Title of Invention	CYLINDER HEAD STRUCTURE OF ENGINE
Abstract	[Designation of Document] Abstract [Abstract] [Problem] The present invention provides the cylinder head structure of an engine in which a lower portion of a head cover is brought into contact with a mating face formed on an upper portion of the cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged with head cover fastening bosses which are integrally formed on the cylinder head, wherein a length of the head cover fastening bolt can be shortened and assembling property is enhanced thus realizing the reduction of weight. [Means for Resolution] On upper portions of a cam shaft holder 68 which is integrally formed with a cylinder head 39 so as to rotatably support a camshaft 63 which constitutes a portion of a valve operating mechanism 57, a head cover fastening boss 96 which has upper end thereof arranged above a mating face 61 is integrally formed such that a space is formed below the head cover fastening boss 96 and the head cover fastening boss 96 projects sideward from the cam shaft holder 68. [Selected Drawing] Fig. 5

Title of Invention

CYLINDER HEAD STRUCTURE OF ENGINE

Abstract

[Designation of Document] Abstract [Abstract] [Problem] The present invention provides the cylinder head structure of an engine in which a lower portion of a head cover is brought into contact with a mating face formed on an upper portion of the cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged with head cover fastening bosses which are integrally formed on the cylinder head, wherein a length of the head cover fastening bolt can be shortened and assembling property is enhanced thus realizing the reduction of weight. [Means for Resolution] On upper portions of a cam shaft holder 68 which is integrally formed with a cylinder head 39 so as to rotatably support a camshaft 63 which constitutes a portion of a valve operating mechanism 57, a head cover fastening boss 96 which has upper end thereof arranged above a mating face 61 is integrally formed such that a space is formed below the head cover fastening boss 96 and the head cover fastening boss 96 projects sideward from the cam shaft holder 68. [Selected Drawing] Fig. 5

Full Text	[Designation of Document] Specification [Title of the Invention] CYLINDER HEAD STRUCTURE OF ENGINE [Technical Field] [0001] The present invention relates to a cylinder head structure of an engine in which a cylinder head which arranges an intake valve and an exhaust valve therein in an openable and closable manner is joined to an upper portion of a cylinder block including a cylinder bore in which a piston is slidably fitted, a lower portion of a head cover which defines a valve operating chamber housing a valve operating mechanism for driving the intake valve and the exhaust valve in an openable and closable manner between the head cover and the cylinder head is brought into contact with a mating face formed on an upper portion of the cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged with head cover fastening bosses which are integrally formed on the cylinder head, and more particularly to the improvement of a cylinder head structure of such an engine. [Background Art] [0002] In patent document 1, there has been known an engine in which a lower portion of the head cover is brought into contact with a mating face which is formed on an upper portion of a cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged with head cover fastening bosses which are integrally formed on the cylinder head. [Patent document 1] JP-A-2007-291979 [Disclosure of the Invention] [Problems that the Invention is to Solve] [0003] However, with respect to the engine disclosed in the above-mentioned patent document 1, the head cover fastening bosses are integrally formed on the cylinder head such that upper surfaces of the head cover fastening bosses become contiguously coplanar with a mating fciCG. In such structure, head cover fastening bolts become extremely long resulting in the increase of weight of the engine and lowering of assembling property of the engine. [0004] The present invention has been made under such circumstances, and it is an object of the present invention to provide the cylinder head structure which can shorten head cover fastening bolts thus enhancing assembling property and realizing the reduction of weight of the engine. [Means for Solving the Problem] [0005] To achieve the above-mentioned objects, the invention described in claim 1 is characterized in that, in a cylinder head structure of an engine in which a cylinder head which arranges an intake valve and an exhaust valve therein in an openable and closable manner is joined to an upper portion of a cylinder block including a cylinder bore in which a piston is slxdably fitted, a lower portion of a head cover which defines a valve operating chamber housing a valve operating mechanism for driving the intake valve and the exhaust valve in an openable and closable manner between the head cover and the cylinder head is brought into contact with a mating face formed on an upper portion of the cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged V7ith head cover fastening bosses which are integrally formed on the cylinder head, on upper portions of cam shaft holders which are integrally formed with the cylinder head so as to rotatably support a camshaft which constitutes a portion of the valve operating mechanism, the head cover fastening bosses which have upper ends thereof arranged above the mating face are integrally formed such that the head cover fastening bosses project sideward from the cam shaft holders so as to form spaces below the head cover fastening bosses. [0006] The invention described in claim 2 is characterized in that, in addition to the constitution of the invention described in claim 1, the upper portion of the cylinder head is constituted of a bottom portion on which the cam shaft holders are formed in a projecting manner and the side wall portion which projects upwardly from an outer periphery of the bottom portion and forms the mating face on an upper end thereof thus forming a box shape which is opened upwardly, and the head cover fastening bosses are arranged at positions spaced-apart inward from the side wall portion. [0007] The invention described in claim 3 is characterized in that, in addition to the constitution of the invention described in claim 1 or claim 2, the cylinder block and the cylinder head are joined together to the crankcase using a plurality of stud bolts which are mounted on the crankcase and a plurality of nuts which are respectively threadediy engaged with the stud bolts, and on upper ends of stud bolt insertion bosses which are integrally formed with the cylinder head such that the plurality of stud bolts are respectively inserted into the stud bolt insertion bosses , and nut engaging surfaces which are arranged on the same plane as the upper ends of the head cover fastening bosses are formed so as to bring the nuts into contact and the engagement with the nut engaging surfaces. [0008] The invention described in claim 4 is characterized in that, in addition to the constitution of the invention described in claim 3, four stud bolt insertion bosses which respectively allow the insertion of four stud bolts therethrough are integrally formed on four corners of the camshaft holders, and two head cover fastening bosses are respectively individually and integrally formed on two stud bolt insertion bosses which are arranged at diagonal positions out of the stud bolt insertion bosses. [00 09 J The invention described in claim 5 is characterized in that, in addition to the constitution of the invention described in claim 4, between the stud bolt which is inserted into at least one specific stud bolt insertion boss out of two stud bolt insertion bosses excluding the stud bolt insertion bosses which are integrally and contiguously formed with the head cover fastening bosses and the cylinder head, an annular oil passage is formed, and a branch passage which is branched from a midst portion of the annular oil passage is formed in the cylinder head so as to guide oil toward an oil passage formed in the head cover. [0010] The invention described in claim 6 is characterized in that, in addition to the constitution of the invention described in any one of claims 1 to 5, threaded holes with which the head cover fastening bolts are threadedly engaged are formed in the head cover fastening bosses in a state that the threaded holes vertically penetrate the head cover fastening bosses. [0011] The invention described in claim 7 is characterized in that, in addition to the constitution of the invention described in claim 6, lower opening ends of the threaded holes are arranged above the mating face of the cylinder head. [0012] The invention described in claim 8 is characterized in that, in addition to the constitution of the invention described in any one of claims 1 to 6 , lower ends of the head cover fastening bosses are arranged above the mating face of the cylinder head. [Advantage of the Invention] [0013] : According to the invention called for in claim 1, the head cover fastening bosses are integrally formed on the upper portion of the cam shaft holder, and the upper ends of the head cover fastening bosses are arranged above the mating face which is formed on the upper portion of the cylinder head so as to be in contact with the lower portion of the head cover by way of the gasket. Due to such constitution, a length of the head cover fastening bolts can be shortened and hence, the cylinder head can be light-weighted and, at the same time, the assembling property of the cylinder head can be enhanced. Further, spaces are formed below the head cover fastening bosses and hence, the cylinder head can be further light-weighted due to the reduction of wall thicknesses of the head cover fastening bosses from below. [0014] Further, according to the invention called for in claim 2, the upper portion of the cylinder head is constituted of the bottom portion on which the cam shaft holders are formed in a projecting manner and the side wall portion which projects upwardly from the outer periphery of the bottom portion thus forming a box shape which is opened upwardly, and the head cover fastening bosses are arranged at positions spaced-apart inward from the side wall portion which forms the mating face on the upper end thereof. Accordingly, the head cover fastening bosses do not become obstacles in forming the mating face thus easing the forming of the mating face. Further, although there exists a possibility that blow-holes are formed in an outer surface of the side wall portion at the time of casting the cylinder head when the side wall portion and the head cover fastening bosses are integrally and contiguously formed, the head cover fastening bosses are arranged at positions spaced-apart inward from the side wall portion and hence, the formation of the blow-holes can be surely prevented thus easing the maintenance of appearance of the cylinder head. Further, due to the structure which prevents the direct connection of the head cover fastening bosses with the side wall portion and the bottom portion, a recessed portion in which lubrication oil stays is hardly formed on the upper portion of the cylinder head thus improving the return of lubrication oil from the cylinder head. [0015] According to the invention called for in claim 3, the cylinder block and the cylinder head are joined together to the crankcase using the plurality of stud bolts and the plurality of nuts, and on the upper ends of the stud bolt insertion bosses which are integrally formed with the cylinder head such that the stud bolts are respectively inserted into the stud bolt insertion bosses, nut engaging surfaces which are arranged on the same plane as upper ends of the head cover fastening bosses are formed. Due to such constitution, forming of the upper ends of the head cover fastening bosses and forming of the nut engaging surfaces can be easily performed. [0016] According to the invention called for in claim 4 , four stud bolt insertion bosses which respectively allow the insertion of four stud bolts therethrough are integrally formed on four corners of camshaft holders. Accordingly, it is possible to make the respective stud bolt insertion bosses function as strength-and-rigidity portions of the cam shaft holders and, further, two head cover fastening bosses are respectively individually and integrally formed on two stud bolt insertion bosses arranged at diagonal positions. Due to such constitution, by contiguously forming the head cover fastening bosses on the stud bolt insertion bosses having high strength and rigidity, it is possible to increase the strength and the rigidity of the head cover fastening bosses . Further, the stud bolt insertion bosses and the head cover fastening bosses are arranged close to each other and hence, a moving distance of a tool for machining upper end surfaces of the stud bolt insertion bosses and the head cover fastening bosses can be decreased thus contributing to shortening of forming time. Further, by contiguously forming the head cover fastening bosses on the stud bolt insertion bosses which are arranged at diagonal positions at four corners of the cam shaft holders, a distance between the two head cover fastening bosses can be set to a large value and hence, the head cover can be fixed to the cylinder head in a stable manner. [0017] According to the invention called for in claim 5, the annular oil passage is formed between the stud bolt which is inserted into the specific stud bolt insertion boss different from the stud bolt insertion bosses on which the head cover fastening bosses are integrally and contiguously formed and the cylinder head, and the branch passage which is branched from the midst portion of the annular oil passage is formed in the cylinder head. Due to such constitution, the head cover fastening bosses and the branch passage can be arranged in a spaced-apart manner from each other thus preventing large-sizing of the cylinder head. [0018] According to the invention called for in claim 6, the threaded holes with which the head cover fastening bolts are engaged are formed in the head cover fastening bosses in a state that the threaded holes vertically penetrates the head cover fastening bosses. Due to such constitution, lower-hole forming and threads forming of the threaded holes can be easily performed and, at the same time, the cut debris can be also easily removed. Further, heights of the head cover fastening bosses pan be set corresponding to the required threaded hole distance and hence, the head cover fastening bosses can be miniaturized thus enhancing the reduction of weight more effectively. [0019] According to the invention called for in claim 7, the lower opening ends of the threaded holes are arranged above the mating face of the cylinder head and hence, the lower opening ends of the threaded holes can be easily observed and a tool can be easily inserted into the lower opening end side of the threaded holes thus easing a burr removing operation. [0020] According to the invention called for in claim 8, the lower ends of the head cover fastening bosses are arranged above the mating face of the cylinder head and hence, the reduction of weight of the head cover fastening bosses can be further enhanced. [Best Mode for Carrying Out the Invention] [0021] Hereinafter, a mode for carrying out the present invention is explained in conjunction with one embodiment of the present invention shown in attached drawings. [0022] Fig. 1 to Fig. 9 are views showing one embodiment of the present, invention, wherein Fig. 1 is a right side view of a motorcycle. Fig. 2 is a vertical cross-sectional side view of a power unit. Fig. 3 is a cross-sectional view taken along a line 3-3 in Fig. 2, Fig. 4 is a cross-sectional view taken along a line 4-4 in Fig. 2, Fig. 5 is a cross-sectional view taken along a line 5-5 in Fig. 4, Fig. 6 is a cross-sectional view taken along a line 6-6 in Fig. 4, Fig. 7 is a cross-sectional view taken along a line 7-7 in Fig. 4, Fig. 8 is a cross-sectional view taken along a line 8-8 in Fig. 2, and Fig. 9 is a cross-sectional view taken along a line 9-9 in Fig. 8. [0023] First of all, in Fig. 1, a vehicle body frame F of the motorcycle includes a head pipe 16 which steerably supports a front folk 15 which pivotally supports a front wheel WF on a lower end portion thereof, a main frame 17 having, on a rear portion thereof , a downward extending portion 17a which extends rearward from the head pipe 16, is curved and then extends downward, a pair of left and right downward frames 18... which is inclined rearward and downward from the head pipe 16 and is arranged below the main frame 17, a pair of left and right sheet rails 19...which extends rearward from an upper portion of the downward extending portion 17a of the main frame 17, and a pair of left and right connection frames 20...which connects a lower' portion of the downward extending portion 17a and intermediate portions of both sheet rails 19.... [0024] A steering handle 21 is connected to an upper end of the front folk 15, a rider' s-sheet 22 is mounted on the sheet rails 19..., and a fuel tank 23 which is arranged in front of the rider' s-sheet 22 and strides over the main frame 17 is mounted on the main frame 17. [0025] In a portion surrounded by the main frame 17 and the down frames 18..., a power unit P is arranged. A first bracket 24 is mounted on lower end portions of both down frames 18..., second and third brackets 25, 26 are arranged at two pprtions of the ■I downward extending portion 17a of the main frame 17 which are arranged in a vertically-spaced-apart manner, and the power unit P is mounted on the first to third brackets 24, 25, 26. -I [0026] ; A pivot frame 27 is fixedly mounted on the downward extending portion 17a of the main frame 17 between the second and third brackets 25, 26, front end portions of swing arms 28...which pivot ally support a rear wheel WR on a rear end portions thereof are tiltably supported on the pivot plate 27 by way of a support shaft 29, and a rear cushion unit 30 is arranged between the sheet rails 19...and the swing arms 28.... [0027] Between a counter shaft 5 3 provided to the power unit P and an axle 32 of the rear wheel WR, a chain power transmission means 36 which is constituted of a drive sprocket wheel 33 which is mounted on the counter shaft 53, a driven sprocket wheel 34 which is fixed to the axle 32, and an endless chain 35 which is extended between and wound around the drive sprocket wheel 33 and the driven sprocket wheel 34 is arranged. [0028] In Fig. 2, the power unit P is constituted of a single-cylinder engine E having a crankcase 37 which is mounted on the first to third brackets 24 , 25 , 26 , and a constant messing gear transmission M which is housed in the inside of the crankcase 37 such that power of the engine E is transmitted to the rear wheel WR in a speed-changing and reducing manner. [0029] The engine E includes the crankcase 37, a cylinder block 38 which is joined to an upper portion of the crankcase 37, a cylinder head 39 which is joined to an upper end of the cylinder block 38, and a head cover 40 which is joined to the cylinder head 39. [0030] An upstream ends of intake pipes 41... which are connected to a rear side surface of the cylinder head 39 are connected to an air cleaner 43 by way of a carburetor 42, and the air cleaner 43 is fixedly arranged above a rear portion of the power unit P. Further, an exhaust pipe 44 which is connected to a front side surface of the cylinder head 39 extends rearward after passing below the power unit P and is connected to an exhaust muffler 45 which is arranged on a right side of the rear wheel WR. [0031] The crankcase 37 is formed by joining a pair of left and right case half bodies 46, 47 to each other, and a crankshaft 48 having an axis along the widthwise direction of the motorcycle is rotatably supported by both case half bodies 46, 47. [0032] The cylinder block 38 is joined to'the crankcase 37 in a state that the cylinder block 38 is inclined frontward and upward in the advancing direction of the motorcycle, and a cylinder bore 50 which allows slidable fitting of a piston 49 therein is formed in the cylinder block 38, and the piston 49 is connected to a crankpin 48a which the crankshaft 48 includes by way of a connecting rod 51. ,1 [0033] ' The above-mentioned constant messing gear transmission M is formed by arranging a gear train of a plurality of gear shift positions which can be selectively established between a main shaft 52 to which power is transmitted from the crankshaft 48 and a countershaft 53. Here, the main shaft 52 and the counter shaft 53 are rotatably supported by the crankcase 3 7 in a state that the main shaft 52 and the countershaft 53 have axes arranged parallel to the crankshaft 48, and the drive sprocket wheel 33 is fixedly mounted on an end portion of the countershaft 53 which projects from the case half bodies 46 of the crankcase 36. [0034] An intake valve 55 and an exhaust valve 56 are arranged in an openable and closable manner such that the intake valve 55 and the exhaust valve 56 are biased in the valve-closing direction, and a v^lve operation chamber 58 which houses a valve operating mechanism 57 which is driven so as to open or close the intake valve 55 and the exhaust valve 56 is formed between the cylinder head 39 and the head cover.40. [0035] To explain this embodiment also in conjunction with Fig. 3, an ignition plug 60 is mounted on the cylinder head 39 in a state that a distal end portion of the ignition plug 60 faces a combustion chamber 59 which is formed between the cylinder block 38 and the cylinder head 39. Here, a top portion of the piston 49 faces the combustion chamber 59. [0036] Further, an upper portion of the cylinder head 39 is constituted of a bottom portion 39a which faces upwardly and a side wall portion 39b which projects upwardly from an outer periphery of the bottom portion 39a and is contiguously formed with the bottom portion 39a in an endless manner thus forming a box shape which opens upwardly. A lower portion of the head cover 40 which is formed in a box shape opening downwardly is i brought into contact with a mating face 61 which is formed on an upper surface of the side wall portion 39b by way of a gasket 62. [0037] The valve operating chamber 5 8 is formed between the upper portion of the cylinder head 39 and the head cover 40. The valve operating mechanism 57 housed in the valve operating chamber 58 includes a camshaft 53 which has an axis parallel to the crankshaft 48 and is arranged between the intake valve 55 and the exhaust valve 56, an intake-side rocker arm 66 which is arranged between an intake-side cam 64 mounted on the camshaft 63 and the intake valve 55, and an exhaust-side rocker arm 67 which is arranged between an exhaust-side cam 65 mounted on the camshaft 6 3 and the exhaust valve 5 5. [0038] To explain this embodiment also in conjunction with Fig. 4 to Fig. 6, the camshaft 63 is rotatably supported on the cylinder head 39 as follows. A pair of camshaft holders 68, 69 which projects upward from the bottom portion 39a of the upper portion of the cylinder head 39 is integrally formed with the cylinder head 39 in a spaced-apart manner in the axial direction of the camshaft 63. A ball bearing 70 is interposed between an inner peripheral surface of a support hole 72 formed in one camshaft holders 68 and an outer peripheral surface of one end portion of the camshaft 63, and a ball bearing 71 is interposed between an inner peripheral surface of the support hole 73 formed in another camshaft holder 69 coaxially with the support hole 72 and the camshaft 63. [0039] The support hole 7 3 formed in another camshaft holder 69 has a diameter larger than a diameter of the support hole 72 formed in one camshaft holder. The camshaft 63 which mounts the ball bearings 70 , 71 on the outer peripheral surface thereof is assembled in the cylinder,head 39 such that the camshaft 63 is inserted into the support holes 72, 73 formed in both camshaft holders 68, 69 from another camshaft holder 69 side. To another camshaft holder 69, an engagement plate 74 which is engaged with or is brought into contact with an outer race of the ball bearing 71 which is interposed between the camshaft 63 and the camshaft holder 69 .thus preventing removal of the camshaft 63 from both camshaft holders 68, 69 using a bolt 75. [0040]. Here, an axis of the support holes 72, 73 and the camshaft 63 are placed on a plane along the mating face 61. To enable assembling of the camshaft 63 in the cylinder head 39, a semicircular notched portion 76 which allows the insertion of the camshaft 63 into the support holes 72, 73 is formed on a portion of the side wall portion 39b which faces another end of the camshaft 63 above the cylinder head 39. and a lid portion 62a for closing the notched portion 76 is integrally formed with the gasket 62. [0041] Rotational power from the crankshaft 48 is transmitted to the camshaft 63 at a speed reduction ratio of 1/2 by a timing power transmission means 78. The timing power transmission means 78 is constituted of a drive sprocket wheel (not shown in the drawing) which is mounted on the crankshaft 48, a driven sprocket wheel 80 which is fixed to another end portion of the camshaft 63, and an endless timing chain 81 which is extended between and wound around the drive sprocket wheel and the driven sprocket wheel 80. A chain running passage 8 2 which allows running of the timing chain 81 therethrough is formed in the cylinder block 38 and the cylinder head 39. [0042] The intake-side rocker arm 66 is rockably supported on an intake-side rocker shaft 83 provided between both camshaft holders 68, 69, a roller. 87 which is brought into ipolling contact with the intake-side cam 64 is pivotally supported on one end portion of the intake-side rocker arm 66, and a tappet screw 88 which is brought into contact with an upper end of the intake valve 55 is threadedly engaged with another end portion of the intake-side rocker arm 66 such that an advancing/retracting position of the tappet screw 88 can be adjusted. Further, the exhaust-side rocker arm 67 is rockably supported on an exhaust-side rocker shaft 84 provided between both camshaft holders 68, 69, a roller 89 which is brought into rolling contact with the exhaust-side cam 65 is pivotally supported on one end portion of the exhaust-side rocker arm 67, and a tappet screw 90 which is brought into contact with an upper end of the exhaust valve 56 is threadedly engaged with another end portion of the exhaust-side rocker arm 67 such that an advancing/retracting position of the tappet screw 90 can be adjusted. [0043] In Fig. 7, a bottomed support hole 91 is formed in one camshaft holder 68, and a support hole 92 which is a through hole coaxial with the support hole 91 is formed in another camshaft holder 69. The intake-side rocker shaft 83 is fitted into both support holes 91, 92 from the support hole 92 side, and for determining an axial-direction position of the intake-side rocker shaft 83, a screw member 85 which has a distal end portion thereof engaged with an outer periphery of the intake-side rocker shaft 83 is threadedly engaged with the camshaft holder 68. [0044] , The exhaust-side rocker shaft 84 is, in the same manner as the intake-side rocker shaft 83, fitted into the camshaft holders 68, 69, and a screw member 86 for determining an axial-direction position of the exhaust-side rocker shaft 84 (see Fig. 4) is fitted into the camshaft holder 69. [0045] Here, a lower portion of the head cover 40 is brought into contact with the mating face 61 which is formed on the upper end of the side wall .portion 39b of the cylinder head 39 by way of the gasket 62 . In such constitution , by threadedly engaging two head cover fastening bolts 95, 95 which are inserted into the head cover 40 with two head cover fastening bosses 96, 97 which are integrally formed with the cylinder head 39, the head cover 40 is joined to the cylinder head 39. [0046] The head cover fastening bosses 96, 97 are integrally formed on upper portions of the camshaft holders 68, 69 which are integrally formed with the cylinder head 39 so as to rotatably support the camshaft 63 which constitutes a portion of the valve operating mechanism 57. Here, upper ends of the head cover fastening bosses 96,97 are arranged above the mating face 61. These head cover fastening bosses 96, 97 are integrally formed on upper portions of the camshaft holders 68, 6 9 such that spaces are formed below the head cover fastening bosses 96, 97 and the head cover fastening bosses 96, 97 project sideward from the camshaft holders 68, 69. Further, the spaces below the head cover fastening bosses 96, 9 7 can be formed using a sand core at the time of forming the cylinder head 39 by casting. [0047] Here, the cylinder block 38 and the cylinder head 39 are joined together to the crankcase 37 using a plurality of, for example, four stud bolts 98, 99. 100, 101 which are mounted on the crankcase 37 and a plurality of, for example, four nuts 102... with which these stud bolts 98 to 101 are threadedly engaged; Four stud bolt insertion bosses 103, 104, 105, 106 which allow the insertion of the respective stud bolts 98 to 101 therethrough are integrally formed on the cylinder head 39. [0048] Four stud bolt insertion bosses 103 to 106 which respectively allow the insertion of the respective stud bolts 98 to 101 therethrough are integrally formed on four corners of both camshaft holders 68, 69. On two stud bolt insertion bosses 103, 105 which are arranged at diagonal positions out of these stud bolt insertion bosses 103 to 106, two head cover fastening bosses 96, 97 are respectively, individually, integrally and contiguously formed. Further, the head cover fastening bosses 96 , 97 are arranged at a position spaced apart inward from the side wall portion 39b of the upper portion of the cylinder head 39. [0049] On upper ends of the stud bolt insertion bosses 103 to 106, nut engaging surfaces 103a, 104a, 105a, 106a which are arranged on the same plane as upper ends of the head cover fastening bosses 96, 97 are formed. The nuts 102... which are threadedly engaged with the stud bolts 98 to 101 are brought into contact with or engaged with the nut engaging surfaces 103a to 106a by way of washers 107.... [0050] The head cover fastening bolts 95... are inserted into the head cover 4 0 with annular sealing members 10 8... interposed between the head cover fastening bolts 95... and the head cover 40 . The head cover fastening bolts 95... include flange portions 95a... which are brought into contact with upper ends of the head cover fastening bosses 96, 97, and screw shaft portions 95b... which project from the flange portions 95a coaxially. The screw shaft portions 9 5... are threadedly engaged with threaded holes 109, 110 which are formed in the head cover fastening bosses 96, 97. [0051] Here, lower ends of the head cover fastening bosses 96, 97 are arranged above the mating face 61 of the cylinder head 39, and the threaded holes 109, 110 vertically penetrate the head cover fastening bosses 96 , 97 such that the threaded holes 109, 110 have lower opening ends thereof arranged above the mating face 61 of the cylinder head 39. [0052] As shown in Fig. 2 , Fig. 3 , Fig. 8 and Fig . 9 , an oil passage 111 which extends in the direction orthogonal to the axis of the camshaft 63 is formed in the head cover 40. As shown in Fig. 2 and Fig. 8, two oil jets 112, 113 which are communicated with the oil passage 111 are formed in the head cover 40 such that these oil jets 112 , 113 blow off oil to the valve operating mechanism 57 side. [0053] Here, between the stud bolt 99 which is inserted into at least one specific stud bolt insertion boss out of two stud bolt insertion bosses excluding the stud bolt insertion bosses 103, 105 which are integrally and contiguously formed with the head cover fastening bosses 96, 97 out of four stud bolt insertion bosses 103 to 106 (in this embodiment, one specific stud bolt insertion boss 104) and the cylinder head 39, as shown in Fig. 5, an annular oil passage 114 is formed. Also between the stud bolt 9 9 and the cylinder block 3 8, an annular oil passage 115 which is communicated with the annular oil passage 114 is formed, and the annular oil passage 115 is connected with an oil supply source not shown in the drawing through an oil passage 116 formed in the crankcase 37. [0054] A branch passage 117 which is branched from a midst portion of the annular oil passage 114 is formed in the cylinder head 39 and extends in an oblique upward direction so as to guide oil to the oil passage 111 side of the head cover side 40. A lower end of a communication passage 118 which is communicated with the oil passage 111 and extends downward and an upper end of the branch passage 117 are connected with each other by way of a sleeve 119 sandwiched between the cylinder head 39 and a head cover 40. [0055] ; Next, the manner of operation of this embodiment is explained. On the upper portions of the cam shaft holders 68, 69 which are integrally formed on the cylinder head 39 so as to rotatably support the camshaft 63 which constitutes a portion of the valve operating mechanism 57, the head cover fastening bosses 96, 97 whose upper ends are arranged above the mating face 61 of the upper end of the cylinder head 39 are integrally formed such that.the head cover fastening bosses 96, 97 project sideward from the cam shaft holders 68, 69. Accordingly, a length of the head cover fastening bolts 95... can be shortened and hence, the cylinder head 39 can be light-weighted and, at the same time, the assembling property of the cylinder head 39 can be enhanced. Further, the spaces are formed below the head cover fastening bosses 96, 97 and hence, the cylinder head 39 can be light-weighted due to the reduction of wall thicknesses of the head cover fastening bosses 96 , 97 from below. Still further, by forming the spaces using the sand cores at the time of forming the cylinder head 3 9 by casting, the increase of the number of cores becomes unnecessary and hence, it is possible to form the spaces below the head cover fastening bosses 96, 97 while suppressing the increase of a cost. [0056} Further, the upper portion of the cylinder head 39 is constituted of the bottom portion 39a on which the head cover fastening bosses 96, 97 are formed in a projecting manner and the side wall portion 39b which projects upwardly from the outer periphery of the bottom portion 39a thus forming a box shape which is opened upward, and the head cover fastening bosses 96, 97 are arranged at positions spaced-apart inward from the side wail portion 39b which forms the mating face 61 on the upper end thereof. Accordingly, the head cover fastening bosses 96, 97 do not become obstacles in forming the mating face 61 thus easing the forming of the mating face 61. Further, although there exists a possibility that blow-holes are formed in an outer surface of the side wall portion 39b at the time of casting the cylinder head 39 when the side wall portion 39b and the head cover fastening bosses 96, 97 are integrally and contiguously formed, the head cover fastening bosses 96, 97 are arranged at positions spaced-apart inward from the side wall portion 39b and hence, the formation of the blow-holes can be surely prevented thus easing the maintenance of appearance of the cylinder head 3 9. Further, due to the structure which prevents the direct connection of the head cover fastening bosses 96, 97 with the side wall portion 39b and the bottom portion 39a, a recessed portion in which lubrication oil stays is hardly formed in the upper portion of the cylinder head 39 thus improving the return of lubrication oil from the cylinder head 39. [0057] Further, the cylinder block 38 and the cylinder head 39 are joined together to the crankcase 3 7 using the plurality of, for example, four stud bolts 98, 99, 100, 101 and the plurality of nuts 102..., and on the upper ends of the stud bolt insertion bosses 103, 104, 105, 106 which are integrally formed with the cylinder head 39 such that the stud bolts 98 to 101 are respectively inserted into the stud bolt insertion bosses 103, 104, 105, 106, nut engaging surfaces 103a, 104a, 105a, 106a which are arranged on the same plane as upper ends of the head cover fastening bosses 96, 97 are formed. Accordingly, forming of the upper ends of the head cover fastening bosses 96, 97 and forming of the nut engaging surfaces 103a to lQ6a can be easily performed. [0058] Further, four stud bolt insertion bosses 103 to 106 which respectively allow the insertion of the respective four stud bolts 98 to 101 therethrough are integrally formed on four corners of both camshaft holder 68, 69. Accordingly, it is possible to make the stud bolt insertion bosses 103 to 106 functioh as strength-and-rigidity portions of the cam shaft holders 68, 69. Two head cover fastening bosses 96, 97 are respectively individually and integrally formed on two stud bolt insertion bosses 103, 105 arranged at two diagonal positions and hence, by contiguously forming the head cover fastening bosses 9.6, 97 on the stud bolt insertion bosses 103, 105 having high strength and rigidity, it is possible to increase the strength and the rigidity of the head cover fastening bosses 96, 97. Further, the stud bolt insertion bosses l03, 105 and the head cover fastening bosses 96, 97 can be arranged close to each other and hence, a moving distance of a tool for machining upper end surfaces of the stud bolt insertion bosses 103, 105 and the head cover fastening bosses 96, 97 can be decreased thus contributing to shortening of forming time. [0059] Further, by contiguously forming the head cover fastening bosses 96, 97 on the stud bolt insertion bosses 103, 105 which are arranged at diagonal positions at four corners of the cam shaft holders 68, 69, a distance between two head cover fastening bosses 96, 97 can be set to a large value and hence, the head cover 40 can be fixed to the cylinder head 39 in a stable manner. [0060] Further, the annular oil passage 114 is formed between the stud bolt 99 which is inserted into the specific stud bolt insertion boss 104 different from the stud bolt insertion bosses 103, 105 on which the head cover fastening bosses 96, 97 are integrally and contiguously formed and the cylinder head 39 , and the branch passage 117 which is branched from the midst portion of the annular oil passage 114 and is communicated with the oil passage 111 formed in the head cover 40 is formed in the cylinder head 39 . Due to such constitution, the head cover fastening bosses 96, 97 and the branch passage 117 can be arranged in a spaced-apart manner from each other thus preventing large-sizing of the cylinder head 3 9. [0061] : Further, the lower ends of the head cover fastening bosses 96, 97 are arranged above the mating face 61 of the cylinder head 39 and hence, the reduction of weight of the head cover fastening bosses 96, 97 can be enhanced. [0062] Further, the threaded holes 109, 110 with which the head cover fastening bolts 9 5... are threadedly engaged are formed in the head cover fastening bosses 96, 97 in a state that the threaded holes 109, 110 vertically penetrates the head cover fastening bosses 96, 97. Accordingly, lower-hole forming and threads forming of the threaded holes 109, 110 can be easily performed and, at the same time, the cut debris can be also easily removed. Further, heights of the head cover fastening bosses 96, 97 can be set corresponding to the required threaded hole distance and hence, the head cover fastening bosses 96, 97 can be miniaturized thus enhancing the reduction of weight more effectively. [0063] 1 Further, the lower opening ends of the threaded holes 109, 110 are arranged above the mating face 61 of the cylinder head 39 and hence, the lower opening ends of the threaded holes 109 , 110 can be easily observed and a tool can be easily inserted into the lower opening end side of the threaded holes 109, 110 thus easing a burr removing operation. Although the embodiment of the present invention has been explained heretofore, the present invention is not limited to the above-mentioned embodiment and various design changes can be made without departing from the gist of the present invention described in Claims. [Brief Description of the Drawings] [00653 [Fig. 1] A right side view of a motorcycle. [Fig. 2] A longitudinal cross-sectional side view of a power unit. [Fig. 3] A cross-sectional view taken along a line 3-3 in Fig. 2. [Fig. 4] A cross-sectional view taken along a line 4-4 in Fig. 2. [Fig. 5;] A crossTsectional view taken along a line 5-5 in Fig. 4. [Fig. 6] A cross-sectional view taken along a line 6-6 in Fig. 4 - '. [Fig. 7] A cross-sectional view taken along a line 7-7 in Fig 4 . [Fig. 8] A cross-sectional view taken along a line 8-8 in Fig 2. [Fig. 9] A cross-sectional view taken along a line 9-9 in Fig 8. [Description of Reference Numerals and Signs] [0066] 37: crankcase 38: cylinder block 39: cylinder head 39a: bottom portion 39b: side wall portion 40: head cover 49: piston 50: cylinder bore 55: intake valve 56: exhaust valve 57: valve operating mechanism 58: valve operating chamber 61: mating face 62: gasket 63: cam shaft 68, 69: cam shaft holder 95: head cover fastening bolt 96, 97: head cover fastening boss 98, 99, 100, 101: stud bolt 102: nut 103, 104, 105, 106: Stud bolt insertion boss 103a, 104a, 105a, 106a: nut engaging surface 109, 110: threaded hole 111: oil passage 114: annular oil passage 117: branch passage E: engine [Designation of Document] Claims [Claim 1] A cylinder head structure of an engine in which a cylinder head (39) which arranges an intake valve (55) and an exhaust valve (56) therein in an openable and closable manner is joined to an upper portion of a cylinder block (38) including a cylinder bore (50) in which a piston (49) is slidably fitted, a lower portion of a head cover (40) which defines a valve operating chamber (58) housing a valve operating mechanism ( 57 ) for driving the intake valve (55) and the exhaust valve (56) in an openable and closable manner between the head cover (40) and the cylinder head (39) is brought into contact with a mating face (61) formed on an upper portion of the cylinder head (39) by way of a gasket (62), and head cover fastening bolts (95) which aire inserted into the head cover (40) are threadedly engaged; with head cover fastening bosses (96, 97) which are integrally formed on the cylinder head (39), wherein on upper portions of cam shaft holders (68, 69) which are integrally formed with the cylinder head (39) so as to rotatably support a camshaft (63) which constitutes a portion of the valve operating mechanism ( 57 ) , the head cover fastening bosses (96, 97) which have upper ends thereof arranged above the mating face (61) are integrally formed such that the head cover fastening bosses (96, 97) project sideward from the cam shaft holders (68, 69) so as to form spaces below the head cover fastening bosses (96, 97). [Claim 2] A cylinder head structure of an engine according to claim 1, wherein the upper portion of the cylinder head (39) is constituted of a bottom portion (39a) on which the cam shaft holders (68, 69 ) are formed in a projecting manner and the side wall portion (39b) which projects upwardly from an outer periphery of the bottom portion (39a) and forms the mating face (61) on an upper end thereof thus forming a box shape which is opened upwardly, and the head cover fastening bosses (96, 97) are arranged at positions spaced-apart inward from the side wall portion (39b). [Claim 3] A cylinder head structure of an engine according to claim 1 or claim 2, wherein the cylinder block (38) and the cylinder head (39) are joined together to the cxankcase (37) using a plurality of stud bolts (98, 99, 100, 101) which are mounted on the crankcase (37) and a plurality of nuts (102) which are respectively threadedly engaged with the stud bolts ( 98 to 101) , and on upper ends of stud bolt insertion bosses (103, 104, 105, 106) which are integrally formed with the cylinder head (39) such that the plurality of stud bolts (98 to 101) is respectively inserted into the stud bolt insertion bosses (103 to 106), nut engaging surfaces (103a, 104a, 105a, 106a) which are arranged on the same plane as the upper ends of the head cover fastening bosses (96, 97) are formed so as to bring the nuts (102) into contact and engagement with the nut engaging surfaces (103a, 104a, 105a, 106a). [Claim 4] A cylinder head structure of an engine according to claim 3, wherein four stud bolt insertion bosses (103 to 106) which respectively allow the insertion of said four stud bolts (98 to 101) therethrough are integrally formed on four corners of the camshaft holders ( 68 , 69 ) , and said two head cover fastening bosses (96, 97) are respectively individually and integrally formed on said two stud bolt insertion bosses (103, 105) which are arranged at diagonal positions out of the stud bolt insertion bosses (103 to 106). [Claim 5] A' cylinder head structure of an engine according to claim 4, wherein between the stud bolt (99) which is inserted into at least one specific stud bolt insertion boss (104) out of two stud bolt insertion bosses (104, 106) excluding the stud bolt insertion bosses (103, 105) which are integrally and contiguously formed with the head cover fastening bosses (96, 97) and the cylinder head (39), an annular oil passage (114) is formed, and a branch passage (117) which is branched from a midst portion of the annular oil passage (114) is formed in the cylinder head (39) so as to guide oil toward an oil passage (111) formed in the head cover (40). [Claim 6] A cylinder head structure of a.n engine according to any¬one of claims 1 to 5, wherein threaded holes (109, 110) with which the head cover fastening bolts (95) are 'threadedly engaged are formed in the head cover fastening bosses (96, 97 ) in a state that the threaded holes (109, 110) vertically penetrate the head cover fastening bosses (95, 97). [Claim 7] A cylinder head structure of an engine according to claim 6, wherein lower opening ends of the threaded holes (109, 110) are arranged above the mating face (61) of the cylinder head (39). [Claim 8] A cylinder head structure of an engine according to any one of claims 1 to 6, wherein lower ends of the head cover fastening bosses (96, 97) are arranged above the mating face (61) of the cylinder head (39).

Full Text

[Designation of Document] Specification
[Title of the Invention] CYLINDER HEAD STRUCTURE OF ENGINE
[Technical Field]
[0001]
The present invention relates to a cylinder head structure of an engine in which a cylinder head which arranges an intake valve and an exhaust valve therein in an openable and closable manner is joined to an upper portion of a cylinder block including a cylinder bore in which a piston is slidably fitted, a lower portion of a head cover which defines a valve operating chamber housing a valve operating mechanism for driving the intake valve and the exhaust valve in an openable and closable manner between the head cover and the cylinder head is brought into contact with a mating face formed on an upper portion of the cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged with head cover fastening bosses which are integrally formed on the cylinder head, and more particularly to the improvement of a cylinder head structure of such an engine. [Background Art] [0002]
In patent document 1, there has been known an engine in which a lower portion of the head cover is brought into contact with a mating face which is formed on an upper portion of a

cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged with head cover fastening bosses which are integrally formed on the cylinder head.
[Patent document 1] JP-A-2007-291979 [Disclosure of the Invention] [Problems that the Invention is to Solve] [0003]
However, with respect to the engine disclosed in the above-mentioned patent document 1, the head cover fastening bosses are integrally formed on the cylinder head such that upper surfaces of the head cover fastening bosses become contiguously coplanar with a mating fciCG. In such structure, head cover fastening bolts become extremely long resulting in the increase of weight of the engine and lowering of assembling property of the engine. [0004]
The present invention has been made under such circumstances, and it is an object of the present invention to provide the cylinder head structure which can shorten head cover fastening bolts thus enhancing assembling property and realizing the reduction of weight of the engine. [Means for Solving the Problem] [0005] To achieve the above-mentioned objects, the invention

described in claim 1 is characterized in that, in a cylinder head structure of an engine in which a cylinder head which arranges an intake valve and an exhaust valve therein in an openable and closable manner is joined to an upper portion of a cylinder block including a cylinder bore in which a piston is slxdably fitted, a lower portion of a head cover which defines a valve operating chamber housing a valve operating mechanism for driving the intake valve and the exhaust valve in an openable and closable manner between the head cover and the cylinder head is brought into contact with a mating face formed on an upper portion of the cylinder head by way of a gasket, and head cover fastening bolts which are inserted into the head cover are threadedly engaged V7ith head cover fastening bosses which are integrally formed on the cylinder head,
on upper portions of cam shaft holders which are integrally formed with the cylinder head so as to rotatably support a camshaft which constitutes a portion of the valve operating mechanism, the head cover fastening bosses which have upper ends thereof arranged above the mating face are integrally formed such that the head cover fastening bosses project sideward from the cam shaft holders so as to form spaces below the head cover fastening bosses. [0006]
The invention described in claim 2 is characterized in that, in addition to the constitution of the invention

described in claim 1, the upper portion of the cylinder head is constituted of a bottom portion on which the cam shaft holders are formed in a projecting manner and the side wall portion which projects upwardly from an outer periphery of the bottom portion and forms the mating face on an upper end thereof thus forming a box shape which is opened upwardly, and the head cover fastening bosses are arranged at positions spaced-apart inward from the side wall portion. [0007]
The invention described in claim 3 is characterized in that, in addition to the constitution of the invention described in claim 1 or claim 2, the cylinder block and the cylinder head are joined together to the crankcase using a plurality of stud bolts which are mounted on the crankcase and a plurality of nuts which are respectively threadediy engaged with the stud bolts, and on upper ends of stud bolt insertion bosses which are integrally formed with the cylinder head such that the plurality of stud bolts are respectively inserted into the stud bolt insertion bosses , and nut engaging surfaces which are arranged on the same plane as the upper ends of the head cover fastening bosses are formed so as to bring the nuts into contact and the engagement with the nut engaging surfaces. [0008]
The invention described in claim 4 is characterized in that, in addition to the constitution of the invention

described in claim 3, four stud bolt insertion bosses which respectively allow the insertion of four stud bolts therethrough are integrally formed on four corners of the camshaft holders, and two head cover fastening bosses are respectively individually and integrally formed on two stud bolt insertion bosses which are arranged at diagonal positions out of the stud bolt insertion bosses. [00 09 J
The invention described in claim 5 is characterized in that, in addition to the constitution of the invention described in claim 4, between the stud bolt which is inserted into at least one specific stud bolt insertion boss out of two stud bolt insertion bosses excluding the stud bolt insertion bosses which are integrally and contiguously formed with the head cover fastening bosses and the cylinder head, an annular oil passage is formed, and a branch passage which is branched from a midst portion of the annular oil passage is formed in the cylinder head so as to guide oil toward an oil passage formed in the head cover. [0010]
The invention described in claim 6 is characterized in that, in addition to the constitution of the invention described in any one of claims 1 to 5, threaded holes with which the head cover fastening bolts are threadedly engaged are formed in the head cover fastening bosses in a state that the

threaded holes vertically penetrate the head cover fastening
bosses.
[0011]
The invention described in claim 7 is characterized in that, in addition to the constitution of the invention described in claim 6, lower opening ends of the threaded holes are arranged above the mating face of the cylinder head. [0012]
The invention described in claim 8 is characterized in that, in addition to the constitution of the invention described in any one of claims 1 to 6 , lower ends of the head cover fastening bosses are arranged above the mating face of the cylinder head. [Advantage of the Invention] [0013] :
According to the invention called for in claim 1, the head cover fastening bosses are integrally formed on the upper portion of the cam shaft holder, and the upper ends of the head cover fastening bosses are arranged above the mating face which is formed on the upper portion of the cylinder head so as to be in contact with the lower portion of the head cover by way of the gasket. Due to such constitution, a length of the head cover fastening bolts can be shortened and hence, the cylinder head can be light-weighted and, at the same time, the assembling property of the cylinder head can be enhanced. Further, spaces

are formed below the head cover fastening bosses and hence, the cylinder head can be further light-weighted due to the reduction of wall thicknesses of the head cover fastening bosses from below. [0014]
Further, according to the invention called for in claim 2, the upper portion of the cylinder head is constituted of the bottom portion on which the cam shaft holders are formed in a projecting manner and the side wall portion which projects upwardly from the outer periphery of the bottom portion thus forming a box shape which is opened upwardly, and the head cover fastening bosses are arranged at positions spaced-apart inward from the side wall portion which forms the mating face on the upper end thereof. Accordingly, the head cover fastening bosses do not become obstacles in forming the mating face thus easing the forming of the mating face. Further, although there exists a possibility that blow-holes are formed in an outer surface of the side wall portion at the time of casting the cylinder head when the side wall portion and the head cover fastening bosses are integrally and contiguously formed, the head cover fastening bosses are arranged at positions spaced-apart inward from the side wall portion and hence, the formation of the blow-holes can be surely prevented thus easing the maintenance of appearance of the cylinder head. Further, due to the structure which prevents the direct connection of

the head cover fastening bosses with the side wall portion and the bottom portion, a recessed portion in which lubrication oil stays is hardly formed on the upper portion of the cylinder head thus improving the return of lubrication oil from the cylinder head. [0015]
According to the invention called for in claim 3, the cylinder block and the cylinder head are joined together to the crankcase using the plurality of stud bolts and the plurality of nuts, and on the upper ends of the stud bolt insertion bosses which are integrally formed with the cylinder head such that the stud bolts are respectively inserted into the stud bolt insertion bosses, nut engaging surfaces which are arranged on the same plane as upper ends of the head cover fastening bosses are formed. Due to such constitution, forming of the upper ends of the head cover fastening bosses and forming of the nut engaging surfaces can be easily performed. [0016]
According to the invention called for in claim 4 , four stud bolt insertion bosses which respectively allow the insertion of four stud bolts therethrough are integrally formed on four corners of camshaft holders. Accordingly, it is possible to make the respective stud bolt insertion bosses function as strength-and-rigidity portions of the cam shaft

holders and, further, two head cover fastening bosses are respectively individually and integrally formed on two stud bolt insertion bosses arranged at diagonal positions. Due to such constitution, by contiguously forming the head cover fastening bosses on the stud bolt insertion bosses having high strength and rigidity, it is possible to increase the strength and the rigidity of the head cover fastening bosses . Further, the stud bolt insertion bosses and the head cover fastening bosses are arranged close to each other and hence, a moving distance of a tool for machining upper end surfaces of the stud bolt insertion bosses and the head cover fastening bosses can be decreased thus contributing to shortening of forming time. Further, by contiguously forming the head cover fastening bosses on the stud bolt insertion bosses which are arranged at diagonal positions at four corners of the cam shaft holders, a distance between the two head cover fastening bosses can be set to a large value and hence, the head cover can be fixed to the cylinder head in a stable manner. [0017]
According to the invention called for in claim 5, the annular oil passage is formed between the stud bolt which is inserted into the specific stud bolt insertion boss different from the stud bolt insertion bosses on which the head cover fastening bosses are integrally and contiguously formed and the cylinder head, and the branch passage which is branched

from the midst portion of the annular oil passage is formed in the cylinder head. Due to such constitution, the head cover fastening bosses and the branch passage can be arranged in a spaced-apart manner from each other thus preventing large-sizing of the cylinder head. [0018]
According to the invention called for in claim 6, the threaded holes with which the head cover fastening bolts are engaged are formed in the head cover fastening bosses in a state that the threaded holes vertically penetrates the head cover fastening bosses. Due to such constitution, lower-hole forming and threads forming of the threaded holes can be easily performed and, at the same time, the cut debris can be also easily removed. Further, heights of the head cover fastening bosses pan be set corresponding to the required threaded hole distance and hence, the head cover fastening bosses can be miniaturized thus enhancing the reduction of weight more effectively. [0019]
According to the invention called for in claim 7, the lower opening ends of the threaded holes are arranged above the mating face of the cylinder head and hence, the lower opening ends of the threaded holes can be easily observed and a tool can be easily inserted into the lower opening end side of the threaded holes thus easing a burr removing operation.

[0020]
According to the invention called for in claim 8, the lower ends of the head cover fastening bosses are arranged above the mating face of the cylinder head and hence, the reduction of weight of the head cover fastening bosses can be further enhanced.
[Best Mode for Carrying Out the Invention] [0021]
Hereinafter, a mode for carrying out the present invention is explained in conjunction with one embodiment of the present invention shown in attached drawings. [0022]
Fig. 1 to Fig. 9 are views showing one embodiment of the present, invention, wherein Fig. 1 is a right side view of a motorcycle. Fig. 2 is a vertical cross-sectional side view of a power unit. Fig. 3 is a cross-sectional view taken along a line 3-3 in Fig. 2, Fig. 4 is a cross-sectional view taken along a line 4-4 in Fig. 2, Fig. 5 is a cross-sectional view taken along a line 5-5 in Fig. 4, Fig. 6 is a cross-sectional view taken along a line 6-6 in Fig. 4, Fig. 7 is a cross-sectional view taken along a line 7-7 in Fig. 4, Fig. 8 is a cross-sectional view taken along a line 8-8 in Fig. 2, and Fig. 9 is a cross-sectional view taken along a line 9-9 in Fig. 8. [0023]
First of all, in Fig. 1, a vehicle body frame F of the

motorcycle includes a head pipe 16 which steerably supports a front folk 15 which pivotally supports a front wheel WF on a lower end portion thereof, a main frame 17 having, on a rear portion thereof , a downward extending portion 17a which extends rearward from the head pipe 16, is curved and then extends downward, a pair of left and right downward frames 18... which is inclined rearward and downward from the head pipe 16 and is arranged below the main frame 17, a pair of left and right sheet rails 19...which extends rearward from an upper portion of the downward extending portion 17a of the main frame 17, and a pair of left and right connection frames 20...which connects a lower' portion of the downward extending portion 17a and intermediate portions of both sheet rails 19.... [0024]
A steering handle 21 is connected to an upper end of the front folk 15, a rider' s-sheet 22 is mounted on the sheet rails 19..., and a fuel tank 23 which is arranged in front of the rider' s-sheet 22 and strides over the main frame 17 is mounted on the main frame 17. [0025]
In a portion surrounded by the main frame 17 and the down
frames 18..., a power unit P is arranged. A first bracket 24
is mounted on lower end portions of both down frames 18..., second
and third brackets 25, 26 are arranged at two pprtions of the
■I downward extending portion 17a of the main frame 17 which are

arranged in a vertically-spaced-apart manner, and the power
unit P is mounted on the first to third brackets 24, 25, 26.
-I
[0026] ;
A pivot frame 27 is fixedly mounted on the downward extending portion 17a of the main frame 17 between the second and third brackets 25, 26, front end portions of swing arms 28...which pivot ally support a rear wheel WR on a rear end portions thereof are tiltably supported on the pivot plate 27 by way of a support shaft 29, and a rear cushion unit 30 is arranged between the sheet rails 19...and the swing arms 28.... [0027]
Between a counter shaft 5 3 provided to the power unit P and an axle 32 of the rear wheel WR, a chain power transmission means 36 which is constituted of a drive sprocket wheel 33 which is mounted on the counter shaft 53, a driven sprocket wheel 34 which is fixed to the axle 32, and an endless chain 35 which is extended between and wound around the drive sprocket wheel 33 and the driven sprocket wheel 34 is arranged. [0028]
In Fig. 2, the power unit P is constituted of a single-cylinder engine E having a crankcase 37 which is mounted on the first to third brackets 24 , 25 , 26 , and a constant messing gear transmission M which is housed in the inside of the crankcase 37 such that power of the engine E is transmitted to the rear wheel WR in a speed-changing and reducing manner.

[0029]
The engine E includes the crankcase 37, a cylinder block 38 which is joined to an upper portion of the crankcase 37, a cylinder head 39 which is joined to an upper end of the cylinder block 38, and a head cover 40 which is joined to the cylinder head 39. [0030]
An upstream ends of intake pipes 41... which are connected to a rear side surface of the cylinder head 39 are connected to an air cleaner 43 by way of a carburetor 42, and the air cleaner 43 is fixedly arranged above a rear portion of the power unit P. Further, an exhaust pipe 44 which is connected to a front side surface of the cylinder head 39 extends rearward after passing below the power unit P and is connected to an exhaust muffler 45 which is arranged on a right side of the rear wheel WR. [0031]
The crankcase 37 is formed by joining a pair of left and right case half bodies 46, 47 to each other, and a crankshaft 48 having an axis along the widthwise direction of the motorcycle is rotatably supported by both case half bodies 46, 47. [0032]
The cylinder block 38 is joined to'the crankcase 37 in a state that the cylinder block 38 is inclined frontward and

upward in the advancing direction of the motorcycle, and a
cylinder bore 50 which allows slidable fitting of a piston 49
therein is formed in the cylinder block 38, and the piston 49
is connected to a crankpin 48a which the crankshaft 48 includes
by way of a connecting rod 51.
,1 [0033] '
The above-mentioned constant messing gear transmission M is formed by arranging a gear train of a plurality of gear shift positions which can be selectively established between a main shaft 52 to which power is transmitted from the crankshaft 48 and a countershaft 53. Here, the main shaft 52 and the counter shaft 53 are rotatably supported by the crankcase 3 7 in a state that the main shaft 52 and the countershaft 53 have axes arranged parallel to the crankshaft 48, and the drive sprocket wheel 33 is fixedly mounted on an end portion of the countershaft 53 which projects from the case half bodies 46 of the crankcase 36. [0034]
An intake valve 55 and an exhaust valve 56 are arranged in an openable and closable manner such that the intake valve 55 and the exhaust valve 56 are biased in the valve-closing direction, and a v^lve operation chamber 58 which houses a valve operating mechanism 57 which is driven so as to open or close the intake valve 55 and the exhaust valve 56 is formed between the cylinder head 39 and the head cover.40.

[0035]
To explain this embodiment also in conjunction with Fig. 3, an ignition plug 60 is mounted on the cylinder head 39 in a state that a distal end portion of the ignition plug 60 faces a combustion chamber 59 which is formed between the cylinder block 38 and the cylinder head 39. Here, a top portion of the piston 49 faces the combustion chamber 59. [0036]
Further, an upper portion of the cylinder head 39 is constituted of a bottom portion 39a which faces upwardly and a side wall portion 39b which projects upwardly from an outer periphery of the bottom portion 39a and is contiguously formed with the bottom portion 39a in an endless manner thus forming a box shape which opens upwardly. A lower portion of the head
cover 40 which is formed in a box shape opening downwardly is
i
brought into contact with a mating face 61 which is formed on an upper surface of the side wall portion 39b by way of a gasket 62. [0037]
The valve operating chamber 5 8 is formed between the upper portion of the cylinder head 39 and the head cover 40. The valve operating mechanism 57 housed in the valve operating chamber 58 includes a camshaft 53 which has an axis parallel to the crankshaft 48 and is arranged between the intake valve 55 and the exhaust valve 56, an intake-side rocker arm 66 which

is arranged between an intake-side cam 64 mounted on the camshaft 63 and the intake valve 55, and an exhaust-side rocker arm 67 which is arranged between an exhaust-side cam 65 mounted on the camshaft 6 3 and the exhaust valve 5 5. [0038]
To explain this embodiment also in conjunction with Fig. 4 to Fig. 6, the camshaft 63 is rotatably supported on the cylinder head 39 as follows. A pair of camshaft holders 68, 69 which projects upward from the bottom portion 39a of the upper portion of the cylinder head 39 is integrally formed with the cylinder head 39 in a spaced-apart manner in the axial direction of the camshaft 63. A ball bearing 70 is interposed between an inner peripheral surface of a support hole 72 formed in one camshaft holders 68 and an outer peripheral surface of one end portion of the camshaft 63, and a ball bearing 71 is interposed between an inner peripheral surface of the support hole 73 formed in another camshaft holder 69 coaxially with the support hole 72 and the camshaft 63. [0039]
The support hole 7 3 formed in another camshaft holder 69 has a diameter larger than a diameter of the support hole 72 formed in one camshaft holder. The camshaft 63 which mounts the ball bearings 70 , 71 on the outer peripheral surface thereof is assembled in the cylinder,head 39 such that the camshaft 63 is inserted into the support holes 72, 73 formed in both

camshaft holders 68, 69 from another camshaft holder 69 side. To another camshaft holder 69, an engagement plate 74 which is engaged with or is brought into contact with an outer race of the ball bearing 71 which is interposed between the camshaft 63 and the camshaft holder 69 .thus preventing removal of the camshaft 63 from both camshaft holders 68, 69 using a bolt 75. [0040].
Here, an axis of the support holes 72, 73 and the camshaft 63 are placed on a plane along the mating face 61. To enable assembling of the camshaft 63 in the cylinder head 39, a semicircular notched portion 76 which allows the insertion of the camshaft 63 into the support holes 72, 73 is formed on a portion of the side wall portion 39b which faces another end of the camshaft 63 above the cylinder head 39. and a lid portion 62a for closing the notched portion 76 is integrally formed with the gasket 62. [0041]
Rotational power from the crankshaft 48 is transmitted to the camshaft 63 at a speed reduction ratio of 1/2 by a timing power transmission means 78. The timing power transmission means 78 is constituted of a drive sprocket wheel (not shown in the drawing) which is mounted on the crankshaft 48, a driven sprocket wheel 80 which is fixed to another end portion of the camshaft 63, and an endless timing chain 81 which is extended between and wound around the drive sprocket wheel and the driven

sprocket wheel 80. A chain running passage 8 2 which allows running of the timing chain 81 therethrough is formed in the cylinder block 38 and the cylinder head 39. [0042]
The intake-side rocker arm 66 is rockably supported on an intake-side rocker shaft 83 provided between both camshaft holders 68, 69, a roller. 87 which is brought into ipolling contact with the intake-side cam 64 is pivotally supported on one end portion of the intake-side rocker arm 66, and a tappet screw 88 which is brought into contact with an upper end of the intake valve 55 is threadedly engaged with another end portion of the intake-side rocker arm 66 such that an advancing/retracting position of the tappet screw 88 can be adjusted. Further, the exhaust-side rocker arm 67 is rockably supported on an exhaust-side rocker shaft 84 provided between both camshaft holders 68, 69, a roller 89 which is brought into rolling contact with the exhaust-side cam 65 is pivotally supported on one end portion of the exhaust-side rocker arm 67, and a tappet screw 90 which is brought into contact with an upper end of the exhaust valve 56 is threadedly engaged with another end portion of the exhaust-side rocker arm 67 such that an advancing/retracting position of the tappet screw 90 can be adjusted. [0043]
In Fig. 7, a bottomed support hole 91 is formed in one

camshaft holder 68, and a support hole 92 which is a through hole coaxial with the support hole 91 is formed in another camshaft holder 69. The intake-side rocker shaft 83 is fitted into both support holes 91, 92 from the support hole 92 side, and for determining an axial-direction position of the intake-side rocker shaft 83, a screw member 85 which has a distal end portion thereof engaged with an outer periphery of the intake-side rocker shaft 83 is threadedly engaged with the camshaft holder 68. [0044] ,
The exhaust-side rocker shaft 84 is, in the same manner as the intake-side rocker shaft 83, fitted into the camshaft holders 68, 69, and a screw member 86 for determining an axial-direction position of the exhaust-side rocker shaft 84 (see Fig. 4) is fitted into the camshaft holder 69. [0045]
Here, a lower portion of the head cover 40 is brought into contact with the mating face 61 which is formed on the upper end of the side wall .portion 39b of the cylinder head 39 by way of the gasket 62 . In such constitution , by threadedly engaging two head cover fastening bolts 95, 95 which are inserted into the head cover 40 with two head cover fastening bosses 96, 97 which are integrally formed with the cylinder head 39, the head cover 40 is joined to the cylinder head 39. [0046]

The head cover fastening bosses 96, 97 are integrally formed on upper portions of the camshaft holders 68, 69 which are integrally formed with the cylinder head 39 so as to rotatably support the camshaft 63 which constitutes a portion of the valve operating mechanism 57. Here, upper ends of the head cover fastening bosses 96,97 are arranged above the mating face 61. These head cover fastening bosses 96, 97 are integrally formed on upper portions of the camshaft holders 68, 6 9 such that spaces are formed below the head cover fastening bosses 96, 97 and the head cover fastening bosses 96, 97 project sideward from the camshaft holders 68, 69. Further, the spaces below the head cover fastening bosses 96, 9 7 can be formed using a sand core at the time of forming the cylinder head 39 by casting. [0047]
Here, the cylinder block 38 and the cylinder head 39 are joined together to the crankcase 37 using a plurality of, for example, four stud bolts 98, 99. 100, 101 which are mounted on the crankcase 37 and a plurality of, for example, four nuts 102... with which these stud bolts 98 to 101 are threadedly engaged; Four stud bolt insertion bosses 103, 104, 105, 106 which allow the insertion of the respective stud bolts 98 to 101 therethrough are integrally formed on the cylinder head 39. [0048]

Four stud bolt insertion bosses 103 to 106 which respectively allow the insertion of the respective stud bolts 98 to 101 therethrough are integrally formed on four corners of both camshaft holders 68, 69. On two stud bolt insertion bosses 103, 105 which are arranged at diagonal positions out of these stud bolt insertion bosses 103 to 106, two head cover fastening bosses 96, 97 are respectively, individually, integrally and contiguously formed. Further, the head cover fastening bosses 96 , 97 are arranged at a position spaced apart inward from the side wall portion 39b of the upper portion of the cylinder head 39. [0049]
On upper ends of the stud bolt insertion bosses 103 to 106, nut engaging surfaces 103a, 104a, 105a, 106a which are arranged on the same plane as upper ends of the head cover fastening bosses 96, 97 are formed. The nuts 102... which are threadedly engaged with the stud bolts 98 to 101 are brought into contact with or engaged with the nut engaging surfaces 103a to 106a by way of washers 107.... [0050]
The head cover fastening bolts 95... are inserted into the head cover 4 0 with annular sealing members 10 8... interposed between the head cover fastening bolts 95... and the head cover 40 . The head cover fastening bolts 95... include flange portions 95a... which are brought into contact with upper ends of the head

cover fastening bosses 96, 97, and screw shaft portions 95b... which project from the flange portions 95a coaxially. The screw shaft portions 9 5... are threadedly engaged with threaded holes 109, 110 which are formed in the head cover fastening bosses 96, 97. [0051]
Here, lower ends of the head cover fastening bosses 96, 97 are arranged above the mating face 61 of the cylinder head 39, and the threaded holes 109, 110 vertically penetrate the head cover fastening bosses 96 , 97 such that the threaded holes 109, 110 have lower opening ends thereof arranged above the mating face 61 of the cylinder head 39. [0052]
As shown in Fig. 2 , Fig. 3 , Fig. 8 and Fig . 9 , an oil passage 111 which extends in the direction orthogonal to the axis of the camshaft 63 is formed in the head cover 40. As shown in Fig. 2 and Fig. 8, two oil jets 112, 113 which are communicated with the oil passage 111 are formed in the head cover 40 such that these oil jets 112 , 113 blow off oil to the valve operating mechanism 57 side. [0053]
Here, between the stud bolt 99 which is inserted into at least one specific stud bolt insertion boss out of two stud bolt insertion bosses excluding the stud bolt insertion bosses 103, 105 which are integrally and contiguously formed with the

head cover fastening bosses 96, 97 out of four stud bolt insertion bosses 103 to 106 (in this embodiment, one specific stud bolt insertion boss 104) and the cylinder head 39, as shown in Fig. 5, an annular oil passage 114 is formed. Also between the stud bolt 9 9 and the cylinder block 3 8, an annular oil passage 115 which is communicated with the annular oil passage 114 is formed, and the annular oil passage 115 is connected with an oil supply source not shown in the drawing through an oil passage 116 formed in the crankcase 37. [0054]
A branch passage 117 which is branched from a midst portion of the annular oil passage 114 is formed in the cylinder head 39 and extends in an oblique upward direction so as to guide oil to the oil passage 111 side of the head cover side 40. A lower end of a communication passage 118 which is communicated with the oil passage 111 and extends downward and an upper end of the branch passage 117 are connected with each other by way of a sleeve 119 sandwiched between the cylinder head 39 and a head cover 40. [0055] ;
Next, the manner of operation of this embodiment is explained. On the upper portions of the cam shaft holders 68, 69 which are integrally formed on the cylinder head 39 so as to rotatably support the camshaft 63 which constitutes a portion of the valve operating mechanism 57, the head cover

fastening bosses 96, 97 whose upper ends are arranged above the mating face 61 of the upper end of the cylinder head 39 are integrally formed such that.the head cover fastening bosses 96, 97 project sideward from the cam shaft holders 68, 69. Accordingly, a length of the head cover fastening bolts 95... can be shortened and hence, the cylinder head 39 can be light-weighted and, at the same time, the assembling property of the cylinder head 39 can be enhanced. Further, the spaces are formed below the head cover fastening bosses 96, 97 and hence, the cylinder head 39 can be light-weighted due to the reduction of wall thicknesses of the head cover fastening bosses 96 , 97 from below. Still further, by forming the spaces using the sand cores at the time of forming the cylinder head 3 9 by casting, the increase of the number of cores becomes unnecessary and hence, it is possible to form the spaces below the head cover fastening bosses 96, 97 while suppressing the increase of a cost. [0056}
Further, the upper portion of the cylinder head 39 is constituted of the bottom portion 39a on which the head cover fastening bosses 96, 97 are formed in a projecting manner and the side wall portion 39b which projects upwardly from the outer periphery of the bottom portion 39a thus forming a box shape which is opened upward, and the head cover fastening bosses 96, 97 are arranged at positions spaced-apart inward from the

side wail portion 39b which forms the mating face 61 on the upper end thereof. Accordingly, the head cover fastening bosses 96, 97 do not become obstacles in forming the mating face 61 thus easing the forming of the mating face 61. Further, although there exists a possibility that blow-holes are formed in an outer surface of the side wall portion 39b at the time of casting the cylinder head 39 when the side wall portion 39b and the head cover fastening bosses 96, 97 are integrally and contiguously formed, the head cover fastening bosses 96, 97 are arranged at positions spaced-apart inward from the side wall portion 39b and hence, the formation of the blow-holes can be surely prevented thus easing the maintenance of appearance of the cylinder head 3 9. Further, due to the structure which prevents the direct connection of the head cover fastening bosses 96, 97 with the side wall portion 39b and the bottom portion 39a, a recessed portion in which lubrication oil stays is hardly formed in the upper portion of the cylinder head 39 thus improving the return of lubrication oil from the cylinder head 39. [0057]
Further, the cylinder block 38 and the cylinder head 39 are joined together to the crankcase 3 7 using the plurality of, for example, four stud bolts 98, 99, 100, 101 and the plurality of nuts 102..., and on the upper ends of the stud bolt insertion bosses 103, 104, 105, 106 which are integrally formed

with the cylinder head 39 such that the stud bolts 98 to 101 are respectively inserted into the stud bolt insertion bosses 103, 104, 105, 106, nut engaging surfaces 103a, 104a, 105a, 106a which are arranged on the same plane as upper ends of the head cover fastening bosses 96, 97 are formed. Accordingly, forming of the upper ends of the head cover fastening bosses 96, 97 and forming of the nut engaging surfaces 103a to lQ6a can be easily performed. [0058]
Further, four stud bolt insertion bosses 103 to 106 which respectively allow the insertion of the respective four stud bolts 98 to 101 therethrough are integrally formed on four corners of both camshaft holder 68, 69. Accordingly, it is possible to make the stud bolt insertion bosses 103 to 106 functioh as strength-and-rigidity portions of the cam shaft holders 68, 69. Two head cover fastening bosses 96, 97 are respectively individually and integrally formed on two stud bolt insertion bosses 103, 105 arranged at two diagonal positions and hence, by contiguously forming the head cover fastening bosses 9.6, 97 on the stud bolt insertion bosses 103, 105 having high strength and rigidity, it is possible to increase the strength and the rigidity of the head cover fastening bosses 96, 97. Further, the stud bolt insertion bosses l03, 105 and the head cover fastening bosses 96, 97 can be arranged close to each other and hence, a moving distance

of a tool for machining upper end surfaces of the stud bolt insertion bosses 103, 105 and the head cover fastening bosses 96, 97 can be decreased thus contributing to shortening of forming time. [0059]
Further, by contiguously forming the head cover fastening bosses 96, 97 on the stud bolt insertion bosses 103, 105 which are arranged at diagonal positions at four corners of the cam shaft holders 68, 69, a distance between two head cover fastening bosses 96, 97 can be set to a large value and hence, the head cover 40 can be fixed to the cylinder head 39 in a stable manner. [0060]
Further, the annular oil passage 114 is formed between the stud bolt 99 which is inserted into the specific stud bolt insertion boss 104 different from the stud bolt insertion bosses 103, 105 on which the head cover fastening bosses 96, 97 are integrally and contiguously formed and the cylinder head 39 , and the branch passage 117 which is branched from the midst portion of the annular oil passage 114 and is communicated with the oil passage 111 formed in the head cover 40 is formed in the cylinder head 39 . Due to such constitution, the head cover fastening bosses 96, 97 and the branch passage 117 can be arranged in a spaced-apart manner from each other thus preventing large-sizing of the cylinder head 3 9.

[0061] :
Further, the lower ends of the head cover fastening bosses 96, 97 are arranged above the mating face 61 of the cylinder head 39 and hence, the reduction of weight of the head cover fastening bosses 96, 97 can be enhanced. [0062]
Further, the threaded holes 109, 110 with which the head cover fastening bolts 9 5... are threadedly engaged are formed in the head cover fastening bosses 96, 97 in a state that the threaded holes 109, 110 vertically penetrates the head cover fastening bosses 96, 97. Accordingly, lower-hole forming and threads forming of the threaded holes 109, 110 can be easily performed and, at the same time, the cut debris can be also easily removed. Further, heights of the head cover fastening bosses 96, 97 can be set corresponding to the required threaded hole distance and hence, the head cover fastening bosses 96, 97 can be miniaturized thus enhancing the reduction of weight more effectively. [0063] 1
Further, the lower opening ends of the threaded holes 109, 110 are arranged above the mating face 61 of the cylinder head 39 and hence, the lower opening ends of the threaded holes 109 , 110 can be easily observed and a tool can be easily inserted into the lower opening end side of the threaded holes 109, 110 thus easing a burr removing operation.

Although the embodiment of the present invention has been explained heretofore, the present invention is not limited to the above-mentioned embodiment and various design changes can be made without departing from the gist of the present invention described in Claims.
[Brief Description of the Drawings] [00653 [Fig. 1]
A right side view of a motorcycle. [Fig. 2]
A longitudinal cross-sectional side view of a power unit. [Fig. 3]
A cross-sectional view taken along a line 3-3 in Fig. 2. [Fig. 4]
A cross-sectional view taken along a line 4-4 in Fig. 2. [Fig. 5;]
A crossTsectional view taken along a line 5-5 in Fig. 4. [Fig. 6]
A cross-sectional view taken along a line 6-6 in Fig.
4 - '. [Fig. 7]

A cross-sectional view taken along a line 7-7 in Fig 4 . [Fig. 8]
A cross-sectional view taken along a line 8-8 in Fig 2. [Fig. 9]
A cross-sectional view taken along a line 9-9 in Fig 8.
[Description of Reference Numerals and Signs] [0066]
37: crankcase 38: cylinder block 39: cylinder head 39a: bottom portion 39b: side wall portion 40: head cover 49: piston 50: cylinder bore 55: intake valve 56: exhaust valve 57: valve operating mechanism 58: valve operating chamber 61: mating face 62: gasket 63: cam shaft

68, 69: cam shaft holder
95: head cover fastening bolt
96, 97: head cover fastening boss
98, 99, 100, 101: stud bolt
102: nut
103, 104, 105, 106: Stud bolt insertion boss
103a, 104a, 105a, 106a: nut engaging surface
109, 110: threaded hole
111: oil passage
114: annular oil passage
117: branch passage
E: engine

[Designation of Document] Claims [Claim 1]
A cylinder head structure of an engine in which a cylinder head (39) which arranges an intake valve (55) and an exhaust valve (56) therein in an openable and closable manner is joined to an upper portion of a cylinder block (38) including a cylinder bore (50) in which a piston (49) is slidably fitted, a lower portion of a head cover (40) which defines a valve operating chamber (58) housing a valve operating mechanism ( 57 ) for driving the intake valve (55) and the exhaust valve (56) in an openable and closable manner between the head cover (40) and the cylinder head (39) is brought into contact with a mating face (61) formed on an upper portion of the cylinder head (39) by way of a gasket (62), and head cover fastening bolts (95) which aire inserted into the head cover (40) are threadedly engaged; with head cover fastening bosses (96, 97) which are integrally formed on the cylinder head (39), wherein
on upper portions of cam shaft holders (68, 69) which are integrally formed with the cylinder head (39) so as to rotatably support a camshaft (63) which constitutes a portion of the valve operating mechanism ( 57 ) , the head cover fastening bosses (96, 97) which have upper ends thereof arranged above the mating face (61) are integrally formed such that the head cover fastening bosses (96, 97) project sideward from the cam shaft holders (68, 69) so as to form spaces below the head cover

fastening bosses (96, 97). [Claim 2]
A cylinder head structure of an engine according to claim 1, wherein the upper portion of the cylinder head (39) is constituted of a bottom portion (39a) on which the cam shaft holders (68, 69 ) are formed in a projecting manner and the side wall portion (39b) which projects upwardly from an outer periphery of the bottom portion (39a) and forms the mating face (61) on an upper end thereof thus forming a box shape which is opened upwardly, and the head cover fastening bosses (96, 97) are arranged at positions spaced-apart inward from the side wall portion (39b). [Claim 3]
A cylinder head structure of an engine according to claim 1 or claim 2, wherein the cylinder block (38) and the cylinder head (39) are joined together to the cxankcase (37) using a plurality of stud bolts (98, 99, 100, 101) which are mounted on the crankcase (37) and a plurality of nuts (102) which are respectively threadedly engaged with the stud bolts ( 98 to 101) , and on upper ends of stud bolt insertion bosses (103, 104, 105, 106) which are integrally formed with the cylinder head (39) such that the plurality of stud bolts (98 to 101) is respectively inserted into the stud bolt insertion bosses (103 to 106), nut engaging surfaces (103a, 104a, 105a, 106a) which are arranged on the same plane as the upper ends of the head

cover fastening bosses (96, 97) are formed so as to bring the nuts (102) into contact and engagement with the nut engaging surfaces (103a, 104a, 105a, 106a). [Claim 4]
A cylinder head structure of an engine according to claim
3, wherein four stud bolt insertion bosses (103 to 106) which
respectively allow the insertion of said four stud bolts (98
to 101) therethrough are integrally formed on four corners of
the camshaft holders ( 68 , 69 ) , and said two head cover fastening
bosses (96, 97) are respectively individually and integrally
formed on said two stud bolt insertion bosses (103, 105) which
are arranged at diagonal positions out of the stud bolt
insertion bosses (103 to 106).
[Claim 5]
A' cylinder head structure of an engine according to claim
4, wherein between the stud bolt (99) which is inserted into
at least one specific stud bolt insertion boss (104) out of
two stud bolt insertion bosses (104, 106) excluding the stud
bolt insertion bosses (103, 105) which are integrally and
contiguously formed with the head cover fastening bosses (96,
97) and the cylinder head (39), an annular oil passage (114)
is formed, and a branch passage (117) which is branched from
a midst portion of the annular oil passage (114) is formed in
the cylinder head (39) so as to guide oil toward an oil passage
(111) formed in the head cover (40).

[Claim 6]
A cylinder head structure of a.n engine according to any¬one of claims 1 to 5, wherein threaded holes (109, 110) with which the head cover fastening bolts (95) are 'threadedly engaged are formed in the head cover fastening bosses (96, 97 ) in a state that the threaded holes (109, 110) vertically penetrate the head cover fastening bosses (95, 97). [Claim 7]
A cylinder head structure of an engine according to claim 6, wherein lower opening ends of the threaded holes (109, 110) are arranged above the mating face (61) of the cylinder head (39). [Claim 8]
A cylinder head structure of an engine according to any one of claims 1 to 6, wherein lower ends of the head cover fastening bosses (96, 97) are arranged above the mating face (61) of the cylinder head (39).

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=LFK1FZ1N2zZkUqB7VkZ7lg==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

272482

Indian Patent Application Number

1105/CHE/2009

PG Journal Number

15/2016

Publication Date

08-Apr-2016

Grant Date

04-Apr-2016

Date of Filing

12-May-2009

Name of Patentee

HONDA MOTOR CO; LTD

Applicant Address

1-1 MINAMI-AOYAMA 2-CHOME, MINATO-KU, TOKYO 107-8556

Inventors:

#	Inventor's Name	Inventor's Address
1	MIZUTANI, FUMINORI,	C/O HONDA R&D CO; LTD. 4-1, CHUO 1-CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193
2	KONO, NAOKI,	C/O HONDA R&D CO; LTD. 4-1, CHUO 1-CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193

PCT International Classification Number

F02B1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2008-133410	2008-05-21	Japan