Title of Invention

"DEVICE FOR PREVENTING ROTATION OF ROCKER LEVER SHAFT"

Abstract

A pair of rocker lever shafts 26 are juxtaposed in spaced relation to each other in a cylinder head 4; and a pair of rocker levers 28, held in contact with respective intake and exhaust cams 18a and with respective intake and exhaust valves 16, 17, are supported swingably by the rocker lever shafts 26, respectively. The rocker lever shafts 26 have respective cutouts 26a formed in portions thereof and facing each other, and a restrictive member 40 having non-parallel side edges as viewed in the axial direction of a camshaft is inserted between the cutouts 26a. The restrictive member 40 is pressed by an inner surface of a cylinder head cover 5. Thus, a problem of a clearance being formed as a result of tightening a rotation preventing member for the rocker lever shafts in a valve operating system of an internal combustion engine is solved ,and a problem of striking sounds being produced by the rocker lever shaft rotation during engine operation is eliminated.

Full Text

DESCRIPTION DEVICE FOR PREVENTING ROTATION OF ROCKER LEVER SHAFT TECHNICAL FIELD The present invention relates to a device for preventing rotation of a rocker lever shaft in a valve operating system of an internal combustion engine. BACKGROUND ART It has been known heretofore to use a stopper for preventing removal of a rocker lever shaft which is press-fitted in a rocker lever shaft hole (see, for example, JP 2000-329002 A, Figs. 6 and 7). There has also been known a device for preventing rotation of a rocker lever shaft as shown in FIG. 8. The rocker lever shaft rotation prevention device has a set plate 040 fastened at its central portion between two rocker lever shafts 026 to a cylinder head 04 with a fastening bolt 023. The set plate 040 has left and right arms having symmetrical rotation prevention surfaces 040a formed on the lower surfaces of the opposite ends thereof. The rotation prevention surfaces 040a are held in abutment against respective cutouts 026a defined in two rocker lever shafts 026 for preventing rotation of the rocker lever shafts 026. In FIG. 8, the reference numeral 018 represents a camshaft, and the reference numeral 019 represents a camshaft bearing. When the set plate 040 of the above-stated rocker lever shaft rotation prevention device is fastened by the fastening bolt 023, the set plate 040 is rotated in the direction in which the fastening bolt 023 is tightened, so that a slight gap S is created between the cutout 026a of one (the left rocker lever shaft in FIG. 8) of the rocker lever shafts 026, which is positioned behind the set plate 040 with respect to the direction of rotation of the set plate 040, and the associated rotation prevention surface 040a of the set plate 040. Therefore, while the internal combustion engine is in operation, the gap S causes the rocker lever shaft 026 to turn idly, producing striking sounds. It is the object of the present invention to provide a device for preventing rotation of a rocker lever shaft in a valve operating system of an internal combustion engine, in which creation of a gap due to tightening of the set plate is prevented. DISCLOSURE OF THE INVENTION To solve the above problem, the present invention provides a device for preventing rotation of rocker lever shafts in a valve operating system of an internal combustion engine, having a pair of rocker lever shafts juxtaposed in spaced relation to each other in a cylinder head; a pair of rocker levers held in contact with respective intake and exhaust cams and respective intake and exhaust valves and swingably supported by the rocker lever shafts, respectively; and a restrictive member provided for preventing rotation of the rocker lever shafts; characterized in that the rocker lever shafts have respective cutouts formed in portions thereof and facing each other, the restrictive member has non-parallel side edges as viewed in axial direction of a camshaft; and the restrictive member is inserted between the cutouts, the restrictive member being pressed by an inner surface of a cylinder head cover. In the present invention, the restrictive member having the non-parallel side edges as viewed axially of the camshaft is inserted between the mutually facing cutouts formed in the rocker lever shafts, and the restrictive member is pressed by the inner surface of the cylinder head cover. The rocker lever shafts and the restrictive member are thus fixed in close contact with each other without rattling movement. Therefore, the generation of striking sounds and wear of bearings due to idling rotation of the rocker lever shafts are prevented. Furthermore, since the restrictive member is pressed and secured by the cylinder head cover, fastening bolts for the restrictive member, a threaded hole machining process, and a fastening process, which have heretofore been required by the conventional rocker lever shaft rotation prevention device, are dispensed with, resulting in an advantage as to manufacturing cost. According to the invention, the restrictive member may be shaped to sandwich a protruding portion in the cylinder head in the direction of the camshaft. By doing so, the rocker lever shafts are prevented from displacing axially thereof and their wear can be prevented. Further, the restrictive member is fixed, using the existing protruding portion, whereby the restrictive member can be fixed in position without requiring special work on the cylinder head. Preferably, a cam shaft holder can be employed as the protruding portion. The restrictive member may have an inverted U-shape in cross section for enabling fitting on the protruding portion. Thus, positioning of the restrictive member is facilitated. A resilient member may be disposed between the restrictive member and the inner surface of the cylinder head cover and between the restrictive member and the protruding portion. Thus, the restrictive member can be fixed reliably. Further, noise owing to vibrations is reduced because vibrations of the cylinder head cover are absorbed by the resilient member. The restrictive member is preferably held in abutment against an outer surface of a camshaft bearing, whereby rattling of the camshaft bearing is reduced and the camshaft bearing is given increased durability. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of an internal combustion engine to which an embodiment of the present invention is applied, taken along a plane which extends substantially through a crankshaft axis and a cylinder axis ; FIG. 2 is a vertical sectional view of the internal combustion engine, taken along a plane which extends substantially through the cylinder axis and perpendicularly to the crankshaft axis; FIG. 3 is a vertical sectional view of the internal combustion engine, taken along a plane which extends perpendicularly to the crankshaft axis near a cam timing chain; FIG. 4 is an enlarged view of an upper portion of FIG. 1; FIG. 5 is a view of a cylinder head, as viewed from above, with a cylinder head cover removed; FIG. 6 is a cross-sectional view taken along line VI - VI of FIG. 5; FIG. 7 is a sectional view taken along line VII - VII of FIGS. 4 and 6; and FIG. 8 is a view showing an example of a conventional device for preventing rotation of a rocker arm shaft. BEST MODE FOR CARRYING OUT THE INVENTION FIG. I shows an internal combustion engine to which an embodiment of the present invention is applied, in vertical section taken along a plane which extends through a crankshaft axis and a cylinder axis. FIG. 2 shows the internal combustion engine in section taken along a plane which extends through the cylinder axis and perpendicularly to the crankshaft axis. FIG. 3 shows the internal combustion engine in a section taken along a plane which extends perpendicularly to the crankshaft axis near a cam chain, and FIG. 4 shows an upper portion of FIG. 1 on an enlarged scale. An internal combustion engine 1 is an overhead-camshaft 4-stroke cycle single-cylinder internal combustion engine having a main body which comprises a left crankcase 2a, a right crankcase 2b, a cylinder block 3, a cylinder head 4, a cylinder head cover 5, a left crankcase cover 6a, and a right crankcase cover 6b. The left crankcase 2a and the right crankcase 2b are assembled together, and the cylinder block 3, the cylinder head 4, and the cylinder head cover 5 are successively mounted on the assembly. The left crankcase cover 6a is assembled on a left side surface of the left crankcase 2a, and the right crankcase cover 6b is assembled on a right side surface of the right crankcase 2b, in such a manner that the crankcases are closed by these crankcase covers, respectively. The left and right crankcases 2a and 2b, the cylinder block 3, the cylinder head 4, the cylinder head cover 5, the left crankcase cover 6a, and the right crankcase cover 6b are coupled together with bolts or the like. As shown in FIGS. 1 and 2, a piston 8 is slidably fitted in a cylinder bore 7 defined in the cylinder block 3, and a crankshaft 9 is rotatably supported in the left and right crankcases 2a and 2b. A connecting rod 12 has opposite ends pivotally mounted on the piston 8 and the crankshaft 9, respectively, by a piston pin 10 and a crankpin 11, respectively. When the piston 8 is reciprocally moved by the combustion of an air-fuel mixture in a combustion chamber 13 in a top region of the cylinder bore 7, the crankshaft 9 is rotated. As shown in FIG.2, an intake port 14 and an exhaust port 15 are defined in the cylinder head 4 in communication with the combustion chamber 13 in the top region of the cylinder bore 7. An intake valve 16 and an exhaust valve 17 are openably and closably mounted in the intake port 14 and the exhaust port 15, respectively. A camshaft 18 is disposed adjacent to the top ends of the intake valve 16 and the exhaust valve 17. A cam lobe 18a for the intake valve 16 and a cam lobe 18a for the exhaust valve 17 are provided on the camshaft 18. The camshaft 18 has one end (left end in FIGS. 1 and 4) rotatably supported by a camshaft bearing 19a between the cylinder head 4 and a camshaft holder 20, and an opposite end (right end in FIGS. 1 and 4) rotatably supported by a camshaft bearing 19b in the cylinder head 4. A driven sprocket 21 and a magnet holder 22 are stacked and integrally mounted on the one end of the camshaft 18 by bolts 23. A drive sprocket 24 is integrally mounted on the crankshaft 9. An endless cam timing chain 25 is trained around the drive sprocket 24 and the driven sprocket 21. As shown in FIG. 2, a pair of rocker lever shafts 26 with respective horizontal axes are disposed intermediate between the top end of the intake valve 16 and a position above the camshaft 18 and between the top end of the exhaust valve 17 and the position above the camshaft 18. The rocker lever shafts 26 have opposite ends supported in the cylinder head 4 and the camshaft holder 20. Rocker levers 28 are swingably supported on the rocker lever shafts 26, respectively. Rollers 29 are pivotally mounted on respective one ends of the rocker levers 28 and held in abutment against the cam lobes 18a of the camshaft 18. The other ends of the rocker levers 28 are held in abutment against the top ends of the intake valve 16 and the exhaust valve 17. When the internal combustion engine 1 is in operation, the camshaft 18 rotates at a rotational speed which is half the rotational speed of the crankshaft 9, causing the intake valve 16 and the exhaust valve 17 to be opened and closed once each time the crankshaft 9 makes two revolutions. As shown in FIGS. 1 and 4, the magnet holder 22 which is integrally mounted on the one end (left end in FIGS. 1 and 4) of the camshaft 18 has a reduced-diameter cylindrical portion positioned radially inside of the driven sprocket 21 and an enlarged-diameter cylindrical portion positioned axially outwardly of the reduced-diameter cylindrical portion. A plurality of permanent magnets 35 are integrally mounted at circumferentially equally spaced intervals on an inner circumferential surface of the enlarged-diameter cylindrical portion. A coolant pump 30 is disposed outwardly (leftwardly in FIGS. 1 and 4) of the camshaft 18. The coolant pump 30 has a pump cover 31 fitted in an opening defined in a side wall of the cylinder head 4, and a pump body 32 having a proximal end sealingly fitted in the pump cover 31. The pump body 32 has a cylindrical portion spaced a given distance from the enlarged-diameter cylindrical portion of the magnet holder 22. The coolant pump 30 also has a pump shaft 33 aligned with the axis of rotation of the camshaft 18 and having opposite ends rotatably supported respectively in the pump cover 31 and the pump body 32. A rotor 34 is mounted on the pump shaft 33 and has a cylindrical portion on which are mounted permanent magnets 36 in positions confronting the permanent magnets 35 that are integrally mounted on the magnet holder 22. Vanes 37 are integrally mounted on the rotor 34 outwardly (leftwardly in FIG. 4) of the cylindrical portion of the rotor 34. When the driven sprocket 21 is rotated, the magnet holder 22 integral therewith is rotated, causing the permanent magnets 36 integrally mounted on the rotor 34 of the coolant pump 30 to rotate under magnetic forces of the permanent magnets 35 that rotate with the magnet holder 22. The coolant pump 30 is thus actuated to rotate, FIG. 5 is a view of the cylinder head 4, as viewed from above, with the cylinder head cover 5 removed. FIG. 6 is a sectional view taken along line VI - VI of FIG. 5, while FIG. 7 is a sectional view taken along line VII -VII of FIGS. 4 and 6. According to the present embodiment, the rocker lever shafts 26 have cutouts 26a formed in ends thereof (left ends in FIG. 5 and lower ends in FIG. 7) and facing each other. Each cutout 26a typically has a planar cutout surface, and as shown in FIG.6, oppositely facing planar cutout surfaces are slanted surfaces that approach each other as they extend downwards. A set plate 40, having non-parallel opposite side edges as viewed in the axial direction of the camshaft 18 (downwardly convergent in FIG. 6), is inserted as a restrictive member from above between the cutouts 26a. As shown in FIGS. 4 and 6, the set plate 40 has a lower arcuate edge held in abutment against an outer side surface of the outer ring of the camshaft bearing 19a, and an upper edge bent horizontally. The horizontally bent portion extends to a region above the camshaft holder 20 which serves as a protruding portion in the cylinder head 4, and is then bent downwardly, thus sandwiching the camshaft holder 20. As shown in Fig.4, the set plate 40 has thus an inverted U-shape in section. The protruding portion for holding the set plate 40 may be a protruding part other than the cam shaft holder 20 which is located at a position adjacent to the cam shaft 18 and within the cylinder head 4. A resilient member 42 such as a rubber member is disposed between the set plate 40 and the camshaft holder 20 and between the set plate 40 and the inner surface of the cylinder head cover 5, and is pressed by the cylinder head cover 5. The dot-and-dash lines 42A in FIG. 6 represent the shape of the resilient member 42 in its free state. When the cylinder head cover 5 is installed, the resilient member 42 is pressed into the shape shown in FIG. 4. The reference numeral 27 in FIGS. 5 and 7 represents collars fitted on the rocker lever shaft 26 to prevent axial displacement of the rocker levers 28. When an air-fuel mixture supplied to the combustion chamber 13 in the internal combustion engine 1 is ignited, the fuel is combusted to increase the pressure in the combustion chamber 13, lowering the piston 8. By operating the intake valve 16 and the exhaust valve 17 and repeatedly supplying the air-fuel mixture, discharging the exhaust gas, and igniting the air-fuel mixture according to a predetermined sequence and timing, the piston 8 is reciprocally moved. The movement of the piston 8 is transmitted by the connecting rod 12 and converted into rotation of the crankshaft 9, which is then transmitted to wheels (not shown) or the like. The rotation of the crankshaft 9 is also transmitted through the drive sprocket 24, the cam timing chain 25, and the driven sprocket 21 to the camshaft 18, and then transmitted through the cam lobes 18a and the rocker levers 28 to open and close the intake valve 16 and the exhaust valve 17 according to a predetermined sequence and timing. According to the present embodiment, the rocker lever shafts 26 have the cutouts 26a defined in the ends thereof and facing each other, and the set plate 40 having the non-parallel (tapered) side edges as viewed in the axial direction of the camshaft 18 is inserted between the cutouts 26a. The set plate 40 is pressed by the inner surface of the cylinder head cover 5. Therefore, the rocker lever shafts 28 and the set plate 40 are thus fixed in close contact with each other without rattling movement. Thus, the generation of striking sounds and the wear of bearings due to idling rotation of the rocker lever shafts 26 are prevented. Furthermore, since the set plate 40 is pressed and secured by the cylinder head cover 5, fastening bolts for the restrictive member, a threaded hole machining process, and a fastening process, which have heretofore been required by the conventional rocker lever shaft rotation prevention device, are dispensed with, resulting in an advantage as to the manufacturing cost. According to the present embodiment, furthermore, the set plate 40 is shaped to sandwich the camshaft holder 20 so as to be restricted in movement in the direction of the camshaft 18, whereby the rocker lever shafts 26 are prevented from being worn by displacement in the axial direction thereof. Further, the set plate 40 is fixed using the existing camshaft holder 20, so that the set plate 40 is fixed in position without the need for special machining of the cylinder head 4. According to the present embodiment, furthermore, the resilient member 42 such as a rubber member is disposed between the set plate 40 and the camshaft holder 20 and between the set plate 40 and the inner surface of the cylinder head cover 5, whereby the set plate 40 is reliably fixed in position. Noise owing to vibrations is reduced as vibrations of the cylinder head cover 5 are absorbed by the resilient member 42. According to the present embodiment, furthermore, as the set plate 40 has the lower end held in abutment against the outer side surface of the outer ring of the camshaft bearing 19a, the camshaft bearing 19a is prevented from rattling and has increased durability. CLAIMS 1. A device for preventing rotation of rocker lever shafts in a valve operating system of an internal combustion engine, having a pair of rocker lever shafts juxtaposed in spaced relation to each other in a cylinder head; a pair of rocker levers held in contact with respective intake and exhaust cams and respective intake and exhaust valves and swingably supported by the rocker lever shafts, respectively; and a restrictive member provided for preventing rotation of the rocker lever shafts; characterized in that said rocker lever shafts have respective cutouts formed in portions thereof and facing each other, said restrictive member has non-parallel side edges as viewed in axial direction of a camshaft; and the restrictive member is inserted between the cutouts, said restrictive member being pressed by an inner surface of a cylinder head cover. 2. A device for preventing rotation of rocker lever shafts according to claim 1, characterized in that said restrictive member is shaped to sandwich a protruding portion in the cylinder head in an axial direction of the camshaft. 3. A device for preventing rotation of rocker lever shafts according to claim 2, characterized in that said protruding portion is a camshaft holder. 4. A device for preventing rotation of rocker lever shafts according to claim 1or 2, characterized in that said restrictive member has an inverted U-shape in cross- section. 5. A device for preventing rotation of rocker lever shafts according to claim 1 or 2, characterized in that said cutouts facing each other are slanting surfaces converging downwards. 6. A device for preventing rotation of rocker lever shafts according to claim 1 or 2, characterized in that a resilient member is disposed between said restrictive member and said inner surface of the cylinder head cover and between said restrictive member and said protruding portion. 7. A device for preventing rotation of rocker lever shafts according to claim I or 2, characterized in that said restrictive member is held in abutment against an outer surface of a camshaft bearing.

Documents:

1783-DELNP-2005-Abstract(11-1-2008).pdf

1783-delnp-2005-abstract.pdf

1783-DELNP-2005-Claims(11-1-2008).pdf

1783-delnp-2005-claims.pdf

1783-DELNP-2005-Correspondence-Others(11-1-2008).pdf

1783-delnp-2005-correspondence-others.pdf

1783-delnp-2005-description (complete).pdf

1783-DELNP-2005-Drawings(11-1-2008).pdf

1783-delnp-2005-drawings.pdf

1783-delnp-2005-form-1.pdf

1783-delnp-2005-form-18.pdf

1783-DELNP-2005-Form-2(11-1-2008).pdf

1783-delnp-2005-form-2.pdf

1783-DELNP-2005-Form-3(11-1-2008).pdf

1783-delnp-2005-form-3.pdf

1783-delnp-2005-form-5.pdf

1783-DELNP-2005-GPA(11-1-2008).pdf

1783-delnp-2005-gpa.pdf

1783-delnp-2005-pct-304.pdf

1783-delnp-2005-pct-311.pdf

1783-DELNP-2005-Petition-137(11-1-2008).pdf

1783-DELNP-2005-Petition-138(11-1-2008).pdf