Title of Invention

OIL TEMPERATURE DETECTION STRUCTURE OF TWO-WHEELED MOTOR VEHICLE ENGINE

Abstract

The present invention to provide an oil temperature detection structure of a two wheeled motor vehicle engine in which luibricating oil returned from a cylinder head collects in an oil pool integrally formed in a crankcase and measures oil temperature of the lubricating oil, Provides is an oil temperature detection structure of a two-wheeled motro vehicle engine for measuring temperature of lubricating oil lubricating an engine 1 which inclides a cylinder head, 3, a cylinder block 4, and a crankcase 5 and which is attached to a two-wheeled motor vehicle with a cylinder chamber 7 extending substantially horizontally to the ground, and being provided for the cylinder block 4, the oil temperature detection structure including an oil pool 49 in which the lubricating oil returened from the cylinder head 3 collects and an oil temperature sensor 50. The oil pool 49 is integrally formed with the crankcase 5 in front bottom part of the crankcase 5. The oil temperature 50 is attached to the crankcase 5 and measures the temperature of the lubricating oil having collected in the oil pool 49.

Full Text

The present invention relates to an oil temperature detection structure of a two-wheeled motor vehicle engine to measure temperature of lubricating oil returned from a cylinder head of an engine mounted on a two-wheeled motor vehicle. [Background Art] [0002] In order to efficiently fire fuel supplied to an engine, it is necessary to measure temperature in a vicinity of a combustion chamber. In an air-cooling engine, temperature of lubricating oil having lubricated a cylinder head is measured for control. As known methods of measuring the temperature of the lubricating oil, there are a measurement method in which an oil passage to return lubricating oil from the cylinder head to a crankcase is formed in a cylinder block, and in which an oil temperature sensor is provided for this oil passage (for example, see Patent Literature l); and a measurement method in which an oil passage to supply lubricating oil to a valve operating mechanism provided for the cylinder head is formed in the cylinder head and a cylinder head cover, and in which the oil temperature sensor is provided for this oil passage (for example, see Patent Literature 2). [0003] [Patent Literature l] Japanese Patent Laid-open publication No. 2000-213326 [Patent Literature 2] Japanese Patent Laid-open publication No. 2004-11436 [Disclosure of the Invention] [Problems to be solved by the Invention] [0004] However, when the oil temperature sensor is attached to the cylinder block, the body of the temperature sensor protrudes from the bottom of the cylinder block toward the ground. Accordingly, it is necessary to attach a protection member to protect this oil temperature sensor from hitting pebbles bouncing and road bumps during running of the vehicle, which increases the weight and mars the external appearance. Moreover, these methods require machining to provide the oil passages used for detecting the oil temperature within the cylinder head or the cylinder block, which increases manufacturing cost. [0005] The present invention was made in the light of the aforementioned problems, and an object of the present invention is to provide an oil temperature detection structure of a two-wheeled motor vehicle engine in which lubricating oil returned from a cylinder head collects in an oil pool integrally formed in a crankcase for measurement of oil temperature. [Means for Solving Problem] [0006] In order to solve the aforementioned problems, an oil temperature detection structure of a two-wheeled motor vehicle engine according to the present invention is to measure temperature of lubricating oil lubricating an engine. Herein, the engine includes a cylinder head, a cylinder block, and a crankcase and is attached to a two-wheeled motor vehicle with a cylinder (for example, a cylinder chamber 7 in an embodiment) extending substantially horizontally to the ground, the cylinder being provided for the cylinder block. The oil temperature detection structure includes: an oil pool in which the lubricating oil returned from the cylinder head collects, the oil pool being integrally formed with the crankcase in front bottom part of the crankcase; and an oil temperature sensor attached to the crankcase and measuring the temperature of the lubricating oil having collected in the oil pool. [0007] Preferably, a cover portion is integrally formed so as to protrude from the crankcase, and a portion of the oil temperature sensor, which is attached to the crankcase, protruding from the crankcase is covered with the cover portion. [Effect of the Invention] [0008] When the oil temperature detection structure of the two-wheeled motor vehicle according to the present invention is thus structured, the lubricating oil having lubricated the cylinder head collects in the oil pool in the crankcase through the cylinder and is not mixed with lubricating oil returned from the other part. Accordingly, measuring the temperature of the lubricating oil having collected in this oil pool allows oil temperature of the cylinder head to be detected. Moreover, the oil pool is integrally formed with the crankcase, and this eliminates the need for machining and suppresses an increase in manufacturing cost. [0009] Moreover, the portion of the oil temperature sensor protruding is covered with the cover portion integrally formed with the crankcase. Accordingly, the oil temperature sensor cannot be damaged by hitting pebbles bouncing and road bumps during running of the vehicle. This cover portion is also integrally formed with the crankcase, and a separate component is not necessary to be provided. It is therefore possible to provide a good external appearance and reduce the manufacturing cost. [Best Mode for Carrying out the Invention] [0010] Hereinafter, a description is given of a preferable embodiment of the present invention with reference to the drawings. First, a description is given of an air-cooling internal combustion engine (engine 1) mounted on a two-wheeled motor vehicle using FIGS. 1 to 5. The engine 1 includes a cylinder head cover 2, a cylinder head 3, a cylinder block 4, and a crankcase 5. This engine 1 is mounted on the two-wheeled motor vehicle with the cylinder head 3 extending forward, and in the following description, the direction indicated by an arrow U of FIG. 1 is upward, and the direction indicated by an arrow F is forward. [0011] A cylindrical cylinder sleeve 6 is fitted in the cylinder block 4, and a piston 8 is provided in a cylinder chamber 7, which is formed by being surrounded by this cylinder sleeve 6, so as to slide within the cylinder chamber 7. This piston 8 is connected to a crankshaft 10, which is rotatably supported within the crankcase 5, through a connecting rod 9. A combustion chamber 11 is formed by being surrounded by the cylinder sleeve 6, cylinder head 3, and piston 8. [0012] Within the cylinder head 3, two intake ports (first and second intake ports 12 and 13) and two exhaust ports (first and second exhaust ports 14a and 14b) are formed. The first and second intake ports 12 and 13 extend upward within the cylinder head 3. One end of the first intake port 12 communicates with the combustion chamber 11 at a first inlet 15, and the other end communicates with the outside at a first intake connection opening 19, which is formed in upper part. One end of the second intake port 13 communicates with the combustion chamber 11 at a second inlet 16, and the other end communicates with the outside at a second intake connection opening 20, which is formed in upper part. As described above, the first and second intake ports 12 and 13 are independently formed within the cylinder head 3 and formed so as to be positioned horizontally side by side in the front view. On the other hand, the exhaust port 14 is divided on one side to be formed into a Y shape and extended downward within the cylinder head 3. On the same side, the first exhaust port 14a communicates with the combustion chamber 11 at a first outlet 17, and the second exhaust port 14b communicates with the combustion chamber 11 at a second outlet 18. The other end of the exhaust port 14 communicates with the outside at an exhaust connection opening 21. [0013] The cylinder head 3 includes mushroom-shaped first and second intake valves 22 and 23 and mushroom-shaped first and second exhaust valves 24 and 25. These valves 22 to 25 are always energized by valve springs 26 to 29 (the valve spring 29 corresponding to the second exhaust valve 25 is not shown) in such directions that the first and second inlets 15 and 16 and first and second outlets 17 and 18 are closed, respectively. One end of each of the valve springs 26 to 29 is attached to a valve shaft and supported by a retainer, and the other end thereof is supported by the cylinder head 3. [0014] Furthermore, in the cylinder head 3, a cam shaft 30, which causes the first and second intake valves 22 and 23 and first and second exhaust valves 24 and 25 to perform opening and closing operations, is rotatably supported, and rotation of the crankshaft 10 is transmitted through a not- shown chain mechanism (timing chain) to the cam shaft 30. In this cam shaft 30, cams 31 corresponding to the first and second intake valves 22 and 23 and first and second exhaust valves 24 and 25 are formed. These cams 31 press up rocker arms 32 to press down the corresponding valves 22 to 25 and open and close the first and second inlets 15 and 16 and first and second outlets 17 and 18. [0015] To the first and second intake connection openings 19 and 20 of the first and second intake ports 12 and 13, an inlet pipe 33 is attached, and furthermore, a carburetor 34 is attached thereto through the inlet pipe 33. Within the inlet pipe 33, a passage is formed. This passage is composed of an intake side passage 33a communicating with the carburetor 34 and first and second passages 33b and 33c, into which the intake side passage 33a is divided toward the cylinder head 3. The first and second passages 33b and 33c are connected to the first and second intake connection openings 19 and 20, respectively. Air supplied from the carburetor 34 is therefore divided from the intake side passage 33a into the first and second passages 33b and 33c and passes through these first and second passages 33b and 33c to be supplied from the first and second inlets 15 and 16 to the combustion chamber 11. [0016] In the middle of the first passage 33b of the inlet pipe 33, a swirl control valve (hereinafter, abbreviated to SCV) 35, which opens and closes the first passage 33b, is provided. This SCV 35 is configured to be closed at low load operation of the engine 1 to supply air (gas mixture) from the second passage 33c (inlet 16) and create swirls within the combustion chamber 11. [0017] As shown in FIG. 5, an injector 46 is attached to bottom part of the inlet pipe 33 and is configured so that fuel is formed into particles (pulverized) to be sprayed to air flowing from the second passage 33c to the second intake port 13 and is supplied to the combustion chamber 11 as gas mixture. In other word, since fuel is supplied as gas mixture from the second intake port 13, which always supplies air, spraying performance of the injector 46 can be ensured. [0018] Next, using FIG. 6, a description is given of an SCV opening/closing mechanism 60, which opens and closes the SCV 35. The SCV 35 is composed of a rotary valve and includes a valve member 35a, which opens and closes the first passage 33b, and an arm member 35b, which is operated in conjunction with the valve member 35a. The SCV 35 is configured to rotate the arm member 35b to perform the opening and closing operations of the valve member 35a. The arm member 35b is connected to a diaphragm 37 through a link member 36. Within the diaphragm 37, an action chamber 37a is formed. The action chamber 37a is connected to a switching valve 39 through the first intake passage 38. The SCV 35 is composed of the rotary valve in this description but can be composed of a butterfly valve as shown in FIGS. 1 and 9. [0019] On the other hand, in a top end portion of the second passage 33c of the inlet pipe 33 (in the vicinity of the second intake connection opening 20), a ventilation pipe 40 communicating with the outside is provided. This ventilation pipe 40 is connected to a vacuum tank 42 through a second intake passage 41. Between the second intake passage 41 and the vacuum tank 42, a check valve 43 is provided so that air does not flow from the vacuum tank 42 into the second passage 33c. This vacuum tank 42 is connected to the switching valve 39 through a third intake passage 44. In such a configuration, when air is supplied to the combustion chamber 11 through the inlet pipe 33, pressure within the second passage 33c is negative with respect to atmospheric pressure, and pressure within the vacuum tank 42 is also negative. [0020] This switching valve 39 is controlled by an engine control unit (ECU)45 to select pressure within the vacuum tank 42 or atmospheric pressure and apply the selected pressure to the action chamber 37a of the diaphragm 37. When determining the engine 1 to be operated at a predetermined load or higher, the ECU 45 switches the switching valve 39 to cause the vacuum tank 42 and the action chamber 37a to communicate with each other and set the pressure within the action chamber 37a to negative pressure. The link member 36 is then pulled to rotate the arm member 35b and open the valve member 35a, thus supplying air from the first passage 33b to the combustion chamber 11. When determining the engine 1 to be operated at a load lower than the predetermined load, the ECU 45 switches the switching valve 39 and sets the pressure within the action chamber 37a to atmospheric pressure. The link member 36 is therefore pushed back by the spring 37b to rotate the arm member 35b and close the valve member 35a. [0021] As described above, negative pressure is taken out through the ventilation pipe 40 from a side of the second passage 33c, which is close to the cylinder head 1. The second passage 33c is always opened. Accordingly, driving force to cause the SCV 35 to perform the opening operation can be ensured, and stable negative pressure can be ensured. [0022] The opening and closing operations of the SCV 35 can be performed in conjunction with the operation of a throttle valve 34 like a SCV opening/closing mechanism 60' shown in FIG. 7. Specifically, a link member 36', which is coupled to the arm member 35b of the SCV 35, is coupled to a throttle of the throttle valve 34. At this time, the link member 36' is coupled so that the link member 36' is not pulled until the opening of the throttle valve 34 reaches a predetermined opening (for example, an opening for intermediate load). Accordingly, when the opening of the throttle valve 34 reaches the predetermined opening or larger, the link member 36' is pulled to rotate the arm member 35b, and the valve member 35a is therefore opened. When the SCV 35 is configured to be opened and closed according to opening and closing of the throttle valve 34 as described above, the operational linkage between the SCV 35 and the throttle valve 34 is enhanced. While the throttle valve 34 has a small opening and the engine 1 is operating at low load, the first passage 33b is closed, and a swirl flow is generated within the combustion chamber 11. [0023] In the engine 1 thus configured, when the SCV 35 is closed, air cleaned by a not-shown air cleaner flows from the throttle valve 34 into the inlet pipe 33 and further flows from the second passage 33c into the second intake port 13 to be gas mixture with fuel mixed. The gas mixture is then supplied to the combustion chamber 11 from the second inlet 16. Within the combustion chamber 11, therefore, a strong oblique swirl flow of the gas mixture is generated to provide an efficient combustion. On the other hand, when the SCV 35 is opened, air flown into the inlet pipe 33 flows from the first and second passages 33b and 33c into the first and second intake ports 12 and 13, respectively, and the combustion chamber 11 is supplied with air from the first inlet 15 and supplied with the gas mixture from the second inlet 16. The air and gas mixture flowing from the first and second inlets 15 and 16 collide with each other to attenuate the swirl flow and also attenuate a tumble flow. It is therefore possible to reduce unnecessary rapid increase in combustion pressure and provide a low-noise driving. [0024] The air and gas mixture supplied to the combustion chamber 11 in the aforementioned manner are compressed by the piston 8 and ignited by a ignition plug 47 for a combustion. The air and gas mixture are thus turned into energy rotating the crankshaft 10 through the piston 8. Thereafter, the air and gas mixture flow through the first and second outlets 17 and 18 to the exhaust port 14 and is discharged to the outside. [0025] In this engine 1, as for the first and second passages 33b and 33c, which are formed in the inlet pipe 33, and the first and second intake ports 12 and 13, which are formed in the cylinder head 3 and connected to the first and second passages 33b and 33c, in a side view, the intake passage composed of the first passage 33b and first intake port 12 is located ahead of the intake passage composed of the second passage 33c and the second intake port 13 in the engine 1 as shown in FIG. 8. As apparent from FIG. 8, an angle formed by the second intake port 13, which is always supplied with air, and the second inlet 16 (a surface on which the first intake valve 23 is seated) is more tilted to the cylinder head 3 side than an angle formed by the first intake port 12, which is connected to the SCV 35, and the first inlet 15 (the valve seat face of the second intake valve 23). The angle of the gas mixture flowing into the combustion engine 11 from the second inlet 16 is smaller than the angle of the gas mixture flowing into the combustion chamber 11 from the first inlet 15. Accordingly, a flange shape 13a of the second intake port 13 is formed into a sharp edge to enhance the oblique swirl component of the gas mixture within the combustion chamber 11. On the other hand, a flange shape 12a of the first intake port 12 has a larger curvature radius, which can reduce flow resistance. Accordingly, the gas mixture smoothly flows into the combustion chamber 11 from the first inlet 15, thus increasing intake efficiency. [0026] As described above, the first and second intake ports 12 and 13, which communicate with the first and second inlets 15 and 16, respectively, are independently formed in the cylinder head 3, and air flowing out of the throttle valve 34 is divided into the first and second passages 33b and 33c within the inlet pipe 33. In the light of optimization of the intake passages to the combustion chamber 11, flexibility in arrangement of the first and second intake ports 12 and 13 can be increased, and a space of peripheral these ports 12 and 13 can be reduced for miniaturization of the cylinder head 3. Moreover, the first and second intake ports 12 and 13, which are connected to the first and second inlets 15 and 16, are separated not within the cylinder head 3 but within the inlet pipe 33. Accordingly, a length of the pipe corresponding to a separated portion of each intake port can be made longer than that of the conventional structure. It is therefore possible to reduce variation in a cross-sectional area of each of the first and second intake ports 12 and 13. Moreover, it is possible to design a partial curvature to be larger, and the gas mixture can be therefore smoothly introduced to the combustion chamber 11. [0027] The throttle valve 34 is disposed above and in front of the cylinder head 3, and the first and second passages 33b and 33c of the inlet pipe 33 are attached so as to be bent downward from the front. Accordingly, the first and second passages 33b and 33c include a curve portion 33d. The SCV 35 is attached to a portion of the first passage 33b vertically extending. As indicated by an arrow A of FIG. 8, therefore, air flown out of the throttle valve 34 is deflected to the outer peripheral side of the passage within the curve portion 33d of the inlet pipe 33 (first and second passages 33b and 33c) and, in other words, to the rear side of the two-wheel mobile to which the engine 1 is attached, in the longitudinal direction, and flows into the SCV 35. When the valve member 35a constituting the SCV 35 is rotated in a direction of an arrow B of FIG. 8 to be opened, this valve member 35a is opened so as to connect rear part of the first passage 33b on the throttle valve 34 side with front part of the first passage 33b on the combustion chamber 11 side. Accordingly, the valve member 35a is opened from the side into which air is deflected and flown from the throttle valve 34 to cause air to flow out to the first inlet 15 without preventing the air flow. This can increase the total of air flown rate into the combustion chamber 11 and the swirl ratio. [0028] The shaft of the SCV 35 is placed obliquely to the first intake port 12 and in parallel to the ground level. The shaft of the SCV 35 therefore does not need to penetrate the second passage 33c, through which air is always supplied to the combustion chamber 11, and does not prevent the air flow through the second passage 33c. Accordingly, the diameter of the second passage 33c can be made smaller. Moreover, with such a structure, the durability of the bearing structure can be ensured. [0029] The inlet pipe 33 is connected to the first and second intake connection openings 19 and 20, which are formed in the cylinder head 3; through an insulator 48. In this insulator 48, a first connection passage 48a, which causes the first passage 33b and the first intake port 12 to communicate with each other, and a second connection passage 48b, which causes the second passage 33c and the second intake port 13 to communicate with each other, are formed. The second passage 33c, second intake port 13, and second connection passage 48b are formed to have a same inner diameter as shown in FIG. 2. However, an inner diameter X of the first passage 33b, which is provided with the SCV 35, is formed to be larger than an inner diameter Y of the first intake port 12. Accordingly, the inner diameter of the first connection passage 48a is formed so as to continually change from the inner diameter X of the first passage 33b to the inner diameter Y of the first intake port 12. [0030] The intake passage provided with the SCV 35 is narrowed at the first connection passage 48a of the insulator 48 as described above. Accordingly, the cross-sectional area of the intake passage can be therefore set equivalent to the cross-sectional area of the SCV 35. It is therefore possible to ensure the balance in flow rate when the SCV 35 is opened to supply air from the first and second ports 12 and 13 to the combustion chamber 11. [0031] This engine 1 has an air-cooling structure, and cooling is performed by lubricating oil used for internal lubrication. The lubricating oil having cooled the cylinder head 3 flows from the front to the rear through an oil passage 52, which is formed in bottom part of the cylinder block 4, into the crankcase 5. Within a front bottom portion of the crankcase 5, an oil pool 49 is formed. The lubricating oil having lubricated the cylinder head 3 and flown out temporarily collects in this oil pool 49. When the surface of the oil exceeds the height of the wall forming the oil pool 49, the oil returns to an oil reservoir (not shown) formed in bottom part of the crankcase 5. As apparent from FIG. 1, this oil pool 49 is formed in the front bottom part of the crankcase 5 in the rear of the cylinder block 4. Accordingly, the lubricating oil returned from the cylinder head 3 through the cylinder block 4 can collect in the oil pool 49 without being mixed with the lubricating oil returned from other part within the engine 1. [0032] An oil temperature sensor 50 is attached to this oil pool 49 and measures temperature of the lubricating oil returned from the cylinder head 3 to detect an increase in temperature of the cylinder head 3. As shown in FIG. 1, the oil pool 49 is formed into a U shape in a side view. Accordingly, even when the two-wheeled motor vehicle is tilted during running, the oil pool 49 can hold enough lubricating oil within, and oil temperature can be surely measured. With such a structure of the oil pool 49, the temperature of the lubricating oil returned from the cylinder head 3 can be always stably measured without being influenced by revolutions of the engine 1 and variation in the orientation of the same. Once the temperature of the lubricating oil is raised, the temperature of the lubricating oil is less subject to external factors, such as getting wet, and can be stably measured. [00331 As shown in FIG. 10, this oil temperature sensor 50 is attached so as to extend laterally from the side face of the crankcase 5. Moreover, as shown in FIG. 11, a portion of the oil temperature sensor 50 protruding from the crankcase 5 is configured to be protruded out of the crankcase 5 and covered with a cover portion 51, which is integrally formed with the crankcase 5. By this oil temperature sensor 50 being attached in the aforementioned manner, the oil temperature sensor 50 is placed within an outline of the crankcase 5 in a side view. Accordingly, even by hitting road bumps and the like, the oil temperature sensor 50 is not directly shocked and less subject to damage. Moreover, the oil temperature sensor 50 is surrounded by the cover portion 51, which is integrally formed with the crankcase 5, and can be prevented from directly hitting pebbles bouncing during running of the vehicle. [0034] The oil pool 49 is composed of the wall integrally formed with the crankcase 5. Accordingly, machining is not necessary, and an increase in manufacturing cost can be suppressed. Moreover, the cover portion 51 is integrally formed with the crankcase 5, and a separate component is not required. It is therefore possible to provide good external appearance and suppress the manufacturing cost. [Brief Description of the Drawings] [0035] [FIG. l] FIG. 1 is a right side view showing a cross section around a cylinder head of an engine according to the present invention. [FIG. 2] FIG. 2 is a right side view showing a main portion of a second intake port. [FIG. 3] FIG. 3 is a right side view of the engine. [FIG. 4] FIG. 4 is a front view showing a structure of the cylinder head and an inlet pipe. [FIG. 5] FIG. 5 is a side view showing a structure of the cylinder head and an injector. [FIG. 6] FIG. 6 is a block diagram showing an opening/closing mechanism which opens and closes an SCV by means of negative pressure of the intake port. [FIG. 7] FIG. 7 is a block diagram showing an opening/closing mechanism which opens and closes the SCV in conjunction with a throttle valve. [FIG. 8] FIG. 8 is a side view showing arrangement of first and second passages and first and second intake ports formed in the inlet pipe. [FIG. 9] FIG. 9 is a side view showing a structure of an insulator provided at a junction of the cylinder head and the inlet pipe. [FIG. 10] FIG. 10 is a cross-sectional view in the vicinity of an oil pool in the crankcase. [FIG. 11] FIG. 11 is a left side view of the engine. [Explanation of the Reference numerals] [0036] 1. ENGINE 3. CYLINDER HEAD 4. CYLINDER BLOCK 5. CRANKCASE 7. CYLINDER CHAMBER 49. OIL POOL 49A. INLET PORTION 49B. BOTTOM PORTION 50. OIL TEMPERATURE SENSOR 51. COVER PORTION [Document Name] Claims [Claim 1] An oil temperature detection structure of a two-wheeled motor vehicle engine for measuring temperature of lubricating oil which lubricates an engine including a cylinder head, a cylinder block, and a crankcase, the engine being attached to a two-wheeled motor vehicle and having a cylinder, which is provided in the cylinder block so as to be substantially extend horizontally with respect to the ground, the cylinder being provided for the cylinder block, the oil temperature detection structure comprising: an oil pool in which the lubricating oil returned from the cylinder head pools, the oil pool being integrally formed with the crankcase in front bottom part of the crankcase; and an oil temperature sensor attached to the crankcase and measuring the temperature of the lubricating oil having collected in the oil pool. [Claim 2] The oil temperature detection structure of a two-wheeled motor vehicle engine according to claim 1,wherein a cover portion is integrally formed to protrude from the crankcase, and a portion of the oil temperature sensor, attached to the crankcase, protruding from the crankcase, is covered with the cover portion.

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