JP2004218507A - Oil returning structure for four-cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent increase in agitation resistance of oil and deterioration of the oil, while avoiding increase in working man-hours, by effectively utilizing a transmission member traveling passage functioning as a passage returning oil to a crankcase side, in a four cycle engine in which the transmission member traveling passage for housing a transmission member, which is wound around a driving wheel fixed to a crankshaft and a driven wheel fixed to a camshaft, to be capable of traveling is extended between the crankcase and a cylinder head, and a rotating member is housed in an operating chamber disposed between the crankcase and a side cover. <P>SOLUTION: In the crankcase 22, an oil guide part 103 is integrally formed to guide the oil dropping from the transmission member traveling passage 85 to the operating chamber 43, so that the oil guide part 103 covers an outer periphery at least on a transmission member traveling passage side of the rotating member. An oil returning passage 104 is disposed to guide the oil guided by the oil guide part 103 into the crankcase 22. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention accommodates a drive wheel fixed to a crankshaft and an endless transmission member wound around a driven wheel fixed to a camshaft in a working chamber formed between a crankcase and a side cover so as to be capable of running. A four-stroke engine in which a transmission member travel passage functioning as a passage for returning oil from the cylinder head to the crankcase side is provided between the crankcase and the cylinder head, and a rotating member driven by a crankshaft is housed in the working chamber. More particularly, the present invention relates to an improvement in an oil return structure for returning oil flowing down in a transmission member traveling passage to a crankcase side.
[0002]
[Prior art]
A cam chain travel passage that houses a cam chain for transmitting power from the crankshaft to the cam shaft so as to be able to travel is provided between the crankcase and the cylinder head, and is provided below the working chamber side opening end of the cam chain travel passage. Patent Document 1 discloses a four-cycle engine in which a located rotor of a generator is fixed to a crankshaft and housed in an operating chamber.
[0003]
[Patent Document 1]
Japanese Patent No. 324064
[0004]
[Problems to be solved by the invention]
In the above-mentioned conventional type, in order to prevent the oil returning from the cam chain traveling passage to the crankcase side from directly abutting on a high-speed rotating body such as a flywheel magneto of a generator, an increase in stirring resistance and deterioration of the oil are prevented. In addition to the cam chain travel passage, an oil return passage is provided from the cylinder head to the crankcase so that oil returning from the oil return passage to the crankcase side does not hit the high-speed rotating body. However, it is necessary to provide an oil return passage separately from the cam chain travel passage, which leads to an increase in the number of processing steps performed on the crankcase, the cylinder block, and the cylinder head.
[0005]
The present invention has been made in view of the above circumstances, and effectively avoids an increase in the number of processing steps by effectively utilizing a transmission member traveling passage that also functions as a passage for returning oil to the crankcase side, while preventing oil stirring. It is an object of the present invention to provide an oil return structure in a four-stroke engine capable of preventing increase and deterioration of oil.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, the crankshaft is provided in a working chamber formed between a crankcase rotatably supporting a crankshaft and a side cover connected to the crankcase. The driven wheel is fixed to the camshaft rotatably supported on the cylinder head, and the driven wheel and the endless transmission member wound around the driving wheel are movably housed therein, and the crankcase is moved from the cylinder head to the crankcase. A transmission member traveling passage that also functions as a passage for returning oil to the side is provided between the crankcase and the cylinder head, and is provided in the working chamber below an opening end of the transmission member traveling passage on the working chamber side. A rotating member driven by the crankshaft can rotate around an axis parallel to the crankshaft. In the four-stroke engine housed in the crankcase, an oil guide portion for guiding oil flowing down from the transmission member traveling passage to the working chamber in the crankcase covers at least an outer periphery of the rotating member on the transmission member traveling passage side. And an oil return passage for guiding oil guided by the oil guide portion into the crankcase is formed.
[0007]
According to the configuration of the first aspect of the present invention, the oil that has flowed down in the transmission member travel passage toward the working chamber is guided by the oil guide portion, so that the oil flows into the crankcase through the oil return passage. As a result, it is possible to minimize contact of the oil flowing down in the transmission member traveling passage with the rotating member in the working chamber, and to prevent an increase in stirring resistance due to the rotating member stirring the oil. In addition to this, it is possible to prevent deterioration due to the oil splashing on the rotating member and to return the oil to the crankcase side by effectively utilizing the transmission member traveling passage, so that the number of processing steps does not increase.
[0008]
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, an upper side of an extension of a lower surface of the transmission member traveling passage inclined with the driven wheel side higher than the drive wheel. The oil guide portion is formed such that the upper end portion is located at the upper end, and one end portion of the transmission member guide disposed in the transmission member traveling passage in sliding contact with the transmission member above the lower surface is provided with the oil guide. According to this configuration, the oil flowing down to the working chamber side along the lower surface of the transmission member traveling passage passes over the oil guide portion and flows to the rotating member side. It can be guided to the oil return passage side while avoiding as much as possible, and the increase in stirring resistance and the deterioration of oil can be more effectively prevented.
[0009]
According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, a lower end of the oil guide portion is formed in the crankcase in an endless manner so as to connect the side cover. A rib integrally formed with the cover coupling wall for receiving oil flowing down from an opening end of the transmission member traveling passage on the working chamber side and forming an oil reservoir communicating with the oil return passage between the transmission case and the crankcase; Is formed integrally with the side cover so as to abut on the oil guide portion when the side cover is joined to the cover joining wall. According to such a configuration, an increase in the number of parts is avoided. While forming a blind hole-shaped oil reservoir between the crankcase and the side cover, returning oil from the transmission member travel passage to the oil reservoir It can be reliably returned to the crankcase through the road.
[0010]
The invention according to claim 4 further includes, in addition to the configuration according to any one of claims 1 to 3, a crankcase disposed on one side of a drive wheel, wherein the crankcase and the drive wheel are disposed between the crankcase and the drive wheel. The arranged side cover is coupled, and a speed change input shaft of the transmission is rotatably supported with an axis parallel to the crankshaft, and the speed change input shaft is provided in an operating chamber between the crankcase and the side cover. At one end of the input shaft, a clutch having a clutch outer as the rotating member is mounted so as to be able to connect / disconnect power transmission between the crankshaft and the speed change input shaft. For example, the oil flowing down in the transmission member travel passage can be prevented from contacting the clutch outer as much as possible. It is possible to dispose the clutch close to the crankshaft side while preventing an increase in agitation resistance due to agitation, so that the power unit including the engine and the transmission can be reduced in size and arranged on one side of the drive wheels. It is possible to suppress the overhang of the power unit from the driving wheels, thereby contributing to the improvement of the vehicle body balance.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described based on an embodiment of the present invention shown in the attached drawings.
[0012]
1 to 7 show an embodiment of the present invention. FIG. 1 is a side view of a motorcycle, FIG. 2 is an enlarged side view of a rear portion of the motorcycle, and FIG. 3 is a line 3-3 in FIG. 4 is a sectional view taken along line 4-4 of FIG. 3, FIG. 5 is a sectional view taken along line 5-5 of FIG. 4, FIG. 6 is a sectional view taken along line 6-6 of FIG. 4, and FIG. FIG. 7 is a sectional view taken along line 7.
[0013]
First, in FIG. 1, a body frame 11 of the scooter type motorcycle includes a front frame 14 connected to a head pipe 13 that supports a front fork 12 so as to be steerable, and a rear end of the front frame 14. And a pair of right and left rear frames 15 extending rearward. A front wheel WF is supported at the lower end of the front fork 12. Further, a step floor 16 is supported on the front frame 14, and a stand 17 capable of standing the vehicle body is attached thereto. A luggage box 18, a passenger seat 19 and a fuel tank 20 are supported on the rear frame 15. You. Further, a power unit P for driving the rear wheel WR while supporting the rear wheel WR, which is a driving wheel, is vertically swingable and supported at the rear end of the front frame 14, and a rear cushion 21 is provided between the rear frame 15 and the power unit P. Is provided.
[0014]
2 to 5, a power unit P is configured by accommodating a crankshaft 23 and a gear transmission T in a crankcase 22 of an engine E that is a single-cylinder four-cycle forced air-cooling system. It is arranged on one side on the left and right, in this embodiment on the right. Thus, the rear wheel WR is attached to a shift output shaft 56 of the gear transmission T.
[0015]
The crankcase 22 disposed on the right side of the rear wheel WR is coupled to the rear of a cylinder block 24 having a cylinder axis C inclined upward and forward. The crankcase 22 is divided by a plurality of bolts 26 along a vertical plane. The left case half 22L and the right case half 22R are connected. A carburetor 28 is connected to an upper surface of a cylinder head 25 connected to a front portion of the cylinder block 24 via an intake pipe 27, and an exhaust pipe 29 connected to a lower surface of the cylinder head 25 is connected to a rear wheel WR. The downstream end of the exhaust pipe 29 is connected to an exhaust muffler 30 which is bent so as to largely detour the front and sandwiches the rear wheel WR with the power unit P.
[0016]
Brackets 31 are fixed to the left and right ends of the rear end of the front frame 14, and a suspension link 32 is swingably connected to these brackets 31 via a horizontal first pivot 33. The suspension link 32 includes one front arm 32a and a pair of left and right rear arms 32b, 32b. The front arm 32a is inserted into the rear end of the front frame 14 via the cushion rubber 34. , Will be supported.
[0017]
On the other hand, the left case half 22L of the crankcase 22 is integrally formed with a hanger arm 35 having a bearing portion 35a disposed between the rear arms 32b, 32b in front of the rear wheel WR. Both ends of a horizontal second pivot shaft 37 that rotatably supports 35a via a pair of left and right rubber bushes 36 are connected to the rear arms 32b, 32b. Accordingly, the crankcase 22, that is, the power unit P can swing up and down around the second pivot 37, and the swinging impact acting on the suspension link 32 from the power unit P is absorbed by the cushion rubber 34.
[0018]
The exhaust muffler 30 is welded to the base end of a muffler stay 41 having bifurcated portions 41a and 41b branched vertically at the distal end side. The bifurcated portions 41a and 41b are bolted to a bearing portion 35a of the hanger arm 35. , 42.
[0019]
A left side cover 44 disposed between the crankcase 22 and the rear wheel WR is joined to the left case half 22L of the crankcase 22 so as to form a working chamber 43 with the left case half 22L. One end of the crankshaft 23 rotatably supported by the left and right case halves 22L, 22R of the crankcase 22 via ball bearings 45, 46 projects into the working chamber 43. The cylinder block 24, the cylinder head 25, and a part of the right case half 22R in the crankcase 22 are covered with a shroud 47, and the crankshaft 23 penetrates the right case half 22R rotatably and liquid-tightly. A rotor 49 of a generator 48 housed in the shroud 47 is fixed to the other end of the generator.
[0020]
A plurality of intake holes 50 are provided in the shroud 47 at portions corresponding to the rotor 49, and a fan 51 for sucking outside air from the intake holes 50, 50 is fixed to the rotor 49. On the outer surfaces of the cylinder block 24 and the cylinder head 25, a plurality of cooling fins 24a,..., 25a, which come into contact with the cooling air flowing through the shroud 47 by the operation of the fan 51, are provided.
[0021]
A piston 53 slidably fitted to a cylinder bore 52 provided in the cylinder block 24 is connected to the crankshaft 23 via a connecting rod 54.
[0022]
The gear transmission T includes a speed change input shaft 55 and a speed change output shaft 56 that are parallel to the crankshaft 23. The speed change input shaft 55 has one end protruding into the working chamber 43 so that the left case A half bearing 22L is rotatably penetrated, and a ball bearing 57 is interposed between the left case half 22L and the speed change input shaft 55. The other end of the speed change input shaft 55 is rotatably supported by the right case half 22R via a ball bearing 58.
[0023]
One end of the transmission output shaft 56 rotatably penetrates the left side cover 44, and a ball bearing 59 and an annular seal member 60 are interposed between the left side cover 44 and the transmission output shaft 56, and protrude from the left side cover 44. The rear wheel WR is attached to one end of the shifted transmission output shaft 56. The other end of the transmission output shaft 56 is rotatably supported by the right case half 22R via a ball bearing 61.
[0024]
Between the one end of the crankshaft 23 and one end of the speed change input shaft 55 in the working chamber 43, a primary speed reducer 62 and a multi-plate mounted on one end of the speed change input shaft 55 so that power transmission can be connected and disconnected. A clutch 63 is interposed. The primary reduction gear 62 includes a drive gear 64 fixed to the crankshaft 23 and a driven gear 65 mounted on the transmission input shaft 55 so as to be relatively rotatable. The multi-plate clutch 63 has a clutch outer 66 connected to the driven gear 65 via a damper 68, and a clutch inner 67 fixed to one end of the shift input shaft 55, and performs a shift in the working chamber 43. It is miniaturized in order to store it in a relatively small space between the output shaft 56 and the crankshaft 23.
[0025]
A plurality of speed change gear trains, for example, four speed change gear trains are provided in the crankcase 22 between the speed change input shaft 55 and the speed change output shaft 56. The driven gears 69, 70, 71, 72 of each transmission gear train are mounted on the transmission output shaft 56 so as to be relatively rotatable.
[0026]
The driven gears 69 to 72 of each of the transmission gear trains are selectively connected to the transmission output shaft 56 by a change mechanism 73 that is mostly disposed outside the right case half 22R in the crankcase 22. The change mechanism 73 is covered with a right side cover 74 coupled to the right case half 22R.
[0027]
The transmission output shaft 56 is coaxially provided with a guide hole 75 opened to the other end, and a plurality of guides extending between the guide hole 75 and the outer surface of the transmission output shaft 56 at the mounting portions of the driven gears 69 to 72. Grooves 76 are provided. The change mechanism 73 includes a shift shaft 77 slidably fitted in the guide hole 75 and an engagement pole 78 fixed to an inner end of the shift shaft 77. Slide in the guide grooves 76 so as to selectively engage with the driven gears 69 to 72.
[0028]
An intake valve (not shown) for controlling intake of an air-fuel mixture from an intake pipe 27 to a combustion chamber 79 formed between the cylinder block 24 and the cylinder head 25 so as to face the piston 53; An exhaust valve (not shown) for controlling exhaust from 79 to the exhaust pipe 29 has a camshaft 80 having an axis parallel to the crankshaft 23 and rotatably supported by the cylinder head 25. A driving sprocket 82 as a driving wheel is fixed to one end of the crankshaft 23 in the working chamber 43 in order to rotationally drive the camshaft 80. A sprocket 83 as an endless transmission member, a driven sprocket 83 as a driven wheel fixed to the It is wound around.
[0029]
The crankcase 22, the cylinder block 24, and the cylinder head 25 are provided with a cam chain passage 85 as a transmission member traveling passage for accommodating the cam chain 84 so that the cam chain 84 can travel. Extend in parallel. That is, since the cylinder axis C is inclined forward, the cam chain passage 85 is also inclined forward with the driven sprocket 83 side higher than the drive sprocket 82.
[0030]
In the cam chain passage 85, a sled-shaped chain tensioner 87 rotatably supported by the left case half 22L on a support shaft 86 disposed above the crankshaft 23 is disposed above the loose cam chain 84. A chain guide 88 serving as a sled-shaped transmission member guide is slid from below on the tension side cam chain 84 so that one end thereof protrudes toward the working chamber 43 side. The part is supported by the cylinder block 24.
[0031]
Referring also to FIG. 6, an inner rotor 91 of an oil pump 90, which is a trochoid pump, is connected to the speed change input shaft 55, and a pump housing 93 of the oil pump 90 is connected to the left case half 22L. To the left case half 22L from the working chamber 43 side so as to sandwich the inner rotor 91 and the outer rotor 92 therebetween.
[0032]
The oil pump 90 pumps oil from the bottom of the crankcase 22. A filter 94 for filtering the oil pumped from the bottom of the crankcase 22 is mounted on the right case half 22R. A suction passage 96 that connects between the filter 94 and a suction port 95 of the oil pump 90 is provided in the 22R and the left case half 22L. In addition, a communication path 97 that guides the oil returned to the working chamber 43 to a lower part in the crankcase 22 is provided in a lower part of the left case half 22L.
[0033]
7, a discharge passage 99 communicating with the discharge port 98 of the oil pump 90 is provided in the left case half 22L and the right case half 22R, and the downstream end of the discharge passage 99 is connected to the right case half. It is communicated with one end of an oil groove 100 formed on the surface of the 22R that is connected to the cylinder block 24. Further, one of a plurality of through bolts 101 connecting the cylinder head 25, the cylinder block 24 and the right case half 22R, and an oil passage 102 communicating between the cylinder block 24 and the cylinder head 25 to the other end of the oil groove 100 are provided. The oil formed and discharged from the oil pump 90 is supplied to the cylinder head 25 side through the discharge passage 99, the oil groove 100, and the oil passage 102, and the lubricating portion of the valve gear 81 provided in the cylinder head 25 is provided. Is led to the oil.
[0034]
The oil used for lubricating the valve gear 81 is returned to the working chamber 43 through the cam chain passage 85. The cam chain passage 85 accommodates the cam chain 84 so as to be able to travel and a cylinder. It also functions as a passage for returning oil from the head 25 to the crankcase 22 side.
[0035]
In the working chamber 43 below the opening end of the cam chain passage 85 on the working chamber 43 side, a driven gear 65 as a rotating member driven by the crankshaft 23 and a clutch outer 66 are arranged. An oil guide portion 103 that guides oil flowing down from the cam chain passage 85 to the working chamber 43 in the left case half 22L of the 22 so as to cover at least the outer periphery of the driven gear 65 and the clutch outer 66 on the cam chain passage 85 side. And an oil return passage 104 that guides the oil guided by the oil guide portion 103 into the crankcase 22.
[0036]
Moreover, the oil guide portion 103 is formed so that its upper end is located above the extension line L of the lower surface 85a of the cam chain passage 85, and slides on the cam chain 84 above the lower surface 85a. One end of the cam chain guide 88 disposed in the cam chain passage 85 is held at the upper end of the oil guide 103. That is, the upper end of the oil guide portion 103 is formed in a substantially J-shape. When the upper end of the oil guide portion 103 is inserted into one end of the cam chain guide 88, one end of the cam chain guide 88 is Will be held at the upper end.
[0037]
The lower end of the oil guide portion 103 is endlessly connected to the left side cover 44 and is integrally connected to a cover connecting wall 105 formed in the left case half 22L of the crankcase 22. A rib 107 for receiving oil flowing down from the opening end on the side of the working chamber 43 and forming an oil sump 106 communicating with the oil return passage 104 with the left case half 22L is provided on the cover connecting wall 105. The left side cover 44 is formed integrally with the left side cover 44 so as to come into contact with the oil guide portion 103 when the left side cover 44 is connected.
[0038]
Next, the operation of this embodiment will be described. An oil guide portion 103 for guiding oil flowing down from the cam chain passage 85 to the working chamber 43 is provided in the left case half 22L of the crankcase 22 with a driven gear in the primary reduction gear 62. The oil guide 65 is formed integrally so as to cover at least the outer periphery of the clutch outer 66 of the multi-plate clutch 63 on the cam chain passage 85 side, and guides oil guided by the oil guide portion 103 into the crankcase 22. Since the return passage 104 is formed, the oil that has flowed down in the cam chain passage 85 toward the working chamber 43 is returned to the crankcase 22 via the oil return passage 104 by being guided by the oil guide portion 103. Will be. Therefore, it is possible to minimize contact of the oil flowing down in the cam chain passage 85 with the driven gear 65 and the clutch outer 66 in the working chamber 43, and the driven gear 65 and the clutch outer 66 stir the oil. In addition, it is possible to prevent the agitation resistance from increasing, and to prevent the oil from hitting the driven gear 65 and the clutch outer 66 and being scattered, thereby preventing deterioration. In addition, since the oil is returned to the crankcase 22 side by effectively utilizing the cam chain passage 85, the number of processing steps does not increase.
[0039]
The cam chain passage 85 is inclined with the driven sprocket 83 side higher than the driving sprocket 82. The upper end of the oil guide portion 103 is located above the extension L of the lower surface 85 a of the cam chain passage 85. One end of a cam chain guide 88 disposed in the cam chain passage 85 in sliding contact with the cam chain 84 above the lower surface 85a is held at the upper end of the oil guide portion 103. . Therefore, the oil flowing down to the working chamber 43 side along the lower surface of the cam chain passage 85 is prevented from flowing over the oil guide portion 103 to the driven gear 65 and the clutch outer 66 side as much as possible and guided to the oil return passage 104 side. Therefore, it is possible to more effectively prevent an increase in stirring resistance and deterioration of oil.
[0040]
The lower end of the oil guide portion 103 is endlessly connected to the left side cover 44 and connected integrally to a cover connecting wall 105 formed on the left case half 22L. A rib 107 for receiving the oil flowing down from the opening end on the 43 side and forming an oil sump 106 communicating with the oil return passage 104 between the left case half 22L and the left side cover 44 to the cover coupling wall 105 is provided. Since the oil reservoir 106 is formed integrally with the left side cover 44 so as to abut on the oil guide portion 103 at the time of coupling, the oil reservoir 106 having a bag-hole shape can be formed into the left case half 22L and the left side cover 44 while avoiding an increase in the number of parts. Oil from the cam chain passage 85 from the oil sump 106 to the crankcase through the oil return passage 104. It can be reliably returned to the 22.
[0041]
Further, a left side cover 44 disposed between the crankcase 22 and the rear wheel WR is coupled to the crankcase 22 disposed on the right side of the rear wheel WR, and a shift input shaft 55 of the gear transmission T is connected to a crankshaft. A multi-plate clutch 63 is provided at one end of the speed change input shaft 55 in the working chamber 43 between the crankcase 22 and the left side cover 44, with a multi-plate clutch 63. The power transmission between the transmission 23 and the speed change input shaft 55 can be connected and disconnected. According to such a configuration, it is possible to prevent the oil flowing down in the cam chain passage 85 from contacting the clutch outer 66 of the multi-plate clutch 63 as much as possible, so that the clutch outer 66 agitates the oil. The multi-plate clutch 63 can be arranged close to the crankshaft 23 while preventing an increase in stirring resistance, so that the power unit P including the engine E and the transmission T can be reduced in size, and the rear wheel WR The overhang from the rear wheel WR of the power unit P disposed on the right side can be suppressed, which can contribute to the improvement of the vehicle body balance.
[0042]
In addition, in this embodiment, since the size is reduced to be accommodated in a relatively small space between the transmission output shaft 56 and the crankshaft 23 in the working chamber 43, the multi-plate clutch 63 rotates at a high speed. Since the clutch outer 66 can be prevented from contacting the oil flowing down in the cam chain passage 85 as much as possible, the stirring resistance of the high-speed clutch outer 66 does not increase due to the contact with the oil.
[0043]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.
[0044]
For example, in the above-described embodiment, the case where the cam chain 84 is used as the transmission member has been described. However, the present invention can be applied to a four-cycle engine in which an endless timing belt is used as the transmission member.
[0045]
【The invention's effect】
As described above, according to the first aspect of the present invention, it is possible to prevent the rotation member from increasing the stirring resistance due to the stirring of the oil, and to prevent the deterioration due to the oil scattering on the rotation member. It is possible, and the number of processing steps does not increase.
[0046]
According to the second aspect of the invention, the oil flowing down to the working chamber along the lower surface of the transmission member traveling passage is prevented from flowing over the oil guide portion and flowing toward the rotating member as much as possible, thereby reducing the stirring resistance. Increase and deterioration of oil can be prevented more effectively.
[0047]
According to the third aspect of the invention, a blind hole-shaped oil reservoir is formed between the crankcase and the side cover while avoiding an increase in the number of parts, and the oil from the transmission member travel passage is transferred from the oil reservoir to the oil return passage. Through the crankcase.
[0048]
Further, according to the fourth aspect of the present invention, it is possible to dispose the clutch close to the crankshaft while preventing an increase in stirring resistance due to the clutch outer stirring oil, and the power unit including the engine and the transmission Of the power unit disposed on one side of the drive wheel can be suppressed from protruding from the drive wheel, thereby contributing to an improvement in vehicle body balance.
[Brief description of the drawings]
FIG. 1 is a side view of a motorcycle.
FIG. 2 is an enlarged side view of a rear portion of the motorcycle.
FIG. 3 is a view taken along line 3-3 of FIG. 2;
FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;
FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;
FIG. 6 is a sectional view taken along line 6-6 of FIG. 4;
FIG. 7 is a sectional view taken along line 7-7 of FIG. 4;
[Explanation of symbols]
22 ... Crankcase
23 ・ ・ ・ Crankshaft
25 ... Cylinder head
43 ・ ・ ・ Working chamber
44 ・ ・ ・ Side cover
55 ... speed change input shaft
63 ・ ・ ・ Clutch
65: Driven gear as rotating member
66 Clutch outer as rotating member
80 ... camshaft
82 ... Driving sprocket as driving wheel
83: Driven sprocket as driven wheel
84 ··· Cam chain as transmission member
85: Cam chain passage as transmission member traveling passage
85a: Lower surface of cam chain passage
88 ··· Cam chain guide as transmission member guide
103 ・ ・ ・ Oil guide part
104 ・ ・ ・ Oil return passage
105 ・ ・ ・ Cover connection wall
106 ・ ・ ・ Oil pool
107 ... rib
E: Engine
L: Extension line
T: transmission
WR: Rear wheel as drive wheel

Claims (4)

The crankshaft is disposed within a working chamber (43) formed between a crankcase (22) rotatably supporting a crankshaft (23) and a side cover (44) coupled to the crankcase (22). A drive wheel (82) is fixed to (23), and is wound around a driven wheel (83) fixed to a camshaft (80) rotatably supported on a cylinder head (25) and the drive wheel (82). A transmission member travel passage (85) that houses the endless transmission member (84) so as to be able to travel and also functions as a passage for returning oil from the cylinder head (25) to the crankcase (22) side is provided in the crankcase ( 22) and the cylinder head (25), below the opening end of the transmission member travel passage (85) on the working chamber (43) side. In the four-stroke engine, a rotating member (65, 66) driven by the crankshaft (23) is accommodated in the working chamber (43) so as to be rotatable around an axis parallel to the crankshaft (23). An oil guide portion (103) for guiding oil flowing down from the transmission member travel passage (85) to the working chamber (43) is provided in the crankcase (22) at least for the transmission of the rotating members (65, 66). An oil return passage (104) is formed integrally to cover the outer periphery on the member traveling passage (85) side and guides oil guided by the oil guide portion (103) into the crankcase (22). Oil return structure in a four-stroke engine. The upper end portion is located above an extension (L) of the lower surface (85a) of the transmission member travel passageway (85) which is inclined with the driven wheel (83) side higher than the drive wheel (82). A transmission member guide (88) disposed in the transmission member traveling passage (85) in sliding contact with the transmission member (84) above the lower surface (85a). The oil return structure for a four-stroke engine according to claim 1, wherein one end of the oil return portion is held at an upper end of the oil guide portion (103). The lower end of the oil guide portion (103) is connected to the cover connecting wall (105) formed on the crankcase (22) in an endless manner so as to connect the side cover (44). An oil sump (106) communicating with the oil return passage (104) is formed between the transmission case travel passage (85) and the crankcase (22) while receiving oil flowing down from an opening end of the transmission member traveling passage (85) on the working chamber (43) side. Rib (107) is formed integrally with the side cover (44) so as to abut the oil guide portion (103) when the side cover (44) is coupled to the cover coupling wall (105). 3. The oil return structure in a four-stroke engine according to claim 1, wherein the oil is returned. The crankcase (22) arranged on one side of the drive wheel (WR) is coupled with the side cover (44) arranged between the crankcase (22) and the drive wheel (WR). A transmission input shaft (55) of the machine (T) is rotatably supported with an axis parallel to the crankshaft (23), and an operating chamber (5) between the crankcase (22) and the side cover (44). 43), a clutch (63) having a clutch outer (66) as the rotating member is provided at one end of the shift input shaft (55) between the crankshaft (23) and the shift input shaft (55). The oil return structure for a four-stroke engine according to any one of claims 1 to 3, wherein the oil return structure is mounted so as to be able to connect and disconnect the power transmission.

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