JP6438812B2 - Gearbox for internal combustion engine - Google Patents

Description

  The present invention relates to a transmission for an internal combustion engine in which a lubrication state between a gear group of a transmission and a shift fork is improved.

  In general, an engine such as a motorcycle is often provided with a constantly meshing transmission. The transmission includes a main shaft to which a rotational driving force from an engine crankshaft is transmitted via a clutch, a counter shaft for transmitting a rotational driving force transmitted from the main shaft to driving wheels, a main shaft and a countershaft. And a gear group provided in the.

The gear group includes a shifter that rotates integrally with the support shaft (main shaft or counter shaft) and is movable in the axial direction. The shifter has a fork groove with which the shift fork is engaged.
A dog clutch is provided between the shifter and the gear adjacent to the shifter to connect or disconnect the shifter and the gear adjacent to the shifter. When the shift fork moves the shifter in the axial direction, the dog clutch provided between the shifter and the gear adjacent to the shifter is connected or disconnected to change the gear position of the transmission.

  In such a transmission, oil for lubrication and cooling is supplied in order to prevent wear and seizure of members.

  For example, in Patent Document 1, oil is injected from the front lower side of a drive shaft (counter shaft) into a portion where a shift fork and a sliding groove (fork groove) of a gear rub against each other when a dog clutch (dog clutch) is disengaged. An engine multi-stage transmission is disclosed in which an oil injection hole is provided in a crankcase to improve a lubrication state between a shift fork and a sliding groove.

  Further, in Patent Document 2, a rib formed on the upper wall portion of the clutch chamber captures the oil scattered in the clutch chamber, and the captured oil is disposed above the necessary portion of the oil-supplied member (second clutch). An oil supply structure for dripping from an oil is disclosed.

JP-A-8-61468 JP, 2011-214610, A FIG. 8, FIG.

  In the invention disclosed in Patent Document 1, not only is it necessary to provide an oil passage for the oil injection hole in the crankcase, but it is also necessary to form the oil injection hole at an accurate position. Therefore, the structure for supplying oil to the fork groove becomes complicated, and there is a problem that the number of manufacturing steps and the manufacturing cost of the crankcase increase.

  On the other hand, it is conceivable to simplify the structure by applying the structure disclosed in Patent Document 2 to oil supply to the fork groove of the shift gear. However, in that case, unlike the upper wall portion of the clutch chamber (that is, the right case cover), the oil drops at a pin point from the upper wall portion of the crankcase formed into a relatively complicated shape to the fork groove is realized. Therefore, the structure disclosed in Patent Document 2 is not sufficient.

  That is, simply forming the ribs causes the oil captured by the ribs to be concentrated and dripped at the bottom of the ribs. Therefore, in a crankcase that is molded into a relatively complex shape, if the shape (height) of the rib is deformed and the lowermost position is not aligned above the fork groove, the oil captured by the rib is removed from the fork groove. It cannot be dripped at a pinpoint. Moreover, when it is going to form the front-and-back overhang | projection part currently disclosed by patent document 2 in a rib, it is not easy in terms of die cutting of a crankcase, or a process.

  The present invention solves the above-described problems, and an object of the present invention is to supply oil to a fork groove formed in a shifter with a simple configuration and improve the lubrication between the fork groove and the shift fork. Is to provide.

In order to solve the above problems, a transmission for an internal combustion engine according to the present invention includes a main shaft, a counter shaft disposed in parallel with the main shaft, a gear group provided on the main shaft and the counter shaft, A shift fork that shifts the gear group, a shift fork shaft that supports the shift fork so as to be movable in an axial direction, a transmission case that houses the main shaft, the counter shaft, the gear group, and the shift fork, A shift drum fitted with a shift fork and moving the shift fork in the axial direction,
A part of the gear group is formed as a shifter that rotates integrally with a shaft and is movable in the axial direction. The shifter is formed with a fork groove that engages with the shift fork. In a transmission of an internal combustion engine provided with a dog clutch that connects or disengages the shifter and the gear adjacent to the shifter between the gears adjacent to the shifter,
The shift drum and the shift fork shaft are disposed below the main shaft and the counter shaft, and a part of the inner wall surface of the upper wall portion of the transmission case protrudes downward, and as viewed from above. , Formed as oblique ribs oriented in an oblique direction with respect to the axial direction of the main shaft or the counter shaft, and a plurality of the oblique ribs are formed, and the oblique ribs are at least of the main shaft and the counter shaft. There is an intersecting portion that is crossed above either one, and the intersecting portion is formed long in the axial direction of the shift fork shaft, and when viewed from above, the fork groove in the neutral state of the dog clutch is defined as the shift fork shaft. the spanning in the axial direction, the the intersections, the first projection portion projecting downward from the inner wall surface of the upper wall portion is a plurality of locations forming, double The first protrusions are arranged on both sides of the intersecting part, in the axial direction of the shift fork shaft, with respect to the position of the fork groove in the neutral state of the dog clutch. Are arranged at one or more positions at positions overlapping with the fork grooves in the connected state of each of the dog clutches when viewed from above .

  According to such a configuration, the oil attached to the inner wall surface of the upper wall of the transmission case due to splashing from the oil pan during traveling or scattering from the gear group due to the centrifugal force, It will gather at the first protrusion by the action of gravity. The oil collected in the first protrusion is dropped from the first protrusion into the fork groove located below the first protrusion in the dog clutch connected state. Therefore, it is possible to supply oil to the fork groove of the shifter when the dog clutch is connected with a simple configuration in which a protrusion is provided on the transmission case, and without increasing the manufacturing cost of the transmission case, the fork groove And the lubrication between the shift forks can be improved.

  In the above configuration, a part of the inner wall surface of the upper wall portion of the transmission case protrudes downward and is oblique to the axial direction of the main shaft or the counter shaft when viewed from above The first protrusion may be formed on the oblique rib.

According to such a structure, the oil adhering to the inner wall surface of the upper wall of the transmission case can be collected over a wide range by the oblique rib. The oil collected in the oblique ribs gathers in the first protrusion that protrudes downward from the oblique ribs along the oblique ribs. The oil collected in the first protrusion is dropped from the first protrusion into the fork groove located below the first protrusion in the dog clutch connected state. Therefore, it is possible to improve the lubrication between the fork groove and the shift fork by supplying oil to the fork groove in the connected state of the dog clutch with a simple configuration that does not particularly change the shape of the oblique rib.
In addition, by forming diagonal ribs in an oblique direction with respect to the axial direction of the main shaft and the counter shaft, the rigidity of the upper wall portion of the transmission case is improved, and the noise of the transmission case during a shift operation is reduced. be able to.

  In the above configuration, a plurality of the oblique ribs may be formed, and the oblique ribs may be disposed so as to intersect above at least one of the main shaft and the counter shaft.

  According to such a structure, the oil adhering to the inner wall surface of the upper wall of the transmission case can be collected over a wider range by the plurality of oblique ribs. The oil collected in the plurality of oblique ribs gathers not only at the protrusions but also at the intersecting portions along the ribs. The oil collected at the intersecting portion is dropped from at the intersecting portion onto at least one of the main shaft and the counter shaft. Therefore, oil can be supplied also to at least one of the main shaft and the counter shaft and the gear group with a simple configuration in which a plurality of oblique ribs intersect.

  The said structure WHEREIN: You may form said 1st projection part in the cross | intersection part where the said diagonal rib cross | intersects.

  According to such a configuration, the oil collected at the intersection from the plurality of oblique ribs is collected at the first protrusion formed at the intersection. And it is dripped from the 1st protrusion part to the fork groove located under an intersection part in the connection state of a dog clutch. Therefore, it is possible to efficiently supply oil to the fork groove of the shifter with the dog clutch connected with a simple configuration, and lubrication between the fork groove and the shift fork can be performed without increasing the manufacturing cost of the transmission case. Can be improved.

  The said structure WHEREIN: You may form two or more said 1st projection parts along the axial direction of the said main axis | shaft and the said counter axis | shaft.

  According to such a configuration, the oil adhering to the inner wall surface of the upper wall of the transmission case is dripped into the fork groove located below the first protrusion in the engaged state of the plurality of dog clutches. Therefore, oil can be supplied to the fork grooves at a plurality of locations with a simple configuration, and lubrication between the fork grooves and the shift forks can be improved.

  The said structure WHEREIN: A said 1st projection part may be located on the rotating shaft line of the said shifter by upper view.

  According to such a configuration, the oil attached to the inner wall surface of the upper wall portion of the transmission case is dripped from the first projection portion into the fork groove on the rotation axis. This oil flows in the fork groove along the circumferential direction of the shifter in two directions, ie, the rotation direction of the shifter and the reverse rotation direction, so that the oil can be efficiently spread in the fork groove. Further, even if the oil dropping position is shifted due to vibration or inertia, the oil is likely to be dropped into the fork groove.

  The said structure WHEREIN: While the said cross | intersection part is formed in three or more places, you may be located above each of the said main axis | shaft and the said counter axis | shaft.

  According to such a configuration, the oil adhering to the inner wall surface of the upper wall portion of the transmission case is dripped into both the shifter fork groove provided on the main shaft and the shifter fork groove provided on the counter shaft. The Therefore, even if either the main shaft or the counter shaft is operating at a high speed, oil can be reliably supplied to the fork groove of the shifter, and lubrication between the fork groove and the shift fork can be improved. .

  The said structure WHEREIN: The said inner wall surface of the said upper wall part of the said transmission case may incline with respect to a horizontal surface.

  According to such a configuration, the oil attached to the inner wall surface of the upper wall portion of the transmission case flows along the inclination. For this reason, the efficiency of oil collection at the protrusions and ribs located in the middle of the oil flow is improved, and the amount of oil dripping from the protrusions is increased. As a result, lubrication between the fork groove and the shift fork can be improved.

  A part of the inner wall surface of the upper wall portion of the transmission case protrudes downward and is formed as a parallel rib directed in a direction parallel to the axial direction of the main shaft. It may be located between the main shaft and the counter shaft when viewed from above.

  According to such a configuration, the oil adhering to the inner wall surface of the upper wall portion of the transmission case also collects on the parallel ribs. The oil collected on the parallel ribs is dropped between the main shaft and the counter shaft. A gear group is provided between the main shaft and the counter shaft, and a meshing portion of the gear is located. Therefore, oil can be supplied to a gear group provided between the main shaft and the counter shaft with a simple configuration in which parallel ribs are formed.

  A second protrusion that protrudes downward from the parallel rib is formed on the parallel rib, and the second protrusion is located in a region where the teeth of the gear group are formed as viewed from above. May be.

  According to such a configuration, the oil adhering to the upper wall portion of the transmission case gathers along the parallel ribs and gathers at the second protrusion, and is dropped onto the teeth of the gear group located below the second protrusion. The Therefore, oil can be supplied to the gear group with a simple configuration, and the meshing lubrication of the gear group can be improved.

  The shift fork is provided with a fork rib that protrudes in the axial direction of the shift fork shaft, and the fork rib is disposed below the gear in the radial direction adjacent to the side of the shift fork where the fork rib protrudes. It may be curved along the tooth tip circle.

According to such a configuration, the oil dropped from the protrusion of the upper wall portion of the transmission case, the intersecting portion of the oblique ribs, or the oil attached to the tooth surface of the gear adjacent to the side where the fork rib protrudes Are captured by the fork ribs and gather at the curved portions of the fork ribs. The collected oil comes into contact with the tooth tips of the gear and lubricates the gear and its meshing portion. In addition, the collected oil is splashed up to the tooth tip of the gear to adhere to the upper wall portion of the transmission case, and a part of the oil is supplied to the fork groove of the shift gear along the shift fork. Therefore, the lubrication between the gear adjacent to the shift fork and its meshing portion and the fork groove with which the shift fork is engaged can be improved only by changing the shape of the shift fork.
In addition, the rigidity of the shift fork can be enhanced.

  According to the transmission of the internal combustion engine according to the present invention, it is possible to supply oil with a simple configuration in which a protrusion is provided on the transmission case in the fork groove of the shift gear when the dog clutch is connected. Lubrication between the fork groove and the shift fork can be improved without increasing the manufacturing cost of the case.

1 is a left side view of a motorcycle equipped with a transmission for an internal combustion engine according to the present invention as viewed from the left side. It is the left view which expanded the internal combustion engine part of FIG. It is the III-III sectional view taken on the line of FIG. It is the expanded sectional view which expanded the transmission of FIG. It is the bottom view which expanded the upper transmission case half part part among the upper unit case half parts, and was seen from the downward direction. In the drawing, a two-dot chain line indicates a region where the teeth of each gear are formed. FIG. 4 is a VI arrow view of a transmission that is partially omitted and is transmitted through the upper transmission case half of FIG. 2. In the drawing, what is formed in the upper transmission case half is indicated by a broken line. It is explanatory drawing which shows the position of the 1st projection part in the connection state of the dog clutch of a 5-speed driven gear. It is explanatory drawing which shows the position of the 1st projection part in the connection state of the dog clutch of a 6-speed driven gear. It is explanatory drawing which shows the position of the 1st projection part in the connection state of the dog clutch of a 3rd speed drive gear and a 4th speed drive gear. FIG. 10 is a sectional view taken along line XX in FIG. 9. It is a left view of the shift fork in 2nd embodiment of the transmission of the internal combustion engine which concerns on this invention. It is the enlarged view which expanded the 2nd shift fork and the 6th speed driven gear in 2nd embodiment, and was seen from diagonally left rear.

Hereinafter, a first embodiment of a transmission for an internal combustion engine according to the present invention will be described with reference to the drawings.
In the present specification and claims, the front / rear, left / right, and up / down directions follow the direction of the motorcycle 1 to which the transmission of the internal combustion engine according to the present embodiment is applied, and an arrow FR in the figure points forward. , RE indicates the rear, LT indicates the left side, RT indicates the right side, UP indicates the upper side, and DW indicates the lower side.

  As shown in FIG. 1, a body frame 10 of the motorcycle 1 includes a pair of left and right main frames 12 that extend rearward and slightly downward from the rear portion of the head pipe 11 and bend downward in the middle. A pair of left and right rear frames 13 that extend obliquely upward from the vicinity of the center, a subframe 14 that is laid between the main frame 12 and the rear frame 13, and a down frame that extends downward and obliquely backward from the front of the main frame 12 15 and.

  A front fork 16 extending downward is supported on the head pipe 11 so as to be steerable. A front wheel 17 is rotatably supported at the lower end of the front fork 16. A steering handle 18 is integrally coupled to the upper end of the front fork 16.

In the motorcycle 1, a water-cooled two-cylinder four-stroke internal combustion engine (hereinafter referred to as "internal combustion engine 3"), to which a transmission 5 is integrally connected, is supported by a plurality of brackets 10a of a vehicle body frame 10 and crankshafts. It is mounted horizontally so that 32 is oriented in the vehicle width direction.
Near the lower end of the main frame 12, a front end portion of a swing arm 19 extending rearward is supported by a pivot shaft 19a so as to be vertically movable. A rear wheel 20 is rotatably supported by a rear wheel shaft 20a at the rear end of the swing arm 19. An endless chain 22 is suspended between a drive sprocket 75 fitted to the output shaft (counter shaft) 54 of the transmission 5 and a driven sprocket 21 fitted to the rear wheel shaft 20a.

  As shown in FIGS. 2 and 3, the internal combustion engine 3 includes a crankcase 31 that rotatably supports the crankshaft 32 and a transmission case 80 that houses the transmission mechanism 50. A unit case 30 formed integrally in the front and rear is provided with the transmission case 80 as the rear half. The unit case 30 includes an upper unit case half 30U in which an upper crankcase half 31U and an upper transmission case half 80U are integrally formed, a lower crankcase half 31D, and a lower transmission. The case half body portion 80D and the lower unit case half body portion 30D, which are integrally formed, are vertically divided. From the front, a weight shaft 34, a crankshaft 32, a main shaft 52 of the transmission 51, and a counter shaft 54 are arranged in parallel to the split surfaces 30a of the upper and lower unit case half portions 30U and 30D. A starter motor 48 is disposed above the main shaft 52. An oil pan 35 is attached to the lower part of the lower unit case half 30D.

  A cylinder block 36 in which two cylinder bores 36a, 36a are arranged in series in the left-right direction is superimposed on the cylinder block 36 on the upper side of the upper crankcase half 31U. 37 are stacked and fastened together. A head cover 38 is put on the cylinder head 37.

As shown in FIG. 3, pistons 39, 39 are fitted in the two cylinder bores 36a, 36a of the cylinder block 36 so as to be reciprocally slidable. The piston 39 is connected to the crankshaft 32 via the connecting rod 40.
The cylinder head 37 is formed with two combustion chambers 37a and 37a facing the two pistons 39 and 39, and two spark plugs 41 and 41 are mounted facing the combustion chambers 37a and 37a, respectively. Yes.

The crankshaft 32 is sandwiched via a main bearing 33 by a bearing portion 33a formed on a split surface 31a of the upper and lower crankcase half portions 31U and 31D (that is, a split surface 30a of the upper and lower unit case half portions 30U and 30D). Thus, the crankcase 31 is rotatably supported. A primary drive gear 42 and a cam chain drive sprocket 43 are sequentially fitted to the right side portion of the crankshaft 32 extending rightward from the right main bearing 33 of the crankcase 31 toward the right from the main bearing 33. .
A timing chain 44 is bridged between a cam chain driven sprocket (not shown) fitted to a cam shaft (not shown) of the cylinder head 37 and a cam chain drive sprocket 43.

  A starter driven gear 45 and an AC generator 46 are sequentially provided on the left portion of the crankshaft 32 extending leftward from the main bearing 33 on the left side of the crankshaft 32 toward the left from the main bearing 33. A generator cover 47 is put on the left side of the AC generator 46.

  The starter driven gear 45 is rotatably supported on the crankshaft 32 via a bearing 45a and is connected to the outer rotor 46a of the AC generator 46 fitted on the crankshaft 32 via a one-way clutch 45b. ing. A starter motor 48 is connected to the starter driven gear 45 via an intermediate gear and a starter drive gear (not shown). The generator cover 47 supports the inner stator 46b of the AC generator 46, and the inner stator 46b is disposed inside the outer rotor 46a.

  The inside of the unit case 30 includes a crank chamber C that houses the crankshaft 32 inside the crankcase 31, and a transmission mechanism chamber M that is located behind the crankcase C and houses the transmission mechanism 50 inside the transmission case 80. It is divided into and.

  A transmission 5 that shifts the driving force of the internal combustion engine 3 to a predetermined shift stage includes a transmission 51 that is always meshed and a transmission mechanism 50 that includes a shift operation mechanism 60 that operates the shift stage of the transmission 51, A transmission case 80 that houses the mechanism 50 and a friction clutch 70 are provided.

  As shown in FIGS. 3 and 4, the transmission 51 housed in the transmission case 80 includes a main shaft 52 as an input shaft, a counter shaft 54 as an output shaft, a gear group provided on the main shaft 52 and the counter shaft 54. Has 56.

  The main shaft 52 and the counter shaft 54 of the transmission 51 have left and right bearing portions formed on the split surfaces 80a of the upper and lower transmission case half portions 80U and 80D (that is, the split surfaces 30a of the upper and lower unit case half portions 30U and 30D). It is sandwiched between 53a and 55a via bearings 53 and 55, and is rotatably supported by the transmission case 80.

As shown in FIG. 4, in the speed change mechanism chamber M, six drive gears m1 to m6 having a gear ratio from the first speed to the sixth speed are shifted on the main shaft 52 and the counter shaft 54 is shifted from the first speed to the sixth speed. A ratio of six driven gears c1 to c6 are supported respectively. The drive gears m1 to m6 and the driven gears c1 to c6 are arranged in order from the right side in the order of 1st speed, 5th speed, 4th speed, 3rd speed, 6th speed, 2nd speed, and mesh with each other. The driven gears c1 to c6 constitute a gear group 56.
For the following description, the meshing portions of the drive gears m1 to m6 and the corresponding driven gears c1 to c6 are defined as meshing portions G1 to G6 of the first speed gear to the sixth speed gear, respectively.

Of the drive gears m1 to m6, the third-speed drive gear m3 and the fourth-speed drive gear m4 are spline-fitted to the main shaft 52 and rotate integrally with the main shaft 52, and the left-right direction that is the axial direction of the main shaft 52 It is integrally formed as a shifter SG that can be moved.
A five-speed drive gear m5 that is a gear adjacent to the right side of the third-speed drive gear m3 and a fourth-speed drive gear m4 and a six-speed drive gear m6 that is a gear adjacent to the left are rotatable relative to the main shaft 52. It is formed as a free gear FG that is fixed so as not to move in the axial direction.

Of the driven gears c1 to c6, the fifth-speed driven gear c5 and the sixth-speed driven gear c6 are spline-fitted to the countershaft 54 and rotate integrally with the countershaft 54, and the left-right direction that is the axial direction of the countershaft 54 Are formed as shifters SG that can be moved to each other.
The first-speed driven gear c1 that is a gear adjacent to the right side of the fifth-speed driven gear c5, the fourth-speed driven gear c4 that is a gear adjacent to the left side, and the gear that is adjacent to the right side of the sixth-speed driven gear c6. The third-speed driven gear c3 and the second-speed driven gear c2 that is a gear adjacent to the left are formed as a free gear FG that can rotate relative to the counter shaft 54 and is immovably fixed in the axial direction.

  Shifter side dog teeth Da are formed on the surface of each shifter SG (m3, m4, c5, c6) facing the adjacent free gear FG. Further, among the free gears FG, free-side dog teeth Db are provided on the surfaces of the fifth-speed drive gear m5 and the sixth-speed drive gear m6 facing the shifter SG, and the first-speed driven gear c1, the second-speed driven gear c2, and the third-speed Free-side dog grooves Dc are formed on the surfaces of the driven gear c3 and the fourth-speed driven gear c4 facing the shifter SG, respectively.

The shifter-side dog teeth Da, the free-side dog teeth Db, and the free-side dog grooves Dc are engaged with each other when the shifter SG approaches the corresponding free gear FG, so that the shifter SG cannot rotate relative to the corresponding free gear FG. The dog clutch D is configured such that when the shifter SG is separated from the corresponding free gear FG, the connection is released and the shifter SG is disengaged from the free gear FG. The dog clutch D includes each shifter SG (m3, m4, c5, c6) and a free gear FG (m5, m6, c1, c2, c3, c4) that is a gear adjacent to each shifter SG (m3, m4, c5, c6). ).
In the present specification and claims, the “connected state of the dog clutch D” refers to a state where the shifter-side dog teeth Da and the free-side dog teeth Db or the free-side dog grooves Dc are engaged.

  On the outer peripheral surface of each shifter SG (m3, m4, c5, c6), a fork groove 59 is engaged along the circumferential direction to engage with tip portions 64b, 65b, 66b of shift forks 64, 65, 66 described later. Each is formed.

Next, the speed change operation mechanism 60 will be described.
As shown in FIG. 3, the speed change operation mechanism 60 includes a shift drum 61, shift forks 64, 65, 66, a shift spindle 67 and a link mechanism 69, and the shift spindle 67 moves the shift drum 61 via the link mechanism 69. The shift forks 64, 65, 66 are moved by intermittently rotating, and each shifter SG of the transmission 51 is moved in the axial direction to switch the gear position of the transmission 51.

  As shown in FIGS. 2 and 3, a shift drum 61 is rotatably supported on the left and right bearings 62a provided on the lower transmission case half 80D below the main shaft 52 via a bearing 62. ing. Three lead grooves 61 b are formed on the outer peripheral surface 61 a of the shift drum 61 along the circumferential direction of the shift drum 61.

As shown in FIG. 3, below the main shaft 52 and the counter shaft 54, a shift fork shaft 63 is supported by fitting both ends to left and right bearing portions 63a provided in the lower transmission case half body portion 80D. Has been.
On the shift fork shaft 63, a first shift fork 64, a second shift fork 65, and a third shift fork 66 are supported in order from the right side so as to be movable in the axial direction. The shift pins 64a, 65a, 66a of the shift forks 64, 65, 66 are fitted in the lead grooves 61b of the shift drum 61, respectively. The front end portions 64b, 65b, 66b of each shift fork 64, 65, 66 are divided into two forks, and the front end portion 64b of the first shift fork 64 is inserted into the fork groove 59 of the fifth-speed driven gear c5. The tip 65b is engaged with the fork groove 59 of the third speed drive gear m3 and the fourth speed drive gear m4, and the tip 66b of the third shift fork 66 is engaged with the fork groove 59 of the sixth speed driven gear c6.

  Further, behind the shift drum 61, a shift spindle 67 is rotatably supported via a bearing 68 on a bearing portion 68a provided in the lower transmission case half 80D. A link mechanism 69 that rotates the shift drum 61 intermittently by the rotation of the shift spindle 67 is provided at the right ends of the shift spindle 67 and the shift drum 61. The shift drum 61, the shift fork shaft 63, and the shift spindle 67 are arranged with the main shaft 52 and the counter shaft 54 in parallel with each other in the axial direction.

  A multi-plate friction clutch 70 is provided at the right end of the main shaft 52 extending rightward from the right bearing of the main shaft 52. A clutch inner 70 a of the friction clutch 70 is spline-fitted to the right end portion of the main shaft 52. A clutch outer 70b of the friction clutch 70 is supported on a primary driven gear 71 that is rotatably supported by the main shaft 52 between a bearing 53a on the right side of the main shaft 52 and a clutch inner 70a.

  A clutch release mechanism 72 that disconnects the friction clutch 70 is provided on the left side of the transmission case 80. The clutch release mechanism 72 rotates the lever portion 72a connected to the clutch cable 73 (see FIG. 10), moves the shaft portion 72b to the right, and pushes the pressure plate 70c to the right with the release rod 74. Then, the transmission of the driving force from the clutch outer 70b to the clutch inner 70a is cut off.

  A drive sprocket 75 is fitted to the left end portion of the counter shaft 54 extending leftward from the left bearing 55 of the counter shaft 54. The left side of the drive sprocket 75 is covered with a chain cover 49.

FIG. 6 is a VI arrow view of the transmission seen through the upper transmission case half of FIG. In FIG. 6, ribs and protrusions to be described later are illustrated by broken lines, and parts other than the main gear are omitted and are not illustrated by hatching.
As shown in FIGS. 5 and 6, the upper wall portion 81 of the upper transmission case half 80U is positioned above the fifth-speed driven gear c5 and opens toward the fifth-speed drive gear m5. An opening 81a is provided. Referring also to FIG. 2, a speed sensor 89 is inserted into the sensor opening 81a obliquely from above the upper transmission case half 80U toward the fifth-speed drive gear m5.

  As shown in FIG. 5, a rib 83 is formed on the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half 80 </ b> U so that a part of the inner wall surface 82 protrudes downward. That is, a part of the inner wall surface 82 of the upper wall portion 81 is formed as a rib 83 protruding downward. As shown in FIG. 10, the rib 83 is formed to have a substantially constant height in the vertical direction along the shape of the inner wall surface 82 of the upper wall portion 81.

Referring also to FIG. 6, the rib 83 includes an oblique rib 84 oriented in an oblique direction with respect to the axial direction of the main shaft 52 or the counter shaft 54 (hereinafter simply referred to as “axial direction”), as viewed from above, and the axial direction. The parallel ribs 87 are oriented in a direction parallel to the.
The rib 83 is partly divided by the sensor opening 81a. However, in the following description, it is assumed that the rib 83 is not increased or decreased by the divided portion.

  As illustrated by α in FIG. 5, the oblique rib 84 is a first oblique rib directed from the left oblique front to the right oblique rear so that the angle with respect to the axial direction is an acute angle (about 30 degrees in the present embodiment). 85 and a second oblique rib 86 extending from the right oblique front to the left oblique rear so that the angle with respect to the axial direction is an acute angle (about 30 degrees in the present embodiment) as illustrated by β in FIG. Have.

As shown in FIG. 5, four each of the first oblique ribs 85 and the second oblique ribs 86 are formed so that the first oblique ribs 85 and the second oblique ribs 86 are substantially parallel to each other. It is installed. Referring also to FIG. 6, the first oblique ribs 85 and the second oblique ribs 86 are arranged in the first oblique ribs 85 across the region from the front of the main shaft 52 to the rear of the counter shaft 54 as viewed from above. The second diagonal ribs 86 are arranged substantially evenly so that the interval between the second diagonal ribs 86 is slightly narrowed toward the rear.
As described above, a part of the inner wall surface 82 of the upper wall portion 81 is formed as the inclined ribs 84, thereby improving the rigidity of the upper wall portion 81 and reducing the noise of the transmission case 80 during the shift operation.

As shown in FIG. 6, the parallel ribs 87 are located between the main shaft 52 and the counter shaft 54 when viewed from above and above the meshing portion G2 of the second gear and the meshing portion G3 of the third gear. One is formed from the left end to the right end of the upper wall portion 81 at a passing position.
The parallel ribs 87 may be disposed between the main shaft 52 and the counter shaft 54 as viewed from above, but the first to sixth gear meshing portions G1 to G1 as in the present embodiment. It is preferable to be disposed above at least one of G6.

  The first oblique rib 85 and the second oblique rib 86 are arranged in a mesh shape, and the oblique rib 84 is formed with an intersection X where the first oblique rib 85 and the second oblique rib 86 intersect. The intersecting portion X is formed long in the axial direction. In the present embodiment, seven intersections X are formed. When viewed from above, the two intersections X1 and X2 are on the axis center line L2 of the counter shaft 54, and the intersection X3 is the axis center line of the main shaft 52. On the L1, the intersections X4 and X6 are disposed between the main shaft 52 and the counter shaft 54, respectively, in front of the two intersections X5 main shaft 52.

  As shown in FIG. 6, two intersections X1 and X2 located above the axis center line L2 of the counter shaft 54 have one intersection (hereinafter referred to as “first intersection X1”), and the dog clutch D is The center of the intersection X (hereinafter referred to as “intersection Y”) is located above the fork groove 59 of the fifth-speed driven gear c5 in the unconnected state (hereinafter referred to as “neutral state Pn”). 59, the other crossing portion (hereinafter referred to as “second crossing portion X2”) is located above the fork groove 59 of the six-speed driven gear c6 in the neutral state Pn. The fork grooves 59 are formed across the axial direction.

  An intersection located above the axis center line L1 of the main shaft 52 (hereinafter referred to as “third intersection X3”) is above the fork grooves 59 of the third speed drive gear m3 and the fourth speed drive gear m4 in the neutral state Pn. The intersection Y is located and is formed across the fork groove 59 in the axial direction when viewed from above.

FIG. 5 shows a region where the gear teeth projected from the lower side on the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half 80U (hereinafter referred to as “tooth region T”) The reference numerals m1 to m6 and c1 to c6 of the gears are indicated by two-dot chain lines.
Referring also to FIG. 5, the two intersecting portions X5 and X5 positioned in front of the main shaft 52 in the upper view are respectively tooth regions T (m5) and T (m6) of the fifth speed driving gear m5 and the sixth speed driving gear m6. ) Above.

  Further, of the intersections X4 and X6 located between the main shaft 52 and the counter shaft 54 as viewed from above, the intersection near the main shaft 52 (hereinafter referred to as “fourth intersection X4”) of the six-speed drive gear m6. Above the tooth region T (m6), the intersection X6 near the counter shaft 54 is formed above the tooth regions T (m3) and T (m4) of the third speed driven gear c3 and the fourth speed driven gear c4, respectively. Yes. Note that the parallel ribs 87 also intersect the fourth intersecting portion X4.

  On the rib 83 (that is, a part of the inner wall surface 82 of the upper wall part 81), a part of the rib 83 protrudes downward to form a protrusion 90. The protrusion 90 is formed by a first protrusion 91, which is a first protrusion formed by projecting a part of the oblique rib 84 downward, and a part of the parallel rib 87 projecting downward. And a second protrusion 92 that is a second protrusion. Referring also to FIG. 10, the projecting portion 90 has a lower end formed in a hemispherical shape, and is formed to be slightly tapered toward the lower end in a longitudinal sectional view.

  As shown in FIG. 6, the first protrusions 91 are formed at the first intersection X1, the second intersection X2, and the third intersection X3, respectively. Hereinafter, the arrangement of the first protrusions 91 will be specifically described.

  As shown by shading in FIG. 7, the first protrusion 91 formed at the first intersecting portion X1 is, when viewed from above, the axis center line L2 of the counter shaft 54 (that is, the rotation axis L3 of the fifth-speed driven gear c5). ) And the fifth speed driven gear c5 is the first speed position P1 where the first speed driven gear c1 and the dog clutch D are connected, and the fifth speed driven gear c5 indicated by a two-dot chain line in FIG. 7 is the fourth speed driven gear c4. And a fourth speed position P4 at which the dog clutch D is connected to the fork groove 59 of the fifth speed driven gear c5.

  As shown by shading in FIG. 8, the first protrusion 91 formed at the second intersecting portion X2 has an axis center line L2 of the counter shaft 54 (that is, the rotation axis L4 of the sixth-speed driven gear c6) when viewed from above. ) And the third speed position P3 where the sixth speed driven gear c6 is connected to the third speed driven gear c3 and the dog clutch D, and the sixth speed driven gear c6 indicated by a two-dot chain line in FIG. 8 is the second speed driven gear c2. And a second speed position P2 at which the dog clutch D is connected to the fork groove 59 of the sixth speed driven gear c6.

  9, the first protrusion 91 formed at the third intersection X3 has an axial center line L1 of the main shaft 52 (that is, the third speed drive gear m3 and the fourth speed drive) when viewed from above. On the rotation axis L5) of the gear m4, the third speed driving gear m3 and the fourth speed driving gear m4 are in the connected state of the fifth speed driving gear m5 and the dog clutch D, and the third speed driving gear m3 and the fourth speed driving gear m4 One high-speed drive gear m4 is formed at a position overlapping the fork groove 59 of the third-speed drive gear m3 and the fourth-speed drive gear m4 at the sixth-speed position P6 where the sixth-speed drive gear m6 and the dog clutch D are connected. .

  As shown in FIGS. 5 and 6, the second protrusions 92 formed on the parallel ribs 87 are, as viewed from above in the neutral state Pn, the first speed driven gear c1, the fourth speed driving gear m4, and the sixth speed driving gear m6. One tooth region T (m4), T (m6), one at the center of the tooth width in each of the meshing portions G2, G3 of the second gear and the third gear. Of the second protrusions 92, the second protrusions 92 located above the tooth region T (m4) of the fourth speed drive gear m4 are formed at the center of the fourth intersection X4.

  As shown in FIG. 10, the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U is a portion slightly closer to the center in the front-rear direction from the rear end 82a (hereinafter referred to as “inner wall surface”). It is inclined with respect to the horizontal surface H so that the position of the inner wall surface 82 becomes lower toward the “low portion 82c”), and the position of the inner wall surface 82 becomes higher from the inner wall low portion 82c toward the front end 82b. Thus, it is formed to be inclined in the front-rear direction with respect to the horizontal plane H. That is, the inner wall surface low portion 82 c is located at the lowest position among the inner wall surfaces 82 of the upper wall portion 81. The low inner wall surface portion 82 c is located above the axis center line L 1 of the main shaft 52 and the parallel rib 87.

  As described above, the rib 83 is formed to have a substantially constant height in the vertical direction along the shape of the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U. The oblique rib 84 has an inclination along the inclination of the inner wall surface 82. On the other hand, since the parallel ribs 87 are formed parallel to the axial direction, they do not have an inclination.

  As described above, the rib 83 and the protrusion 90 formed on the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U act as follows.

  When the main shaft 52 and the counter shaft 54 rotate, they are discharged from oil passages 52a and 54a formed inside the main shaft 52 and the counter shaft 54, and lubricate the drive gears m1 to m6 and the driven gears c1 to c6. The oil jumps up by centrifugal force and adheres to the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U. Further, when the motorcycle 1 travels, the oil in the oil pan 35 jumps up due to shaking or vibration and adheres to the inner wall surface 82.

  Referring to FIG. 6, the oil collects in the oblique ribs 84 and the parallel ribs 87 located nearby due to the surface tension of the oil itself and the action of gravity on the oil. Then, most of the oil collected on the oblique rib 84 gathers at the intersection X along the oblique rib 84. Among them, the oil collected at the intersections X5 and X6 is the tooth region T of the third speed driven gear c3, the fourth speed driven gear c4, the fifth speed drive gear m5 and the sixth speed drive gear m6 located below the intersections X5 and X6. The gears G3 to G6 of these gears are lubricated.

On the other hand, the oil gathered at the first intersection X1, the second intersection X2, and the third intersection X3 gathers at the first protrusions 91 formed respectively. The oil collected in the first projection 91 is dropped into the fork groove 59 of any shifter SG (m3, m4, c5, c6) in the connected state of the dog clutch D, and the fork groove 59 and the shift fork 64, Lubricate the tip portions 64b, 65b, 66b of 65, 66.
For example, as shown in FIG. 7, when the gear position is at the first speed position P1 where the dog clutch D between the fifth speed driven gear c5 and the first speed driven gear c1 is connected, the fork groove 59 of the fifth speed driven gear c5. Then, oil is dripped from the first projection 91 on the right side of the first intersection X1, and the fork groove 59 and the front end portion 64b of the first shift fork 64 engaged with the fork groove 59 are lubricated. Thus, even when the dog clutch D is connected and disconnected, even if the tip portions 64b, 65b, 66b of the shift forks 64, 65, 66 are in strong contact with the side wall of the fork groove 59, the shift engages with the fork groove 59. Lubrication between the tip portions 64b, 65b, and 66b of the forks 64, 65, and 66 can be sufficiently maintained.

  As shown in FIGS. 6 to 10, the first protrusion 91 is located on the rotation axis L3 to L5 of each shifter SG (the axis centerlines L1 and L2 of the main shaft 52 and the counter shaft 54). Therefore, the oil adhering to the inner wall surface 82 is dropped from the first protrusion 91 to the apex portion 59a in the circumferential direction of the fork groove 59. This oil flows in the forward and backward directions in the fork groove 59, and the oil can be efficiently spread in the fork groove 59. Further, even if the oil dropping position is shifted back and forth due to vibration, inertia, etc., the oil is likely to be dropped into the fork groove 59.

  The oil collected in the parallel ribs 87 gathers in the second protrusion 92, and tooth regions T (m4 of the first speed driven gear c1, the fourth speed drive gear m4, and the sixth speed drive gear m6 located below the second protrusion 92. ), T (m6), and drops onto the meshing portions G2 and G3 of the second gear and the third gear, respectively, to lubricate the meshing portions G1 to G4 and G6 of these gears. In the present embodiment, the oil collected at the second protrusion 92 does not lubricate the meshing part G5 of the fifth gear by installing the speed sensor 89, but the meshing part G5 of the fifth gear is also lubricated. You may comprise.

  The inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U is inclined in the front-rear direction with respect to the horizontal plane H, and the oil attached to the inner wall surface 82 flows along the inclination. Therefore, the oil adhering to the inner wall surface 82 is likely to gather on the oblique ribs 84 and the parallel ribs 87 located below the adhering location. In addition, since the oblique rib 84 itself has an inclination along the inclined surface, the oil transmitted through the oblique rib 84 is likely to gather at the intersecting portion X located below the oblique rib 84. Since the parallel ribs 87 do not have an inclination, the oil collected on the parallel ribs 87 does not flow in one direction and is collected almost evenly on all the second protrusions 92.

As described above, the transmission 5 of the internal combustion engine 3 according to the first embodiment of the present invention described in detail has the following effects.
A part of the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U protrudes downward and is formed as an oblique rib 84 that is oriented obliquely with respect to the axial direction when viewed from above. Has been. The oblique rib 84 is formed with intersecting portions X1 to X6. A first protrusion 91 that protrudes downward from the intersections X1 to X3 is formed at the intersections X1 to X3 at a position overlapping the fork groove 59 of each shifter SG in the connected state of the dog clutch D when viewed from above. ing.
According to such a configuration, the oil attached to the inner wall surface 82 of the upper wall portion 81 can be collected (captured) from a wide range by the oblique ribs 84. The oil collected on the oblique rib 84 gathers at the intersections X1 to X6 along the oblique rib 84. The oil collected at the intersections X1 to X3 is dropped from the first protrusion 91 into the fork groove 59 located below the first protrusion 91 in the connected state of the dog clutch D. Therefore, it becomes possible to supply oil to the fork groove 59 in the connected state of the dog clutch D with a simple configuration in which a part of the inner wall surface 82 is formed as the inclined rib 84 or the first protrusion 91, and the transmission case Lubrication between the fork groove 59 and the shift forks 64, 65, 66 can be improved without increasing the manufacturing cost of 80.

The oil collected at the intersections X4 to X6 is the tooth regions T (m5), T (m6), T (c3), and T (c4) of the gears m5, m6, c3, and c4 located below the intersections. Therefore, the meshing portions G3 to G6 of the third speed gear to the sixth speed gear can be lubricated with a simple configuration in which the intersection portion X is provided.
Furthermore, since the oblique ribs 84 are formed substantially uniformly on the entire inner wall surface 82 of the upper wall portion 81, it is possible to improve the rigidity of the upper wall portion 81, and at the same time, a transmission case for the shift operation material. It is possible to reduce the noise of 80.

  Since the intersecting portions X1 to X3 are located above the main shaft 52 and the counter shaft 54, the oil gathered at the intersecting portions X1 to X3 through the oblique ribs 84 is removed from the main shaft 52, the counter shaft 54, and the gear group. They can be dripped into 56 to improve their lubrication.

  A plurality of first protrusions 91 are formed along the axial direction. Therefore, oil can be dripped into the fork groove 59 when the dog clutch D is joined to one shifter SG. Further, when two shifters SG are arranged on one support shaft (in this embodiment, the counter shaft 54) like the fifth-speed driven gear c5 and the sixth-speed driven gear c6 in the present embodiment. The oil can be dropped into the fork groove 59 in the joined state of the dog clutch D of each shifter SG.

  The first protrusions 91 are located on the rotation axes L3 to L5 of the shifters SG (the axis centerlines L1 and L2 of the main shaft 52 and the counter shaft 54), and the oil attached to the inner wall surface 82 is the first Dropped from the protrusion 91 to the apex 59a in the circumferential direction of the fork groove 59. This oil flows in the fork groove 59 in two directions, the front and the rear, along the circumferential direction of the gear, so that the oil can be efficiently spread in the fork groove 59. Further, even if the oil dropping position is shifted back and forth due to vibration, inertia, etc., the oil is surely dropped into the fork groove 59.

  Among the intersections X, the intersections X1 to X3 where the first protrusions 91 are formed are such that the first intersection X1 and the second intersection X2 are above the counter shaft 54, and the third intersection X3 is the main shaft 52. Three places are formed above the top. Then, the oil collected at the intersections X1 to X3 is supplied to the fork groove 59 of the third speed drive gear m3 and the fourth speed drive gear m4 provided on the main shaft 52, and the fifth speed driven gear c5 and the sixth speed provided on the counter shaft 54. It is dropped into any of the fork grooves 59 of the driven gear c6. Therefore, oil can be reliably supplied to the fork groove 59 of each shifter SG regardless of which of the main shaft 52 and the counter shaft 54 is operating at high speed. , 66 can improve the lubrication.

  Since the inner wall surface 82 of the upper wall portion 81 of the transmission case 80 is inclined with respect to the horizontal plane H, the oil attached to the inner wall surface 82 of the upper wall portion 81 flows along the inclination. As a result, the efficiency of oil collection at the protrusions 90 and ribs 83 located in the middle of the oil flow is improved, and the amount of oil dripping from the protrusions 90 increases. As a result, the fork groove 59 and the shift forks 64, 65, 66 are Lubrication can be improved.

A part of the inner wall surface 82 of the upper wall portion 81 of the transmission case 80 is formed as a parallel rib 87 that protrudes downward and points in a direction parallel to the axial direction. The parallel ribs 87 are located between the main shaft 52 and the counter shaft 54 when viewed from above. The parallel ribs 87 are provided with second protrusions 92 projecting downward from the parallel ribs 87 and the tooth regions T (m4), T (m6), T (c1) and the meshing portions G2, as viewed from above. It is located at G3.
The oil adhering to the inner wall surface 82 also collects on the parallel ribs 87, travels along the parallel ribs 87, and collects on the second protrusion 92. The oil collected in the second protrusion 92 is the tooth region T (m4), T (m6), T (c1) or meshing portion G2 of the gear disposed between the main shaft 52 and the counter shaft 54. , G3. Therefore, oil can be supplied to the gear group 56 provided between the main shaft 52 and the counter shaft 54 with a simple configuration.

  The first embodiment of the present invention has been described above with reference to the drawings. However, the first embodiment is not limited to the above description, and can be changed without departing from the spirit of the present invention.

  For example, in the present embodiment, a part of the inner wall surface 82 of the upper wall portion 81 of the upper transmission case half body portion 80U is formed as the rib 83, but a part of the inner wall surface 82 is directly used as the protrusion 90. It may be formed. In this case, the oil collecting effect by the rib 83 cannot be obtained, but the oil adhering to the periphery of the protrusion 90 is collected in the protrusion 90, and the protrusion in the connected state of the tooth region T of each gear and the dog clutch D. Dropped from the projection 90 into the fork groove 59 and the like located below the 90. Therefore, it becomes possible to supply oil to the fork groove 59 in the connected state of the dog clutch D with a simple configuration in which only the protrusion 90 is provided on the inner wall surface 82 of the upper wall portion 81, thereby reducing the manufacturing cost of the transmission case 80. Lubrication between the fork groove 59 and the shift forks 64, 65, 66 can be improved without increasing.

  In the present embodiment, the oblique rib 84 includes a first oblique rib 85 and a second oblique rib 86, and a first protrusion 91 is formed at the intersection X. However, the oblique rib 84 forms only one of the first oblique rib 85 and the second oblique rib 86, and the first protrusion 91 is formed on the formed first oblique rib 85 or second oblique rib 86. It may be formed.

In the present embodiment, the first protrusions 91 are formed at six locations above each shifter SG, but may be formed by reducing the number as necessary.
Further, the inner wall surface 82 of the upper wall portion 81 is preferably formed to be inclined with respect to the horizontal plane, but may be formed in parallel to the horizontal plane.

One parallel rib 87 is disposed between the main shaft 52 and the counter shaft 54 when viewed from above, but is located above all of the meshing portions G1 to G6 of the first to sixth gears. Alternatively, it may be formed by dividing and shifting the front and rear positions.
Further, the shifter is not limited to a gear, and may be a gear without a gear.

  Next, a second embodiment of the transmission 5 of the internal combustion engine 3 according to the present invention will be described with reference to the drawings. In the second embodiment, the same members as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 11, the shift fork 100 is formed with a fork rib 104 that protrudes in the axial direction of the shift fork shaft 63. The fork rib 104 protrudes downward along the tooth tip circle Q of the gear, which is a gear (not shown) adjacent to the side of the shift fork 100 where the fork rib 104 protrudes. It is curved.
Note that the fork rib 104 may be formed so as to project not only in one axial direction of the shift fork 100 but also in one axial direction with respect to one shift fork 100.

Hereinafter, an example in which the fork rib 104 is formed on the second shift fork 102 will be described.
As shown in FIG. 12, a fork rib 104 is formed on the left side surface 102a of the second shift fork 102 so as to protrude leftward. The fork rib 104 extends along the tip circle Q of the sixth-speed driven gear c6 at the lower side in the radial direction of the sixth-speed driven gear c6 adjacent to the side on which the fork rib 104 protrudes (that is, the left side) of the second shift fork 102. It is formed to be curved so as to protrude downward.

Therefore, the oil dropped from the first protrusion 91 of the second intersection X2 and the oil dropped from the second protrusion 92 of the fourth intersection X4 are passed through the six-speed driven gear c6 and the second shift fork 102. Then, the fork rib 104 is stored in the curved portion 104a. The oil accumulated in the curved portion 104a comes into contact with the tooth tip of the sixth-speed driven gear c6 to lubricate the sixth-speed driven gear c6 and the meshing portion G6 of the sixth-speed gear, and a part of the oil is stored in the sixth-speed driven gear c6. In addition to being splashed to the tooth tip and adhering to the inner wall surface 82 of the upper wall portion 81 of the transmission case 80, a part thereof is also supplied to the fork groove 59 of the six-speed driven gear c6 through the second shift fork 102. .
In addition, since the fork rib 104 is arranged below the high-speed six-speed driven gear c6, the high-speed six-speed driven gear c6 that requires lubrication and the meshing portion G6 of the six-speed gear are more effective. Can be lubricated.

  The fork ribs 104 may be formed not on the second shift fork 102 but on a first shift fork or a third shift fork 103 (not shown). In this case, the fork rib 104 is a maximum of the third speed driving gear m3, the fourth speed driving gear m4, and the third to sixth speed driven gears c3 to c6 (the third speed at the third speed position P3 for the third speed driven gear c3). It can be formed below the driven gear c3 and the fourth speed driven gear c4 below the fourth speed driven gear c4 at the fourth speed position P4.

As described above, the transmission for an internal combustion engine according to the second embodiment of the present invention described in detail with reference to the drawings has the following effects.
The shift fork 100 is formed with fork ribs 104 that protrude in the axial direction of the shift fork shaft 63. The fork ribs 104 are formed along the tooth tip circles Q of the gears adjacent to the side where the fork ribs 104 of the shift fork 100 project.
Therefore, the oil dropped from the rib 83, the intersecting portion X, and the protruding portion 90 is accumulated in the curved portion 104a of the fork rib 104, and lubricates the gear located above the fork rib 104 and the meshing portion G of the gear. be able to. Further, the oil accumulated in the curved portion 104a is splashed up by the contact of the gear teeth, adheres to the inner wall surface 82 of the upper wall portion 81 of the transmission case 80, and part of the oil travels through the shift fork 100. To the fork groove 59 of the shifter SG.
As described above, the gears m3, m4, C3 to C6 adjacent to the shift fork 100 and the meshing portions G3 to G6 thereof and the fork groove 59 with which the shift fork 100 engages can be obtained only by changing the shape of the shift fork 100. Lubrication can be improved.

DESCRIPTION OF SYMBOLS 3 ... Internal combustion engine, 5 ... Transmission, 52 ... Main shaft, 54 ... Counter shaft, 56 ... Gear group, 59 ... Fork groove, 64, 65, 66 ... Shift fork, 80 ... Transmission case, 81 ... Upper wall part , 82 ... inner wall surface, 84 ... oblique ribs, 87 ... parallel ribs, 91 ... first protrusion, 92 ... second protrusion, 100 ... shift fork, 104 ... fork rib D ... dog clutch, H ... horizontal plane, L2 , L3, L4 ... rotation axis, Q ... addendum circle, X ... intersection, m3, m4, c3, c4, c5, c6 ... gear adjacent to the shift fork, SG ... shifter, FG ... free gear (adjacent to the shifter) Gear)

Claims (8)

The main shaft (52),
A counter shaft (54) disposed in parallel with the main shaft (52),
A gear group (56) provided on the main shaft (52) and the counter shaft (54);
Shift forks (64, 65, 66, 100) for shifting the gear group (56);
A shift fork shaft (63) that supports the shift fork (64, 65, 66, 100) so as to be movable in the axial direction;
A transmission case (80) that houses the main shaft (52), the counter shaft (54), the gear group (56), and the shift forks (64, 65, 66, 100);
The shift fork (64, 65, 66, 100) is fitted, and a shift drum (61) for moving the shift fork (64, 65, 66, 100) in the axial direction,
A part of the gear group (56) is formed as a shifter (SG) that rotates integrally with the shaft and is movable in the axial direction.
The shifter (SG) is formed with a fork groove (59) with which the shift fork (64, 65, 66, 100) is engaged,
A dog clutch that connects or disengages the shifter (SG) and the gear (FG) adjacent to the shifter (SG) between the shifter (SG) and the gear (FG) adjacent to the shifter (SG). In the transmission (5) of the internal combustion engine (3) provided with D),
The shift drum (61) and the shift fork shaft (63) are disposed below the main shaft (52) and the counter shaft (54),
A part of the inner wall surface (82) of the upper wall portion (81) of the transmission case (80) protrudes downward, and when viewed from above, the main shaft (52) or the counter shaft (54) Formed as an oblique rib (84) oriented in an oblique direction with respect to the axial direction of
A plurality of the oblique ribs (84) are formed,
The oblique rib (84) has an intersecting portion (X) intersecting above at least one of the main shaft (52) and the counter shaft (54),
The intersecting portion (X) is formed long in the axial direction of the shift fork shaft (63), and the fork groove (59) in the neutral state of the dog clutch (D) is seen from above in the neutral state of the shift fork shaft (63). Straddling in the axial direction of
The intersection (X) is formed with a plurality of first protrusions (91) protruding downward from the inner wall surface (82) of the upper wall portion (81) ,
The plurality of first protrusions (91) are distributed in the axial direction of the shift fork shaft (63) with respect to the position of the fork groove (59) in the neutral state of the dog clutch (D), and the intersection Arranged on both sides of the part (X),
One or more of the first protrusions (91) are disposed at positions overlapping the fork grooves (59) in each connected state of the dog clutch (D) when viewed from above. (3) The transmission (5). The internal combustion engine (3) according to claim 1, wherein a plurality of the first protrusions (91) are formed along an axial direction of the main shaft (52) or the counter shaft (54 ). The transmission (5). The internal combustion engine (3) according to claim 2, wherein the first protrusion (91) is located on a rotation axis (L3, L4, L5) of the shifter (SG) when viewed from above. The transmission (5). The intersection (X) is formed at three or more locations, and is located above each of the main shaft (52) and the counter shaft (54) . A transmission (5) for an internal combustion engine (3) according to any one of the preceding claims. Wherein the inner wall surface of the upper wall portion of the transmission case (80) (81) (82), any one of claims 1 to 4, characterized in that it is inclined relative to the horizontal plane (H) A transmission (5) for an internal combustion engine (3) according to claim 1 . A part of the inner wall surface (82) of the upper wall portion (81) of the transmission case (80) protrudes downward and points in a direction parallel to the axial direction of the main shaft (52). Formed as parallel ribs (87)
The said parallel rib (87) is located between the said main axis | shaft (52) and the said counter axis | shaft (54) in upper direction, The one of Claim 1 thru | or 5 characterized by the above-mentioned. A transmission (5) of the internal combustion engine (3). The parallel rib (87) is formed with a second protrusion (92) protruding downward from the parallel rib (87),
The internal combustion engine (3 ) according to claim 6 , wherein the second protrusion (92) is located in a region (T) where the teeth of the gear group (56) are formed as viewed from above. ) Transmission (5). The shift fork (100) is supported on the shift fork shaft (63) so as to be movable in the axial direction,
The shift fork (100) is provided with a fork rib (104) protruding in the axial direction of the shift fork shaft (63),
The fork rib (104) is disposed below the gear (m3, m4, c3, c4, c5, c6) adjacent to the side of the shift fork (100) from which the fork rib (104) protrudes. The internal combustion engine according to any one of claims 1 to 7, wherein the internal combustion engine is formed by being curved along a tip circle (Q) of (m3, m4, c3, c4, c5, c6). The transmission (5) of the engine (3).

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