JP4638291B2 - engine - Google Patents

Description

  The present invention includes an engine, a so-called cassette-type (or cartridge-type) mission, in which a mission assembly formed by supporting a plurality of transmission shafts and the like on a shaft support member is detachably accommodated in an engine mission chamber. Related to the engine.

  8 and 9 show an example of an engine provided with a conventional cassette type transmission (Patent Document 1). In FIG. 8 showing a developed sectional view, a mission cover (shaft support) which is a member different from the crankcase 301 is shown. Member) 302 is configured to support the transmission input shaft 303, the output shaft 304, the pump shaft 312a of the oil pump 312 and the like in a cantilever manner, thereby constituting the mission assembly M. As a unit, the unit is inserted into the mission chamber 310 in the axial direction, the mission cover 302 is attached to the opening end surface of the mission chamber 310, and the tip portions of the shafts 303 and 304 are supported on the other side walls of the mission chamber 310.

  A clutch 322 for connecting / disconnecting power from the crankshaft 331 is attached to the end of the input shaft 303, and an output sprocket 323 for transmitting power to wheels or the like is fixed to the end of the output shaft 304, for example. However, the clutch 322 and the output sprocket 323 are arranged separately at both ends in the axial direction in order to maintain the compactness of the entire mission.

  In FIG. 9 showing the right side view with the clutch cover removed, the transmission cover 302 also supports a change drum 325 in addition to the input shaft 303, the output shaft 304, the pump shaft 312a of the oil pump 312 and the like. In the arrangement of the shafts 303, 304, 312 a, etc. in the mission chamber 310, the input shaft 303 is disposed at the front portion closest to the crankshaft 331, the output shaft 304 is disposed behind the input shaft 303, and the input shaft 303. A change drum 325 is disposed below the pump shaft 312 and a pump shaft 312 a is disposed at the rear lower end of the mission chamber 310. Oil passages 320 and 321 are formed in the input shaft 303 and the output shaft 304, respectively.

The pump shaft 312a is adapted to transmit power from the gear 303a of the input shaft 303 via transmission gears (gear transmission mechanisms) 333 and 334.
JP-A-1-169171

  In an engine equipped with a cassette-type transmission, if the oil pump 312 is arranged behind the output shaft 304 as shown in FIG. 9, the dimension of the crankcase 1 in the front-rear direction becomes longer, and the engine becomes larger. At the same time, the shaft support member 302 of the transmission assembly M is also a member having a large area, which takes time for assembly work and causes an increase in weight.

  The oil pump 312 is moved closer to the input shaft 303 by changing the arrangement position of the oil pump 312 to, for example, a position in front of the output shaft 304, most preferably the front lower end portion of the mission chamber 11, so Compactness can be achieved.

  However, even if the oil pump 312 is arranged at the front lower end of the mission chamber 310 and its power is taken out from an arbitrary transmission shaft of the mission set M by the gear transmission mechanism, the arrangement position of the gear transmission mechanism is greatly limited. The degree of freedom of the arrangement position of the oil pump is limited, and when the pump 312 is arranged at a position away from the transmission shaft (input shaft 303) for taking out power, the gear diameter increases and the weight increases. Cause.

  In contrast to such an oil pump drive system using a gear transmission mechanism, when a winding transmission mechanism, for example, a chain transmission mechanism, is provided, the degree of freedom in the arrangement position of the oil pump is increased, which hinders the power transmission mechanism. The oil pump can be easily arranged at the front lower end of the transmission chamber without causing a high degree of accuracy, and does not require a high degree of assembling accuracy as compared with the gear transmission mechanism.

  However, when the oil pump is arranged at the front lower end of the transmission chamber and is driven by the chain transmission mechanism to reduce the size of the crankcase in the longitudinal direction, the chain transmission mechanism is As a result, the chain may come into contact with the crank part (weight part) of the crankshaft and generate a contact sound that may cause noise. Therefore, in consideration of the chain runout range, the chain has to be disposed behind the crank portion at a predetermined distance, and it is difficult to achieve a reduction in size in the longitudinal direction of the engine.

  The present invention has been made in view of the above problems, and by using a winding transmission mechanism such as a chain transmission mechanism, the degree of freedom of the arrangement position of the hydraulic pump arranged in the transmission chamber is increased, and the engine By making the front and rear dimensions smaller, and preventing the generation of contact noise between the chain and other cable-like bodies and the crank part, the winding transmission mechanism can be brought closer to the crank part. The purpose is to make the engine dimension in the front-rear direction more compact.

In order to solve the above-mentioned problems, the present invention comprises a crank chamber in the front half of a crankcase having a vertically divided structure and a transmission chamber in the rear half, wherein the transmission chamber has at least an input shaft, a shaft support member, The transmission assembly supporting the output shaft and the change drum is detachably accommodated, a hydraulic pump is disposed, the output shaft is disposed on the upper and lower mating surfaces of the crankcase, and the input shaft is Arranged above the mating surface, the change drum is arranged below the mating surface, the hydraulic pump is arranged at the front lower end of the mission chamber, the input shaft, the hydraulic pump, the interlockingly connected by winding transmission mechanism, between the crank portion of the crank chamber-side portion and the crank shaft of the wick member of KimakiKake transmission mechanism, to regulate the deflection of the at least the front of the wick member The regulating guide disposed, the regulating guide is attached to the upper and lower, said crank chamber side has a mounting boss projecting on the opposite side, respectively, both said mounting boss portion to the shaft support member It has been .

According to the above configuration, the cassette-type transmission assembly can be stored close to the crank chamber side, thereby achieving a reduction in the size of the engine in the front-rear direction. Contact between the body and the crank part of the crankshaft can be prevented, and generation of contact noise can be prevented. Further, the shaft support member of the transmission assembly can be made compact to reduce the weight and facilitate the assembling work.
In addition, since the regulation guide is provided in the transmission assembly, the distance (or contact pressure) between the cable-like body such as a chain and the regulation guide can be adjusted appropriately when the transmission assembly is assembled. The cord can be properly guided by the guide.
Furthermore, since the regulation guide can be arranged without considering that the mounting boss part contacts the crank part, the dimension in the front-rear direction of the engine can be made more compact.

According to a second aspect of the present invention, in the engine according to the first aspect, the mounting boss portion of the regulation guide is engaged with a groove formed in the shift fork shaft in the transmission assembly, thereby It has become a stopper.

According to the above configuration, the number of members for preventing the shaft member from falling out in the mission assembly can be reduced.

  According to the present invention, in an engine equipped with a cassette-type transmission, it is possible to reduce the size of the engine in the front-rear direction while preventing the generation of contact noise between a chain-like member such as a chain that can cause noise and the crank portion.

  1 to 7 show an example in which the present invention is applied to a parallel two-cylinder engine for a motorcycle, and an embodiment of the present invention will be described based on these drawings.

[Overview of the whole engine]
FIG. 1 is a side view of the crankcase 1 shown with the clutch cover 88 (see FIG. 4) removed. For convenience of explanation, the side on which the cylinder 5 is disposed (vehicle traveling side) is referred to as the “front side of the crankcase 1. In the following description, the left and right direction (axial direction of the crankshaft) when viewed from the rear, that is, when viewed from the rider, is referred to as the “left and right direction” of the crankcase 1.

  In FIG. 1, the crankcase 1 has an upper and lower split structure in which an upper crankcase member 2 and a lower crankcase member 3 are joined by a mating surface S, and a cylinder is formed on the upper surface of the front half of the upper crankcase member 2. Although not shown, a cylinder head and a head cover are sequentially fixed to the upper surface of the cylinder 5. The front half of the crankcase 1 is a crank chamber 10 that houses the crankshaft 7. A balancer shaft 8 is disposed at the front of the crank chamber 10, and a water pump 9 is disposed at the right end of the balancer shaft 8. Is provided. An oil pan 23 is attached to the lower surface of the crankcase 1.

  The latter half of the crankcase 1 is a mission chamber 11 that houses a cassette-type mission assembly M. The cassette-type mission assembly M is shifted to a shaft support member 13 that is separate from the crankcase 1. The input shaft 14 for transmission, the output shaft 15 for speed change, the change drum 16 and the shift fork shaft 17 are supported, and the mission assembly M is inserted into the mission chamber 11 from the right side as a unit. The support member 13 is detachably fixed to a mission mounting wall 41 formed on each crankcase member 2 and 3 by a bolt 43 (only a part is given a reference numeral). A drive sprocket 25 for driving the pump is attached to the right end portion of the input shaft 14 and a multi-plate friction clutch 18 indicated by an imaginary line is attached.

  FIG. 3 is a perspective view of the lower crankcase member 3 as viewed from the upper right rear side, and is applied to a parallel two-cylinder engine. Therefore, the crank chamber 10 is left and right by a partition wall 29 formed at the center in the left-right direction. It is partitioned.

  The left side wall 44 of the lower crankcase member 3 of the mission chamber 11 is formed with a concave portion 45 for supporting an output shaft, a support hole 46 for supporting a change drum, and a bottomed concave portion 47 for supporting a shift fork support shaft. Yes.

  A clutch chamber 12 is formed on the right side of the mission chamber 11 via the mission mounting wall 41. In order to use the lower portion of the mission chamber 11 and the lower portion of the clutch chamber 12 as an oil reservoir, A partition wall 40 a having a height corresponding to the mating surface S is formed between the crank chamber 10 and a partition wall 40 b lower than the mating surface S is formed between the clutch chamber 12 and the crank chamber 10. Yes. In addition, a communication hole 42 is formed at the lower end of the mission mounting wall 41 so as to allow oil to flow between the lower end of the mission chamber 11 and the lower end of the clutch chamber 12. The lower part of the mission chamber 11 can be used simultaneously as an oil reservoir.

  The lower end portion of the partition wall 40a, that is, the front lower end portion of the mission chamber 11, returns from a feed oil pump 50 for pumping oil in the oil reservoir to each lubrication location, and a lubrication location such as a crankshaft. A scavenging pump (recovery oil pump) 51 for collecting the used oil in the oil reservoir is provided side by side on the axis O5 of the common pump shaft 24.

[Feed oil pump and scavenging pump]
FIG. 5 is a sectional development view (VV sectional development view of FIG. 1) of the cassette-type mission M, the oil pump 50, and the scavenging pump 51. The feed oil pump 50 and the oil recovery scavenging pump 51 are all shown in FIG. A trochoid pump is used. A cylindrical outer casing part 70 is formed at the lower end of the partition wall 40a of the lower crankcase member 3, and an intermediate casing member 71 is fitted into the outer casing part 70, and the right-side open end of the intermediate casing member 71 is By closing with the pump cover 72, the casing of the scavenging pump 51 is configured on the right side, and the casing of the oil pump 50 is configured on the left side. Inner rotors 50 a and 51 a arranged in casings of the pumps 50 and 51 are fixed to the common pump shaft 24.

[Cassette type mission assembly]
In FIG. 5, the left end portion of the input shaft 14 of the mission assembly M is supported by a penetrating support hole 108 formed in the left side wall 48 of the upper crankcase member 2 of the mission chamber 11 via a needle bearing 109. ing. The right end portion of the input shaft 14 is supported by a penetrating support hole 117 formed in the shaft support member 13 via a ball bearing 118 and protrudes into the clutch chamber 12. The sprocket 25 and the clutch input gear 18a of the multi-plate friction clutch 18 are fitted, and a clutch housing 18b is fixed to the clutch input gear 18a.

  The left end portion of the output shaft 15 is connected to a pair of upper and lower concave portions 45 formed on the left side wall 48 of the upper crankcase member 2 and the left side wall 44 of the lower crankcase member 3 via the ball bearing 126. The sprocket 127 is supported and protrudes out of the mission chamber 11, and an output sprocket 127 is fixed to the protruding portion. The output sprocket 127 is linked to a sprocket on the rear axle via a rear wheel drive chain (not shown). The right end of the output shaft 15 is supported by a bottomed recess 132 formed in the shaft support member 13 via a needle bearing 133.

  The left end portion of the change drum 16 is supported by the support hole 46 formed in the left side wall 44 of the lower crankcase member 3 of the transmission chamber 11 via the needle bearing 140, and the right end portion of the change drum 16 is the shaft support member. 13 is supported through a ball bearing 142 in a support hole 141 formed in 13.

  The left end portion of each shift fork support shaft 17 is fitted into the bottomed concave portion 47 formed in the left side walls 44 and 48 of the mission chamber 11, and the right end portion is a penetrating shape formed in the shaft support member 13. It is fitted in the fitting hole 143.

[Arrangement of crankshaft, input shaft and output shaft]
FIG. 2 is a left side view of the crankcase 1. The shaft core O 1 of the crankshaft 7, the shaft core O 6 of the balancer shaft 8, and the shaft core O 3 of the output shaft 15 are aligned with the upper and lower crankcase members 2 and 3. Located on the surface S, the axis O2 of the input shaft 14 is located above the mating surface S, and the axis O4 of the change drum 16 is located below the mating surface S. A change shaft 19 having a change pedal is disposed below the change drum 16.

  The input shaft 14 is disposed at the center of the cylinder above the axis O1 of the crankshaft 7 and the first line segment B1 (O1-O2) connecting the axis O2 and the axis O1 of the crankshaft 7. The angle θ1 formed with the line C is set to be an acute angle. Specifically, the angle θ1 is arranged in a range of about 75 ° to 85 °.

  The output shaft 15 is disposed at the second line segment B2 (O2-O3) connecting the axis O3 and the axis O2 of the input shaft 14 and the first line segment B1 (O1-O2). Is set to be an obtuse angle with a downward opening. Specifically, the angle θ2 is arranged in a range of about 100 ° to 120 °.

[Pump drive chain transmission mechanism and chain guide]
In FIG. 1, the winding transmission mechanism is fixed to a drive sprocket 25 mounted at the right end of the input shaft 14 and a common pump shaft 24 such as an oil pump 50 disposed at the front lower end of the transmission chamber 11. A pump drive chain transmission mechanism is configured by winding a pump drive chain 27 between the driven sprocket 26 and the driven sprocket 26. Between the front portion 27a of the chain 27, that is, the portion on the crank chamber 10 side, and the crank portion 203 of the crankshaft 7, a front side regulation guide 200 that regulates the swing of the front side portion 27a of the chain 27 is disposed. The rear regulation guide 201 is also disposed on the rear portion 27b of the chain 27.

  In FIG. 4, which is a sectional view taken along the line IV-IV in FIG. 1, the pump driving chain 27 is disposed at substantially the same position in the left-right direction with respect to the right weight portion 203 a of the right crank portion 203 of the crankshaft 7. Has been. That is, the front side portion 27a of the chain 27 passes substantially right behind the rightmost weight portion 203a.

  In order to prevent the front portion 27a of the chain 27 from coming into contact with the rightmost weight portion 203a of the crankshaft 7, as described above, the front portion 27a of the chain 27 and the right weight portion 203a of the right crank portion 203 Between them, a restriction guide 200 for restricting the runout of the chain is arranged.

  FIG. 6 is a right side view clearly showing the positional relationship between the front regulation guide 200 and the right weight 203 a of the right crank portion 203. The front regulation guide 200 includes a metal guide main body 205 and a rubber guide surface forming member 206. The guide main body 205 is disposed so as to extend in the vertical direction, and the right side of the crankshaft 7 is disposed on the right side. The rubber guide surface forming member 206 is opposed to the outer peripheral end surface of the right weight portion 203a of the crank portion 203 with a predetermined gap D from the rear side. It is stuck by.

  At the upper and lower ends of the metal guide body 205, mounting bosses 205a and 205b projecting backward are integrally formed, and the lower end of the upper mounting boss 205a is above the right end of the shift fork shaft 17. The upper mounting boss portion 205a is engaged with the split groove 17a (see FIG. 5) formed in the half portion, thereby also serving as an axial positioning (preventing slip-off) of the shift fork shaft 17.

  The upper mounting boss portion 205 a is fixed to the shaft support member 13 by a bolt 213, and the lower mounting boss portion 205 b is fixed to the oil pump cover 72 by a bolt 214.

  The rear side regulation guide 201 has basically the same configuration as the front side regulation guide 200, and is attached to the metal guide body 215 and the front surface of the guide body 215 by thermocompression bonding or an adhesive. The upper and lower end portions of the guide main body 215 are integrally formed with mounting boss portions 215a and 215b, respectively. The upper mounting boss portion 215a is integrally formed with the shaft support member 13. The lower mounting boss portion 215 b is fixed to the shaft support member 13 with a bolt 219.

  7 is a cross-sectional view taken along the line VII-VII in FIG. 6. The rubber guide surface forming body 206 of the front regulation guide 200 is positioned between the left and right connecting plates of the chain 27 and contacts the connecting pin portion 27c of the chain 27. Accordingly, the forward deflection of the chain 27 is restricted, and the lateral deflection is also restricted. Further, the upper mounting boss portion 205a of the front side regulation guide 200 is engaged with the split groove 17a of the shift fork support shaft 17 as described above.

[Assembly work of cassette type mission]
The cassette type mission assembly M can be assembled from the right side with respect to the mission chamber 11 in which the upper and lower crankcase members 2 and 3 are coupled.

  In FIG. 5, the transmission assembly M before assembly supports at least the right end portions of the input shaft 14, the output shaft 15, the change drum 16, and the shift fork support shaft 17 on the shaft support member 13. The right end portion of the output shaft 15 is fitted through a needle bearing 133 to a needle shaft outer ring 133a that is fitted in the output shaft support hole 132 of the shaft support member 13 in advance. On the other hand, on the left side wall 48 of the upper crankcase member 2 of the mission chamber 11, the cap 113 and the outer ring 109a of the input shaft needle bearing 109 are fitted into at least the input shaft support hole 108, and the output shaft The bearing 126 for use and the needle bearing 140 for change drum are also fitted.

  The mission assembly M is inserted into the mission chamber 11 as a unit from the right side, and the left end portions of the input shaft 14, the output shaft 15, the change drum 16 and the shift arm support shaft 17 are connected to the corresponding support holes 108, upper and lower A pair of recesses 45, recesses 46, 47, etc. constituting a support hole are fitted directly or directly through the outer ring 109a, bearings 109, 126, 140, etc. The bolt 43 is fixed to the mounting wall 41.

  After assembling the transmission assembly M, the drive sprocket 25 is fitted to the right end portion of the input shaft 14 shown in FIG. 5, and the pump extends from the drive sprocket 25 to the driven sprocket 26 of the common pump shaft 24 for driving the pump. The driving chain 27 is wound around, and then the front and rear chain regulation guides 200 and 201 shown in FIG. 6 are attached.

  In the front chain regulation guide 200, the upper mounting boss portion 205a is fixed to the shaft support member 13 with a bolt 213, and the lower mounting boss portion 205b is fixed to the oil pump cover 72 with a bolt 214. In the rear side regulation guide 201, the upper mounting boss portion 215 a is fixed to the shaft support member 13 with a bolt 218, and the lower mounting boss portion 215 b is also fixed to the shaft support member 13 with a bolt 219.

  After attaching the chain regulation guides 200 and 201 as described above, the clutch 18 of FIG. 5 is attached to the input shaft 14.

  In addition, the said attachment order shows an example and the cassette type mission of this invention is not restrict | limited by the said assembly order.

[Effect of the embodiment of the present invention]
(1) In an engine having a cassette type mission in which the mission assembly M is assembled as a unit in the mission chamber 11, an oil pump 50 disposed at the input shaft 14 of the mission assembly M and the front lower end of the mission chamber 11. Are connected to each other by a chain transmission mechanism including sprockets 25 and 26 and a chain 27, and a front portion (crank chamber 10 side portion) 27a of the chain 27 and a crank portion 203 of the crankshaft 7 are connected to each other. Since the regulation guide 200 that regulates the runout of the chain 27 is disposed between them, the size of the engine in the front-rear direction is reduced, and contact between the chain 27 and the crank portion 203 of the crankshaft 7 is prevented. Generation of contact sounds that can cause noise can be prevented. In addition, the shaft support member 13 of the transmission assembly M can be made compact to reduce weight and facilitate assembly work.

(2) Since the mounting bosses 205a and 205b of the front regulation guide 200 are projected to the rear side (the side opposite to the crank chamber side), it is considered that the mounting bosses 205a and 205b come into contact with the crank portion 203. Therefore, the regulation guide 200 can be arranged at a predetermined position, and the size of the engine in the front-rear direction can be made more compact.

(4) as viewed in the axial direction of the crankshaft 7, a first line segment (O 1 -O 2) connecting the shaft core O 2 of the input shaft 14 for shifting in the mission chamber 11 and the shaft core O 1 of the crankshaft 7; The input shaft 14 is arranged so that the angle θ1 formed with the cylinder center line C above the axis O1 of the crankshaft 7 is an acute angle. The position of the input shaft 14 can be increased, and the oil capacity can be increased.

(5) Since the clutch 18 is attached to the end of the input shaft 14 arranged at a high position as described above, the clutch 18 and the clutch input gear 18a are immersed in the oil while increasing the amount of oil in the oil reservoir. Can be avoided, the stirring resistance can be reduced, and the output can be improved.

(6) The output shaft 15 of the mission chamber 11 is disposed at a position farther from the crankshaft 7 than the input shaft 14, and the first shaft O3 of the output shaft 15 and the shaft core O2 of the input shaft 14 are connected. The output shaft 15 is arranged so that the downward opening angle θ2 formed by the second line segment (O2-O3) and the first line segment (O1-O2) is an obtuse angle. By increasing the position 15, the oil capacity of the oil reservoir can be further increased in the semi-dry sump type engine.

(7) A mission assembly M is configured by supporting the input shaft 14 and the output shaft 15 on the shaft support member 13, and the mission assembly M is detachably mounted as a unit in the mission chamber 11. Therefore, since the input shaft 14 and the output shaft 15 that need to avoid stirring resistance can be assembled to the top of the mission assembly M, a space for arranging mission components that do not normally rotate, such as the change drum 16, is provided. Can be easily secured at the bottom of the mission assembly M. That is, the change drum 16 that does not need to consider the stirring resistance can be easily assembled in a state of being immersed in oil, and the transmission assembly can be made compact without increasing the stirring resistance or the like.

[Other embodiments]
(1) Although the rear side regulation guide 201 for guiding the rear side part 27b of the chain 27 is provided in the above embodiment, the rear side regulation guide 201 can be omitted.

(2) In the above embodiment, the oil pump 50 and the scavenging scavenging pump 51 are driven by the chain transmission mechanism, but a water pump is installed in the transmission chamber 11 as a hydraulic pump driven by the chain transmission mechanism. It can also be set as the structure to arrange.

(3) In the above embodiment, the power for driving the pump is taken out from the input shaft 14, but the pump is driven from the other transmission shaft that rotates constantly in the transmission assembly M through the chain transmission mechanism during operation. It is also possible to adopt a structure for extracting power for use.

(4) Although the above embodiment includes a chain transmission mechanism as a winding transmission mechanism, the present invention is also applied to an engine including a belt transmission mechanism including a pulley and a belt (a cord-like body such as a V belt). Applicable.

Industrial application fields

  In addition to motorcycle engines, the present invention can also be applied to other vehicle engines such as automobiles.

1 is a right side view of a crankcase that is a parallel two-cylinder engine for a motorcycle to which the present invention is applied, with a clutch cover removed. It is a left view of the crankcase of FIG. It is the perspective view which looked at the lower crankcase member of FIG. 1 from the upper right rear. FIG. 4 is a developed sectional view taken along the line IV-IV in FIG. 1. It is a VV cross-section expanded view of FIG. It is a left view of a restriction guide and the crank part of a crankshaft. It is VII-VII sectional drawing of FIG. It is a cross-sectional development view of a conventional example. It is a right view which removes and shows the clutch cover of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crankcase 7 Crankshaft 11 Mission chamber 13 Shaft support member for cassette type missions 14 Input shaft (transmission shaft)
15 Output shaft (transmission shaft)
16 Change drum 17 Shift fork support shaft 18 Multi-plate friction clutch 25 Sprocket 26 Sprocket 27 Chain 41 Mounting wall 50 Oil pump (an example of a hydraulic pump)
51 Scavenging pump (an example of a hydraulic pump)
200 Front side regulation guide 203 Crank part 203a Weight part (constituting part of crank part)
203b Web (component of the crank part)
205a, 205b Mounting boss

Claims (2)

A crank chamber is provided in the front half of the crankcase with the upper and lower split structure, and a mission chamber is provided in the rear half.
In the transmission chamber, a transmission assembly supporting at least the input shaft, the output shaft and the change drum is detachably stored on the shaft support member, and a hydraulic pump is disposed.
The output shaft is disposed on the upper and lower mating surfaces of the crankcase, the input shaft is disposed above the mating surface, the change drum is disposed below the mating surface, and the hydraulic pump is Arranged at the front lower end of the mission chamber,
The input shaft and the hydraulic pump are interlocked and connected by a winding transmission mechanism,
Between the portion on the crank chamber side of the cord-like body of the winding transmission mechanism and the crank part of the crankshaft, a regulation guide that regulates at least forward deflection of the cord-like body is disposed,
The restriction guide has an attachment boss portion projecting to the opposite side to the crank chamber side at an upper portion and a lower portion thereof, and both the attachment boss portions are attached to the shaft support member. Engine. The mounting boss portion of the regulation guide is engaged with a groove formed in the shift fork shaft in the transmission assembly to prevent the shift fork shaft from coming off. Engine.

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