JP2670109B2 - engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an engine suitable for a motorcycle, and in particular, shortens the front-rear length of a crankcase to downsize the entire engine, and further, to reduce the distance between the front and rear wheel axles. The present invention relates to an arrangement structure of a crank shaft, a transmission main shaft (main shaft), a transmission auxiliary shaft (drive shaft), etc., which can shorten (hereinafter referred to as a wheel base).

[Conventional technology]

For example, a motorcycle engine generally employs a structure in which a crankshaft and a transmission having a transmission main shaft and an auxiliary shaft are integrally incorporated in a crankcase. In this case, in order to improve the workability of assembling the crankshaft and the transmission, the crankcase is often divided into upper and lower parts, and the crankshaft, the transmission main shaft, and the auxiliary shaft are arranged side by side between the divided surfaces. (See, for example, JP-A-59-79020).

[Problems to be solved by the invention]

As described above, when the crankshaft and the respective shift shafts are arranged side by side between the split surfaces, the front-rear length of the crankcase becomes long, and there is a problem that the entire engine becomes large. Further, the rear arm that pivotally supports the rear wheel is pivotally supported near the engine suspension position of the vehicle body frame. However, if the front-rear length of the engine becomes longer as described above, the wheel base becomes longer accordingly.

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide an engine capable of shortening the front-rear length of the engine for downsizing and shortening the wheel base.

[Means for solving the problem]

According to the present invention, a crankcase is divided into an upper case and a lower case, a crankshaft and a shift sub-width are arranged in parallel between the split surfaces of the two cases, and the shift main shaft is the crankshaft of the upper case or the lower case. And the transmission auxiliary shaft, and the transmission auxiliary shaft and the crankshaft are arranged in parallel with each other in a portion apart from the dividing surface, and the rear arm has a shaft fulcrum on an upper side and a lower case where the transmission main shaft is not disposed. The engine is characterized in that it is formed between the case or the divided surfaces of both cases.

[Action]

In the engine according to the present invention, the transmission main shaft is arranged between the crankshaft and the transmission auxiliary shaft of the upper case or the lower case and in a portion separated from the split surface, so that the transmission auxiliary shaft can be brought closer to the crankshaft. The case, and thus the front-rear length of the engine, is shortened. Therefore, the size of the engine can be reduced, and the wheel base can be shortened. Further, since the transmission main shaft is arranged between the transmission auxiliary shaft and the crankshaft and at a portion separated from the split surface, and the shaft fulcrum of the rear arm is arranged at a position separated downward or upward from the transmission main shaft. Even if it is arranged toward the front, it is less likely to interfere with a large diameter reduction gear or the like mounted on the transmission main shaft, and from this point as well, the engine can be downsized and the wheel base can be shortened. Further, since the pivotal fulcrum of the rear arm is formed on the crankcase itself, the rear arm is pivotally supported at the pivotal fulcrum and the engine is also suspended so that the space between the vehicle body support of the engine and the pivotal fulcrum of the rear arm is increased. Since there is no space in the front-rear direction, the wheel base can be shortened from this point as well.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 4 are views for explaining one embodiment of the present invention.

In the drawing, reference numeral 1 denotes a motorcycle on which the engine of the present embodiment is mounted, and a front fork 4 for supporting a front wheel 3 at a lower end is supported at the front end of a body frame 2 so as to be steerable left and right. A rear arm 6 that pivotally supports the rear wheel 5 at the rear end is pivotally supported vertically at the lower end, and a large fuel tank 7 and a seat 8 are mounted on the upper portion in order from the front. An engine unit 9 is suspended and supported below the front part of the body frame 2.

The engine unit 9 is an air-cooled 4-cycle parallel 2
A cylinder type, a cylinder block 11, a cylinder head 12, and a head cover 13 are stacked on a front portion of an upper surface of a crankcase 10 in a state where the cylinder block 11, the cylinder head 12, and the head cover 13 are inclined forward by approximately 45 degrees with respect to a horizontal plane.

Above the left and right cylinders 11a and 11b of the cylinder block 11, pistons 14a and 14b and concave portions 12 of the cylinder head 12 are provided.
A fuel chamber 14 is formed by a and 12b, and intake and exhaust ports communicating with the combustion chamber 14 have three intake valves 15a and an exhaust valve 1
Two 5b are arranged. A driven sprocket 16c is fixed to the right end of the intake cam shaft 16a and the exhaust cam shaft 16b for the intake valve 15a and the exhaust valve 15b when viewed from the rear of the vehicle (the same applies hereinafter).

The pistons 14a, 14b are connected by connecting rods 17a, 17b to crank arm portions 18a, 18b formed by connecting a pair of webs of the crank shaft 18 with crank pins. A drive sprocket 18c is integrally formed on the right side protrusion of the crankshaft 18, and the sprocket 18c and the camshaft
A cam chain 20 is wound between the driven sprockets 16c of 16a and 16b. This cam chain 20 has a cylinder head 12,
The cylinder block 11 and the upper case 23 are arranged so as to pass through inside the chain case portions 11c, 12c, and 23a that are bulged on the right side walls. A tensioner 60 is disposed behind the cam chain 20, and the chain pressing member 60a of the tensioner 60 has a lower end pivotally supported by a pin 61a. On the outside of the pin 61a, there is a bolt 10a for connecting the upper and lower split type crankcases 10 described later to the pin 61a.
The pin 61a is positioned so as to be substantially orthogonal to the axis of the pin 61a, thereby preventing the pin 61a from coming off.

A pump drive gear 25 is mounted on the right end of the crankshaft 18, and a lubricating oil from an oil tank (not shown) having an oil cooler function is provided below the pump drive gear 25, which is required for the bearings 19a to 19c. A feed pump 26 for supplying the lubricating portion and a scavenging pump 27 for feeding the lubricating oil in the oil pan 28 into the oil tank are arranged in parallel in the front and rear of the vehicle. Further, a water pump 53 for circulating cooling water is arranged in a recessed portion on the right side wall of the crankcase 10 on the front side of the chain case portion 23a. In addition, 29 is an oil strainer, 31 is an oil cleaner, and 30 is a cap, whereby the cleaner chamber 28a has a three-tiered structure of the lower case 24, the oil pan 28, and the cap 30.

The crankcase 10 has an upper / lower split structure divided into upper and lower cases 23 and 24. The split surface A is inclined so that the front side becomes lower when mounted on a vehicle. And the crankshaft 18 is located on the front side between the split surfaces,
The part between the crank arm parts 18a and 18b, and the left and right outer parts are pivotally supported by a central bearing 19c and left and right bearings 19a and 19b formed between the divided surfaces, respectively. A front balancer shaft 47 is provided in front of the crankshaft 18 of the lower case 24 and below the dividing surface A, and a rear balancer shaft 47 is provided in rear of the crankshaft 18 of the upper case 23 and above the dividing surface A. 48 are arranged in parallel with the crank shaft 18, respectively, and a line L connecting the shaft cores of the both balancer shafts 47, 48 is located in front of the shaft core of the crank shaft 18. The front and rear balancer shafts 47 and 48 have a structure in which a support shaft 50 is inserted into a balancer body 49 and a needle bearing 51 is disposed between the two. This rear support shaft
50 is inserted through an insertion hole 23b formed in the side wall of the upper case 23, its tip is supported by a support hole 23c formed in the right side wall of the upper case 23, and its rear end is in the left side wall by a key plate 47b. Fixed. The same applies to the front support shaft. Further, the balancer main body 49 is formed by integrally forming a weight portion 49b at both ends of the cylindrical body 49a and a positioning portion 49c at the center, and the weight portion 49b is provided in each crank arm portion 18a of the crankshaft 18, Located between 18b webs. The positioning portion 49c is disposed below and above the balancer shafts 47, 48 and is inserted into the guide groove of the positioning plate 52 fixed to the crankcase, whereby each balancer shaft 47, 48 is positioned in the axial direction. Also,
A driven gear 47a fixed to the left end of the balancer body 49,
The gear 48a meshes with the balancer gear 21 fixed to the crankshaft 18, and thereby rotates in the direction opposite to the crankshaft 18. Reference numeral 58 denotes a breather cover that forms a breather chamber, and this also serves as a lid member that is formed at the rear portion of the upper surface of the upper case 23 and that opens and closes an opening for assembly work of the rear balancer shaft 48 and the like.

A transmission main shaft (main shaft) 32 is disposed in a portion of the upper case 23 rearward of the crankshaft 18 and above the division surface A, and a portion slightly rearward of the transmission main shaft 32 between the division surfaces. Further, a transmission auxiliary shaft (drive shaft) 35 is arranged. Bearings 32b and 32c are provided on the left and right ends of the transmission main shaft 32, respectively.
Both ends of the speed change counter shaft 35 are axially supported by bearings 35b and 35c, respectively. The right bearing 32c of the transmission main shaft 32 is attached to the right side wall of the upper case 23 via a housing 32d having a larger diameter than the transmission gear 32a mounted on the main shaft 32. Also left bearing 32b
An opening for extracting the main shaft 32 is formed in the portion, and a cap 32e is fitted and mounted in the opening. The oil seal 35d on the outside of the left bearing 35b of the sub shaft 35 and the cap 32e is pressed by a metal plate pressing plate 35e fixed to the left side wall of the crankcase 10.

A wet multi-plate clutch 33 is mounted on the right end of the transmission main shaft 32, and a reduction gear 33b fixed to an outer 33a of the clutch 33 meshes with a reduction small gear 22 fixed to the crankshaft 18. ing. Pressing member 33 of this clutch 33
When viewed from the right side of the vehicle, the operation shaft 33d for moving c is inclined forward from the vertical, and the clutch cable 33e
Is routed to the left side of the vehicle body through the rear side of the cylinder block 11 and without forming a concave portion below, and extends to the left grip of the steering handle. Further, the transmission gears 32a and 35a of the respective stages mounted on the transmission main shaft 32 and the auxiliary shaft 35 are meshed with each other, thereby forming a constant mesh transmission.

The left end of the transmission countershaft 35 protrudes outward from the left side wall of the crankcase 10, and a sprocket 36 for rear wheel drive is mounted on the protruding portion, between the sprocket 36 and the driven sprocket 5a of the rear wheel 5. Has a transmission chain 37 wound.
A chain cover 38 is arranged outside the sprocket 36 so as to cover it. The chain cover 38 is for shielding the chain 37 and the sprocket 36 from splashed mud and the like. Further, the change pedal 39 arranged on the lower side of the drive sprocket 36 and the shift shaft 40 arranged on the upper side have universal joints 41a at both ends, and the outside of the drive sprocket 36 is vertically extended and connected. They are connected by a rod 41b, and the connecting rod 41b is covered with a case cover 42.

Further, a pivot portion (shaft fulcrum) 24a is integrally formed at a rear end portion of the lower case 24 of the crankcase 10.
The left and right outer sides of the pivot portion 24a are provided with the rear arm 6 described above.
Of the vehicle body frame 2 is located outside the front end of the pivot bracket 24a, and a pivot shaft 24h is arranged to pass through the bracket. As a result, the suspension of the engine unit 9 and the pivotal support of the rear arm 6 are provided.

Reference numeral 43 denotes a starter motor, and a drive gear 43b mounted on the output shaft 43a meshes with the start gear 46 mounted on the crankshaft 18 via a one-way clutch via an idle gear 45.

 Next, the operation and effect of this embodiment will be described.

In the present embodiment, the crankcase 10 is divided into upper and lower parts, and the crankshaft 18 and the speed change auxiliary shaft 35 are arranged between the divided surfaces.
Since the transmission main shaft 32 is disposed between the shafts 18 and 35 of the upper case 23 and above the dividing surface A, the transmission auxiliary shaft 35 can be arranged closer to the front side, and the crankcase length can be shortened accordingly. As a result, the whole engine can be downsized,
Wheelbase can be shortened. Further, the transmission main shaft 32 is arranged in a portion separated from the split surface A between the transmission auxiliary shaft 35 and the crankshaft 18, and the shaft fulcrum 24a of the rear arm is arranged at the transmission main shaft 32.
Since the shaft supporting point 24a is provided at a position distant from the lower side, it is difficult to interfere with the large-diameter reduction gear 33b or the like mounted on the transmission main shaft 32 even if the shaft fulcrum 24a is arranged at the front side. The engine can be made smaller and the wheel base can be shortened.

Further, a pivot part 24a that pivotally supports the rear arm 6 is integrally formed with the lower case 24, and the pivot part 24a is formed in the rear arm 6.
Together with the front end of the vehicle body frame 2 support bracket portion 2a
Since there is no space between the engine suspension and the rear arm pivot support, the wheel base can be shortened from this point as well.

Although the transmission main shaft 32 is arranged on the upper case 23 side in the above embodiment, it may be arranged on the lower case 24 side. Further, although the pivot part 24a is formed on the lower case 24, it may be formed on the upper case 23 or between the dividing surfaces of both cases.
The transmission main shaft 32 is arranged at such a position, and the pivot portion 24a
Even when the above is formed, the same effect as that of the above embodiment can be obtained.

〔The invention's effect〕

As described above, according to the engine of the present invention, the crankshaft and the speed change auxiliary shaft are arranged between the upper and lower split surfaces of the crankcase, and the crankshaft and the speed change auxiliary shaft of the upper case or the lower case are separated from the split surface. The transmission main shaft is placed in the part
Since the shaft fulcrum of the rear arm is formed between the case or the split surface on the side where the transmission main shaft of the lower case is not arranged, the crankcase length can be shortened and the engine can be downsized.
This has the effect of shortening the wheel base.

[Brief description of the drawings]

1 to 4 are views for explaining an engine according to an embodiment of the present invention. FIG. 1 is a right side view of a partial cross section thereof, and FIG. 2 is a left side view of a partial cross section thereof. FIG. 3 is a sectional plan development view thereof, and FIG. 4 is a side view of a motorcycle equipped with the engine. In the figure, 10 is a crankcase, 18 is a crankshaft, 2
3, 24 are upper and lower cases, 24a is a pivot part (a pivotal fulcrum of a rear arm), 32 is a main shaft for gear shifting, 35 is a sub shaft for gear shifting, and A is a split surface.

Claims (1)

(57) [Claims] 1. A crankcase is divided into an upper case and a lower case, and a crankshaft and a speed change auxiliary shaft are arranged in parallel between the divided surfaces of the both cases, and a speed change main shaft is the crankshaft of the upper case or the lower case. And the transmission auxiliary shaft, and the transmission auxiliary shaft and the crankshaft are arranged in parallel with each other in a portion apart from the dividing surface, and the rear arm has a shaft fulcrum on an upper side and a lower case where the transmission main shaft is not disposed. An engine formed by the case or between the divided surfaces of both cases.