JPH01233189A - Engine unit for motorcycle - Google Patents

Abstract

PURPOSE:To achieve the miniaturization of an engine unit and the enhancement in the mountability of the engine by inserting a main shaft into a crankcase through a window having been provided in the half-body of the crankcase, and supporting the main shaft by the cover plate of the window, so that the longitudinal length of the crankcase on the division surfaces can be reduced. CONSTITUTION:The division surfaces 34c of a crankcase 32c capable of being divided into upper and lower halves are inclined so as to be lower in its front side, and both a crankshaft 36 and a auxiliary shaft 42 are held between the division surfaces 32c. And in the lower half body 60 of the crankcase, a circular window 62 is formed on the right side side-wall 60a, and a main shaft 40 is inserted from the window 62 in such a condition as the speed change gears have been assembled, and is supported in such a condition as the cover plate 66 of the window 62 has been penetrated. Then, the rotation of the crankshaft 36 is transmitted to the main shaft 40 via a chain 70 and a clutch 68, and further is speed-changed by a transmission 38, and thereafter is transmitted to rear wheels via an auxiliary shaft 42, an output shaft 76, and a shaft-drive type rear wheel driving system. In the case of a V-type engine, the main shaft 40 can be arranged in a lower position, so that the rear bank 54 can be strongly inclined rearward, thus the whole unit 30c (not shown) can be suitably miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine unit for a motorcycle in which a transmission is housed in a vertically split crankcase.

(Background of the Invention) In motorcycles, an engine unit is generally used in which a transmission is housed in a crankcase and an engine and a transmission are integrated. There is an extremely strong demand for miniaturization of this engine unit when the engine mounting space is severely limited, such as in a motorcycle, and it is particularly desirable to reduce the dimensions of the engine in the longitudinal direction.

FIG. 1 is a side view showing a conventional engine unit having a horizontal rank case split surface. In this figure, reference numeral 10 denotes a frame, which includes a subframe 12 made of sheet metal, a seat pillar tube 14, a seat rail 16, and a pack tube 18. Seat pillar tube 1
4, the seat rail 16, and the pack tube 18 form a substantially triangular side surface, and a pivot bearing 20 is provided at the lower apex of this triangle. Reference numeral 22 denotes a rear arm, whose front end is rotatably attached to a pivot bearing 20 by a pivot shaft 24, and whose rear end holds a rear wheel 26. The rear arm 22 and the rear wheel 26 are mounted on the frame 1o so that they can be vertically swung by a cushion unit (not shown).
A so-called swing arm type rear wheel suspension system is formed.

30 is an engine unit, and its crankcase 3
2 has a horizontal split surface 34, and a crankshaft 36, and a main shaft 40 and a counter shaft 42 of a transmission 38 are held in this order laterally on this split surface 34. A chain 48 is wound between a sprocket 44 fixed to the shaft end of the subshaft 42 and a sprocket 46 of the rear wheel 26, forming a chain-type rear wheel drive system.

In this way, when the crankshaft 36, main shaft 40, and subshaft 42 are held between the split surfaces 34 of the upper and lower split crankcase 32, there is a problem in that the longitudinal dimension of the crankcase 32 becomes large.

Therefore, the inventor considered the configuration shown in FIG. 2 as a first improvement example. That is, the split surface 34A of the crankcase 32A of the engine unit 30A is inclined so that its front part is lower, and the crankshaft 36 and the main shaft 4 are attached to this split surface 34A.
0, while holding the counter shaft 42, move the counter shaft 42 to the pivot shaft 2
The height is approximately the same as that of 4. In this figure, the same parts as in FIG. 1 are given the same reference numerals.

However, even with the engine shown in FIG. 2, the front and rear dimensions of the engine on the crankcase split plane were not reduced, resulting in the same problem as the engine shown in FIG. 1.

Therefore, the inventor further considered the configuration shown in FIG. 3 as a second improvement example. That is, the split surface 34B of the crankcase 32B of the engine units 1 to 30B is made horizontal, and while the crankshaft 36 and the main shaft 40 are held on this split surface, the subshaft 4
2 is held in the upper case 50 of the crankcase 32B,
This sub-shaft 42 is arranged to be approximately at the same height as the pivot shaft 24. However, in this case, the secondary shaft 42 must be inserted into the upper case half 50 from the side. The diameter of the speed change gear provided on the subshaft 42 is generally larger than the diameter of the gear provided on the main shaft 4o. For this reason, it became necessary to form a large-diameter opening in the upper case half 50, which was found to be extremely disadvantageous when considering the strength of the crankcase 32B.

(Object of the Invention) The present invention has been made in view of the above circumstances, and it is possible to reduce the dimensions of the engine unit in the front and rear directions, thereby improving the ease of mounting it on the vehicle body, and also in terms of ensuring the strength of the crankcase. An object of the present invention is to provide a preferable motorcycle engine unit.

(Structure of the Invention) According to the present invention, the object is to provide a transmission housed in a vertically split crankcase, and a main shaft of the transmission is provided behind a crankshaft disposed laterally within the crankcase. and in which subshafts are arranged in parallel, the crankshaft and subshaft are held between the split surfaces of the crankcase, and the largest diameter gear on the main shaft is attached to either the upper or lower case half of the crankcase. A window with a slightly larger diameter is opened, and the main shaft inserted into the crankcase from the side through this window is pivotally supported by a cover plate that closes this window, and a clutch is attached to the shaft end of the main shaft on the cover plate side. This is achieved by a motorcycle engine unit characterized by the following.

The present invention will be described in detail below based on the illustrated embodiments.

(Embodiment) Fig. 4 It is a side view showing an embodiment of the present invention, and Fig. 5 is a sectional view taken along the line v-v. In this embodiment, an engine unit 3'OC with four cylinders in the front and rear is used, and a shaft drive type rear wheel drive system is employed. The split surface 34C of the vertically split crankcase 32G is inclined so that its front part is lower, and the crankshaft 36 is inserted between the split surface 32C.
and the subshaft 42 are held. 52 and 54 are a front bank and a rear bank, respectively, and each bank 52 and 54 is provided with an overhead camshaft 56 (only one is shown in FIG. 5). 58 is a flywheel magneto attached to the left end of the crankshaft 36.

The main shaft 40 is the lower case half 6 of the crankcase 32C.
It is held at 0. The lower case half 60 has a circular window 62 formed in its right side wall 60a (FIG. 5). The diameter of this window 62 is slightly larger than the largest diameter gear 64 among the speed change gears provided on the main shaft 40. The main shaft 40 is inserted through this window 62 with the speed change gear assembled,
Its tip (left end) is held by the side wall 60b of the lower case half 60. In this state, a cover plate 66 is attached to the window 62, and the main shaft 40 is held in a state passing through the cover plate 66.

A wet multi-disc clutch 68 is mounted on the right end of the main shaft 40, and the rotation of the crankshaft 36 is transmitted to the clutch housing by a silent chain 70.

The gear 7 with the largest diameter among the speed change gears provided on the subshaft 42
2 is larger than the maximum diameter gear 64 of the main shaft 40, as is clear from FIG. From the left end of the countershaft 42, the bevel gear 74
The rotation of the subshaft 42 is transmitted to the output shaft 76 via.

According to this embodiment, the rotation of the crankshaft 36 is controlled by the chain 7.
0, is transmitted to the main shaft 40 via the clutch 68, and after being changed in speed by the transmission 38, is transmitted to the rear wheels via the subshaft 42, the output shaft 76, and a known shaft drive type rear wheel drive system.

In addition, in the case of a ■ type engine as in this embodiment, the main shaft 40
Since the angle becomes lower, the rear bank 54 can be strongly tilted rearward, which is suitable for downsizing the entire unit 30G.

FIG. 6 is a side view showing another embodiment of the present invention. In this embodiment, a horizontal in-line multi-cylinder engine unit 30D
The split surface 34D of the vertically split crankcase 32D is inclined so that the front part thereof is lower. The crankshaft 36 and the subshaft 42 are held between the split surfaces 34D, and the main shaft 40 is held in the lower case half 78 of the crankcase 32D. Further, the countershaft 42 is disposed at a height between the pivot shaft 24 and the track. In this figure, the same parts as in the above-mentioned Figs. 1 to 3 are given the same reference numerals, so their description will not be repeated.

(Effects of the Invention) As described above, the present invention provides a window in the case half at a position other than the split surface of the crankcase where the main shaft is divided into upper and lower parts, and through this window, the main shaft with gears attached is inserted into the crankcase from the side. Since the main shaft is pivotally supported by the cover plate that is inserted and closes this window, the length of the engine unit in the front-rear direction on the crankcase split surface can be reduced, making it possible to downsize the engine unit. This improves the ease with which the engine can be mounted on the vehicle body.

Furthermore, since the gear for changing gears with the largest diameter of the main shaft is smaller than the gear with the largest diameter of the sub-shaft, the window for inserting the main shaft into the case half can also be smaller. Therefore, it is convenient for ensuring the rigidity and strength of the crankcase.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an example of engine arrangement when a conventional engine unit is used, FIGS. 2 and 3 are side views showing second and third improved examples, and FIG. FIG. 5 is a side view showing the embodiment, FIG. 5 is a sectional view taken along line v-v, and FIG. 6 is a side view of another embodiment. 30.30A-30D...engine unit, 32.
32A~32D...Crankcase, 34.34A~
34D... Split surface, 36... Crankshaft, 38... Transmission, 40... Main shaft, 42... Subshaft, 60.78... Lower case, 62... Window, 66... Lid plate. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Scope of Claims] A transmission is provided with a transmission housed in a vertically divided crankcase, and a main shaft and a subshaft of the transmission are sequentially arranged in parallel behind a crankshaft disposed laterally within the crankcase. The crankshaft and subshaft are held between the split surfaces of the crankcase, and a window with a diameter slightly larger than the largest diameter gear on the main shaft is opened in either the upper or lower case half of the crankcase. The motorcycle is characterized in that the main shaft inserted into the crankcase from the side through the window is pivotally supported by a cover plate that closes the window, and a clutch is attached to the shaft end of the main shaft on the cover plate side. engine unit.