JPS6146180Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of a power unit for a motorcycle, particularly a crankcase.

In a power unit for a motorcycle, as shown in FIG. A plane connecting the center lines,
It is conceivable to divide the crankcase, which is integrated with the transmission case, into two parts: an upper case 01 and a lower case 02.

In such a structure, the main shaft 04, which has a heavy clutch unit, must be placed on the same plane as the crankshaft 03 and subshaft 05, whose positions are defined in the layout of the completed vehicle, and the overall power unit The center of gravity cannot be lowered much, and the length of the power unit becomes long.

Furthermore, just for maintenance around the crankshaft 03, the entire crankcase, which is integrated with the transmission case, has to be disassembled.

The present invention was devised in consideration of such problems, and its purpose is to provide a compact power unit for motorcycles with a low center of gravity.

An embodiment of the present invention shown in FIGS. 2 and 3 will be described below.

The power unit 1 consists of a gasoline engine E and a transmission T. The crankcase of the gasoline engine E also serves as a casing for the transmission and is configured as a transmission case 2.

FIG. 2 conceptually shows the internal structure of a power unit 1 having a V-type three-cylinder gasoline engine E, and the power generated by the engine is transferred to the transmission case 2.
The transmission is transmitted from the crankshaft 3 housed in the inner shaft to the primary shaft 6 via the clutch drive gear 7 and the clutch driven gear 8, and then to the secondary drive gear 9 and the secondary driven gear 1.
0 is transmitted to the main shaft 4 via the clutch unit 11, further transmitted to the subshaft 5 having a sprocket 14 via the main shaft gear 12 and subshaft gear 13,
Power is transmitted to the rear wheel through a chain 15 that spans the sprocket 14.

Thus, the transmission case 2 has a first dividing surface D1 that is inclined toward the front side of the vehicle body at a predetermined angle with respect to a surface (hereinafter referred to as a horizontal surface) L passing through the respective center lines of the crankshaft 3 and the subshaft 5. , the transmission case 2 is divided at the second dividing plane D2, and the upper case 1
6, an intermediate case 17, and a lower case 18, and the cases are connected to each other with bolts (not shown) so as to be freely removable.

Further, in the engine E, the pair of left and right cylinders C1 and C3 are tilted forward so that their upper portions are located forward, and the intermediate cylinder C
2 is arranged such that its upper part is inclined downward with respect to the horizontal plane L, the center line of the crankshaft 3 is aligned with the first dividing plane D1 of the transmission case 2, and the crankshaft 3 is It is rotatably supported by an upper case 16 and an intermediate case 17 via bearings (not shown).

Further, the main shaft 4, the counter shaft 5, and the primary shaft 6 of the transmission T are attached to the intermediate case 17 and the lower case 18 with their center lines aligned with the second dividing plane D2 of the transmission case 2. It is rotatably supported via the shaft.

The embodiment shown in FIGS. 2 and 3 is constructed as described above, and the transmission case 2 is divided into three parts, and the center line of the main shaft 4 is connected to the horizontal plane L passing through the crank shaft center line and the sub-shaft center line. Regardless, since it is lowered below the same horizontal plane L, the center of gravity of the entire power unit 1 is lowered, and the steering stability of the vehicle is improved.

Further, by dividing the transmission case 2 into three parts, the distance between the crankshaft 3 and the subshaft 5 can be greatly shortened, and the overall length of the power unit 1 can therefore be shortened.

Further, because of the three-part division, when performing maintenance around the crankshaft 3, it is only necessary to separate the upper case 16 and the intermediate case 17, and there is no need to disassemble the transmission T.

Furthermore, in the above embodiment, since the cylinders C1 and C3 are inclined forward, the height of the power unit 1 is lowered, and sufficient clearance can be secured between the frame and the fuel tank. Easier installation and maintenance.

In the above embodiment, the power unit 1 is of a type in which power is transmitted from the crankshaft 3 to the main shaft 4 via the primary shaft 6, but there is no primary shaft and power is transmitted directly from the crankshaft to the main shaft. It goes without saying that the present invention can also be applied to other types of methods.

As is clear from the description of the embodiments above, according to the configuration of the present invention, the center of gravity of the entire power unit can be lowered and the longitudinal length can be shortened, thereby improving the handling stability of the vehicle. , it is possible to reduce work costs by improving maintainability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of a power unit, FIG. 2 is a conceptual development view of a power unit according to an embodiment of the present invention, and FIG. 3 is a cutaway side view of the same essential parts. 1...Power unit, 2...Transmission case, 3
...Crankshaft, 4...Main shaft, 5...Subshaft, 6...
...Primary shaft, 7...Clutch drive gear, 8...Clutch driven gear, 9...Secondary drive gear, 10...Secondary driven gear, 11...Clutch unit, 12...
Main shaft gear, 13... Subshaft gear, 14... Sprocket, 15... Chain, 16... Upper case,
17...middle case, 18...lower case, C
1, C2, C3...Cylinder, D1...First dividing surface, D2...Second dividing surface, E...Gasoline engine, L...Horizontal surface, T...Transmission.

Claims (1)

[Scope of utility model registration request] In a power unit for a motorcycle in which a crankcase is integrally formed with a transmission case, the crankshaft is sandwiched between an upper case and an intermediate case, and a main shaft and a subshaft of the transmission are sandwiched between the intermediate case and the lower case. A power unit for a motorcycle characterized by: