JPH0125885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motorcycle engine. More specifically, the present invention relates to an improvement of a motorcycle engine in which front and rear cylinders are arranged in a V-shape.

In a motorcycle engine in which the front and rear cylinders are arranged in a V-shape, the exhaust pipe of each cylinder is extended from the front of the cylinder, and the exhaust pipe of the rear cylinder is extended from the rear of the cylinder. There is one that has a divided configuration. In such a configuration, the crankshaft in the crank chamber at the front of the crankcase and the main shaft and subshaft in the transmission chamber at the rear of the crankcase are mounted on the mating surfaces of the upper and lower crankcases. For example, it can be said that the assembling work of these shafts becomes easier, which is preferable. However, if the crankshaft and the main shaft, sub-shaft, etc. of the transmission chamber are mounted on the mating surfaces of the upper and lower crankcases at the same time, the presence of the main shaft, sub-shaft, etc. of the transmission chamber, located at the rear, will be affected. This occupies the installation space for the exhaust pipe that extends from the rear of the rear cylinder of the V-type engine, which means that the exhaust pipe has to be installed with a fairly unreasonable bend, and this also increases exhaust resistance. This has the disadvantage of adversely affecting engine output.

Further, such bending of the exhaust pipe can be achieved by raising the cylinder position, but if the cylinder is raised higher, the center of gravity of the engine moves upward, which is disadvantageous in terms of running stability and the like.

An object of the present invention is to solve the above-mentioned conventional problems, and to arrange the front and rear cylinders in a V-shape, and to divide the crankcase into upper and lower parts, while lowering the overall height and lowering the center of gravity, it is possible to To provide a motorcycle engine whose exhaust pipe can be extended without difficulty without interfering with the crankcase.

To achieve the above object, the present invention arranges the front and rear cylinders in a V-shape, and the exhaust pipe of the front cylinder extends diagonally forward and downward from the front surface of the cylinder, and the exhaust pipe of the rear cylinder extends diagonally rearward and downward from the rear surface of the cylinder. , and a motorcycle engine in which a crankcase is divided into an upper crankcase and a lower crankcase, the front part being a crank chamber and the rear part being a transmission chamber, wherein the front cylinder and the rear cylinder are connected to the upper crankcase. The structure is integrally molded, and only the crankshaft in the crank chamber is mounted on the mating surface of the upper crankcase and the lower crankcase, and the main shaft and sub-shaft in the transmission chamber are mounted on the lower crankcase side. It is characterized by being worn.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to embodiments shown in the drawings.

In FIG. 1, 1 and 2 are the front and rear wheels of a motorcycle, respectively, 3 is a handlebar, 4 is a fuel tank, and 5 is a seat. A four-stroke engine 6 with four front and rear cylinders arranged in a V-shape is mounted below the fuel tank 4. Reference numeral 7 denotes an air cleaner, to which front and rear carburetors 8, 9' are connected, and further connected to the front and rear cylinder heads 9a, 9'a of the engine 6 to reach the combustion chamber. An exhaust pipe 10 is attached to the front surface of the front cylinder head 9a, and after protruding forward, it is bent and extended rearward, and an exhaust pipe 10' is attached to the rear surface of the rear cylinder head 9'a. It extends backwards. Exhaust pipe 10,1
0' joins the chamber 11, then the silencer 12
connected to.

As shown in detail in FIGS. 2 and 3, the cylinder body 9 has cylinders 9b and 9'b arranged in a V
The cylinder heads 9a and 9'a are respectively attached to the upper parts of the cylinder heads 9a and 9'a. The crankcase has a crank chamber at the front and a transmission chamber at the rear, and is divided into upper and lower parts, an upper crankcase 13 and a lower crankcase 14.
It consists of Of these, front and rear cylinders 9b, 9b' are integrally molded in the upper crankcase 13, and the lower part of the cylinder body 9 is also used. The mating surface 15 where the upper crankcase 13 and the lower crankcase 14 face each other is
It has an inclined surface that is low on the front side and becomes high toward the rear side, and a crankshaft 16 is mounted on the front part of this mating surface 15 so as to be held between the upper and lower crankcases 13 and 14. . 17,1
7' is a piston inserted into the front and rear cylinders 9b, 9'b; 18, 18' are these pistons 17, 1;
7' and the crankshaft 16.

On the other hand, a main shaft 19 and a sub-shaft 2 of the transmission chamber are located at the rear inside the lower crankcase 14.
0 is attached. One end of the main shaft 19 and the sub-shaft 20 is directly supported by the side wall of the lower crankcase 14 via a bearing, and the other end is supported by the other side wall of the lower crankcase 14. Mounting plate 21 that can be freely removed
The lower crankcase 14 of the main shaft 19 and the sub-shaft 20 is supported through the mounting plate 21.
This makes the installation work easier. Note that FIG. 2 shows the shafts of the transmission chamber such as the main shaft 19 and the sub-shaft 20 removed, and 19a is the mounting hole of the main shaft 19, 20
22a is a mounting hole for a shift drum (not shown).

According to the above-described structure, the main shaft 19, sub-shaft 20, etc. of the transmission chamber are located in the lower crankcase 14 and below the crankcase, so that the cylinder head 9' of the rear cylinder 9'b This ensures a sufficient space for the exhaust pipe 10' extending rearward from a. Therefore, the exhaust pipe 10' is not subjected to excessive bending, which increases exhaust resistance, and the engine output can be sufficiently ensured.

In addition, since the front and rear cylinders 9b, 9b' are integrally molded into the upper crankcase 13, the height required for the connection structure is greater than a structure in which separate cylinders are connected with bolts. This reduces the overall height and lowers the center of gravity.

In addition, in the above embodiment, the upper crankcase 1
3 and the lower crankcase 14 is an inclined surface that slopes forward and downward, and the crankshaft 16 is attached to the front of this inclined mating surface 15, so that the center of gravity of the machine as a whole is directed downward. It has the advantage of stabilizing the aircraft.

FIGS. 4 and 5 show other embodiments of the present invention.

In this embodiment, the mounting plate 21 is not used to mount the main shaft 19, sub-shaft 20, etc. of the transmission chamber as in the above embodiment, and both ends of the shafts are attached to both side walls of the lower crankcase 14. It is configured to be directly supported via bearings. Further, the mating surface 15 between the upper crankcase 13 and the lower crankcase 14 does not require an attachment allowance for the mounting plate 21, so it is not an inclined surface but is substantially horizontal.

In this embodiment as well, the main shaft 19 and sub-shaft 20 of the transmission chamber are connected to the lower crankcase 1.
4, it will be located below the crankcase, so the rear cylinder 9'b
This ensures sufficient space for the exhaust pipe 10' to extend from the exhaust pipe 10', and an increase in exhaust resistance due to excessive bending of the exhaust pipe does not occur.

As described above, the motorcycle engine according to the present invention has a structure in which the front cylinder and the rear cylinder are integrally molded into the upper crankcase, so that the separate cylinders can be connected by bolts or the like. Compared to the previous version, the overall height of the connecting structure is lower, which lowers the center of gravity of the engine. Furthermore, only the crankshaft in the crank chamber is mounted on the mating surface of the upper and lower crankcases, and the main shaft and sub-shaft in the transmission chamber are mounted on the lower crankcase side, further lowering the center of gravity. At the same time, it is possible to secure a space for the exhaust pipe extending from the rear cylinder, allowing it to extend diagonally rearward and downward without being forced to bend, and thereby preventing a reduction in engine output due to exhaust resistance.

[Brief explanation of drawings]

Fig. 1 is a side view of a motorcycle equipped with an engine according to an embodiment of the present invention, Fig. 2 is an enlarged side view showing the same engine partially in section, and Fig. 3 is a plan view also partially in section. be. FIG. 4 is a partially sectional side view of an engine according to another embodiment of the present invention, and FIG. 5 is a partially sectional plan view of the same engine. 9...Cylinder body, 9a, 9'a...Cylinder head, 9b, 9'b...Cylinder, 10,
10'...exhaust pipe, 13...upper crankcase,
14...Lower crankcase, 15...Matching surface, 1
6...Crankshaft, 19...Main shaft, 20...
Sub-shaft, 21...Mounting plate.

Claims (1)

[Claims] 1 The front and rear cylinders are arranged in a V-shape, with the front cylinder's exhaust pipe extending diagonally forward and downward from the front of the cylinder, and the rear cylinder's exhaust pipe extending diagonally rearward and downward from the rear surface of the cylinder, and the front part is made into a crank chamber. , in a motorcycle engine in which the crankcase with the transmission chamber at the rear is divided into an upper crankcase and a lower crankcase,
The front cylinder and the rear cylinder are integrally molded with the upper crankcase, and only the crankshaft in the crank chamber is mounted on the mating surface of the upper crankcase and the lower crankcase, and the transmission chamber An engine for a motorcycle, characterized in that a main shaft and a sub-shaft are mounted on the lower crankcase side.