JPS60116825A - Two-cycle engine of motorcycle - Google Patents

Abstract

PURPOSE:To contrive the improvement of engine performance and the compactness of an engine, by fixing a read valve communicating with a suction passage to a crankcase at a specific angle and arranging a cylinder head and a main shaft in a transmission case in specific directions respectively. CONSTITUTION:The upper part of a crankcase 7 is provided with a suction pipe 10 which is connected with an air purifier juxtaposed in a separating method laterally from a fuel tank through a carburetor 9. The suction pipe 10 is fixed through a reed valve 23 and the reed valve 23 is set up so that a suction direction of the same meets at an engle alpha of more than 90 deg. with an axial direction of a cylinder 5. The cylinder 5 of an engine 2 is made almost horizontal and a head part 6 is turned in front of a car body. In addition to the above, a transmission case 8 is provided on the lower part of the crankcase 7 and a main shaft 26 provided within the transmission case 8 is arranged at the lower part of a crankshaft 20 and the front side beyond a vertical line passing through a shaft center of the crankshaft 20. With this construction, the improvement of engine performance and compactness of the whole of the engine are attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a two-stroke engine for a motorcycle, and particularly to a two-stroke engine suitable for a motocross vehicle that runs on rough terrain.

[Prior art]

Motocross vehicles run on rough terrain, so the front fork's extension and retraction strokes are larger than those of regular motorcycles in order to better absorb shock. For this reason, the wheelbase of a motocross vehicle cannot be made too long for the sake of handling stability when the front fork is not compressed very much, and it is necessary to limit the wheelbase to a certain range.

Furthermore, in order to prevent the front wheel from hitting the engine even when the front fork is fully retracted, it is necessary to make the engine compact in the longitudinal direction.

As a countermeasure for this, it is conceivable to arrange the cylinder head toward the front of the vehicle body and place the transmission chamber below the crank chamber, as in Japanese Utility Model Publication No. 43-26102. However, this alone is not sufficient to achieve compactness while maintaining high engine performance.

[Purpose and outline of the invention]

It is an object of the present invention to provide a two-wheeled motor vehicle that can be mounted compactly with ample margin compared to the limited wheelbase of a motorbike while maintaining high engine performance.
Our goal is to provide cycle engines.

To achieve the above object, the present invention is configured such that a reed valve communicating with the intake passage is attached to the crank chamber, and the angle between the intake direction of the reed valve and the axial direction of the cylinder is 90 degrees or more, and the reed valve communicates with the intake passage. the head of which is directed toward the front of the vehicle body, and the transmission chamber is located below the crank chamber;
The main shaft in the transmission chamber is located below the crankshaft and forward of a vertical line passing through the centers of the crankshafts.

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings.

In the figure, 1 is a vehicle body frame, 2 is a two-stroke engine mounted on this vehicle body frame 1, and 3.4 is a front wheel and a rear wheel, respectively. The engine 2 has a cylinder 5 that is horizontal, and a cylinder head 6 that is directed toward the front of the vehicle body. A crank chamber 7 is located behind the cylinder 5, and a mission chamber 8 is disposed below the crank chamber 7.

An intake pipe 1o is attached to the upper part of the crank chamber 7, and is connected via a carburetor 9 to a fuel tank 13 and an air cleaner 14 that is provided separately on the left and right sides. The exhaust pipe 11 is attached to the lower side of the cylinder 5, is inverted from the bottom to the top, and further extends rearward. A drive shaft 12 protrudes from the side of the mission chamber 8, and this drive shaft 12 drives the rear wheel 4 via a chain 17 wound between a sprocket 15 fixed to the end of the shaft and a sprocket 16 on the rear wheel 4 side. do.

As shown in detail in FIG. 2, the cylinder 5 has a piston 1.
8 is fitted, and this piston 18 is connected to the crankshaft 2o via a connecting rod 19. A scavenging boat 21 is provided on the upper side of the cylinder 5, and the scavenging boat 21 communicates with the crank chamber 7. Further, an exhaust boat 22 is provided on the lower side of the side and communicates with the exhaust pipe 11.

The intake pipe 1o connected to the upper surface of the crank chamber 7 is attached via a reed valve 23. This reed valve 23 is
The intake direction and the axial direction of the cylinder 5 are set to form an angle α of 90° or more.

A main shaft 26 and a drive shaft 12 are provided in the mission chamber 8 disposed below the crank chamber 7, and power is transmitted to the main shaft 26 from the crankshaft 20 via a reduction gear 24 and a large reduction gear 25. .

Gear groups 27 and 28 that selectively mesh with each other are supported on the main shaft 26 and the drive shaft 12, respectively.
The power on the main shaft 26 side is selectively decelerated and transmitted to the drive shaft 12 side.

The main shaft 26 located below the crankshaft 20 is located forward of the vertical line passing through the axis of the crankshaft 200, and this arrangement positions the main shaft 26 together with the drive shaft 12 toward the front of the vehicle body. I try to do that. In this arrangement, the triangle formed by connecting the axes of the three axes, the crankshaft 20, the main shaft 26, and the drive shaft 12, has an acute angle A between the axes of the crankshaft 20, and Angles B and C between each axis of the main shaft 26 and drive shaft 12
It is smaller than either.

In the above-mentioned motorcycle engine, since the intake valve 23 for introducing intake air is attached to the crank chamber 7, the thermal influence of the intake air from the cylinder is small, and the filling efficiency can be increased. In addition, since the intake direction of the reed valve 23 forms an angle α of 90° or more with respect to the axis of the cylinder 5, the reed valve 23 is connected to the scavenging boat 21.
The flow resistance of the intake air introduced into the cylinder 5 through the cylinder 5 is reduced, and overall engine performance can be improved.

Furthermore, in the configuration of the intake system, the main shaft 26 of the mission chamber 8 is disposed below the crankshaft 20 and forward of the vertical line passing through the centers of the crankshafts. Shorten the overall length of the kombaku. Therefore, even on motorcycles whose wheelbases are limited to a certain range, such as motocross vehicles, it is possible to mount an engine with sufficient margin, and as shown by the chain lines in Figure 1, the upper and lower parts of the front and rear wheels 3.4 This allows sufficient leeway for movement.

〔Effect of the invention〕

As described above, the present invention is configured such that a reed valve communicating with the intake passage is attached to the crank chamber, and the angle between the intake direction of the reed valve and the axial direction of the cylinder is 90° or more, and the reed valve communicates with the intake passage. The head is directed toward the front of the vehicle, the transmission chamber is placed below the crank chamber, and the main shaft in the transmission chamber is placed below the crankshaft and forward of the vertical line passing through the center of the crankshafts.
It is possible to improve engine performance by reducing the thermal influence of intake air from the cylinder and reducing intake resistance.Furthermore, by shortening the front and rear length of the engine, it is suitable for motorcycles with limited wheelbases. It can also be installed with ease.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing a motocross motorcycle equipped with the engine of the present invention, and FIG. 2 is an enlarged sectional view of the same engine, showing only the main parts. l...Engine, 5...Cylinder, 6...Cylinder head, 7...Crank chamber, 8...Mission chamber, lO...Intake pipe, 20...Crankshaft, 2G...
...Main axis, 12...Drive axis. Agent: Patent Attorney Shin Ogawa − Patent Attorney Ken Noguchi Teru Patent Attorney Kazuhiko Saishita

Claims (1)

[Claims] A reed valve that communicates with the intake passage is installed in the crank chamber, and configured so that the angle between the intake direction of the reed valve and the axial direction of the cylinder is 90 degrees or more, and the head of the cylinder is directed toward the front of the vehicle body. In addition, a transmission chamber is disposed below the crank chamber, and a main shaft in the transmission chamber is disposed below the crankshaft and forward of a vertical line passing through the centers of the crankshafts.
cycle engine.