JP2667452B2 - 4-cycle engine for motorcycles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a four-stroke engine for a motorcycle, and more particularly to a four-stroke engine for a two-cylinder engine in which an intake valve and an exhaust valve are opened and closed by separate camshafts. The present invention relates to narrowing the width of an engine and, consequently, the width of a frame.

[Conventional technology]

In a multi-cylinder engine, when an intake valve and an exhaust valve are driven to open and close by an intake camshaft and an exhaust camshaft, respectively, a chain chamber is formed substantially in the center of the engine, and a camshaft driving chain is arranged in the chain chamber. Generally, a crankshaft and each camshaft are connected (for example, see Japanese Patent Application Laid-Open No. 61-205576).

[Problems to be solved by the invention]

By the way, in the engine in which the above-mentioned chain chamber is provided at the center, the engine width is determined according to the number of cylinders and the width of the chain chamber. When mounted in a state sandwiched between the above, there is a problem that the frame width increases in accordance with the engine width. In this case, in order to ensure an appropriate riding posture, the engine holding portion of the main pipe is widened according to the engine width, and the rear side portion is narrowed to obtain an appropriate knee grip. The main pipe needs to be bent greatly, which is disadvantageous in strength. Therefore, an engine structure capable of reducing the frame width is required.

The present invention has been made in view of the above conventional problems,
It is an object of the present invention to provide a motorcycle four-cycle engine capable of reducing the frame width.

[Means for solving the problem]

According to the present invention, an exhaust camshaft is arranged on the front side and an intake camshaft is arranged on the rear side in the vehicle width direction. When viewed from the side, the intake side of the cylinder head is located between a pair of left and right main pipes of the body frame. In a motorcycle four-stroke engine mounted on a body frame in a sandwiched state, an outer end of a crankshaft and an outer end of the exhaust camshaft protrude outside an engine side wall, and the two protruding portions are connected to each other by a first Connected by a transmission member,
The first transmission member is covered by a cover detachably attached to an engine side wall, and the exhaust camshaft and the intake camshaft are connected by a second transmission member disposed inside the first transmission member. I have.

Here, as the first and second transmission members of the present invention, a general chain, a toothed belt or a gear can be adopted.
As a transmission member, a chain and a belt are advantageous in terms of a relatively large interval between the crankshaft and the camshaft and in terms of weight, and as a second transmission member, a gear is advantageous in terms of reducing the engine width. .

[Action]

In the four-stroke engine according to the present embodiment, the projecting portions of the exhaust camshaft and the crankshaft from the engine side wall are set to the first position.
Since it is connected with the transmission member and covered with the belt cover, this belt cover has a shape that covers only the front half of the cylinder head and cylinder body when viewed from the side, and the engine width of the intake camshaft side portion is There is no belt cover in this part and it is narrower. Therefore, the vehicle body frame of the present invention configured such that the intake camshaft side portion is sandwiched by the main pipes can be narrowed accordingly.

〔Example〕

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

1 to 3 are views for explaining a four-stroke engine for a motorcycle according to 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. A steering fork 2a formed at a front end of a body frame 2 of the motorcycle 1 is provided with a front fork 4 for supporting a front wheel 3 at a lower end. A pair of left and right main pipes 2b, which are rotatably supported left and right and extend obliquely downward and rearward from the steering shaft cylinder 2a, have a rear end supporting a rear wheel 5 at a rear end. The arm 6 is pivotally supported so as to swing up and down. A fuel tank 7 and a seat 8 are mounted on the upper part of the body frame 2.

And the left and right main pipes 2 of the body frame 2
b, 2b, a water-cooled 4-cycle parallel 4-cylinder engine 9
Is suspended and supported. The engine 9 includes a cylinder body 11, a cylinder head 12
And the head cover 13 are sequentially laminated, two upper and lower portions of the rear portion of the crankcase 10 are fixedly supported at the lower end of the rear portion of the main pipe 2b, and the front portion is a down tube.
Suspended by 2c.

In the cylinder body 11, four cylinder liners 11c are press-fitted at predetermined intervals into a cylinder body 11b having a water-cooling jacket 11a. The crankshaft 16 is connected to a crankshaft 16 disposed in the crankcase 10. Although not shown, an intake port and an exhaust port communicate with a combustion chamber 12a formed on the lower surface of the cylinder head 12, and an intake valve,
An exhaust valve 17 is provided to open and close the exhaust valve. An intake camshaft 19 and an exhaust camshaft 20 are arranged on a lifter 18 mounted on the upper end of each valve, and each of the camshafts 19 and 20 is provided with a lower bearing formed on an upper part of the cylinder head 12. , And is rotatably supported by an upper bearing detachably attached to the upper bearing. Each of the camshafts 19 and 20 is an intake camshaft 1 when viewed from the side.
9 is located on the rear side of the vehicle body, and the exhaust camshaft 20 is located on the front side. The head cover 13 is fastened and fixed to the upper bearing by a fixing bolt 13a, and an ignition plug 30 is mounted in each of the combustion chambers 12a so as to pass between the camshafts 19 and 20.

Then, when viewed from behind of the exhaust camshaft 20 (the same applies hereinafter)
The left end portion 20a protrudes outward from the left side wall 12b of the cylinder head 12 and the left side wall 13b of the head cover 13, and a driven sprocket 21 is mounted and fixed to the protruding portion. The left end 16a of the crankshaft 16 projects outward from the left side wall 10a of the crankcase 10, and a drive sprocket 22 is mounted and fixed to the projection. The driving sprocket 22 and the driven sprocket 21 of the exhaust camshaft 20 are connected by a timing belt 23. A belt cover 24 is detachably attached to the left side walls 13b, 12b, 10a of the engine 9 so as to cover the timing belt 23 and the sprockets 21, 22. The belt cover 24 has a two-part structure including an upper half portion 25 and a lower half portion 26. By the way, only the substantially front half of the cylinder head 12 and the like is covered when viewed from the side. The lower half 26 is the belt
It is sized to cover 23 crankcase 10 portions and drive sprocket 22.

A gear chamber 27 is formed at the boundary between the cylinder head 12 and the head cover 13. A drive gear 28 is provided inside the gear chamber 27 of the exhaust cam shaft 20, and a driven gear 2 is provided at the left end 19a of the intake cam shaft 19 located inside the gear chamber 27.
9 are attached and fixed, respectively, and they are in mesh with each other. And from the side, this engine 9
The intake camshaft 19 side portion is sandwiched between the left and right main pipes 2b, 2b of the body frame 2, and the exhaust camshaft 20 side portion, that is, the belt cover 24 side portion is located outside the both main pipes 2b. It is located in.

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

In the engine 9 of the present embodiment, a tamping belt disposed in the center of the conventional engine is disposed outside the engine side wall, and the exhaust camshaft 20 located in front of the engine is disposed.
Only the belt is driven by this belt. Therefore, the belt cover 24 has a shape that covers only the first half of the engine, so that the engine width of the intake camshaft side portion is narrowed by an amount equivalent to a conventional chain chamber. Since the engine 9 is suspended and supported on the body frame 2 in a forwardly inclined state, the narrowed intake camshaft side portions of the cylinder head 12 and the head cover 13 are sandwiched between the left and right main pipes 2b, 2b. It has become. As a result, in this embodiment,
The space between the main pipes 2b can be narrowed by the reduced width of the engine. Also, in this case, there is no need to largely bend the main pipe 2b, which is advantageous in strength.

Further, in the present embodiment, the timing belt 23 is disposed outside the engine side wall, and is covered with a detachable belt cover 24, and the belt cover 24 overlaps with the main pipe 2b when viewed from the side. Since the cover 24 is not provided, the cover 24 can be easily attached and detached, and the maintainability around the belt is greatly improved as compared with the above-mentioned one in which the chain is arranged in the center part of the engine.

〔The invention's effect〕

As described above, according to the four-stroke engine for a motorcycle according to the present invention, the exhaust camshaft arranged on the front side of the engine is driven by the first transmission member arranged outside the engine side wall, and this is covered with the cover. As a result, the engine width on the intake camshaft side can be reduced, and the frame width can be reduced accordingly.

[Brief description of the drawings]

1 to 3 are views for explaining a four-stroke engine for a motorcycle according to an embodiment of the present invention. FIG. 1 is a front sectional view of the engine, and FIG. 2 is a schematic view showing a main part thereof. FIG. 3 is a left side view of a motorcycle equipped with the engine of the embodiment. In the figure, 1 is a motorcycle, 2 is a body frame, 2b is a main pipe, 9 is an engine, 12 is a cylinder head, 13
Is a head cover, 16 is a crankshaft, 16a is an outer end of the crankshaft, 19 is an intake camshaft, 20 is an exhaust camshaft, 20a is an outer end of the exhaust camshaft, 23 is a timing belt (first transmission member), Reference numeral 24 denotes a belt cover, and reference numerals 28 and 29 denote gears (second transmission members).

Claims (1)

(57) [Claims] An exhaust camshaft is arranged on the front side of the vehicle and an intake camshaft is arranged on the rear side in the vehicle width direction. When viewed from the side, the intake side of the cylinder head is located between a pair of left and right main pipes of the body frame. In a motorcycle four-cycle engine mounted on a vehicle body frame with a portion sandwiched, an outer end of a crankshaft and an outer end of the exhaust camshaft are projected outside an engine side wall, and the two projected portions are connected to each other. A first transmission member connected to the first transmission member, the first transmission member being covered by a cover detachably attached to an engine side wall, and an exhaust camshaft and an intake camshaft being disposed inside the first transmission member. A four-stroke engine for a motorcycle, characterized by being connected by members.