JPH0330699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a V-type two-cylinder engine suitable for motorcycles, agricultural machinery (particularly tractors, lawn mowers), and the like.

(Prior Art) Generally, when a V-type two-cylinder engine is mounted on a two-wheeled motor vehicle, a horizontal structure as shown in FIG. 1 or a vertical structure as shown in FIG. 2 is conventionally adopted.

In FIG. 1, an engine 1 and a vehicle body frame 2 are illustrated from the left side of the vehicle body. In the structure shown in FIG. 1, the crankshaft 3 extends in the lateral direction (vehicle width direction), and the two cylinders 4 and 5 protrude forward and upward, and rearward and upward, respectively, with respect to the crankshaft 3. However, although this structure has the advantage of narrowing the engine width, on the other hand, the length L of the entire cylinder in the longitudinal direction becomes large, making it difficult to mount it on the frame 2. Further, a seat (not shown) is arranged above and behind the engine 1, but in order to lower the seat height, the wheelbase must be lengthened. Furthermore, when the cooling method is air cooling, it is difficult to cool the rear cylinder 5.

FIG. 2 is a diagram of the engine 10 seen from the front of the vehicle body. In this structure, the crankshaft 11 extends in the vertical direction (the front and back direction of the vehicle body), and the two cylinders 12,
13 protrudes upward and on both left and right sides of the crankshaft 11. Therefore, in the case shown in FIG. 2, the cylinders 12 and 13 protrude from both sides of the fuel tank 14 and get in the way of the driver's feet. Further, the torque roll shaft extends in the longitudinal direction of the vehicle body, and a torque reaction occurs in a direction that twists the vehicle body, making the driver sensitive to engine vibrations and feeling uncomfortable.

(Object of the Invention) The object of the present invention is to improve the layout of a V-type two-cylinder engine and to solve the above-mentioned conventional problems.

(Structure of the Invention) The present invention is a V-type two-cylinder engine mounted on the body of a vehicle, in which the crankshaft is arranged with an inclination in the range of about 45 degrees to about 90 degrees with respect to the horizontal direction. The cylinders are located at positions shifted toward the front of the vehicle body with respect to the crankshaft, and at positions on both sides of the vehicle body in the left-right direction with respect to a central plane extending in the longitudinal direction of the vehicle body.

(Example) FIG. 3 is a partially cutaway left side schematic diagram of the engine and the main parts of the vehicle body, and FIG. 4 is a schematic cross-sectional diagram along the side of FIG. 3. In FIG. 3, the crankshaft 21 of the V-type two-cylinder engine 20 is disposed in a substantially vertical position inclined at an angle D of 60° to 70° with respect to the horizontal direction, for example. The two sets of cylinders 22, 23 and cylinder heads 24, 25 are perpendicular to the crankshaft 21 and protrude toward the front of the vehicle body, and as shown in FIG. distributed symmetrically. The down tube 19 extends vertically between the cylinders 22 and 23 on both sides.

As shown in FIG. 3, a generator 26 is attached to the lower end of the crankshaft 21, and a transmission 27 is provided behind the crankshaft 21. The transmission 27 transmits the output from the crankshaft 21 to the engine sprocket 30 via a clutch 28, a transmission gear mechanism (not shown), and a bevel gear mechanism 29. The sprocket 30 is connected to a rear wheel sprocket (not shown) via a chain 31. The input shaft 32 and output shaft 33 of the transmission 27 are connected to the crankshaft 2.
It extends parallel to 1.

A caplet 40 and an air cleaner 41 are provided above the engine 20, and a fuel tank 42 is provided above them. 43 is a seat, 44 is a front fender, and 45 is an exhaust pipe.

(Effects of the Invention) According to the above structure, there is
4 and 25), the wheelbase can be shortened.

Both cylinders 22, 23 and cylinder head 2
4 and 25 protrude forward and on both the left and right sides, so that the entire area is sufficiently exposed to cooling air. Therefore, an air-cooled engine with high cooling performance can be constructed.

Cylinders 22, 23 and cylinder heads 24, 2
5 protrudes from the front or side of the front end of the fuel tank 42, so that they do not hit the driver's feet. Therefore, the optimum riding position can be easily taken.

Since the overall height of the engine 20 can be reduced, a wide space can be formed between the engine 20 and the fuel tank 42. Therefore, the layout of the capletor 40 and the air cleaner 41 in the space becomes free and easy, and the capletor 40 and the air cleaner 41 can be installed so as to increase the intake efficiency, thereby increasing the output of the engine.

Since the torque roll axis is in a substantially vertical direction, the driver becomes less sensitive to torque reactions and the driving feeling is improved.

Since the overall height of the engine 20 is lower, the seat 4
3 can be installed lower, and of course the wheelbase can be kept short even in that case.

Cylinders 22, 23 and cylinder heads 24, 2
5 protrudes forward, it is possible to configure an engine with excellent serviceability around the cylinder head and cylinders, such as adjusting valve clearance.

As in the illustrated embodiment, the inclination angle D of the crankshaft 21
When the angle is 60° to 70°, the cylinder head 24, 25
protrudes obliquely upward and occupies a relatively high position. Therefore, even if the vehicle body is tilted to the left or right, the cylinder heads 24, 25 can be reliably prevented from coming into contact with the road surface.

(Modified example) The inclination angle D of the crankshaft 21 is set to 90 degrees or approximately 90 degrees, and the cylinders 22, 23, cylinder head 24,
25 can also be made to incline with respect to the crankshaft 21 and protrude obliquely upward.

According to the present invention, the inclination angle D of the crankshaft 21 can be arbitrarily set within the range of approximately 90° to approximately 45° (approximately vertical range).

[Brief explanation of the drawing]

Fig. 1 is a schematic left side view of the conventional example, Fig. 2 is a schematic front view of another conventional example, Fig. 3 is a partially cutaway schematic left side view of the embodiment of the present invention, and Fig. 4 is a - cross section of Fig. 3. This is a schematic diagram. 20...engine, 21...crankshaft,
22, 23...Cylinder.

Claims (1)

[Claims] 1 A V-type two-cylinder engine mounted on the body of a vehicle, which is arranged with the crankshaft inclined at an angle of about 45° to about 90° with respect to the horizontal direction, and the two cylinders are mounted on the crankshaft. A V-type two-cylinder engine is located at a position shifted toward the front of the vehicle body, and the center of the vehicle body is located on both sides of the vehicle body in the left-right direction with respect to a center plane extending in the longitudinal direction of the vehicle body.