JPH025748A - Engine of motorcycle - Google Patents

Abstract

PURPOSE:To facilitate the assembling of a counter shaft and a drive shaft and improve the rigidity of a bearing portion by dividing a lower crankcase right and left. CONSTITUTION:A crankcase 10 is divided in an upper crankcase 28 and a lower crankcase 29 with a plane passing through the axes of both crankshafts 15a, 15b as an up-down dividing face 27. Further, the lower crankcase 29 is divided in right/left divided lower crankcases 31, 32 with a plane intersecting to the axes of the crankshafts 15a, 15b as a right-left dividing face 30. Further, both end portions of a counter shaft 17 and a drive shaft 21 are rotatably supported by the side walls 31a, 32a of the divided lower crankcases 31, 32. Thereby, the rotatable support of the counter shaft 17 and drive shaft 21 can be stabilized, reducing mechanical losses, and reducing the gear trouble of a transmission gear mechanism while lowering gear noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an engine for a two-wheeled motor vehicle that is configured into a multi-cylinder structure using two crankshafts.

(Prior Art) For example, in a square four engine mounted on a two-wheeled motor vehicle, a front crankshaft of a front row cylinder and a rear crankshaft of a rear row cylinder are provided in parallel.

Primary drive gears are respectively supported on the front and rear crankshafts, and mesh with a common primary driven gear on the countershaft. A mission gear-like structure is interposed between the counter shaft and the drive shaft arranged in parallel with the counter shaft.

The outer shell of such an engine is assembled by overlapping a crankcase, cylinder block, cylinder head, and head cover. Because the crankshaft is mounted inside the crankcase, it is divided into two halves, upper and lower, along a plane that passes through the axes of both crankshafts.When joining the upper and lower crankcases, both crankshafts are sandwiched between the mating surfaces. It is pivoted with.

However, since the countershaft is interlocked with the two crankshafts by gears as described above, it is impossible to arrange the countershaft together with the drive shaft on the above mating surface, and the shaft is mounted inside the lower crankcase. .

In this case, if the lower crankcase is further divided along a plane passing through the wheel centers of the counter shaft and the drive shaft, it will be easier to support both wheels, but this mating surface will cross the mating surface at an acute angle, making the strength unstable.

Therefore, conventionally one side of the lower crankcase was opened,
A cassette-type transmission was used that supported both wheels with side covers attached. However, the cassette type had the problem that the bearing part lacked rigidity and was prone to gear pull and gear noise.

(Problems to be Solved by the Invention) As described above, in a multi-cylinder engine configured with two crankshafts, the crankcase is divided into upper and lower halves.
If the crankshaft is pivotally supported on the mating surface and the transmission gear mechanism is a cassette-type mechanism in which the crankshaft is pivotally supported in the lower crankcase, the rigidity of the bearing part is insufficient and gear noise may occur. In view of this problem, the present invention has developed a motorcycle engine that does not use a cassette type, has a crankcase that is easy to assemble, and has increased rigidity in the bearings of the countershaft and driveshaft. The purpose is to provide.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the engine of the motorcycle of the present invention is a multi-cylinder engine constituted by two crankshafts arranged in parallel in the front and rear, is divided into upper and lower parts along a plane that passes through the axes of the two crankshafts, and the crank case is divided into left and right parts perpendicular to the axes of the two crankshafts, and the countershaft and drive that make up the mission gear mechanism The shaft is mounted on both side walls of the lower crankcase.

(Function) Since the lower crankcase is divided into left and right parts in this way, it is easy to assemble the countershaft and drive shaft that are mounted inside the lower crankcase, and the rigidity of both side walls, that is, the bearing part, is increased. Made with high quality.

Therefore, the shaft support of both shafts is stabilized, and gear trouble and gear noise of the mission gear mechanism interposed between the two shafts are reduced.

(Example) DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings showing embodiments of the present invention will be explained below.

In FIG. 3, the engine unit 1 mounted on this two-wheeled motor vehicle is assembled as a main frame. That is, a front wheel 4 is steerably supported by a steering head 3 at the front end of a box-shaped frame 2 connected to the front upper part, and a rear wheel 6 is supported by the rear end of a swing arm 5 that is pivotally supported at the front end. Also, a seat 8 and a fuel tank 9 are supported by a seat rail 7 connected to the rear upper part.

As shown in FIG. 2, the engine unit 1 includes a crankcase 10, a cylinder block 11, a cylinder head 12, and a head cover 13, and the frame 2 serves as an air cleaner case with a built-in carburetor 14.

The engine type is a square 4 multi-cylinder 4-stroke engine with four cylinders arranged in a rectangular arrangement, with a front crankshaft 15a belonging to the front row of cylinders and a rear crankshaft 15b belonging to the backward row of cylinders arranged one after the other.

Primary drive gears 16a and 16b are fixed to both crankshafts 15a and 15b, and mesh with a primary driven gear 18 pivotally supported by a countershaft 17 at the same time. A friction clutch 19 is interposed between the counter shaft 17 and the primary driven gear 18. Furthermore, a drive gear group 20 is mounted on the counter shaft 17 and meshes with a driven gear group 22 on a drive shaft 21 arranged in parallel to form a mission gear mechanism.

A cam chain T23 is formed on the side of the engine unit 1, and within this cam chain chamber 23, a cam drive sprocket gear 24 on the rear crankshaft 15b and a cylinder head 1 are connected to each other.
A cam chain 26 is suspended between a cam driven sprocket 1=a 25 which is supported by a cam chain 25 and drives a valve camshaft.

Next, as shown in FIG. 1, the crankcase 10 is
It is divided into an upper crankcase 28 and a lower crankcase 29 with a plane passing through the axes of both cranks @ 15a and 15b as an upper and lower dividing plane 27.
9 is divided into left and right divided lower crankcases 31 and 32 with a plane perpendicular to the axes of the crankshafts 15a and 15b as a left and right dividing plane 30, and these parts are combined.

The crankshafts 15a and 15b are supported across the upper and lower dividing surface 27, and the countershaft 17 and the drive shaft 21
Both ends of the split lower crankcase 31, 32
The shaft is mounted straddling the l walls 31a and 32a. Counter axis 1
7 protrudes from the side wall 32a, the primary driven gear 18 and one friction clutch are mounted on the protruding end 17a, and a clutch cover 33 is attached.

Since the split lower crankcases 31 and 32 are both formed into a bowl shape, the side walls 31a and 32a have high rigidity. Therefore, the shaft support of the counter shaft 17 and the drive shaft 21 is stabilized,
Mechanical loss is small, and there is less gear trouble and gear noise in the mission gear mechanism.

〔Effect of the invention〕

As described above, in the motorcycle engine according to the present invention, the crankcase is divided into upper and lower parts by a plane passing through the axes of the two crankshafts, and the lower crankcase is divided into upper and lower parts by a plane perpendicular to the axes of the crankshafts. It is further divided into left and right parts, which increases the rigidity of the shaft support of the counter shaft and drive shaft, which has the effect of stabilizing the operation of the mission gear mechanism.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a crankcase showing an embodiment of the present invention, Fig. 2 is a side view of an engine unit equipped with the crankcase shown in Fig. 1, and Fig. 3 is an engine unit shown in Fig. 2. FIG. 2 is a side view of a two-wheeled motor vehicle equipped with. DESCRIPTION OF SYMBOLS 1... Engine unit, 10... Crank case, 15... Front crankshaft, 15b... Rear crankshaft, 17... Counter shaft, 21... Drive shaft, 27
...Upper and lower dividing surface, 28...Upper crankcase, 29...Lower crankcase, 30...Left and right dividing surface, 31°32...Divided lower crankcase, 31a
, 32a...side wall.

Claims (1)

[Claims] It is a multi-cylinder engine composed of two crankshafts arranged in parallel in the front and rear, and the crankcase is divided into upper and lower parts along a plane passing through the axes of the two crankshafts, and the lower crankcase is connected to the crankshaft. An engine for a two-wheeled motor vehicle, characterized in that the engine is divided into left and right parts on a plane perpendicular to the shaft axis, and a counter shaft and a drive shaft forming a mission gear mechanism are mounted astride both side walls of the lower crankcase. .