JP2560426B2 - Motorcycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to an engine of a motorcycle having a multi-cylinder structure with two crankshafts. In a square 4 engine mounted on a wheeled vehicle, a front crankshaft of a front row cylinder and a rear crankshaft of a rear row cylinder axis are provided in parallel.

Primary drive gears are axially supported by the front and rear crank shafts, respectively, and mesh with a common primary driven gear on the counter shaft. A transmission gear mechanism 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 stacking a crankcase, a cylinder block, a cylinder head and a head cover. Since the crankcase has the crankshaft mounted inside, it is divided into two parts vertically on the plane that passes through the axes of both crankshafts. Support with.

However, since the counter shaft is interlocked with the two crank shafts by a gear as described above, it is impossible to arrange the counter shaft on the mating surface together with the drive shaft, and the counter shaft is mounted in the lower crank case. .

In this case, if the lower crankcase is further divided by a plane that passes through the center axes of the counter shaft and the drive shaft, both shafts can be easily supported, but this mating surface crosses the mating surface at an acute angle and becomes unstable in strength. .

Therefore, conventionally, a cassette type mission has been used in which one side of the lower crankcase is opened and a side cover is attached to support both shafts. However, the cassette type has a problem in that the rigidity of the bearing portion is insufficient, which is likely to cause gear troubles and gear noise.

(Problems to be Solved by the Invention) As described above, in a multi-cylinder engine including two crankshafts, the crankcase is divided into upper and lower halves, and the crankshaft is axially supported by the mating surfaces thereof. In the case where the mission gear mechanism axially supported in the case is of a cassette type, there is a problem that the rigidity of the bearing portion is insufficient and gear noise and the like are likely to occur. It is an object of the present invention to provide an engine of a motorcycle, which is not adopted, is easy to assemble, and has a crankcase in which the rigidity of the bearing portions of the counter shaft and the drive shaft is increased.

[Structure of Invention]

(Means for Solving the Problem) In order to achieve the above object, an engine of a motorcycle according to the present invention is a multi-cylinder engine including two crankshafts arranged in front and rear, and a crankcase. Is vertically divided in a plane passing through the axes of the two crankshafts, and its lower crankcase is divided into left and right in a plane orthogonal to the crankshafts, thereby forming a transmission gear mechanism and a counter shaft. The shaft is constructed so as to span the both side walls of the lower crankcase.

(Operation) Since the lower crankcase is divided into the left and right in this way, the counter shaft and the drive shaft mounted on the lower crankcase can be easily assembled, and the rigidity of both side walls, that is, the bearing portion can be increased. It

Therefore, the pivotal support of both shafts is stabilized, and gear troubles and gear noises of the transmission gear mechanism interposed between both shafts are reduced.

(Embodiment) A description will be given below of a drawing showing an embodiment of the present invention.

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

As shown in FIG. 2, the engine unit 1 includes a crankcase 10, a cylinder block 11, and a cylinder head 1.
2. The head cover 13 is included, and the frame 2 is an air cleaner case having a carburetor 14 built therein.

The engine type is a square 4-cylinder 4-cycle engine in which four cylinders are arranged in a square, and a front crankshaft 15a belonging to a front row cylinder and a rear crankshaft 15b belonging to a rear row cylinder are arranged in front and rear.

Primary drive gear 16a, 1 on both shafts 15a, 15b
6b is fixed and simultaneously meshes with a primary driven gear 18, which is axially supported by a counter shaft 17. A friction clutch 19 is interposed between the counter shaft 17 and the primary driven gear 18. Further, 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 transmission gear mechanism.

A cam chain chamber 23 is formed on the side surface of the engine unit 1. In the cam chain chamber 23, a cam driven sprocket gear that is driven by a cam drive sprocket gear 24 of a rear crankshaft 15b and a cylinder head 12 to drive a valve operating cam shaft. A cam chain 26 is suspended between 25 and 25.

Next, as shown in FIG. 1, the crankcase 10
A plane that passes through the axes of both crankshafts 15a and 15b is divided into upper and lower split surfaces 27
As upper crankcase 28 and lower crankcase 29
The lower crankcase 29 is further divided into left and right divided lower crankcases 31 and 32 with a plane orthogonal to the axis of the crankshafts 15a and 15b as a left and right divided surface 30, and these are combined together.

The crankshafts 15a, 15b are rotatably supported across the upper and lower split surfaces 27, and both ends of the counter shaft 17 and the drive shaft 21 are spanned over the side walls 31a, 32a of the split lower crankcases 31, 32. . The counter shaft 17 projects from the side wall 32a, the primer driven gear 18 and the friction clutch 19 are axially mounted on the projecting end 17a, and the clutch cover 33 is attached.

Since the divided lower crankcases 31, 32 are both bowl-shaped, the side walls 31a, 32a have high rigidity. Therefore, the shaft support of the counter shaft 17 and the drive shaft 21 is stable, the mechanical loss is small, and the gear trouble and gear noise of the transmission gear mechanism are small.

〔The invention's effect〕

As described above, in the motorcycle engine according to the present invention, the crankcase is divided into upper and lower parts on a plane passing through the axes of the two crankshafts, and the lower crankcase is a plane perpendicular to the crankshaft axes. Since it is further divided into right and left, the rigidity of the shaft support portion of the counter shaft and the drive shaft is increased, and the operation of the mission gear mechanism is stabilized.

[Brief description of drawings]

FIG. 1 is a rear view of a longitudinal section of a crankcase showing an embodiment of the present invention, FIG. 2 is a side view of an engine unit including the crankcase of FIG. 1, and FIG. It is a side view of a two-wheeled vehicle. 1 ... Engine unit, 10 ... Crankcase, 15 ...
… Front crankshaft, 15b …… Rear crankshaft, 17 …… Counter shaft, 21 …… Drive shaft, 27 …… Upper and lower split surface, 28 …… Upper crankcase, 29 …… Lower crankcase, 30
...... Left and right split surface, 31,32 ...... Split lower crankcase, 3
1a, 32a …… Sidewall.

Claims (1)

(57) [Claims] 1. A multi-cylinder engine composed of two crankshafts arranged in front and rear, wherein a crankcase is divided into a top and a bottom in a plane passing through the axes of the two crankshafts, and The lower crankcase is divided into left and right in a plane orthogonal to the crankshaft axis, and the counter shaft and drive shaft that make up the transmission gear mechanism are laid across both side walls of the upper and lower lower crankcases. Motorcycle engine.