JPH0568398B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine having a balancer shaft and a starter motor used in a unit swing type vehicle.

(Prior art) In vehicles such as scooters, the engine, transmission, and rear wheels are integrated to form a power unit, and this power unit is connected to the vehicle body frame directly or indirectly via a pivot shaft so that it can swing vertically. There is a unit swing type. In this type of vehicle, it is desirable to reduce the moment of inertia about the pivot axis of the power unit in order to improve the road following ability of the rear wheels and increase running stability. However, when a balancer shaft for vibration absorption or a starter motor is attached to an engine, the engine part generally becomes larger and the crankshaft tends to be farther away from the pivot shaft, resulting in a problem that the moment of inertia around the pivot shaft increases. If the engine is a four-stroke engine, the weight of the engine increases, so this moment of inertia tends to become even larger. Further, in a small four-stroke engine used in a scooter or the like, it is desirable to increase the volume of the lower part of the crank chamber for reasons of lubrication.

(Object of the Invention) The present invention was made in view of the above circumstances, and even though the engine is provided with a balancer shaft and a starter motor, the moment of inertia around the pivot axis of the power unit can be reduced, and the rear wheel An object of the present invention is to provide an engine for a unit swing type vehicle, which can improve the road surface followability of the vehicle, thereby increasing running stability, and which can also be arranged in an engine suitable for lubrication.

(Structure of the Invention) The present invention achieves the above object by arranging the starter motor, crankshaft, and balancer shaft so that they surround the pivot shaft. That is, according to the present invention, this purpose is 4.
In a unit swing type vehicle in which a cycle engine, a transmission device, and a rear wheel are integrated to form a power unit, and this power unit is connected to the vehicle body frame by a pivot shaft so as to be able to swing vertically, the cylinder of the engine is placed vertically and the front end of the crankcase is connected. the pivot shaft is disposed in the pivot shaft, and the center axes of the starter motor and the balancer shaft are disposed between the pivot shaft and a crankshaft parallel thereto on the upper side and the lower side of a plane including both these axes, respectively;
This is achieved by a unit swing type vehicle engine characterized in that the balance weight of the balancer shaft is intermittently inserted between the crank webs of the crankshaft.

(Example) The present invention will be explained in detail below based on the drawings.

FIG. 1 is a side view of a two-wheeled scooter which is an embodiment of the present invention, and FIG. 2 is a side sectional view of its engine.
Figures 3 and 4 are the - line and - line in Figure 2.
FIG. In FIG. 1, reference numeral 10 denotes a vehicle body frame, which includes a steering head tube 12, a down tube 14, a pair of left and right back tubes 16 (only one of which is shown), and the like. A front wheel 20 is attached to the lower part of the steering shaft 18 held by the head tube 12 via a front fork 20. 24 is a steering wheel, and 26 is a driver's seat.

30 is a power unit in which a forced air-cooled four-stroke engine 32, a V-belt type transmission 34, and a rear wheel 36 are integrated. The front end of the power unit 30 is connected by a pivot shaft 40 to a pair of left and right brackets 38 (only one of which is shown) fixed to a pair of right and left bag tubes 16 of the vehicle body frame 10, respectively. As a result, the power unit 30 can swing up and down about the pivot shaft 40. Power unit 30
The rear part of the bag 16 is resiliently supported by a damping unit 42 on the bag tube 16. In FIG. 1, 44 is an intake air purifier, 46 is a carburetor, 48 is an exhaust pipe, 50 is an exhaust muffler, and 52 is an exhaust duct for engine cooling air.

The engine 32 is constructed as shown in FIGS. 2-4. In these figures, reference numeral 54 denotes a crankshaft, which is disposed behind the pivot shaft 40 and parallel to the pivot shaft 40, and is held in left-right split crankcases 60, 60a, 60b via bearings 56, 58. 62 is a cylinder, 64 is a cylinder head, 6
6 is a piston, 68 is a connecting rod, and 70 is an overhead camshaft. This camshaft 70 is rotated at half the speed of the crankshaft 54 by a timing chain 72 that is wound between the camshaft 70 and the crankshaft 54, and opens and closes an intake valve 78 and an exhaust valve 80 via rocker arms 74 and 76. Although not shown in FIG. 2, the cylinder head 64 is of course provided with an ignition plug. A magneto generator 84 is attached to the right end of the crankshaft 54, and a starting one-way clutch 86 and a drive pulley 88 of the V-belt transmission 34 are attached to the left end of the crankshaft 54. Note that 90 is a cover that covers the cylinder 62 and cylinder head 64 from the side of the generator 84. A fan 92 fixed to the generator 86 sucks outside air into the cover 90 through an air intake port 94 provided in the cover 90 and sends cooling air to the cylinder 62 and cylinder head 64.
This cooling air is discharged below the engine 32 from the exhaust duct 52 (FIG. 1).

96 is a balancer shaft parallel to the pivot shaft 40, and its central axis is below the plane connecting the central axes of the pivot shaft 40 and the crankshaft 54, as shown in FIG. located between. This balancer shaft 96 includes crank webs 54a and 5 of the crankshaft 54.
A balance weight 98 that is inserted intermittently between 4b is integrally formed. The balancer shaft 96 is connected to the gear 1
00 and 102, the crankshaft 54 is driven in the reverse direction at a constant speed with respect to the crankshaft 54.
The primary vibration caused by the rotation of the piston 66 and the vertical movement of the piston 66 is absorbed. This balancer shaft 96 has an oil passage 1.
04,106, a centrifugal filter 108 is provided,
Lubricating oil pumped from a lubricating oil pump (not shown) is led to an oil path 104 through a pipe 110, and after metal powder and the like are separated by a centrifugal filter 108, it flows into an oil path 106. A portion of the lubricating oil in this oil passage 106 is supplied from a nozzle 112 provided on the balancer shaft 96.
It is ejected toward the large end of the stove rod 68.

114 is a starter motor, and its rotating shaft 1
16 (FIG. 4) is parallel to the pivot shaft 40, is above the plane connecting the central axes of the pivot shaft 40 and the crankshaft 54, and is parallel to the pivot shaft 40.
0 and the crankshaft 54. The rotation of the rotating shaft 116 of the starter motor 114 is transmitted to the gear 86a of the starting one-way clutch 86 via the deceleration idle gear 118.

In this embodiment, the rotation of the crankshaft 54 is transmitted to the rear wheel 36 via the V-belt transmission 34, and vibrations accompanying the rotation of the crankshaft 54 are well absorbed by the balancer shaft 96. At the time of starting, the starter motor 114 rotates, and the crankshaft 54 is rotationally driven via the one-way clutch 86.

Since the pivot shaft 40, the crankshaft 54, the balancer shaft 96, and the starter motor 114 form a diamond shape when viewed from the side as shown in FIG.
The pivot shaft 4 of the power unit 30 can be placed close to the pivot shaft 40.
The moment of inertia around zero can be reduced.

In this embodiment, the pivot shaft 40 and the crankshaft 5
4. Balancer shaft 96 and starter motor 114
The diamond shape formed by is horizontally elongated, but if the crankshaft 54 is brought closer to the pivot shaft 40 and the starter motor 114 and balancer shaft 96 are further separated vertically to form a vertically elongated diamond shape,
The crankshaft 54, balancer shaft 96, and starter motor 114 are closer to the pivot shaft 40 surrounding the pivot shaft 40, and the moment of inertia is further reduced.

Further, in the present invention, since the balancer shaft 96 is placed at the bottom and the motor 114 is placed at the top, it is convenient for lubrication of the balancer shaft 96, and the motor 114 is less likely to be exposed to muddy water. Furthermore, since the starter motor 114 is located above the plane that includes the pivot shaft 40 and the crankshaft 54, if it is installed below this plane, the lower part of the crankcase should be made to fit in the outer shape of the starter motor and make a large recess. There is no need to let it happen. Therefore, the volume of the lower part of the crankcase does not become smaller. On the other hand, since the balancer shaft disposed in the lower part of the crankcase is housed within the crankcase, the lower part of the crankcase has a large volume, which is convenient for lubrication.

(Effects of the Invention) As described above, the present invention is configured such that the center axes of the balancer shaft and the starter motor are located on both sides of the plane connecting the pivot shaft and the crankshaft. A heavy object such as a starter motor can be placed close to the pivot axis, and the moment of inertia of the power unit about the pivot axis can be reduced. As a result, the rear wheels' ability to follow the road surface improves, making it possible to enhance driving stability. Also, since the engine is closer to the pivot axis, it is possible to shorten the distance between the pivot axis and the rear wheels, and in this case, the moment of inertia around the pivot axis becomes even smaller, further improving driving performance. .

Furthermore, since the starter motor is located between the pivot shaft and the crankshaft and above the plane that includes both shafts, there is no need to make a large recess in the lower part of the crankcase along the outer shape of the starter motor, and the crank chamber There is no need to reduce the capacity at the bottom. Further, since the balancer shaft located below this plane is accommodated within the crankcase, the volume of the lower portion within the crankcase increases, which is convenient for lubrication. In particular, since the cylinder is placed vertically, the balance weight of the balancer shaft at the bottom of the crankcase is convenient for scattering lubricating oil from between the crank webs to the inside of the cylinder or the bottom surface of the piston, making it suitable for lubrication.

[Brief explanation of the drawing]

FIG. 1 is a side view of an embodiment of the present invention, FIG. 2 is a side sectional view of the engine, and FIGS. 3 and 4 are sectional views taken along lines - and - in FIG. 10...Vehicle frame, 30...Power unit, 32...Engine, 34...Transmission device, 36
... Rear wheel, 40 ... Pivot shaft, 54 ... Crankshaft, 96 ... Balancer shaft, 114 ... Starter motor.

Claims (1)

[Scope of Claims] 1. A unit swing type vehicle in which a four-stroke engine, a transmission, and a rear wheel are integrated to form a power unit, and this power unit is connected to a vehicle body frame by a pivot shaft so as to be able to swing vertically, comprising: While the cylinder is placed vertically and the pivot shaft is disposed at the front end of the crankcase,
The center axes of the starter motor and balancer shaft are arranged above and below a plane containing both axes between the pivot shaft and a crankshaft parallel to the pivot shaft, respectively, and the balance weight of the balancer shaft is aligned with the crankshaft. A unit swing type vehicle engine characterized by being intermittently inserted between the crank webs.