JP2572502B2 - Balancer mechanism for two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balancer mechanism for a two-stroke engine, and more particularly to a lubrication structure for the balancer mechanism.

[0002]

2. Description of the Related Art In recent years, a two-stroke engine is also provided with a balancer mechanism to reduce vibration. This balancer mechanism is provided with a balancer integrally on the balancer shaft to cancel imbalance such as inertial force due to reciprocating motion of a piston or the like or rotation of a crank weight attached to the crankshaft. And the like, and is configured to rotate forward or reverse with respect to the crankshaft.

In a two-stroke engine of a crankcase preload type that requires a closed state of the crankcase, the balancer mechanism is provided in a balancer case provided separately from the crankcase. Become. As such prior art, there are JP-A-58-77950 and JP-A-63-170634.

In general, lubrication of a sliding portion such as a bearing portion of a balancer shaft constituting the balancer mechanism or a meshing portion of a driven gear meshing with a drive gear on the crankshaft side includes lubrication of an engine body. Separately, a lubrication device for the balancer mechanism is separately required.

[0005]

As a lubricating device for the balancer mechanism, for example, an oil bath type lubricating device can be considered. However, if such a lubricating device is provided, it is necessary to check the amount of oil in the lubricating device. In addition, it is necessary to consider oil cooling.
It takes time in maintenance and inspection.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a balancer mechanism provided with a lubricating device which is inexpensive and requires no maintenance.

[0007]

A balancer mechanism for a two-stroke engine according to the present invention is a balancer mechanism for a crankcase preload-type two-stroke engine in which a balance weight is attached to a balancer shaft, wherein the balancer shaft includes the balancer shaft. In addition to providing a case, the balancer case and the crank chamber are communicated with each other through a communication path, and valve means for allowing only the flow from the balancer case to the crank chamber is disposed in the communication path. A suction port communicating with a supply means for supplying the air-fuel mixture is provided, and the balancer mechanism is lubricated by the air-fuel mixture.

[0008]

According to the balancer mechanism of the two-stroke engine according to the present invention, when the pressure in the crank chamber becomes negative during the intake stroke of the engine, the balance chamber is disposed in the communication passage connecting the balancer case and the crank chamber. The valve means is opened, so that the balancer case also has a negative pressure, and the air-fuel mixture is supplied from the supply means to the suction port of the balancer case. Then, the sliding portion of the balancer mechanism in the balancer case is lubricated by the air-fuel mixture. In the scavenging stroke of the engine, when the pressure in the crank chamber becomes positive, the crank chamber is isolated from the balancer case by the valve means , and the air-fuel mixture in the crank chamber does not flow back into the balancer case. Driving can be performed.

In the scavenging process of the engine, when the pressure in the crank chamber becomes positive, the crank chamber is isolated from the balancer case by the check valve, and the air-fuel mixture in the crank chamber does not flow back into the balancer case. The smooth operation of the cycle engine can be performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the configuration of a crankcase and a balancer case of a crankcase preload type two-stroke engine according to an embodiment of the present invention. FIGS. 2 (a) and 2 (c) show the configuration of a balance weight. 1 and II-II in FIG.
It is arrow sectional drawing.

In FIG. 1, reference numeral 1 denotes a crankshaft;
Is a crank weight (also referred to as a web), 3 is a connecting rod, 4 is a balancer shaft, and 5 is a balance weight.

The two-stroke engine according to the present embodiment
The basic configuration of the engine is the same as that of a well-known two-stroke engine of a crankcase preload type. In a sealable crankcase C, a crank weight 2 fixed to the crankshaft 1 is rotatably disposed. 1
A large end of the connecting rod 3 is rotatably connected to the crankpin portion of the connecting rod. Then, the crank chamber C above the scavenging ports provided in the crankcase C _c (not shown), by the step-up in the crank chamber C due to the descent of the piston, the combustion chamber above the engine from the crank chamber C ( (Not shown).

In the balancer mechanism of the two-stroke engine according to the present invention, the side of the crank chamber C (FIG. 1)
In the left side) and the crankcase C and the balancer case B
Is formed, and a rotary valve 7 as valve means is integrally provided on the balancer shaft 4 at a suction port of the communication passage 6. That is, as shown in FIG. 2B, which is a cross-sectional view taken along the line III-III in FIG. 1, the rotary valve 7 is formed of a disk-shaped member having an opening 7a extending along the circumferential direction. The valve is "open" when the opening 7a coincides with the communication passage 6 of the crank chamber C, and the valve is "closed" at other positions. In this case, the valve is closed during the compression stroke of the engine. Is attached to be in the “open” state.

The balancer shaft 4 has a crank chamber C
, Both ends are rotatably supported by bearings 11 and are enclosed by a balancer case B as a closed space integrally extending from the crank chamber C. The balancer case B is partitioned so as to be able to communicate with the crank chamber C by the rotary valve 7, and the suction port 9 formed at the right end in FIG. 1 is connected to the air-fuel mixture supply means 10 composed of a vaporizer. Have been. In the balancer case B, a pair of gears 12 for transmitting rotation from the crankshaft 1 to the balancer shaft 4 are incorporated, and both ends of the balancer shaft 4 have reciprocating pistons or crank weights. The balance weight 5 shown in FIG. 1 or FIGS. 2 (a) and 2 (c) is provided in order to dynamically balance the inertial force due to the rotation of.

Thus, the balancer mechanism of the present two-stroke engine configured as described above operates as follows.

That is, when the engine is operating, the balancer mechanism operates, and the balancer shaft 4 rotates in synchronization with the crankshaft 1 to reduce engine vibration. During this operation, the rotary valve 7 is opened during the compression stroke of the engine in which the pressure in the crank chamber becomes negative, and the inside of the balancer case B is brought into a negative pressure state. Therefore, in the balancer case B, the supply means
An air-fuel mixture containing lubricating oil is supplied from 10, and both sides of the bearing 11, the gear 12, and the rotary valve 7 in the balancer case B are wetted (lubricated) by the air-fuel mixture.

As described above, according to the balancer mechanism of the present two-stroke engine, lubrication can be easily performed using the air-fuel mixture used as fuel. In addition, according to this lubrication mechanism (device), the amount of air-fuel mixture supplied to the balancer case can be increased or decreased in proportion to the engine speed, so that lubrication and cooling suitable for the operating conditions can be achieved. Becomes

Although not mentioned in the above embodiment, a normal carburetor for directly supplying the air-fuel mixture to the crank chamber C may be provided in addition to the above-mentioned supply means 10, or the above-mentioned supply means may be provided. 10 may be configured to supply all the mixture required for operation to the crankcase C via the balancer case B. Further, although the number of cylinders of the engine is not mentioned at all, it goes without saying that the invention can be applied to an engine having a plurality of cylinders even if it is a single cylinder.

Further, in the above embodiment, a rotary valve is used as the valve means , but another type of valve (valve) such as a reed valve may be used instead.

[0021]

According to the balancer mechanism of the two-stroke engine according to the present invention, since the negative pressure in the crankcase of the engine is used for supplying the air-fuel mixture, a power source for separately supplying the air-fuel mixture is provided. Since it is not necessary to provide the device, it can be implemented at low cost. Further, according to this balancer mechanism, since the air-fuel mixture used as fuel is used,
Since a fresh air-fuel mixture is always supplied, regular troublesome maintenance such as another lubrication mechanism such as an oil bath type is not required.

Further, most of all, since the optimum lubrication state and cooling in proportion to the engine speed can be easily obtained, the reliability of the important balancer mechanism for reducing engine vibration is improved.

In addition, it is only necessary to provide a communication passage provided with a valve means and a suction port communicating with the supply means in the balancer case enclosing the balancer shaft portion, so that the outer shape can be made very compact. .

[Brief description of the drawings]

FIG. 1 is a crankcase preload type 2 according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing a configuration of a crank chamber and a balancer case of the cycle engine.

FIG. 2 (a) is a view taken on line II of FIG. 1 showing a configuration of a balance weight, and FIG. 1 (b) is a view showing a configuration of a rotary valve.
FIG. 2 is a sectional view taken along line III-III of FIG. 1, and FIG. 2C is a sectional view taken along line II-II of FIG.

[Explanation of symbols]

 4 ... Balancer shaft 5 ... Balance weight 6 ... Communication path 7 ... Rotary valve 9 ... Inlet 10 ... Supply means B ... Balancer case C ... Crank chamber

Claims (1)

(57) [Claims] 1. A balancer mechanism for a crankcase preload-type two-stroke engine, wherein a balancer shaft provided with a balance weight is rotatably disposed in a balancer case formed separately from a crankcase. The chambers are communicated by a communication passage,
By providing a valve means for allowing only the flow from the balancer case to the crank chamber in this communication path, and providing the balancer case with an intake port communicating with a supply means for supplying a mixture containing lubricating oil, A balancer mechanism for a two-cycle engine, wherein the balancer mechanism is lubricated by an air-fuel mixture passing through a balancer case.