JPH027326Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a 180° crank 4-stroke 2-cylinder engine with a balancer mechanism, specifically a 4-cycle 2-cylinder engine that reduces impact noise generated in the gear transmission device that drives the balancer shaft. Regarding cylinder engines.

Conventionally, various types of engines with balancer mechanisms have been proposed that cancel engine vibrations (particularly vibrations caused by a crank weight formed on the crankshaft).

Among these, in the gear-driven single-shaft balancer mechanism, as shown in the conceptual diagram of FIG.
and a driven gear 5 disposed on the balancer shaft 4 so as to mesh with the drive gear 3, the drive gear is transmitted to the balancer shaft 4 to drive the balancer shaft 4. .

In FIG. 1, numerals 6 and 7 are a piston and a connecting rod, respectively, and numerals 8 and 9 are a crank weight and a balancer weight, respectively.

On the other hand, the inventor of the balancer mechanism in this 180° crank 4-cycle 2-cylinder engine,
The measurement results shown in Figure 2 were obtained.

That is, the rotational force of the crankshaft fluctuates with a unique periodicity, as shown in the graph of FIG. 2a, due to factors such as engine explosion and direction change of the crank weight couple.

Furthermore, the distance L between the crankshaft 2 and balancer shaft 4 shown in FIG. Then, it fluctuates as shown in the graph shown in FIG. 2b.

By the way, Fig. 2c is a graph showing the noise level when the drive gear 3 and the driven gear 5 mesh.
In a two-cylinder cycle engine, the crank rotation angle
137° ~ 167° (This crank rotation angle is 137° ~
167° is an angle of 137° to 167° from the top dead center of one cylinder in a 4-cycle two-cylinder engine with a 180° crank, where the explosion stroke is 180° before the explosion stroke of one cylinder at the crank angle. It was found that the noise level was high in the vicinity of

This is because the meshing state between the drive gear 3 disposed on the crankshaft 2 and the driven gear 5 disposed on the balancer shaft 4 shown in FIG. 4 and the rotational force fluctuation of the crankshaft 2, especially when the rotational fluctuation of the crankshaft 2 is large and the distance between the crankshaft 2 and the balancer shaft 4. If L is large, then the drive gear 3 and the driven gear 5 will mesh with each other in an impactful manner, thereby generating a large amount of noise.

This idea is based on a 180° crank 4-stroke 2-cylinder engine in which the crankshaft has a crank rotation angle of 137° to 167° (i.e., in a 180° crank 4-stroke 2-cylinder engine, the crank angle is greater than the explosion stroke of one cylinder). This crank rotation suppresses the increase in bumps that occur at the meshing part between the drive gear and the driven gear when the cylinder rotates 137° to 167° from the top dead center of the other cylinder that undergoes the explosion stroke 180° before the other cylinder. The purpose of this engine is to provide a four-stroke, two-cylinder engine that prevents noise between the gears that occurs at the corners. One of the gears and the driven gear is installed eccentrically by a predetermined amount in the meshing direction when the crankshaft is rotated by a crank rotation angle of 137° to 167°, and depending on this eccentricity, the crankshaft This is to absorb the increase in the distance between the crankshaft and balancer shaft when the balancer shaft is rotated by a crank rotation angle of 137° to 167°.

Hereinafter, one embodiment of a four-stroke two-cylinder engine according to this invention will be described in detail.

FIG. 3 is a conceptual diagram of a four-stroke two-cylinder engine 10 according to this invention. In particular, in a four-stroke two-cylinder engine with a crankshaft having a crank rotation angle (θ) of 137° to 167° (i.e., 180°), one The explosion stroke of the cylinder is 180 degrees before the explosion stroke of the other cylinder (at an angle of 137 degrees to 167 degrees from the top dead center of the other cylinder). It is shown in

In Fig. 3, the drive gear 3 disposed on the crankshaft 2 is arranged so that the crankshaft 2 has a crank rotation angle of 137° to 167° (i.e., 180° in a 4-cycle two-cylinder engine with a crankshaft), and the explosion stroke of one cylinder. The position in the meshing direction of the driven gear 5 with which the drive gear 3 meshes when the cylinder rotates at an angle of 137° to 167° from the top dead center of the other cylinder that undergoes the explosion stroke 180° before the crank angle. It is attached and fixed to the crankshaft 2 eccentrically by a certain amount t (usually t=0.1 mm).

Note that point α indicates the center of the crankshaft 2, and point β indicates the center of the drive gear 3.

Therefore, when the crankshaft 2 reaches the crank rotation angle (θ=137° to 167°), the crank weight 8 formed on the crankshaft 2 and the balancer shaft disposed parallel to the crankshaft 2 The increase in the distance L between the crankshaft 2 and the balancer shaft 4 caused by the couple (arrows A and B) acting on each of the balancer weights 9 formed in the drive gear 3 is caused by the eccentricity of the drive gear 3. Therefore, the drive gear 3 at the crank rotation angle (θ=137° to 167°)
An increase in bumpiness occurring at the meshing portion between the driven gear 5 and the driven gear 5 is suppressed.

In the above embodiment, one of the drive gears 3 and 5 constituting the balancer mechanism is mounted and fixed eccentrically by a predetermined amount, but this invention is of course limited to the above embodiments. Alternatively, the other driven gear 5 may be eccentrically mounted to the balancer shaft 4 by a predetermined amount.

As explained above, in this invention, the crankshaft of a 180° crank 4-stroke 2-cylinder engine is at a crank rotation angle of 137° to 167°, that is, in a 180° crank 4-cycle 2-cylinder engine, one cylinder will explode. The bump crash that occurs at the meshing part between the drive gear and the driven gear when the other cylinder is rotated at an angle of 137° to 167° from the top dead center of the other cylinder, which undergoes the explosion stroke 180° in terms of crank angle before the cylinder stroke, is calculated as follows: Since the noise is absorbed by the eccentricity of the driven gear, it is possible to prevent the noise between the gears that occurs at this crank rotation angle, making it quiet and reducing wear on the tips of each tooth of the drive and driven gear. It is possible to provide a highly durable four-stroke two-cylinder engine.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the main parts of a conventional 4-cycle two-cylinder engine, and Figures 2 a, b, and c show variations in the rotational force of the crankshaft, and variations in the distance between the shafts of the drive and driven gears that make up the balancer mechanism, respectively. and a graph showing fluctuations in the noise level generated by the balancer mechanism, and FIG. 3 is a conceptual diagram of main parts showing a four-cycle two-cylinder engine according to this invention. 10... 4-stroke 2-cylinder engine, 2... crankshaft, 3... drive gear, 4... balancer shaft, 5... driven gear, 8... crank weight, 9... balancer weight.

Claims (1)

[Scope of Claim for Utility Model Registration] A gear transmission device consisting of a drive gear fixed to a crankshaft and a driven gear fixed to a balancer shaft arranged parallel to the crankshaft are meshed with each other. In the 180° crank four-cycle two-cylinder engine that drives the balancer shaft, the crankshaft drives either one of the drive gear and the driven gear at a crank rotation angle.
It is installed eccentrically by a predetermined amount in the direction of engagement when rotated by 137° to 167°, and the crankshaft is rotated at the crank rotation angle.
A four-stroke, two-cylinder engine characterized in that a variation in the distance between the crankshaft and the balancer shaft when rotated by 137° to 167° is absorbed by the eccentricity of the one gear.