JPH0828629A - Crankshaft device for two-cylinder four-cycle engine - Google Patents

Abstract

PURPOSE:To reduce energy loss even in the case that massive error occurs at balance weights when a crankshaft alone is balanced, by easily adjusting the massive error afterward, and reducing the mass of a second balance weight. CONSTITUTION:A fan driving pulley 20 and a flywheel 25 are fixed to a crankshaft 10 in which a crank angle of 180 degrees are shown between a first crank pin 11a and a second crank pin 11b. A first balance weight W1 which suppresses a vibration moment M of the crank shaft 10 is arranged on a crank arm 12a on one end side of the crankshaft 10. A second balance weight W2 is arranged on a flywheel 2 fixed to the other end side of the crankshaft 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft device for a two-cylinder, four-cycle engine, and more particularly to a technique for suppressing a swinging moment of the crankshaft.

[0002]

2. Description of the Related Art As a crankshaft of a two-cylinder four-cycle engine, for example, as shown in FIGS.
There is one in which the crank angle of the crank pin 11a and the second crank pin 11b is set to 180 °. In this case,
The primary inertial forces cancel each other out by the first piston 1 and the second piston 2, but a deflection moment M as shown in FIG. 3 (B) acts on the crankshaft 10. In order to suppress this deflection moment M, a first
The counterweight W1 may be provided, and the second counterweight W2 may be provided near the other end.

As a technique for suppressing the deflection moment M, a technique shown in, for example, FIG.
4) (hereinafter, referred to as Conventional Example 2) is known. Here, FIG. 3A shows a conventional example 1
FIG. 4B is a schematic diagram of the crankshaft device according to Conventional Example 2, FIG. 4B is a schematic diagram of the crankshaft device according to Conventional Example 2, and FIG. It is a schematic diagram of an apparatus.

In the conventional example 1, as shown in FIGS. 3A and 3B, a fan drive pulley 20 is fixed to one end shaft portion 14 of the crankshaft 10 and a flywheel 25 is fixed to the other end shaft portion 15. The first balance weight W1 on the fan drive pulley 20.
The flywheel 25 is provided with a second counterweight W2. The first counterweight W1 and the second counterweight W2 are the fan drive pulley 20 and the flywheel 2 respectively.
5 is provided integrally with a required thick wall portion, and the amount of adjustment for suppressing the swinging moment M is appropriately determined by drilling holes (27a / 27b) (28a / 28) in the thick wall portion.
Apply b) and adjust.

Each crank arm 1 of the crankshaft 10
2a to 12d are provided with counterweights W3 and W4 by integrally forming required thick portions, respectively. By providing these counterweights W3 and W4, the crankshaft alone (a state in which a piston is not mounted, The same applies hereinafter) is configured to be balanced. In addition,
Reference numeral 16 is a power take-out shaft portion fixed to the flywheel 25.

In the conventional example 2, as shown in FIGS. 4A and 4B, a fan drive pulley 20 is fixed to one end shaft portion 14 of the crankshaft 10 and a flywheel 25 is fixed to the other end shaft portion 15, respectively. A first counterweight W1 is provided on the crank arm 12a near the one end of the crankshaft 10, and a second counterweight W2 is provided on the crank arm 12d near the other end. The first counterweight W1 and the second counterweight W2 are provided in equal amounts on the opposite sides of the crank pins 11a and 11b of the respective crank arms 12a and 12d by integrally forming required thick portions. .

[0007]

In each of the above-mentioned conventional examples, the fan drive pulley 20 is fixed to the one end shaft portion 14 of the crankshaft 10 and the flywheel 25 is fixed to the other end shaft portion 15. However, depending on the engine, as shown in FIG. 1, for example, a flywheel 25 and a fan drive pulley 20 are fixedly mounted on the other end shaft portion 15 of the crankshaft 10. In such a case, the counterweight W1
Even if W2 is provided, the deflection moment M of the crankshaft 10 cannot be suppressed. Therefore, Conventional Example 1 cannot be applied as it is, and Conventional Example 2 is applied. In other words, it is necessary to prepare two types of crankshafts and use them properly.

Further, when the conventional example 2 is applied, there are the following inconveniences. Normally, when manufacturing the crankshaft 10, it is necessary to balance the crankshaft alone as described above. That is, each crank arm 12a-1
1d of equal amount by integrally forming required thick portions on 2d
Since the counterweight W1 and the second counterweight W2 are provided, in order to balance the crankshaft by itself, as shown by the broken line in FIG. 3 (B), dummy weights V1. V2 is the first counterweight W1 and the second
Since it is necessary to mount the counterweight W2 so as to face it, it is troublesome. Moreover, in the case of the conventional example 2, since the dimension D up to the crank arms 12a and 12d provided with the central crank journal 13b and the counterweights W1 and W2 is relatively small, the fishing line for suppressing the swinging moment M is suppressed. Weight W1
-Since it is necessary to increase the mass of W2, energy loss increases.

The present invention has been made in consideration of such circumstances, and a case where a fan drive pulley 20 is provided on one end side of the crankshaft 10 and a flywheel 25 is provided on the other end side, and other cases of the crankshaft 10 In the case where the flywheel 25 and the fan drive pulley 20 are provided on the end side, it is not necessary to prepare two types of crankshafts so that they can be shared by a single crankshaft. The technical problem is to reduce the number of dummy weights attached to the crank arm to reduce the inconvenience thereof and to reduce the energy loss by reducing the mass of the second counterweight W2.

[0010]

In order to solve the above problems, the present invention provides a fan drive pulley 20 on a crankshaft 10 in which a first crank pin 11a and a second crank pin 11b are set at a crank angle of 180 °. In a crankshaft device for a two-cylinder four-cycle engine, in which a flywheel 25 is fixedly provided, a first counterweight W1 is provided near one end of the crankshaft 10, and a second counterweight W2 is provided near the other end thereof.
The first counterweight W1 is provided on the crank arm 12a near one end of the crankshaft 10, and the second counterweight W2 is provided on a flywheel 25 fixed near the other end of the crankshaft 10. It is a thing.

[0011]

[Operation / Effect] The present invention has the following operation / effect. The first counterweight W1 is provided on the crank arm 12a near one end of the crankshaft 10, and the second counterweight W2 is provided on the flywheel 25 fixed near the other end of the crankshaft 10. Of the fan drive pulley 20 on one end side of the crankshaft 10 and the flywheel 25 on the other end side of the crankshaft 10, and the flywheel 25 on the other end side of the crankshaft 10.
It is not necessary to prepare and use two kinds of crankshafts differently depending on whether the fan drive pulley 20 is provided, and a single crankshaft can be used in common.

Since the first counterweight W1 is provided on the first crank arm 13a near the one end, in order to balance the crankshaft alone, as shown by the broken line in FIG. 1B, the dummy weight V1 is used. Is attached so as to face the first counterweight W1, but since the number of dummy weights to be attached is only one, the troublesomeness of attaching the dummy weights can be reduced to half.

The second counterweight W2 is used for the crankshaft 10
Since it is provided on the flywheel 25 fixed near the other end, the dimension L up to the flywheel 25 provided with the central crank journal 13b and the second counterweight W2 as shown in FIG. , Central crank journal 13b
And the second counterweight W for suppressing the deflection moment M because it is larger than the dimension D up to the first counterweight W1.
The mass of 2 can be made smaller than the mass of the first counterweight W1. The energy loss can be reduced as much as the mass of the second counterweight W2 is reduced.

[0014]

Embodiments of the present invention will now be described in more detail with reference to the drawings. 1A is a schematic diagram of a crankshaft device according to a first embodiment of the present invention, and FIG. 1B is a schematic diagram of the crankshaft device. The crankshaft device according to this embodiment, as shown in FIGS. 1A and 1B, has the following configuration. In FIG. 1A, reference numeral 3 is a first cylinder of the engine body, 4 is a second cylinder, 5 is a fan pulley, 6 is a cooling fan, 7 is a fan belt, and 26 is an outer periphery of the flywheel 25. It is a fixed ring gear.

The crankshaft 10 includes a first crankpin 11a, a second crankpin 11b, and a crank arm 12.
a / 12b / 12c / 12d, crank journal 13
a, 13b, 13c, one end shaft portion 14, and the other end shaft portion 15
And the first crank pin 11a and the second crank pin 11b are set at a crank angle of 180 °. A first piston 1 is connected to the first crank pin 11a and a second piston 2 is connected to the second crank pin 11b through a connecting rod. The primary inertia force is generated by the first piston 1 and the second piston 2. Cancel each other out.

A flywheel 25 is fixed to the other end shaft portion 15 of the crankshaft 10 by a fixing bolt 22, and a fan drive pulley 20 is fixedly mounted on the flywheel 25 by a fixing bolt 23. Further, as in the case of the conventional example 1, the crank arms 12a to 12d of the crankshaft 10 are provided with counterweights W3 and W4 by integrally forming required thick portions, and the crank arms 12a closer to one end. Is provided integrally with a first counterweight W1 and the flywheel 25 is integrally provided with a second counterweight W2. As a result, the deflection moment M acting on the crankshaft 10 is
It is suppressed by the counterweight W1 and the second counterweight W2.
The one end shaft portion 14 of the crankshaft 10 is configured as a power takeout portion.

The operation of the crankshaft device according to this embodiment will be described below. As described above, the first counterweight W1 is provided on the crank arm 12a near one end of the crankshaft 10, and the second counterweight W2 is provided on the flywheel 25 fixed near the other end of the crankshaft 10. From the case where the fan drive pulley 20 is provided on one end side of the crankshaft 10 and the flywheel 25 is provided on the other end side.
To the other end of the flywheel 25 and the fan drive pulley 2
There is an advantage that it is not necessary to prepare and use two types of crankshafts differently when 0 is provided, and a single crankshaft can be used in common.

Since the first counterweight W1 is provided on the first crank arm 12a near the one end, in order to balance the crankshaft alone, as shown by the broken line in FIG. 1B,
The dummy weight V1 is attached so as to face the first counterweight W1, but the number of attachments is only one, and therefore the burden of attaching the dummy weight can be reduced to half. Further, as shown in FIG. 1 (A), by machining the drill holes 28a and 28b in the thick portion of the flywheel 25, the second counterweight W2 is substantially provided with respect to the first counterweight W1. Can be balanced.

Since the second counterweight W2 is provided on the flywheel 25 fixed near the other end of the crankshaft 10, as shown in FIG. 1B, the central crank journal 13b and the second balance weight W2 are provided. Flywheel 2 with a weight W2
Since the dimension L up to 5 is larger than the dimension D up to the central crank journal 13b and the first counterweight W1,
The mass of the second counterweight W2 for suppressing the deflection moment M can be made smaller than the mass of the first counterweight W1. The energy loss can be reduced as much as the mass of the second counterweight W2 is reduced.

FIG. 2 is a view corresponding to FIG. 1 showing a crankshaft device according to a second embodiment of the present invention. In this crankshaft device, as shown in FIGS. 2A and 2B, a fan drive pulley 20 is fixed to one end shaft portion 14 of a crankshaft 10, and a flywheel 25 is fixed to the other end shaft portion 15. , 1st counterweight W
1 is a first crank arm 1 near one end of the crankshaft 10.
2a, the second counterweight W2 is provided on the flywheel 25 fixed near the other end, and the crank arms 12a to 12a.
Counter weights W3 and W4 are not provided in d.
Also in the second embodiment, the same operation and effect as those of the first embodiment (FIG. 1) are obtained.

[Brief description of drawings]

FIG. 1 shows a crankshaft device according to a first embodiment of the present invention, FIG. 1A is a schematic diagram of the crankshaft device, and FIG. 1B is a schematic view of the crankshaft device.

FIG. 2 is a view corresponding to FIG. 1 showing a crankshaft device according to a second embodiment of the present invention.

FIG. 3 is a view corresponding to FIG. 1 showing a crankshaft device according to Conventional Example 1.

FIG. 4 is a view corresponding to FIG. 1 showing a crankshaft device according to Conventional Example 2.

[Explanation of symbols]

10 ... Crankshaft, 11a ... 1st crankpin, 11b
... second crankpin, 12a ... crank arm near one end, 20 ... fan drive pulley, 25 ... flywheel,
W1 ... 1st counterweight, W2 ... 2nd counterweight.

 ─────────────────────────────────────────────────── (72) Inventor Nobuhiro Yamamoto 64 Ishizukitamachi, Sakai City, Osaka Prefecture, Kubota Sakai Co., Ltd.

Claims (1)

[Claims] 1. A fan drive pulley (20) and a flywheel (25) are fixed to a crankshaft (10) having a crank angle of 180 ° between the first crankpin (11a) and the second crankpin (11b). This crankshaft (10)
The first counterweight (W1) near one end and the second counterweight near the other end.
In a crankshaft device for a two-cylinder, four-cycle engine configured by providing a counterweight (W2), the first counterweight (W1) is provided on a crank arm (12a) near one end of the crankshaft (10). The crankshaft device for a two-cylinder four-cycle engine, wherein the two counterweights (W2) are provided on a flywheel (25) fixed near the other end of the crankshaft (10).