JP2001050348A - Crankshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the occurrence of whole bending of the crankshaft of a four-cylinder engine and mount a torsional damper to the front part in an axial direction of the crankshaft without especially varying the peripheral condition of the crankshaft. SOLUTION: In the crankshaft 10 of a four-cylinder engine, first-eighth balance weights 11-18 are disposed in positions situated opposite to respective crank arms 3, in the order, from the front side in an axial direction of the crank-shaft. The central loads of the first balance weight 11, the third balance weight 13, the sixth balance weight 16, and the eighth balance weight 18 are approximately equals to each other and lower than the centrifugal loads of other balance weights 12, 14, 15, and 17 approximately equal to each other. A torsional damper 19 is mounted on the front side in the axial direction of the crankshaft of the first balance weight 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft in which a torsion damper is mounted at a front portion in an axial direction in a four-cylinder engine, and more particularly to a structure of a balance weight provided on the crankshaft.

[0002]

2. Description of the Related Art As shown in FIG. 2A, a crankshaft 1 in a conventional in-line four-cylinder engine has:
While having the crank pin 2, the crank arm 3, and the journal 4, a relatively large unbalance force acts on the central portion in the axial direction due to the rotational motion, and the entire portion is easily bent largely. It is necessary to dispose a balance weight 5 having a relatively large centrifugal load at a position opposed to the crank arm 3 with the axis interposed therebetween. Also, in order to balance the entire crankshaft 1, the centrifugal load is substantially equal to the balance weight 5. The balance weight 6 must be disposed at positions opposite to the crank arms 3 at both ends of the crankshaft 1 with respect to the axis.

On the other hand, if the combustion pressure in each cylinder is increased in order to increase the engine output, a large unbalance force applied to the crankshaft 1 is balanced, as shown in FIG. 2 (B). As described above, the balance weights 7 having centrifugal loads substantially equal to the balance weights 5 and 6 are disposed at positions opposed to the remaining crank arms 3 with the axis of the crankshaft 1 interposed therebetween, and the balance weights 5, 6, 7 It is necessary to increase the total centrifugal load of the crankshaft 1. However, if an attempt is made to mount a torsional damper on the front portion in the axial direction of the crankshaft 1 without changing the surrounding conditions of the crankshaft 1, the situation shown in FIG. As shown, the front end of the crank arm 3 of the crankshaft 1 and the first balance weight 6 counted from the front side in the axial direction. Must be formed to form a mounting space for the torsional damper 8, so that the first balance weight 9 must reduce the centrifugal load, and therefore, it is possible to improve the rotational balance of the crankshaft 1. There is a problem that the lubrication of each journal 4 is likely to be inferior, and the centrifugal load on the balance weights 5, 6, and 7 other than the balance weight 9 is balanced to improve the rotational balance of the crankshaft 1. 9, the centrifugal load of the balance weight 5 becomes relatively small.
A problem arises in that it is difficult to effectively reduce the overall deflection of the.

[0004]

SUMMARY OF THE INVENTION The present invention effectively reduces the overall deflection of a crankshaft in a four-cylinder engine, and provides a crankshaft axial front without significantly altering the crankshaft ambient conditions. It is intended to make it possible to mount a torsional damper.

[0005]

For this reason, in a four-cylinder engine, a crankshaft according to the present invention is provided with a first balance weight at a position facing each crank arm across a crankshaft axis from the front side in the axial direction. To the eighth balance weight, and the first
The balance weight, the third balance weight, the sixth balance weight, and the eighth balance weight each have substantially the same centrifugal load, and the second balance weight, the fourth balance weight, the fifth balance weight, and the fifth balance weight have substantially the same centrifugal load. Each of the seven balance weights has a centrifugal load greater than the centrifugal load, and a torsional damper is mounted on the axially forward side of the first balance weight.

That is, the centrifugal load of the fourth balance weight and the fifth balance weight near the center in the axial direction of the crankshaft is relatively large, so that the overall deflection of the crankshaft can be effectively suppressed and the crankshaft can be effectively prevented. The first balance weight on the shaft ~
Since the eighth balance weight is provided and the total centrifugal load of each balance weight can be increased, even if the engine output is increased, the rotation balance of the crankshaft can be favorably maintained, and Since the centrifugal load of the 1 balance weight is relatively small, the first balance weight can be used without changing the surrounding conditions of the crankshaft.
A torsional damper can be easily mounted on the front side of the balance weight in the axial direction.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described by assigning the same reference numerals to the same parts as those of the conventional device. In FIG. 1, a crankshaft 10 of an in-line four-cylinder engine includes a crankpin 2, a crank arm 3, and a journal 4, and is located at a position facing the respective crank arms 3 with respect to the crank shaft axis. From the first balance weight 11, the second balance weight 12, the third balance weight 13, the fourth balance weight 14, the fifth balance weight 15, the sixth balance weight 16, the seventh balance weight 17, and the eighth balance weight 18. The first balance weight 11, the third balance weight 13, the sixth balance weight 16, and the eighth balance weight 18 are substantially the same and relatively small, respectively.
Although it has a centrifugal load, the second balance weight 1
The second, fourth, fifth and seventh balance weights 14, 15 and 17 each have substantially the same second centrifugal load that is greater than the first centrifugal load.

Each of the balance weights 11, 13, 16, and 18 having a relatively small centrifugal load is cut from the side surface of each of the balance weights 12, 14, 15, and 17 equivalent to each of the balance weights 12, 14, 15, and 17 having a relatively large centrifugal load. This can be easily formed by cutting each side surface and the side surfaces of the crank arm 3 facing the balance weights 11 and 18 across the crankshaft axis, respectively.

A torsional damper 19 is mounted on the first balance weight 11 on the front side in the axial direction of the crankshaft.

[0010] In this case, the fourth shaft arranged near the center of the crankshaft 10 in the axial direction of the crankshaft.
Since the balance weight 14 and the fifth balance weight 15 each have a relatively large centrifugal load, the overall deflection of the crankshaft 10 can be effectively suppressed, and at the same time, the balance weight 14 and the fifth balance weight 15 are connected to each of the crank arms 3 with the crankshaft axis interposed therebetween. Since the first to eighth balance weights 11 to 18 are provided at opposing positions, even if the unbalance force applied to the crankshaft 10 is increased due to an increase in engine output, the first balance weights are provided. The increase in the total centrifugal load by the 11th to the 8th balance weights 18 makes it possible to maintain the rotational balance of the crankshaft 10 in a favorable state, and thus ensures smooth rotation of the crankshaft 10 and
Lubrication can always be improved.

Since the first balance weight 11 disposed at the front end of the crankshaft 10 in the axial direction of the crankshaft has a relatively small centrifugal load, the thickness of the first balance weight 11 in the axial direction of the crankshaft is relatively small. By such a method, the crankshaft 1
The torsion damper 19 can be easily mounted on the front side of the first balance weight 11 in the axial direction of the crankshaft without any change in the surrounding conditions of 0, and the rotational balance of the crankshaft 10 can be further improved from this aspect. There is an advantage that can be held.

[0012]

According to the crankshaft according to the present invention, the centrifugal load of the fourth balance weight and the fifth balance weight near the center in the axial direction of the crankshaft is relatively large, and the overall deflection of the crankshaft is reduced. In addition to being able to effectively suppress, the total centrifugal load of each balance weight can be increased by the first to eighth balance weights provided on the crankshaft, and the output of the four-cylinder engine is enhanced. This also makes it possible to keep the rotational balance of the crankshaft good, so that the lubrication in each journal of the crankshaft can always be made good, and the centrifugal load of the first balance weight is relatively small. Therefore, without changing the surrounding conditions of the crankshaft, To the axial direction front side of the first balance weight is featured that the torsional damper can be easily mounted.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram in an embodiment of the present invention.

FIG. 2 is a schematic layout diagram of a conventional device or the like.

[Explanation of symbols]

Reference Signs List 3 crank arm 10 crankshaft 11-18 first balance weight to eighth balance weight 19 torsion damper

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Daisuke Fujii 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Yoshiyuki Watanabe 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi F-term (reference) in Automobile Industry Co., Ltd. 3J033 AA02 AB03 AC02 BA04 BA13 BC06 CA04 CB02 CC01 CD02

Claims (1)

[Claims] In a four-cylinder engine, first to eighth balance weights are sequentially arranged from the front side in the axial direction at positions opposed to the respective crank arms with respect to the crankshaft axis, and the first balance weight is provided. , The third balance weight, the sixth balance weight, and the eighth balance weight each have substantially the same centrifugal load, and the second balance weight,
A crank wherein the fourth balance weight, the fifth balance weight, and the seventh balance weight each have a centrifugal load larger than the centrifugal load, and a torsional damper is mounted on the axially forward side of the first balance weight. shaft.