JP2002168228A - Crankshaft and unbalance correction method for crankshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the unbalance correction method for a crankshaft that can reliably correct unbalance of the crankshaft with an easy work, and avoid the scrap of a raw material, and thus reduce a manufacturing cost. SOLUTION: When there is no compensation for correcting unbalance since a balancing position is placed to a crank pin 3 side over a target range, a weight reducing hole 10 is formed on an arm 2. Thus, the weight at the crank pin side is reduced, the balance position shifts to a counterweight 4 side over the target range, thereby and thereafter, an unbalance correction hole is formed on the counterweight 4, so that unbalance can be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft of an engine and a method of correcting imbalance thereof.

[0002]

2. Related Background Art As is well known, for the purpose of reducing engine vibration and increasing the rotation speed, a crankshaft is subjected to an unbalance correction operation after completion of forging or machining. Since this correction work is performed by drilling the outer peripheral surface of the counterweight with a drill to reduce the weight, in the forging process in advance, the actual balance position with respect to the target range is set in order to provide a balance correction allowance. The material of the crankshaft is molded so that it is slightly on the counterweight side.

[0003]

The balance position of the crankshaft before the correction depends on the shape of the material by forging. However, since the variation in the shape by forging is large, the balance position before the correction is the target. In some cases, there is no correction allowance on the crankpin side of the range. At this time, even if the weight on the counterweight side is reduced by the balance correction, the material is only to be discarded because the balance position moves away from the target range, resulting in an increase in manufacturing cost. .

As a countermeasure, it is conceivable to set the balance position of the crankshaft sufficiently on the countershaft side from the target range in consideration of the variation due to forging. As a result, the amount of weight reduction required, specifically, the amount of drilling, increases drastically, and it was hardly a practical measure.

An object of the present invention is to make it possible to reliably correct the imbalance of the crankshaft by a simple operation,
An object of the present invention is to provide a crankshaft capable of avoiding material disposal and reducing manufacturing costs, and an imbalance method for the crankshaft.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, the crank journal and the crankpin are connected by an arm, and the outer peripheral surface of the crank journal and the outer peripheral surface of the crankpin communicate. An oil passage is formed, a counterweight is extended from the arm to the opposite side around the crank journal, and an unbalance correction hole is formed on the outer periphery of the counterweight. A weight reduction hole was formed so as to be located on the outer peripheral side of the oil passage as the center and on the outer peripheral side of the axis of the crankpin.

Therefore, at the stage before the unbalance correction, if the balance position is on the crankpin side from the target range and there is no unbalance correction allowance, an unbalance correction hole is formed to reduce the weight on the counterweight side. Even though the imbalance cannot be corrected, the weight reduction hole reduces the weight on the crankpin side, so the balance position moves beyond the target range to the counterweight side and the imbalance can be corrected. Become.

In addition, since the weight reduction hole is located near the outer periphery of the arm, compared with the case where the weight reducing hole is located closer to the inner periphery,
The influence on the balance position of the crankshaft is increased, and the desired movement amount of the balance position can be achieved even with a small weight reduction hole. According to the invention of claim 2, the weight reducing hole is formed on a line connecting the axis of the crank journal and the axis of the crankpin.

Therefore, the balance position moves to the counterweight side along the line without shifting in the direction orthogonal to the line due to the formation of the weight reducing hole. If the balance position is shifted in a direction perpendicular to the line, the unbalance correction hole may cause the balance to be out of the area in which the balance can be corrected, but such a situation is prevented beforehand. Moreover, the arm has the largest thickness on the line, which is advantageous in terms of strength.

According to the third aspect of the present invention, the arm connecting the crank journal and the crank pin is located on the outer periphery side of the lubricating oil passage centering on the crank journal and on the outer periphery side of the axis of the crank pin. The first step of forming the weight reducing hole as described above, the second step of rotating the crankshaft to measure the balance position, and setting the crankshaft balance position to a predetermined target based on the measurement result of the second step. A third step of forming an unbalance correction hole in the outer periphery of the counterweight extending from the arm so as to fall within the range.

Therefore, even if the balance position is on the crankpin side of the target range and there is no allowance for unbalance correction at the stage before the unbalance correction, the weight reduction hole is formed in the arm in the first step. Then, the weight on the crankpin side is reduced, and the balance position moves to the counterweight side beyond the target range. As a result, a balance correction allowance is secured, so that an unbalance correction hole is formed in the counterweight in the third step based on the measurement result of the balance position in the subsequent second step, and the balance position is set within the target range. It can be moved to correct the imbalance.

Further, since the weight reducing hole is located near the outer periphery of the arm, compared to the case where the weight reducing hole is located closer to the inner periphery,
The influence on the balance position of the crankshaft is increased, and the desired movement amount of the balance position can be achieved even with a small weight reduction hole. Preferably, the inner diameter of the weight reducing hole is set to 0.4 or less with respect to the outer diameter of the crankpin. In other words, as shown in FIG.
Since the bending strength ratio of the crankshaft sharply decreases around the vicinity of 4, the reduction in the bending strength ratio of the crankshaft can be minimized by setting the bending strength ratio to 0.4 or less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a method for correcting imbalance of a crankshaft for a V-type six-cylinder engine will be described below. First, the crankshaft before the unbalance correction work is performed will be described. The material of the crankshaft is formed by forging, and thereafter, machining of a crank journal, a crankpin, an oil passage and the like is performed. FIG. 1 is a front view showing a crankshaft to which the unbalance correction method according to the present embodiment is applied. Crank journals 1 are provided at four positions, and two A crank pin 3 for each cylinder is provided. Each arm 2 is appropriately provided with a counterweight 4. Each counterweight 4 is provided with a crank pin 3 centered on the axis C1 of the crank journal 1 (that is, the rotation center of the crankshaft) in order to offset the inertial weight of the piston. It extends on the opposite side.

A large number of oil passages are formed in the crankshaft. These oil passages connect the adjacent crank journal 1 and the crankpin 3 to each other, and when the engine is operating, the crankpin 1 is moved from the crank journal 1 side to the crankpin 3. The oil is supplied to the side. FIG. 2 is a partially enlarged view showing the front side of the crankshaft, and FIG. 3 is a sectional view taken along line III-III of FIG. 2. In these figures, the oil passage 5 at the forefront is shown, but Passage 5
(Shown in FIG. 1) has exactly the same arrangement. Less than,
The arrangement state will be described using the oil passage 5 at the forefront as an example.

As shown in FIG. 2, the oil passage 5 is drilled from the arm 2 on one side of the crank pin 3 to reach the crank journal 1 through the inside of the crank pin 3 and its opening is closed by a plug 6. Have been. The oil passage 5 is disposed in a line L connecting the axis C1 of the crank journal 1 and the axis C2 of the crank pin 3 shown in FIG. 3 is in communication with an injection hole 8 penetrating in the radial direction. As a result, the oil passage 5
Opens at the outer peripheral surfaces of the crank journal 1 and the crank pin 3 through the injection holes 7 and 8, and supplies oil from the crank journal 1 side to the crank pin 3 side as described above.

FIG. 4 is a schematic diagram showing a balance position and a target range of the crankshaft.
The line L connecting the axes C1 and C2 is defined as the y direction, and the direction orthogonal thereto is defined as the x direction. In a V-type six-cylinder engine, a target range T (a fan-shaped hatching area in the figure) of the balance position is set slightly closer to the counterweight 4 than the axis C1 of the crank journal 1 in consideration of the inertial weight of the piston and the like. I have. Then, in the unbalance correction work described later, the unbalance is corrected by cutting the counterweight 4 side so that the balance position falls within the target range T.
In order to secure the balance adjustment allowance, the balance position is set closer to the counterweight 4 than the target range T, for example, as indicated by P2 in the drawing.

Next, the procedure of the unbalance correction method according to the present embodiment will be described. First, the balance position is measured by rotating the crankshaft while being supported by the center holes at both ends, and it is determined whether the measured balance position is on the counterweight side from the target range. Unless unexpected variations occur in the shape of the material due to consideration of the balance position in the forging stage described above, in most cases, P2 in FIG.
As shown in (2), the balance position is located on the counterweight 4 side of the target range T. In this case, it is considered that the imbalance can be corrected only by ordinary work, and as shown in FIGS. 1 and 3, a predetermined position, number, An unbalance correction hole 9 having a depth is formed. As a result, the weight of the counterweight 4 side is reduced, and P3
The balance position moves toward the crankpin 3 and enters the target range T as shown in FIG. Note that the angle θ in the figure indicates an area where the balance can be corrected, and corresponds to a range where the unbalance correction hole 9 can be formed in the counterweight 4.

The above-described measurement of the balance position is performed on the front end side and the rear end side of the crankshaft. Correspondingly, the drilling of the unbalance correction hole 9 is performed on the frontmost and rearmost counterweights 4. Is done. The above modification work
Very common. On the other hand, as shown by P1 in FIG. 5, when the balance position on the front end side or the rear end side is closer to the crankpin 3 than the target range T, the imbalance cannot be corrected as it is. As shown in
For the balance position on the front end side, a weight reduction hole 10 is formed in the frontmost arm 2, and for the balance position on the rear end side, the weight reduction hole 10 is formed in the rearmost arm 2 (first).
Process). Therefore, the weight on the crankpin 3 side is reduced, and the balance position moves to the counterweight 4 side in the y direction in FIG. 5 and reaches the position P2 beyond the target range T, for example. By the above operation, the balance correction allowance is surely secured.

The inner diameter and depth (in other words, the amount of weight reduction) of the weight reduction hole 10 are determined in advance, and are set to be equal to or more than the maximum error of the balance position that can occur due to the variation in the shape of the material during forging. Needless to say. After that, it is the same as the above case, the balance position is measured again (second step), and based on the measurement result, an unbalance correction hole 9 is appropriately formed in the outer peripheral surface of the counterweight 4 to adjust the balance position. It is moved within the target range T (third step). This completes the balance correction work.

Here, as shown in FIG. 2, the weight reducing hole 10 is in a direction perpendicular to the surface of the arm 2, that is, the axis C1 of the crank journal 1 and the crank pin 3 to facilitate the cutting of the drill. C2 is formed at a predetermined angle. As shown in FIG. 3, the position of the weight reducing hole 10 is the same as that of the oil passage 5 in the axial center C.
1 and C2, and on the outer side of the oil passage 5 around the crank journal 1 which is the center of rotation, and as shown in FIG. 2, on the outer side of the axis C2 of the crank pin 3. Is arranged to be located at
Although its tip reaches the inside of the crank pin 3, it does not communicate with the oil passage 5 and is completely independent.

The inner diameter d of the weight reducing hole 10 is set so that the ratio d / D to the outer diameter D of the crankpin 3 is 0.3. FIG. 6 shows the test results of the bending strength ratio of the crankshaft when the ratio d / D is changed. It can be seen that the bending strength ratio sharply decreases around the boundary where the ratio d / D is around 0.4. . Therefore, by setting the inner diameter d of the weight reducing hole 10 so that the ratio d / D is 0.4 or less, preferably 0.3 or less based on FIG. Not
The advantage in the work of correcting imbalance by the above-described weight reduction hole 10 can be obtained.

As described above, in the crankshaft unbalance correcting method according to the present embodiment, the weight reducing hole 10 is formed even when the balance adjustment allowance is not ensured due to the variation of the material shape at the forging stage. By moving the balance position toward the counterweight 4, a balance adjustment margin can be secured. Therefore, even a material that was conventionally discarded as being unbalance-correctable can be commercialized as a crankshaft with the imbalance corrected. In addition, it is not necessary to unnecessarily set the balance position on the countershaft 4 side in consideration of the variation due to forging, so the drilling amount when forming the unbalance correction hole 9 becomes small, and the correction work is performed. Can be made easier,
Manufacturing costs can be significantly reduced.

In addition, as a result of arranging the weight reducing hole 10 on the outer side of the oil passage 5 and on the outer side of the axis C2 of the crank pin 3, as shown in FIG.
0 is located at the outermost periphery of the arm 2. That is,
Compared to the case where the weight reduction hole 10 is arranged on the inner peripheral side, the influence on the balance position of the crankshaft is large, so that even the small weight reduction hole 10 can achieve the desired movement amount of the balance position, and This is more advantageous in terms of the manufacturing cost and strength described above.

Further, since the weight reducing hole 10 is independent without communicating with the oil passage 5, the weight reducing hole 1
There is no danger of oil flowing into zero. In other words, when the weight reduction hole 10 communicates with the oil passage 5, it is necessary to close the opening of the weight reduction hole 10 with a plug, for example, in order to prevent a decrease in oil pressure due to oil outflow. Such measures are not required at all.

On the other hand, a line L connecting the crank journal 1 and the axis C1, C2 of the crank pin 3
As shown by solid arrows in FIG. 5, the balance position is determined by the counterweight 4 along the y-direction.
Will move to the side. In other words, when the weight reducing holes 10 are provided other than on the line L, the balance position may shift in the x direction and deviate from the area of the angle θ at which the balance can be corrected, as indicated by the broken arrow. Thus, such a situation can be prevented beforehand, and the imbalance can be more reliably corrected. Moreover, since the arm 2 has the largest thickness on the line L, it is advantageous in terms of strength.

Although the embodiment has been described above, aspects of the present invention are not limited to this embodiment. For example, in the above-described embodiment, the crankshaft imbalance correction method for a V-type 6-cylinder engine is embodied. However, the type of the engine is not limited to this. For example, a V-type 8-cylinder, a 12-cylinder, or an in-line 4 The present invention may be embodied in a method for correcting imbalance applied to a cylinder or a six-cylinder crankshaft.

In the above embodiment, the weight reduction hole 10 is formed in the direction perpendicular to the surface of the arm 2 on the line L connecting the axes C1 and C2. However, the invention is not limited to this. Instead, for example, the weight reducing hole 10 may be formed at a position slightly deviated from the line L, or the drilling angle may be changed.

[0028]

As described above, according to the crankshaft of the present invention and the method for correcting the imbalance thereof, the imbalance of the crankshaft can be surely corrected by a simple operation, thereby avoiding the disposal of the material. Manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a crankshaft to which an unbalance correction method according to an embodiment is applied.

FIG. 2 is a partially enlarged view showing a front side of a crankshaft.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a schematic diagram showing a state of movement of a balance position by an unbalance correction hole.

FIG. 5 is a schematic diagram showing a movement state of a balance position by a weight reduction hole.

FIG. 6 is an explanatory diagram showing the results of testing the bending strength ratio of the crankshaft when the ratio d / D is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crank journal 2 Arm 3 Crank pin 4 Counter weight 5 Oil passage 9 Unbalance correction hole 10 Weight reduction hole L line T Target range C1, C2 Shaft center

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Teruyuki Doi 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 3J033 AA02 AC01 BA01 CC03

Claims (3)

[Claims] An oil passage connecting an outer peripheral surface of the crank journal to an outer peripheral surface of the crank pin;
A crankshaft having a counterweight extending from the arm toward the opposite side around the crank journal and having an unbalance correction hole formed on the outer periphery of the counterweight. A crankshaft, wherein a weight reducing hole is formed so as to be located on an outer peripheral side of the oil passage and on an outer peripheral side of an axis of the crankpin. 2. The crankshaft according to claim 1, wherein the weight reduction hole is formed on a line connecting an axis of the crank journal and an axis of the crankpin. 3. An arm connecting the crank journal and the crank pin, a weight reducing hole is provided so as to be located on the outer peripheral side of the lubricating oil passage around the crank journal and on the outer peripheral side with respect to the axis of the crank pin. A second step of measuring the balance position by rotating the crankshaft; and setting the balance position of the crankshaft within a predetermined target range based on the measurement result of the second step. In order to fit in
A third step of forming an unbalance correction hole in the outer circumference of the counterweight extending from the arm.