JPH105923A - Manufacture of crankshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate bending work to be performed for the volume distribution of a material to be forged in the width direction before forging by forging so that the counter weights of a crank arm are arranged on the same side in the width direction, removing burrs, rotating the crank arm by twisting, and arranging the counter weights in a prescribed direction. SOLUTION: A base stock to be forged, to which the volume distribution in the axial direction has been properly performed by roll forming, is prepared. By rough forging, all counter weights 1a', 1b', 1c' and 1d' are worked in the same direction. Finish forging is performed to roughly forged parts, and burrs are removed. The crank arms 1c and 1d of a classification B (crank pin 3b, crank arms 1c, 1d, and counter weights 1c', 1d') are twisted by 180 degree to form them, and are made in a prescribed shape. The crank shaft can be manufactured with a satisfactory yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a crankshaft, and more particularly, to a method of manufacturing a crankshaft without bending a material to be forged in a width direction before forging. The present invention relates to a method of manufacturing a crankshaft which can satisfy (material) and has a high production yield.

[0002]

2. Description of the Related Art Crankshafts for automobiles and the like have conventionally been manufactured by casting or forging. However, in recent years, as the weight and output of engines have been reduced, high strength and high toughness have been required for crankshafts, and demand for forged products has been increasing.

[0003] Crankshafts manufactured by forging are made of square billets or round billets such as medium carbon steel for machine structures, and are formed by roll forming, bending, rough forging (the first step of die forging), finish forging ( (2nd process of die forging) and each process of deburring.

FIG. 4B shows an example of a crankshaft. In the drawings, the left side is a side view of the crankshaft, and the right side is a plan view. The front part 4 and the flange part 5 are omitted from the side view. The crank arms 1a to 1h are provided with large counterweights 1a 'to 1h'. A plurality of the counterweights 1a 'to 1h' are provided at positions deviated from the central axis (XX axis) of the crankshaft. It is also provided not in the same direction but in a predetermined direction with the center axis of the crankshaft (XX axis) interposed therebetween for the purpose of balancing the rotation. And this counter weight 1
It is required that a 'to 1h' be filled with meat (material) at the time of forging.

[0005] In order to fill the counterweights 1a 'to 1h' with meat by the conventional forging method, before the forging, the width direction (Y-Y direction in Fig. 4 (b); It was necessary to distribute the volume of the forged material in the “direction”.

[0006] Among the above-mentioned steps (1) to (3), the bending process is performed to distribute the volume of the material to be forged in the width direction and to enhance the filling of the counterweights 1a 'to 1h' with the meat during forging. Processing. That is, this bending process is performed before forging, and counterweights in the same direction (FIG. 4)
In (b), 1a 'and 1b', 1c 'and 1d', 1e 'and 1f', and
The forged part for forming 1g 'and 1h') must be eccentric to the counterweight side, which is the desired direction. For example, the portion corresponding to the section A in FIG. 4B is eccentrically shifted toward the counterweights 1a 'and 1b', and the portion corresponding to the section B is eccentrically shifted toward the counterweights 1c 'and 1d' in the opposite direction. deep.

[0007] However, if the amount of eccentricity in the case of bending is excessive, deformation outside a predetermined range such as local width expansion occurs, and forging this causes flaws. Therefore, there is naturally a limit to the volume eccentricity that can be given by bending.

Therefore, depending on the shape of the counterweight, the amount of volume eccentricity becomes insufficient, and there may be a case where underfilling occurs even when formed by forging. In order to prevent such underfilling of the counterweight, it is necessary to increase the total volume of the forged material, and as a result, the yield decreases.

In the above-mentioned roll forming, the material to be forged is volume-distributed in the axial direction (the XX direction in FIG. 4B, hereinafter simply referred to as "axial direction") before forging. This is the process. In other words, roll forming is a process of forming a forged material into a stepped shaft for the purpose of volume distribution in the axial direction. In addition to reducing the cross-sectional area of the front part 4 at the tip of the crankshaft, it increases yield near the front part. The purpose is to increase the yield by narrowing down a portion corresponding to a portion having a small required volume such as a crank journal (2a to 2e in FIG. 4A).

As a technique for improving the filling of the counterweight, Japanese Patent Application Laid-Open No. 60-27440 discloses a "forging method for a crankshaft and a mold for rough forging". In the method proposed in this publication, by providing an inclined step surface in the forging die, it is possible to restrict the outflow of burrs and improve the yield. However, even in this method, it is essential to distribute the volume of the forged material in the width direction by performing bending. If the above-mentioned volume distribution is inappropriate, the underfill may occur, the yield may be reduced, and the overload phenomenon may occur due to the overfilling of the forging die with the material.

[0011]

As described above, in order to manufacture a crankshaft by a conventional forging method, before forging,
It was essential to bend and distribute the volume of the forged material in the width direction. Furthermore, even when bending is performed, if the volume distribution is not appropriate, problems such as underfill and reduced yield cannot be avoided.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crankshaft having a high production yield, which can fill a counterweight portion with meat without performing a bending process for distributing a forged material in a width direction before forging. Is to provide a method of manufacturing the same.

[0013]

Means for Solving the Problems The inventors of the present invention have made the following conclusions as a result of repeated studies and experiments for solving the above-mentioned problems.

"All the counterweights are formed in the same direction by forging (rough forging and finish forging), and then deburring is performed. After that, twisting is performed and the required crank arm is rotated to set the counterweight. If it can be arranged in a predetermined direction, it is not necessary to distribute the volume of the material to be forged in the width direction by bending before forging, and the fillability of the counterweight is improved, so that the yield can be increased. " In order to confirm this, as a basic experiment, a conventional crankshaft manufacturing process up to a rough forging was reproduced by a model experiment with respect to a crankshaft in which the counterweight directions differ by 180 degrees. Fig. 2 (a)
Shows the model shape of the target crankshaft.

In the above model experiment, two crank arms each having counterweights 1a 'and 1b' and counterweights 1c 'and 1d' in the same direction with respect to the crankpins 3a and 3b and the crankpins 3a and 3b are used. 1a and 1b, and 1c and 1d are each divided into one section, and the crank journal 2 is interposed therebetween.
Section A (0 ° opposed, different direction) (crank pin 3a,
Crank arms 1a and 1b, counterweights 1a 'and 1b'
), Category B (Crank pin 3b, Crank arm 1c and 1
d, counterweights 1c 'and 1d') were taken as one piece. And JIS S45C 100mm x 100
A model experiment was performed using a square billet of mm as a material.

As described above, roll forming is a process of forming a forged material into a stepped shaft for the purpose of distributing the volume in the axial direction. As a result, the yield near the front portion can be increased by narrowing the cross-sectional area of the front portion at the tip of the crankshaft, and the yield can be increased by narrowing the portion corresponding to a portion having a small required volume such as the crank journal.

As is clear from FIG. 2A, in the shape of the crankshaft targeted in this model experiment, first, the interval between the counterweights is narrow. For this reason, a substantially constant volume is required in the axial direction. Therefore, it is not necessary to distribute the volume in the axial direction to the portion other than the front portion 4 at the front end of the crankshaft and the flange portion 5 at the rear end.
(For the parts of the front part 4 and the flange part 5, see FIG. 4 (b).) Next, the part which does not include the front part 4 and the flange part 5 is targeted.
For this reason, in the part of this model (FIG. 2), axial volume distribution is not required. Therefore, in this model experiment, roll forming was omitted.

That is, the above-mentioned S45C of 100 mm
A 100 mm billet (FIG. 3 (A)) is directly bent, and as shown in FIG. 3 (B), a product (FIG. 2 (A))
8mm counter weight 1
The parts to be forged were shifted to the a ′ and 1b ′ sides, while the parts corresponding to the section B were shifted to the 8 mm counterweights 1c ′ and 1d ′ sides to distribute the volume of the forged material in the width direction. Using the forged material obtained in this manner, rough forging was performed by a normal method. In any of the sections A and B, a large volume was applied to both the counterweight side and the opposite crankpin side. Burrs have occurred.

Next, the shape of the rough forging die was changed to a shape in which the crank arms 1c and 1d were rotated by 180 degrees around the central axis (XX axis), and as shown in FIG. Rough forging was performed so that ', 1b', 1c ', and 1d' were all in the same direction. Note that, similarly to the above case, the roll forming is omitted, and no bending is performed.
The 0-mm billet itself was used as a material to be forged, and was directly mounted on a lower die for rough forging and forged. However, the width direction position of the forged material on the lower mold is the same distance (8 mm) as the eccentric amount when the conventional bending is performed from the center axis (XX axis) of the crankshaft to the position of the counterweight. The position was shifted in the direction. Investigation of the shape after rough forging revealed that it was equivalent to that forged by the conventional method.

Next, a 97 mm × 97 mm square billet whose volume was reduced by 5% was prepared by using the same JIS S45C as the base material as described above, and was placed directly on a lower die for rough forging to forge. did. In this case, the width direction position of the material to be forged on the lower die for rough forging is determined by the center axis (XX axis) of the crankshaft.
By shifting 10 mm to the counterweight side from, molding was possible without underfill.

On the other hand, the same billet of 97 mm × 97 mm as described above is bent in the conventional manner, and the portion corresponding to the section A of the product (FIG. 2 (A)) is 8 mm counterweight 1a ′.
And the part corresponding to section B was also shifted to the 8 mm counterweights 1c 'and 1d' side to distribute the volume of the forged material in the width direction. Then
When rough forging was performed by the conventional method, the underweight occurred in the counterweight portion.

Therefore, the eccentricity was increased to 10 mm so as to secure a required volume on the counterweight side, and the workpiece was bent, and then rough forging was performed by a conventional method. In this case, a forging flaw occurred near the crank journal 2.

As described above, the results of the model experiment show that the position of the forged material in the width direction on the lower die for rough forging is the same distance as the eccentricity given to the forged material by the conventional bending process. (XX axis) to the counterweight side, and forging is performed with the counterweight in the same direction, without bending before forging to distribute the forged material in the width direction to the counterweight portion. It was found that the meat filling could be improved. Further, by shifting the width direction position of the forged material on the lower die for rough forging to the counterweight side larger than the above-mentioned distance, a material having a small volume can be used as the forged material, and the yield increases. This was also confirmed.

Therefore, the material formed into a stepped shaft by narrowing the cross-sectional area as required in addition to the front portion at the tip of the crankshaft by roll forming is used as the material to be forged, and then the above forging is carried out. It is considered that the fillability of the meat to the counterweight portion can be improved and the yield can be further increased without performing bending before forging for volume distribution of the forged material.

Incidentally, in the case of a crankshaft in which it is difficult to obtain a desired shape only by forming by forging, usually,
After deburring, a method of twisting and finishing to a required shape is adopted (for example, Sumitomo Metal Vol. 43, No. 5, (1991)
Year) on page 54).

Therefore, the inventors of the present invention have conducted the above-described model experiment by using the shapes shown in FIG. 1 (counter weights 1a ', 1b', 1c ',
Finish forging and deburring are performed on the roughly forged ones in the same direction (1d 'are all in the same direction), and then the above-mentioned section B (crank pin 3b, crank arms 1c and 1d, counterweight 1c')
And 1d ') to form the crank arms 1c and 1d by twisting 180 degrees. As a result, a desired shape shown in FIG.

That is, it was confirmed that it was possible to manufacture a crankshaft having no problem in the finished product shape and accuracy.

The gist of the present invention based on the results of the above research and experiments is a method of manufacturing a crankshaft described below.

That is, "forging is performed so that the counterweight of the crank arm is arranged on the same side in the width direction, deburring is performed, and then the crank arm is rotated by twisting, so that the counterweight is arranged in a predetermined direction. A method of manufacturing a crankshaft characterized by doing so. "

Here, the "predetermined direction" of the counterweight refers to the direction of the counterweight provided on the crankshaft, which is a product for the purpose of balancing the rotation. As will be described in a later embodiment, for example, in a semi-finished product after forging and deburring, only a group of crank arms whose counter weights are not oriented in the “predetermined direction” as described in a later embodiment. It is also possible to do. Alternatively, all the crank arms of the semi-finished product may be rotated by a required amount, and the counterweight may be arranged in a predetermined direction.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the method for manufacturing a crankshaft according to the present invention will be described below.

First, a slab is manufactured by a normal method from a steel ingot melted by a normal method, and is roll-formed by a normal method. A forged material is prepared in which the sectional area is reduced in accordance with the above and the volume is distributed in the axial direction so as to form a stepped shaft shape. Next, the forged material is carried into a lower die for rough forging. At this time, the position of the forged material in the width direction is set to a position appropriate for filling the counterweight according to the shape of the counterweight of the product, for example, the crankshaft by the same distance as the amount of eccentricity when conventional bending is performed. Center axis (XX
(Axis) in the direction of the counterweight.

After placing the forged material in the lower die for rough forging as described above, rough forging is immediately performed, followed by finish forging and deburring. When the deburring is completed in such a process, a semi-finished crankshaft product in which all the counterweights are present on the same side in the width direction as shown in FIG. 1 is completed.

Next, the semi-finished product after the above deburring is subjected to twisting and rotation of the crank arm, and each of the counterweights is arranged in a predetermined direction to obtain a desired shape shown in FIG. Is obtained.

As a specific example, the number of cylinders is four, that is, there are four crankpins, and each crankpin is sandwiched between two crank arms having counterweights oriented in the same direction. Consider a crankshaft with a crank arm having two counterweights. In this case, as the final product shape, the four counterweights at both ends and the four counterweights at the center are different from each other by 180 degrees as shown in FIG.

In the case of the above crankshaft, after deburring,
Twist the four crank arms at both ends to rotate 180 degrees with respect to the four center crank arms. In such a twisting process, the four crank arms at the center may be fixed and the crank arms at both ends may be rotated 180 degrees, or the four crank arms at the center may be rotated 90 degrees, At the same time, the four crank arms at both ends may be rotated 90 degrees in opposite directions.

FIG. 4A shows an example in which the four crank arms 1a, 1b, 1g and 1h at both ends are rotated by 180 degrees.
In addition, the front part 4 and the flange part 5 are omitted in the side view.

According to the method of the present invention, there is no need to distribute the volume of the forged material in the width direction. That is, the bending process can be omitted through the following steps.

First, a forged material prepared by roll forming as described above and appropriately performing volume distribution in the axial direction is prepared. Next, the width direction position where both the counterweight and the crankpin (the crankpin in the width direction is opposite to the center axis (XX axis) in the width direction) is filled with the meat as described above. If a forged material is installed in a lower die for rough forging, rough forging can be performed without performing conventional bending.

[0040]

【Example】

(Example 1) JIS S45C was made of raw steel with a cross section of 100
After heating a billet of mm × 100 mm to 1260 ° C., it is roll-formed, and the volume distribution of the forged material in the axial direction is adjusted so that the tip portion of the billet corresponding to the front part of the crankshaft has a cross section of 50 mm × 50 mm. went.

Next, this was bent at 1200 ° C. by an ordinary method to prepare a forged material by a conventional method. That is, the two crank arms and the crank pins between them (for example, the crank arms 1a and 1b and the crank pin 3a) are defined as one section, and the central axis (X- The volume of the forged material was distributed in the width direction so that the shape shifted from the X-axis) by 8 mm toward the counterweight side.

Thereafter, the forged material is subjected to rough forging, finish forging and deburring at 1150 ° C. by a usual method.
A crankshaft having four cylinders and eight counterweights as shown in FIG.

On the other hand, according to the following method of the present invention, FIG.
4 cylinders and 8 counterweights as shown in (b)
Was manufactured.

That is, first, as in the above case, JI
100 mm x 100 m cross section using S S45C as material steel
After the m billet was heated to 1260 ° C., it was roll-formed and subjected to an axial volume distribution to prepare a forged material. Next, the material to be forged is moved 8 m from the center axis of the crankshaft (XX axis) to the counterweight side with respect to the lower die for rough forging.
It is installed at a position eccentric in the width direction by m and rough forging is performed, and further, forging and deburring are performed to produce a semi-finished product in which all the counterweights shown in FIG. processed.

Thereafter, using a hydraulic press at 1050 ° C.
Then, the four crank arms at the center are fixed, and the crank arms at both ends are twisted by 180 degrees (the four crank arms 1a, 1b, 1g, and 1h at both ends are rotated by 180 degrees). The crankshaft having four cylinders and eight counterweights having the shape shown in FIG.

For each of the conventional method and the method of the present invention, 50 crankshafts were manufactured, and their appearance was examined.

As a result, it was confirmed that the crankshaft manufactured by the method of the present invention had the same dimensional accuracy as that of the crankshaft manufactured by the conventional method, and that there was no underfill in the counterweight portion. On the other hand, in the crankshaft manufactured by the conventional method, one of the counterweights was found to be slightly underfilled.

Example 2 A billet having a cross section of 97 mm × 97 mm made of JIS S45C as a material steel was heated to 1260 ° C., then roll-formed, and the billet tip portion corresponding to the front part of the crankshaft was 50 mm × 50 mm. The volume of the forged material was distributed in the axial direction so as to have a cross section.

Next, this was bent at 1200 ° C. by an ordinary method to prepare a forged material by a conventional method. That is, the two crank arms and the crank pins between them (for example, the crank arms 1a and 1b and the crank pin 3a) are defined as one section, and the central axis (X- The volume of the forged material was distributed in the width direction so that the shape shifted from the X-axis) by 8 mm toward the counterweight side.

Thereafter, the material to be forged is subjected to rough forging, finish forging and deburring at 1150 ° C. in a usual manner to obtain a crankshaft having four cylinders and eight counterweights as shown in FIG. Was prepared.

The cross section used in this embodiment is 97 mm ×
The 97 mm billet is obtained by improving the yield by 5% with respect to the billet having a cross section of 100 mm × 100 mm used in the first embodiment.

On the other hand, according to the following method of the present invention, FIG.
4 cylinders and 8 counterweights as shown in (b)
Was manufactured.

That is, first, as in the above case, JI
A billet having a cross section of 97 mm × 97 mm made of S S45C as a material steel was heated to 1260 ° C., and then roll-formed.
A volume distribution in the axial direction was performed so as to have a cross section of 0 mm × 50 mm to prepare a forged material. Next, the material to be forged is moved to the lower die of the rough forging with respect to the center axis of the crankshaft (XX).
From the shaft) to the counterweight side at a position eccentric by 10 mm in the width direction, rough forging, and further forging,
Deburring was performed to obtain a semi-finished product having a shape in which the counterweights shown in FIG. 4A were all disposed on the same side in the width direction.

After that, using a hydraulic press at 1100 ° C.
Then, the four crank arms at the center are fixed, and the crank arms at both ends are twisted by 180 degrees (the four crank arms 1a, 1b, 1g, and 1h at both ends are rotated by 180 degrees). The crankshaft having four cylinders and eight counterweights having the shape shown in FIG.

For each of the conventional method and the method of the present invention, 50 crankshafts were manufactured, and their appearance was examined.

As a result, the crankshaft manufactured by the method of the present invention has the same dimensional accuracy as that of the crankshaft manufactured by the conventional method in the first embodiment, and there is no underfill in the counterweight portion. It could be confirmed. That is, the yield of crankshaft production could be increased by 5% by the method of the present invention.

On the other hand, in a crankshaft manufactured by the conventional method,
Underweight was observed in the counterweight in all 50 tubes.

[0058]

According to the method of the present invention, the counterweight portion can be filled with meat (material) without performing a bending process for distributing the forged material in the width direction before forging. . Therefore, the crankshaft can be manufactured with high yield, and the industrial effect is great.

[Brief description of the drawings]

FIG. 1 is a view showing a shape in which a counterweight of a crank arm is forged so as to be arranged on the same side in the width direction according to the method of the present invention.

FIG. 2 is a view showing a model shape of a forged crankshaft.
(A) is a plan view and (B) is a side view.

FIG. 3 is a view showing a material billet and a shape after bending of a crankshaft having the model shape of FIG. 2; (A) is a billet, and (b) is a shape after bending.

FIG. 4 is a view showing a method of manufacturing a crankshaft having four cylinders and eight counterweights according to the method of the present invention.
(A) is a shape after deburring through rough forging and finish forging, and (b) is a crankshaft that has been twisted and finished to a required shape.

[Brief description of reference numerals]

 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h: Crank arm 1a ', 1b', 1c ', 1d': Counter weight 2, 2a, 2b, 2c, 2d, 2e: Crank journal 3a, 3b, 3c, 3d: Crank pin 4: Front of crankshaft 5: Flange of crankshaft

Claims (1)

[Claims] 1. After forging so that the counterweight of the crank arm is arranged on the same side in the width direction, deburring is performed, and then the crank arm is rotated by twisting so that the counterweight is arranged in a predetermined direction. A method of manufacturing a crankshaft, comprising: