JPH1029032A - Die for forging crank shaft, and manufacture of crank shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the service life of a die by filling the molten metal onto a counter weight without increasing the volume of a work to be forged, and reducing the load on the die. SOLUTION: A counter weigh 3c is expanded in the direction (A-A direction) orthogonal to the die forging direction (Z-Z direction) during the forging, and the forming shape is carved so that burrs 3d to be generated in the forging is protruded from the space between upper and lower dies 1, 2 at the top point H of a counter weight expansion part. Forging is performed with the die forging direction (Z-Z direction) is orthogonal to the counter weight expansion direction (A-A direction) of a crank arm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a die for forging a crankshaft and a method for manufacturing a crankshaft.

[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, roughing (the first step of die forging), and finishing ( (2nd process of die forging) and each process of deburring.

FIG. 4 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 crank arms 4a to 4h of the crankshaft are provided with counterweights 4a 'to 4h' having a large volume.
As shown in FIG. 4, the shape of the counter weights 4a 'to 4h' is such that the center axes of the crank pins 5a to 5d to which the crank arms 4a to 4h are connected and the crank journals 6a to 4h.
It overhangs a plane passing through the central axis of 6e. In the side view, the front part 7 and the flange part
8 is omitted.

Conventionally, in die forging of a crankshaft (finishing with the above-described rough driving), since the die design is easy, the die driving direction (forging direction) is set to the extending direction of the counterweight (the side surface in FIG. 4). (For example, AA direction in the figure).

That is, the above-mentioned thin plate-shaped engraved portion is filled with meat (material) by forging (stamping) using upper and lower dies having a thin plate-shaped engraved shape corresponding to the overhang shape of the counterweight. Then, the counterweight was formed. Figure 2 shows the conventional upper mold 1 and lower mold 2
The following shows how the counterweight is formed when using the method.
The forged material 3 is forged from the direction (Z-Z direction) that coincides with the overhang direction (AA direction) of the counterweight 3C using the upper and lower dies 1 and 2 in which a thin plate-shaped engraving is inserted. Thus, it is formed into a desired shape. In FIG. 2, a part of FIG. 3 which is a part of the crankshaft of FIG. 4 is taken out and shown. In FIG. 2, 1 is an upper die, 2 is a lower die, 3 is a forged material, 3a is a crankpin, 3b is a crank journal, 3c is a counterweight, and 3d is a burr.
Reference numeral 3e denotes a burr holding portion provided around the die-shaped engraved portion of the mold for the purpose of reducing the thickness of the burr and improving the filling of the meat with the product. H is the overhang height of the counterweight, and t is defined as the thickness of the counterweight. In FIG. 2, the crank pin 3a and the crank journal 3b are omitted for simplicity.

However, in the above-described conventional method of forging a crankshaft using a mold, it is sometimes difficult to fill a thin plate-shaped engraved portion with meat. In particular, in many cases, the counterweight was not filled with meat in a crankshaft having a small counterweight thickness t in the axial direction and a crankshaft having a large overheight height h of the counterweight.

If the counterweight is not full of meat, there is a problem that the counterweight loses thickness and the rotational balance of the crankshaft is lost. Therefore,
Conventionally, in order to fill the counterweight with meat, a surplus volume is given to the forged material. However, when an excessive volume is given to the forged material, the material yield is reduced.

As a technique for improving the filling of the counterweight, for example, Japanese Patent Application Laid-Open No. 60-27440 discloses a technique.
A "method for forging a crankshaft and a mold for rough forging" is disclosed. The method proposed in this publication aims to improve the yield by providing an inclined step surface in the forging die to restrict the outflow of burrs. Therefore, in the above method, the surface pressure in the burr holding portion provided around the product shape engraving portion of the mold increases and the forming load increases, so that a large-sized forging facility is required. Furthermore,
As the load on the mold increases, the life of the mold also decreases.

[0010]

As described above, conventionally, when forging a crankshaft, (a) it is difficult to fill the counterweight with meat, so that the counterweight may be thinned,
(B) When the underfill is prevented, the yield is reduced due to the need to increase the volume of the material to be forged, or (c)
Problems such as an increase in the load on the mold were inevitable.

[0011] The present invention provides a crank capable of filling the counterweight with meat without increasing the volume of the material to be forged, reducing the load on the mold, and achieving a longer life of the mold. An object of the present invention is to provide a method for manufacturing a shaft and a forging die for a crankshaft used during forging.

[0012]

To solve the above-mentioned problems, the present inventors have developed a counterweight 3c shown in FIG.
A model experiment was conducted to investigate the fillability of the counterweight with meat for a portion composed of the crank arm having the above, the crank pin 3a and the crank journal 3b.

As shown in FIG. 2, using a forged material of 100 mm × 100 mm square billet of JIS S45C, upper and lower forging dies 1 and 2 having the same shape as the conventional shape are used to form a die (ZZ). Direction) was matched with the direction of extension of the counterweight (A-A direction), and forging was performed. In addition,
Upper and lower forging dies 1 and 2 are counterweight thickness
The ratio (h / t), which is the ratio of t to the overhang height h (h / t) is 4.3, is defined as a reference shape, and this h / t is 4.3 to 7.0.
A series of samples that had been changed up to that point were used. In this case, h / t
When the value exceeds 5.0, the underweight is generated in the counterweight, and as the thickness t is reduced and the height h is increased, the thickness is increased.

Next, JIS S45C 100 mm × 100
As shown in FIG. 1, using a forged material having a square billet of mm, the vertical direction is such that the stamping direction (Z-Z direction) is perpendicular to the overhang direction (AA direction) of the counterweight. Forging was performed by changing the shapes of the forging dies 1 and 2. In this experiment, the upper and lower forging dies 1 and 2
Is a reference shape having a ratio (h / t) of 4.3, which is the ratio of the thickness t of the counterweight to the overhang height h, and changed this h / t from 4.3 to 7.0. A series was used. In this experiment, the counterweight was thinned by forging according to the conventional method shown in FIG.
Was greater than 5.0, there was no problem with the fillability of the meat to the counterweight, and the molding could be completed without any underfill.

Further, in the conventional method shown in FIG. 2, the counterweight is filled with meat (h / t is 5.
0), JIS S45C was used as the base material, and the volume was set to 1 for the above-mentioned square billet of 100 mm x 100 mm.
Forging was performed by the method shown in FIG. 1 described above using a 95 mm × 95 mm square billet reduced by 0% as a material to be forged.
As a result, forging could be performed without causing underfill in the counterweight.

As described above, it is apparent from the results of the model experiment that as shown in FIG. 1, by performing forging with the stamping direction perpendicular to the direction in which the counterweight extends, the filling of the counterweight is enhanced. Became. Further, it has been clarified that the material yield can be increased by the forging by the method of FIG. 1 with respect to the product shape which does not cause the underfill by the forging by the conventional method of FIG.

The gist of the present invention based on the above experimental results is the following (1) a crankshaft forging die and (2) a method of manufacturing a crankshaft.

(1) As shown in FIG. 1, the counterweight 3c projects in the direction (AA direction) perpendicular to the stamping direction (ZZ direction) during forging, and burrs generated during forging. A crankshaft forging die characterized in that a molding shape is engraved so that 3d is bitten from between upper and lower dies 1 and 2 at a vertex H of a counterweight overhang portion.

(2) As shown in FIG. 1, the stamping direction (Z
A method for manufacturing a crankshaft, characterized in that forging is performed such that a direction (Z direction) is perpendicular to a direction of extension of a counterweight (AA direction) of a crank arm.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below.

First, a steel slab is manufactured by a normal method from a steel ingot melted by a normal method, and is roll-formed by a normal method.
For a portion corresponding to 8, etc., a forged material is prepared in which the cross-sectional area is reduced as necessary and the volume is distributed in the axial direction so as to form a stepped shaft shape. Then, it bends,
For each part corresponding to the counterweight of the forged material, the volume of the forged material is changed in the width direction (so that the shape is shifted from the central axis of the crankshaft (for example, the XX axis in FIG. 4) to the counterweight side). For example, it is eccentric in the YY direction in FIG. The processing before such forging (stamping) is the same as the case of manufacturing a crankshaft by a conventional method.

Next, the forged material is carried into a roughing die and roughed. In this case, the counterweight overhangs in a direction perpendicular to the stamping direction at the time of forging, and burrs generated at the time of roughing are formed at the apex of the counterweight overhang portion on the roughing die. Use the one engraved with the molded shape so as to bite out from between. By using the above roughing die,
Forging can be performed with the rough striking direction perpendicular to the direction of extension of the counterweight of the crank arm.

Subsequently, the forged material to be roughly beaten is loaded into a die for finish-strike while being held in the same direction (in the direction of rough strike), and is subjected to finish-strike. In this case, the counterweight also protrudes in the direction perpendicular to the direction of the stamping at the time of forging, and burrs generated at the time of the final striking are formed at the top of the counterweight overhang portion. Use the one engraved with the molded shape so as to bite out from between. By using the above-described finishing die, forging can be performed with the finishing driving direction perpendicular to the direction of extension of the counterweight of the crank arm.

After performing the above-described finish driving, the forged material is held in the same direction (in the direction of the finish driving).
A desired crankshaft can be obtained by deburring.

According to the above-mentioned method of the present invention, the fillability of the meat to the counterweight is increased, the yield can be improved, and the burr volume can be reduced, so that the load on the mold can be reduced. it can.

The die for forging a crankshaft according to the present invention is, for example, JIS S like a conventional die for a crankshaft.
Using KD61 as a base material, smelting is performed by a normal method, then a steel slab is hot forged, and further subjected to heat treatment of annealing and quenching and tempering to use a steel material adjusted to a desired strength and toughness. Obtained by engraving in a manner.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0028]

【Example】

(Example 1) JIS S45C with steel as the cross section is 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. That is,
Two crank arms and a crank pin between them (for example, crank arms 4a and 4b and crank pin 5a in FIG. 4)
Is defined as one section, and in the width direction, the shape is shifted from the central axis of the crankshaft (the XX axis in FIG. 4) to the counterweight side by 8 mm for each portion of the material to be forged corresponding to each section. The volume distribution of the forged material was performed.

Thereafter, the above-mentioned forged material is roughly beaten at 1150 ° C. by a conventional method using upper and lower dies having a conventional thin plate-shaped engraved JIS SKD61 as a base material. Hitting, then deburring,
A crankshaft having four cylinders and eight counterweights shown in FIG. 4 was manufactured.

On the other hand, a crankshaft having four cylinders and eight counterweights was manufactured by the following method of the present invention.

First, a billet having a cross section of 100 mm × 100 mm made of JIS S45C as a material steel was subjected to the same roll forming and bending as described above to prepare a forged material.

Next, the forged material was carried into a roughing die at 1150 ° C. and roughened. In this case, the roughing die is made of JIS SKD61 as a base material, and is formed by engraving a molding shape such that the counterweight projects in a direction perpendicular to the die-casting direction at the time of forging according to the present invention.
At the top of the overhanging portion of the counterweight, burrs generated during forging are engraved with a molding shape so as to bite between the upper and lower molds, in other words, the apex of the overhanging portion of the counterweight to be formed is up and down. The center of the burr that bites out from between the molds in the thickness direction was used. By using the above-described roughing die, forging can be performed with the roughing direction perpendicular to the direction of extension of the counterweight of the crank arm (FIG. 1).
reference).

The overall shape engraved on the upper and lower dies is the same as the conventional rough hitting shape according to the above-described ordinary method, and is from the central axis of the crank journal to the overhanging portion apex H of the counterweight. The distance is 65 mm.

Next, the forged material for roughing was carried into a finishing die while being held in the same direction (in the direction of roughing), and was forged at 1100 ° C. In this case, the die for finishing is also made of JIS SKD61 as a base material similarly to the above-mentioned die for roughing, and the counterweight is stretched in a direction perpendicular to the die-casting direction at the time of forging according to the present invention. A counter in which the molding shape is engraved so that the burrs generated at the time of forging and the burrs generated during forging bite out between the upper and lower molds at the apex of the counterweight overhang. The one in which the apex of the overhang portion of the weight is the center in the thickness direction of the burr that bites between the upper and lower molds was used. By using the above-described die for finish driving, forging can be performed in a direction perpendicular to the direction in which the crank arm extends the counterweight, as in the case of rough driving. The overall shape engraved on the upper and lower molds is the same as the conventional finish stamping shape by the ordinary method described above.

Immediately after the above-mentioned finishing, deburring was performed to complete the manufacture of the crankshaft.

For each of the above-described conventional method and the method of the present invention, 30 crankshafts were manufactured, and their appearance was examined.

As a result, the crankshaft manufactured by forging (die stamping) using the mold according to the present invention has the same dimensional accuracy as that of the crankshaft manufactured by the conventional method, and has the same quality as forging flaws. It was confirmed that no abnormality occurred.

Example 2 A billet having a cross section of 95 mm × 95 mm made of JIS S45C as a material steel was heated to 1260 ° C. and then roll-formed, and the billet tip portion corresponding to the front part of the crankshaft had a size of 50 mm × 50 mm. The volume of the forged material was distributed in the axial direction so as to have a cross section.

Next, as in the case of Example 1, the material whose volume was distributed in the axial direction was bent at 1200 ° C. by an ordinary method to prepare a forged material. That is,
Two crank arms and a crank pin between them (for example, crank arms 4a and 4b and crank pin 5a in FIG. 4)
Is defined as one section, and in the width direction, the shape is shifted from the central axis of the crankshaft (the XX axis in FIG. 4) to the counterweight side by 8 mm for each portion of the material to be forged corresponding to each section. The volume distribution of the forged material was performed.

Thereafter, the above-mentioned forged material is roughly beaten at 1150 ° C. by a usual method using upper and lower molds made of JIS SKD61 having a thin plate-shaped engraving of a conventional type as a base material. Hitting, then deburring,
A crankshaft having four cylinders and eight counterweights shown in FIG. 4 was manufactured.

On the other hand, a crankshaft having the same four cylinders and eight counterweights as described above was manufactured by the method of the present invention described below.

First, a billet having a cross section of 95 mm × 95 mm made of JIS S45C as a material steel was subjected to the same roll forming and bending as described above to prepare a forged material.

Next, the forged material was carried into a roughing die at 1150 ° C. and roughened. In this case, the roughing die is made of JIS SKD61 as a base material, and is formed by engraving a molding shape such that the counterweight projects in a direction perpendicular to the die-casting direction at the time of forging according to the present invention.
At the top of the overhanging portion of the counterweight, burrs generated during forging are engraved with a molding shape so as to bite between the upper and lower molds, in other words, the apex of the overhanging portion of the counterweight to be formed is up and down. The center of the burr that bites out from between the molds in the thickness direction was used. By using the above-described roughing die, forging can be performed with the roughing direction perpendicular to the direction of extension of the counterweight of the crank arm (FIG. 1).
reference).

The overall shape engraved on the upper and lower dies is the same as the conventional rough hitting shape obtained by the above-described ordinary method, and is from the center axis of the crank journal to the overhanging portion apex H of the counterweight. The distance is 65 mm.

Next, the forged material to be roughly beaten was carried into a finishing die while being held in the same direction (in the direction of roughing), and was finished at 1100 ° C. In this case, the die for finishing is also made of JIS SKD61 as a base material similarly to the above-mentioned die for roughing, and the counterweight is stretched in a direction perpendicular to the die-casting direction at the time of forging according to the present invention. A counter in which the molding shape is engraved so that the burrs generated at the time of forging and the burrs generated during forging bite out between the upper and lower molds at the apex of the counterweight overhang. The one in which the apex of the overhang portion of the weight is the center in the thickness direction of the burr that bites between the upper and lower molds was used. By using the above-described die for finish driving, forging can be performed in a direction perpendicular to the direction in which the crank arm extends the counterweight, as in the case of rough driving. The overall shape engraved on the upper and lower molds is the same as the conventional finish stamping shape by the ordinary method described above.

Immediately after the above-described finishing, deburring was performed to complete the manufacture of the crankshaft.

For each of the above-mentioned conventional method and the method of the present invention, 30 crankshafts were manufactured, and their appearance was examined.

As a result, the crankshaft manufactured by forging (die stamping) using the mold according to the present invention has the same dimensional accuracy as that manufactured by the conventional method in the first embodiment.
It was also confirmed that there was no underfill in the counterweight. That is, the crankshaft manufacturing yield could be improved by 10% by the crankshaft manufacturing method of the present invention.

On the other hand, in the crankshaft manufactured by the conventional method,
Underfilling in the counterweight was observed in all 30 tubes.

[0051]

According to the crankshaft manufacturing method of the present invention, the counterweight can be filled with meat without increasing the volume of the material to be forged, so that the crankshaft manufacturing yield can be increased. Furthermore, since the burr volume can be reduced and the load on the mold is reduced, the life of the mold can be prolonged. The method for manufacturing a crankshaft of the present invention can be easily implemented by using the die for forging a crankshaft of the present invention.

[Brief description of the drawings]

FIG. 1 is a view showing a forging method using a crankshaft forging die of the present invention.

FIG. 2 is a view showing a forging method using a conventional crankshaft forging die.

FIG. 3 is a view showing a model shape of a forged crankshaft.

FIG. 4 is a diagram showing a crankshaft with four cylinders and eight counterweights manufactured in the example.

[Brief description of reference numerals]

1: Upper die 2: Lower die 3: Forged material 3a, 5a, 5b, 5c, 5d: Crank pin 3b, 6a, 6b, 6c, 6d, 6e: Crank journal 3c, 4a ', 4b', 4c ', 4d', 4e ', 4f', 4g ', 4h'
: Counter weight 3d: Burr 3e: Burr holding section 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h: Crank arm t: Thickness of counter weight h: Overhang height of counter weight H: Overhang of counter weight vertex

Claims (2)

[Claims] 1. A counterweight overhangs in a direction perpendicular to a stamping direction at the time of forging, and burrs generated at the time of forging at a vertex of the counterweight overhang portion.
A mold for forging a crankshaft, characterized in that a molded shape is engraved so as to bite out between upper and lower molds. 2. A method for manufacturing a crankshaft, wherein forging is performed with a stamping direction perpendicular to a direction in which a counterweight of a crank arm extends.