FORGING APPARATUS AND FORGING METHOD

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese patent application No. 2018-012653, filed on Jan. 29, 2018, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

The present disclosure relates to a forging apparatus and a forging method, and particularly relates to a forging apparatus and a forging method for molding an annular member having an outer peripheral surface of a diameter enlarged part where grooves are formed, an inner diameter of the diameter enlarged part being gradually enlarged toward one end.

Annular members such as gears having an outer peripheral surface of a diameter enlarged part where teeth and grooves are formed, an inner diameter of the diameter enlarged part being gradually enlarged toward one end, has been known. These annular members are often molded using a forging apparatus. For example, Japanese Unexamined Patent Application Publication No. 2007-105793 discloses a forging apparatus for molding a diameter enlarged part using a floating die.

SUMMARY

The present inventors have found the following problems regarding the forging apparatus and the forging method for molding the annular member having the outer peripheral surface of the diameter enlarged part where grooves are formed, the inner diameter of the diameter enlarged part being gradually enlarged toward one end.

In the forging apparatus and the forging method disclosed in Japanese Unexamined Patent Application Publication No. 2007-105793, after the diameter enlarged part is molded by a forging process, teeth and grooves are formed on the outer peripheral surface of the diameter enlarged part by a machining process. Therefore, there is a problem that yield and productivity of the annular member to be manufactured are low.

On the other hand, when the teeth and the grooves are concurrently molded on the outer peripheral surface of the diameter enlarged part while simply molding the diameter enlarged part by the forging process, there is a problem that stress concentrates on an end part of a protruding part provided at the die for molding the grooves, which causes the end part to be worn out, resulting in a significant reduction in the life of the die.

The present disclosure has been made in view of the aforementioned circumstances and provides a forging apparatus and a forging method with which yield and productivity of the annular member to be molded are high and a life of the die is long.

A forging apparatus according to one aspect of the present disclosure is a forging apparatus for molding an annular member having an outer peripheral surface of a diameter enlarged part where a groove is formed, an inner diameter of the diameter enlarged part being gradually enlarged toward one end, the forging apparatus including:

a fixed punch in which a tapered part for molding the diameter enlarged part is formed;

a die arranged so as to surround an outer periphery of the fixed punch; and

a movable punch that is arranged above the fixed punch so as to be opposed to the fixed punch, in which

the die is floatingly supported and includes a protruding part for molding the groove on an inner peripheral surface thereof, and

when the movable punch is lowered, an annular blank set between the fixed punch and the die is pressed, and the annular member is molded, the die is lowered along with the movable punch, and the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part.

In the forging apparatus according to one aspect of the present disclosure, the die includes the protruding part for molding the groove on the inner peripheral surface thereof, and when the movable punch is lowered, the annular blank set between the fixed punch and the die is pressed, and the annular member is molded, the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part. Therefore, yield and productivity of the annular member to be molded are high. Further, since the die is floatingly supported and is lowered along with the movable punch, the upper end of the protruding part is hard to wear out, which prolongs the life of the die. In this way, with the forging apparatus according to one aspect of the present disclosure, the annular member to be molded having high yield and productivity and a die with a long life are achieved.

A recessed part may be provided on a lower surface of the movable punch, and when the movable punch is lowered, an end part of the fixed punch may be fitted into the recessed part. According to this structure, it is possible to prevent the blank from entering the gap between the movable punch and the fixed punch and burrs from occurring.

A forging method according to one aspect of the present disclosure is a forging method for molding an annular member having an outer peripheral surface of a diameter enlarged part where a groove is formed, an inner diameter of the diameter enlarged part being gradually enlarged toward one end, the method including:

setting an annular blank between a fixed punch where a tapered part for molding the diameter enlarged part is formed and a die arranged so as to surround an outer periphery of the fixed punch; and

molding the annular member by lowering a movable punch that is arranged above the fixed punch so as to be opposed to the fixed punch and pressing the blank, in which

the die is floatingly supported and includes a protruding part for molding the groove on an inner peripheral surface thereof, and

in molding of the annular member, the die is lowered along with the movable punch, and the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part.

In the forging method according to one aspect of the present disclosure, the die includes the protruding part for molding the groove on the inner peripheral surface thereof, and when the movable punch is lowered, the annular blank set between the fixed punch and the die is pressed, and the annular member is molded, the groove is molded on the outer peripheral surface of the diameter enlarged part while molding the diameter enlarged part. Therefore, yield and productivity of the annular member to be molded are high. Further, since the die is floatingly supported and is lowered along with the movable punch, the upper end of the protruding part is hard to wear out, which prolongs the life of the die. In this way, with the forging method according to one aspect of the present disclosure, the annular member to be molded having high yield and productivity and a die with a long life are achieved.

According to the present disclosure, it is possible to provide a forging apparatus and a forging method with which yield and productivity of the annular member to be molded are high and a life of the die is long.

The above and other objects, features and advantages of the present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an annular member molded using a forging apparatus according to a first embodiment;

FIG. 2 is a cross-sectional view of the annular member molded using the forging apparatus according to the first embodiment;

FIG. 3 is a vertical cross-sectional view of the forging apparatus according to the first embodiment;

FIG. 4 is a vertical cross-sectional view of the forging apparatus according to the first embodiment;

FIG. 5 is a result of an FEM analysis indicating a plastic flow when a workpiece 40 is molded using the forging apparatus according to the first embodiment;

FIG. 6 is a vertical cross-sectional view of a forging apparatus according to a second embodiment;

FIG. 7 is a vertical cross-sectional view of the forging apparatus according to the second embodiment; and

FIG. 8 is a result of an FEM analysis indicating a plastic flow when a workpiece 40 is molded using the forging apparatus according to the second embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, with reference to the drawings, specific embodiments to which the present disclosure is applied will be explained in detail. However, the present disclosure is not limited to the following embodiments. Further, for the sake of clarity of the description, the following description and the drawings are simplified as appropriate.

First Embodiment
Structure of Molded Annular Member

With reference first to FIGS. 1 and 2, an annular member molded using a forging apparatus according to a first embodiment will be explained.

FIG. 1 is a perspective view of the annular member molded using the forging apparatus according to the first embodiment. FIG. 2 is a cross-sectional view of the annular member molded using the forging apparatus according to the first embodiment. As shown in FIGS. 1 and 2, an annular member 50 is a metallic gear including a diameter enlarged part 53 whose inner diameter is gradually enlarged toward one end and teeth 51 and grooves 52 formed on an outer peripheral surface of the diameter enlarged part 53. FIG. 2 shows, besides the annular member 50, a workpiece 40 before molding, that is, a blank. It can also be said that the annular member 50 is a workpiece 40 after molding.

As shown in FIG. 2, the diameter enlarged part 53, the teeth 51, and the grooves 52 in the annular member 50 after molding are not formed in the workpiece 40 before molding. That is, by forging the workpiece 40, which is the blank, using the forging apparatus according to the first embodiment, the diameter enlarged part 53 is molded and the teeth 51 and the grooves 52 are formed on the outer peripheral surface of the diameter enlarged part 53.

The annular member molded by using the forging apparatus according to the first embodiment is not limited to a gear and it is sufficient that the annular member include a diameter enlarged part whose inner diameter is gradually enlarged toward one end and grooves formed on the outer peripheral surface of the diameter enlarged part.

Structure of Forging Apparatus

With reference next to FIGS. 3 and 4, the forging apparatus according to the first embodiment will be explained. FIGS. 3 and 4 are vertical cross-sectional views of the forging apparatus according to the first embodiment.

As a matter of course, the right-handed xyz orthogonal coordinates shown in FIG. 3 and the other drawings are shown just for the sake of convenience for explaining the positional relation among components. Typically, the z-axis positive direction is the vertically upward direction and the xy-plane forms a horizontal plane, which is common throughout the drawings.

As shown in FIGS. 3 and 4, the forging apparatus according to the first embodiment includes a movable punch (upper punch) 10, a fixed punch (lower punch) 21, and a floating die 30. FIG. 3 shows a state before the workpiece 40 is forged, which is a state in which the movable punch 10 is raised. FIG. 4 shows a state after the workpiece 40 is forged, which is a state in which the movable punch 10 is lowered. That is, the movable punch 10 can be raised and lowered in the vertical direction (z-axis direction). The workpiece 40 after it is molded shown in FIG. 4 is the annular member 50.

As shown in FIGS. 3 and 4, the movable punch 10 is formed of a columnar inner punch 11 and a cylindrical outer punch 12 into which the inner punch 11 is fitted and inserted. The movable punch 10 is fixed to a lower surface of a pressure receiving plate 14 by a punch holder 15, which is an annular plate member. Further, in the examples shown in FIGS. 3 and 4, a disc-shaped spacer 13 is provided between the pressure receiving plate 14 and the movable punch 10.

More specifically, a recessed part having a circular shape as viewed in a planar view is provided in the central part of the lower surface of the pressure receiving plate 14, and a root part of the movable punch 10 mates with this recessed part. A flange is provided in the root part of the outer punch 12, and the punch holder 15 supports the flange from below. Then the punch holder 15 is bolted to the pressure receiving plate 14.

The movable punch 10 may not be divided into the inner punch 11 and the outer punch 12 and they may instead be integrally formed.

As shown in FIGS. 3 and 4, the fixed punch 21 is a columnar die arranged so as to be opposed to the lower side of the inner punch 11 of the movable punch 10. A tapered part 21a for molding the diameter enlarged part 53 of the annular member 50 after molding shown in FIG. 2 is formed on an upper side surface of the fixed punch 21. The fixed punch 21 is placed on a pressure receiving plate 22a. A pressure receiving plate 22b into which the fixed punch 21 is fitted and inserted is placed on the pressure receiving plate 22a, and the fixed punch 21 is fixed to the pressure receiving plate 22a. Further, a pressure receiving plate 22c is placed on the pressure receiving plate 22b.

More specifically, a cutout part is provided on an upper surface periphery of the pressure receiving plate 22a. Further, a protrusion is provided on a lower surface periphery of the pressure receiving plate 22b. The pressure receiving plate 22b is placed on the pressure receiving plate 22a in such a way that the cutout part of the pressure receiving plate 22a mates with the protrusion of the pressure receiving plate 22b. In a similar way, a cutout part is provided on an upper surface periphery of the pressure receiving plate 22b. Further, a protrusion is provided on a lower surface periphery of the pressure receiving plate 22c. The pressure receiving plate 22c is placed on the pressure receiving plate 22b in such a way that the cutout part of the pressure receiving plate 22b mates with the protrusion of the pressure receiving plate 22c.

As shown in FIGS. 3 and 4, the pressure receiving plates 22a and 22b, and 22c are accommodated in a pressure receiving plate holder 23. The pressure receiving plate holder 23 is formed of cylindrical body parts 23a and 23b, and a lid part 23c, which is an annular plate member. More specifically, the pressure receiving plates 22a and 22b are accommodated in the cylindrical body part 23a. The pressure receiving plate 22c is accommodated in the cylindrical body part 23b placed on the body part 23a. Further, the floating die 30 is also accommodated in the body part 23b. The lid part 23c is placed on the body part 23b and is fixed thereto.

As shown in FIGS. 3 and 4, a knockout ring 24, which is a cylindrical die into which the fixed punch 21 is fitted and inserted, is placed on the pressure receiving plate 22b while the workpiece 40 is being molded. The knockout ring 24 is pushed upwardly (in the z-axis positive direction) by a knockout pin 25 that penetrates through the pressure receiving plates 22a and 22b. After the workpiece 40 is molded, the knockout ring 24 is pushed upwardly, whereby the molded workpiece 40 can be taken out from the floating die 30.

As shown in FIGS. 3 and 4, the floating die 30, which is an annular die, is formed of a case 31 and insert dies 32 and 33. The floating die 30 is floatingly supported by a back-pressure pin 34 that penetrates through the pressure receiving plates 22a and 22b, and 22c. The insert dies 32 and 33, both of which have the annular shape, are fit into the annular case 31 by shrink fitting or the like. The insert die 32 arranged on the upper side of the annular case 31 and the insert die 33 arranged on the lower side thereof contact each other. The insert dies 32 and 33 may be integrally formed. Further, the case 31 and the insert dies 32 and 33 may be integrally formed.

A protruding part 33a is formed on an inner peripheral surface of the insert die 33. By this protruding part 33a, the grooves 52 can be molded on the outer peripheral surface of the annular member 50 shown in FIG. 1. Further, a recessed part that corresponds to the protruding part 33a of the insert die 33 is provided on an outer peripheral surface of the knockout ring 24, whereby the knockout ring 24 can be fitted and inserted into the insert die 33.

Operation of Forging Apparatus

Next, with reference to FIGS. 3 and 4, an operation of the forging apparatus according to the first embodiment, that is, a forging method, will be explained.

As shown in FIG. 3, in the state in which the movable punch 10 is raised, the annular workpiece 40, that is, the blank, is set between the fixed punch 21 and the floating die 30.

Next, as shown in FIG. 4, the movable punch 10 is lowered and the workpiece 40 is pressed, whereby the annular member 50 shown in FIG. 1 is molded. In this case, the inner punch 11 is inserted into the through-hole of the annular workpiece 40. Therefore, the upper inner peripheral surface of the workpiece 40 (i.e., the annular member 50) is molded by the lower outer peripheral surface of the inner punch 11. On the other hand, the outer punch 12 presses the upper surface of the workpiece 40. Therefore, the upper end surface of the workpiece 40 (i.e., the annular member 50) is molded by the lower surface of the outer punch 12. Further, the lower inner peripheral surface of the workpiece 40 (i.e., the annular member 50) is molded by the upper outer peripheral surface of the fixed punch 21.

Now, as shown in FIG. 4, a cutout part is provided on a lower surface periphery of the outer punch 12. When the movable punch 10 is lowered, this cutout part of the outer punch 12 mates with the floating die 30 and then the floating die 30 is lowered along with the movable punch 10. FIG. 4 shows a stroke S of the floating die 30. The outer peripheral surface of the workpiece 40 (i.e., the annular member 50) is molded by the inner peripheral surface of the floating die 30. At this timing, as described above, the grooves 52 of the annular member 50 shown in FIG. 1 are molded on the outer peripheral surface of the workpiece 40 by the protruding part 33a formed on the inner peripheral surface of the insert die 33 of the floating die 30. On the other hand, the lower end surface of the workpiece 40 (i.e., the annular member 50) is molded by an upper end surface of the knockout ring 24.

Now, a result of a Finite Element Method (FEM) analysis of a plastic flow in the case in which the workpiece 40 is molded using the forging apparatus according to the first embodiment will be explained. FIG. 5 is a result of the FEM analysis showing the plastic flow in the case in which the workpiece 40 is molded using the forging apparatus according to the first embodiment. FIG. 5 shows cross-sectional shapes of the workpiece 40 when the molding is started, during the molding, and when the molding is completed. The three diagrams shown in FIG. 5 correspond to an enlarged view of an area V surrounded by the dashed line in FIG. 4.

As shown by the outline arrows in FIG. 5, when the movable punch 10 (the inner punch 11 and the outer punch 12) is lowered and the workpiece 40 is pressed, the workpiece 40 is pushed toward the knockout ring 24 between the fixed punch 21 and the insert dies 32 and 33 of the floating die 30. In this case, the diameter of the workpiece 40 is enlarged by the tapered part 21a of the fixed punch 21. Therefore, as shown by the black arrows in FIG. 5, the workpiece 40 is subjected to plastic flow in the x-axis positive direction, that is, toward the insert die 33. Therefore, the grooves 52 of the annular member 50 shown in FIG. 1 are molded on the outer peripheral surface of the workpiece 40 by the protruding part 33a formed on the inner peripheral surface of the insert die 33. The tooth 51 is molded between the grooves 52.

As described above, by using the forging apparatus according to the first embodiment, the grooves 52 can be molded on the outer peripheral surface of the diameter enlarged part 53 while molding the diameter enlarged part 53 (see FIG. 2) of the annular member 50 shown in FIG. 1. Therefore, with the forging apparatus according to the first embodiment, the annular member 50 to be molded having high yield and productivity is achieved.

Further, the insert die 33 is floatingly supported and is lowered along with the movable punch 10, that is, the workpiece 40. Therefore, it is hard for the upper end of the protruding part 33a of the insert die 33 to wear out, which prolongs the life of the insert die 33.

Accordingly, with the forging apparatus according to the first embodiment, the annular member to be molded having high yield and productivity and a die with a long life are achieved.

Second Embodiment

With reference next to FIGS. 6 and 7, a structure and an operation of a forging apparatus according to a second embodiment will be explained. FIGS. 6 and 7 are vertical cross-sectional views of the forging apparatus according to the second embodiment.

As shown in FIG. 5, in the forging apparatus according to the first embodiment, when the molding is completed, the workpiece 40 may enter the gap between the inner punch 11 of the movable punch 10 and the fixed punch 21 and a burr 40a may occur.

On the other hand, as shown in FIGS. 6 and 7, in the forging apparatus according to the second embodiment, a recessed part 11a having a circular shape as viewed in a plane view into which the end part of the fixed punch 21 is fitted is provided on the lower surface of the inner punch 11 of the movable punch 10. Further, the height of the end part of the fixed punch 21 of the forging apparatus according to the second embodiment is larger than the height of the end part of the fixed punch 21 of the forging apparatus according to the first embodiment by the depth of the recessed part 11a.

As shown in FIG. 7, when the movable punch 10 is lowered, the end part of the fixed punch 21 is fit into the recessed part 11a of the inner punch 11.

Now, a result of an FEM analysis of a plastic flow in a case in which the workpiece 40 is molded using the forging apparatus according to the second embodiment will be explained. FIG. 8 is a result of the FEM analysis showing the plastic flow when the workpiece 40 is molded using the forging apparatus according to the second embodiment. FIG. 8 shows cross-sectional shapes of the workpiece 40 when the molding is started, during the molding, and the molding is completed. The three diagrams shown in FIG. 8 correspond to an enlarged view of an area VIII surrounded by the dashed line in FIG. 7.

As shown by the outline arrows in FIG. 8, when the movable punch 10 (the inner punch 11 and the outer punch 12) is lowered and the workpiece 40 is pressed, the workpiece 40 is pushed toward the knockout ring 24. In this case, the diameter of the workpiece 40 is enlarged by the tapered part 21a of the fixed punch 21. Therefore, as shown by the black arrows, the workpiece 40 is subjected to plastic flow in the x-axis positive direction, that is, toward the insert die 33. Therefore, the grooves 52 of the annular member 50 shown in FIG. 1 are molded on the outer peripheral surface of the workpiece 40 by the protruding part 33a formed on the inner peripheral surface of the insert die 33. The tooth 51 is molded between the grooves 52.

As described above, by using the forging apparatus according to the second embodiment, the grooves 52 can be molded on the outer peripheral surface of the diameter enlarged part 53 while molding the diameter enlarged part 53 (see FIG. 2) of the annular member 50 shown in FIG. 1. Therefore, with the forging apparatus according to the second embodiment, the annular member 50 to be molded having high yield and productivity is achieved, like in the forging apparatus according to the first embodiment.

Further, the insert die 33 is floatingly supported, and is lowered along with the movable punch 10, that is, the workpiece 40. Therefore, the upper end of the protruding part 33a of the insert die 33 is hard to wear out, which prolongs the life of the insert die 33. That is, with the forging apparatus according to the second embodiment, a die with a long life is achieved, like in the forging apparatus according to the first embodiment.

Therefore, with the forging apparatus according to the second embodiment as well, the annular member to be molded having high yield and productivity and a die with a long life are achieved.

Further, in the forging apparatus according to the second embodiment, when the movable punch 10 is lowered, the end part of the fixed punch 21 is fitted into the recessed part 11a of the inner punch 11. Therefore, when the molding is completed, a gap is not generated between the inner punch 11 of the movable punch 10 and the fixed punch 21. It is therefore possible to prevent the workpiece 40 from entering the gap between the inner punch 11 and the fixed punch 21 and the burr 40a (see FIG. 5) from occurring.

Since the other structures and the operations are similar to those of the forging apparatus according to the first embodiment, the descriptions thereof will be omitted.

From the disclosure thus described, it will be obvious that the embodiments of the disclosure may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.

FORGING APPARATUS AND FORGING METHOD

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