Press-work method and bottomed container

A press mold includes an inner punch (23), an intermediate punch (24) disposed along an outer periphery of the inner punch (23) and having an intermediate punch inclined portion (24a) at a leading end, an outer punch (25) disposed along an outer periphery of the intermediate punch (24), and a die (27) having a die inclined portion (27a) facing the intermediate punch inclined portion (24a), central axes (20) of all of which are coaxially disposed. While a bottom portion of a bottomed container (22) is constrained by the inner punch (23) and the die (27), an end portion of the bottomed container (22) is pressed by the outer punch (25), and the intermediate punch (24) is moved in a direction opposite a direction in which the outer punch (25) is pressed, whereby a bottomed container inclined portion (22a) of the bottomed container (22) sandwiched by the intermediate punch inclined portion (24a) and the die inclined portion (27a) is thickened.

TECHNICAL FIELD

The present invention relates to a press-work method of thickening an inclined portion rising from a bottom surface portion of a bottomed container, and to a bottomed container manufactured by the same.

BACKGROUND ART

With reference toFIG. 1AandFIG. 1B, as a method of thickening a vertical wall of a bottomed container, a method in which a disk-shaped workpiece is formed into a bottomed container11by deep drawing, and an end surface11bof the bottomed container is pushed by a pushing punch14while a bottomed container bottom surface11ais sandwiched by a die12and a pressing punch13, to thereby thicken a vertical wall11cof the bottomed container has been conventionally in general use. In this method, however, being constrained only weakly, the vertical wall portion of the bottomed container buckles during the thickening, so that folding11doccurs. This has made it difficult to realize a large thickening ratio (sheet thickness after the thickening/original sheet thickness) exceeding 1.3.

For example, Patent Literature 1 discloses a thickening press-work method in which a pressing punch and an upsetting punch are provided, and between an upper end portion and a bottom inner portion of a workpiece, a gap is reserved between the pressing punch and a die, and an upper surface of the end portion of the workpiece is pressed by the upsetting punch. However, in the method of Patent Literature 1, folding may also occur because buckling occurs in the gap during the thickening.

Therefore, there has been proposed a method to overcome the drawbacks of the above-described thickening methods, in the manufacture of a pulley piston for continuously variable transmission of an automobile, as described in Non Patent Literature 1. This forming method is capable of preventing folding ascribable to buckling because a portion to be thickened is thickened by pushing an end portion of a cup in a state where a constraint surface of a material is increased by providing a corner portion in the portion to be thickened. However, since a gap of the portion to be thickened is geometrically decided by constraint by the shape of a mold and the movement of the mold, a maximum thickening ratio that can be achieved in one forming is about 1.5. Further, before this process, it is necessary to form a bottomed cylindrical container by deep drawing or the like, and totally two processes are required.

Further, Patent Literature 2 proposes a method in which a press-worked workpiece which has an end wall, a bent portion bent from an outer periphery of the end wall toward one side, and a cylindrical portion provided to continue from the bent portion is used, the workpiece is clamped by a clamp punch adapted to an inner surface of the workpiece, a clamp die adapted to an outer surface of the end wall, and a thickness-increase guide die fitted to an outer peripheral surface of the clamp die so as to be swingable in an axial direction and adapted to outer peripheral surfaces of the bent portion and the cylindrical portion, a thickness-increasing punch is inserted in space formed between the clamp punch and the thickness-increase guide die to apply an axial-direction compression load to the cylindrical portion, thereby thickening the bent portion, and the thickness-increase guide die is retracted from the clamp die according to the thickening.

Further, Patent Literature 3 proposes a structure in which a knockout for receiving a body portion of a workpiece, a plate presser for pressing an area up to the middle of a rising portion rising obliquely outward from the body portion, a thickness-increasing punch for pressing a tip of the rising portion, and a die for receiving the rising portion are provided, and the die is movable in an axial direction relatively to the knockout and the thickness-increasing punch. In the process of crushing the rising portion by pressing the tip of the rising portion by the thickness-increasing punch, the die is pressed by the rising portion which is in the course of being thickened without being pushed by the thickness-increasing punch, to move relatively to the knockout, so that a gap between the plate presser and the die which sandwich the rising portion widens.

However, the methods of Patent Literatures 2, 3 also require the forming of a bottomed cylindrical container by deep drawing or the like, and thus require totally two processes. Further, a cutting process is sometimes required because a large step occurs in a boundary between a thickened portion and a non-thickened portion. Further, an achievable thickening ratio is not mentioned.

Further, in the structure in which the die is divided and part thereof is moved, in Patent Literature 2, for example, a force in a direction perpendicular to an inclined portion (2bin Patent Literature 2) acts on the thickness-increase guide die at the time of the thickening. Since this force acts in such a direction as to make the thickness-increase guide die separate from the clamp die (outward in a diameter direction), a gap occurs in a boundary between the clamp die and the thickness-increase guide die, which may cause a burr.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The present invention was made in order to solve the above-described conventional drawbacks and its main object is to make it possible to avoid folding due to buckling to achieve thickening with a thickening ratio of 1.5 times or more in a press-work. Its another object is to make it possible to manufacture a bottomed container having a smooth shape without a large step in a boundary between a thickened portion and a non-thickened portion. Its another object is to make it possible to manufacture a bottomed container whose inclined portion is thickened, from a disk-shaped workpiece by a press-work having one process.

Solution to Problem

The gist of the present invention that is to achieve the aforesaid objects is as follows.

[1] A press-work method using a press mold which includes an inner punch, an intermediate punch disposed along an outer periphery of the inner punch and having an intermediate punch inclined portion at a leading end, an outer punch disposed along an outer periphery of the intermediate punch, and a die having a die inclined portion facing the intermediate punch inclined portion, central axes of all of which are disposed coaxially, the method including a thickening step of, while constraining a bottom portion of a bottomed container by the inner punch and the die, pressing an end portion of the bottomed container by the outer punch and moving the intermediate punch in a direction opposite a direction in which the outer punch is pressed, to thereby thicken a bottomed container inclined portion of the bottomed container sandwiched by the intermediate punch inclined portion and the die inclined portion.

[2] A press-work method using a press mold which includes an inner punch having an inner punch flat portion and an inner punch inclined portion at a leading end, an intermediate punch disposed along an outer periphery of the inner punch and having an intermediate punch inclined portion at a leading end, an outer punch disposed along an outer periphery of the intermediate punch, and a die having a die inclined portion disposed to face the intermediate punch inclined portion, central axes of all of which are disposed coaxially, the inner punch inclined portion being formed at an end portion, of the leading end of the inner punch, on a side adjacent to the intermediate punch inclined portion, the method including:

an outer punch pressing step of, while constraining a bottom portion of a bottomed container by the inner punch flat portion and the die, pressing an end portion of the bottomed container by the outer punch to thereby bring a bottomed container inclined portion, of the bottomed container, which extends along the inner punch inclined portion and the intermediate punch inclined portion, into contact with the die inclined portion;

an intermediate punch pressing step of pressing the intermediate punch in a direction of the die against the bottomed container which is brought into contact with the die inclined portion in the outer punch pressing step, to bring the intermediate punch inclined portion into contact with the bottomed container inclined portion; and

a thickening step of pressing the outer punch against the bottomed container which is brought into contact with the intermediate punch inclined portion in the intermediate punch pressing step, and moving the intermediate punch in a direction opposite a direction in which the outer punch is pressed, to thereby thicken the bottomed container inclined portion.

[3] The press-work method according to [1], including, before the thickening step, a forming step of pressing a disk-shaped workpiece into the die by the inner punch and the intermediate punch to form the bottomed container in which the bottomed container inclined portion is formed at a position sandwiched by the intermediate punch inclined portion and the die inclined portion.

[4] The press-work method according to [2], including, before the outer punch pressing step, a forming step of pressing a disk-shaped workpiece into the die by the inner punch and the intermediate punch to form the bottomed container in which the bottomed container inclined portion is formed at a position sandwiched by the inner punch inclined portion and the intermediate punch inclined portion, and the die inclined portion.

[5] The bottomed container manufactured by the press-work method according to [1], wherein a thickening ratio of a thickness of the bottomed container inclined portion is 1.5 times or more.

[6] The bottomed container manufactured by the press-work method according to [2], wherein a thickening ratio of a thickness of the bottomed container inclined portion is 1.5 times or more.

Advantageous Effects of Invention

According to the present invention, it is possible to avoid folding due to buckling to achieve thickening with a thickening ratio of 1.5 times or more.

Further, it is possible to manufacture a bottomed container having a smooth shape without a large step in a boundary between a thickened portion and a non-thickened portion.

Furthermore, it is possible to manufacture a bottomed container whose inclined portion is thickened, from a disk-shaped workpiece by a press-work having one process.

DESCRIPTION OF EMBODIMENTS

Hereinafter, modes for carrying out the present invention will be described with reference to the attached drawings.

As a result of studious studies, the present inventor has found out that, by performing deep drawing by using an inner punch, an intermediate punch disposed along an outer periphery of the inner punch, and a die, central axes of all of which are coaxially disposed, to form a bottomed container, and subsequently, while constraining a workpiece, performing thickening by gradually increasing a gap between the intermediate punch and the die when an end surface of the bottomed container is pressed by the outer punch, it is possible to perform the thickening with a thickening ratio of 1.5 times or more by a press-work having one process while avoiding folding due to buckling.

FIG. 2is a cross-sectional view illustrating a state before deep drawing is executed. As illustrated inFIG. 2, a press mold includes an inner punch23, an intermediate punch24disposed along an outer periphery of the inner punch23, an outer punch25disposed along an outer periphery of the intermediate punch24, a knockout26, and a die27disposed along an outer periphery of the knockout26, central axes of all of which are coaxially disposed. The inner punch23is disposed to face the knockout26and the die27, and the intermediate punch24and the outer punch25are disposed to face the die27.

The inner punch23has a columnar shape, and is of a movable type capable of moving up and down by a not-illustrated drive source of a mechanical type (hydraulic or servo motor, or the like).

The intermediate punch24has a cylindrical shape, and on its surface that comes into contact with a portion to be thickened of a workpiece (that is, on a lower end portion (leading end) of the intermediate punch24), an intermediate punch inclined portion24ais formed. This intermediate punch inclined portion24ais inclined in an obliquely upward direction from an inner punch23side toward an outer punch25side. The intermediate punch24is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

The outer punch25has a cylindrical shape and is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

The knockout26has a columnar shape, is intended to detach a formed product from the mold, and is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

The die27is of a fixed type, has a substantially concave shape, and has, at a center portion, a hole allowing the knockout26to be inserted therein. Further, in the die27, a die inclined portion27ais formed, and this die inclined portion27ais disposed to face the intermediate punch inclined portion24a.

In this embodiment, by executing the following forming step and thickening step, the workpiece21was press-worked. As the workpiece21, a disk-shaped high-tensile steel sheet (SAPH590) having a 240 mm outside diameter and a 4 mm sheet thickness was used.

The workpiece21is placed on the die27and is subjected to the deep drawing by pressing the inner punch23and the intermediate punch24, whereby a bottomed container22in which a bottomed container inclined portion22ais formed at a position sandwiched by the intermediate punch inclined portion24aand the die inclined portion27ais formed as illustrated inFIG. 3(forming step).

In the state illustrated inFIG. 3, a bottom portion of the bottomed container22is constrained by the inner punch23and the die27.

Subsequently, as illustrated inFIG. 4andFIG. 5, an end surface of the bottomed container22formed in the forming step is pressed by the outer punch25, and the intermediate punch24is moved upward. Consequently, a gap between the intermediate punch inclined portion24aand the die inclined portion27agradually becomes larger, which makes it possible to perform the thickening while suppressing buckling by sandwiching the bottomed container inclined portion22aby the intermediate punch inclined portion24aand the die inclined portion27a(thickening step). The cross-sectional views inFIG. 4andFIG. 5illustrate states in the middle of the thickening and after the thickening respectively.

After the thickening step, the inner punch23, the intermediate punch24, the outer punch25, and the knockout26are moved upward, and the bottomed container22is detached from the die27. A sheet thickness of the bottomed container inclined portion22ais 6.9 mm, and thus the thickness can be increased to 1.73 times an original sheet thickness of 4 mm without any occurrence of folding due to buckling.

Further, at the time of the thickening, a force in a direction perpendicular to the intermediate punch inclined portion24aacts on the intermediate punch24, but since this force acts in such a direction as to press the intermediate punch24against the inner punch23(inward in a diameter direction (center direction)), there occurs no gap in a boundary between the inner punch23and the intermediate punch24and a burr is not generated.

In a second embodiment, a bottomed container having a smooth shape without a large step in a boundary between a thickened portion and a non-thickened portion is manufactured.

FIG. 6is a cross-sectional view illustrating a state before deep drawing is executed. As illustrated inFIG. 6, a press mold includes an inner punch33, an intermediate punch34disposed along an outer periphery of the inner punch33, an outer punch35disposed along an outer periphery of the intermediate punch34, a knockout36, and a die37disposed along an outer periphery of the knockout36, central axes30of all of which are coaxially disposed. The inner punch33is disposed to face the knockout36and the die37, and the intermediate punch34and the outer punch35are disposed to face the die37.

The inner punch33has a columnar shape, and on its leading end, an inner punch inclined portion33aand an inner punch flat portion33bare formed. The inner punch inclined portion33ais formed on a peripheral edge portion of the leading end, that is, on an end portion on a side adjacent to an intermediate punch inclined portion34a, and the inner punch flat portion33bis formed around the central axis30. The inner punch inclined portion33ais inclined in an obliquely upward direction from a central axis30side toward an intermediate punch34side. The inner punch flat portion33bextends in a horizontal direction perpendicular to the central axis30. The inner punch33is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

The intermediate punch34has a cylindrical shape, and on its surface that comes into contact with a portion to be thickened of a workpiece (that is, on a lower end portion (leading end) of the intermediate punch34), the intermediate punch inclined portion34ais formed. This intermediate punch inclined portion34ais inclined in an obliquely upward direction from an inner punch33side toward an outer punch35side. The intermediate punch34is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

Here, when a height of an end portion of the inner punch inclined portion33aon a side more distant from the central axis30and a height of an end portion of the intermediate punch inclined portion34aon a side closer to the central axis30are equal, that is, in the state illustrate inFIG. 6, the inner punch inclined portion33aand the intermediate punch inclined portion34aform a smooth curve.

The outer punch35has a cylindrical shape and is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

The knockout36has a columnar shape, is intended to detach a formed product from the mold, and is of a movable type capable of moving up and down by a not-illustrated mechanical drive source.

The die37is of a fixed type, has a substantially concave shape, and has, at a center portion, a hole allowing the knockout36to be inserted therein. In the die37, a die inclined portion37ais formed, and this die inclined portion37ais disposed to face the inner punch inclined portion33aand the intermediate punch inclined portion34a.

In this embodiment, by executing the following forming step, outer punch pressing step, intermediate punch pressing step, and thickening step, the workpiece31was press-worked. As the workpiece31, a disk-shaped high-tensile steel sheet (SAPH590) having a224outside diameter and a 4 mm sheet thickness was used.

The workpiece31is placed on the die37, and is subjected to the deep drawing by pressing the inner punch33and the intermediate punch34, whereby a bottomed container32in which a bottomed container inclined portion32ais formed at a position sandwiched by the inner punch inclined portion33aand the intermediate punch inclined portion34a, and the die inclined portion37ais formed as illustrated inFIG. 7(forming step).

In the state illustrated inFIG. 7, a bottom portion of the bottomed container32is constrained by the inner punch flat portion33bof the inner punch33and the die37.

Subsequently, an end surface of the bottomed container32formed in the forming step is pressed by the outer punch35, whereby the bottomed container inclined portion32aextending along the inner punch inclined portion33aand the intermediate punch inclined portion34ais brought into contact with the die inclined portion37aas illustrated inFIG. 8(outer punch pressing step).

Subsequently, the intermediate punch34is moved downward toward the bottomed container32which is brought into contact with the die37in the outer punch pressing step (the intermediate punch34is pressed toward the die37), whereby the intermediate punch inclined portion34ais brought into contact with the bottomed container inclined portion32aas illustrated inFIG. 9(intermediate punch pressing step).

Subsequently, as illustrated inFIG. 10andFIG. 11, an end surface of the bottomed container32is pressed by the outer punch35, and the intermediate punch34is moved upward. Consequently, a gap between the intermediate punch inclined portion34aand the die inclined portion37agradually becomes larger, which makes it possible to perform the thickening while suppressing buckling by sandwiching the bottomed container inclined portion32aby the intermediate punch inclined portion34aand the die inclined portion37a(thickening step). The cross-sectional views inFIG. 10andFIG. 11illustrate states in the middle of the thickening and after the thickening respectively.

After the thickening step, the inner punch33, the intermediate punch34, the outer punch35, and the knockout36are moved upward, and the bottomed container32is detached from the die37. A sheet thickness of the bottomed container inclined portion32ais 8 mm, and thus the thickness can be increased to twice an original sheet thickness of 4 mm without any occurrence of folding due to buckling. Further, a smooth shape is achieved without any large step in a boundary between a thickened portion and a non-thickened portion.

Further, at the time of the thickening, a force in a direction perpendicular to the intermediate punch inclined portion34aacts on the intermediate punch34, but since this force acts in such a direction as to press the intermediate punch34against the inner punch33(inward in a diameter direction (center direction)), there occurs no gap in a boundary between the inner punch33and the intermediate punch34and a burr is not generated.

Here, in the state illustrated inFIG. 7, if the end portion of the bottomed container32is pressed by the outer punch35without the intermediate punch34abutting on the bottomed container32, the bottomed container inclined portion32ais not sufficiently constrained, and accordingly, buckling occurs in the bottomed container inclined portion32aas illustrated inFIG. 12. Therefore, by executing the thickening process by the outer punch35while constraining the bottomed container inclined portion32aby sandwiching it by the intermediate punch34and the die37, it is possible to suppress the buckling in the bottomed container inclined portion32a.

In the above-described examples, an angle made by the bottomed container inclined portions22a,32aand the horizontal direction is 45°, but it is desirably not less than 20° nor more than 70°. This is because, if the angle made by the bottomed container inclined portion22a,32aand the horizontal direction is less than 20°, a flow of a material from bottomed container vertical wall portions22b,32bto the bottomed container inclined portions22a,32abecomes worse, and a load required for the forming becomes large. Further, this is because, if the angle made by the bottomed container inclined portions22a,32aand the horizontal direction is over 70°, a contact length of the workpieces21,31and the mold becomes long, and accordingly a frictional force becomes large, so that a load required for the forming becomes large. Note that the bottomed container vertical wall portions22b,32bmean portions of the bottomed containers22,32on a side closer to the outer punches25,35than the bottomed container inclined portions22a,32a.

Hitherto, the present invention has been described together with various embodiments, but the present invention is not limited only to these embodiments, and changes and so on can be made within the scope of the present invention.

In the above-described examples, SAPH590 is used as the workpiece, but it is not limited to an iron-based material, but an aluminum-based metal, a titanium-based metal, or the like is usable.

Further, in the above-described embodiments, the examples where the bottomed container whose inclined portion is thickened is manufactured from the disk-shaped workpiece by the press-work having one process, but the present invention is also applicable to a press-work whose thickening target is a bottomed container having an inclined portion which is formed in a separate process, that is, to a press-work whose starting state isFIG. 3orFIG. 7.

INDUSTRIAL APPLICABILITY

The present invention is usable for thickening an inclined portion rising from a bottom surface portion of a bottomed container.