Press drawing method

Abstract

To provide a press drawing method for manufacturing a molding including a swollen part that is a part having a swollen shape which effectively reduces reduction in a shoulder curve part.SOLUTION: A press drawing method includes: a first step of manufacturing a first molding that is a molding including a swollen part that is a part having a swollen shape by pressing a plate material that is a plate-like base material in a first direction by a first die; and a second step of manufacturing a second molding by pressing at least a part of a shoulder curve part in a second direction by a second die while restraining a shape of a central part of the swollen part of the first molding. The shoulder curve part is a part from a ridge line to a side face of the swollen part, the second direction is a direction toward the inside of the swollen part rather than the first direction, and the second molding is a molding having a shoulder curve part having a shape closer to a target shape than the shape of the shoulder curve part of the first molding.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a press drawing method. Specifically, the present invention relates to a press drawing method capable of effectively reducing the material removal in the shoulder curved surface portion of a molded body including a bulging portion which is a portion having a bulging shape.

Background Art

[0002] In the relevant technical field, molded bodies including a bulging portion which is a portion having a ridgeline portion and a large drawing height and a bulging shape (such as a mountain shape and a hat shape) are used for various applications. Since it may be difficult to produce such a molded body from a plate-like member by a single press drawing process, it is known to produce it by multiple press drawing processes. For example, a preliminary molded body 1 having a bulging portion slightly larger than the target shape as shown in FIG. 5(a) is prepared in advance. Such a preliminary molded body 1 can be produced, for example, by a press drawing process using a mold (an overdraw mold) (not shown) having an internal space corresponding to a shape slightly larger than the target shape.

[0003] Next, the preliminary molded body 1 is press drawn using a mold 2 having an internal space corresponding to the target shape as indicated by the black arrow to produce a target molded body 3 having the target shape as shown in FIG. 5(b). Note that FIG. 5(a) shows the shape of the preliminary molded body 1 in an easy-to-understand manner, represents the mold 2 by the wall surface (molding surface) defining the internal space of the mold 2, and omits a part of the molding surface so that the portion of the preliminary molded body 1 located inside the mold 2 can be seen.

[0004] FIG. 6 is a schematic diagram illustrating changes in the position of a mold and the shape of a workpiece (formed object) in a press drawing process (conventional method) according to the prior art illustrated in FIG. 5. As indicated by the solid black arrows in FIG. 6, in a press drawing process using a general press machine, a target formed object 3 having a target shape is formed by pressing a preform 1 downward in the vertical direction with a mold 2 (upper mold). At this time, a bulging portion R1 that bulges slightly larger than the target shape of the preform 1 is pressed by the mold 2 and formed into the target shape (e.g., a seating surface, etc.).

[0005] However, in the press drawing method according to the prior art as described above (hereinafter sometimes referred to as the "conventional method"), there is a risk of problems such as a reduction in plate thickness or cracking occurring in a shoulder curved surface portion R2 (a portion extending from the vicinity of a ridge line to the side surface) located at the end of the bulging portion R1 compared to other portions. Such problems occur because the shoulder curved surface portion R2, where the plate thickness has already decreased (thinning) during the forming of the preform 1, is rubbed (scraped off) downward by the mold 2 (upper mold) coming down from above as indicated by the arrow in FIG. 7, resulting in a further reduction in plate thickness (thinning) in the shoulder curved surface portion R2.

[0006] Therefore, in this technical field, various techniques have been proposed to effectively reduce thinning in the shoulder curved surface portion in a press drawing method for a formed object having a bulging shape.

[0007] For example, in a process of obtaining a cylindrical drawn formed object having a flat plate portion and a cylindrical drawn portion that bulges from the flat plate portion and has a circular top, a method has been proposed in which unevenness is formed on the top surface of the cylindrical drawn portion, and in the next drawing process, the portion is thickened using a mold having a circumference shorter than the circumference of the workpiece (formed object) (see, for example, Patent Document 1). According to this, it is said that it is possible to minimize the outflow of material in the thinning portion and form a cylindrical drawn formed object with a thickening of 25% or more in the thickening portion.

[0008] However, in the above method, a special mold for forming unevenness on the top surface of the cylindrical drawing part is required, so the shape of the applicable molded body is limited and the manufacturing cost increases. In addition, since it is not a method for reducing the thinning of only the shoulder curved surface part, it is impossible and / or wasteful to reduce the thinning of the shoulder curved surface part by the above method.

[0009] In addition, there has also been proposed a method in which, with the entire workpiece clamped by a clamp punch, a clamp die, and a bulking die, an axial compressive load is applied to the cylindrical portion of the workpiece by a bulking punch to thicken the bent portion of the workpiece, and the bulking guide die is retracted with respect to the clamp die according to the thickening to guide the flow of thickening of the bent portion along the inner peripheral surface of the bulking guide die (see, for example, Patent Document 2). According to this, it is said that the shoulder curved surface part can be thickened while preventing the occurrence of wrinkles.

[0010] However, in the above method, an inner and outer overall mold is required to push the lower end portion of the cylindrical drawing part into the mold. Also in this case, a mold having a complicated shape is required, leading to an increase in manufacturing cost. In addition, since it is not a method for reducing the thinning of only the shoulder curved surface part, it is impossible and / or wasteful to reduce the thinning of the shoulder curved surface part by the above method.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] As described above, in the relevant technical field, there is a continuous demand for a technology that can effectively reduce the material removal on the shoulder curved surface portion in the press drawing process for manufacturing a molded body including a bulging portion that is a portion having a bulging shape.

Means for Solving the Problem

[0013] In view of the above problems, as a result of intensive research, the inventor has found that in the process of manufacturing a target molded body from a preform as described above, instead of pressing the shoulder curved surface portion of the preform in the same direction as when the preform is molded, by pressing it in the direction toward the inside of the bulging portion, further material removal on the shoulder curved surface portion can be reduced.

[0014] Specifically, the press drawing process method according to the present invention (hereinafter may be referred to as "the method of the present invention") is a press drawing process method for manufacturing a molded body including a bulging portion that is a portion having a bulging shape, and is characterized by including the first step and the second step listed below.

[0015] First step: A step of manufacturing a first molded body, which is a molded body including a bulging portion that is a portion having a bulging shape, by pressing a plate material, which is a plate-shaped base material, in a first direction by a first mold. Second step: A step of manufacturing a second molded body by pressing at least a part of the shoulder curved surface portion in a second direction by a second mold while restraining the shape of the central portion of the bulging portion of the first molded body. Note that the shoulder curved surface portion is a portion extending from the ridge line of the bulging portion to the side surface, the second direction is a direction toward the inside of the bulging portion rather than the first direction, and the second molded body is a molded body having a shoulder curved surface portion closer to the target shape than the shape of the shoulder curved surface portion of the first molded body.

[0016] The method of the present invention can further include the following third step. Third step: A step of manufacturing a third molded body, which is a molded body having a target shape, by pressing at least a part of the second molded body by a third mold.

Effect of the Invention

[0017] As described above, in the method of the present invention, the shoulder curved surface portion of the bulging portion included in the first molded body (corresponding to the preformed body described above) formed in the first step is pressed in the second step in a direction (second direction) toward the inside of the bulging portion rather than in the pressing direction (first direction) in the first step. Therefore, further thinning of the shoulder curved surface portion as occurs in the conventional method described above is effectively reduced. That is, according to the method of the present invention, in the press drawing process for producing a molded body including a bulging portion which is a portion having a bulging shape, thinning of the shoulder curved surface portion can be effectively reduced.

[0018] Other objects, other features and attendant advantages of the present invention will be readily understood from the description of each embodiment of the present invention described with reference to the following drawings.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0020] 《First Embodiment》 Hereinafter, a press drawing method according to the first embodiment of the present invention (hereinafter, may be referred to as the "first method") will be described with reference to the drawings.

[0021] 〈Configuration〉 FIG. 1 is a flowchart illustrating the flow of each step included in the first method. The first method is a press drawing method characterized by including the first step (step S10) and the second step (step S20) listed below.

[0022] First step (step S10): A step of producing a first formed body, which is a formed body including a bulging portion that is a portion having a bulging shape, by pressing a plate material, which is a plate-shaped base material, in a first direction by a first mold. Second step (step S20): A step of producing a second formed body by pressing at least a part of the shoulder curved surface portion in a second direction by a second mold while restraining the shape of the central portion of the bulging portion of the first formed body. Note that the shoulder curved surface portion is a portion extending from the ridge line of the bulging portion to the side surface, the second direction is a direction toward the inside of the bulging portion rather than the first direction, and the second formed body is a formed body having a shoulder curved surface portion closer to the target shape than the shape of the shoulder curved surface portion of the first formed body.

[0023] The first step (step S10) can be executed using a press machine such as a hydraulic press machine or a mechanical press machine. Since the configuration and operation of such a press machine are well known to those skilled in the art, the description here is omitted.

[0024] The above-mentioned "plate material" is a member composed of a material that can be plastically deformed by press drawing and has a plate-like shape. Specific examples of such materials include, for example, metal materials such as iron, copper, and aluminum, and alloy materials containing any of these metals. Typical examples of the above-mentioned plate material include, for example, stainless steel plates. Alternatively, the plate material may be a non-metallic material as long as it can be plastically deformed by press drawing.

[0025] The "first mold" is a mold having an internal space corresponding to the shape of a formed body (corresponding to the aforementioned "preformed body") having a bulging portion slightly larger than the shape of the final formed body (which may be hereinafter referred to as the "target shape") to be produced by the first method. Such a mold may be referred to as an "overdraw mold". Therefore, the "first formed body" produced in the first step is a formed body corresponding to the aforementioned preformed body and has a bulging portion slightly larger than the target shape.

[0026] The "first direction" is the direction in which the first mold presses the plate material in the first step, and in press drawing using a press machine, it is generally the downward direction in the vertical direction.

[0027] The second step (step S20) can also be executed in the same manner as the above-mentioned first step. However, in the second step, while restraining the shape of the central portion of the bulging portion of the first formed body produced in the first step, at least a part of the shoulder curved surface portion is pressed in the second direction by the second mold, thereby producing the second formed body.

[0028] As described above, the "shoulder curved surface portion" is the portion extending from the ridge line of the bulging portion to the side surface. The "ridge line" mentioned here means the boundary between the top surface and the side surface of the bulging portion, but it is not necessarily required that there is a clear boundary between the top surface and the side surface of the bulging portion. That is, the ridge line in this specification means a protruding portion located near the boundary between the top surface and the side surface of the bulging portion. Therefore, the shoulder curved surface portion means a curved surface located in the portion extending from near the boundary between the top surface and the side surface of the bulging portion to the side surface.

[0029] In the first step, by pressing the plate material in the first direction with the first mold, a first molded body, which is a molded body including a bulging portion, is produced. At this time, the plate thickness of the shoulder curved surface portion decreases (thinning) with the formation of the bulging portion. Therefore, if the shoulder curved surface portion of the first molded body is pressed in the same first direction as in the first step also in the second step in the same manner as the conventional method, the shoulder curved surface portion will be rubbed (scraped off) in the first direction by the mold. That is, the plate thickness further decreases (thinning) in the shoulder curved surface portion.

[0030] However, in the second step included in the first method, as described above, at least a part of the shoulder curved surface portion is pressed by the second mold in the second direction, which is the direction toward the inside of the bulging portion rather than the first direction. Therefore, the shoulder curved surface portion is not rubbed in the same direction as the pressing direction (the first direction) in the first step as in the conventional method, but is pressed in the direction toward the inside of the bulging portion rather than the first direction. As a result, compared with the conventional method, the ratio of the material flowing in the first direction among the materials forming the shoulder curved surface portion is reduced, and the ratio of the material remaining in the shoulder curved surface portion or flowing to the side opposite to the first direction of the shoulder curved surface portion increases. That is, further thinning in the shoulder curved surface portion of the second molded body is efficiently reduced.

[0031] Still, as described above, the second direction is a direction toward the inside of the bulging portion from the first direction. For example, when the first direction is the downward direction in the vertical direction, the second direction is a direction having a component toward the center of the bulging portion in the horizontal direction (for example, a direction slanting downward). The specific angle of the second direction can be appropriately set based on various factors such as the shape and thickness of the shoulder curved surface portion pressed by the second mold, the target shape of the shoulder curved surface portion formed as a result of being pressed by the second mold, and the pressing load in the second step and the load-bearing capacity of the press machine. Typically, the second direction can be the normal direction of the main surface in the target shape of the shoulder curved surface portion. For example, when the main surface in the target shape of the shoulder curved surface portion constitutes a seating surface, the normal direction of the seating surface can be the second direction.

[0032] Means and methods for driving the second mold in the above-described direction are not particularly limited. Typically, as will be described in detail later, in a press machine including a cam mechanism including a cam driver having an inclined surface inclined in the second direction and a cam slider configured to abut against the cam driver and slide along the inclined surface, the second mold can be driven in the second direction by the cam mechanism. In this case, by setting the inclined surface of the cam driver at an angle parallel to the second direction and sliding the cam slider in the second direction, the second mold can be moved in the second direction to press the shoulder curved surface portion in the second direction by the second mold.

[0033] However, preparing a cam driver having an inclined surface that exactly matches the normal direction of the main surface in the target shape of the shoulder curved surface portion for each individual molded body may lead to an increase in the manufacturing cost of the molded body. Therefore, in the actual manufacturing process of such a molded body, within the scope where it is possible to effectively reduce the material removal in the shoulder curved surface portion, a cam driver having an inclined surface inclined at an angle close to the normal direction can be selected and used from existing cam drivers.

[0034] FIG. 2 is a schematic diagram illustrating the configuration of the press machine as described above, the positions of the second dies, and the changes in the shape of the workpiece (formed body) as the second step progresses. As shown in FIG. 2(a), the press machine 100 includes a total of two rams 110a and 110b, one on each side left and right facing the drawing. Further, the press machine 100 includes a cam mechanism including cam drivers 23a and 23b having inclined surfaces inclined in the second direction and cam sliders 24a and 24b configured to abut against the cam drivers 23a and 23b respectively and slide along the inclined surfaces. The two second dies 22a and 22b are respectively attached to the two rams 110a and 110b via the cam sliders 24a and 24b. In addition, the press machine 100 includes a pad 22c for restraining the shape of the central portion of the bulging portion of the first formed body 11.

[0035] When the second step is started using the press machine 100 having the above-described configuration, the two rams 110a and 110b are driven by a drive mechanism (not shown), and as indicated by the black arrows, the second dies 22a and 22b begin to descend. Eventually, as shown in FIG. 2(b), the cam sliders 24a and 24b respectively abut against the inclined surfaces of the cam drivers 23a and 23b. After this point, as indicated by the white arrows in FIG. 2(c), the cam sliders 24a and 24b slide in the second direction along the inclined surfaces of the cam drivers 23a and 23b respectively. Accordingly, the moving directions of the second dies 22a and 22b attached to the cam sliders 24a and 24b also move in the second direction respectively, and press the shoulder curved surface portions of the bulging portion of the first formed body 11 in the second direction.

[0036] FIG. 3 is a schematic diagram that more specifically illustrates the changes in the position of the second mold and the shape of the workpiece (formed object) in the second step included in the first method. FIG. 3(a) corresponds to FIG. 2(a) described above, and for the purpose of making it easier to understand the changes in the position of the second mold and the shape of the workpiece (formed object) in the second step, only the first formed body 11 as the workpiece (formed object), the second molds 22a and 22b, and the pad 22c are depicted. FIGS. 3(b) to (e) show step by step the changes in the position of the second mold and the shape of the workpiece (formed object) after the second step is started, and FIG. 3(f) shows the second formed body 12 obtained as a result of the second step. In FIGS. 3(b) to (f), the pad 22c is omitted, and the range of the central part of the bulging part whose shape is restricted by the pad 22c is indicated by two dashed lines.

[0037] When the second step is started, as shown in FIGS. 3(b) and (c), the second molds 22a and 22b begin to descend (refer to the black arrows). Eventually, as described with reference to FIG. 2, the moving direction of the second molds 22a and 22b changes to the second direction by a cam mechanism (not shown) (refer to the white arrows). As a result, the shoulder curved surface part R2 of the bulging part of the first formed body 11 is pressed in the second direction, and the second formed body 12 is produced.

[0038] <Effect> As described above, in the first method, the shoulder curved surface part of the bulging part included in the first formed body formed in the first step is pressed in the direction (second direction) toward the inside of the bulging part rather than the pressing direction (first direction) in the first step in the second step. Therefore, further thinning at the shoulder curved surface part as occurs in the conventional method described above is effectively reduced. That is, according to the first method, in a press drawing process method for producing a formed body including a bulging part which is a part having a bulging shape, thinning at the shoulder curved surface part can be effectively reduced.

[0039] <<Second Embodiment>> Hereinafter, a press drawing process method according to the second embodiment of the present invention (hereinafter may be referred to as the "second method") will be described with reference to the drawings.

[0040] As described above, according to the first method, by pressing the shoulder curved surface portion of the bulging portion included in the first molded body formed in the first step in the direction (second direction) toward the inside of the bulging portion in the second step, further thinning of the shoulder curved surface portion is effectively reduced. When the second molded body obtained as a result has the final target shape, the second molded body can be used as the molded body of the final product.

[0041] However, for example, due to various factors such as the shape and thickness of the shoulder curved surface portion pressed by the second mold, the target shape of the shoulder curved surface portion formed as a result of being pressed by the second mold, and the pressing load in the second step and the load-bearing capacity of the press machine, etc., it is also assumed that it may be difficult to achieve the final target shape by the second step.

[0042] <Configuration> Therefore, the second method is the first method described above and is a press drawing process method that further includes the following third step. Third step: A step of producing a third molded body, which is a molded body having a target shape, by pressing at least a part of the second molded body with a third mold.

[0043] Figure 4 is a flowchart illustrating the flow of each step included in the second method. As is clear from the above, the second method is the same press drawing process method as the first method described above, except that the above third step (step S30) is executed after the first step (step S10) and the second step (step S20) included in the first method described above. Therefore, since the first step and the second step have already been described in detail in the description regarding the first method described above, the description here is omitted, and the following description mainly focuses on the third step.

[0044] In the third step, as described above, by pressing at least a part of the second molded body produced in the second step with a third mold, a third molded body, which is a molded body having a target shape, is produced. The part of the second molded body pressed by the third mold includes at least a part that could not achieve the final target shape in the second step. Specific examples of such parts include, for example, the shoulder curved surface part that approached the target shape but did not reach the target shape in the second step, and parts other than the shoulder curved surface part of the bulging part where unintended deformation occurred due to the pressing on the shoulder curved surface part in the second step, etc.

[0045] Therefore, the third mold used in the third step is a mold having a molding surface that defines an internal space corresponding to the target shape, which can make the second molded body into a molded body (third molded body) having the target shape by pressing the second molded body. Incidentally, the direction in which the second molded body is pressed by the third mold in the third step may be the same as the first direction described above, may be the same as the second direction described above, or may be a direction different from both the first direction and the second direction described above.

[0046] <Effect> As described above, the second method is the first method described above, which is a press drawing process method in which a third step is executed after the first step and the second step. In the third step, by pressing at least a part of the second molded body with a third mold, a third molded body, which is a molded body having a target shape, is produced. Therefore, according to the second method, for example, even when it is difficult to achieve the final target shape in the second step due to various factors as described above, by executing the third step, a molded body having the final target shape can be surely obtained.

[0047] For the purpose of describing the present invention above, several embodiments having specific configurations have been described with reference to the accompanying drawings at times. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments, and it goes without saying that appropriate modifications can be made within the scope of the matters described in the claims and the specification. For example, in the drawings referred to in the description so far, the case where two shoulder curved surfaces are simultaneously pressed by two second molds in the second step has been illustrated. However, the number of shoulder curved surfaces pressed by the second mold in the second step may be one, or may be three or more.

Explanation of Signs

[0048] 1... Preform, 2... Mold (upper mold), 3... Target molded body, 11... First molded body (preform), 12... Second molded body (target molded body), 22a and 22b... Second mold, 22c... Pad, 23a and 23b... Cam driver, 24a and 24b... Cam slider, 100... Press machine, and 110a and 110b... Ram.

Claims

1. A press drawing method for producing a molded body including a bulging portion, which is a portion having a bulging shape, comprising: A first step is a step of producing a first molded body that is a molded body including a bulging portion that is a portion having a bulging shape by pressing a plate material that is a plate-shaped substrate in a first direction with a first mold; and a second step of pressing at least a part of the shoulder curved surface portion, which is a portion extending from the boundary position between the top surface and the side surface of the bulge portion to the side surface, with a second mold in a second direction that is inclined with respect to the first direction and toward the inside of the bulge portion in a normal direction of one of the surfaces that constitute the target shape of the shoulder curved surface portion, while restraining the shape of the central portion of the bulge portion of the first molded body, thereby producing a second molded body that is a molded body having the shoulder curved surface portion closer to a target shape than the shape of the shoulder curved surface portion of the first molded body; A press drawing method comprising the steps of:

2. The press drawing method according to claim 1, a third step of pressing at least a part of the second molded body with a third mold to produce a third molded body having a target shape; The press drawing method further comprises:

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