FORMATION METHOD OF SIDEWALL PART

Description

TECHNICAL FIELD

The present invention relates to a formation method of a sidewall part.

BACKGROUND ART

For example, when a product 200 comprising a top plate part 210 and a sidewall part (flange part) 220 installed upright at an approximately right angle from an end part of the top plate part 210 as exemplified in FIG. 1 is integrally molded from a tabular blank which is not shown by press processing, a “bending process” that is a process in which the sidewall part is formed by bending work and/or drawing work is generally performed. (a) of FIG. 2 is a schematic sectional view for showing an example of such a bending process. However, in FIG. 2, only a part of the tabular blank 100 in which one sidewall part 220 of the product 200 is molded by the bending process is illustrated instead of the whole of the tabular blank 100.

In the example shown in (a) of FIG. 2, an end part projecting from between a first lower mold die 11 and a first pad 21 of the tabular blank 100 sandwiched and held between the first lower mold die 11 and the first pad 21 is bent at an approximately right angle with a first bending blade 31 driven to a direction of an outlined white arrow shown in the drawing. As a result, a first intermediate blank 110 with an integrally molded sidewall part is manufactured.

However, as exemplified on the right hand side in (a) of FIG. 2, the sidewall part may open due to spring back and the angle between the top plate part and the sidewall part (which may be referred to as a “flange angle” hereafter) may become larger than an approximately right angle when the first intermediate blank 110 is picked out from a mold after completion of the bending process. Therefore, a process referred to as a “restriking process” is widely performed as additional processing such that the flange angle becomes an approximately right angle as a result of the sidewall part being opened due to the spring back after the bending process. The restriking process is a process in which the sidewall part is pushed in until the flange angle reaches a restrike angle that is an angle (acute angle) which is smaller than a right angle by an angle corresponding to an opening angle of the sidewall part due to the spring back (which may be referred to as a “spring back amount” hereafter) and thereby the spring back amount is offset.

(b) of FIG. 2 is a schematic sectional view for showing an example of a restriking process as the above. In the example shown in (b) of FIG. 2, the first intermediate blank 110 with the top plate part is sandwiched and held between the first pad 21 and a second lower mold die 12 in which an angle of a corner opposing to a bent part (boundary part between the top plate part and the sidewall part) of the first intermediate blank 110 is a restriking angle that is an acute angle, and the sidewall part of the first intermediate blank 110 pushed in with a second bending blade 32 driven in a direction of the outlined white arrow shown in the drawing. As a result, the second intermediate blank 120 in which the angle between the top plate part and the sidewall part (flange angle) is the restriking angle (acute angle) is manufactured. However, as exemplified on the right-hand side of (b) of FIG. 2, the sidewall part opens due to spring back and the flange angle can become an approximately right angle when the second intermediate blank 120 is picked out from the mold after completion of the restriking process.

However, since the spring back amount differs according to materials constituting the blanks, shapes of products to be molded and/or processing conditions, etc., for example, it is necessary to estimate the amount of spring back carefully for each products in order to set up the restriking angle appropriately. Moreover, even though the restriking angle is set up appropriately in this way, it is difficult to eliminate variation for each individual processed products completely in a mass production. Therefore, a “trimming process” that is a process in which the sidewall part is molded longer than its target shape expecting a certain amount of variation and thereafter a surplus part is cut off from the sidewall part has been widely performed as additional processing.

(c) of FIG. 2 is a schematic sectional view for showing an example of a trimming process as the above. In the example shown in (c) of FIG. 2, the top plate part of the second intermediate blank 120 is sandwiched and held between a third lower mold die 13 and the first pad 21, the sidewall part of the second intermediate blank 120 is sandwiched and held between the third lower mold die 13 and a second pad 22, and a surplus part at a tip of the sidewall part of the second intermediate blank 120 is cut off by the third lower mold die 13 and a first punch 41 driven in the direction of the outlined white arrow shown in the drawing. As a result, a scrap 300 is cut off from the tip of the sidewall part of the second intermediate blank 120, and the product 200 which comprises the top plate part 210 and the sidewall part 220 installed upright at an approximately right angle from the end part of the top plate part 210 and having a prescribed length as exemplified in FIG. 1 is molded integrally. However, cutting off the scrap 300 in a trimming process as mentioned above leads to waste of resources, and it causes deterioration of the product yield.

Moreover, when the length of the sidewall part 220 is short like the product 200 exemplified in FIG. 1, it is necessary to make small the width (dimension in an extending direction of the sidewall part) of the third lower mold die 13 used in the above-mentioned trimming process. Namely, since it is necessary to make the third lower mold die 13 thin according to the length required for the sidewall part 220 like the product 200, it may become difficult to configure the third lower mold die 13 so as to have durability for withstanding stress and/or impact which acts when cutting off the scrap 300 by the first punch 41.

On the other hand, in the Patent Literature 1 (PTL 1, Japanese Patent Application Laid-Open (kokai) No. 2001-225111), and the Patent Literature 2 (PTL 2, Japanese Patent Application Laid-Open (kokai) No. 2014-91140), methods which perform what is called “coining processing” that is processing in which a blank having sidewall part formed by bending work and/or drawing work and an approximately U character-like cross section is fitted (restrained) inside a mold and the tip end of the sidewall part is struck (pressed) toward its base end side are disclosed. In accordance with such methods, it is supposed that sufficient compressive residual stress can be given and fatigue strength can be improved while raising dimensional accuracy in the tip end shape of the sidewall part. However, in these methods, the problem that the sidewall part opens due to spring back and the flange angle becomes larger than a predetermined angle (for example, approximately right angle) when the product is picked out from the mold after completion of the bending process as mentioned above is not taken into consideration at all.

Furthermore, in the Patent Literature 3 (PTL 3, Japanese Patent Application Laid-Open (kokai) No. 2014-221493), a method in which a box body which comprises a top plate part and a sidewall part installed upright from the top plate part by multistage warm-press processing covering from a metal plate consisting of a specific material, such as a magnesium, is disclosed. In accordance with the method, it is supposed that a box object which has a sharp corner part can be provided by performing bending work and/or drawing work and coining processing simultaneously. However, also in this method, the problem that the sidewall part opens due to spring back and the flange angle becomes larger than a predetermined angle (for example, approximately right angle) when the product is picked out from the mold after completion of the bending process as mentioned above is not taken into consideration at all.

As the above, in the art, in a method in which a product which comprises a top plate part and a sidewall part (flange part) installed upright at a predetermined angle (for example, an approximately right angle) from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank consisting of a common material, a technology which can cancel or reduce spring back without performing the above-mentioned restriking process as additional processing is desired.

CITATION LIST

Patent Literature

• • [PTL 1] Japanese Patent Application Laid-Open (kokai) No. 2001-225111
  • [PTL 2] Japanese Patent Application Laid-Open (kokai) No. 2014-91140
  • [PTL 3] Japanese Patent Application Laid-Open (kokai) No. 2014-221493

SUMMARY OF INVENTION

Technical Problem

As mentioned previously, in the art, in a method in which a product which comprises a top plate part and a sidewall part (flange part) installed upright at a predetermined angle (for example, an approximately right angle) from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank consisting of a common material, a technology which can cancel or reduce spring back without performing the above-mentioned restriking process as additional processing is desired.

Solution to Problem

In view of the above-mentioned problem, as a result of diligent research, the present inventor has found out that, by sandwiching and holding a top plate part of an intermediate blank which comprises the top plate part and a sidewall part formed integrally by bending an end part of a tabular blank at a predetermined first angle and pressing the tip end part of the sidewall part of the intermediate blank toward the base end side while maintaining a state where the sidewall part of the intermediate blank in which the sidewall part opened due to spring back and a flange angle that is the angle between the top plate part and the sidewall part became larger than the first angle has been pushed back until the flange angle coincides with the first angle.

Specifically, a formation method of a sidewall part according to the present invention (which may be referred to as a “present invention method” hereafter) is a formation method of a sidewall part in a method in which a product comprising a top plate part and a sidewall part installed upright at a first angle that is a predetermined angle from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank. The present invention method includes a first step to a third step listed below.

The first step is a step in which an intermediate blank comprising a top plate part and a sidewall part formed integrally by bending an end part of the tabular blank at the first angle through bending work and/or drawing work is obtained.

The second step is a step in which the top plate part of the intermediate blank is sandwiched and held between a first holding member disposed outside the top plate part of the intermediate blank and a second holding member disposed inside the top plate part of the intermediate blank.

The third step is a step in which the sidewall part of the intermediate blank which was in a first state is brought to be in a second state and a first end part that is an end part on the tip end side of the sidewall part is pressed toward the base end side while maintaining the second state. The first state is a state where the sidewall part of the intermediate blank opens due to spring back and a flange angle that is the angle between the top plate part and the sidewall part is larger than the first angle. The second state is a state where the sidewall part is pushed back until the flange angle coincides with the first angle.

Advantageous Effects of Invention

In the present invention method, as mentioned above, in the third step, the end part on the tip end side of the sidewall part of the intermediate blank is pressed toward the base end side while maintaining a state where the sidewall part of the intermediate blank in which the sidewall part opened due to spring back and a flange angle that is the angle between the top plate part and the sidewall part became larger than the first angle has been pushed back until the flange angle coincides with the first angle. Thereby, residual stress causing spring back of the intermediate blank is canceled or reduced, and a product with the flange angle corresponding to the target first angle can be formed.

Namely, in accordance with the present invention method, in a method in which a product which comprises a top plate part and a sidewall part (flange part) installed upright at a predetermined angle (for example, an approximately right angle) from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank consisting of a common material, spring back can be canceled or reduced without performing the above-mentioned restriking process as additional processing.

Other objectives, other features and accompanying advantages of the present invention will be easily understood from the following explanation about respective embodiments of the present invention described referring to drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view for showing an example of a product comprising a top plate part and a sidewall part installed upright at an approximately right angle from an end part of the top plate part.

FIG. 2 is a schematic view for showing an example of a method according to a conventional technology in which a sidewall part installed upright at an approximately right angle from an end part of a top plate part.

FIG. 3 is a flow chart for exemplifying a flow of respective steps included in a formation method of a sidewall part according to a first embodiment of the present invention (first method).

FIG. 4 is a schematic view for exemplifying a change of a shape and the like in a molding process to a product comprising a top plate part and a sidewall part from a tabular blank by the first method.

FIG. 5 is a schematic view for exemplifying one specific means for obtaining an intermediate blank comprising a top plate part and sidewall part formed integrally by bending an end part of a tabular blank at a first angle in the first step.

FIG. 6 is a schematic view for exemplifying one specific means for pressing an end part on the tip end side of the sidewall part of the intermediate blank toward the base end side while pushing back the sidewall part in a first state in the third step and bringing the intermediate blank to a second state.

FIG. 7 is a schematic view for exemplifying a situation where the third step is performed by advancing a punch having a predetermined shape in a first direction that is a predetermined direction in a formation method of a sidewall part according to a second embodiment of the present invention (second method).

FIG. 8 is a schematic view for exemplifying a situation where a first end part is pressed toward the base end side in a state where a part including at least the first end part of the sidewall part of the intermediate blank is housed in the inside of a closed space in the third step included in a formation method of a sidewall part according to a third embodiment of the present invention (the third method).

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereafter, a formation method of a sidewall part according to a first embodiment of the present invention (which may be referred to as a “first method” hereafter) will be explained.

The first method is a formation method of a sidewall part in a method in which a product comprising a top plate part and a sidewall part installed upright at a first angle that is a predetermined angle from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank. A material constituting the tabular blank is not limited as long as it is possible to obtain an intermediate blank comprising a top plate part and sidewall part formed integrally by bending an end part of the tabular blank through bending work and/or drawing work. As examples of such materials, metals such as stainless steel, copper and aluminum as well as alloys containing these metals and the like can be mentioned, for example. The shape of the tabular blank is not limited in particular as long as at least a part which will become the top plate part and the sidewall part is tabular, and the shape may be planar or curved, and non-tabular part may exist in regions other than the parts which will become the top plate part and the sidewall part. Typically, the shape of the tabular blank is a planar rectangle, a planar elliptical or planar circular, for example.

The number of the sidewall parts installed upright at the end part of the top plate part may be one, or may be plural. When the number of the sidewall parts is plural, all the sidewall parts may be installed upright at an identical first angle on the same side with respect to the top plate part, or a part of the sidewall parts may be installed upright at a different first angle with respect to the top plate part. In the latter case, a part of the sidewall parts may be installed upright toward the side opposite to other sidewall parts with respect to the top plate part. Furthermore, the first method can be also applied to a method in which an annular sidewall part is prepared so as to surround a peripheral edge of the top plate part to mold a product with a bottomed cylindrical shape.

As shown in the flow chart exemplified in FIG. 3, for example, the first method includes a first step to a third step which will be explained in detail below. In the following explanation, details of respective steps included in the first method will be mentioned, referring to FIG. 4 and FIG. 5 in addition to FIG. 3. FIG. 3 is a flow chart for exemplifying a flow of respective steps included in the first method, and FIG. 4 is a schematic view for exemplifying a change of a shape and the like in a molding process to a product comprising a top plate part and a sidewall part from a tabular blank by the first method. However, similarly to the previously referred FIG. 2, only a part of the tabular blank 100 in which one sidewall part 220 of the product 200 is molded by the bending process is illustrated instead of the whole of the tabular blank 100 also in FIG. 4 and FIG. 5.

As exemplified in FIG. 3, the first step is first performed in Step S10. The first step is a step in which an intermediate blank comprising a top plate part and a sidewall part formed integrally by bending an end part of the tabular blank at the first angle through bending work and/or drawing work is obtained. Specifically, for example, an end part of the tabular blank 100 as exemplified in (a) of FIG. 4 can be bent by bending work and/or reducing work at a first predetermined angle θ1 as shown by the black-painted arrow in (b) of FIG. 4.

FIG. 5 is a schematic view for exemplifying one specific means for obtaining an intermediate blank 130 comprising a top plate part 131 and sidewall part 132 formed integrally by bending the end part of the tabular blank 100 at the first angle θ1 in the first step as described above. First, as exemplified in (a) of FIG. 5, the tabular blank 100 is sandwiched and held between a first lower mold die 11 and a first pad 21. Next, as exemplified in (b) of FIG. 4 and (a) of FIG. 5, an end part of the tabular blank 100 projecting from between the first lower mold die 11 and the first pad 21 is bend at the predetermined first angle θ1 with a first bending blade 31 driven in a direction of the outlined white arrow shown in the drawing (refer to the arrow hatched with oblique lines in (b) of FIG. 5). As a result, as exemplified in (b) of FIG. 4 and (b) of FIG. 5, the intermediate blank 130 comprising the top plate part 131 and the sidewall part 132 formed integrally can be obtained. Although the first angle θ1 is an approximately right angle typically, it is not limited to an approximately right angle and it can be an arbitrary angle required for the finally fabricated product.

However, similarly to the conventional technology explained at the beginning of the present description while referring to (a) of FIG. 2, the sidewall part 132 may open due to spring back when the intermediate blank 130 is picked out from a mold after completion of the first step (Step S10), as shown with the outlined white arrow in (c) of FIG. 4. This is because stress in a shrinkage direction (a black-painted arrow) and stress in an extension direction (outlined white arrow) remain respectively in the outside and inside of a bent part that is the boundary part between the top plate part 131 and the sidewall part 132 of the intermediate blank 130 as the result that tensile stress and compression stress acted respectively on the outside and inside of the bent part when bending the tabular blank 100 as exemplified in (c) of FIG. 5. Consequently, as exemplified in (c) of FIG. 4, the angle between the top plate part 131 and the sidewall part 132 (flange angle θf) becomes a second angle θ2 larger than the target first angle θ1.

A state where the sidewall part of the intermediate blank opens due to spring back and a flange angle that is the angle between the top plate part and the sidewall part is larger than the first angle may be referred to as a “first state” hereafter.

Then, in the first method, the second step is performed in the following Step S20, as exemplified in FIG. 3. The second step is a step in which the top plate part of the intermediate blank is sandwiched and held between a first holding member disposed outside the top plate part of the intermediate blank and a second holding member disposed inside the top plate part of the intermediate blank. Specifically, as exemplified in (d) of FIG. 4, the top plate part 131 of the intermediate blank 130 is sandwiched and held between the first holding member 51 (for example, a die) disposed outside the top plate part 131 of the intermediate blank 130 and a second holding member 52 (for example, a pad) disposed inside the top plate part 131 of the intermediate blank 130.

Next, the third step is performed in Step S30. The third step is a step in which the sidewall part of the intermediate blank which was in a first state is brought to be in a second state and a first end part that is an end part on the tip end side of the sidewall part is pressed toward the base end side while maintaining the second state. The first state is a state where the sidewall part of the intermediate blank opens due to spring back and a flange angle that is the angle between the top plate part and the sidewall part is larger than the first angle. The second state is a state where the sidewall part is pushed back until the flange angle coincides with the first angle. Specifically, as shown by the black-painted arrow in (d) of FIG. 4, the sidewall part 132 of the intermediate blank 130 is pushed back (by a pad or the like which is not shown, for example) until the flange angle θf coincides with the first angle θ1 and thereby the second state is attained. While maintaining this second state, the first end part E1 that is an end part on the tip end side of the sidewall part 132 of the intermediate blank 130 is pressed toward the base end side (bent part side), as shown by the arrow hatched with oblique lines in (d) of FIG. 4.

Specific means for pushing back the sidewall part 132 of the intermediate blank 130 in the first state where the sidewall part 132 opens due to spring back and bringing the intermediate blank 130 to be in the second state in the third step is not limited in particular. Moreover, specific means for pressing the end part on the tip end side of the sidewall part 132 of the intermediate blank 130 (first end part E1) toward the base end side while maintaining the second state is not limited in particular, either.

For example, (a) of FIG. 6 is a schematic view for exemplifying a state where the second step in which the top plate part of the intermediate blank 130 is of sandwiched and held between the first holding member 51 (die) disposed outside the top plate part of the intermediate blank 130 and the second holding member 52 (pad) disposed inside the top plate part of the intermediate blank 130 has been completed. Since the sidewall part of the intermediate blank 130 is not restrained in this state, the intermediate blank 130 is in the first state where the sidewall part opens due to spring back and the flange angle θf is the second angle θ2.

Next, the third step is started, and the second state is attained by pushing back the sidewall part of the intermediate blank 130 until the flange angle θf is coincides with the first angle θ1 using the first pressing member 61 (for example, a pad) (refer to the black-painted arrow) as exemplified in (b) of FIG. 6. While maintaining this second state, the end part on the tip end side of the sidewall part of the intermediate blank 130 (first end part E1) is pressed toward the base end side by the second pressing member 62 (for example, a punch), as exemplified in (c) of FIG. 6 (refer to the arrow hatched with oblique lines). The drive system of the first pressing member 61 and the second pressing member 62 may be a mechanical drive by a cam mechanism, etc., or may be a control drive by an actuator, etc.

Although the sidewall part of the intermediate blank which used to be in the first state can be brought to be in the second state and the third step in which the first end part that is an end part on the tip end side of the sidewall part of the intermediate blank is pressed toward the base end side while maintaining the second state can be performed as mentioned above, the above is only an example of the means for performing the third step to the last.

By performing the third step (Step S30) as the above, the stress history which the tabular blank 100 received in the first step (Step S10) is overwritten, and the residual stress causing the above-mentioned spring back is canceled. As a result, the possibility that the sidewall part 132 will open due to spring back when the intermediate blank 130 is picked out from a mold after completion of the third step is canceled or reduced. Namely, the product 200 comprising the top plate part 210 and the sidewall part 220 installed upright from the end part of the top plate part 210 at the first angle θ1 (not shown in FIG. 1) that is a predetermined angle as exemplified in FIG. 1 can be molded integrally from the tabular blank 100 by press working at an ordinary temperature.

In addition, as mentioned above, in the third step, the first end part E1 that is an end part on the tip end side of the sidewall part 132 of the intermediate blank 130 is pressed toward the base end side (bent part side). Since stress in an extension direction remains in the sidewall part 132 as a result of the stress history, the sidewall part 132 opens slightly due to spring back resulting from the residual stress when the intermediate blank 130 is picked out from a mold after completion of the third step (refer to the part hatched with oblique lines in (e) of FIG. 4). From a viewpoint of attaining high dimensional accuracy in the product 200, it can be considered to perform the “trimming process” described at the beginning of the present specification as additional processing. However, as mentioned above, such additional processing has a possibility of causing problems, such as deterioration of the product yield and/or reduction in durability of lower mold die in a trimming process. Therefore, it is preferable to set up the pressing force and the amount of pressing of the first end part E1 in the third step according to a material of the tabular blank 100, thickness of the tabular blank 100 and length of the sidewall part 220 in the product 200, etc., for example, such that length of the sidewall part 132 after extension due to spring back satisfies dimensional accuracy required for the sidewall part 220 in the product 200.

Effects

In the first method, as mentioned above, in the third step, the end part on the tip end side of the sidewall part of the intermediate blank is pressed toward the base end side while maintaining a state where the sidewall part of the intermediate blank in which the sidewall part opened due to spring back and a flange angle that is the angle between the top plate part and the sidewall part became larger than the first angle has been pushed back until the flange angle coincides with the first angle. Thereby, residual stress causing spring back of the intermediate blank is canceled or reduced, and a product with the flange angle corresponding to the target first angle can be formed.

Namely, in accordance with the first method, in a method in which a product which comprises a top plate part and a sidewall part (flange part) installed upright at a predetermined angle (for example, an approximately right angle) from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank consisting of a common material, spring back can be canceled or reduced without performing the above-mentioned restriking process as additional processing.

Second Embodiment

Hereafter, a formation method of a sidewall part according to a second embodiment of the present invention (which may be referred to as a “second method” hereafter) will be explained.

As mentioned previously, specific means for pressing the end part on the tip end side of the sidewall part of the intermediate blank (first end part) toward the base end side while maintaining the intermediate blank which was in the first state where the sidewall part opened due to spring back in the second state where the sidewall part of the intermediate blank is pushed back is not limited in particular.

The means exemplified in FIG. 6 is only an example of the means for performing the third step.

However, in the means exemplified in FIG. 6, the first pressing member 61 for pushing back the sidewall part of the intermediate blank 130 until the flange angle θf coincides with the first angle θ1 to bring the intermediate blank 130 to be in the second state (refer to the black-painted arrow) and a driving unit (not shown) for driving the first pressing member 61 as well as the second pressing member 62 for pressing the end part (first end part E1) on the tip end side of the sidewall part of the intermediate blank 130 (refer to the arrow hatched with oblique lines) while maintaining such a second state and a driving unit (not shown) for driving the second pressing member 62 are required.

From a viewpoint of reducing the labor, components and cost required for implementation of the formation method of a sidewall part according to the present invention (present invention method) as much as possible, it is preferable to decrease the number of the components required for performing the third step and make the driving units simpler.

Configuration

Then, the second method is the above-mentioned first method, characterized in that the third step is performed by advancing a punch which has a predetermined shape toward the intermediate blank in a first direction that is a predetermined direction. Hereafter, details of the third step performed in the second method will be explained referring to FIG. 7.

FIG. 7 is a schematic view for exemplifying a situation where the third step is performed by advancing a punch having a predetermined shape in a first direction that is a predetermined direction in the second method. The first direction is a direction parallel to a direction from the tip end side toward the base side of the sidewall part of the intermediate blank in the second state mentioned previously. In the example shown in FIG. 7, the first direction is indicated by the upward arrow D1 hatched with oblique lines (which may be referred to as a “first direction D1” hereafter).

Moreover, as exemplified in (a) of FIG. 7, on a side surface of the punch 70 opposing to the sidewall part 132 of the intermediate blank 130 used in the second state, a first surface 71, a second surface 72 and a third surface 73 listed below.

The first surface 71 is an inclined plane formed at an end part on the tip end side (the downstream side in the first direction D1, namely the upper side in the drawing) of the punch 70 and inclined at a predetermined angle θs with respect to the first direction D1 (refer to (b) of FIG. 7). As exemplified in FIG. 7, the first surface 71 inclines such that a distance from (the sidewall part 132 of) the intermediate blank 130 in a direction perpendicular to the first direction D1 may become smaller as progressing to the base end side (the upstream side in the first direction D1, namely the lower side in the drawing) from the tip side of the punch 70.

The second surface 72 is a surface which adjoins the base end side of the first surface 71 and has a shape corresponding to the outer surface of the sidewall part 132 of the intermediate blank 130 in the second state. In the example shown in FIG. 7, the outer surface of the sidewall part 132 of the intermediate blank 130 in the second state is a plane extending particularly to the top plate part 131. Therefore, the second surface 72 of the punch 70, which has a shape corresponding to the outer surface of the sidewall part 132 of the intermediate blank 130 in the second state is also a plane extending particularly to the top plate part 131, and opposes to the outer surface of the sidewall part 132 of the intermediate blank 130 in the second state.

The third surface 73 is a surface which adjoins the base end side of the second surface 72 and has a shape which can come into contact with the first end part E1 of the intermediate blank 130 in the second state. In the example shown in FIG. 7, the third surface 73 is formed as a plane extending particularly from the second surface 72, and constitutes a level difference (step) with a height corresponding to the thickness of the first end part E1 of the intermediate blank 130.

In the third step included in the second method, in association with advancing the punch 70 toward the intermediate blank 130 in the first direction D1, the processing listed below are sequentially executed. In the example shown in FIG. 7, the punch 70 is advanced in the first direction D1 toward the intermediate blank 130 fixed at a predetermined position by the top plate part 131 being sandwiched and held between the first holding member 51 (die) and the second holding member 52 (pad). However, the punch 70 should just advance in the first direction D1 relatively toward the intermediate blank 130. For example, contrary to the example shown in FIG. 7, the intermediate blank 130 with the top plate part 131 sandwiched and held between the first holding member 51 and the second holding member 52 may be advanced in a direction opposite to the first direction D1 toward the punch 70 fixed at a predetermined position.

First, as exemplified in (a) of FIG. 7, the first end part E1 is brought into contact with the first surface 71 of the punch 70. Next, although not shown, by sliding the first end part E1 on the first surface 71, the sidewall part 132 of the intermediate blank 130 soon begins to be housed into a space between the second surface 72 of the punch 70 and the second holding member 52 (for example, pad) from the first end part E1. At this time, the flange angle θf coincides with the target first angle θ1, and the second state has been attained. Furthermore, by sliding the second surface 72 on the outer surface of the sidewall part 132 of the intermediate blank 130, the first end part E1 is brought into contact with the third surface 73 while maintaining the second state, as exemplified in (b) of FIG. 7. In addition, as shown by a black-painted arrow in (b) of FIG. 7, the first end part E1 is pressed toward the base end side by the third surface 73.

As a result of performing the third step by advancing the punch 70 in the first direction D1 as mentioned above, the stress history which the tabular blank 100 received in the first step (Step S10) is overwritten, and stress in a shrinkage direction (a black-painted arrow) in the outside of the bent part of the intermediate blank 130 and stress in an extension direction (outlined white arrow) in the inside of the bent part of the intermediate blank 130 are cancelled or reduced respectively, as exemplified in (c) of FIG. 7.

Effects

As mentioned above, in the second method, the third step is performed by advancing a punch which has a predetermined shape toward the intermediate blank in the first direction that is a predetermined direction. Namely, in the second method, the third step can be performed by a simpler configuration without requiring to drive many components intricately as exemplified in FIG. 6, for example. Therefore, in accordance with the second method, spring back of the intermediate blank in a method for molding a product comprising a top plate part and sidewall part formed integrally by press working at an ordinary temperature from a tabular blank consisting of a common material can be cancelled or reduced while suppressing increase of the required labor, components and cost

Third Embodiment

Hereafter, a formation method of a sidewall part according to a third embodiment of the present invention (which may be referred to as a “third method” hereafter) will be explained.

In the formation method of a sidewall part according to the present invention (present invention method) including the first method and the second method, as mentioned previously, in the third step, the end part on the tip end side of the sidewall part of the intermediate blank is pressed toward the base end side while maintaining a state where the sidewall part of the intermediate blank in which the sidewall part opened due to spring back and a flange angle that is the angle between the top plate part and the sidewall part became larger than the first angle has been pushed back until the flange angle coincides with the first angle. Thereby, residual stress causing spring back of the intermediate blank is canceled or reduced, and a product with the flange angle corresponding to the target first angle can be formed.

Namely, in accordance with the present invention method, in a method in which a product which comprises a top plate part and a sidewall part (flange part) installed upright at a predetermined angle (for example, an approximately right angle) from an end part of the top plate part is molded integrally by press processing at an ordinary temperature from a tabular blank consisting of a common material, spring back can be canceled or reduced without performing the above-mentioned restriking process as additional processing.

From a viewpoint of further improving dimensional accuracy in the shape of the sidewall part of the product formed by the present invention method, it is preferable to press the first end part in the inside of a closed space when pressing the end part on the tip end side of the sidewall part of the intermediate blank (first end part) maintained in the second state toward the base end side in the third step.

Configuration

Then, the third method is the above-mentioned second method, characterized in that, in the third step, the first end part is pressed toward the base end side in a state where a part including at least the first end part of the sidewall part of the intermediate blank is housed in the inside of a closed space.

Specific configurations of the above-mentioned closed space are not limited in particular, as long as residual stress causing spring back of the intermediate blank is cancelled or reduced by pressing the first end part toward the base end side and dimensional accuracy in the shape of the sidewall part of the product formed by the third method can be improved.

FIG. 8 is a schematic view for exemplifying a situation where the first end part is pressed toward the base end side in a state where a part including at least the first end part of the sidewall part of the intermediate blank is housed in the inside of a closed space in the third step included in the third method. FIG. 8 is the same as FIG. 6, except for the point that it is configured such that the first holding member 51 and the first pressing member 61 which are disposed outside the top plate part of the intermediate blank 130 come into contact with each other and thereby a closed space is defined by the second holding member 52 disposed inside the top plate part of the intermediate blank 130 and the first holding member 51 and the first pressing member 61 when the sidewall part of the intermediate blank 130 is pushed back until the flange angle θf coincides with the first angle θ1 (refer to the black-painted arrow) to attain the second state.

In the example shown in FIG. 8, as exemplified in (c), in a state where the sidewall part of the intermediate blank 130 is housed in the inside of the closed space defined by the second holding member 52, the first holding member 51 and the first pressing member 61, the first end part E1 of the sidewall part is pressed by the second pressing member 62 toward the base end side (refer to the arrow hatched with oblique lines). Thereby, dimensional accuracy in the shape of the sidewall part of the product formed by the third method can be improved further.

By the way, also in the configuration exemplified in FIG. 7 referred to in the explanation about the above-mentioned second method, the first end part is pressed toward the base end side in a state where the part of the sidewall part of the intermediate blank which includes the first end part at least is housed in the inside of the closed space. More specifically, in the example shown in FIG. 7, in the third step, the first end part E1 is pressed toward the base end side by the third surface 73 in a state where a closed space is defined by the first holding member 51 and the second holding member 52 as well as the second surface 72 and the third surface 3 of the punch 70 and the sidewall part of the intermediate blank 130 is housed in the inside of the closed space.

Effects

As mentioned above, in the third step included in the third method, the first end part is pressed toward the base end side in a state where a part including at least the first end part of the sidewall part of the intermediate blank is housed in the inside of a closed space. Therefore, in accordance with the third method, spring back of the intermediate blank in a method for molding a product comprising a top plate part and sidewall part formed integrally by press working at an ordinary temperature from a tabular blank consisting of a common material can be cancelled or reduced while further improving dimensional accuracy in the shape of the sidewall part of the formed product.

Although some embodiments which have specific configurations have been explained referring to accompanying drawings as the above for the purpose of explaining the present invention, it should not be interpreted that the scope of the present invention is limited to these exemplary embodiments, and it is needless to say that modifications can be properly added within the limits of the matter described in the claims and the specification.

For example, application of a formation method of a sidewall part according to the present invention (present invention method) is not limited to a case where a product having a planar sidewall part (flange) erected from one end edge in a shape of a straight line of a top plate part as mentioned above is molded. For example, the present invention method can be applied also to a case where a product having a curved sidewall part (flange) erected from one end edge in a shape of a curved line of a top plate part is molded. Moreover, the present invention method can be applied also to a case where a product having a sidewall part (flange) erected from all over the end edge of a top plate part is molded. Furthermore, the present invention method can be applied also to a case where a bowl-shaped body that is a product having a sidewall part (flange) erected from all over the circumference of an end edge of a top plate part in a shape pf a disk, for example, is molded.

REFERENCE SIGNS LIST

• • 12: Second Lower Mold Die
  • 13: Third Lower Mold Die
  • 21: First Pad
  • 22: Second Pad
  • 31: First Bending Blade
  • 32: Second Bending Blade
  • 41: First Punch
  • 51: First Holding Member
  • 52: Second Holding Member
  • 61: First Pressing Member
  • 62: Second Pressing Member
  • 70: Punch
    • 71: First Surface
    • 72: Second Surface
    • 73: Third Surface
  • 100: Tabular Blank
    • 110: First Intermediate Blank
    • 120: Second Intermediate Blank
    • 130: Intermediate Blank
      • 131: Top Plate Part
      • 132: Sidewall Part
  • 200: Product
    • 210: Top Plate Part
    • 220: Sidewall Part
  • 300: Scrap