Pressing Machine, Pressing Method, and Punched Article

TECHNICAL FIELD

The present invention relates to a press working apparatus that performs blanking work on a relatively thick sheet, which will serve, for example, as the raw material for a press-formed part for an automatic transmission, an element of a belt for a continuously variable transmission, or the like, and relates to a press working method and a blanked product manufactured by the press working apparatus.

BACKGROUND ART

An example of a conventional press working apparatus of the same type is the press working apparatus proposed and described in Patent Document 1 (a press die apparatus for perforation). Such a press working apparatus (hereinafter referred to as a “first conventional apparatus”) is equipped with two working units (first and second working units). The working units are respectively provided with a punch and a die. In the first working unit, the punch and the die are relatively moved, such that a region of a sheet to be formed with a through hole having a predetermined shape (e.g. a shape with a generally circular cross section) is formed with a half-blanked portion having a shape that projects toward the die side. In other words, at a first stage in the first working unit, a region of the sheet to be formed with a through hole has a concave portion on a side facing the punch, and also has a half-blanked portion with a convex portion formed on a side facing the die.

Next in the second working unit, for cases where the half-blanked portion of the sheet is disposed between the punch and the die, the punch is disposed so as to be opposite the concave portion (of the half-blanked portion) of the sheet and the die is disposed so as to be opposite the concave portion (of the half-blanked portion) of the sheet. Furthermore, the diameter of the punch of the second working unit is formed smaller than the diameter of the through hole. At a second stage in the second working unit, the punch thereof presses the half-blanked portion of the sheet toward the die side, whereby the half-blanked portion becomes a blanked body and is blanked from the sheet. Accordingly, a through hole with a shape corresponding to the blanked body is formed in the sheet.

However, in cases where the half-blanked portion is blanked from the sheet to become a blanked body by the first conventional apparatus, a majority of a side wall surface (a blanked surface along the blanking direction on a region where the blanked body is blanked from the sheet) of the through hole in the sheet, and a majority of a side wall surface (a blanked surface along the blanking direction) of the blanked body respectively become rough cross sections. Therefore, if the respective blanked body and the sheet formed with the through hole are to be turned into blanked products, then all of the respective side wall surfaces, including such rough cross sections, should be made smooth. It is thus necessary to further utilize a separate device (such as a polishing device) in order to polish the side wall surface of the through hole and the side wall surface of the blanked body. Hence, in recent times, for cases where a blanked body is blanked from a sheet, apparatuses have been proposed that are capable of suppressing the formation of roughness on a cross section of the side wall surface of the through hole in the sheet. An example of such an apparatus is the press working apparatus (hereinafter referred to as a “second conventional apparatus”) described in Patent Document 2.

The second conventional apparatus is equipped with three working units (first, second, and third working units). The working units are respectively provided with a punch and a die. In the first working unit, almost identical to the first working unit in the first conventional apparatus, a half-blanked portion is formed at a region of a sheet where blanking work is performed. In the second working unit, almost identical to the second working unit in the first conventional apparatus, a hole (a blank hole) is formed in the sheet by blanking from the sheet a half-blanked portion, which becomes a blanked body. In this case, the blank hole is formed such that a diameter thereof is slightly smaller than the diameter of the through hole to be ultimately formed in the sheet. In the third working unit, a punch whose diameter is almost the same as the diameter of the through hole is pressed into a region to be formed with the through hole (a region surrounding the blank hole), whereby the punch performs shaving work on the side wall surface of the blank hole. As a consequence, the sheet becomes a blanked product formed with a through hole that has a side wall surface with a sheared-surface shape.

Incidentally, in the second conventional apparatus, the three stages of forming a half-blanked portion in a sheet, forming a blank hole in the sheet, and performing shaving work on the side wall surface of the blank hole are performed in that order. Therefore, in actuality, the number of processes needed to form a through hole shaped with a sheared-surface shape in a sheet is no different from a press working method that uses the first conventional apparatus to perform the first stage and the second stage, and uses a separate device to additionally perform the third stage (a polishing process). Moreover, the second conventional apparatus has a further problem: the third working unit for performing shaving work on the side wall surface of the blank hole (the third stage) must be further provided, and therefore the apparatus structure increases in size by a corresponding amount compared to the first conventional apparatus.

Patent Document 1: Japanese Patent Application Publication No. JP-A-9-174492 (FIGS. 2 and 3)

Patent Document 2: Japanese Patent Application Publication No. Jp-A-2004-176853 (Claim 1, FIG. 1)

DISCLOSURE OF THE INVENTION

The present invention was devised in light of the foregoing circumstances. It is an object of the present invention to provide a press working apparatus capable of forming into a sheared-surface shape at least a portion of blanked surfaces along the blanking direction on a region of a sheet from which a blanked body has been blanked and on the blanked body that has been blanked from the sheet, and capable of suppressing the generation of burrs on the sheet, while at the same time suppressing an increase in the size of the apparatus and the number of processes for performing blanking work on the sheet; and it is a further object of the present invention to provide a press working method and a blanked product.

In order to achieve the above object, a press working apparatus according to the present invention is a press working apparatus, which performs blanking work on a sheet, that includes: a first working unit having a first upper die and a first lower die, wherein at least one of the first upper die and the first lower die is mobile in the vertical direction with respect to the other, with the first upper die fixedly attached with at least one among an opposing first punch and a first die, and the first lower die fixedly attached with the other among the first punch and the first die, and a negative clearance is set between the first punch and the first die as viewed from the downward direction, and half-blanking work is performed on the sheet by relatively moving the first punch and the first die in the vertical direction; and a second working unit having a second upper die and a second lower die, wherein at least one of the second upper die and the second lower die is mobile in the vertical direction with respect to the other, with the second upper die fixedly attached with at least one among a second punch and a second die having a paired relationship, and the second lower die fixedly attached with the other among the second punch and the second die, and a positive clearance is set between the second punch and the second die as viewed from the vertical direction, and when a half-blanked portion that was formed in the sheet by half-blanking work performed by the first working unit is blanked to become a blanked body by the second punch, a blanked surface is formed along a blanking direction on a region where the blanked body is blanked from the sheet, and at least a portion of the blanked surface is subjected to shaving work performed by the second punch.

In the press working apparatus according to the present invention, the second punch is structured so as to achieve a form wherein a cross-sectional shape for the second punch when cut in a direction orthogonal to the vertical direction is a similar and enlarged version of a cross-sectional shape for the first punch when cut in a direction orthogonal to the vertical direction.

In the press working apparatus according to the present invention, the second punch is structured such that if the cross-sectional shape for the second punch when cut in a direction orthogonal to the vertical direction overlaps in the vertical direction with the cross-sectional shape for the first punch when cut in a direction orthogonal to the vertical direction, then there is a distance dimension of 0.01 mm to 0.3 mm between adjacent outer peripheral regions with mutually similar shapes.

In the press working apparatus according to the present invention, the first die is formed with a through hole running therethrough that extends in the vertical direction, and the second punch is structured such that the cross-sectional shape for the second punch when cut in a direction orthogonal to the vertical direction is a similar and enlarged shape of a hole shape of the through hole when the first die when is cut in a direction orthogonal to the vertical direction.

In the press working apparatus according to the present invention, the second punch is structured such that if the cross-sectional shape for the second punch when cut in a direction orthogonal to the vertical direction overlaps in the vertical direction with the cross-sectional shape for the first die when cut in a direction orthogonal to the vertical direction, then there is a distance dimension of 0.01 mm to 0.3 mm between an outer peripheral region of the cross section of the second punch and an inner peripheral region of the cross section of the first die, which have a mutually similar relationship.

The press working apparatus according to the present invention is a press working apparatus, which performs blanking work on a sheet, that includes: a first working unit having a first upper die and a first lower die, wherein at least one of the first upper die and the first lower die is mobile in the vertical direction with respect to the other, with the first upper die fixedly attached with at least one among an opposing first punch and a first die, and the first lower die fixedly attached with the other among the first punch and the first die, and a negative clearance is set between the first punch and the first die as viewed from the vertical direction, and half-blanking work is performed on the sheet by relatively moving the first punch and the first die in the vertical direction; and a second working unit having a second upper die and a second lower die, wherein at least one of the second upper die and the second lower die is mobile in the vertical direction with respect to the other, with the second upper die fixedly attached with at least one among a second punch and a second die having a paired relationship, and the second lower die fixedly attached with the other among the second punch and the second die, and a positive clearance is set between the second punch and the second die as viewed from the vertical direction, and when a half-blanked portion that was formed in the sheet by half-blanking work performed by the first working unit is blanked to become a blanked body by the second punch, a blanked surface is formed along a blanking direction on the blanked body, and at least a portion of the blanked surface is subjected to shaving work performed by the second die.

In the press working apparatus according to the present invention, the first die and the second die are respectively formed with insertion holes running therethrough in the vertical direction, and the second die is structured so as to achieve a form wherein a hole shape of the insertion hole when the second die is cut in a direction orthogonal to the vertical direction is a similar and scaled-down version of a hole shape of the insertion hole when the first die is cut in a direction orthogonal to the vertical direction.

In the press working apparatus according to the present invention, the second die is structured such that if a cross-sectional shape for the second die when cut in a direction orthogonal to the vertical direction overlaps in the vertical direction with a cross-sectional shape for the first die when cut in a direction orthogonal to the vertical direction, then there is a distance dimension of 0.01 mm to 0.3 mm between an outer peripheral region of a cross section of the second die and an inner peripheral region of a cross section of the first die, which have a mutually similar relationship.

In the press working apparatus according to the present invention, the first working unit is structured such that if the first punch is made to relatively approach the first die, then the first punch is made to approach up to a position that is separated only by a distance dimension that is 10% to 50% of a thickness dimension of the sheet.

In the press working apparatus according to the present invention, the first punch is formed such that a width dimension of the negative clearance is a width dimension that is 1% to 15% of the thickness dimension of the sheet.

In the press working apparatus according to the present invention, the second punch is fixedly attached with the second lower die if the first punch is fixedly attached with the first upper die, and the second punch is fixedly attached with the second upper die if the first punch is fixedly attached with the first lower die.

In the press working apparatus according to the present invention, the second punch is formed such that a width dimension of the positive clearance is a width dimension that is 0.3% to 8% of the thickness dimension of the sheet.

In the press working apparatus according to the present invention, at least one among an end edge portion on a side facing the sheet in the first punch and an inner-side edge portion on a side facing the sheet in the first die is subjected to chamfering work so as to have a curved surface.

In the press working apparatus according to the present invention, the curved surface formed on at least one among the end edge portion on a side facing the sheet in the first punch and the inner-side edge portion on a side facing the sheet in the first die is formed so as to achieve an arc shape, which has a curvature radius with a length dimension that is equal to or less than 7.5% of the thickness dimension of the sheet when the first punch and the first die are cut in the vertical direction.

In the press working apparatus according to the present invention, an end edge portion on a side facing the sheet in the second punch is subjected to chamfering work so as to have a curved surface.

In the press working apparatus according to the present invention, the curved surface of the end edge portion on a side facing the sheet in the second punch is formed so as to achieve an arc shape, which has a curvature radius with a length dimension that is equal to or less than 7.5% of the thickness dimension of the sheet when the second punch is cut in the vertical direction.

A blanked product according to the present invention is manufactured by blanking a blanked body from a sheet using a press working apparatus as structured above.

A press working method according to the present invention is a press working method, which performs blanking work on a sheet, that includes: a first stage where a first punch and a first die in a paired relationship are used to perform half-blanking work on a region where a blanked body is to be blanked in the sheet; and a second stage where a second punch and a second die in a paired relationship are used to blank the blanked body from the region in the sheet subjected to half-blanking in the first stage, and at such time, the second punch performs shaving work on at least a portion of a blanked surface along a blanking direction on a region where the blanked body is blanked.

A press working method according to the present invention is a press working method, which performs blanking work on a sheet, that includes: a first stage where a first punch and a first die in a paired relationship are used to perform half-blanking work on a region where a blanked body is to be blanked in the sheet; and a second stage where a second punch and a second die in a paired relationship are used to blank the blanked body from the region in the sheet subjected to half-blanking in the first stage, and at such time, the second die performs shaving work on at least a portion of a blanked surface along a blanking direction on the blanked body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic front view of a press working apparatus according to a first embodiment.

FIG. 2 is a schematic cross-sectional view showing a portion of a first working unit according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing how a first punch contacts a sheet in the first working unit.

FIG. 4 is a schematic cross-sectional view showing how the first working unit performs half-blanking work on the sheet.

FIG. 5 is a schematic cross-sectional view showing the first punch at its closest approach to a first die in the first working unit.

FIG. 6 is a schematic cross-sectional view showing a portion of a second working unit according to the first embodiment.

FIG. 7 is a schematic cross-sectional view showing the start of a stroke movement of a second punch toward a second die side in the second working unit.

FIG. 8 is a schematic cross-sectional view showing the second punch press a half-blanked portion of the sheet in the second working unit.

FIG. 9 is a schematic cross-sectional view showing the start of shaving work in the second working unit on a region to serve as a side wall surface of a through hole.

FIG. 10 is a schematic cross-sectional view showing the performance of shaving work in the second working unit on the region to serve as the side wall surface of the through hole.

FIG. 11 is a schematic cross-sectional view showing the blanked body being blanked from the sheet in the second working unit.

FIG. 12 is a schematic cross-sectional view showing the end of a second stage in the second working unit.

FIG. 13 is a schematic cross-sectional view showing a portion of the first working unit according to a second embodiment.

FIG. 14 is a schematic cross-sectional view showing a portion of the second working unit according to the second embodiment.

FIG. 15 is a schematic cross-sectional view showing the start of a stroke movement of the second punch toward the second die side in the second working unit.

FIG. 16 is a schematic cross-sectional view showing the second punch press the half-blanked portion of the sheet in the second working unit.

FIG. 17 is a schematic cross-sectional view showing the start of shaving work in the second working unit on a region to serve as the side wall surface of the blanked body.

FIG. 18 is a schematic cross-sectional view showing the performance of shaving work in the second working unit on the region to serve as the side wall surface of the blanked body.

FIG. 19 is a schematic cross-sectional view showing the blanked body being blanked from the sheet in the second working unit.

FIG. 20 is a schematic cross-sectional view showing the blanked body being blanked from the sheet in the second working unit according to a third embodiment.

FIG. 21 is a view showing a frame format of another example of a cross sectional-shape of the first punch and a cross-sectional shape of the second punch overlapped.

FIG. 22 is a plane view of a carrier formed by further processing the sheet press worked by the press working apparatus according to the first embodiment.

FIG. 23 is a cross-sectional arrow view taken along a line 23-23 in FIG. 23.

FIG. 24 is a plane view of a backing plate formed by processing the sheet press subsequent to press working by the press working apparatus according to the second embodiment.

FIG. 25A is a schematic cross-sectional view showing the performance of half-blanking work on a region formed with a notch portion on the sheet; FIG. 25B is a schematic cross-sectional view showing the notch portion formed on the sheet; and FIG. 25C is a schematic plane view showing the notch portion formed on the sheet.

BEST MODES FOR CARRYING OUT THE INVENTION
First Embodiment

Hereinafter, with reference to FIGS. 1 to 12, a first embodiment will be explained that realizes the present invention as a press working apparatus and a press working method which are used when a blanked body is blanked from a relatively thick sheet.

As FIG. 1 shows, a press working apparatus 11 according to the present embodiment has a first working unit 13 and a second working unit 14 provided in parallel on a base plate 12. Using the respective working units 13, 14, the press working apparatus 11 is designed to form a through hole P (see FIG. 12) with a predetermined shape (whose cross section is a generally circular shape in the present embodiment) in a sheet W, which is formed from a metallic material (e.g. hot-rolled sheet steel (JIS SPH440) for automobile structures). Namely, in the first working unit 13, as FIG. 5 shows, a region where the through hole P is to be formed is half-blanked on the sheet W, and a half-blanked portion 15 is formed having a shape that projects upward from the sheet W. In the second working unit 14, as FIG. 12 shows, the half-blanked portion 15 formed by the first working unit 13 is blanked and becomes a blanked body 15A (see FIG. 11). The through hole P is thus formed at the region where the blanked body 15A was blanked in the sheet W. At this time, the through hole P is subjected to shearing work (shaving work) such that a side wall surface (a blanked surface along the blanking direction) Pa thereof becomes a sheared surface instead of a rough fracture surface. Thereafter, the sheet W from which the blanked body 15A was blanked is further worked, and as a result, a blanked product is formed. Note that “half-blanking work” refers to the time when a blanked body (the blanked body 15A) is to be blanked from the sheet W. Such blanking is stopped partway so as to form a projection portion (the half-blanked portion 15) having a projecting shape in the sheet W.

Next, the first working unit 13 will be explained below based on FIGS. 1 to 5.

As FIG. 1 shows, in the first working unit 13, a lower die (a first lower die) 16 is disposed on the base plate 12, and a first punch 17 is fixedly attached on the lower die 16. Furthermore, a plurality (four) cylindrical columns 18 are arranged in a standing condition on the base plate 12 so as to extend in the vertical direction and run through the four corners of the lower die 16. The lower die 16 is designed to move up and down along the respective columns 18. Although not shown in the figure, the first working unit 13 is also provided with a driving source (e.g. an actuator formed from a hydraulic cylinder (a fluid pressure cylinder) and the like) for the purpose of moving the lower die 16 (and the first punch 17) between the bottom dead center position and the top dead center position in strokes.

Additionally, in the first working unit 13, an upper die (a first upper die) 19 is supported in an area over the lower die 16 by the respective columns 18, and a first die 20 that corresponds to the first punch 17 is fixedly attached to a lower surface side of the upper die 19. Furthermore, the first working unit 13 is provided with a sheet pushing portion (not shown) that pushes the sheet W upward, such that when the sheet W is carried into the first working unit 13 and subjected to press working, an upper surface Wa of the sheet W comes in contact with a lower surface 20a of the first die 20. The first die 20, as FIG. 2 shows, is formed with a first die hole (insertion hole) 21 that corresponds to a cross-sectional shape (a hole shape) of the through hole P and has a cross section with a generally circular shape. The first die hole 21 has a diameter dimension D1 (e.g. 29.9 mm) that is set so as to be slightly smaller than a diameter dimension d1 of the through hole P. Note that in the present embodiment, an inner-side edge portion 20b on the lower surface 20a side (a side facing the sheet W) of the first die 20 is not subjected to processing that would form a curved surface with a certain radius.

The first punch 17 is formed so as to have a generally cylindrical shape corresponding to the cross-sectional shape (the hole shape) of the through hole P. An end edge portion 17b on an upper surface 17a side (a side facing the sheet W) of the first punch 17 is subjected to processing so as to have a curved surface 17c with a certain radius. Therefore, by facing the first punch 17 upward and moving it, the sheet W is subjected to half-blanking work. In such case, as FIG. 5 shows, on a lower surface Wb side of the sheet W, a deformation Wc is formed whose shape has a curved surface. The curved surface 17c of the end edge portion 17b of the first punch 17 according to the present embodiment is formed into an arc shape whose curvature radius has a length dimension (e.g. 0.2 mm) that is 5% of a thickness dimension d (e.g. 4 mm) of the sheet W.

In addition, the first punch 17, as can also be understood from FIG. 2, has a diameter dimension D2 (e.g. 30.1 mm) that is set so as to be greater than the diameter dimension D1 of the first die hole (insertion hole) 21 of the first die 20. In other words, the first punch 17 and the first die 20 (the first die hole 21) are in a mutually corresponding relationship, and a clearance (a width dimension of the clearance) C1 therebetween is set so as to be a negative clearance (C1=(D1−D2)/2<0). In the present embodiment, the first punch 17 is formed such that the clearance C1 has a width dimension (e.g. 0.1 mm) that is 2.5% of the thickness dimension d (e.g. 4 mm) of the sheet W. Accordingly, the first punch 17 of the present embodiment is set such that the difference between the diameter dimension D2 of the first punch 17 and the diameter dimension D1 of the first die hole 21 is double the clearance C1 (i.e., D1−D2=2×C1).

Note that the “clearance” refers to a gap created between the punch (the first punch 17) and the die hole (the first die hole 21) when viewed from the vertical direction. If the clearance (the clearance C1) is a “negative clearance”, this indicates that the diameter (the diameter dimension D2) of the punch (the first punch 17) is greater than the diameter (the diameter dimension D1) of the die hole (the first die hole 21). Namely, the “forming a negative clearance” refers to the punch overlapping on a region of the die around the die hole as viewed from the vertical direction, and does not mean that a gap is actually created between the punch and the die hole as viewed form the vertical direction. On the other hand, if the clearance is a “positive clearance”, this indicates that the diameter of the punch is smaller than the diameter of the die hole.

Next, a first stage S1 performed by the first working unit 13 will be explained below.

A region to be blanked (a region where the through hole P is formed) on the sheet W is disposed in an area over the first punch 17. At such time, the sheet pushing portion pushes the sheet W upward (toward the first die 20 side), and puts the upper surface Wa of the sheet W in contact with the lower surface 20a of the first die 20. Next, the first punch 17 moves upward from the bottom dead center position in a stroke according to driving of the hydraulic cylinder. Thus, as FIG. 3 shows, the upper surface (an opposite surface facing the sheet W) 17a of the first punch 17 contacts the lower surface Wb of the sheet W, and such a contacted region is pressed upward by the first punch 17. As a consequence, the sheet W, as FIG. 4 shows, is formed with a half-blanked portion 15, which has a shape that projects toward the first die 20 side (upward). Accordingly, in the first working unit 13, the first punch 17 and the first die 20 are relatively moved in the vertical direction, whereby a region to be blanked in the sheet W is subjected to half-blanking work.

Here, as mentioned earlier, the clearance C1 between the first punch 17 and the first die 20 (the first die hole 21) is a negative clearance. However, in the present embodiment, the end edge portion 17b of the first punch 17 is processed so as to have an arc shape. Therefore, the pressing force applied to the first punch 17 when the first punch 17 pushing the sheet W toward the first die 20 becomes smaller compared to when the end edge portion 17b of the first punch 17 is not processed. In other words, the load applied to the first punch 17 (especially the load applied to the blade edge) is satisfactorily reduced.

Subsequently, as FIG. 5 shows, the first punch 17 moves in a stroke up to the top dead center position, and movement further upward is stopped. At this time, the upper surface 17a of the first punch 17 approaches the lower surface 20a of the first die 20 up to a position separated by a distance dimension d2, which is 35% of the thickness dimension d of the sheet W. Next, the first punch 17 moves to the bottom dead center position (see FIG. 2), after which movement is stopped. In other words, the first stage S1 in the first working unit 13 ends. Thereafter, pushing up of the sheet W by the sheet pushing portion is stopped, and the sheet W moves away from the first die 20. The sheet W is subsequently passed from the first working unit 13 into the second working unit 14. Note that a region contacting the end edge portion 17b of the first punch 17 during the stroke movement up to the top dead center position (called a “first side wall surface 15sh of the half-blanked portion 15”) is shaved by the first die 20, and therefore formed into a sheared-surface shape.

Next, the second working unit 14 will be explained below based on FIG. 1 and FIGS. 6 to 12.

As FIG. 1 shows, in the second working unit 14, a lower die (a second lower die) 22 is disposed on the base plate 12, and a second die 23 is fixed attached on the lower die 22. The second die 23, as FIG. 6 shows, is formed with a second die hole (insertion hole) 24 that corresponds to the cross-sectional shape (the hole shape) of the through hole P and has a cross section with a generally circular shape. The second die hole 24 has a diameter dimension D4 (e.g. 30.9 mm) that is set so as to be slightly greater than the diameter dimension d1 of the through hole P. Furthermore, the cylindrical columns 18 are arranged in a standing condition at the four corners of the lower die 22. An upper die (a second upper die) 25 is supported vertically mobile in an area over the lower die 22 by the columns 18. Although not shown in the figure, the second working unit 14 is also provided with a driving source (e.g. an actuator formed from a hydraulic cylinder (a fluid pressure cylinder) and the like) for the purpose of moving the upper die 25 (and a second punch 26) between the bottom dead center position and the top dead center position in strokes. Note that the driving source is provided in a manner similar to that of the first working unit 13.

A second punch 26 that has a paired relationship with the second die 23 is fixedly attached to the lower surface side of the upper die 25. Namely, in the press working apparatus 11 according to the present embodiment, the first punch 17 is fixedly attached to the lower die 16 in the first working unit 13, and therefore, the second punch 26 is fixedly attached to the upper die 25 in the second working unit 14. Furthermore, the second punch 26 is formed in a generally cylindrical shape that corresponds to the cross-sectional shape (the hole shape) of the through hole P. The second punch 26 has a diameter dimension D3 (e.g. 30.7 mm) that is set so as to be greater than the diameter dimension D2 of the first punch 17 by 0.6 mm, for example. In other words, the second punch 26 is structured so as to achieve a form wherein the cross-sectional shape for the second punch 26 when cut in a direction orthogonal to the vertical direction is a similar and enlarged version of the cross-sectional shape for the first punch 17 when cut in a direction orthogonal to the vertical direction. In addition, if the cross-sectional shape for the second punch 26 when cut in a direction orthogonal to the vertical direction overlaps in the vertical direction with the cross-sectional shape for the first punch 17 when cut in a direction orthogonal to the vertical direction, then there is a distance dimension of, for example, 0.3 mm, between adjacent outer peripheral regions with mutually similar shapes. Note that the diameter dimension D3 of the second punch 26 is set so as to enable the second punch 26 to cut (or shave in the present embodiment) a region of the sheet W on which the deformation Wc is formed.

In addition, the diameter dimension D3 of the second punch 26, as can also be understood from FIG. 6, is set so as to be smaller than the diameter dimension D4 of the second die hole 24 in the second die 23, and substantially the same dimension as the diameter dimension d1 of the through hole P. In other words, the second punch 26 and the second die 23 have a paired relationship, and a clearance (a width dimension of the clearance) C2 therebetween is set so as to be a positive clearance (C2=(D4−D3)/2>0). In the present embodiment, the second die 23 is formed such that the clearance C2 has a width dimension (e.g. 0.1 mm) that is 2.5% of the thickness dimension d (e.g. 4 mm) of the sheet W. Note that in the present embodiment, an end edge portion 26b on a lower surface 26a side (a side facing the sheet W) of the second punch 26 is not subjected to processing that would form a curved surface with a certain radius.

Next, a second stage S2 performed by the second working unit 14 will be explained below.

The sheet W on which the first working unit 13 formed the half-blanked portion 15 is passed into the second working unit 14, and the half-blanked portion 15 is disposed below the second punch 26. Following this, the second stage S2 is started. In other words, the second punch 26, as FIG. 7 shows, moves in a downward stroke toward the sheet W (the half-blanked portion 15), and presses the half-blanked portion 15 of the sheet W downward. Accordingly, a lower end side region (hereinafter referred to as a “second side wall surface 15sb of the half-blanked portion 15”) is formed into a fracture-surface shape at a connecting region between the half-blanked portion 15 and the sheet W. As the second punch 26 presses the half-blanked portion 15 further downward, as FIG. 8 shows, the first side wall surface 15sh and the second side wall surface 15sb of the half-blanked portion 15 connect, and result in the cutting of the half-blanked portion 15 from the sheet W.

Next, as FIG. 9 shows, the second punch 26 presses the half-blanked portion 15 further downward and starts to shear the sheet W. In other words, the second punch 26 blanks the half-blanked portion 15 from the sheet W and also starts to perform shaving work on a side wall surface Pa of the through hole P by blanking the half-blanked portion 15. As FIG. 10 shows, further movement of the second punch 26 in the downward stroke results in the progressive performance of shaving work on the side wall surface Pa of the through hole P.

Here, the deformation Wc still remains on the lower surface Wb side of the sheet W. Thus, even if the lower surface 26a of the second punch 26 does not move further to the lower side than the upper surface 23a of the second die 23, the blanked body 15A is still blanked from the sheet W. Thereafter, the downward stroke movement of the second punch 26 is stopped and an upward stroke movement is subsequently started, whereby the blanking of the blanked body 15a from the sheet W is completed. The side wall surface Pa of the through hole P, as FIG. 12 shows, is subjected to shaving work by the second punch 26 and thus formed into a sheared-surface shape.

In view of the above, the effects specified below can be obtained in the present embodiment.

(1) If, for instance, the clearance C1 between the first punch 17 and the first die 20 (the first die hole 21) is set as a positive clearance, then tensile stress acts on a portion of the sheet W sandwiched between the first punch 17 and the second die 20. Therefore, when the first punch 17 pushes the sheet W upward in the first working unit 13, the pushed region may fracture and form a fracture surface on the sheet W. However, in the present embodiment, the clearance C1 is a negative clearance, and therefore compression stress acting on the portion of the sheet W sandwiched between the first punch 17 and the second die 20 suppresses fractures. As a consequence, it is possible to suppress the formation of a fracture surface on the sheet W in the first working unit 13. Furthermore, in the second working unit 14, the second punch 26 performs shaving work on the side wall surface Pa of the through hole P, which is formed when the half-blanked portion 15 is blanked from the sheet W to become the blanked body 15A. Moreover, since the clearance C2 between the second punch 26 and the second die 23 is a positive clearance, it is possible to avoid contact between the second punch 26 and the second die 23. Accordingly, an increase in the size of the apparatus itself and an increase in the number of processes for performing blanking work on the sheet W can be suppressed. And at the same time, it is possible to form into a sheared-surface shape the side wall surface Pa of the through hole P that is formed in the sheet W, and also possible to suppress the generation of burrs on the sheet W.

(2) In the first working unit 13, the half-blanked portion 15 is formed at a region where the through hole P is to be formed (a region to be blanked) in the sheet W; and in the second working unit 14, the periphery of the half-blanked portion 15 is subjected to blanking work. Therefore, shaving scraps generated when the side wall surface Pa of the through hole P is subjected to shaving work in the second working unit 14 can fall along with the half-blanked portion 15 as the blanked body 15A, which is not used as a product. Moreover, adhering of the shaving scraps to the second punch 26 can be suppressed.

(3) In the first stage S1, if, for instance, the distance dimension d2 between the upper surface 17a of the first punch 17 and the lower surface 20a of the first die 20 is set to a distance dimension that is less than 10% of the thickness dimension d of the sheet W, then a problem such as the following may occur. Namely, in this case, there is a possibility that the half-blanked portion 15 may be severed from the sheet W when half-blanking work is performed on the sheet W by moving the first punch 17 in a stroke. On the other hand, if, for instance, the distance dimension d2 is set to a distance dimension that is greater than 50% of the thickness dimension d of the sheet W, then a problem such as the following may occur. Namely, in this case, the thickness of the connecting region between the sheet W and the half-blanked portion 15 is greater than that in the present embodiment. As a consequence, regardless of whether the second punch 26 presses the half-blanked portion 15 of the sheet W downward in the second stage S2, an increased load acts on the second punch 26 at the times of blanking the half-blanked portion 15 and performing shaving work on the side wall surface Pa of the through hole P. However, in the present embodiment, the distance dimension d2 is set to 35% of the thickness dimension d of the sheet W. Therefore, severing of the half-blanked portion 15 from the sheet W in the first stage S1 can be suppressed, and the load on the second punch 26 in the second stage S2 can be satisfactorily reduced.

(4) If, for instance, the clearance (the width dimension of the negative clearance) C1 is set to a width dimension that is less than 1% of the thickness dimension d of the sheet W, then there is a possibility that the deformation Wc formed on the lower surface Wb side of the sheet in the first stage S1 may become excessively large. In other words, when the half-blanked portion 15 is blanked from the sheet W in the second stage S2, there is a risk that a portion of the deformation Wc may remain on the sheet W. On the other hand, if the clearance C1 is set to a width dimension that is greater than 15% of the thickness dimension d of the sheet W, then when the first punch 17 pushes the sheet W upward, a load generated by such pushing increases the load on the first punch 17 and the first die 20. Consequently, there is a risk of shortening the lives of the first punch 17 and the first die 20. However, in the present embodiment, the clearance C1 is set to a width dimension that is 2.5% of the thickness dimension d of the sheet W. Therefore, the lives of the first punch 17 and the first die 20 can be satisfactorily lengthened. In addition, when the blanked body 15A is blanked from the sheet W in the second stage S2, the remaining of a portion of the deformation Wc on the sheet W can be suppressed.

(5) When the first punch 17 presses the sheet W upward from below in the first working unit 13, the sheet W centered around the half-blanked portion 15 may rebound toward the upward side. However, in the second working unit 14, the second punch 26 blanks (presses) the half-blanked portion 15 from the sheet W downward from above. Therefore, warping of the sheet W generated while blanking work is performed in the first working unit 13 can be satisfactorily corrected.

(6) If, for instance, the clearance (the width dimension of the positive clearance) C2 is set to a width dimension that is less than 0.3% of the thickness dimension d of the sheet W, then there is the risk of an increased load acting on the second punch 26 and the second die 23 when the half-blanked portion 15 is blanked from the sheet W by the second punch 26. In other words, there is a possibility of shortening the lives of the second punch 26 and the second die 23. On the other hand, if the clearance C2 is set to a width dimension that is greater than 8% of the thickness dimension d of the sheet W, then when the second punch 26 performs blanking work on the sheet W, burrs may be generated on the sheet W. However, in the present embodiment, the clearance C2 is set to a width dimension that is 2.5% of the thickness dimension d of the sheet W. Accordingly, the lives of the second punch 26 and the second die 23 can be lengthened, and the generation of burrs on the sheet W when the blanked body 15A is blanked from the sheet W by the second punch 26 can be satisfactorily suppressed.

(7) If, for instance, the difference between the diameter dimension D3 of the second punch 26 and the diameter dimension D2 of the first punch 17 is set shorter than 0.02 mm, then a problem such as the following may occur. Namely, the width dimension of the connecting region that connects the half-blanked portion 15 and the sheet W becomes excessively short (the width of a certain shaving amount becomes excessively narrow) compared to that in the present embodiment. Therefore, there is a risk that performing shaving work on the side wall surface Pa of the through hole P will become difficult in the second stage S2. On the other hand, if, for instance, the difference between the diameter dimension D3 of the second punch 26 and the diameter dimension D2 of the first punch 17 is set to longer than 0.6 mm, then a problem such as the following may occur. Namely, when the second punch 26 blanks the blanked body 15A from the sheet W in the second stage S2, the end edge portion 26b of the second punch 26 shears a region that is separated from the half-blanked portion 15 formed in the first stage S1, whereby the load acting on the second punch 26 increases compared to that in the case of the present embodiment. However, in the present embodiment, the second punch 26 is formed such that the difference between the diameter dimension D3 thereof and the diameter dimension D2 of the first punch 17 is 0.6 mm. Therefore, the width of a certain shaving amount in the second stage S2 can be satisfactorily ensured, and the life of the second punch 26 can be further lengthened.

(8) The end edge portion 17b of the first punch 17 is subjected to chamfering work so as to have an arc shape. Therefore, when the first punch 17 moves above the sheet W (toward the first die 20 side) in a stroke, the load acting on the first punch 17 can be satisfactorily reduced. Furthermore, the first punch 17 is also subjected to chamfering work so as to have an arc shape, and thus formed to have a certain blunt blade configuration. Therefore, in the first stage S1, the severing of a region pressed by the first punch 17 in the sheet W can be suppressed.

(9) If, for instance, when the first punch 17 is cut in the vertical direction, the curved Surface 17c of the end edge portion 17b of the first punch 17 is formed into an arc shape whose curvature radius is greater than a curvature radius with a length dimension that is 7.5% of the thickness dimension d of the sheet W, then a problem such as the following may occur. Namely, when the sheet W is subjected to blanking work in the first stage S1, there is a risk of forming an excessively large deformation Wc on the sheet W. However, in the present embodiment, the curved surface 17c of the end edge portion 17b of the first punch 17 is formed so as to have a curvature radius that is 5% of the thickness dimension d of the sheet W. Therefore, the deformation Wc formed on the sheet W can be satisfactorily suppressed so as not to become excessively large.

Second Embodiment

Next, a second embodiment according to the present invention will be explained based on FIGS. 13 to 19. Note that the second embodiment differs somewhat from the first embodiment with respect to the working units. Thus, the following explanation will mainly describe portions differing from the first embodiment; like symbols are used for members and structures that are identical to or correspond to those in the first embodiment, and redundant explanations shall be omitted.

The press working apparatus 11 according to the present embodiment has the first working unit 13 and the second working unit 14. In the first working unit 13, the first punch 17 is fixedly attached on the lower die 16, and the first die 20 corresponding to the first punch 17 is fixedly attached to the lower surface side of the upper die 19. The first punch 17 is formed into a generally cylindrical shape, and also formed such that the diameter dimension D2 thereof is 30 mm, for example.

In addition, the first die 20, as FIG. 13 shows, is formed with the first die hole 21 that has a cross section with a generally circular shape. The negative clearance C1 between the first die 20 and the first punch 17 is set so as to have a width dimension (e.g. 0.15 mm) that is 3.8% of the thickness dimension d (e.g. 4 mm) of the sheet W. Namely, the first die hole 21 of the first die 20 is set such that the diameter dimension D1 thereof is 29.7 mm, for example. Furthermore, the inner-side edge portion 20b on the lower surface 20a side (a side facing the sheet W) of the first die 20 is subjected to processing so as to have a curved surface 20c with a certain radius. In the present embodiment, when the first die 20 is cut in the vertical direction, the curved surface 20c of the inner-side edge portion 20b of the first die 20 is formed so as to have an arc shape whose curvature radius has a length dimension (e.g. 0.3 mm) that is 7.5% of the thickness dimension d (e.g. 4 mm) of the sheet W.

Next, the first stage S1 performed by the first working unit 13 will be explained below.

A region to be blanked on the sheet W is disposed in an area over the first punch 17. At such time, the sheet pushing portion pushes the sheet W upward (toward the first die 20 side), and puts the upper surface Wa of the sheet W in contact with the lower surface 20a of the first die 20. Next, the first punch 17 moves upward from the bottom dead center position in a stroke according to driving of the hydraulic cylinder. Thus, the upper surface (an opposite surface facing the sheet W) 17a of the first punch 17 contacts the lower surface Wb of the sheet W, and such a contacted region is pressed upward by the first punch 17. As a consequence, the sheet W is formed with the half-blanked portion 15, which has a shape that projects toward the first die 20 side (upward). Accordingly, in the first working unit 13, the first punch 17 and the first die 20 are relatively moved in the vertical direction, whereby a region at which the blanked body 15A is to be blanked in the sheet W is subjected to half-blanking work.

Subsequently, the first punch 17 moves in a stroke up to the top dead center position, and movement further upward is stopped. At this time, the upper surface 17a of the first punch 17 approaches the lower surface 20a of the first die 20 up to a position separated by a distance dimension, which is 45% of the thickness dimension d of the sheet W. Next, the first punch 17 moves to the bottom dead center position, after which movement is stopped. In other words, the first stage S1 in the first working unit 13 ends. Thereafter, pushing up of the sheet W by the sheet pushing portion is stopped, and the sheet W moves away from the first die 20. The sheet W is subsequently passed from the first working unit 13 into the second working unit 14. Note that the half-blanked portion 15 in the present embodiment is subjected to processing to achieve a certain radius by the inner-side edge portion 20b of the first die 20, and is therefore formed such that the deformation 15b on the upper surface Wa side thereof is larger than that in the case of the first embodiment. In addition, the first side wall surface 15sh of the half-blanked portion 15 formed by the first working unit is shaved by the first die 20, similar to the case of the first embodiment, and therefore formed into a sheared-surface shape.

Next, the second working unit 14 will be explained below based on FIGS. 14 to 19.

In the second working unit 14, the second die 23 is fixedly attached on the lower die 22, and the second punch 26, which has a paired relationship with the second die 23, is fixedly attached to the lower surface side of the upper die 25. The second die 23, as FIG. 14 shows, is formed with the second die hole 24 that has a cross section with a generally circular shape. The second die hole 24 has the diameter dimension D4 (e.g. 29.3 mm) that is set so as to be greater than the diameter dimension D1 of the first die hole 21 in the first die 20 by 0.4 mm, for example. In addition, the diameter dimension D4 of the second die hole 24 is set so as to be slightly smaller than the diameter dimension d1 of the through hole P, and also set so as to be substantially the same dimension as the diameter d3 of the blanked body 15A (see FIG. 19) to be described later.

The second punch 26 is formed so as to have a generally cylindrical shape. The second punch 26 is structured so as to achieve a form wherein the cross-sectional shape for the second punch 26 when cut in a direction orthogonal to the vertical direction is a similar and scaled-down version of the cross-sectional shape for the first punch 17 when cut in a direction orthogonal to the vertical direction. In addition, the diameter dimension D3 of the second punch 26 is set so as to enable cutting (or shaving in the present embodiment) of a region where a deformation Wd is formed on the sheet W, and also set so as to be shorter than the diameter dimension of the second die hole 24 by 0.2 mm, for example. In other words, the second punch 26 and the second die 23 have a paired relationship, and the clearance (a width dimension of the clearance) C2 therebetween is set so as to be a positive clearance (C2=(D4−D3)/2>0). In the present embodiment, the second die 23 is formed such that the clearance C2 has a width dimension (e.g. 0.1 mm) that is 2.5% of the thickness dimension d (e.g. 4 mm) of the sheet W.

Next, the second stage S2 performed by the second working unit 14 will be explained below.

The sheet W on which the first working unit 13 formed the half-blanked portion 15 is passed into the second working unit 14, and the half-blanked portion 15 is disposed below the second punch 26. Following this, the second stage S2 is started. In other words, the second punch 26, as FIG. 15 shows, moves in a downward stroke toward the sheet W (the half-blanked portion 15), and presses the half-blanked portion 15 of the sheet W downward. At this time, the end edge portion 26b of the second punch 26 positionally corresponds to an edge portion (a deformation on the upper side) that forms the cross-sectional arc shape of the half-blanked portion 15 of the sheet W. Accordingly, the second side wall surface 15sb of the half-blanked portion 15 is formed into a fracture-surface shape, similar to the case of the first embodiment. As the second punch 26 presses the half-blanked portion 15 further downward, as FIG. 16 shows, the first side wall surface 15sh and the second side wall surface 15sb of the half-blanked portion 15 connect, and result in the cutting of the half-blanked portion 15 from the sheet W.

Next, as FIG. 17 shows, the second punch 26 presses the half-blanked portion 15 further downward and the second die 23 starts to shear the side wall surface (the blanked surface) 15a of the half-blanked portion 15 (a region to become the blanked body 15A). In other words, the second die 23 blanks the half-blanked portion 15 that is pushed downward by the second punch 26 from the sheet W, and starts to perform shaving work on the side wall surface 15a of the half-blanked portion 15. As FIG. 18 shows, further movement of the second punch 26 in the downward stroke results in the progressive performance of shaving work on the side wall surface 15a of the half-blanked portion 15.

At this point in time, the half-blanked portion 15 is still in a fitted state inside the through hole P of the sheet W. However, with the further performance of shaving work on the side wall surface Pa by the second die 23, as FIG. 19 shows, the half-blanked portion 15 is pushed out of the through hole P by the second punch 26 and blanked from the sheet W to become the blanked body 15A. A majority of the side wall surface 15a of the blanked body 15A is formed into a sheared-surface shape due to shaving work performed by the second die 23. Note that a portion among the side wall surface 15a of the blanked body 15A that is not formed into a sheared-surface shape is a region of the half-blanked portion 15 (the blanked body 15A) that will ultimately be cut from the sheet W by pressure from the second punch 26, and is formed into a fracture-surface shape. In addition, scraps (shaving scraps) generated due to the second die 23 performing shaving work on the side wall surface 15a adhere to the sheet W. Therefore, the side wall surface Pa is formed into a fracture-surface shape.

In addition to the effects (3) to (5), (8), and (9) of the first embodiment, the further effects specified below can be obtained in the present embodiment.

(10) If, for instance, the clearance C1 between the first punch 17 and the first die 20 (the first die hole 21) is set as a positive clearance, then tensile stress acts on a portion of the sheet W sandwiched between the first punch 17 and the second die 20. Therefore, when the first punch 17 pushes the sheet W upward in the first working unit 13, the pushed region may fracture and form a fracture surface on the sheet W. However, in the present embodiment, the clearance C1 is a negative clearance, and therefore compression stress acting on the portion of the sheet W sandwiched between the first punch 17 and the second die 20 suppresses fractures. As a consequence, it is possible to suppress the formation of a fracture surface on the sheet W in the first working unit 13. Furthermore, in the second working unit 14, when the sheet W is subjected to blanking work, the second die 23 performs shaving work on the side wall surface 15a of the half-blanked portion 15 (the blanked body 15A). Moreover, since the clearance C2 between the second punch 26 and the second die 23 is a positive clearance, it is possible to avoid contact between the second punch 26 and the second die 23. Accordingly, an increase in the size of the apparatus itself and an increase in the number of processes for performing blanking work on the sheet W can be suppressed. And at the same time, it is possible to form into a sheared-surface shape the side wall surface 15a of the blanked body 15A blanked from the sheet W, and also possible to suppress the generation of burrs on the blanked body 15A.

(11) In the first working unit 13, the half-blanked portion 15 is formed at a region where the through hole P is to be formed (a region to be blanked) in the sheet W; and in the second working unit 14, the periphery of the half-blanked portion 15 is subjected to blanking work. Therefore, shaving scraps generated when the side wall surface 15a of the blanked body 15A is subjected to shaving work in the second working unit 14 can be made to adhere to the sheet W, which is not used as a product. Moreover, adhering of the shaving scraps to the second punch 26 can be suppressed.

(12) If, for instance, the clearance (the width dimension of the positive clearance) C2 is set to a width dimension that is less than 0.3% of the thickness dimension d of the sheet W, then there is the risk of an increased load acting on the second punch 26 and the second die 23 when the half-blanked portion 15 is blanked from the sheet W by the second punch 26. In other words, there is a possibility of shortening the lives of the second punch 26 and the second die 23. On the other hand, if the clearance C2 is set to a width dimension that is greater than 8.0% of the thickness dimension d of the sheet W, then when the second punch 26 and the second die 23 punch the blanked body 15A from the sheet W, burrs may be generated on the blanked body 15A. However, in the present embodiment, the clearance C2 is set to a width dimension that is 2.5% of the thickness dimension d of the sheet W. Accordingly, the lives of the second punch 26 and the second die 23 can be lengthened, and the generation of burrs on the blanked body 15A when the blanked body 15A is blanked from the sheet W by the second punch 26 and the second die 23 can be satisfactorily suppressed.

(13) If, for instance, the difference between the diameter dimension D4 of the second die hole 24 of the second die 23 and the diameter dimension D1 of the first die hole 21 of the first die 20 is set shorter than 0.02 mm, then a problem such as the following may occur. Namely, the width dimension of the connecting region that connects the half-blanked portion 15 and the sheet W becomes excessively small (the width of a certain shaving amount becomes excessively narrow) compared to that in the present embodiment. Therefore, there is a risk that performing shaving work on the side wall surface 15a of the blanked body 15A will become difficult in the second stage S2. On the other hand, if the difference between the diameter dimension D4 of the second die hole 24 of the second die 23 and the diameter dimension D1 of the first die hole 21 of the first die 20 is set greater than 0.6 mm, then a problem such as the following may occur. Namely, when the second punch 26 and the second die 23 punch the blanked body 15A from the sheet W in the second stage S2, the inner-side edge portion of the second die 23 shears a region on the inner peripheral side of the half-blanked portion 15 formed in the first stage S1, whereby the load acting on the second die 23 increases compared to that in the case of the present embodiment. However, in the present embodiment, the second die 23 is formed such that the difference between the diameter dimension D4 of the second die hole 24 thereof and the diameter dimension D1 of the first die hole 21 of the first die 20 is 0.4 mm. Therefore, the width of a certain shaving amount in the second stage S2 can be satisfactorily ensured, and the life of the second die 23 can be further lengthened.

(14) If, for instance, when the first die 20 is cut in the vertical direction, the curved surface 20c of the inner-side edge portion 20b of the first die 20 is formed into an arc shape whose curvature radius is greater than a curvature radius with a length dimension that is 7.5% of the thickness dimension d of the sheet W, then a problem such as the following may occur. Namely, when the sheet W is subjected to half-blanking work in the first stage S1, there is a risk of forming an excessively large deformation on the upper side of the sheet W. However, in the present embodiment, the curved surface 17c of the end edge portion 17b of the first punch 17 is formed so as to have a curvature radius that is 7.5% of the thickness dimension d of the sheet W. Therefore, the deformation Wc formed on the sheet W can be satisfactorily suppressed so as not to become excessively large.

Third Embodiment

Next, a third embodiment according to the present invention will be explained based on FIG. 20. Note that the third embodiment differs somewhat from the first embodiment with respect to the working units. Thus, the following explanation will mainly describe portions differing from the first embodiment; like symbols are used for members and structures that are identical to or correspond to those in the first embodiment, and redundant explanations shall be omitted.

The press working apparatus 11 according to the present embodiment has the first working unit 13 and the second working unit 14. The press working apparatus 11 is designed to form the through hole P with a predetermined shape (whose cross section is a generally circular shape in the present embodiment) in the sheet W, which is formed from a metallic material (e.g. hot-rolled sheet steel (JIS SAPH370) for automobile structures) with a predetermined thickness (e.g. 3 mm). In the first working unit 13, the first punch 17 is fixedly attached on the lower die 16, and the first die 20 corresponding to the first punch 17 is fixedly attached on the lower surface side of the upper die 19. The first punch 17 is formed so as to have a generally cylindrical shape, and also formed such that the diameter dimension D2 thereof is 20.2 mm, for example.

In addition, the first die 20 is formed with the first die hole 21 that has a cross section with a generally circular shape. The negative clearance C1 between the first die 20 and the first punch 17 is set so as to have a width dimension (e.g. 0.3 mm) that is 10% of the thickness dimension d (e.g. 3 mm) of the sheet W. Namely, the first die hole 21 of the first die 20 is set such that the diameter dimension D1 thereof is 19.6 mm, for example. Note that in the present embodiment, the end edge portion 17b on the upper surface 17a side (a side facing the sheet W) of the first punch 17 and the inner-side edge portion 20b on the lower surface 20a side (a side facing the sheet W) of the first die 20 are not subjected to processing that would form curved surfaces thereon with a certain radius.

Next, the first stage S1 performed by the first working unit 13 will be explained below.

A region to be blanked on the sheet W is disposed in an area over the first punch 17. At such time, the sheet pushing portion pushes the sheet W upward (toward the first die 20 side), and puts the upper surface Wa of the sheet W in contact with the lower surface 20a of the first die 20. Next, the first punch 17 moves upward from the bottom dead center position in a stroke according to driving of the hydraulic cylinder. Thus, the sheet W is formed with the half-blanked portion 15, which has a shape that projects toward the first die 20 side (upward). Accordingly, in the first working unit 13, the first punch 17 and the first die 20 are relatively moved in the vertical direction, whereby a region at which the blanked body 15A is to be blanked in the sheet W is subjected to half-blanking work. Furthermore, at this time, a region of the sheet W in contact with the end edge portion 17b of the first punch 17 is formed into a sheared-surface shape as a result of shaving work performed by the first punch 17.

Next, the second working unit 14 will be explained below.

The second punch 26 is formed so as to have a generally cylindrical shape. The second punch 26 is structured so as to achieve a form wherein the cross-sectional shape for the second punch 26 when cut in a direction orthogonal to the vertical direction is a similar and enlarged version of the cross-sectional shape for the first punch 17 when cut in a direction orthogonal to the vertical direction. In addition, the second punch 26 is formed such that the diameter dimension D3 thereof is set greater than the diameter dimension D1 of the first die hole 21 of the first die 20 by 0.5 mm. In other words, the diameter dimension D3 of the second punch 26 is set so as to be 20.1 mm, for example. Therefore, the diameter dimension D3 of the second punch 26 is shorter than the diameter dimension D4 of the second die hole 24 by 0.4 mm, for example. Accordingly, the second punch 26 and the second die 23 have a paired relationship, and the clearance (a width dimension of the clearance) C2 formed therebetween is set so as to be a positive clearance (C2=(D4−D3)/2>0). In the present embodiment, the second die 23 is formed such that the clearance C2 has a width dimension (e.g. 0.2 mm) that is 6.7% of the thickness dimension d (e.g. 3 mm) of the sheet W.

Next, the second stage S2 performed by the second working unit 14 will be explained below.

The sheet W on which the first working unit 13 formed the half-blanked portion 15 is passed into the second working unit 14, and the half-blanked portion 15 is disposed below the second punch 26. Following this, the second stage S2 is started. In other words, the second punch 26 moves in a downward stroke toward the sheet W (the half-blanked portion 15), and presses the half-blanked portion 15 of the sheet W downward. Accordingly, the second side wall surface 15sb of the half-blanked portion 15 is formed into a fracture-surface shape. As the second punch 26 presses the half-blanked portion 15 further downward, the first side wall surface 15sh and the second side wall surface 15sb of the half-blanked portion 15 connect, and result in the cutting of the half-blanked portion 15 from the sheet W.

Next, the second punch 26 presses the half-blanked portion 15 further downward, whereby the second punch 26 starts to perform shaving work on the side wall surface Pa of the through hole P. In this case, the diameter dimension D3 of the second punch 26 is smaller than the diameter dimension D3 of the first punch 17 by 0.1 mm. Therefore, as FIG. 20 shows, a region (an upper-side region in FIG. 20) P1 sheared by the second punch 26 is formed such that a diameter dimension thereof (e.g. 20.1 mm) is smaller than a diameter dimension (e.g. 20.2 mm) of a region (a lower-side region in FIG. 20) P2 sheared by the first punch 17. Thus, the through hole P formed in the sheet W by the press working apparatus 11 according to the present embodiment is formed with the upper-side region P1 and the lower-side region P2, which has a diameter dimension that is greater than the diameter dimension of the upper-side region P1.

In addition to the effects (1) to (5), (8), and (9) of the first embodiment, the further effect specified below can be obtained in the present embodiment.

(15) If, for instance, the difference between the diameter dimension D3 of the second punch 26 and the diameter dimension D1 of the first die hole 21 of the first die 20 is set smaller than 0.02 mm, then a problem such as the following may occur. Namely, the width dimension of the connecting region that connects the half-blanked portion 15 and the sheet W becomes excessively small (the width of a certain shaving amount becomes excessively narrow) compared to that in the present embodiment. Therefore, there is a risk that performing shaving work on the side wall surface Pa of the upper-side region P1 of the through hole P will become difficult in the second stage S2. On the other hand, if the difference between the diameter dimension D3 of the second punch 26 and the diameter dimension D1 of the first die hole 21 of the first die 20 is set greater than 0.6 mm, then a problem such as the following may occur. Namely, when the second punch 26 and the second die 23 punch the blanked body 15A from the sheet W in the second stage S2, the load acting on the end edge portion 26b of the second punch 26 increases. However, in the present embodiment, the second punch 26 is formed such that the difference between the diameter dimension D4 thereof and the diameter dimension D1 of the first die hole 21 of the first die 20 is 0.5 mm. Therefore, the width of a certain shaving amount in the second stage S2 can be satisfactorily ensured, and the life of the second punch 26 can be further lengthened.

Note that the respective embodiments above may be modified to achieve other embodiments (other examples) such as the following.

In the first embodiment, provided that the curvature radius of the curved surface 17c is a curvature radius that is equal to or less than 7.5% of the thickness dimension d of the sheet W, the end edge portion 17b of the first punch 17 may be formed such that the curved surface 17c has an arbitrary curvature radius (e.g. a curvature radius that is 1.5% of the thickness dimension d).

In the first embodiment, the inner-side edge portion 20b of the first die 20 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 10% of the thickness dimension d). In addition, the end edge portion 26b of the second punch 26 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 5% of the thickness dimension d).

In the second embodiment, provided that the curvature radius of the curved surface 20c is a curvature radius that is equal to or less than 7.5% of the thickness dimension d of the sheet W, the inner-side edge portion 20b of the first die 20 may be formed such that the curved surface 20c has an arbitrary radius (e.g. a curvature radius that is 6% of the thickness dimension d).

In the second embodiment, the end edge portion 17b of the first punch 17 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 5% of the thickness dimension d). In addition, the end edge portion 26b of the second punch 26 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 5% of the thickness dimension d).

In the third embodiment, the end edge portion 17b of the first punch 17 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 5% of the thickness dimension d). In addition, the inner-side edge portion 20b of the first die 20 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 10% of the thickness dimension d). Furthermore, the end edge portion 26b of the second punch 26 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 5% of the thickness dimension d). Moreover, the end edge portion 26b of the second punch 26 may be formed such that the shape of a vertical cross section thereof forms a part of the circular shape of an arbitrary diameter dimension that is equal to or less than a diameter dimension that is 15.0% of the thickness dimension d of the sheet W (e.g. a diameter dimension that is 5% of the thickness dimension d).

In the first embodiment, provided that the difference between the diameter dimension D3 of the second punch 26 and the diameter dimension D2 of the first punch 17 is within a range of 0.02 mm to 0.6 mm, the second punch 26 may be formed such that the difference between the diameter dimension D3 and the diameter dimension D2 is an arbitrary diameter dimension (e.g. 0.1 mm).

In the first embodiment, the first punch 17 and the second punch 26 may be respectively structured such that the shapes of the respective cross sections, when cut in a direction orthogonal to the vertical direction, are arbitrary cross-sectional shapes that correspond to the cross-sectional shape (the hole shape) of the through hole P formed in the sheet W. However, the cross-sectional shape of the second punch 26 is preferably a shape that is a generally similar and enlarged version of the cross-sectional shape of the first punch 17.

In other words, the first punch 17 and the second punch 26 may respectively have cross-sectional shapes that are formed as generally square shapes. Here, as FIG. 21 shows, a cross section (hereinafter referred to as a “first punch cross section”) 17A of the first punch 17 is superimposed in a frame format in the vertical direction on a cross section (hereinafter referred to as a “second punch cross section”) 26A of the second punch 26. In such case, a distance dimension da between adjacent outer peripheral regions 17d, 26d that have mutually similar shapes may be set to an arbitrary distance dimension (e.g. 0.15 mm), provided that the distance dimension is within a range of 0.01 mm to 0.3 mm. In this case, the distance dimension da is, respectively, the distance dimension between a top side of the first punch cross section 17A and a top side of the second punch cross section 26A; and the distance dimension between the right side of the first punch cross section 17A and the second punch cross section 26A. Likewise, the distance dimension da also is, respectively, the distance dimension between the bottom side of the first punch cross section 17A and the bottom side of the second punch cross section 26A; and the distance dimension between the left side of the first punch cross section 17A and the left side of the second punch cross section 26A. Note that the top, bottom, left, and right as used here refer to the top, bottom, left, and right as shown in FIG. 21.

Also, the press working apparatus 11 according to the first embodiment, as FIGS. 22 and 23 show, may be used along with other processing devices (such as a press working apparatus having a punch and a die that differ in shape and size from the punches 17, 26 and the dies 20, 23) to form a carrier 40. Note that the carrier 40 is a type of press-formed part for an automatic transmission.

Also, in the second embodiment as well, the first punch 17 and the second punch 26 may be respectively structured such that the shapes of the respective cross sections, when cut in a direction orthogonal to the vertical direction, are arbitrary cross-sectional shapes (e.g. cross sections with polygonal shapes) that correspond to the cross-sectional shape (the hole shape) of the through hole P formed in the sheet W. In other words, the press working apparatus 11 according to the second embodiment, as FIG. 24 shows, may be used to form a backing plate 36 that is formed with a plurality of projections 35 on an outer-side surface (a side wall surface 15A) side thereof. In this case, the hole shape of the second die hole 24 of the second die 23 is preferably a shape that is a generally similar and scaled-down version of the hole shape of the first die hole 21 of the first die 20.

- Furthermore, in the third embodiment as well, the first punch 17 and the second punch 26 may be respectively structured such that the shapes of the respective cross sections, when cut in a direction orthogonal to the vertical direction, are arbitrary cross-sectional shapes (e.g. cross sections with polygonal shapes) that correspond to the cross-sectional shape (the hole shape) of the through hole P formed in the sheet W. In this case, the cross-sectional shape of the second punch 26 is preferably a shape that is a generally similar and enlarged version of the hole shape of the first die hole 21 of the first die 20.

In the respective embodiments above, provided that the width dimension is within a range of 0.3% to 8% of the thickness dimension d of the sheet W, the second punch 26 may be formed such that the clearance C2 has an arbitrary width dimension (e.g. a width dimension that is 1% of the thickness dimension d).

In the respective embodiments above, provided that the width dimension is within a range of 1% to 15% of the thickness dimension d of the sheet W, the first punch 17 may be formed such that the clearance C 1 has an arbitrary width dimension (e.g. a width dimension that is 3.0% of the thickness dimension d).

In the second embodiment, the second die 23 may be structured such that the distance dimension between an inner peripheral region of the cross section of the second die 23 and an inner peripheral region of the cross section of the first die 20 is an arbitrary distance dimension (e.g. 3 mm) within a range of 0.01 mm to 0.3 mm. For such a structure, in the second working unit 14, the second die 23 shears only a portion of the side wall surface 15a of the blanked body 15A. Namely, the blanked body 15A has a major diameter portion whose diameter dimension is large and a minor diameter portion whose diameter dimension is smaller than the major diameter portion, which are provided connected in the vertical direction.

In the respective embodiments above, when the sheet W is half-blanked in the first working unit 13, the distance dimension d2 in the vertical direction between the upper surface 17a of the first punch 17 and the lower surface 20a of the first die 20 may be set to an arbitrary distance dimension, provided that the distance dimension is within a range of 10% to 50% of the thickness dimension d. For example, the distance dimension d2 may be set to a distance dimension that is 40% of the thickness dimension d.

In the first embodiment, as FIGS. 25A, 25B, and 25C show, the press working apparatus 11 may be realized by a press working apparatus that forms a notched portion 31 on a sheet 30. Namely, in the first stage S1, a half-blanked portion 32 is formed at a region formed with the notched portion 31 in the sheet 30. Then, in the second stage S2, the half-blanked portion 32 of the sheet 30 is subjected to blanking work, and a side wall surface 31a of the notched portion 31 is subjected to shaving work. As a consequence, the sheet 30 is formed with the notched portion 31 having the side wall surface 31a, which has been processed into a sheared-surface shape.

In the respective embodiments above, the press working apparatus 11 may have a structure in which the first punch 17 is fixedly attached to the lower surface side of the upper die 19 in the first working unit 13, and the second punch 26 is fixedly attached to the upper surface side of the lower die 22 in the second working unit 14. For such a case, in the first stage S1, as FIG. 25A shows, the half-blanked portion 32 is formed having a shape that projects downward from the sheet 30.

In the respective embodiments above, the press working apparatus 11 may have a structure in which the first punch 17 is fixedly attached to the lower surface side of the upper die 19 in the first working unit 13, and the second punch 26 is fixedly attached to the lower surface side of the upper die 25 in the second working unit 14. In the case of such a structure, the sheet 30 formed with the half-blanked portion 32 by the first stage S1 of the first working unit 13 may be turned over such that a concave portion of the half-blanked portion 32 faces upward, after which the sheet 30 is passed into the second working unit 14.

In the respective embodiments above, the press working apparatus 11 may be realized as an apparatus that forms an arbitrary press-formed part, provided that it is a press-formed part for an automatic transmission. In addition, the press working apparatus 11 may be realized as an apparatus that forms an element of a belt for a continuously variable transmission. Namely, the press working apparatus 11 may be an apparatus that forms an arbitrary press-formed part, provided that it is a part that has a relative thickness and is not a thin plate.

Pressing Machine, Pressing Method, and Punched Article

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