WO2019132000A1

WO2019132000A1 - Method for press forming annular part

Info

Publication number: WO2019132000A1
Application number: PCT/JP2018/048447
Authority: WO
Inventors: 智行望月; 正道三輪; 俊之市川; 正明大庭; 正英前島; 加田　修; 伸麻吉川
Original assignee: ユニプレス株式会社; 日本製鉄株式会社
Priority date: 2017-12-28
Filing date: 2018-12-28
Publication date: 2019-07-04
Also published as: JPWO2019132000A1; JP7230828B2

Abstract

The present invention relates to a method for press forming an annular part having a boss of a T cross-sectional shape, and it is a purpose of the present invention to reduce the material cost and to shorten the production tact by forming by pressing from a single steel plate. While holding a disk-shaped work W made of a single steel plate and having a central hole under a die cushion, the central hole of the work W is burred with a punch to form one side of the work into a cylindrical overhang portion. First-stage ironing is performed by ironing the overhang portion with a punch, while holding the work W after burring under the die cushion, and thickening toward the root W3 of the overhang portion W₂ after ironing. Then, the overhang portion W2 after ironing is further ironed with a punch 65, while holding the work under the die cushion, thereby forming a second overhang portion W₅ on the opposite side of the work and obtaining a carrier part having a boss portion of a T-shaped cross section.

Description

Method of press forming annular parts

The present invention relates to a method of press forming an annular part such as a carrier base of an automobile transmission.

In a torque converter type automobile transmission, an automobile transmission using a planetary gear is used. The planetary gear is provided with a plurality of pinions, a sun gear and a ring gear meshing with inner and outer circumferences of the plurality of pinions, and the plurality of pinions are carrier parts that rotatably support the carrier (carrier, carrier base ) Is provided. As is well known, the shifting operation by the planetary gear brakes one of the three rotating elements of the carrier, the sun gear and the ring gear, and one rotating element of the remaining two rotating elements on the input side and the other rotating It is done by connecting the elements to the output side. The carrier is rotatably attached to a support such as a housing, but the support of the carrier's planetary gear is in a plate shape, and a boss is formed for attachment to the support such as a housing In many cases, the bosses may extend on both sides from the plate-like attachment for the planet gears.

It is essential to reduce the weight as a rotating part for an automobile transmission including the carrier, and the weight reduction can be realized by using a sintered part. Although unification of plate-like part and boss part is not directly disclosed, there is patent document 1 about a carrier part by sintering. Further, in order to reduce the weight by forming a pressed product from a steel plate, there has been proposed one in which separate bosses are integrated by welding or a special fitting structure (Patent Document 2).
Moreover, in connection with this invention, there exists patent document 3 about the press-forming of the cylindrical part by the burring from the steel plate of 1 sheet, and subsequent ironing. Moreover, there is patent document 4 about the structure of the carrier base in the motor vehicle transmission provided with the torque converter as embodiment of this invention.

Japanese Patent Application Laid-Open No. 7-208585 JP-A-7-290185 JP-A-11-138219 JP 2009-85389

In the case of a sintered product (Patent Document 1), the production tact becomes long, and the cost increases. Moreover, in the case of the welding or fitting structure of two parts (patent document 2), it also becomes complicated as a process, and this causes an increase in cost. In view of such problems, the present invention is to reduce the material cost and realize the shortening of the production tact by forming an annular part in an automobile transmission such as a carrier by pressing from a single steel plate. To aim.

It is a press-formed product formed from a single steel plate according to the present invention, and is a disc portion, and an overhang portion located on the outer diameter side or the inner diameter side with respect to the disc portion and overhanging on both sides in the axial direction The press-forming method of an annular part having a substantially T-shaped cross-section at the connecting portion between the disc portion and the projecting portion is as follows.
Forming one side of the work into a cylindrical first overhang by performing burring on a disc-shaped work consisting of a single steel plate on the inner or outer diameter side;
While holding the work up and down, the first overhanging portion is ironed, and the flow of the meat at that time causes the annular portion to form the second overhanging portion in the direction opposite to the first overhanging portion with respect to the work holding portion. It consists of a part and an ironing process,
The above-mentioned drawing process is
At least the first overhanging portion while holding the work up and down while holding the work up and down while holding the work up and down in the first stage of drawing the meat toward the base side of the first overhanging portion by squeezing the inner diameter of the first overhanging portion It consists of at least two stages of ironing with a second stage of ironing at the side to which the meat is added. By applying the necessary post-processing such as cutting to the annular part, it can be made a carrier part in an automobile transmission.

During the first stage ironing process and the second stage ironing process, ironing is performed over the entire length of the first overhang obtained by burring using a cylindrical punch and die of uniform diameter. As a result, it is possible to form a tubular part provided with tubular parts on both sides of the plate part.

As another embodiment, in the first stage ironing, ironing is performed over the entire length of the first overhang obtained by burring using a cylindrical punch and die of uniform diameter, and the second stage In the ironing process, using a stepped cylindrical die and a punch, while constraining the end of the first overhang obtained by the first stage ironing, the restraint of the first overhang is performed. Further ironing of the first overhanging portion can be performed at a site separated from the end, and the opposite side can be formed into a second tubular portion.

According to the present invention, it is possible to manufacture an annular part having cylindrical parts on both sides by only pressing using burring from a single steel plate and multistage ironing, and thus achieving weight reduction. The material cost is reduced and the production tact is shortened, thereby achieving a large cost reduction as a total.
Moreover, there is no structural defect by the combined use of burring and multi-step ironing, and high rigidity can be ensured even in the T cross-sectional shape part, and in particular, when annular parts are adopted for automobile parts such as carriers Even in the case where an axial force input portion is used as a part, the high rigidity makes it advantageous in terms of strength as compared with a separate structure such as a welding or fitting method.

FIG. 1 is a cross-sectional view, at one side of a central axis, of a relevant portion of an automobile transmission provided with a carrier base in which the tubular part of the present invention is used. FIG. 2 is a schematic cross-sectional view showing the steps from (A) to (D) of the press-forming process of the first embodiment of the tubular part for the carrier base of FIG. FIG. 3 is a schematic cross-sectional view showing the steps (E) to (G) following the step of FIG. FIG. 4 is a schematic cross-sectional view showing main three steps (1) (2) (3) of the second embodiment of the present invention. FIG. 5 is a schematic sectional view showing main three steps (1) (2) (3) of the third embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing main three steps (1) (2) (3) of the fourth embodiment of the present invention.

An automobile transmission provided with a carrier base as an embodiment of the annular part of the present invention will be described below. FIG. 1 is a schematic cross-sectional view showing an example of the arrangement of the carrier base in the automobile transmission. Represented by M. This automobile transmission is structurally similar to that described in Patent Document 4, and the carrier base 10 is employed in the third-stage transmission mechanism of the transmission mechanism having a three-stage configuration. According to the present invention, the carrier base 10 is a press-formed product from a single steel plate, and the annular plate portion 12 and a boss portion extending on both sides in the axial direction of the annular plate portion 12 at the inner peripheral portion of the annular plate portion 12 The cross-sectional shape of the connecting portion between the annular plate portion 12 and the boss portion 14 is T-shaped. As will be described later, in this embodiment, the boss portion 14 press-molds a first cylindrical overhang portion extending to one side in the axial direction by burring a material steel plate, and the inner portion with respect to the first cylindrical overhang portion. It is obtained by press-forming a second cylindrical overhanging portion extending to the opposite side by winding the periphery, and thereafter performing finish processing such as cutting, and the boss portion 14 is an integral press for the annular plate portion 12 It becomes a forming part. The boss 14 of the carrier base 10 is rotatably attached to the boss 22-1 of the cover 22.

In addition to the carrier base 10, the transmission mechanism shown in FIG. 1 meshes with the pinion 16 and the pinion 16 provided on the inner diameter side with the pinion 16, which is circumferentially separated from the carrier base 10 so as to be rotatable about the respective rotation shafts 15. And a ring gear 20 meshing with the pinion 16 on the outer diameter side, thereby forming a planetary gear mechanism consisting of three rotating elements, which is accommodated in the transmission cover 22. The sun gear 18 is connected to the input shaft 24 from the engine side. The input shaft 24 is rotatable relative to the transmission cover 22. Reference numeral 28 denotes a clutch drum, and the ring gear 20 is formed on the inner peripheral portion of the plate-like portion clutch drum 28. The clutch drum 28 is provided with a disc-shaped portion 28-1 and a bearing 29 is disposed between the disc-shaped portion 28-1 of the clutch drum 28 and the transmission cover 22. Although the brake 30 is shown in a simplified manner, it has a drive plate 32 and a driven plate 34 in the shape of an annular disk, and as is known, the drive plate 32 has teeth at equal intervals in the circumferential direction on the inner periphery. The drive plate 32 is rotated in the rotational direction by engaging the groove portions 28-1 axially extending on the outer periphery of the clutch drum 28 and equally spaced in the circumferential direction. It is integral with the drum 28 but is slidable in the longitudinal direction. As is well known, the driven plate 34 has teeth at equal intervals in the circumferential direction on the outer periphery, and the teeth extend in the axial direction on the inner periphery of the transmission cover 22, respectively in the circumferential direction, etc. The driven plate 34 is integral with the transmission cover 22 in the rotational direction, but is slidable in the longitudinal direction by engaging the groove 22-2 spaced apart from the space. The annular piston 36 is provided in the annular recess 22-3 of the transmission cover 22, and the left-handed position in FIG. 1 is normally taken by the annular

elastic members

38A and 38B on the inner and outer peripheries. Smooth rotation can be performed by the oil film between them. By introducing the hydraulic pressure into the recess 22-3, the annular piston 36 is moved to the right against the elastic force of the

elastic members

38A and 38B, and the drive plate 32 and the driven plate 34 are engaged. Be done. Therefore, the clutch drum 28 is braked by the transmission cover 22. The pinion 16 of the planetary gear mechanism is connected by a carrier plate 37 to an output shaft (not shown), that is, the wheel side.

In Patent Document 1, in addition to the planetary gear type transmission mechanism of FIG. 1, a transmission mechanism using another planetary gear is provided, and a brake or a clutch different from the brake 30 is provided to engage each brake or clutch Alternatively, the desired gear ratio or forward or reverse can be obtained by non-engagement. With respect to the brake 30, in the non-engaged state, the clutch drum 28 rotates freely because it is not restrained, and in this case does not participate in the transmission ratio, and in the engaged state the clutch drum 28 is braked. In accordance with the gear ratio, the rotation of the carrier base 10, that is, the carrier plate 37 is controlled.

In the transmission, the carrier base 10 is an installation place of a rotation speed sensor (not shown) for transmission control. Further, since the carrier base 10 receives a thrust force during the operation of the transmission, thrust

bearings

42 and 44 are disposed on both sides of the annular plate 12 at the connection with the boss 14. The sun gear side of the boss portion 14 presents a somewhat thin portion 14-1 toward the sun gear.

In the configuration of the conventional carrier base 10, the annular plate portion 12 and the boss portion 14 are integrated by forming the entire carrier base 10 as a sintered product, or in the case of press forming from a steel plate, the annular plate portion 12 And the boss portion 14 are separately manufactured and integrated by welding or the like. However, in the case of using a sintered product, it involves complicated steps such as raw material mixing, molding, and sintering, and the production tact is long, resulting in a considerable increase in cost. Moreover, since it also starts a joining process when starting from another part and integrating by welding etc., this will also lead to a cost increase.

In the present invention, in view of the above problems, the carrier base 10 is formed from a single steel plate by pressing without forming material defects, which will be described below.

FIGS. 2 and 3 illustrate the press forming process of the cylindrical part of the present invention from a single steel plate in the first embodiment, and only one side of the central axis L is shown for the sake of clarity. In the figure, the black arrows indicate the main pressing force of the press (the pressing force by the crank in the case of a mechanical press) along with the direction of its application, and the white arrows indicate the force of the die cushion (spring force) Is displayed along with its direction of addition.

2A and 2B show one side of the center line L of the burring apparatus in the press line, and in FIG. 2A, the work W is made of one circular steel plate (only one side of the center line L is shown), It is shown in a state in which punched circular openings W _0. The workpiece W is mounted on the lifter 52 at its outer peripheral portion, and the annular die 54 having a straight inner peripheral surface connected to a pressing mechanism (not shown) is opposed to the lifter 52 via the outer peripheral portion of the workpiece W doing. The punch 55 whose outer peripheral surface is straight is vertically fixed to a die base (not shown). The workpiece W in FIG. 2A is located on the transfer line.

In FIG. 2B, the die 54 is lowered due to burring, and the work W is lowered under the die cushion while the outer peripheral portion is held between the die 54 and the lifter 52, and the work W is lowered by the punch 55. the inner peripheral portion is burring between the die 54 and the punch 55, the tubular projecting portion W ₁ to the work side (upper side in the drawing) at the center of the workpiece centerline L and coaxial workpiece W is formed. After forming of the protruding portion W _1, the die 54 is raised, the lifter 52 by the die cushion is raised to the position of FIG. 2 (A), the workpiece W is return position on the transfer line.

FIGS. 2 (C) and 2 (D) show a first stage ironing apparatus adjacent to the burring apparatus. In FIG. 2 (C), the workpiece W obtained by forming the projecting portion W ₁ by burring is held by the force of the die cushion between the lifter 56 and the work holding 58 on the transfer line. In FIG. 2C, the punch 60 connected to the pressing mechanism is located at the upper side. The punch 60 has an outer diameter somewhat larger than the inner diameter of the cylindrical extension W ₁ of the workpiece W obtained by the burring, and the outer diameter of the punch 60 and the inner diameter of the cylindrical extension W ₁ of the workpiece W The difference in As shown in FIG. 2 (D), the cylindrical projecting portion W ₁ of the inner diameter portion of the workpiece W by the punch 60 descends receives ironing over the entire length, wall thickness as the tubular projecting portion W ₂ becomes thin, I squeezed a minute flesh, by plastic flow, toward the lifter 56 side as W ₃ (annular recessed portion 56-1 of the lifter 56) is closer to the lower part of FIG. After the first stage of ironing, the punch 60 returns to the top dead center position (C), and the work W is raised to the transfer line by the force of the die cushion.

FIGS. 3E and 3F show a second stage ironing device adjacent to the first stage ironing device. In FIG. 3 (E), the outer peripheral part of the work W of FIG. 2 (D) obtained in the first stage ironing process is held between the lifter 62 and the work presser 64 by the force of the die cushion on the transfer line. . In FIG. 3E, the punch 65 connected to the pressing mechanism is retracted upward. Punch 65 has somewhat larger outer diameter than the cylindrical projecting portion W ₂ of the inner diameter of the workpiece W obtained by ironing processing of the first stage, the tubular projecting portion of the outer diameter of the workpiece W of the punch 65 The difference from the inner diameter of W ₂ is the ironing cost. As shown in FIG. 3 (F), the tubular projecting portion W ₂ of the inner diameter of the workpiece W by the punch 65 descends undergoing ironing over the entire length, flow occurs in meat downwards in the figure, the tubular projecting portion The wall thickness is reduced as in W ₄ , and the thickened portion is plastically flowed toward the annular recess 62-1 of the lifter 62 by plastic flow, and is opposite to the cylindrical overhang portion W ₄ (see FIG. molding is carried out below) to the work center line L coaxial cylindrical projecting portion W _5. After ironing, the punch 65 returns to the top dead center position (E), and the work W is raised to the transfer line by the force of the die cushion.

FIG. 3 (G) shows a tubular part which is a work W formed by pressing a single steel plate as described above, and the first disc in which the disc portion 66 and the center line L on both sides thereof are in common. It comprises an overhang portion 67 (W ₄ ) and a second overhang portion 68 (W ₅ ). By subjecting this cylindrical part to a necessary finishing process such as cutting, the carrier base 10 of FIG. 1 is obtained.

In the above embodiment, the ironing process after burring uses a cylindrical punch and die of uniform diameter, the inner diameter of the overhanging portion by the burring is ironed, and the first stage ironing process of flowing the meat toward the root side The second stage ironing step is carried out in which the overhanging portion is formed on the opposite side by changing the diameter of the punch for the entire length by changing the diameter of the punch and forming the overhanging portion formed by the first stage ironing process, but it is smooth It is possible to add an ironing process (one or more stages) with an intermediate diameter punch and die in the first stage ironing process and the second stage ironing process if necessary for the flow of meat .

FIG. 4 shows a second embodiment of the press-forming method of the present invention. Also in this embodiment, bosses extending on both sides in the axial direction from a single steel plate can be press-formed. As in the first embodiment (FIG. 2 and FIG. 3), it is at least three steps of the burring, the first stage ironing process and the second stage ironing process, and is simplified. Steps corresponding to or related to FIG. 2 and (B), (D), and (F) in the embodiment are shown by (1), (2), and (3), respectively. In this second embodiment, cylindrical dies and punches of uniform diameter are used as in the first embodiment. That is, the central portion of the workpiece W'annular disc-shaped on the burring step (1) the lifter 69 is pressed by the punch 70, the overhang _W'1 on the outer peripheral portion of the workpiece W'by an annular die 72 in the outer periphery To mold. In ironing of the second stage (2), and holding the work W'inner portion of the overhanging portion _W'1 between lifter 74 and the workpiece retainer 76, FIG outside diameter of the flared portion _W'1 by an annular punch 78 of by squeezing downward, while forming the work W'one side thinned center line L coaxially cylindrical outer peripheral overhang _W'2, gather meat as W'the base side _3. In ironing of the second stage (3), a portion of the inner from the outer peripheral overhang _W'2 work W'held between the lifter 80 and the workpiece retainer 82, annular punch outer diameter portion of the outer peripheral overhang _W'2 by squeezing by 84, forming a tubular projecting portion _W'5 is performed on the opposite side to the further center line L coaxially cylindrical overhang _W'4 which is thinned. Also in this embodiment, as in the first embodiment, if necessary, ironing with an intermediate diameter punch and die (one or more stages in the first stage ironing and the second stage ironing) It is possible to add stages).

FIG. 5 shows a third embodiment. This embodiment is the same as the first embodiment in the burring process (1) and the first stage ironing process (2), and uses cylindrical dies and punches of uniform diameter, and the workpiece W ′ ′ is used in the burring process. Is pressed by the die 54 against the lifter 52, whereby the overhang portion W ′ ′ ₁ is formed on the inner periphery of the work W ′ ′ by the punch 55. Further, in the first stage ironing, the work W ′ ′ is lifted 56 and work presser 58 and While holding at the same time, ironing of the overhang W ′ ′ ₁ is performed by the punch 60 to form a thin-walled cylindrical overhang W ′ ′ ₂ and also brings meat like W ′ ′ _{3 to} the root side. Second stage The ironing process (3) is different from the first embodiment, and the die hole is a stepped cylindrical die 86 and a central stepped punch 88 (upright fixed to a die base not shown) is used. The attached die 86 is The lower end inner periphery of the inner diameter is provided with an enlarged diameter portion 86-1, and the punch 88 is provided with a reduced diameter portion 88-1 at the tip end. ′ ′ Is lowered with respect to the punch 88 fixed at the center, and the upper portion of the overhang W ′ ′ ₂ is formed by the reduced diameter portion 88-1 at the tip of the punch 88 and the enlarged diameter portion 86-1 at the lower end of the die 86. Flow into the annular cavity to fill the cavity. Further, the overhanging end face of the overhanging portion W ′ ′ ₂ is abutted (restrained) on the shoulder portion (shoulder portion formed by the annular groove 86-1) of the die 86, and the thickness of the upper portion of the overhanging portion W ′ ′ ₃ is substantially thick Although the inner diameter portion of the lower portion of the overhang W ′ ′ ₂ is squeezed by the enlarged diameter portion 88-2 of the punch 88 by the lowering of the work by the lowering of the die 86, the opposite side is not restricted. The flow of meat to the (downward in the figure) occurs, and the side opposite to the overhang W ′ ′ ₃ is formed into a cylindrical overhang W ′ ′ _4. Therefore, in this embodiment, the second stage ironing is the inner circumference. Since the overhanging portions W ′ ′ ₃ and W ′ ′ ₄ after ironing are not the same thickness (the inner circumferential surface is formed with a step) because they are partial rather than full length, the overhanging portions W ′ ′ ₃ and W ′ ′ _{Since 4} and 5 are cylindrically extended on both sides in the axial direction of the work, the extended portions W ′ ′ ₃ and W ′ ′ ₄ are It can be said that the cross section in the connecting portion is substantially T-shaped. In this embodiment, since the upper end side of the overhanging portion W ′ ′ ₃ is restrained during the second stage of ironing, the overhanging portion to the opposite side As in the first and second embodiments, it is possible to obtain a reliable meat flow for forming W ′ ′ _4. Also in this embodiment, if necessary, the second step of the first stage ironing process is also possible. Also in the staged ironing process, it is possible to add an ironing process (one stage or multiple stages) with a punch and die of an intermediate diameter.

FIG. 6 shows a fourth embodiment, in which overhang portions having different thicknesses on both sides of the outer periphery of the work are formed by ironing. This embodiment is the same as the second embodiment (FIG. 4) with respect to the burring process (1) and the first stage ironing process (2), and using a cylindrical die and punch of uniform diameter, the burring process in "'by pressing toward the lifter 69 by the punch 70 in the center of the workpiece W by an annular die 72"' workpiece W forming the tubular projecting portion W "_'1 to the central axis L coaxial with the outer periphery side. In the first stage of ironing, the outer diameter portion of the overhanging portion W ′ ′ ′ ₁ is ironed by the annular punch 78 while the workpiece W ′ ′ ′ is held by the lifter 74 and the workpiece presser 76, and the thinned overhang is obtained. While making it part W ′ ′ ₂ and bringing meat to the root side (downward in the figure) like W ′ ′ _3. The second stage of ironing (3) is the third embodiment of ironing (FIG. 5 (3)) is similar, and the die hole has a stepped cylindrical ring Lee 90 and (upright fixed to a not-shown die base), an outer peripheral surface and the punch 92 with a cylindrical stage is used, "'by pressing by a punch 92, overhang W"' workpiece W on the lifter 94 ₂ The upper end portion of the lower end of the punch 92 flows (flows) into the annular cavity between the outer diameter reduced diameter portion 92-1 at the lower end of the punch 92 and the inner diameter enlarged diameter portion 90-1 at the upper end of the die 90 to fill the cavity and The end face of the part W ′ ′ ′ ₂ is abutted and restrained by the lower end of the punch 92 (a shoulder 92-3 connected to the reduced diameter part 92-1). Therefore, since the outer diameter portion of the lower portion of the overhang portion W ′ ′ ′ ₂ is squeezed by the enlarged diameter portion 90-2 of the fixing die 90 by the descent of the work due to the descent of the punch 92, the unrestrained downward meat is Flow occurs to form an overhang W "' _{4 in the} opposite direction to the overhang W"' _3. Therefore, also in this embodiment, the post-stroke overhang W "' ₃ similar to the embodiment of FIG. Although the wall thickness of the workpiece W ′ ′ ₄ is not the same as the wall thickness of the workpiece W ′ ′ ₄ , the cross-section has a substantially T-shaped configuration because the workpiece W ′ ′ ′ has overhangs on both sides in the axial direction. In this embodiment, as in the first to third embodiments, if necessary, ironing with an intermediate diameter punch and die in the first stage ironing and the second stage ironing (one stage Or, it is possible to add multiple stages).

DESCRIPTION OF SYMBOLS 10 Carrier base 12 Annular plate part 14 Boss part 16 Pinion 18 Sun gear 20 Ring gear 24 Input shaft 28 Clutch drum 32 Drive plate 34 Driven plate 36 Annular piston
38A, 38B: annular elastic member 52: lifter 54: die 55: punch 56: lifter 58: work presser 60: punch 62: lifter 64: work presser 65: punch 66: disc portion 67: first projecting portion (W ₄ )
68: second overhanging portion 68 (W ₅ )
70: Punch 72: Die 7
74 ... lifter 76 ... workpiece pressure member 78 ... punch 86 ... stepped die
86-1 ... Expanded diameter portion 87 of stepped die Lifter 88 ... Stepped punch
88-1 ... Diameter reducing portion 90 of stepped punch ... Stepped die
90-1 ... Inner diameter enlarged portion 92 of stepped die ... Stepped punch
92-1 ... Reduced diameter part W of stepped punch ... Work

Claims

It is a press-formed product formed from a single steel plate, and has a disc portion, and an overhang portion located on the outer diameter side or the inner diameter side with respect to the disc portion and extending in both axial directions The connection part between the part and the overhang part is a press forming method of an annular part having a substantially T-shaped cross section,
Forming one side of the work into a cylindrical first overhang by performing burring on a disc-shaped work consisting of a single steel plate on the inner or outer diameter side;
Forming an annular part by forming a second overhanging portion in a direction opposite to the first overhanging portion by restraining the first overhanging portion while holding the work up and down;
The ironing step is a first step of ironing the meat toward the base of the first overhang, and holding the workpiece up and down while the first overhang is at least the side to which the meat is approached. And a press forming method further comprising at least two stages of ironing with a second stage ironing.
In the invention according to claim 1, in the first-stage ironing process and the second-stage ironing process, the first obtained by burring using a cylindrical punch and a die of uniform diameter. A press molding method for ironing over the entire length of the overhang portion.
In the invention according to claim 1, in the ironing process of the first step, ironing is performed over the entire length of the first overhanging portion obtained by the burring process using a cylindrical punch and die of uniform diameter, In the two-stage ironing process, the stepped cylindrical die and the punch are used to restrain the end of the first overhang obtained by the first-stage ironing process while the first overhang is being restrained. The press forming method which further irons a 1st overhang | projection part in the site | part of the separation side from the restrained edge part, and it forms in a 2nd overhang | projection part by the flow of the meat by this.