BEAD FORMING UNIT FOR PRESS

Abstract

A bead forming unit for a press is formed between a blank holder and an upper press portion and forms at least a dual circular bead for controlling a material flow along an edge portion of a material panel during a process for pressurizing the material panel placed between upper and lower press portions to form a product panel. The bead forming unit for a press includes: a bead projection formed to protrude out of the lower die face surface of the blank holder and having at least one dual circular bead groove integrally formed to form a waveform thereto; and a dual circular bead groove formed on the upper die face surface of the upper press portion and having at least one dual circular bead projection integrally formed to form a waveform complementary to the dual circular bead groove.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(a) on Korean Patent Application No. 10-2007-0040710, filed on Apr. 26, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bead forming unit for a press, and more particularly, to a bead forming unit for a press in which at least one dual circular bead is formed according to a forming depth on a bead surface of a bead forming unit arranged on die face surfaces of a blank holder and an upper press portion of a press apparatus in order to control a bead force, whereby defects such as wrinkles which may occur on a forming product can be minimized.

2. Description of the Related Art

Generally, a vehicle is manufactured by numerous assembling processes using about twenty to thirty thousands of parts.

In particular, a vehicle body is formed by a first assembling process such that product panels are produced by many kinds of press apparatuses, and the respective product panels are then assembled in a vehicle body factory to form a vehicle body of a body-in-white (B.I.W) state.

Such a product panel is formed by press, forming a material panel through many kinds of press apparatuses. FIG. 1 shows a process for forming a product panel out of a material panel by a conventional punch press apparatus.

In the punch press apparatus of FIG. 1, a lower press portion 101 having a shape corresponding to a lower surface of a product panel is mounted on a bolster 103, and a blank holders 107 are mounted on the bolster 103 via cushion pins 105 along an outside of the lower press portion 101.

An upper press portion 111 having a shape corresponding to an upper surface of a product panel is mounted on a slider 109 above the lower press portion 101. A material panel 113 is put on the blank holders 107 of the lower press portion 101 and is then pressed by the upper press portion 111 to thereby form a product panel.

In more detail, as shown in S1 of FIG. 1, the upper press portion 111 and the blank holder 107 move up, and the material panel 113 is placed between the upper press portion 111 and the lower press portion 101 and blank holders 107.

Then, as shown in S2 of FIG. 1, the upper press portion 111 moves down, so that an edge portion of the material panel 113 is hold by a upper die face surface 115 of the upper press portion 111 and a lower die face surface 117 of the blank holder 107. The upper press portion 111 and the blank holder 107 move down together as shown in S3 of FIG. 1, and a product panel is forging-processed by a press as shown S4 of FIG. 1.

Here, the upper die face surface 115 of the upper press portion 111 and the lower die face surface 117 of the blank holder 107 serve to prevent a corner portion of a material panel 113 from being burst or torn by controlling a material flow rate when the product panel is formed, affecting the quality of a completed product panel. For example, if material holding pressure of the upper and lower die face surfaces 115 and 117 is very high, a material flow, i.e., metal flow is not smooth, causing a crack in a material panel, and if the holding pressure is too low, a material flow rate is high, causing a material surface to be bent.

In order to resolve the above problem, a round type bead forming unit BU is formed conventionally on the upper and lower die face surfaces 115 and 117 to control a cushion force as shown in FIG. 2.

The bead forming unit BU comprises a bead projection 121 formed to protrude out of the lower die face surface 117 of the blank holder 107 and a bead groove 123 formed on the die face surface 115 complementary to the bead projection 121.

However, in case of the conventional bead forming unit BU for a press described above, if a curvature R of both side portions of a bead portion is small and cushion pressure of the blank holder 107 does not reach a forming force, the blank holder 107 can not stably hold the material panel 113, leading to an unstable material flow. In contrast, if the cushion pressure of the blank holder 107 is increased to have a sufficient forming force, a material panel 113 may locally get burst because a desired material flow does not occur, thereby badly affecting the quality of the product panel.

Also, if two or more lines of beads are applied to suppress a material flow, too many bents may occur on the die face surface, and a holding force of the blank holder 107 becomes too strong, so that a material flow discontinuously occurs, and hence bents occurs on a surface of product panel, leading to the low throughput.

On the other hand, if a curvature R of both side portions of the bead projection 121 is small, plating portion of the material panel caught by the bead projection 121 may be locally peeled, and defects such as bents or hacked portions may occur. In this instance, the upper and lower die face surfaces 115 and 117 should be overall processed and grinded again, leading to high-cost and lengthy processing time.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the aforementioned problems associated with prior arts.

In one aspect, the present invention provides a bead forming unit for a press in which at least one dual circular bead is formed according to a forming depth on a bead surface of a bead forming unit formed on the die face surfaces of the blank holder and the upper press portion to adjust a bead force, thereby minimizing defects such wrinkles which may occur on forming a product.

In a preferred embodiment, the present invention provides a bead forming unit for a press which is formed between a lower die face surface of a blank holder and a upper die face surface of an upper press portion and forms at least a dual circular bead for controlling a material flow along an edge portion of a material panel during a process for pressurizing the material panel placed between upper and lower press portions to form a product panel, comprising: a bead projection formed to protrude out of the lower die face surface of the blank holder and having at least one dual circular bead groove integrally formed to have a waveform; and a bead groove formed on the upper die face surface of the upper press portion complementary to the bead projection and having at least one dual circular bead projection integrally formed to have a waveform complementary to the dual circular bead groove of the bead projection.

With respect to the lower die face surface of the blank holder, both lower side portions of the bead projection have round surfaces with predetermined curvature radiuses.

A contact managing surface having a plane shape is formed between the lower die face surfaces of the blank holder and the upper die surfaces of the upper press portion, the contact managing surface contacting and holding at least a surface of a portion of the material panel in a material flow direction between the bead projection and the bead groove.

The dual circular bead groove and the dual circular bead projection have round surfaces with predetermined curvature radiuses of substantially the same length.

The above features and advantages of the present invention will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated in and form a part of this specification, and the following Detailed Description of the Invention, which together serve to explain by way of example the principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 shows a process for forming a product panel out of a material panel by a conventional punch press apparatus;

FIG. 2 is a cross-sectional view illustrating a conventional bead forming unit;

FIG. 3 is a cross-sectional view illustrating a bead forming unit for a press according to an exemplary embodiment of the present invention; and

FIG. 4 is a cross-sectional view illustrating a bead formed by the bead forming unit for a press according to the exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 3 is a cross-sectional view illustrating a bead forming unit for a press according to an exemplary embodiment of the present invention.

A press apparatus to which the exemplary embodiment of the present invention is applied is described with reference to FIG. 1.

In the press apparatus which employs the bead forming unit for a press according to the exemplary embodiment of the present invention, as shown in FIG. 1, a lower press portion 101 having a shape corresponding to a lower surface of a product panel is mounted on a bolster 103, and blank holders 107 is mounted on the bolster 103 through cushion pins 105 along the outside of the lower press portion 101.

An upper press portion 111 having a shape corresponding to an upper surface of a product panel is mounted on a slider 109 above the lower press portion 101. A material panel 113 is placed on the blank holders 107 of the lower press portion 101 and is then pressed by the upper press portion 111 to form a product panel.

In the press apparatus having the above described configuration, a bead forming unit BU according to the exemplary embodiment of the present invention has at least a dual circular bead for controlling a material flow along an edge portion of the material panel 113 during a process for pressurizing the material panel 113 to form the product panel. The bead forming unit BU, as shown in FIG. 3, comprises a bead projection 10 formed to protrude out of the lower die face surface 117 of the blank holder 107 and a dual circular bead groove 20 formed on the upper die face surface 115 of the upper press portion 111 complementary to the bead projection 10. The bead projection 10 and the dual circular bead groove 20 are integrally formed to have a waveform

A bead groove 30 is formed on the upper die face surface 115 of the upper press portion 111 complementary to the bead projection 10, and a dual circular bead projection 40 is formed at the bead groove 30 complementary to the dual circular bead groove 20 of the bead projection 10. The bead groove 30 and the dual circular bead projection 40 are integrally formed to have a waveform.

In the exemplary embodiment of the present invention, one dual circular bead projection 40 and one circular bead groove 20 are formed, but the present invention is not limited to that. Two or more dual circular bead projections 40 and two or more circular bead grooves 20 may be formed to increase a bead force.

With respect to the lower die face surface 117 of the blank holder 107, both lower end portions of the bead projection 10 have round surfaces and have curvature radiuses R1 and R2, respectively as shown in FIG. 4.

Furthermore, referring to FIG. 3, contact managing surfaces F which are shaped of plane for contacting and holding both upper and lower surfaces of a portion of the material panel 113 in a material flow direction between the bead projection 10 and the bead groove 30 is formed between the lower die face surface 117 of the blank holder 107 and the upper die face surface 115 of the upper press portion 111.

The dual circular bead groove 20 and the dual circular bead projection 40 have round surfaces and have a predetermined curvature radius R5 of substantially the same length.

Component factors of a dual circular bead formed by the bead projection 10 and the bead groove 30 which have the curvature radiuses R1, R2 and R5 and a contact managing surface F and their applicable representative measurements are described below in detail with reference to Table 1.

As shown in FIG. 4 and Table 1, as the bead height H is larger, the bead force is increased and the strength of bead is stronger. However the applicable measurement of the bead height is preferably limited to 0 mm<H<10 mm because a holding wrinkle may occur if the bead height H is equal to or higher than 10 mm.

The smaller the bead width W is, the stronger the bead force is, and thus the stronger the strength of bead is. However the applicable measurement of the bead width is preferably limited to 7 mm<W<20 mm because there is a disadvantage in the aspect of material reduction if the bead width W is equal to or higher than 20 mm.

TABLE 1
Component Factors
(Applicable
Representative
Measurement)			Range (mm,
(mm, degree))	Factor Name	Effects	degree)
H(8)	Bead Height	The higher H is, the	0 < H < 10 mm
		stronger the bead force is
		and the stronger the bead
		strength is
W(15)	Bead Width	The smaller W is, the	7 < W < 20 mm
		stronger the bead force is
		and the stronger the bead
		strength is
h(2)	Depth of dual	The deeper h is, the	0 ≦ h < 5 mm
	circular bead	stronger the bead force is
		but the weaker the bead
		strength is
θ1 (degrees)	Forming angle	The larger θ1 is, the	0 ≦ θ1 < 15 degree
	of bead inner	weaker the bead force is,
	sidewall	but the stronger the bead
		strength is and the more
		excellent an effect for
		preventing the material
		panel from being caught
		is
θ2 (2 degree)	Forming angle	The larger θ2 is, the	0 ≦ θ2 < 15 degree
	of bead outer	weaker the bead force is,
	sidewall	but the stronger the bead
		strength is and the more
		excellent an effect for
		preventing the material
		panel from being caught
		is
φ1 (6)	Diameter of	The larger φ1 is, the	0 ≦ φ1 < 10 mm
	dual circular	stronger the bead force is
	bead	and the weaker the bead
		strength is, and the larger
		the number of φ1
		installed is, the stronger
		the bead force is
R1, R2, R3, R4, R5	Bead	The larger R1, R2, R3	2 mm ≦ R1, R2,
(3, 3, 2, 2, 3)	processing R	and R4 are, the weaker	R3, R4, R5 ≦ 6 mm
		the bead force is, and the
		larger R5 is, the stronger
		the bead force is
r1, r2 (3, 3)	Bead	The larger r1, r2 are, the	2 mm ≦ r1, r2 ≦ 6 mm
	processing R	weaker the bead force is

The deeper the depth h of the dual circular bead is, the stronger the bead force is but the weaker the bead strength is. Therefore, it is preferable to limit the measurement of h to a range of 0≦h≦5 mm.

The larger a forming angle θ1 of a bead inner sidewall and a forming angle θ2 of a bead outer sidewall are, the weaker the bead force is but the stronger the bead strength is, and the more excellent an effect for preventing the material panel from being caught is. However, its applicable measurement is preferably limited to a range of 0≦θ1, θ2<15 degrees because the bead force is rapidly reduced if θ1 and θ2 are equal to or higher than 15 degrees.

The larger a diameter φ1 of the dual circular bead is, the weaker the bead force is, the weaker the bead strength is, but the larger the number of the dual circular beads installed is, the stronger the bead force is. However its applicable measurement is preferably limited to a range of 0≦φ1≦10 mm because there is a disadvantage in the aspect of material reduction if φ1 is larger than 10 mm and a ladder-shaped bead is formed if φ1 is 0 mm.

The larger the curvature radiuses R1, R2, R3 and R4 are, the weaker the bead force is, and the larger a curvature radius R5 is, the stronger the bead force is. Their applicable measurements are preferably limited to a range 2 mm≦R1, R2, R3, R4, R5≦6 mm because there is a disadvantage in processibility if they are less than 2 mm and there is a disadvantage in the aspect of material reduction if they are more than 6 mm. Here, R5=(φ1)/2, and R3 and R4 are the curvature radiuses of both inner side portions of the bead projection as shown in FIG. 4.

The larger the curvature radiuses r1 and r2 of both outer side portions of the bead projection are, the weaker the bead force is. Their applicable measurements are preferably limited to a range of 2 mm≦r1, r2≦6 mm because there is a disadvantage in processibility if they are less than 2 mm and there is a disadvantage in the aspect of material reduction if they are more than 6 mm.

Table 2 shows usage for forming and its effects according to exemplary combinations of the component factors.

TABLE 2
Component Factor
Combination
(Bead-applied
Representative
Measurement) (mm, degree)	Usage for Forming	Effects
H(8), W(15), h(2), θ1(2deg),	When a product depth is	Possible to suppress a
θ2(2deg), φ1(6), R1(3),	low, when a low forming	material flow because the
R2(3), R3(2), R4(2), R5(3),	depth (less than 35 mm) is	bead force is stronger
r1(3), r2(3), Ra(3), Rb(3),	applied, when to secure a	compared to an existing
Contact managing surface	stiffness of a product surface	bead, possible to perform a
(5)	by a punch forming, when to	punch forming because a
→ HOOD OTR, HOOD	pursue material reduction (to	material flow is
INR: applicable	improve throughput), when	suppressible, possible to
→ (FRT, RR) DOOR OTR:	to replace an existing double	secure a stiffness of a
applicable	bead, when to improve a	product surface, possible to
→ ROOF: applicable	plating peeling problem, and	prevent a product surface
	when to improve mechanical	from being bent, possible to
	processibility to prevent a	improve a plating peeling
	manual process.	problem, possible to
		improve mechanical
		processibility, possible to
		save a material by applying
		a low draw, and possible to
		improve a throughput of a
		press die.
H(6), W(12), h(1.5),	When a product depth is	Possible to suppress a
θ1(2deg), θ1(2deg), φ1(6),	deep, when a deep forming	material flow because the
R1(3), R2(3), R3(2), R4(2),	depth (more than 35 mm) is	bead force is stronger
R5(3), r1(3), r2(3), Ra(3),	applied, when to secure a	compared to the existing
Rb(3), Contact managing	product stiffness by a	bead, possible to perform a
surface (10)	stretching forming, when to	punch forming because a
→ FENDER: applicable	save a material (to improve a	material flow is
→ T/LID OTR (INR):	throughput), when to replace	suppressible, possible to
applicable	an existing double bead,	extend a product surface,
→ T/GATE OTR (INR):	when to improve a plating	possible to prevent a product
applicable	peeling problem, and when	surface from being bent,
→ S/OTR: applicable	to improve a mechanical	possible to improve a plating
→ all of the other vehicle	processibility to prevent a	peeling problem, possible to
body panels: applicable	manual process.	improve mechanical
		processibility, possible to
		save a material by applying
		a low draw, and possible to
		improve a throughput of a
		press die.

A component factor combination that H is 8 mm, W is 15 mm, h is 2 mm, θ1 is 2 deg, θ2 is 2 deg, φ1 is 6 mm, R1 is 3 mm, R2 is 3 mm, R3 is 2 mm, R4 is 2 mm, R5 is 3 mm, r1 is 3 mm, r2 is 3 mm, and a contact managing surface is 5 mm, can be applied to secure a stiffness for product surface by a punch forming and to save a material (to improve a throughput) when a product depth is low like when to form a hood outer, a hood inner, front and rear door outers, a roof, that is, when to form a product having a low forming depth (less than 35 mm).

The other usage for forming and its effects are further listed in Table 2.

A component factor combination that H is 6 mm, W is 12 mm, h is 1.5 mm, θ1 is 2 deg, θ2 is 2 deg, φ1 is 6 mm, R1 is 3 mm, R2 is 3 mm, R3 is 2 mm, R4 is 2 mm, R5 is 3 mm, r1 is 3 mm, r2 is 3 mm, and a contact managing surface is 10 mm, can be applied to secure a stiffness of product surface by a stretch forming and to save a material when a product depth is deep like when to form a fender, tail lid outer and inner, tail gate outer and inner, and a side outer, that is, when to form a product having a deep forming depth (more than 35 mm).

As described above, according to the present invention, at least one dual circular bead is formed according to a forming depth on a bead surface of the bead forming unit formed on the die face surfaces of the blank holder and the upper press portion to control the bead force, whereby there is an advantage of minimizing a product defect like a wrinkle which may occur on a forming product.

The forgoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiment were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that technical spirit and scope of the present invention be defined by the Claims appended hereto and their equivalents

Claims

1. A bead forming unit for a press which is formed between a lower die face surface of a blank holder and a upper die face surface of an upper press portion and forms at least a dual circular bead for controlling a material flow along an edge portion of a material panel during a process for pressurizing the material panel placed between the upper and lower press portions to form a product panel, comprising:

a bead projection formed to protrude out of the lower die face surface of the blank holder and having at least a dual circular bead groove integrally formed thereto to form a waveform; and

a bead groove formed on the upper die face surface of the upper press portion and having at least a dual circular bead projection integrally formed thereto to form a waveform complementary to the dual circular bead groove of the bead projection.

2. The bead forming unit of claim 1, wherein with respect to the lower die face surface of the blank holder, both lower side portions of the bead projection have round surfaces with predetermined curvature radiuses.

3. The bead forming unit of claim 1, wherein the dual circular bead groove and the dual circular bead projection have round surfaces with predetermined curvature radiuses of substantially the same length.

4. The bead forming unit of claim 1, wherein a bead height of the bead projection is substantially between 0 mm to 10 mm.

5. The bead forming unit of claim 1, wherein a bead width of the bead projection is substantially between 7 mm to 20 mm.

6. The bead forming unit of claim 1, wherein a depth of the dual circular bead is substantially between 0 mm to 5 mm.

7. The bead forming unit of claim 1, wherein forming angles of a bead inner sidewall and of a bead outer sidewall of the bead projection are substantially between 0 degree to 15 degrees.

8. The bead forming unit of claim 1, wherein a diameter of the dual circular bead is substantially between 0 mm and 10 mm

9. The bead forming unit of claim 2, or 3, wherein the predetermined curvature radius are substantially between 2 mm and 6 mm.

10. The bead forming unit of claim 1, wherein curvature radiuses of both outer side portions of the bead projection are substantially between 2 mm and 6 mm.

11. The bead forming unit of claim 1, wherein curvature radiuses of both inner side portions of the bead projection are substantially between 2 mm and 6 mm.

12. The bead forming unit of claim 1, wherein at least a contact managing surface of a plane shape is formed on the upper and lower die face surfaces of the blank holder and the upper press portion, the contact managing surface contacting and holding at least a surface portion of the material panel in the material flow direction between the bead projection and the bead groove.