Metal plate burring method

Abstract

Respective gaps between a pair of vertical outer surfaces parallel to a pressing direction of a punch and inner surfaces of a cavity portion of a die facing the same, at positions at both ends in a longitudinal direction of the cross-section of the punch, are set smaller than respective gaps between outer surfaces parallel to the pressing direction of the punch and inner surfaces of the cavity portion of the die facing the same, at positions at both ends in a width direction of the cross-section. Burring height formed by pressing a punch for burring toward the cavity portion to insert the punch into the same is generally proportional to these gap values, and therefore the burring height at ends in the major axis direction becomes lower than that in the minor axis direction.

Claims

1. A burring method on a metal plate, comprising the steps of: arranging a first surface of the metal plate on a surface of a die, the die having a cavity portion forming a vertical inner circumferential surface relative to a planar face of the die, and the cavity portion's horizontal cross-section inner circumference parallel to the planar face being a flat shape, the flat shape being oblong of length greater than width; and pressing a burring punch from a second surface of the metal plate toward the cavity portion, the second surface of the metal plate being opposite the first surface of the metal plate, the burring punch having an oblong horizontal cross-section of length greater than width, and the burring punch having a vertical outer circumferential surface relative to the planar face of the die, wherein: the punch has a flat cross-section parallel to the planar face; and in a state in which the burring punch is pressed toward the cavity portion of the die with the metal plate therebetween, a gap between the vertical outer circumferential surface of the burring punch parallel to a pressing direction of the burring punch and the vertical inner circumferential surface of the cavity portion of the die facing the same is set smaller at both ends in a longitudinal direction of the horizontal cross-section of the burring punch than between said both ends whereby a burring of lesser height at said both ends than between said both ends is formed.

2. A burring method on a metal plate, comprising the steps of: arranging a first surface of the metal plate in which a preliminary flat hole has been formed in advance on a surface of a die, the preliminary flat hole having an oblong horizontal cross-section of length greater than width, the die having a cavity portion forming a vertical inner circumferential surface relative to a planar face of the die, and the cavity portion's horizontal cross-section inner circumference parallel to the planar face being a flat shape, the flat shape being oblong of length greater than width; and pressing a burring punch through the preliminary flat hole from a second surface of the metal plate toward the cavity portion, the second surface of the metal plate being opposite the first surface of the metal plate, the burring punch having an oblong horizontal cross-section of length greater than width, and the burring punch having a vertical outer circumferential surface relative to the planar face of the die, wherein: the punch has a flat cross-section parallel to the planar face; and in a state in which the burring punch is pressed toward the cavity portion of the die with the metal plate therebetween, a gap between the vertical outer circumferential surface of the burring punch and the vertical inner circumferential surface of the cavity portion of the die facing the same is set smaller at both ends in a longitudinal direction of the horizontal cross-section of the burring punch than between said both ends whereby a burring of lesser height at said both ends than between said both ends is formed.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates a partial perspective view for explaining one example of the burring method of the present invention.

(2) FIG. 2 illustrates a plan view of FIG. 1.

(3) FIG. 3 illustrates a partially enlarged side cross-section view (A) in a preliminary perforating step of the metal plate 1, and a partially enlarged side cross-section view (B) showing a burring step in FIG. 1.

(4) FIG. 4 illustrates a partially enlarged side cross-section view of a metal plate burred according to the present invention.

(5) FIG. 5 illustrates a partially enlarged perspective view of a header plate burred according to the present invention.

(6) FIG. 6 illustrates a VI-VI arrow-seen cross-section view of FIG. 5.

(7) FIG. 7 illustrates a partial cross-section view of a header plate 8 different from FIG. 6, which is burred according to the present invention.

(8) FIG. 8 illustrates a partially enlarged perspective view of a heat exchanger using a furthermore another header plate burred according to the present invention.

(9) FIG. 9 illustrates a IX-IX arrow-seen cross-section view of FIG. 8.

(10) FIG. 10 illustrates a X-X arrow-seen cross-section view of FIG. 9.

(11) FIG. 11 illustrates a partial perspective view showing an example in which crack occurs at a burring portion.

(12) FIG. 12 illustrates a view explaining a conventional burring method.

DESCRIPTION OF EMBODIMENTS

(13) Next, on the basis of the drawings, embodiments of the present invention will be explained. FIG. 1 illustrates a partial perspective view showing one example of the burring method of the present invention, and FIG. 2 illustrates a plan view of FIG. 1.

(14) In FIGS. 1 and 2, in a metal plate 1, a preliminary flat hole 1a, which has a flat plan cross-section, has been formed in advance, and the dimension of the major axis thereof is shown as L.sub.3, and the dimension of the minor axis is shown as d.

(15) With regard to a punch 7 for burring, as one example, one whose cross-section orthogonal to pressing direction thereof is a race track-like shape can be employed. In other words, the cross-section thereof has a pair of parallel portions facing each other and a pair of arc portions linking between both ends thereof. The dimension along the axis in the longitudinal direction of the race track-like shape is shown as L.sub.1, and the dimension in the width direction of the punch 7 is shown as D. The lower end face of the punch 7 may not be an arc shape. Note that the dimension L.sub.1 of an axis along the longitudinal direction of the punch 7 is identical to the dimension L.sub.3 of the major axis of the preliminary flat hole 1a. The dimension D of the axis along the width direction of the punch 7 is larger than the dimension d of the minor axis of the preliminary flat hole 1a in the metal plate 1.

(16) A die 12 is one commonly used as a base stand for burring, the whole of which is formed in a block with a hard iron material or the like and a cavity portion 13 is formed from the upper face thereof toward the inside. The cavity portion 13 of this embodiment is a rectangular hole and four inside surfaces extend vertically from the upper face of the die 12 toward the lower side thereof. The dimension of the major axis of the cavity portion 13 is shown as L.sub.2, which is the dimension identical to the dimension L.sub.1 of the axis along the longitudinal direction of the punch 7 and the dimension L.sub.3 of the major axis of the preliminary flat hole 1a. The dimension of the minor axis of the cavity portion 13 is shown as Da.

(17) In this embodiment, the dimension L.sub.2 of the major axis of the cavity portion 13 and the dimension L.sub.1 of the axis along the longitudinal direction of the punch 7 are set to be identical to each other. However, as shown in FIG. 2, the dimension Da of the minor axis of the cavity portion 13 is set to a larger value than the dimension D of the axis along the width direction of the punch 7. Accordingly, the value of the gap (L.sub.2−L.sub.1=0) between the outer surface in the longitudinal direction of the punch 7 and the inner surface in the major axis direction of the cavity portion 13 is set to be smaller than the gap (Da−D>0) between the outer surface in the width direction of the punch 7 and the inner surface in the minor axis direction of the cavity portion 13.

(18) Next, on the basis of FIG. 3, the burring method in this embodiment shown in FIG. 1 will be explained. FIG. 3(A) is a partially enlarged side cross-section view showing a state where the metal plate 1 is being subjected to perforating machining of the preliminary flat hole 1a. The perforating machining of the preliminary flat hole 1a is performed by pressing a perforating punch 14a or the like in an arrow direction, in a state where one surface of the metal plate 1 is arranged on the upper face of a die 12a, and FIG. 3(A) shows just for reference a small piece 1b of the metal plate 1 having fallen in the cavity when punching has been performed.

(19) FIG. 3(B) illustrates a partially enlarged side cross-section view showing a state where burring is being performed using the punch 7 shown in FIG. 1. The punch 7 has a flat race track-like cross-section that is orthogonal to the pressing direction, and has two even side surfaces parallel to each other at both ends in the longitudinal direction thereof and in the width direction thereof. Note that lower end portions of respective side surfaces have been subjected to chamfering.

(20) In this embodiment, the dimension L.sub.2 of the major axis in the cavity portion 13 and the dimension L.sub.1 along the axis in the longitudinal direction of the punch 7 are set to be identical. In other words, the gap between the outer surface in the longitudinal direction of the punch 7 and the inner surface in the major axis direction of the cavity portion 13 is substantially zero. Therefore, when the punch 7 is pushed into the cavity portion 13, there are no portions to be bent up at both ends of the major axis of the cavity portion 13 in the metal plate 1, and as a result burring is substantially not formed at the portions.

(21) In a case where it is also necessary to form a comparatively low burring 3 at metal plate 1 portions positioned at both ends of the major axis of the cavity portion 13, the dimension L.sub.2 of the major axis in the cavity portion 13 may be set to be slightly longer than the dimension L.sub.1 of the axis along the longitudinal direction in the punch 7.

(22) FIG. 4 illustrates a partially enlarged side cross-section view showing a state where the metal plate 1 arranged on the die 12 has been subjected to burring, which shows an example of forming the comparatively low burring 3 at metal plate 1 portions positioned at both ends of major axis of the cavity portion 13, by setting modification of the gap as described above. Meanwhile, FIG. 4 is a side cross-section view seen from the minor axis direction of the cavity portion 13, in which both ends of a high burring 3 at the portion run in a line to the arc low burring 3.

(23) FIG. 5 is a partially enlarged perspective view of a header plate 8 (metal plate 1) burred as in FIG. 4, and FIG. 6 is a VI-VI arrow-seen cross-section view of FIG. 5. In FIG. 6, there are shown together a state where the rim of a tank main body 9 shown by a dotted line is fixed to both ends of the header plate 8 to form a tank 10, and a state where an apex of a flat tube 11 is inserted in the flat hole 2.

(24) FIG. 7 is a partial cross-section view of the header plate burred in a configuration in which the horizontal cross-section shape of the punch 7 is set to an approximate rectangle, and the gap between the outer surface in the longitudinal direction of the punch 7 and the inner surface in the major axis direction of the cavity portion 13 is set substantially to zero. FIG. 7 is shown according to FIG. 6, but in FIG. 7 both ends of the high burring 3 in the minor axis direction in the metal plate 1 form vertical surfaces relative to the planar face of the metal plate 1. In this case, it is shown that any burring 3 is substantially not formed at both ends in the major axis direction of the cavity portion 13.

(25) FIG. 8 illustrates a partially enlarged perspective view of a heat exchanger 16 on which the header plate 8 of another Example burred according to the present invention is mounted, FIG. 9 illustrates a IX-IX arrow-seen cross-section view of FIG. 8, and FIG. 10 is a X-X arrow-seen cross-section view of FIG. 9.

(26) In this example, the horizontal cross-section of the header plate 8 is formed in an arc shape. To the header plate 8, a tank main body 9 having an arc horizontal cross-section is fixed to form a tank 10, and a core portion 14 is formed of stacked plural flat tubes 11 and fins 15 arranged therebetween. Further, burring is formed on this header plate 8 having an arc cross-section. Regarding the height of burring from an opening edge face, it is low at both ends thereof and is high between these.

(27) The heat exchanger 16 is configured by these respective members.

(28) Meanwhile, in FIG. 9, an end lid and a core support 17 fixed to one of ends of the core portion 14, which are not shown in FIG. 8, are shown just for reference.

(29) Note that, in the above explanation, the example in which the preliminary flat hole 1a has been formed in advance in the metal plate 1 is explained, but it may be omitted (claim 1).

INDUSTRIAL APPLICABILITY

(30) The present invention can be utilized for burring a metal plate such as a header plate for a heat exchanger in vehicles and construction machines.

REFERENCE SIGNS LIST

(31) 1 metal plate

(32) 1a preliminary flat hole

(33) 1b small piece

(34) 2 flat hole

(35) 3 burring

(36) 4 crack portion

(37) 5 prepared hole

(38) 6 punch

(39) 7 punch

(40) 8 header plate

(41) 9 tank main body

(42) 10 tank

(43) 11 flat tube

(44) 12 die

(45) 12a die

(46) 13 cavity portion

(47) 14 core portion

(48) 14a perforating punch

(49) 15 fin

(50) 16 heat exchanger

(51) 17 core support