JPH06285553A - Hemming method - Google Patents

Abstract

PURPOSE:To easily and efficiently execute hemming of various metallic plates, and also, to surely obstruct a fact that a crack, etc., are generated on the outside surface. CONSTITUTION:On the inside surface 12 of a metallic plate 10, notch parts 18, 20 are formed so as to be positioned on both sides of a bending center line 16, and thereafter, to this metallic plate 10, bending is performed by about 90 deg. along the bending center line 16. Therefore, a stress concentration is not generated in the part corresponding to the bending center line 16, and it can be obstructed surely that a crack, etc., are generated on the outside surface 22 of the metallic plate 10. In such a state, to the metallic plate 10, bending is further performed by about 90 deg. along the bending center line 16, and a hemming part 32 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hemming method for bending a metal plate material, particularly a plate material having low extensibility, along a bending center line to provide a hemming portion.

[0002]

2. Description of the Related Art A method for maintaining the strength of an edge and smoothing the edge by subjecting the edge of a metal plate material to hemming is widely used. In this case, if hemming is performed on the metal plate with a small radius of curvature,
Stress concentration occurs near the bending center line of this metal plate material.
In particular, when a plate material having low extensibility, such as an aluminum plate material, is used as the metal plate material, defects such as cracks often occur on the outer surface of the hemming portion due to the stress concentration.

Therefore, measures have been taken to prevent the occurrence of a clutch in the hemming portion by locally heating the hemming portion in advance.

[0004]

However, in the above-mentioned prior art, it has been pointed out that the work of locally heating the metal plate material in advance before the hemming process is required, and the efficiency of the entire hemming process cannot be achieved. There is.

The present invention is intended to solve this type of problem and enables various types of metal plate materials to be hemmed easily and efficiently, while ensuring that cracks and the like occur on the outer surface. An object of the present invention is to provide a hemming processing method capable of preventing the hemming.

[0006]

In order to achieve the above object, the present invention is a hemming method in which a metal plate material is bent along a bending center line to provide a hemming portion on the metal plate material. A step of forming notches having a predetermined width on both sides of the bending center line on the inner surface of the metal plate after bending, and the metal plate having the notches formed, And a step of performing a bending process along the bending center line to provide the hemming portion.

[0007]

In the hemming method of the present invention, first, since notches are formed on both sides of the bending center line on the metal plate material, the notches are formed along the bending center line. It is possible to surely prevent the stress from being distributed in the vicinity of the bending center line and the stress concentration in the vicinity of the bending center line.

That is, as shown in FIG. 1, the metal plate material S
When a bending moment is applied to, a vertical stress σ is generated in different directions (tensile side and compression side) with the neutral axis N of the metal plate material S as a boundary. On the other hand, as shown in FIG.
When a bending moment acts on the metal plate material S1 having the notch K on the inner peripheral side, the stress σ1 is generated around the notch K.
Is the largest and so-called stress concentration occurs.

Therefore, if notches are formed on the inner surface of the metal plate on both sides of the bending center line, a relatively large stress is applied to each notch when the metal plate is hemmed. It is possible to prevent the occurrence of stress concentration on the outer side surface corresponding to the bending center line.
As a result, cracks and the like do not occur on the outer surface of the plate material when the hemming process is applied to a plate material having low stretchability,
Moreover, the efficiency of the entire hemming process can be easily achieved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hemming method according to the present invention will be described in detail below with reference to the accompanying drawings. 3 to 6 show the steps of the hemming method according to this embodiment.

In FIG. 3, reference numeral 10 indicates a metal plate material to which the hemming method according to this embodiment is applied. The metal plate material 10 is a plate material having low extensibility, for example, an aluminum plate material, and is separated from an edge portion 14 by a predetermined distance on an inner surface (hereinafter referred to as an inner surface 12) after bending (described later). The bending center line 16 is set.

Therefore, first, the inner surface 12 of the metal plate member 10
The notch portions 18 and 20 are formed on both sides of the bending center line 16 and are cut out in the width direction of the metal plate material 10 (see FIG. 4). The notches 18 and 20 can have various groove shapes such as a semicircular cross section and a V-shaped cross section.
For example, it is formed by milling.

Next, the metal plate material 10 is passed through a hemming machine (not shown), and is approximately 90 ° along the bending center line 16.
Only bending is applied (see FIG. 5). Here, a stress distribution curve 24 as shown in FIG. 7 is provided on the outer side surface 22 of the metal plate material 10. The stress distribution curve 24 has a high stress portion 26 also in a portion corresponding to the bending center line 16,
The high stress portion 28a is formed in the portion corresponding to the notches 18 and 20.
28b, the stress is dispersed throughout.
On the other hand, the conventional metal plate material having no notch portion is approximately 9
In the stress distribution curve 2 when bent to 0 °, the portion corresponding to the bending center line 16 is maximized and stress concentration occurs.

Therefore, in this embodiment, stress concentration does not occur in the portion corresponding to the bending center line 16, and cracks or the like occur in the outer surface 22 of the metal plate material 10 which is an aluminum plate material having particularly low extensibility. The advantage is that it can be reliably blocked.

Next, the metal plate material 10 is further subjected to a hemming processing machine (not shown) along the bending center line 16 to further form about 9
The hemming portion 32 is provided by bending only 0 ° (up to about 180 ° C. as a whole) (see FIG. 6). Here, as shown in FIG. 8, the stress distribution curve 34 generated in the metal plate material 10 is substantially uniform as a whole, and the stress generated when hemming a conventional metal plate material having no notch portion is performed. Unnecessary stress does not occur in the portion corresponding to the bending center line 16 like the distribution curve 4.

As a result, the outer surface 22 of the metal plate member 10
In addition, it is possible to reliably and easily prevent the occurrence of defects such as cracks, and it is possible to obtain a high quality hemming product. Moreover, it suffices to add a simple process of forming the notches 18 and 20 to the metal plate material 10 prior to bending, and the efficiency of the entire hemming operation can be easily performed.

[0017]

According to the hemming method of the present invention, the following effects and advantages can be obtained.

First, since the notch portions are formed on both sides of the bending center line on the metal plate material, stress is dispersed in the notch portions when bending is performed along the bending center line, and the bending is performed. It is possible to reliably prevent stress concentration from occurring near the center line. As a result, when a hemming process is performed on a plate material having particularly low stretchability, cracks and the like do not occur on the outer surface thereof, and the efficiency of the entire hemming process is easily achieved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a stress distribution curve when a bending moment acts on a plate material.

FIG. 2 is an explanatory diagram of a stress distribution curve when a bending moment acts on a plate material having a cutout portion.

FIG. 3 is a perspective explanatory view of a metal plate material used in the hemming method according to the embodiment of the present invention.

FIG. 4 is an explanatory perspective view showing a state in which a notch portion is formed on the metal plate material.

FIG. 5 is a perspective explanatory view showing a state where the metal plate material is bent by approximately 90 °.

FIG. 6 is an explanatory perspective view showing a state in which the metal plate material is bent to approximately 180 °.

FIG. 7 is an explanatory diagram of stress distribution curves of the present example and the conventional example when the metal plate material is bent by approximately 90 °.

FIG. 8 is an explanatory diagram of stress distribution curves of the present example and a conventional example when the metal plate material is bent to approximately 180 °.

[Explanation of symbols]

 10 ... Metal plate material 12 ... Inner side surface 14 ... Edge part 16 ... Bending center line 18, 20 ... Notch part 22 ... Outer side surface 24, 34 ... Stress distribution curve

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tetsuya Wakabayashi 1-10-1 Shin-Sayama, Sayama-shi, Saitama Honda Engineering Co., Ltd.

Claims (1)

[Claims] 1. A hemming method in which a metal plate material is bent along a bending center line to provide a hemming portion on the metal plate material, wherein A step of forming notches having a predetermined width on both sides of the center line, and a step of bending the metal plate material on which the notches are formed along the bending center line to provide the hemming portion And a hemming method.