JP2007260721A - Small diameter hole structure on sheet metal and method of forming small diameter hole on sheet metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small diameter hole structure on a sheet metal and a method of forming the small diameter hole on the sheet metal which enable the small diameter hole to be formed on the sheet metal without impairing layout of a product while manufacturing cost is suppressed. <P>SOLUTION: On a body member 2, a weld nut force-fitting hole 21 is formed which has an inner diameter larger than the outer diameter of the weld nut body 41 and equal to or smaller than the outer diameter of a projection lug 42 of the weld nut 4. Into this weld nut force-fitting hole 21, the projection lug 42 is force-fitted and the force-fitted lug is welded, wherein the entire height of the weld nut body 41 is set to be situated inside the weld nut force-fitting hole 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention belongs to the technical field of a small-diameter hole structure for a metal plate and a method for forming a small-diameter hole in a metal plate.

In the small-diameter hole processing on a thick metal plate pressed by sheet metal, the ratio of the length of the press to the diameter of the punch becomes large, so that the punch may be damaged during processing due to insufficient punch strength. Therefore, conventionally, a method has been adopted in which a pilot hole is formed in the processed surface of the thick plate, and the drilling is performed while the drill is positioned using the pilot hole (see, for example, Patent Document 1).
JP-A-11-123623

  However, in the above prior art, after the metal sheet press forming of a thick metal plate, machining or laser processing for small-diameter hole machining is separately required, which increases the number of processes and increases the manufacturing cost. There was a problem.

  On the other hand, as a method of generating a screw hole in a metal plate, a method using machining, a welding nut, and a press-fit nut (curry nut) is known. However, the machining cost is high, and a weld nut or press-fit nut is used. However, there was a problem that the entire nut protruded on one side of the metal plate and the layout of the product was impaired.

  The present invention has been made paying attention to the above-mentioned problems, and the object thereof is to provide a metal plate capable of providing a small-diameter hole in the metal plate while suppressing the manufacturing cost and without impairing the layout of the product. And a method for forming a small-diameter hole in a metal plate.

In order to achieve the above object, the present invention provides:
The metal plate is formed with a weld nut press-fit hole that is larger than the outer diameter dimension of the weld nut body and has an inner diameter equal to or smaller than the projection projection outer diameter dimension of the weld nut,
The projection projection is welded to the weld nut press-fitting hole in a press-fitted state,
The welding nut press-fitting hole is set so that at least a part of the height of the welding nut main body is located.

In the small-diameter hole structure of the metal plate of the present invention, the hole diameter of the weld nut press-fitting hole formed on the metal plate is larger than the outer diameter of the weld nut body, Thus, the hole diameter can be set large, and the hole can be formed using an inexpensive method such as press molding. In addition, since a part of the height of the weld nut body is located in the weld nut press-fitting hole, the amount of protrusion from the metal plate can be made smaller than the height of the weld nut body.
As a result, it is possible to provide a small-diameter hole in the metal plate while suppressing the manufacturing cost and without impairing the layout of the product.

  Hereinafter, the best mode for carrying out the present invention will be described based on the first embodiment.

First, the configuration will be described.
1 is a longitudinal sectional view showing a resin cover mounting portion of a vehicle body body to which a small-diameter hole structure of a metal plate of Example 1 is applied.
The resin cover 1 covers the surface side of the body member 2 and is fastened with bolts 3.

  The body member 2 is a thick metal plate formed by die press molding. The body member 2 is formed with a circular welding nut press-fitting hole 21. A welding nut 4 that is screwed into the bolt 3 is press-fitted and welded into the welding nut press-fitting hole 21.

The weld nut 4 includes a weld nut main body 41 and four projection protrusions 42, and has a height dimension shorter than the thickness of the body member 2.
The weld nut main body 41 has a female screw (small diameter hole) 41a formed therein, and has the same shape as a normal square nut. The weld nut body 41 is set to a shape that does not contact the weld nut press-fitting hole 21.

The projection protrusion 42 is press-fitted into the weld nut press-fitting hole 21 in a state of being completely buried in the body member 2 (press-fitted state). The projection protrusions 42 project radially from the four corners on one end side in the axial direction of the weld nut body 41, and the outer diameter dimension thereof is set larger than the outer diameter dimension of the weld nut body 41. At the tip portions of these four projection projections 42, an inner periphery of the weld nut press-fitting hole 21 and a joint 42a by projection welding are formed. Here, the “outer diameter dimension” refers to the length from the center of the welding nut 4 to the outer surface of the projection protrusion 42.
As this welding nut 4, for example, “square welding nut 1C type, 1D type” defined as “JIS B 1196: 2001” in the JIS standard or an equivalent specification product can be used.

  The weld nut press-fitting hole 21 has a taper shape whose axial cross section is reduced in diameter toward the press-fitting direction of the weld nut 4 (right direction in FIG. 1). The opening edge of the weld nut press-fitting hole 21 on the weld nut 4 press-fitting side (left side in FIG. 1) is set to a diameter larger than the outer diameter of the weld nut main body 41 and smaller than the projection protrusion 42. The opening edge on the mounting surface side (the right side in FIG. 1) is set to have a diameter larger than the outer diameter of the weld nut body 41 and smaller than the projection protrusion 42.

Next, the operation will be described.
[Small-diameter hole forming method of metal plate]
FIG. 2 is an explanatory view showing a method for forming a small-diameter hole in a metal plate of Example 1, and this small-diameter hole forming method includes three steps: (a) drilling step, (b) press-fitting step, and (c) welding step. It has. Hereinafter, each process is demonstrated in order.

(a) Hole making process The hole making process is performed at the time of sheet metal pressing of the body member 2 which is a workpiece. In this drilling step, the punching position of the body member 2 is sandwiched between the punch 5 and the die 6, and the weld nut press-fitting hole 21 is formed by a general punching process. Here, since the hole diameter of the weld nut press-fitting hole 21 is larger than the outer diameter dimension of the weld nut main body 41, the hole diameter by punching can be set larger than the plate thickness of the body member 2. That is, since the ratio of the diameter to the length of the punch 5 of the press can be made sufficiently large, the punch 5 does not have insufficient strength.

  Generally, when a thick metal plate is punched, the cross section of the punched hole becomes a taper shape. However, by setting the clearance C between the punch 5 and the die 6 larger than that during normal punching, welding is performed. The taper-shaped inclination of the nut press-fitting hole 21 can be set large.

(b) Press-fit process In the press-fit process, the body member 2 is turned upside down with respect to the time of the drilling process, and the weld nut 4 is press-fit into the weld nut press-fit hole 21 until the weld nut 4 is completely within the body member 2. At this time, since the weld nut press-fitting hole 21 is set to have a smaller diameter than the outer diameter of the projection protrusion 42 of the weld nut 4, the outer periphery of the four projection protrusions 4 is crushed inward, and the weld nut press-fitting hole 21 will be in close contact with the inner periphery of 21.

(c) Welding process In the welding process, the upper electrode 7 is disposed on the projection projection 42 side of the weld nut body 41 and the lower electrode 8 is disposed on the opposite side, and the electrodes 7 and 8 are energized. An insulator 81 is disposed at a portion of the lower electrode 8 that contacts the welding nut 4. When the electrodes 7 and 8 are energized, the projection protrusion 42 is melted due to the concentration of current, and is joined to the inner peripheral surface of the weld nut press-fitting hole 21 to form a joint 42a.

  As described above, the four projection projections 4 are in a state in which the outer peripheral portion is crushed inward and is in close contact with the inner periphery of the weld nut press-fitting hole 21, so that the welding strength of the joint portion 42a can be ensured and at the time of welding. Non-conduction can be prevented. Further, since only the four projection protrusions 4 are in contact with the weld nut press-fitting hole 21 and the weld nut main body 41 is not in contact with the weld nut press-fitting hole 21, the welding current from the weld nut main body 41 to the body member 2 is reduced. There is no leakage, and only the projection protrusion 4 can be reliably welded.

[Reduced man-hours and manufacturing costs]
In sheet metal press forming, in general, forming a small diameter hole with a thickness of less than the plate thickness (or 80% or less of the plate thickness) increases the ratio of the length of the press to the punch diameter. There is a risk of breakage, and laser processing and machining are necessary especially for plate thicknesses (t3.2 or more). However, in a method using laser processing or machining, it is necessary to perform laser processing or machining in a separate process after sheet metal press processing of a metal plate, resulting in an increase in man-hours and cost.

  On the other hand, as a method for generating a screw hole in a metal plate, a method using machining, a weld nut, and a press-fit nut (curry nut) is known. However, in machining, as described above, man-hours increase and cost increases. There was a problem of inviting. In addition, with welded nuts and press-fit nuts, the entire nut protrudes from the surface of the metal plate. When attaching a harness clip, resin cover, etc. to this nut, a structure to avoid the nut is required. There was a problem of losing the layout.

  On the other hand, in the small-diameter hole structure of the metal plate of Example 1, the welding nut 4 is press-fitted into a hole (welding nut press-fitting hole 21) formed by pressing at an appropriate tightening allowance, and at the press-fitting portion by projection welding. A projection projection 42 is welded. For this reason, since the hole in the body member 2 can be made to have the outer diameter of the welding nut 4, the hole diameter is large, the degree of freedom in selecting a drilling method is increased, and it can be formed inexpensively by press molding. it can. For example, when a welding nut is provided outside (on the one surface side) of the body member, the punch hole diameter is substantially the female screw diameter, so the hole diameter is small. In Example 1, however, the punch hole diameter is reduced as described above. Can be bigger.

  In Example 1, commercially available square welding nuts 1C type and 1D type specified in JIS standards are used as the welding nut 4. That is, since a small hole structure can be formed by diverting a highly circulated JIS standard product, the manufacturing process of the welding nut 4 is unnecessary, and the manufacturing cost can be further reduced.

[Layout improvement effect]
In Example 1, since the welding nut 4 has a height dimension shorter than the thickness of the body member 2, the protruding amount of the welding nut 4 on the resin cover 1 attachment side surface of the body member 2 is zero, and space saving is achieved. The attachment (resin cover 1) can be fixed, and the layout of the product is not impaired.

[Securing removal load by taper section]
In the method for forming a small-diameter hole in the metal plate according to the first embodiment, the weld nut press-fitting hole 21 has a taper shape whose axial cross section is reduced in diameter toward the press-fitting direction of the weld nut 4 (right direction in FIG. 1). ing. The opening edge of the weld nut press-fitting hole 21 on the weld nut 4 press-fitting side (left side in FIG. 1) is set to a diameter larger than the outer diameter of the weld nut main body 41 and smaller than the projection protrusion 42. The opening edge on the mounting surface side (the right side in FIG. 1) is set to have a diameter larger than the outer diameter of the weld nut body 41 and smaller than the projection protrusion 42. Therefore, the removal load of the press-fitted weld nut 4 is increased, the mounting strength of the resin cover 1 can be secured, and the press-fitting work of the projection protrusion 42 into the weld nut press-fit hole 21 can be facilitated.

Next, the effect will be described.
The small-diameter hole structure of the metal plate of Example 1 has the following effects.

  (1) A weld nut press-fitting hole 21 having an inner diameter that is larger than the outer diameter dimension of the weld nut body 41 and less than the outer diameter dimension of the projection projection 42 of the weld nut 4 is formed in the body member 2. The projection projection 42 was welded in the hole 21 in a press-fit state, and the entire height of the weld nut main body 41 was set in the weld nut press-fit hole 21. Thereby, the small diameter hole (internal thread 41a) can be provided in the body member 2 while suppressing the manufacturing cost and without impairing the layout of the product.

  (2) Since the welding nut 4 has a height direction dimension shorter than the thickness of the body member 2, the attachment (resin cover 1) can be fixed in a space-saving manner, and the layout of the product is not impaired. .

  (3) Since the axial cross-sectional shape of the weld nut press-fitting hole 21 has a tapered shape that decreases in diameter in the press-fitting direction of the weld nut 4, the removal load of the press-fitted weld nut 4 is increased, and the resin cover 1 Mounting strength can be secured.

  (4) a drilling step of forming a weld nut press-fitting hole 21 in the body member 2 having an inner diameter that is larger than the outer diameter dimension of the weld nut body 41 and less than the outer diameter dimension of the projection protrusion 42 of the weld nut 4; A press-in process for press-fitting the projection protrusions 42 into the weld nut press-fit holes 21 until the projection protrusions 42 and the height of the weld nut main body 41 are all located in the weld nut press-fit holes 21, and the projection protrusions 42 into the weld nut press-fit holes 21. And a welding process for welding. Thereby, a small diameter hole (internal thread 41a) can be provided in the metal plate while suppressing the manufacturing cost and without impairing the layout of the product.

(Other examples)
Although the best mode for carrying out the present invention has been described based on the first embodiment, the specific configuration of the present invention is not limited to the first embodiment and does not depart from the gist of the present invention. Such design changes are included in the present invention.

  For example, in Example 1, although the example which used the square welding nut 1C type and 1D type of JIS standard "JIS B 1196: 2001" as a welding nut was shown, even if it uses a hexagonal welding nut and a welding nut of another shape, it is used. Good. Further, the shape of the weld nut press-fitting hole is not limited to a circle, and may be changed according to the shape of the weld nut. For example, in the case of a square weld nut press-fitting hole, the outer shape of the weld nut refers to the length from the center of the weld nut to the corner of the square hole.

  Moreover, in Example 1, although the example which embedded the welding nut completely in the metal plate was shown, it is good also as a structure which made a part of welding nut main body protrude from the one surface side of a metal plate. In this case, the degree of freedom in layout is somewhat inferior to the configuration of Example 1, but the ratio of the diameter to the length of the punch of the press can be made sufficiently large. There is an effect that a hole can be formed.

  In the first embodiment, an example in which a resin cover is attached to a metal plate is shown. However, the small-diameter hole structure in the first embodiment is not limited to the attachment of a cover and a trim part, and a harness clip (wiring clamp) for harness bundling is attached to the vehicle body. It can also be used as a mounting hole to be attached to.

It is a longitudinal cross-sectional view which shows the resin cover attachment part of the vehicle body body to which the small diameter hole structure of the metal plate of Example 1 is applied. It is explanatory drawing which shows the small diameter hole formation method of the metal plate of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resin cover 2 Body member 21 Weld nut press-fit hole 3 Bolt 4 Weld nut 41 Weld nut main body 42 Projection protrusion 42a Joint part 5 Punch 6 Die 7 Upper electrode 8 Lower electrode 81 Insulator

Claims (4)

The metal plate is formed with a weld nut press-fit hole that is larger than the outer diameter dimension of the weld nut body and has an inner diameter equal to or smaller than the projection projection outer diameter dimension of the weld nut,
The projection projection is welded to the weld nut press-fitting hole in a press-fitted state,
A small-diameter hole structure for a metal plate, which is set so that at least a part of the height of the weld nut body is positioned in the weld nut press-fitting hole. In the small diameter hole structure of the metal plate according to claim 1,
The weld plate has a small-diameter hole structure for a metal plate, wherein the weld nut has a height direction dimension shorter than a thickness of the metal plate. In the small-diameter hole structure of the metal plate according to claim 1 or 2,
A small-diameter hole structure of a metal plate, wherein an axial cross-sectional shape of the weld nut press-fitting hole has a tapered shape whose diameter decreases in a press-fitting direction of the weld nut. A hole forming step for forming a weld nut press-fitting hole having an inner diameter that is larger than the outer diameter dimension of the weld nut main body and less than the projection projection outer diameter dimension of the weld nut on the metal plate;
A press-fitting step of press-fitting the projection protrusion into the weld nut press-fit hole until at least a part of the height of the projection protrusion and the weld nut main body is located within the weld nut press-fit hole;
A welding step of welding the projection protrusion to the inner periphery of the weld nut press-fitting hole;
A method for forming a small-diameter hole in a metal plate.

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