JP2005264996A - Sheet metal made female screw member, burring punch and die for manufacturing the same, and image forming device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet metal female screw preventing lowering of a male resisting break torque value at a screw fastening part where a hole diameter of a partner member is larger than an outer diameter of a cylindrical portion of the sheet metal female screw, when the sheet metal female screw and the male screw manufactured by burring machining are used for fastening the partner member. <P>SOLUTION: In the sheet metal female screw 1, the cylindrical portion 3 is projected and formed on a metallic plate 2 by burring machining, and a uniform inner diameter portion 4 in the cylindrical portion 3 is used as the female screw. The metallic plate 2 and the metallic plate side opening portion 9 of the cylindrical portion 3 are connected with each other through a part 7 larger than the outer diameter of the cylindrical portion disposed at a projecting base portion of the cylindrical portion 3, and projecting to the outside of an outer peripheral surface 6 of the cylindrical portion 3 and to the cylindrical portion projecting side, when viewing a projecting side opening portion of the cylindrical portion 3 from right above. The metallic plate side opening portion 9 of the cylindrical portion is continuously arranged from a metallic plate surface 8 on the opposite side to the projecting direction of the cylindrical portion 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a female screw made of sheet metal, and more specifically, manufactured from a metal plate by burring processing, and when another mating member is fastened using a male screw, the cylindrical portion is not easily deformed by being protruded from the metal plate, The present invention relates to a sheet metal female screw whose breakdown torque value does not decrease, a burring punch and a die for manufacturing the sheet metal female screw, and an image forming apparatus using the sheet metal female screw.

Conventionally, after piercing a thin metal plate using a burring punch, continuous squeezing is performed, so that a cylindrical burring (fitting, hole flange) is formed on the metal plate without producing metal debris in one step. A burring process to be formed is known (see, for example, Patent Document 1), and in an image forming apparatus such as a copying machine or a printer, it is known to form a female thread for fastening its constituent elements by a burring process. (For example, refer to Patent Document 2).
JP-A-9-201627 JP-A-11-51029

9A and 9B are diagrams showing a conventional sheet metal female screw, FIG. 9A is a plan view, and FIG. 9B is a partially sectional front view.
A conventional sheet metal female screw 101 is formed by projecting and forming a cylindrical portion 103 on a thin metal plate 102 by burring processing using a burring punch, and causing the uniform inner diameter portion 104 of the cylindrical portion 103 to function as a female screw. Although it has features such as simple structure, light weight, suitable for mass production, and low cost, it has the following two problems.

As a first problem, when the hole diameter of the fastening partner member with respect to the female screw is larger than the outer diameter of the cylindrical portion that becomes the female screw, the female screw breaking torque value, that is, the female screw can withstand without being destroyed to the maximum extent. Torque value decreases.
Specifically, when a M3 or M4 female screw is formed using a metal plate having a plate thickness of 1.2 mm or less, and screw fastening is performed using the M3 or M4 male screw, a conventional sheet metal is used. As shown in FIG. 9, the female screw 101 has a configuration in which a cylindrical portion 103 is extruded and formed by burring, and the uniform inner diameter portion 104 in the cylindrical portion 103 is applied as a female screw.

FIG. 10 is a cross-sectional view showing a screw fastening location when fastening a male screw with another component using the sheet metal female screw shown in FIG. 9, and FIG. 11 shows the male screw at the screw fastening location shown in FIG. It is sectional drawing which shows the state at the time of overfastening.
In the screw fastening portion shown in FIG. 10, the diameter of the hole 122 of the mating member 121 for the purpose of allowing a positional deviation between the sheet metal female screw 101 and the hole 122 formed in the mating member 121 due to the influence of the stacked dimensional accuracy between the members. When the screw fastening is carried out at a location where the outer diameter of the cylindrical portion 103 is larger than the outer diameter of the cylindrical portion 103, the protruding portion 105 of the cylindrical portion 103 applied as a female screw, that is, the bent portion where the metal plate 102 and the cylindrical portion 103 are connected to each other is formed. A phenomenon occurs in which the deformation 106 occurs as shown by the dotted line by being drawn into the hole 122 side of the mating member 121.

The cause of the deformation 106 will be described.
At the screw fastening location, a compressive stress F in a direction of pulling from the screw thread formed on the male screw 131 toward the head side of the male screw 131 acts on the screw thread portion of the female screw formed on the uniform inner diameter portion 104. The compressive stress F increases as the tightening torque T applied to the male screw 131 is increased.

  Here, at the screw fastening portion where the diameter of the hole 122 of the mating member 121 is larger than the outer diameter of the cylindrical portion 103, the protruding portion 105 of the cylindrical portion 103 serving as a female screw and the head 132 of the male screw 131. Since there is a space formed by the hole 122 between them, when the tightening torque T increases and the compressive stress F acting on the female screw increases, the protruding part 105 of the cylindrical part 103 is joined to the protruding part 105 of the mating member 121 at the time of fastening. Bending stress f with the surface side ridge line as a fulcrum 107 acts, and the protruding portion 105 of the cylindrical portion 103 undergoes deformation 106 in the direction in which it is pulled into the hole 122 side of the mating member 121. The deformation of the protruding portion 105 of the cylindrical portion 103 is more easily deformed because the fulcrum 107 of the bending stress f is separated as the hole 122 of the mating member 121 becomes larger than the outer diameter of the cylindrical portion 103. Further, as the plate thickness of the metal plate 102 constituting the sheet metal female screw 101 is reduced, the bending stress value of the protruding portion 105 of the cylindrical portion 103 is decreased, so that the metal plate 102 is easily deformed.

In such deformation of the protruding portion 105 of the cylindrical portion 103, the metal plate side opening 108 of the cylindrical portion 103 serving as a female screw is disposed on the same horizontal plane as the fulcrum 107 of the bending stress f. The metal plate side opening 108 is deformed 106 so that its diameter increases when it is deformed in the direction of being pulled toward the hole 122 side of the counterpart member 121. The thread of the female thread formed on the inner diameter of the cylindrical part 103 corresponding to the protruding part 105 of the cylindrical part 103 due to this bulging phenomenon is in close contact with the thread of the male thread 131 as shown in the circular part of FIG. As a result, the number of effective threads of the female screw formed in the cylindrical portion 103 is reduced.
For these reasons, in the conventional sheet metal female screw, the female screw breaking torque resistance value of the female screw is reduced at the screw fastening location where the hole diameter of the fastening partner member is larger than the outer diameter of the cylindrical portion. Yes.

As a second problem, in the conventional sheet metal female screw, the number of threads of the female screw cannot be effectively formed over the entire height of the cylindrical portion, and the female screw breaking torque value decreases.
As shown in FIG. 9, when the cylindrical portion 103 is extruded and formed on the thin metal plate 102 by burring, the opening on the metal plate side of the cylindrical portion 103 has an R shape 109. Since the inner diameter portion of the cylindrical portion 103 having the R shape 109 does not become the uniform inner diameter portion 104, the thread of the effective female screw cannot be obtained at this location. Since the R shape 109 increases as the plate thickness t of the cylindrical portion 103 increases, the number of effective female threads obtained in the cylindrical portion 103 decreases as the thickness of the cylindrical portion 103 increases.
When the number of effective female threads is reduced in this way, the internal thread strength decreases, leading to a decrease in the internal thread breaking torque value.

As described above, the sheet metal female screw 101 according to the prior art has a condition in which the resistance value of the female screw breaking torque is reduced. Therefore, in a product to which this sheet metal female screw is applied, when tightening with a specified tightening torque in mass production assembly work, Failure to break the female screw is likely to occur.
Currently, the response to mass production assembly work where such internal thread breakage occurs is to increase the thickness of the metal plate to improve the bending stress value of the protruding part of the cylindrical part, or tighten it in mass production assembly work. Although this is dealt with by the torque value lowering management, each countermeasure has a major drawback.

The former handling method has the disadvantages that the amount of material used increases as the plate thickness increases, resulting in an increase in material costs and an increase in product weight.
In the latter method, it is necessary to individually set the tightening torque for each fastening point where the internal thread breakage occurred. Therefore, in the actual screw fastening work site, it is necessary to prepare and work a dedicated tightening tool for each fastening point. In addition, the operator must use different tools for each fastening portion, and the assembly workability is significantly hindered.

  The present invention was made to solve the problems of the prior art, and in the female metal screw of the invention according to claims 1 to 3, the hole diameter of the fastening counterpart member is that of the cylindrical portion of the female metal screw. The object is to prevent the male screw breaking torque value from being lowered at a screw fastening portion having a diameter larger than the outer diameter.

  The female metal screw of the inventions according to claims 4 and 5 is such that the number of threads of the effective female screw is reduced due to the R shape formed in the opening on the metal plate side of the cylindrical portion by performing burring, and the male screw breaking torque resistance value The purpose is to prevent the decrease.

  The invention according to claim 6 is to provide a burring punch and die capable of forming the sheet metal female screw according to claims 4 and 5 without deteriorating productivity.

  Further, the invention according to claim 7 is to obtain an image forming apparatus that performs screw fastening to which the female screw according to claims 1 to 5 is applied, thereby preventing the female screw from being destroyed in mass production assembly work. The purpose is to prevent an increase in material cost and an increase in product weight due to the increase in the thickness of the plate being performed, and to prevent an assembly failure due to a tightening torque value lowering management.

  The invention of claim 1 of the present invention is a sheet metal female screw in which a cylindrical part is extruded and formed on a metal plate by burring, and the uniform inner diameter part of the cylindrical part is used as a female screw. The metal plate side opening has a shape larger than the outer diameter of the cylindrical portion disposed at the protruding source portion of the cylindrical portion when the protruding side opening of the cylindrical portion is viewed from directly above, and the cylindrical portion The metal plate-side opening of the cylindrical portion is connected to the outer side of the outer periphery of the metal plate and protrudes toward the cylindrical portion protruding side. It is characterized by being arranged continuously.

  According to a second aspect of the present invention, in the female metal screw according to the first aspect, when the protruding side opening of the cylindrical portion is viewed from directly above, the outer portion of the cylindrical portion arranged at the protruding source portion of the cylindrical portion is arranged. The shape portion that is larger than the diameter and that protrudes outward from the outer periphery of the cylindrical portion and toward the protruding portion of the cylindrical portion is a tapered shape that opens from the protruding portion of the cylindrical portion toward the metal plate. And

  According to a third aspect of the present invention, in the female metal screw according to the first or second aspect, the cylindrical portion disposed at a protruding source portion of the cylindrical portion when the protruding side opening of the cylindrical portion is viewed from directly above. The position of the connecting portion between the shape portion that is larger than the outer diameter of the cylindrical portion and that protrudes outward from the outer periphery of the cylindrical portion and protrudes toward the cylindrical portion and the metal plate surface opposite to the protruding direction of the cylindrical portion Is outward from the position of the hole of the fastening member.

  According to a fourth aspect of the present invention, in the female metal screw according to any one of the first to third aspects, the cylindrical portion is larger in shape than an outer diameter of a cylindrical portion disposed at a protruding portion of the cylindrical portion, and the cylindrical portion An inner diameter side connecting corner of the cylindrical portion with a shape portion protruding outward from the outer periphery of the cylindrical portion and protruding toward the cylindrical portion has a concave shape on the entire circumference of the connecting corner.

  According to a fifth aspect of the present invention, in the female metal screw according to the fourth aspect, the concave cross-sectional shape has an inclined side that is obliquely connected to the inner diameter side of the cylindrical portion, and the inclination of the inclined side is The inner diameter side of the cylindrical portion forms a side that is inclined toward the protruding portion side of the cylindrical portion.

  According to a sixth aspect of the present invention, in the burring punch and die for manufacturing the sheet metal female screw according to claim 4 or 5 by burring, the clearance during processing of the burring punch and the die is the shape of the female metal screw. It is characterized by that.

  A seventh aspect of the invention is an image forming apparatus using screw fastening to which the sheet metal female screw according to any one of the first to fifth aspects is applied.

In the invention according to claim 1, the bending stress f acts on the protruding portion of the cylindrical portion at the screw fastening portion where the hole diameter of the fastening partner member is larger than the outer diameter of the cylindrical portion of the sheet metal screw. Even if deformation of the fastening partner member in the hole direction occurs in the protruding shape portion of the portion, the opening on the metal plate side of the cylindrical portion is on the opposite side of the deformation direction due to the stress from the horizontal plane that is the fulcrum of the bending stress f. Since it is configured to be arranged, the action of reducing the opening to the inner diameter side works, and even if the protruding shape part of the cylindrical part is deformed by this action, the thread of the female screw formed on the inner diameter of the cylindrical part Intimate engagement with the thread of the male thread is maintained.
In addition, when the action of reducing the opening on the metal plate side of the cylindrical part works, the inner diameter of the cylindrical part is filled with the thread of the male screw, so there is no space for deformation to the inner diameter side, so it is difficult to deform. .
Therefore, at the screw fastening portion where the hole diameter of the fastening partner member is larger than the outer diameter of the cylindrical portion, it is possible to prevent the decrease in the effective number of female threads due to the deformation of the protruding portion of the cylindrical portion as in the prior art. It is possible to prevent a decrease in the female screw breaking torque value.

  In the invention according to claim 2, the shape portion which is larger than the outer diameter of the cylindrical portion arranged at the protruding portion of the cylindrical portion and protrudes outward from the outer periphery of the cylindrical portion and toward the protruding portion of the cylindrical portion is Since the taper shape opens from the protruding part toward the metal plate, it can be processed with the same number of processing steps as normal burring processing, and the internal thread shape with good workability is obtained without increasing the part processing cost. It becomes possible.

  The invention according to claim 3 is a shape portion that is larger than the outer diameter of the cylindrical portion disposed in the protruding base portion of the cylindrical portion, and that protrudes outward from the outer periphery of the cylindrical portion and toward the protruding portion of the cylindrical portion; Since the position of the connecting portion between the metal plate surface opposite to the direction in which the cylindrical portion protrudes is outward from the position of the hole of the fastening partner member, the fulcrum of bending stress f acting on the protruding shape portion of the cylindrical portion However, the connecting portion becomes larger than the diameter of the hole of the mating member, and the bending stress value of the protruding portion of the cylindrical portion is not affected by the size of the hole diameter of the mating member. Therefore, the influence of the male screw breaking torque value on the size of the hole diameter of the mating member is eliminated, and stable tightening torque management becomes possible.

  The invention which concerns on Claim 4 is a shape larger than the outer diameter of the cylindrical part arrange | positioned at the cylindrical part and the protrusion origin part of a cylindrical part, and the shape part protruded outward from the outer periphery of the said cylindrical part, and the cylindrical part protrusion side Since the inner diameter side connecting corner of the cylindrical portion has a concave shape on the entire circumference of the connecting corner, it is possible to flow the material of the concave portion to the inner diameter side of the cylindrical portion, which is a conventional example. It is possible to obtain a uniform inner diameter portion even in a region where the R shape is formed and the uniform inner diameter cannot be obtained, and it is possible to achieve an increase in the number of threads of the female screw, which is more resistant to male screws than the conventional sheet metal female screws. It becomes possible to improve.

  In the invention according to claim 5, the concave cross-sectional shape has an inclined side that is obliquely connected to the inner diameter side of the cylindrical portion, and the inclination of the inclined side is such that the inner diameter side of the cylindrical portion is on the protruding portion side of the cylindrical portion. Since the inclined side is formed, it is possible to flow the material of the concave portion to the metal plate side opening side of the cylindrical portion, so that a wide area forming a uniform inner diameter portion can be obtained. It is possible to improve the internal thread breaking torque resistance.

  According to a sixth aspect of the present invention, in the burring punch and die for manufacturing the sheet metal female screw according to claim 4 or 5 by burring, the clearance during processing of the burring punch and the die is the shape of the female metal screw. Therefore, by performing burring processing using this punch and die, it is possible to form a female screw shape having a concave shape with the same number of steps as in the conventional burring processing, and it is possible to avoid an increase in parts processing costs. .

  The invention according to claim 7 is an image forming apparatus in which the screw fastening to which the sheet metal female screw according to any of claims 1 to 5 is applied is used. It is possible to prevent internal thread breakage during work, and it is possible to prevent the increase in material cost and the increase in product weight due to the thickening of the plate thickness that has been implemented in the prior art, and the hindrance to assembly by the tightening torque value lowering management. Become.

In the present invention, when fixing another mating member using a sheet metal female screw and a male screw manufactured by burring, the hole diameter of the mating member is larger than the outer diameter of the cylindrical portion of the sheet metal female screw. It relates to a sheet metal internal thread where the internal thread breaking torque value does not decrease at the screw fastening location, and the configuration for that purpose is to form a cylindrical part on a metal plate by burring, and to form a uniform inner diameter in the cylindrical part The metal plate and the metal plate side opening of the cylindrical portion of the sheet metal female screw that uses the portion as the female screw, when the protruding side opening of the cylindrical portion is viewed from directly above, the protruding portion of the cylindrical portion The cylindrical portion is arranged to be larger than the outer diameter of the cylindrical portion, and is connected to the outer side of the outer periphery of the cylindrical portion and connected through a shape portion protruding to the cylindrical portion protruding side. Genus plate side openings, in which as the cylindrical portion is arranged continuously from the metal plate surface of the protruding direction opposite side.
Hereinafter, the sheet-metal internal thread of the Example of this invention is demonstrated based on FIGS.

A sheet metal female screw according to Example 1 of the present invention will be described.
1A and 1B are diagrams showing a sheet metal female screw of Example 1, FIG. 1A is a plan view, and FIG. 1B is a partially sectional front view.
A sheet metal female screw 1 of Example 1 is formed by projecting and forming a cylindrical portion 3 on a thin metal plate 2 by burring, and applying a uniform inner diameter portion 4 in the cylindrical portion 3 as a female screw. 2 and the metal plate side opening portion 5 of the cylindrical portion 3 when the protruding side opening portion of the cylindrical portion 3 is viewed from directly above (see FIG. 1 (A)), It is larger than the outer peripheral surface 6 of the part 3 and is disposed through a protruding shape part 7 protruding in the protruding direction of the cylindrical part 3, and the metal plate side opening 5 of the cylindrical part 3 is in the protruding direction of the cylindrical part 3. Is a sheet metal female screw having a configuration arranged on the cylindrical portion protruding side from the opposite metal plate surface 8. (Claim 1)

  Here, in the sheet metal female screw 1 shown in FIG. 1, the protruding portion 7 protruding from the outer peripheral surface 6 of the cylindrical portion 3 located at the protruding source portion of the cylindrical portion 3 and continuing to the metal plate 2 is directed toward the metal plate 2. The protruding portion 7 has a truncated cone shape.

2A and 2B are views showing a modification of the sheet metal female screw of the first embodiment, in which FIG. 2A is a plan view and FIG. 2B is a partially sectional front view.
The sheet metal female screw 1 of this modified example is located at the projecting base portion of the cylindrical portion 3, and the projecting shape portion 7 projecting from the outer peripheral surface 6 of the cylindrical portion 3 and continuing to the metal plate 2 is directed toward the surface of the metal plate 2. The protruding portion 7 has a truncated pyramid shape. (Claim 2)

  As shown in FIGS. 1 and 2, if the protruding portion 7 protruding from the outer peripheral surface 6 of the cylindrical portion and continuing to the metal plate 2 is a truncated cone or a truncated pyramid taper, the same processing as a normal burring process is performed. It becomes possible to process with man-hours, resulting in a shape with good workability that does not cause an increase in parts processing costs.

Next, an embodiment of screw fastening using the sheet metal female screw of Example 1 will be described.
FIG. 3 is a cross-sectional view showing a screw fastening location when the mating member and the male screw are fastened using the sheet metal female screw of the first embodiment.
As described in the problem of the prior art, a compressive stress F in a direction of pulling from the thread of the male screw to the male screw head side acts on the screw thread portion of the female screw (see FIG. 10). At a screw fastening location where the hole 22 of the mating member 21 has a larger diameter than the outer peripheral surface 6 of the cylindrical portion 3 of the female metal screw 1, a space is formed between the protruding portion 7 of the cylindrical portion 3 and the head 32 of the male screw 31. Therefore, when the compressive stress F acting on the female screw formed in the uniform inner diameter portion 4 increases, the bending stress f acts on the protruding portion 7 continuous from the cylindrical portion 3. Here, in the sheet metal female screw 1 of the present invention, the metal plate side opening 9 of the cylindrical portion 3 serving as the female screw is disposed on the cylindrical portion protruding side from the metal plate surface 8 opposite to the cylindrical portion protruding direction. For this reason, it becomes the structure arrange | positioned on the opposite side to the deformation | transformation direction by stress from the horizontal surface used as the fulcrum 10 of bending stress.

  In the configuration of the screw fastening portion shown in FIG. 3, when deformed by the bending stress f, the protruding portion 7 of the cylindrical portion 3 is indicated by a dotted line toward the inner diameter side of the cylindrical portion 3 in the opening 9 on the metal plate side of the cylindrical portion 3. The action of deforming works. By this action, even if the protruding portion 7 of the cylindrical portion 3 is deformed, the female thread formed on the inner diameter of the cylindrical portion 3 and the thread of the male screw 31 are kept in close contact with each other. In addition, when the action of reducing the metal plate side opening 9 of the cylindrical portion 3 to the inner diameter side works, the inner diameter of the cylindrical portion 3 is filled with the thread of the male screw 31, so that the space deformed to the inner diameter side. Since there is no, there is an effect that it is difficult to deform.

  Thereby, in the screw fastening location where the diameter of the hole 22 of the counterpart member 21 is larger than the outer diameter of the cylindrical portion 3, the deformation 106 of the protruding portion 105 (see FIG. 10) of the cylindrical portion 3 as in the prior art. According to (see FIG. 10), it is possible to prevent the number of effective threads of the female screw 131 as shown in the circle of FIG. 11 from decreasing, and to prevent a decrease in the male screw breaking torque value of the female screw.

FIG. 4 is a cross-sectional view of a fastening state different from FIG. 3 showing screw fastening locations when the mating member and the male screw are fastened using the sheet metal female screw 1 of the first embodiment.
The fastening state shown in FIG. 4 is different from the fastening state shown in FIG. 3 in that the fulcrum of the bending stress f acting on the protruding source portion of the cylindrical portion 3 is on the larger diameter side than the counterpart hole diameter.
In the female metal screw of Example 1 that can obtain the effects described with reference to FIG. 3, a connection portion between the inner surface of the protruding portion 7 of the cylindrical portion 3 and the metal plate surface 8 opposite to the protruding direction of the cylindrical portion, That is, the position of the fulcrum 10 of the bending stress becomes larger than the diameter of the hole 22 of the counterpart member 21. (Claim 3)

  In the fastening state shown in FIG. 4, the fulcrum 10 of the bending stress f acting on the protruding shape portion 7 of the cylindrical portion 3 becomes a connection portion between the protruding shape portion 7 of the cylindrical portion 7 and the metal plate surface 8. Since it is outside the diameter, the bending stress value of the protruding portion 7 of the metal plate 2 and the cylindrical portion 3 is not affected by the size of the hole 22 of the counterpart member 21. As a result, the influence of the male screw breaking torque value on the diameter of the hole 22 of the mating member 21 is eliminated, and stable tightening torque management becomes possible.

Next, the female metal screw of Example 2 will be described.
FIG. 5 is a partial cross-sectional front view showing the sheet metal female screw of the second embodiment.
The sheet metal female screw of Example 2 is a metal plate 2 from the outer peripheral surface 6 of the cylindrical part 3 and the cylindrical part 3 located in the protrusion part of a cylindrical part with respect to the female metal screw of Example 1 shown in FIGS. A concave shape 11 is formed at the inner diameter side connection corner of the cylindrical portion 3 with the protruding shape portion 7 that continues toward the inner periphery of the connection corner. (Claim 4)

FIG. 6 is a partial cross-sectional front view showing a modification of the female metal screw of the second embodiment.
6, the concave shape 11 has an inclined side that is obliquely connected to the inner diameter side of the cylindrical portion 3 in a cross-sectional shape passing through the central axis of the cylindrical portion 3, and The inclination indicates that the inner diameter side of the cylindrical portion 3 forms a side 12 that is inclined toward the protruding shape portion 7 side of the cylindrical portion 3. (Claim 5)

Next, the burring punch and die used when manufacturing the sheet metal female screw of Example 2 shown in FIGS. 5 and 6 by burring will be described.
7 and 8 are views showing the relationship between the burring punch and die for manufacturing the sheet metal female screw of the present invention shown in FIGS. 5 and 6 and the sheet metal female screw.
Burring is performed on the thin metal plate, and the burring punch and die clearance C when the burring is completed have the same shape as the outer shape of the sheet metal female screw shown in FIGS. (Claim 6)

  The concave shape 11 of the sheet metal female screw of Example 2 shown in FIGS. 5 and 6 is a shape to which the shapes of the burring punch 41 and the die 44 shown in FIGS. 7 and 8 are transferred in burring. The burring punch 41 has convex shapes 42 and 43 corresponding to the concave shape 11. In the burring process, the punch convex shape pressurizes the periphery of the opening on the metal plate side of the cylindrical portion, and the concave shape 11 is formed. It becomes possible to flow the material to the inner diameter side of the cylindrical portion 3. Accordingly, in the conventional sheet metal female screw shown in FIG. 9, it is possible to obtain a uniform inner diameter portion even in a region where the R shape 109 is formed and the uniform inner diameter cannot be obtained.

  In particular, the concave portion 11 shown in FIG. 6 has an inclined side that is obliquely connected to the inner diameter side of the cylindrical portion in a cross-sectional shape passing through the central axis of the cylindrical portion 3, and the inclination of the inclined side is cylindrical on the inner diameter side of the cylindrical portion. By forming the side 12 that is inclined toward the protruding shape portion side of the portion 3, it is possible to cause the material of the portion that becomes the concave shape 11 to flow toward the metal plate side opening 9 side of the cylindrical portion 3. Thereby, the area | region which makes the more uniform internal diameter part 4 will be obtained.

  With the above effects, in the conventional example as shown in FIG. 9, it is possible to obtain a uniform inner diameter portion even in a region where the R shape 109 is formed and a uniform inner diameter cannot be obtained, thereby increasing the number of threads of the female screw. Assurement can be achieved, and the resistance to internal thread breaking torque can be improved compared to the female thread of the prior art.

  Further, as described above, by using the burring punch 41 and the die 44 shown in FIGS. 7 and 8 in the burring process, it is possible to form the sheet metal female screw having the concave shape 11 with the same number of steps as the conventional burring process. It is possible to avoid an increase in parts processing costs.

  In the image forming apparatus using the screw fastening to which the sheet metal female screw according to the first and second embodiments can be obtained, the female screw breaking torque value can be prevented from being lowered. It is possible to prevent breakage, and it is possible to prevent an increase in material cost due to the thickening of the member to be fastened, which has been performed in the prior art, an increase in product weight, and a hindrance to assembly by tightening torque value management. (Claim 7)

It is a figure which shows the sheet-metal female screw of Example 1, FIG. 1 (A) is a top view, FIG.1 (B) is a partial cross section front view. FIG. 2A is a plan view and FIG. 2B is a partial cross-sectional front view of a modification of the sheet metal female screw of the first embodiment. It is sectional drawing which shows the screw fastening location at the time of fastening a mating member and a male screw using the sheet-metal female screw of Example 1. FIG. It is sectional drawing of the fastening state different from FIG. 3 which shows the screw fastening location at the time of fastening a mating member and a male screw using the sheet-metal female screw 1 of Example 1. FIG. It is a partial cross section front view which shows the sheet-metal female screw of Example 2. FIG. It is a partial cross section front view which shows the modification of the sheet-metal female screw of Example 2. FIG. It is a figure which shows the relationship between the burring punch and die which manufacture the sheet metal internal thread of this invention shown in FIG. 5, and a sheet metal internal thread. It is a figure which shows the relationship between the burring punch and die which manufacture the sheet metal internal thread of this invention shown in FIG. 6, and a sheet metal internal thread. It is a figure which shows the sheet metal female screw of a prior art, FIG. 9 (A) is a top view, FIG.9 (B) is a partial cross section front view. It is sectional drawing which shows the screw fastening location at the time of fastening another part and a male screw using the sheet-metal female screw shown in FIG. It is sectional drawing which shows the state at the time of fastening the male screw excessively in the screw fastening location shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sheet-metal female screw, 2 ... Metal plate, 3 ... Cylindrical part, 4 ... Uniform internal diameter part, 5 ... Metal plate side opening part of cylindrical part, 6 ... Outer peripheral surface of cylindrical part, 7 ... Projection shape part, 8 ... Cylindrical part Metal plate surface on the opposite side to the protruding direction of the part, 9 ... Metal plate side opening of the cylindrical part, 10 ... Bending point of bending stress, 11 ... Concave shape, 12 ... Inclined side, 21 ... Partner member, 22 ... Hole , 31 ... male screw, 32 ... head, 41 ... burring punch, 42, 43 ... convex shape, 44 ... die, F ... compressive stress, f ... bending stress.

Claims (7)

On a metal plate, a cylindrical part is extruded and formed by burring, and the uniform inner diameter part of the cylindrical part is used as a female thread.
When the metal plate and the opening on the metal plate side of the cylindrical portion are viewed from directly above the protruding side opening of the cylindrical portion, the outer diameter of the cylindrical portion arranged at the protruding source portion of the cylindrical portion It is connected via a shape part that is larger in shape and protrudes outward from the outer periphery of the cylindrical part and toward the cylindrical part protruding side, and the metal plate side opening of the cylindrical part has a direction in which the cylindrical part protrudes A sheet metal female screw, which is continuously arranged from the metal plate surface on the opposite side. In the female screw made of sheet metal according to claim 1,
When the protruding side opening of the cylindrical portion is viewed from directly above, the cylindrical portion is larger than the outer diameter of the cylindrical portion disposed at the protruding source portion of the cylindrical portion, and is outward from the outer periphery of the cylindrical portion and the cylindrical portion. The sheet metal female screw, wherein the shape portion protruding to the protruding side has a tapered shape that opens from the protruding portion of the cylindrical portion toward the metal plate. In the female metal screw according to claim 1 or 2,
When the protruding side opening of the cylindrical portion is viewed from directly above, the cylindrical portion is larger than the outer diameter of the cylindrical portion disposed at the protruding source portion of the cylindrical portion, and is outward from the outer periphery of the cylindrical portion and the cylindrical portion. A sheet metal, wherein the position of the connecting portion between the shape portion protruding to the protruding side and the metal plate surface opposite to the direction in which the cylindrical portion protrudes is more outward than the hole position of the fastening member. Made female screw. The sheet metal female screw according to any one of claims 1 to 3,
The cylindrical portion and the cylindrical portion having a shape larger than the outer diameter of the cylindrical portion arranged at the protruding portion of the cylindrical portion and protruding outward from the outer periphery of the cylindrical portion and toward the protruding portion of the cylindrical portion. An inner diameter side connection corner has a concave shape on the entire circumference of the connection corner. The female metal screw according to claim 4,
The concave cross-sectional shape has an inclined side that is obliquely connected to the inner diameter side of the cylindrical portion, and the inclination of the inclined side is a side where the inner diameter side of the cylindrical portion is inclined toward the protruding portion side of the cylindrical portion. A sheet metal female screw characterized by being formed. In the burring punch and die for manufacturing the sheet metal female screw according to claim 4 or 5 by burring,
A burring punch and die, wherein the clearance during processing of the burring punch and die is the shape of the female screw made of sheet metal.   An image forming apparatus using screw fastening to which the sheet metal female screw according to any one of claims 1 to 5 is applied.