JP2010264694A - Method of press-fitting insert fitting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press-fitting method of an insert fitting, which press-fits a resin without melting unnecessarily to obtain a sufficient fixed power when press-fitting the heated insert fitting into a hole of a crystalline thermoplastic resin product. <P>SOLUTION: A nut 1 is heated up to a melting temperature or more of the resin, and the press-fitting is temporarily stopped in a state that a part of the nut 1 is press-fitted into the hole 6 until the surface temperature of the nut 1 is decreased below the melting temperature. Thereafter, the press-fitting of the nut 1 to the hole 6 starts again to complete the press-fitting. Therefore, in the nut 1, the resin melts at a melting portion 8 in the surface side of the hole 6 and a part is press-fitted into the hole 6 without inclining and stops temporarily. By press-fitting the nut 1 in which the temperature lowers further into the hole 6 of the resin product 5, the nut 1 is press-fitted into the hole 6 in which the inner wall surface is softened without melting the resin of the inner wall surface of the hole 6 to finish the press-fitting. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for press-fitting an insert fitting that press-fits an insert fitting that has been heated and heated in a hole formed in a thermoplastic resin product.

  In order to couple a synthetic resin product (hereinafter simply referred to as a resin product) and other parts or structures, a screw hole may be provided in the resin product. However, when a bolt or the like is screwed directly into this screw hole, the screw surface of the screw hole is destroyed by the load applied through the bolt, or the screw and screw screw are loosened by creep, It is difficult to increase the screwing force between the bolt and the screw hole.

  Therefore, a nut or the like is inserted into a resin product, and a bolt is screwed onto the nut. The insertion method includes a method of inserting a nut into a mold during molding of a resin product, a method of bonding a nut to a hole of a resin product using an adhesion technique, a method of press-fitting a heated nut into a hole of a resin product, and the like. Can be mentioned. Each method has advantages and disadvantages, but the press-fitting method is the simplest method.

  The “insert press-fitting device” disclosed in Patent Document 1 is a fixing provided with a heating rod that heats an insert inserted into an embedding hole of a resin molded product, and a blowout port that blows out air together with a pressing portion that holds the insert. With a stick. According to this apparatus, the softened resin heated through the insert is quickly cooled by the air blown out from the outlet, and the time for solidifying the softened resin is shortened.

  In the “heat insert structure” disclosed in Patent Document 2, a counterbore portion is provided in a hole portion into which the insert metal fitting is press-fitted, and a chamfered portion is provided in an inner edge portion of the counterbore portion. A heated insert fitting is press-fitted into the hole having such a configuration. The resin that has been melted by the press-fitting to become burrs stays in the spot facing portion without protruding outside the hole portion.

  In the “press-fitting method” disclosed in Patent Document 3, a press-fitting jig to which a press-fitting member is attached is passed while contacting the inner wall surface of the hole of the injection molded product in a heated state, and the inner wall surface is in a molten state. A press-fitting member is press-fitted into the hole.

JP-A-6-31458 (see [Summary]) Japanese Patent Laid-Open No. 2002-1824 (see [Summary]) JP 2004-106082 A (see [Summary])

  Thermoplastic resins include crystalline resins and non-crystalline resins. Crystalline resins have the property of melting when the temperature rises above a certain temperature and the viscosity is significantly reduced, and this temperature is called the melting temperature. In addition, the amorphous resin does not have the property that the thermal properties clearly change at a certain temperature, unlike the crystalline resin. For this reason, since amorphous resins such as ABS and polystyrene gradually change from a softened state to a molten state, it can be said that the temperature management of the insert fitting when press-fitting the heated insert fitting is easy. However, since the viscosity of the crystalline resin immediately decreases after the melting temperature, a part of the crystalline resin may leak from between the insert metal and the resin due to the press fitting of the insert metal. In addition, since the crystalline resin has a large amount of shrinkage when solidified, a gap may be formed between the insert fitting and the resin. For this reason, it is not easy to obtain a strong fixing force of the press-fitted insert metal fitting to the crystalline resin product.

The method for press-fitting a heating insert fitting into a resin product disclosed in Patent Documents 1 to 3 is unquestioned with respect to the above-described problem relating to press-fitting into a crystalline resin product.
Furthermore, according to the press-fitting method of Patent Document 1, a time for heating the insert is required for each step of press-fitting, which causes a problem of time reduction. According to the press-fitting method of Patent Document 2, it is essential to provide a counterbore, and the finished product is subject to design restrictions. According to the press-fitting method of Patent Document 3, a through-hole through which a press-fitting jig can pass is essential for a resin product, and cannot be applied to a bottomed hole.

  The present invention has been made paying attention to such a problem, and its purpose is to make the resin unnecessary when press-fitting a heated insert metal fitting into a hole of a crystalline thermoplastic resin product. An object of the present invention is to provide a method for press-fitting an insert metal fitting which can be press-fitted without melting and can obtain a sufficient fixing force.

  In order to solve the above-mentioned problem, the invention of the press fitting method of the insert fitting according to claim 1 is the press fitting method of the insert fitting for press fitting the insert fitting heated in the hole of the thermoplastic resin product, wherein the thermoplastic resin is crystalline. When the insert metal fitting, which is a heat-resistant resin and heated above its melting temperature, is press-fitted into the hole, the heat of the insert metal fitting is transferred to the thermoplastic resin by press-fitting a part thereof, and the surface of the insert metal fitting The press-fitting is temporarily stopped until the temperature becomes lower than the melting temperature by the transmission, and then the press-fitting of the insert fitting into the hole is resumed to complete the press-fitting. The “hole” used herein means both a bottomed hole and a through hole.

  According to the invention described in claim 1, when the insert metal fitting is heated to a temperature higher than the melting temperature of the crystalline resin and the insert metal fitting is press-fitted into the hole of the resin product, The press-fitting was temporarily stopped until the surface temperature became lower than the melting temperature, and then the press-fitting of the insert fitting into the hole was resumed to complete the press-fitting. For this reason, the insert fitting is press-fitted into the hole while melting the resin on the surface side of the hole. While the press-fitting is temporarily stopped, the insert metal fitting is deprived because the heat melts and softens the resin, and the temperature becomes lower than the melting temperature of the resin. By further press-fitting the insert fitting whose surface temperature is lower than the melting temperature of the resin into the hole of the resin product, the insert fitting is pressed into the softened hole without melting the resin, thereby completing the press-fitting. Accordingly, the molten resin leaks out or contracts, and a gap is generated between the resin and the insert metal fitting, thereby preventing a reduction in the fixing force of the insert metal fitting to the resin product.

  According to a second aspect of the present invention, in the press-fitting method of the insert metal fitting according to the first aspect, the insert metal fitting is temporarily stopped after being press-fitted to a depth capable of self-supporting along the axial direction of the hole. It is a feature.

  According to the second aspect of the present invention, the press fitting is temporarily stopped after the insert fitting is pressed to a depth at which the insert fitting can be self-supported along the axial direction of the hole. For this reason, it is not necessary to support the insert fitting by the press-fitting device while the press fitting of the insert fitting is temporarily stopped. Therefore, the heat of the insert fitting can be efficiently transmitted to the resin without being wastedly transmitted to the press-fitting device, and the resin can be softened.

  The invention described in claim 3 is the press-fitting method of the insert metal fitting according to claim 1 or 2, wherein the insert metal fitting is a coupler for connecting the resin product and another component or structure. It is characterized by.

  According to the third aspect of the present invention, the coupler formed with the female screw or the male screw is press-fitted into the hole of the resin product as an insert fitting. For this reason, strong coupling | bonding of the resin product and other components or structures was attained by the coupling tool fixed to the resin product strongly.

  According to a fourth aspect of the present invention, there is provided the insert fitting press-fitting method according to any one of the first to third aspects, wherein the insert fitting is provided with a flange portion, while the surface of the hole of the resin product is provided. An enlarged diameter portion is provided on the side, and the flange portion is fitted to the enlarged diameter portion.

  According to the invention described in claim 4, the flange portion of the insert metal fitting is fitted to the enlarged diameter portion provided on the surface side of the hole of the resin product. For this reason, even if a burr generated when the insert metal fitting is press-fitted into the hole of the resin product leaks into the enlarged diameter part, the flange part covers the burr, so that the insert metal fitting for the resin product is not impaired. Can be press-fitted.

  The invention according to claim 5 is the press-fitting method of the insert metal fitting according to any one of claims 1 to 4, wherein the outer peripheral surface of the body portion of the insert metal fitting is an uneven surface. It is what.

  According to the invention described in claim 5, since the softened resin is in close contact with the uneven surface formed on the outer periphery of the body portion of the insert fitting, the insert fitting can be firmly fixed to the resin product.

  According to the present invention, the press-fitting of the heated insert metal fitting is temporarily stopped, while the heat of the insert metal fitting is transmitted to the resin product, and the inner wall surface of the hole of the resin product is softened, thereby reducing the temperature. The insert fitting that has been recombined with the press fitting can complete the press fitting without melting the resin. Therefore, it is possible to provide a method for press-fitting an insert fitting that provides a strong fixing force of the insert fitting to a resin product.

The perspective view which shows the relationship between the nut of this embodiment, and a resin product. (A) is sectional drawing which shows the nut of this embodiment, (b) is sectional drawing which shows the hole of a resin product. The partial cross section figure which shows the state where the nut was press-fitted into the hole of the resin product and stopped temporarily. The partial cross section figure which shows the state where the press injection of the nut with respect to the resin product was completed.

(Embodiment)
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described with reference to FIGS.
As shown in FIG.1 and FIG.2, the steel nut 1 as an insert metal fitting used for the press-fitting method of this embodiment has a female screw 3 penetrating vertically in the center, and a disc-shaped flange 2 and It consists of a cylindrical main body 4. Moreover, the outer periphery of the main-body part 4 is an uneven surface by knurling. The tip of the main body 4 is a chamfered portion 4a. A hole 6 into which the nut 1 is press-fitted is formed in the resin product 5 of the crystalline thermoplastic resin, and a diameter-expanded portion 7 is formed on the surface side of the hole 6. The resin product 5 of the present embodiment is a molded product of high density polyethylene (HDPE).

  The diameter D <b> 12 of the flange portion 2 of the nut 1 is a dimension that can be loosely fitted to the diameter D <b> 22 of the enlarged diameter portion 7 of the resin product 5. The diameter D11 of the main body 4 of the nut 1 is larger than the diameter D21 of the hole 6 of the resin product 5 so that a press-fitting allowance 9 (shown in FIG. 4) when the press-fitting of the nut 1 into the hole 6 is completed is obtained. It has become.

  Further, the total length L11 of the nut 1 and the total depth L21 of the hole 6 have the same dimensions, but the length L12 of the main body 4 of the nut 1 is longer than the depth L22 of the hole 6. When the press-fit of the nut 1 into the hole 6 is completed by this length difference, the burrs that have melted and leaked between the lower surface of the flange portion 2 and the annular flat surface portion 7a of the enlarged diameter portion 7 are accommodated. There is a gap that can be done.

Next, a method for press-fitting the nut 1 of the present embodiment into the resin product 5 will be described with reference to FIGS. 3 and 4.
As shown in FIG. 3, a portion of the nut 1 heated by a heating device (not shown) and having a HDPE melting temperature of 130 ° C. or higher is inserted into the hole 6 of the resin product 5 using a press-fitting device (not shown). The press-fitting is temporarily stopped in the press-fitted state. At this time, the press-fit depth L3 of the nut 1 is not particularly limited, but if it is shallow, it is difficult for the nut 1 to stand by itself while being temporarily stopped. You must support your posture. While the nut 1 is being supported, the press-fitting device cannot be involved in press-fitting other insert fittings, resulting in poor work efficiency. Further, when the press-fitting depth L3 of the nut 1 is increased, a portion corresponding to the press-fitting depth L3 of the inner wall surface of the hole 6 is melted at once, and as a result, a gap is formed between the periphery of the nut 1 and the hole 6. For example, a predetermined fixing force of the nut 1 to the resin product 5 cannot be obtained. Therefore, it is preferable that the press-fit depth L3 of the nut 1 is between a depth at which the nut 1 can stand on its own and a depth that is about a quarter of the length L12 of the main body 4.

  Then, while the nut 1 is temporarily stopped in the hole 6, the heat of the nut 1 is transmitted to the resin product 5 through the press-fit portion of the hole 6, and the inner wall surface of the hole 6 is softened. At the same time, since the nut 1 is deprived of heat, its temperature drops and falls below the melting temperature of 130 degrees C. Thus, at least when the surface temperature of the nut 1 is lower than the melting temperature, and preferably when it is 125 degrees C or less, if the press-fitting of the nut 1 into the hole 6 is resumed, the nut 1 The inner wall surface is press-fitted without melting, and the press-fitting is completed.

  As shown in FIG. 4, the nut 1 press-fitted into the resin product 5 is in a state in which the main body 4 compresses the surrounding press-fitting allowance 9. For this reason, since the resin (HDPE) forming the resin product 5 is solidified in an intimate contact state on the uneven surface on the outer periphery of the main body 4, the nut 1 is firmly fixed to the resin product 5.

  Further, a burr that has melted and leaked between the lower surface of the flange portion 2 fitted to the expanded diameter portion 7 and the annular flat surface portion 7a of the expanded diameter portion 7 when the press-fitting of the nut 1 is temporarily stopped. Is contained and solidified as it is. Therefore, not only the burrs are prevented from leaking to the outside, but also due to the presence of burrs, the frictional force increases due to the close contact between the lower surface of the flange portion 2 and the annular flat portion 7a of the enlarged diameter portion 7. Thus, the anti-rotation force of the nut 1 against the resin product 5 is obtained.

  Since the melting temperature of HDPE varies depending on the resin manufacturer or grade, in this embodiment, the resin product 5 is formed by applying the nut 1 whose temperature has been changed to the resin product 5. The temperature at which the resin to be melted (HDPE) starts melting is defined as the melting temperature. Therefore, in order to press-fit a heated insert fitting into the resin product 5, it is preferable to measure the individual melting temperature of the resin forming the resin product 5 in order to perform the press-fitting method of the present invention.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) In the above-described embodiment, the surface temperature of the nut 1 is lower than the melting temperature in a state in which the nut 1 is heated to a temperature higher than the melting temperature of the resin (HDPE) and a part of the nut 1 is press-fitted into the hole 6. The press-fitting was temporarily stopped until then, and the press-fitting of the nut 1 into the hole 6 was resumed to complete the press-fitting. For this reason, the nut 1 is temporarily stopped after being pressed into a predetermined depth of the hole 6 while melting the resin in the melting portion 8 on the surface side of the hole 6. Then, by further press-fitting the nut 1 whose temperature has decreased into the hole 6 of the resin product 5, the nut 1 is pressed into the hole 6 whose inner wall surface is softened without melting the resin on the inner wall surface of the hole 6. Press-in is completed. Therefore, it is possible to prevent the molten resin from leaking or shrinking, and to prevent a gap from being formed between the resin and the nut 1, and to press-fit the insert fitting that can obtain a strong fixing force of the nut 1 to the resin product 5. Can be provided.

  (2) In the above embodiment, the press-fitting is temporarily stopped after the nut 1 is pressed to a depth at which the nut 1 can stand independently along the axial direction of the hole 6. For this reason, it is not necessary to support the nut 1 by the press-fitting device while the press-fitting of the nut 1 is temporarily stopped. Therefore, the heat of the nut 1 can be efficiently transmitted to the resin without being wastedly transmitted to the press-fitting device, and the resin can be softened.

  (3) In the above-described embodiment, the press-fitting of the nut 1 that has been temporarily stopped is resumed after the surface temperature of the nut 1 becomes 5 degrees or more lower than the melting temperature of the resin. For this reason, the nut 1 is press-fitted when the inner wall surface of the hole 6 of the resin product 5 is sufficiently softened, and the resin is solidified in close contact with the periphery thereof. be able to.

  (4) In the above-described embodiment, the flange portion 2 of the nut 1 is fitted into the enlarged diameter portion 7 provided on the surface side of the hole 6 of the resin product 5. For this reason, even if the burr generated when the nut 1 is press-fitted into the hole 6 of the resin product 5 leaks into the enlarged diameter portion 7, the flange portion 2 covers the burr, so that the resin is not deteriorated in appearance. The nut 1 can be pressed into the product 5.

(5) In the above embodiment, since the softened resin is in close contact with the uneven surface formed on the outer periphery of the main body portion 4 of the nut 1, the nut 1 can be firmly fixed to the resin product 5.
(Example of change)
In addition, the said embodiment can also be changed and actualized as follows.
The nut 1 is provided with the flange portion 2 but is not provided with the flange portion 2 but only the outer peripheral body portion 4 having a uniform diameter, and the resin product 5 is not provided with the enlarged diameter portion 7 but only the hole 6. .
-Although the main body 4 is cylindrical, it should be a polygonal cylinder such as a hexagonal cylinder.
-Although the outer periphery of the main body 4 is an uneven surface by knurling, it should be a smooth curved surface.
-Although the hole 6 is a bottomed hole, it should be a through-hole penetrating vertically.
-Although the nut 1 was press-fitted into the hole 6 of the resin product 5 as an insert metal fitting, the head of the bolt was press-fitted into the hole 6 of the resin product 5 to expose the screw portion of the bolt to the outside of the resin product 5.

  L22: Depth, 2 ... Ridge part, 4 ... Body part, 5 ... Resin product, 6 ... Hole, 7 ... Diameter-expanded part.

Claims (5)

  In the method of press-fitting an insert fitting that press-fits a heated insert fitting into a hole of a thermoplastic resin product, the thermoplastic resin is a crystalline resin, and when the insert fitting heated above its melting temperature is pressed into the hole Then, heat of the insert metal fitting is transferred to the thermoplastic resin by press-fitting a part thereof, and the press fitting is temporarily stopped until the surface temperature of the insert metal fitting becomes lower than the melting temperature, and then the insert to the hole is inserted. A method for press-fitting an insert metal fitting, wherein the press-fitting of the metal fitting is resumed to complete the press-fitting.   The method of press-fitting an insert metal fitting according to claim 1, wherein the insert metal fitting is temporarily stopped after being press-fitted to a depth capable of being self-supporting along the axial direction of the hole.   The method of press-fitting an insert metal fitting according to claim 1 or 2, wherein the insert metal fitting is a connector for connecting the resin product and another part or structure.   The insert metal fitting is provided with a flange portion, and on the other hand, a diameter-expanded portion is provided on the surface side of the hole of the resin product, and the flange portion is fitted to the diameter-expanded portion. 4. The method for press-fitting an insert fitting according to any one of claims 3 to 3.   The method for press-fitting an insert fitting according to any one of claims 1 to 4, wherein the outer periphery of the body portion of the insert fitting is an uneven surface.

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