Resin molded article

Abstract

This resin molded article is provided with a flat-plate-shaped screw fastening part, and the screw fastening part has: a through-hole through which a screw passes; a contact region provided around the through-hole and into which the head of the screw comes into contact; a cutout part which is formed by extending from the through-hole in a first direction along the weld line, and which cubes a part of the contact region; and a pair of slits formed so as to extend further in the first direction from the cutout portion, the slits being symmetrical with respect to the weld line.

Description

Technical Field

[0001] The present invention relates to a resin molded product. Background Art

[0002] Patent document 1 disclosed below discloses the following technology: for the purpose of providing a resin-molded component in which cracks starting from a weld line are less likely to occur when pressure is applied, in a resin-molded component having a disk-shaped main body portion having a through hole at the center, an opening portion connected to the through hole and extending toward a peripheral portion of the main body portion away from the gate cut-off portion is provided along a straight line connecting the center of the through hole and a gate cut-off portion.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-59168 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, the technology of Patent Document 1 cannot sufficiently release the stress applied to the weld line when the screw is tightened, and high stress is still applied to the weld line when the screw is tightened, which may cause cracks along the weld line.

[0008] Means for solving problems

[0009] A resin molded product according to one embodiment has a flat screw fastening portion, wherein the screw fastening portion has: a through hole for the screw to pass through; a contact area arranged around the through hole for the head of the screw to contact; a notch formed by extending from the through hole in a first direction along a weld line and cutting away a portion of the contact area; and a pair of slits formed by further extending from the notch in the first direction and symmetrically relative to the weld line.

[0010] Effects of the Invention

[0011] According to the resin molded article of one embodiment, it is possible to suppress stress applied to the weld line when the screw is tightened. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a perspective view of the appearance of a resin molded product according to one embodiment as viewed from above.

[0013] Figure 2 This is a perspective view of the appearance of a resin molded product according to one embodiment as viewed from below.

[0014] Figure 3 This is an exploded perspective view of a resin molded product according to one embodiment.

[0015] Figure 4 This is a cross-sectional view of a resin molded product according to one embodiment.

[0016] Figure 5 This is a bottom view of a battery cover included in a portable device according to an embodiment.

[0017] Figure 6 This is a diagram showing an example of a battery cover included in a portable device according to an embodiment.

[0018] Figure 7 It is a diagram showing a first modified example of the screw fastening portion included in the portable device according to one embodiment.

[0019] Figure 8 It is a diagram showing a second modified example of the screw fastening portion included in the portable device according to the embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, one embodiment will be described with reference to the drawings.

[0021] (Structure of Portable Device 100 )

[0022] Figure 1 This is a perspective view of the appearance of the portable device 100 according to one embodiment as viewed from above. Figure 2 This is a perspective view of the appearance of the portable device 100 according to one embodiment as viewed from below. Figure 3 It is an exploded perspective view of the portable device 100 according to one embodiment. Figure 4 It is a cross-sectional view of a portable device 100 according to one embodiment.

[0023] It should be noted that in the following description, for convenience, the Z-axis direction in the figure (the thickness direction of the shell 110) is set as the up and down direction, the Y-axis direction in the figure (the short side direction of the shell 110) is set as the horizontal width direction, and the X-axis direction in the figure (the length direction of the shell 110) is set as the front and back direction.

[0024] Figure 1 The portable device 100 shown is a small device that can be carried by a user. As an example, the portable device 100 is an electronic key that can remotely operate the vehicle (e.g., lock, unlock, start, etc.) by wirelessly communicating with an onboard device mounted on the vehicle. However, the portable device 100 can also be used for any purpose other than an electronic key.

[0025] like Figure 1 to Figure 4 As shown, the portable device 100 includes a housing 110 , a battery cover 120 , and a circuit board 130 .

[0026] The housing 110 is a container-shaped member made of resin with a hollow structure. The housing 110 has a substantially rectangular parallelepiped shape. The housing 110 can be divided into an upper housing 111 and a lower housing 112 at an intermediate position in the vertical direction. It should be noted that the outer shape of the housing 110 is a substantially rectangular parallelepiped shape, but its front end (the end on the positive side of the X-axis) is interrupted.

[0027] Instead, a substantially square cylindrical convex portion 113 is provided protruding forward (on the positive side of the X-axis) at the front end portion (the end portion on the positive side of the X-axis) of the housing 110. When the housing 110 is divided into two parts, the convex portion 113 can be divided into two parts: an upper convex portion 113A integrally provided on the upper housing 111 and a lower convex portion 113B integrally provided on the lower housing 112.

[0028] The battery cover 120 is a hollow resin container-shaped member. The battery cover 120 is an example of a "resin molded product". The battery cover 120 has an outer shape that is continuous with the housing 110 (i.e., an outer shape that complements the interrupted portion of the housing 110), and is attached to the front end portion (the end portion on the positive side of the X axis) of the housing 110, and forms an outer shape that is substantially rectangular parallelepiped together with the housing 110. A battery (not shown) for supplying power to the circuit board 130 is built into the battery cover 120.

[0029] The battery cover 120 has a rectangular opening 120A at the rear end (the part on the negative side of the X axis) facing the housing 110. The battery cover 120 is attached to the front end (the end on the positive side of the X axis) of the housing 110 by being inserted into the protrusion 113 of the housing 110 from the opening 120A, and is supported from the inside by the protrusion 113 so as not to fall off the housing 110 easily.

[0030] It should be noted that the housing 110 and the battery cover 120 are formed into a predetermined shape by injection molding using a synthetic resin material such as ABS resin or PC resin.

[0031] The circuit substrate 130 is a resin-made, flat-plate-shaped member provided inside the housing 110. The circuit substrate 130 is fixed inside the housing 110 in a horizontal position relative to the lower housing 112. An integrated circuit for realizing various functions (e.g., wireless communication function, control function, etc.) of the resin molded product 10 is constructed by mounting various electronic components on the circuit substrate 130. The integrated circuit operates using power supplied from a battery (not shown) built into the battery cover 120. For example, a PCB (Printed Circuit Board) is used as the circuit substrate 130.

[0032] (Thread locking fixing structure)

[0033] Here, the threaded locking and fixing structure of the portable device 100 is described. Figure 2 to Figure 4 As shown, the battery cover 120 has a main body 122 and a flat screw fastening portion 121 protruding from the rear end (the end on the negative side of the X-axis) of the lower wall portion 122A of the main body 122 and the central portion in the left-right direction (Y-axis direction) toward the rear (negative direction of the X-axis). In particular, in this embodiment, one end (the end on the positive side of the X-axis) of the screw fastening portion 121 is connected to the main body 122, and the other end (the end on the negative side of the X-axis) is not connected to anything, so it has a tongue shape. The screw fastening portion 121 has a circular through hole 121A that penetrates the screw fastening portion 121 in the up-down direction in the central portion when viewed from above.

[0034] On the other hand, the lower wall portion 112A of the lower housing 112 has a recess 112B having substantially the same shape as the screw fastening portion 121 formed at the front end portion (the end on the positive side of the X-axis) and the center portion in the left-right direction (the Y-axis direction). The recess 112B has a threaded hole 112C threaded upward (in the positive direction of the Z-axis) formed at the center portion thereof when viewed from above.

[0035] Here, if Figure 2 and Figure 4 As shown, when the portable device 100 of one embodiment is mounted with the battery cover 120 on the front end portion (the end on the positive side of the X-axis) of the housing 110, the screw fastening portion 121 of the battery cover 120 is fitted into the recess 112B of the lower housing 112. In addition, at this time, when viewed from below (the negative direction of the X-axis), the through hole 121A of the screw fastening portion 121 overlaps with the threaded hole 112C of the recess 112B.

[0036] Therefore, for the portable device 100 of one embodiment, if Figure 4 As shown, the screw fastening portion 121 can be screw-fastened and fixed to the recessed portion 112B by passing the countersunk screw 140 through the through hole 121A of the screw fastening portion 121 and screwing it into the threaded hole 112C of the recessed portion 112B.

[0037] (Detailed Structure of Screw Fastening Portion 121)

[0038] Figure 5 This is a bottom view of the battery cover 120 included in the portable device 100 according to one embodiment.

[0039] like Figure 5 As shown, the screw fastening portion 121 of the battery cover 120 has a circular through hole 121A penetrating the screw fastening portion 121 in the up-down direction at the center portion in a plan view.

[0040] The screw fastening portion 121 has a tapered surface 121B (an example of a “contact region”) formed in an annular shape around the through hole 121A so as to surround the through hole 121A in a plan view. The tapered surface 121B has a tapered shape (conical shape) whose diameter gradually decreases toward the depth direction (Z-axis positive direction).

[0041] Therefore, when fastening is performed using the countersunk screw 140, the screw fastening portion 121 can utilize the same conical tapered surface 121B to withstand the fastening force from the conical base surface of the head 141 of the countersunk screw 140, and can accommodate the head 141 of the countersunk screw 140 on the inner side of the tapered surface 121B in a manner that does not protrude from the screw fastening portion 121.

[0042] Here, if Figure 5 As shown, the screw fastening portion 121 has a weld line WL extending in the front-to-back direction (X-axis direction) at the middle position in the left-right direction (Y-axis direction) of the portion that is further back than the through hole 121A (negative side of the X-axis). The weld line WL is formed when the molten resin that flows from one side (positive side of the Y-axis) bypasses the outside of the through hole 121A and merges with the molten resin that flows from the other side (negative side of the Y-axis) during injection molding of the battery cover 120. Therefore, the weld line WL can also be expressed as a "molten resin confluence portion" or the like. It should be noted that the weld line WL can be obtained by performing a flow analysis of the molten resin for injection molding of the battery cover 120.

[0043] Since the screw fastening portion 121 has a weld line WL, when fastening is performed using the countersunk screw 140 , stress is applied to the weld line WL, and cracks may be generated along the weld line WL.

[0044] Therefore, in the portable device 100 of one embodiment, if Figure 5 As shown, the screw fastening portion 121 is provided with a cutout portion 121C and a pair of slits 121D.

[0045] The cutout portion 121C is formed to extend from the through hole 121A in the first direction D1 (X-axis negative direction) along the weld line WL, and cuts out a portion of the tapered surface 121B.

[0046] The pair of slits 121D are formed to extend further in the first direction D1 (X-axis negative direction) from the cutout portion 121C and are symmetrical with respect to the weld line WL.

[0047] The pair of slits 121D is a portion where the protrusion 121E is formed between the pair of slits 121D. The cutout portion 121C is a portion connecting the through hole 121A and the pair of slits 121D.

[0048] Note that the screw-fastening portion 121 has a protrusion 121E protruding toward the through hole 121A between the pair of slits 121D by providing the pair of slits 121D, and thus the weld line WL exists on the protrusion 121E.

[0049] Therefore, it is important here to form the cutout portion 121C and the pair of slits 121D so that the head 141 of the countersunk screw 140 does not come into contact with the protrusion 121E when fastening is performed using the countersunk screw 140 .

[0050] It should be noted that the front end portion (the end on the positive side of the X-axis) of the protrusion 121E is located at approximately the same position as the outer periphery of the head 141 of the countersunk screw 140 , and can therefore function as a positioning and stopper for the outer periphery of the head 141 of the countersunk screw 140 .

[0051] The portable device 100 of one embodiment provides the notch 121C and the pair of slits 121D. When fastened with the countersunk screws 140, stress can be concentrated on the pair of slits 121D (i.e., both outer sides of the weld line WL). Therefore, stress applied to the weld line WL (protrusion 121E) can be suppressed.

[0052] In particular, in the present embodiment, as an example of a preferred structure capable of relieving stress applied to the weld line WL, a pair of slits 121D are provided in parallel with each other.

[0053] (Example)

[0054] Figure 6 FIG. 1 is a diagram showing an example of a battery cover 120 included in the portable device 100 according to an embodiment.

[0055] In this embodiment, Figure 5 The battery cover 120 shown is an "Example", and the battery covers prepared for comparison are "Comparative Example 1" and "Comparative Example 2". The stress applied to the weld line WL was measured by simulation, and the probability of cracking was determined.

[0056] In addition, in "Comparative Example 1", a battery cover having neither a cutout portion nor a slit portion was used. In addition, in "Comparative Example 2", a battery cover having a cutout portion but not a slit portion was used.

[0057] like Figure 6As shown in FIG. 1 , in “Comparative Example 1”, it was found that a very large stress of “about 48 MPa” was applied to the weld line WL, and the possibility of cracking was extremely high, so the possibility of cracking was judged as “× (poor)”. This is considered to be because in “Comparative Example 1”, since there is no notch or slit, the stress has nowhere to be released, and the stress is concentrated on the weld line WL.

[0058] In addition, if Figure 6 As shown in FIG. 1 , in “Comparative Example 2”, it was found that a relatively large stress of “about 8 MPa” was applied to the weld line WL, and since the possibility of cracking was relatively high, the possibility of cracking was determined as “× (poor)”. This is considered to be because in “Comparative Example 2”, since the notch portion is provided, a certain degree of stress can be released to the notch portion, but this alone is insufficient, and the stress is still concentrated on the weld line WL.

[0059] On the other hand, Figure 6 As shown, in the "Example", it was found that the possibility of cracking was extremely low when a very small stress of "less than 1 MPa" was applied to the weld line WL, so the possibility of cracking was determined to be "0 (good)". This is considered to be because in the "Example", since the notch 121C and the pair of slits 121D are provided, most of the stress can be released to the pair of slits 121D.

[0060] (First Modification)

[0061] Figure 7 This is a diagram showing a first modified example of the screw fastening portion 121 included in the portable device 100 according to the embodiment. Figure 7 The screw fastening portion 121 shown is Figure 5 A first modified example of the screw fastening portion 121 is shown. Figure 7 The screw fastening portion 121 shown is Figure 5 The screw fastening portion 121 shown is different in that the groove width of the cutout portion 121C is enlarged and the cutout portion 121C is extended in the first direction D1.

[0062] It should be noted that the inventors have confirmed through simulation that even when the groove width of the notch 121C is increased and the notch 121C is extended in the first direction D1, the same as when the pair of slits 121D are provided in parallel with each other ( Figure 5 ), most of the stress can be released to the pair of slits 121D, and therefore, an extremely small stress of "less than 1 MPa" is applied to the weld line WL.

[0063] (Second Modification)

[0064] Figure 8FIG. 1 is a diagram showing a second modified example of the screw fastening portion 121 included in the portable device 100 according to the embodiment. Figure 8 The screw fastening portion 121 shown is Figure 5 A second modified example of the screw fastening portion 121 is shown. Figure 8 The screw fastening portion 121 shown is Figure 5 The screw fastening portion 121 shown is different in that a pair of slits 121D are provided in a radial shape (ie, a shape in which the intervals between them gradually increase as they extend in the first direction D1 (the negative direction of the X-axis)).

[0065] It should be noted that the inventors have confirmed through simulation that even when the pair of slits 121D are arranged radially, the difference is still the same as when the pair of slits 121D are arranged parallel to each other ( Figure 5 ), most of the stress can be released to the pair of slits 121D, and therefore, an extremely small stress of "less than 1 MPa" is applied to the weld line WL.

[0066] As mentioned above, although one embodiment of the present invention has been described in detail, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

[0067] For example, in the above-mentioned embodiment, the left-right width (width in the Y-axis direction) of the screw fastening portion 121 is made smaller than the left-right width of the main body 122, but the present invention is not limited thereto, and the left-right width (width in the Y-axis direction) of the screw fastening portion 121 may be made equal to the left-right width of the main body 122. Even in this case, the stress suppression effect of the weld line generated by providing the notch 121C and the pair of slits 121D is the same.

[0068] It should be noted that from the viewpoint of suppressing the stress applied to the weld line WL, Figure 5 , Figure 7 , Figure 8 As is consistent with the structures shown, it is preferable that at least one pair of slits 121D is provided within a range forming an acute angle with respect to the center of the through hole 121A.

[0069] In addition, in the above-mentioned embodiment, an example of using the countersunk screw 140 to fix the screw fastening portion 121 is described, but the present invention is not limited to this. Even when other screws (screws whose base surface is not conical but flat) are used to fix the screw fastening portion 121, the stress suppression effect of the weld line generated by providing the notch portion 121C and the pair of slits 121D is the same.

[0070] The present international application claims the priority based on Japanese Patent Application No. 2022-123571 filed on August 2, 2022, the entire contents of which are hereby incorporated by reference.

[0071] Description of reference numerals:

[0072] 100 Portable Devices

[0073] 110 Housing

[0074] 111 upper side housing

[0075] 112 Lower side housing

[0076] 112A Lower wall

[0077] 112B concave part

[0078] 112C threaded hole

[0079] 113 convex part

[0080] 113A Upper convex part

[0081] 113B Lower convex part

[0082] 120 Battery cover (resin molded product)

[0083] 120A Opening

[0084] 121 Screw fastening part

[0085] 121A Through hole

[0086] 121B Cone (abutment area)

[0087] 122 Main body

[0088] 122A Lower wall

[0089] 130 Circuit board

[0090] 140 Countersunk Screw

[0091] 141 Head

[0092] D1 First direction

[0093] WL Weld line.

Claims

1. A resin molded product having a flat plate-shaped screw fastening portion, characterized in that: The screw fastening portion has: A through hole for a screw to pass through; an abutment area, which is arranged around the through hole and is abutted by the head of the screw; a notch portion extending from the through hole in a first direction along the weld line and notching a portion of the abutment region; and A pair of slits are formed extending from the cutout portion further in the first direction and symmetrically with respect to the weld line.

2. The resin molded article according to claim 1, wherein The pair of slits are arranged parallel to each other.

3. The resin molded article according to claim 1, wherein The pair of slits are arranged radially.

4. The resin molded article according to claim 1, wherein The pair of slits are provided within a range forming an acute angle with respect to the center of the through hole.

5. The resin molded article according to claim 1, wherein The resin molded product comprises a main body portion, The screw fastening portion is provided so as to extend from the main body toward the first direction.

6. The resin molded article according to claim 1, wherein The abutting area is a conical surface.

7. The resin molded article according to claim 1, wherein The pair of slits is a portion forming a protrusion between the pair of slits, The cutout portion is a portion connecting the through hole and the pair of slits.

8. The resin molded article according to claim 1, wherein The pair of slits is a portion forming a protrusion between the pair of slits, The cutout portion and the pair of slits are formed so that the head of the screw does not come into contact with the protrusion when the screw is tightened.

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