Grommet and method for manufacturing method therefor

Abstract

To provide a grommet and a manufacturing method therefor capable of maintaining predetermined sealing performance by minimizing deformation of an annular core material and forming it into an appropriate shape.SOLUTION: A grommet 10 comprises an annular core material 20 and an elastic part 30, which are mounted between an inner wall surface 1a of a recess 1 and an outer wall surface 3a of an object 3 to be inserted into the recess 1. The elastic part 30 is provided on the inner and outer surfaces of a peripheral wall 21 of the annular core material 20, and a concave part 22 is formed on a fixed surface of the elastic part 30 in an inner surface 21a of the peripheral wall 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a grommet that is installed between a recess and an object installed in the recess to maintain a seal, and a method for manufacturing the same. [Background technology]

[0002] In conventional grommets, many have been proposed in which the inner and outer surfaces of the peripheral wall of the annular core material are covered with an elastic material, taking into consideration the degree of elastic deformation and shape stability when placed between the inner wall surface of the recess and the outer wall surface of the object attached to the recess (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-175331 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a grommet is formed by insert molding using an annular core material with a flat, smooth inner surface, as in Patent Document 1, the timing when the elastic material on the inner side of the annular core material is completed to fill is different from the timing when the elastic material on the outer side is completed to fill, so pressure is generated on the annular core material from the filled space side to the unfilled space side, which may result in deformation of the annular core material.

[0005] Figure 5 is a longitudinal cross-sectional view of this type of conventional grommet 100. Even if grommet 100 is manufactured using a distortion-free cylindrical annular core 120 so that the annular core 120 is covered with elastic portion 130, there is a risk of partial deformation of the annular core 120 inside, as shown by portion X in Figure 5. If the annular core 120 is deformed, it may cause the grommet 100 to malfunction during use. Even if the annular core 120 is deformed in this way, it is not possible to detect the deformation of the annular core 120 from the outside of the grommet 100.

[0006] The present invention has been proposed in consideration of the above circumstances, and its object is to provide a grommet and a manufacturing method thereof that can minimize deformation of the annular core member and maintain a proper shape to maintain a predetermined sealing performance. Another object of the present invention is to reduce the product defect rate. Another object of the present invention is to improve the bonding strength between the annular core member and the elastic portion. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the grommet of the present invention is a grommet comprising an annular core material and an elastic portion, which is attached between the inner wall surface of a recess and the outer wall surface of an object to be inserted into the recess, and is characterized in that the elastic portion is provided on the inner and outer surfaces of the peripheral wall of the annular core material, and a recess is formed on the fixing surface with the elastic portion on the inner surface of the peripheral wall.

[0008] In addition, in order to achieve the above-mentioned object, the grommet manufacturing method of the present invention is a method of manufacturing a grommet in which a grommet having an annular core material and an elastic portion is manufactured by insert molding using a molding mold, and which is attached between the inner wall surface of a recess and the outer wall surface of an object to be inserted into the recess, and is characterized in that a flow fluctuation means is provided on the inner surface of the peripheral wall of the annular core material, which fluctuates the flow of raw material of the elastic portion injected into the molding mold. [Effects of the Invention]

[0009] The grommet and its manufacturing method of the present invention have the above-mentioned configuration and procedure, so that deformation of the annular core member can be minimized to form an appropriate shape, thereby maintaining a predetermined sealing performance. Furthermore, the manufacturing method of the grommet of the present invention can reduce the defective rate of grommet products. [Brief explanation of the drawings]

[0010] [Figure 1]1A is a perspective view of a grommet according to an embodiment of the present invention, FIG. 1B is a vertical cross-sectional view taken along line XX in FIG. 1A, and FIG. 1C is a perspective view of an annular core member. [Figure 2] 10(a) to 10(d) are explanatory views of various other examples of the annular core material. [Figure 3] 1A is a longitudinal cross-sectional view of a molding die, and FIG. 1C is a schematic cross-sectional view of two different examples of annular core materials showing the flow of raw material for the elastic portion inside and outside the annular core material. [Figure 4] 5A to 5C are schematic vertical cross-sectional views showing the steps and states of attaching an object and a grommet to a recess. [Figure 5] FIG. 1 is a vertical cross-sectional view of a conventional grommet. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, the basic configuration of the grommet 10 according to the embodiment will be described.

[0012] The grommet 10 according to the embodiment described below comprises an annular core material 20 and an elastic portion 30 that are attached between the inner wall surface 1a of the recess 1 and the outer wall surface 3a of the object 3 to be inserted into the recess 1. The elastic portion 30 is provided on the inner and outer surfaces of the peripheral wall 21 of the annular core material 20, and a recess 22 is formed on the surface of the inner surface 21a of the peripheral wall 21 where the elastic portion 30 is fixed (see FIGS. 1 to 4).

[0013] Next, the detailed configuration of the grommet 10 of this embodiment and various example embodiments will be described with reference to Fig. 1 and Figs. 2(a) to (d). Note that the up and down positions and directions of the grommet 10 in this specification are based on the state in which the opening 11 of the cylindrical body of the grommet 10 faces in the up and down directions as shown in Fig. 1.

[0014] In these examples, the recesses 22 shown in Figures 1 and 2(a) are openings 221, 222 (bottomless recesses) that penetrate from the inside to the outside of the peripheral wall 21, and the recesses 22 shown in Figures 2(b) to (d) are depressions 223, vertical grooves 224, and horizontal grooves 225 (all of which are bottomed recesses) provided on the inner surface 21a of the peripheral wall 21.

[0015] First, the external shape of the grommet 10 will be described based on Fig. 1. Note that other examples of the annular core material 20 (Figs. 2(a) to (d)) described later are explanatory diagrams of only the annular core material 20, but are premised on the same external shape as Fig. 1.

[0016] 1 is an annular body, the entire surface of which is covered with an elastic portion 30, and an annular core material 20 is disposed inside the elastic portion 30. In other words, the annular core material 20 has a substantially cylindrical peripheral wall 21, the elastic portions 30 are fixed to the inner and outer surfaces of which, and the entire annular core material 20 is covered with the elastic portion 30 to form the grommet 10.

[0017] As shown in Figures 1(a) and 1(b), on the surface of the elastic portion 30 fixed to the inner and outer surfaces of the peripheral wall 21, i.e., on the surface of each of the inner elastic portion 31 and the outer elastic portion 32, three convex ridges 31a and 32a, which protrude to the same degree in the circumferential direction, are formed via concave grooves 31b and 32b at approximately the same height position between the inner elastic portion 31 and the outer elastic portion 32.

[0018] The thicknesses of the inner elastic portion 31 and the outer elastic portion 32 are substantially the same. The protruding dimension of the ridge 31a in the inner elastic portion 31 is substantially the same as the protruding dimension of the ridge 32a in the outer elastic portion 32, and the depth dimension of the recessed groove 31b in the inner elastic portion 31 is substantially the same as the depth dimension of the recessed groove 32b in the outer elastic portion 32.

[0019] 1(b), the outer elastic portion 32 tapers inward at the upper end 33 and the lower end 34 (areas where the annular core 20 is not present), and both sides of the grommet 10 as a whole have a convexly curved shape. The inner elastic portion 31 does not widen or narrow at the upper end 33 or the lower end 34, and an inner diameter surface that is not distorted between the top and bottom is formed.

[0020] Next, various annular core materials 20 used in the grommet 10 of FIG. 1 will be described in order with reference to FIG. 1 and FIGS. 2(a) to (d).

[0021] As shown in Figures 1(b) and 1(c), the annular core material 20 used in the grommet 10 of Figure 1 is made by processing a flat plate material into a cylindrical body with a recess 22 formed in a portion thereof. In the example of Figure 1, the recess 22 is an opening 221 (a bottomless recess) formed by cutting out a semicircular portion of the lower edge of the cylindrical body. Note that the opening is not limited to the cutout-shaped opening 221, and may be, for example, a circular opening formed partway along the height direction, or, as will be described later in Figure 2(a), a slit-shaped opening 222 formed by removing the entire vertical length of the peripheral wall 21 partway along the circumferential direction.

[0022] 1(b), in the product of grommet 10, in the manufacturing stage by insert molding, which will be described later, the raw material of elastic portion 30 enters the space of recess 22 of annular core material 20, thereby filling the space of recess 22 with elastic portion 30 (elastic material). In other words, elastic portion 30 is connected inside and outside via recess 22 of annular core material 20.

[0023] As will be described later, such recesses 22 serve as flow fluctuation means 22A for preventing deformation of the annular core material 20 due to the flow of raw material for the elastic portion 30 within a molding die 50 (see FIG. 4) during the manufacturing stage of the grommet 10 by insert molding. Examples of recesses 22 that act as flow fluctuation means 22A include the opening 221 shown in FIG. 1 and recesses 22 of various shapes shown in FIGS. 2(a) to 2(d).

[0024] 2(a) is a bottomless recess, and is a slit-shaped opening 222 that is open in a portion of the circumferential direction of the annular core material 20. Because this recess 22 is an opening 222, the inside and outside of the elastic portion 30 are connected via the recess 22 of the annular core material 20.

[0025] The recesses 22 provided in the annular core material 20 in Fig. 2(b) are bottomed recesses, and more specifically, are a plurality of depressions 223 (dimples) provided on the inner surface 21a of the annular core material 20, which are regularly arranged vertically and horizontally. In the finished grommet 10, these depressions 223 are filled with elastic portions 30 (elastic material).

[0026] The recesses 22 provided in the annular core material 20 in Fig. 2(c) are bottomed recesses, and more specifically, are a plurality of vertical grooves 224 provided on the inner surface 21a of the annular core material 20, which are formed at approximately equal intervals along the circumferential direction. In the finished grommet 10, these vertical grooves 224 are filled with elastic portions 30 (elastic material).

[0027] 2(d) is a recessed portion with a bottom, specifically a plurality of lateral grooves 225 formed in the inner surface 21a of the annular core 20 without interruption in the circumferential direction, and these are formed at approximately equal intervals in the vertical direction. In the finished grommet 10, these lateral grooves 225 are filled with elastic portions 30 (elastic material).

[0028] Next, a method for manufacturing grommet 10 using an annular core member 20 having recesses 22 as described above will be described with reference to Figures 1 to 3. First, the basic steps of the method for manufacturing grommet 10 will be described.

[0029] The method for manufacturing grommet 10 is a method for manufacturing grommet 10 by insert molding using a molding die 50 to mount grommet 10 having an annular core material 20 and an elastic portion 30, which is fitted between the inner wall surface 1a of recess 1 and the outer wall surface 3a of object 3 to be inserted into recess 1 (see FIGS. 2 and 3). Flow fluctuation means 22A (recess 22) is provided on the inner surface 21a of the peripheral wall 21 of annular core material 20 to fluctuate the flow of raw material for elastic portion 30 injected into molding die 50 (see FIGS. 1(b)(c) and 2(a) to (d)).

[0030] 3(a) is a vertical cross-sectional view of a molding die 50, and in the example shown in FIG. 2(c), an annular core material 20 having vertical grooves 224 as recesses 22 is used. The molding die 50 has an upper die 51 and a lower die 52, and is provided with a molding cavity 53 as the internal space between the upper die 51 and the lower die 52 into which the raw material of the elastic part 30 is filled.

[0031] In this manufacturing method, first, annular core material 20 with an adhesive applied to its surface is placed in molding cavity 53 on the lower mold 52 side, then upper mold 51 is attached, and raw material for elastic portion 30 is injected through material injection port 54. After the raw material for elastic portion 30 has hardened, it is demolded to obtain grommet 10.

[0032] In manufacturing using such a molding die 50, after the raw material for the elastic portion 30 is injected through the material injection port 54, multiple recesses 22 consisting of vertical grooves 224 are formed on the inner surface 21a of the peripheral wall 21 of the annular core material 20, as shown in the schematic diagram (cross-sectional view) of Figure 3(b), so that the surface area with which the raw material comes into contact on the inner surface side increases, slowing down the flow of the raw material. Note that the two-dot chain line in Figure 3(b) indicates the flow of the raw material.

[0033] In this way, by slowing down the flow of raw materials on the inner surface, the difference in timing when the raw materials are filled inside and outside can be reduced, and the pressure on the unfilled part from the filling completion side through the peripheral wall 21 against the peripheral wall 21 can be reduced, and as a result, deformation of the annular core material 20 due to the pressure of the raw materials can be suppressed.

[0034] Assuming that the thicknesses of the inner elastic portion 31 and the outer elastic portion 32 are approximately the same (see FIG. 1), if both the inner and outer surfaces of the peripheral wall 21 are smooth, the filling volume will be smaller on the inner side than on the outer side, and the time required to complete filling will be shorter on the inner side than on the outer side. Therefore, it is desirable to increase the filling volume by providing a recess 22 on the inner side, and to increase the resistance to the flow of raw material by the recess 22.

[0035] Since the recesses 22 are provided to lengthen the time until the filling of the raw material is completed on the inner surface side, there is a risk that the filling on the outer surface side will be completed earlier as a result of providing the recesses 22, but this can be adjusted by adjusting the number and shape of the recesses 22 provided on the inner surface side. In this way, the difference in timing between the filling completed side and the filling incomplete side can be adjusted to be smaller.

[0036] 2(b), the recess 22 increases the surface area of ​​the inner surface, and thus the flow of raw material on the inner surface can be slowed down. Furthermore, when the recess 22 is a lateral groove 225 shown in the longitudinal cross section of FIG. 2(d), the flow of raw material in the lateral groove 225 can be slowed down more than on the surface other than the lateral groove 225, and therefore the flow of raw material can be made uneven between the groove portion and the non-groove portion. Consequently, the recess 22 slows down the completion of filling on the entire inner surface, and the pressure on the peripheral wall 21 can be suppressed.

[0037] 3(c) is a diagram showing the flow of raw materials when the annular core material 20 has a notched opening 221 as the recess 22. As in FIG. 3(b), the two-dot chain line indicates the flow of raw materials.

[0038] In the case of Figure 3(c), the flow speed of the raw material on the inner and outer surfaces of the peripheral wall 21 is almost the same, so naturally the raw material flowing on the inner surface reaches the filling end portion 55 faster, and the raw material tries to flow to the outer surface through the opening 221.

[0039] In this way, as soon as filling is completed on the inner surface side, the raw material flows to the outer surface side through the opening 221, which reduces the pressure on the peripheral wall 21 from the inner surface side toward the outer surface side, which is the unfilled side, and as a result, reduces deformation of the annular core material 20. The same is true when the recess 22 is a slit-shaped opening 222.

[0040] According to the manufacturing method described above, the action of the flow fluctuation means 22A can suppress the pressure of the raw material from the inner side pressing against the outer surface of the peripheral wall 21, and as a result, the grommet 10 can be made to have an appropriate shape that is not distorted, and in particular does not have any parts bulging outward.

[0041] In short, these manufacturing methods allow grommet 10 to be molded into the proper shape while minimizing deformation of the annular core, thereby maintaining the desired sealing performance of grommet 10. Furthermore, implementing these manufacturing methods can also reduce the defective rate.

[0042] As explained above, the mechanism for varying the flow rate of the raw material on the inner surface differs between when the recess 22 is a bottomed recess (depression 223, vertical groove 224, horizontal groove 225) and when it is a bottomless recess (openings 221, 222) (see comparison of Figures 3(b) and (c)).

[0043] However, both recesses 22 constitute flow fluctuation means 22A that fluctuates the flow of raw material in forming mold 50. Thus, in either case, the flow fluctuation of the raw material caused by flow fluctuation means 22A can suppress the pressure from the inner surface side onto peripheral wall 21, and as a result, deformation of annular core material 20 during the manufacturing stage can be suppressed.

[0044] 3(c), the openings 221, 222 in the annular core 20 are preferably provided at the filling end portion 55, which is located farthest from the material injection port 54, but may be provided at other positions, or a plurality of openings 221, 222 may be provided. The grommet 10 may also be manufactured using an annular core 20 in which both a bottomless recess and a bottomed recess are provided on the inner surface 21a of the peripheral wall 21.

[0045] Furthermore, since the grommet 10 is manufactured in this manner by insert molding so that the entire surface of the annular core material 20 is covered in close contact with the elastic portion 30 and the recess 22 is filled with elastic material, the adhesion between the annular core material 20 and the elastic material 30 can be made stronger.

[0046] In short, by manufacturing the grommet 10 using an annular core material 20 having a recess 22, the adhesive surface area between the metal (annular core material 20) and the elastic material is increased, thereby improving the bonding strength between the annular core material 20 and the elastic portion 30.

[0047] The various grommets 10 described above are used as shown in Figure 4. The manner in which the grommet 10 is used will be described with reference to Figure 4. Note that Figure 4 illustrates the grommet 10 of Figure 1 as an example of the annular core member 20.

[0048] As shown in Figure 4, grommet 10 is attached so as to be integrated with object 3, such as a cylindrical or cylindrical body, and is attached to a recess 1, such as a round hole, together with object 3, to maintain the airtightness of the outer periphery of object 3 within recess 1.

[0049] Specifically, grommet 10 is disposed between the inner wall surface 1a of recess 1 and the outer wall surface 3a of object 3, and outer elastic portion 32 elastically contacts inner wall surface 1a of recess 1 and deforms so that the unevenness of the outer surface conforms to inner wall surface 1a of recess 1, while inner elastic portion 31 elastically contacts outer wall surface 3a of object 3 and deforms so that the unevenness of the inner surface conforms to outer wall surface 3a of object 3. By elastically deforming elastic portion 30 in this manner, object 3 is mounted in recess 1 in a sealed state.

[0050] 1 and 2, a flow fluctuation effect can also be expected by providing openings or grooves that are finer than the recesses 22. The raw material of the elastic portion may be inserted into such fine recesses to increase the strength of adhesion of the elastic portion 30 to the annular core material 20 by an anchor effect.

[0051] The grommet 10 according to the various embodiments described above is merely an example, and other configurations are also possible. It goes without saying that the overall shape of the grommet 10 can be changed as appropriate as a design matter. In addition, the entire surface of the annular core 20 is not limited to being covered by the elastic portion 30, and a portion of the outer surface, inner surface, etc. of the peripheral wall 21 may be exposed.

[0052] Furthermore, the manufacturing method of the grommet 10 is not limited to the example shown in FIG. 4, and it goes without saying that it can be modified as appropriate as a design item of the insert molding. [Explanation of symbols]

[0053] 1 recess 1a Inner wall surface 3. Object 3a External wall surface 10 Grommets 11 Aperture 20 Annular core material 21 Peripheral wall 21a Inside 22 recess 22A Flow Variation Means 221 (notched) opening (bottomless recess) 222 (Slit-shaped) opening (bottomless recess) 223 Depression (bottomed recess) 224 Vertical groove (bottom recess) 225 Horizontal groove (bottomed recess) 30 Elastic part 31 Inner elastic part 31a Convex strip 31b Groove 32 outer elastic part 32a Convex strip 32b Groove 33 Upper end 34 Lower end 50 mold 51 Upper mold 52 Lower mold 53 Molding cavity 54 Material inlet 55 Filling end

Claims

1. A grommet having an annular core material and an elastic portion, which is attached between an inner wall surface of a recess and an outer wall surface of an object to be inserted into the recess, The elastic portion is provided on the inner and outer surfaces of the peripheral wall of the annular core material, A grommet characterized in that a recess is formed on the inner surface of the peripheral wall at a surface where the elastic portion is fixed.

2. In claim 1, A grommet characterized in that the recess is an opening provided in a portion of the peripheral wall in the circumferential direction, penetrating between the inside and outside of the peripheral wall.

3. In claim 1, The grommet is characterized in that the recess is a bottomed recess provided in the annular core material.

4. A method for manufacturing a grommet, the method comprising: manufacturing a grommet by insert molding using a molding die, the grommet having an annular core material and an elastic portion, the grommet being attached between an inner wall surface of a recess and an outer wall surface of an object to be inserted into the recess; A method for manufacturing a grommet, characterized in that a flow fluctuation means for fluctuating the flow of raw material for the elastic portion injected into the molding die is provided on the inner surface of the peripheral wall of the annular core material.

5. In claim 4, A method for manufacturing a grommet, characterized in that an opening penetrating the inside and outside is formed in the peripheral wall, and the raw material of the elastic part is caused to flow from the inner side of the peripheral wall of the annular core material to the outer side through the opening.

6. In claim 4, A method for manufacturing a grommet, characterized in that a bottomed recess is formed on the inner surface of the peripheral wall, and the bottomed recess slows down the flow of raw material for the elastic portion.

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