Grommet

Abstract

A grommet 10 includes 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 attached to 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 recess 22 following a circumferential direction is formed on the inner and / or outer surface(s) of the peripheral wall 21.

Description

Grommet

[0001] The present invention relates to a grommet that is installed to maintain a seal between a recess and an object installed in the recess.

[0002] In conventional grommets, many have been proposed in which the inner and outer surfaces of the peripheral wall of the annular core are covered with an elastic material, taking into consideration the degree of elastic deformation and shape stability when the grommet is disposed 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). This type of annular core is typically formed by cutting or pressing a flat plate of approximately uniform thickness.

[0003] Japanese Patent Application Laid-Open No. 2008-175331

[0004] However, an object inserted and attached inside a recess may shift radially inside the recess even when grommets are arranged around it, which means that the concentricity between the recess and the object may not be ensured.

[0005] Even in such cases, there would be no problem if the grommet could follow the object, but due to the difficulty in deforming the annular core material, it may not follow the object sufficiently, and the surface pressure generated between the object and the grommet may become significantly uneven depending on the position.

[0006] In other words, if an object placed in a recess is tilted, there may be little or no surface pressure between the upper or lower part of one side of the grommet and the object. In other words, the grommet has insufficient elastic contact. In such a case, not only will the grommet not provide a sufficient seal, but the object may also shift within the recess or fall out of the recess.

[0007] The present invention was proposed in consideration of these circumstances, and its purpose is to provide a grommet that can prevent the surface pressure between the object attached to the recess and the grommet from becoming significantly uneven depending on the position.

[0008] 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 attached to 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 extending in the circumferential direction is formed on at least one of the inner and outer surfaces of the peripheral wall.

[0009] The present invention has the above-described configuration, which can prevent the surface pressure on the grommet caused by the object attached to the recess from becoming significantly uneven, thereby ensuring the sealing performance of the grommet.

[0010] 1A and 1B are explanatory diagrams of a grommet according to one embodiment of the present invention. (a) is a perspective view of the grommet, (b) is a vertical cross-sectional view taken along line X-X in (a), (c) is a perspective view of an annular core material, and (d) is an enlarged vertical cross-sectional view of part A in (c).

[0023] Fig. 1B is a schematic vertical cross-sectional view showing the procedure for attaching an object and grommet to a recess and the attached state. (a) is a perspective view showing another embodiment of the annular core material, and (b) to (e) are partial end views showing four other examples of the annular core material. (a) and (b) are diagrams showing a method for manufacturing a grommet.

[0024] Fig. 1B is a diagram showing yet another embodiment of the annular core material, where (a) is a perspective view of the annular core material and (b) is a cross-sectional view of the grommet corresponding to line Y-Y of the annular core material in (a).

[0025] Fig. 1C is an exploded front view showing a modified example of the annular core material.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. First, the basic configuration of a grommet 10 according to the embodiment will be described.

[0012] The grommet 10 according to the embodiment described below comprises annular core materials 20, 40 and an elastic portion 30 that are mounted between the inner wall surface 1a of the recess 1 and the outer wall surface 3a of the object 3 that is mounted in the recess 1. The elastic portion 30 is provided on the inner and outer surfaces of the peripheral walls 21, 45 of the annular core materials 20, 40, and recesses 22, 43 are formed along the circumferential direction on at least one of the inner and outer surfaces of the peripheral walls 21, 45 (see FIGS. 1, 5, and 6).

[0013] Next, the detailed configuration of the grommet 10 of this embodiment, the procedure for installing it in the recess 1, and various embodiments of the grommet 10 will be described with reference to Figures 1 to 3. In this specification, the position and direction of the grommet 10, such as up and down, are based on the state in which the opening 11 of the cylindrical body of the grommet 10 is oriented in the up and down direction, as shown in Figure 1.

[0014] 1 is an annular body, and an annular core material 20 is contained inside an elastic portion 30. In other words, the annular core material 20 forms a substantially cylindrical peripheral wall 21, and the elastic portions 30 are fixed to the inner and outer surfaces of the peripheral wall 21 to form the grommet 10.

[0015] As shown in Figures 1(a) and 1(b), on the surfaces of the elastic portions 30 fixed to the inside and outside of the peripheral wall 21, i.e., on the surfaces of the inner elastic portion 31 and the outer elastic portion 32, three circumferentially extending convex ridges 31a, 32a are formed with the same degree of protrusion via concave grooves 31b, 32b, at approximately the same axial height between the inner elastic portion 31 and the outer elastic portion 32.

[0016] The thicknesses of the inner elastic portion 31 and the outer elastic portion 32 are substantially the same. The protruding dimension of the ridge 31 a in the inner elastic portion 31 is substantially the same as the protruding dimension of the ridge 32 a in the outer elastic portion 32, and the depth dimension of the groove 31 b in the inner elastic portion 31 is substantially the same as the depth dimension of the groove 32 b in the outer elastic portion 32.

[0017] 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), giving the grommet 10 as a whole a convexly curved shape on both sides. The inner elastic portion 31 does not widen or narrow at the upper end 33 or the lower end 34, forming an inner diameter surface that is not distorted between the top and bottom.

[0018] The annular core member 20 used in the grommet 10 of FIG. 1 is a cylindrical body (hereinafter referred to as a spring 20A) formed by forming a wire into a spiral or coil spring shape as shown in FIGS. 1(b) and 1(c).

[0019] 1(b) to 1(d), unlike a tension coil spring, this spring 20A has no gaps within one pitch in the vertical direction, but because the cross section of the wire portion 20A1, which consists of one turn of wire, is approximately circular, discontinuous, regular recesses 22 appear in the vertical direction on the inner and outer surfaces of the annular core material 20. These recesses 22 are grooves 22a that are continuous in the circumferential direction. Note that the spring 20A may have gaps between the wire portions 20A1.

[0020] Next, with reference to FIG. 2, the manner in which the grommet 10 is used and the change in shape during use will be described.

[0021] The grommet 10 of this embodiment is attached to a recess 1 such as a round hole together with an object 3 such as a columnar or cylindrical body, and maintains the sealing of the outer periphery of the object 3 within the recess 1.

[0022] 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 irregularities on its outer surface conform to the 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 irregularities on its inner surface conform to the 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 (see the left and center diagrams in FIG. 2 for the above).

[0023] Here, we consider a case where the object 3 cannot be maintained in the recess 1 due to external forces acting on the object 3 or the mutual relationships between the dimensions of the recess 1, grommet 10, and object 3, as shown in the right diagram of Figure 2, and positional fluctuations occur due to tilt, etc.

[0024] Even if the position of the object 3 changes as shown in the right diagram of Figure 2, the present grommet 10 has recesses 22 (see Figure 1) formed on the inner and outer surfaces of the annular core material 20 along the circumferential direction, extending almost the entire circumference, so that the annular core material 20 deforms to follow the change in the position of the object 3 at one or several locations (the lower part in the example shown) of the multiple recesses 22 in the vertical direction of its peripheral wall 21.

[0025] At this time, the elastic portion 30 elastically deforms in accordance with the deformation of the annular core material 20 and the positional change of the object 3. In the case of this example, on the opposite radial side (not shown), the upper part of the annular core material 20 may deform to follow the change of the object 3.

[0026] In this way, when the annular core material 20 is deformed inward as shown in the figure, the elastic portion 30 also deforms in accordance with the deformation of the annular core material 20. In other words, because the outer elastic portion 32 is present on the outer diameter side, a surface pressure appropriate for the bent state of the annular core material 20 is generated between the outer elastic portion 32 and the inner wall surface 1a of the recess 1. Furthermore, because the inner elastic portion 31 is present on the inner diameter side, a uniform surface pressure appropriate for the bent state of the annular core material 20 is generated between the inner elastic portion 31 and the outer wall surface 3a of the object 3.

[0027] In this way, both the annular core material 20 and the elastic portion 30 of the grommet 10 deform to follow the positional fluctuation of the object 3, and the elastic portion 30 makes appropriate elastic contact with the inner wall surface 1a of the recess 1 and the outer wall surface 3a of the object 3. As a result, the seal between the recess 1 and the object 3 is ensured. In particular, since the inner and outer surfaces of the elastic portion 30 are uneven, sufficient elastic contact is made both inside and outside.

[0028] If the annular core material 20 is made of a flat plate material as in the conventional case, the annular core material 20 does not deform as shown in Figure 2 because there are no recesses 22 that promote deformation. As a result, the surface pressure between the recess 1 and the grommet 10, and the surface pressure between the grommet 10 and the object 3, may be insufficient to ensure airtightness. Furthermore, there is a risk that the object 3 may shift within the recess 1 or come out of the recess 1.

[0029] Furthermore, when a spring 20A is used for the annular core material 20 as in this embodiment, the wire portion 20A1 at each pitch in the vertical direction is separated from the adjacent wire portions 20A1 above and below (they are in contact but not fixed together), so they are prone to radial deformation in the recesses 22 (see Figure 1) between the vertical wire portions 20A1, making it easier to follow the positional fluctuations of the object 3.

[0030] The annular core 20 employed in the grommet 10 is not limited to the spring 20A, but may be any of various annular plates 20B as shown in Figures 3(a) to 3(e). Note that the perspective view shown in Figure 3(a) and the partial end view shown in Figure 3(b) are views of grommets 10 of the same shape.

[0031] 3(a) and 3(b), a plurality of recesses 22 each consisting of a groove 22a that is continuous around the entire circumference are formed at equal intervals in the vertical direction on the inner surface of an annular core 20 made of an annular plate 20B. The bottoms 22ab of the grooves 22a are thinner than the adjacent portions of the grooves 22a in the axial direction, and the bottoms 22ab are easily deformed.

[0032] The grommet 10 in Figure 3(c) has a plurality of recesses 22, each consisting of a groove 22a extending around the entire circumference, formed at the same height on the inner and outer surfaces of the annular core 20, which is made of an annular plate 20B, at the same pitch in the vertical direction. As shown in the figure, the bottoms 22ab of the grooves 22a are aligned on the inner and outer sides, making the bottoms 22ab thinner and more susceptible to deformation. The depth of the grooves 22a is similar to those in Figures 3(a) and 3(b), but the grommet 10 in Figure 3(c) is naturally more susceptible to deformation.

[0033] 3(d), a grommet 10 has a plurality of recesses 22 formed at equal intervals in the vertical direction on the inner and outer surfaces of an annular core 20 made of an annular plate 20B, the recesses 22 being made of grooves 22a that run the entire circumference, and the positions of the recesses 22 are alternated so that the positions on the inner and outer sides are different. Because the grooves 22a are formed in alternate positions on the inner and outer sides in this way, many thin-walled bottoms 22ab are formed, making it possible for the grommet 10 to conform to the object 3 at various heights.

[0034] 3(e), a plurality of recesses 22 consisting of grooves 22a extending all around the inside and outside surfaces of an annular core 20 made of an annular plate 20B are formed at equal intervals in the vertical direction, and the positions of the recesses 22 are alternately different on the inside and outside. The width of the grooves 22a is approximately the same as the width of the ridges 23 on the opposite surface, so that the vertical dimension of the thin-walled portions 24 is small, but deformation is possible.

[0035] Furthermore, although the recess 22 (groove 22a) in each grommet 10 in FIG. 3 is provided continuously around the entire circumference, it may be provided with a plurality of discontinuous grooves around the entire circumference.

[0036] Furthermore, the recesses 22 formed on the inside and outside of the peripheral wall 21 of the annular core material 20 include small recesses (dimples) such as circular, elliptical, or rectangular recesses formed discontinuously along the circumferential direction. Although such recesses 22 are formed as a plurality of discontinuous small recesses, if they are formed around the entire circumference, they will be softer in the vertical direction than areas where recesses 22 are not formed, and will be more likely to bend in the radial direction. Note that the small recesses formed discontinuously in the circumferential direction may be through-openings instead of dimples.

[0037] Furthermore, it is desirable to provide a plurality of recesses 22 at approximately equal intervals in the vertical direction so that the grommet 10 can be deformed at more locations in the vertical direction, but it is also possible to provide only one recess 22 in the vertical direction.

[0038] Next, a method for manufacturing the grommet 10 will be described with reference to Figures 4(a) and 4(b). Figure 4 shows an example of the grommet 10 similar to that shown in Figure 1, but using a spring 20A as the annular core member 20.

[0039] The grommet 10 is manufactured by insert molding using a molding die 50 consisting of an upper and lower die. The molding die 50 has an upper die 51 and a lower die 52, and the internal space between the upper die 51 and the lower die 52 is provided with a molding cavity 53 into which the raw material of the elastic portion 30 is filled.

[0040] In this manufacturing method, first, the annular core material 20 (spring 20A) is placed in the molding cavity 53 on the lower mold 52 side, the upper mold 51 is attached, and the raw material of the elastic portion 30 is injected through the material injection port 54. Thereafter, the grommet 10 is obtained by demolding it from the molding mold 50.

[0041] In this way, the grommet 10 shown in Figure 1 is manufactured by insert molding in such a way that the entire surface of the annular core material 20 is covered so as to be in close contact with the elastic portion 30, so that the annular core material 20 is less likely to move or shift in the vertical direction within the elastic portion 30.

[0042] The spring 20A having gaps between the wire portions 20A1 is not limited to a tension coil spring in which the wire portions 20A1 are opened during molding as described above, but may be a compression coil spring in which the wire portions 20A1 are already opened before molding.

[0043] Furthermore, the spring 20A used in the annular core member 20 is not limited to the round wire coil spring shown in FIG. 1(c), but may be a deformed wire coil spring such as a rectangular wire coil spring.

[0044] Next, another embodiment will be described. In the grommet 10, an annular core 40 having a configuration as shown in Fig. 5(a) can be used instead of the annular core 20 illustrated in Figs. 1 and 3.

[0045] The annular core 40 shown in Fig. 5(a) is a laminated ring body 40A made of a single wire, and is a cylindrical body formed into a coil spring shape (hereinafter referred to as a wave spring body 40A). Note that although a rectangular wire is used as the wire in the annular core 40 of Fig. 5, other irregularly shaped wires may also be used.

[0046] The wave spring body 40A is a spring material known as a coiled wave spring, and is used as a coil spring (mainly a compression coil spring).

[0047] The basic structure of the laminated ring body 40A made up of wave spring bodies 40A will be described with reference to Figures 5(a) and 5(b). Figure 5(b) is a longitudinal cross-sectional view of the grommet corresponding to line Y-Y of the annular core member 40 in Figure 5(a). Note that the various parts (reference numerals 31, etc.) of the elastic portion 30 in Figure 5(b) are the same as those in Figure 1(b), and therefore the same reference numerals are used and their description will be omitted.

[0048] The laminated ring body 40A has multiple stages of ring portions 40A1, each made of wire rod that extends around the annular core material 40, and these multiple ring portions 40A1 are formed from a single continuous wire rod. The ring portions 40A1 have peaks 41 and valleys 42 with amplitudes that extend along the axial direction of the laminated ring body 40A, alternating in the circumferential direction. Two adjacent ring portions 40A1 are arranged vertically such that the upper peak 41 faces the lower valley 42, and a through opening 43 is formed as a recess 43 between the opposing peaks 41 and valleys 42. The recesses 43 required for the annular core material 40 are formed by multiple through openings 43 formed along the circumferential direction and penetrating the peripheral wall 45.

[0049] As shown in FIG. 5A, the through openings 43 are discontinuous in the circumferential direction, being partitioned by contact portions 44, but the plurality of through openings 43 are formed periodically over the entire circumference.

[0050] First, the detailed structure and shape of the wave spring body 40A will be described with reference to the perspective view of FIG.

[0051] The wave spring 40A is formed by forming a single wire into a spiral shape with periodic waveforms. Each of the multiple ring sections 40A1 that make up the wave spring 40A has a periodic waveform consisting of peaks 41 and valleys 42 with the same wavelength and amplitude.

[0052] In the wave spring body 40A in its natural state, the peaks 41 and the valleys 42 of the ring portion 40A1 below them are positioned vertically apart, and the valleys 42 are in contact with the peaks 41 of the ring portion 40A1 below them.

[0053] In this way, the wave spring body 40A is formed with adjacent ring portions 40A1 on the top and bottom being offset by half a period. In the example of Figure 5(a), four and a half periods of peaks 41 and valleys 42 are formed per ring portion 40A1. Of course, this period is not limited to this.

[0054] As a result, the valley portions 42 of the upper ring portion 40A1 are arranged above the peak portions 41 of the ring portion 40A1, and the valley portions 42 of the lower ring portion 40A1 are arranged below the peak portions 41 of the ring portion 40A1. Furthermore, the peak portions 41 of the upper ring portion 40A1 are arranged above the valley portions 42 of the ring portion 40A1, and the peak portions 41 of the lower ring portion 40A1 are arranged below the valley portions 42 of the ring portion 40A1.

[0055] Furthermore, since all of the ring portions 40A1 have the same wavelength and the same amplitude, as shown in Figure 5(a), through openings 43 of approximately the same shape appear between the peaks 41 and valleys 42 between the upper and lower ring portions 40A1, while contact portions 44 appear between the valleys 42 and peaks 41 between the upper and lower ring portions 40A1. Thus, through openings 43 and contact portions 44 appear periodically in the circumferential direction for the ring portion 40A1.

[0056] Before manufacturing the grommet 10, the wave spring body 40A may be one in which the contact portions 44 between the upper and lower valley portions 42 and peak portions 41 are fixed to each other, or may not be one in which the contact portions 44 are fixed to each other.

[0057] Here, the principle of elastic deformation of the wave spring body 40A (coiled wave spring) will be briefly explained.

[0058] When a load is applied in the axial direction, the shape of the through opening 43 of the wave spring body 40A deforms, expanding or narrowing in the vertical direction. This generates a repulsive force in the direction opposite to the applied load, but the force may also be dispersed to the side. In other words, like the spring 20A shown in Figure 1(c), the axis may shift and the spring may become bent as shown in Figure 2(c).

[0059] The grommet 10 having the wave spring body 40A as the annular core material 40 (see Figure 5 (b)) can be manufactured by the manufacturing method shown in Figure 4, similar to the grommet 10 having the annular core material 20 shown in Figure 1.

[0060] When the molding die 50 and manufacturing method shown in FIG. 4 are used, the wave spring body 40A has a through opening 43 that communicates with the inside and outside via the peripheral wall 45, which facilitates the flow of raw materials between the inside and outside of the annular core material 40, thereby preventing uneven distribution of raw materials within the molding die 50.

[0061] The through opening 43 of the laminated ring body 40A in the grommet 10 thus formed is filled with the elastic material (see FIG. 5(b)).

[0062] Furthermore, since the raw material flows smoothly through the through openings 43 of the peripheral wall 45, the peripheral wall 45 itself is prevented from interfering with the flow of the raw material. In other words, the possibility that the peripheral wall 45 will be deformed by the injection pressure of the raw material is reduced, and the laminated ring body 40A can be maintained in a stable state within the molding die 50. In particular, since the one shown in FIG. 5 uses rectangular wire as the wire material, there is little resistance to the raw material flowing through the through openings 43. It is desirable that the laminated ring body 40A be restrained from above and below within the molding die 50.

[0063] Furthermore, the wave spring body 40A has a good sense of stability when placed because the upper and lower ring portions 40A1 are in contact with each other at multiple contact portions 44. Furthermore, the wave spring body 40A can be placed stably if the cycle of the peaks 41 and valleys 42 is set to three or more cycles. If the contact portions 44 are fixed between the upper and lower ring portions 40A1, the wave spring body 40A will have a particularly good sense of stability.

[0064] In this way, the laminated ring body 40A has a high degree of rigidity that allows it to withstand the injection pressure, at least during the manufacturing stage, and is more stable within the molding die 50 than other coil springs, making molding errors less likely to occur and improving the yield of the grommet 10.

[0065] The compression coil spring (not shown) also has a clearance space (through opening) that penetrates from the inside to the outside around the entire circumference between the upper and lower ring portions, but there is no contact between the upper and lower ring portions. Therefore, when raw material is circulated, the longer the spring is in the axial direction, the more likely it is to bend midway along the axis due to injection pressure, making it difficult to maintain a stable shape.

[0066] Furthermore, the wave spring body 40A is easy to handle because it is formed entirely from a single wire rod, and when placed in the forming die 50, if the dimensions match, no processing is required and it can be used as is, making it easy to use.

[0067] A grommet 10 (see Figure 5(b)) formed using a laminated ring body 40A as an annular core material 40 deforms to follow the movement of the object 3 when a load is applied during use as illustrated in Figure 2 due to the expansion and contraction of the through opening 43 of the annular core material 40 and the elasticity of the elastic portion 30.

[0068] In particular, when the grommet 10 formed by the annular core material 40 is bent (axially misaligned), the wave spring body 40A may be in a state in which the through opening 43 narrows between the top and bottom in some parts of the circumferential direction and widens in other parts. Therefore, the grommet 10 can be used in a manner in which the coaxiality of the grommet 10 is misaligned, as shown in FIG.

[0069] Therefore, with the grommet 10 having the annular core material 40, it is possible to prevent the surface pressure of the object 3 attached to the recess 1 from becoming significantly uneven, as described above with reference to Fig. 2. This makes it possible to ensure the sealing performance of the grommet 10.

[0070] After the grommet 10 is formed using the wave spring body 40A, the contact portion 44 between the upper and lower ring portions 40A1 is fixed due to the hardening of the raw material during molding. Therefore, even if the coaxiality is shifted when the grommet 10 is in use, it is possible to prevent either of the upper and lower ring portions 40A1 from shifting in the wall thickness direction of the peripheral wall 45 at the contact portion 44 or to prevent the upper and lower ring portions 40A1 from separating.

[0071] Since the contact portion 44 is fixed when the grommet 10 is molded using the molding die 50, it does not need to be glued when placed in the molding die 50, but it is desirable to glue it in advance to prevent the two ring portions 40A1 at the contact portion 44 from shifting or separating due to the injection pressure within the molding die 50.

[0072] As described above, the laminated ring body 40A exhibits appropriate rigidity during the manufacturing stage of the grommet 10, and the laminated ring body 40A exhibits ease of deformation when the manufactured grommet 10 is used.

[0073] A laminated washer body 40B as shown in Fig. 6 may be used as the annular core member 40. Fig. 6 is an exploded front view of the laminated washer body 40B. The laminated washer body 40B is formed by stacking wave washers (wave washers 400) formed from a single wire rod.

[0074] Each ring portion 40B1 in the stacked washer body 40B is made up of one wave washer 400, and adjacent ring portions 40B1 on the top and bottom are separate wave washers 400. In other words, the stacked washer body 40B is made up of wave washers 400 stacked one on top of the other as shown in FIG.

[0075] The wave washers 400 used in the stacked washer body 40B have the same shape. Each of the ring portions 40B1 has a waveform consisting of peaks 41 and valleys 42 with the same period and amplitude.

[0076] By stacking the wave washers 400 with a shift of half a period, through openings 43 are formed between the peaks 41 of the upper ring portion 40B1 and the valleys 42 of the lower ring portion 40B1, and the valleys 42 of the upper ring portion 40B1 come into contact with the peaks 41 of the lower ring portion 40B1. Note that it is desirable to fix the contact portions 44 between the upper and lower valleys 42 and peaks 41 before molding the grommet 10 in the molding die 50.

[0077] By stacking the wave washers 400 in this manner, periodic through-openings 43 appear along the circumferential direction. In the example shown in Fig. 6, three periods of peaks 41 and valleys 42 are formed for one ring portion 40B1.

[0078] The wave washer 400 used in the laminated washer body 40B can be said to be a type of spring washer in that it uses elasticity to prevent loosening, but it differs from a typical spring washer (one in which a portion is cut and twisted to create a step) in that the load is distributed evenly.

[0079] In the stacked washer body 40B formed in this manner by a plurality of wave washers 400, when a load is applied in the axial direction, the through opening 43 between the upper and lower ring portions 40B1 expands and contracts due to the elasticity of the wave washers 400. Also, like the wave spring body 40A in FIG. 5(a), the axis may be misaligned and the stacked washer body 40B may become bent.

[0080] As described above, the grommet 10 may be formed using the laminated ring body 40B as shown in FIG. 6, and the laminated ring body 40B can also provide the same effects as the grommet 10 shown in FIG. 5(b).

[0081] The grommet 10 according to the various embodiments described above is merely an example, and other configurations are also acceptable. It goes without saying that the overall shape of the grommet 10 can be appropriately changed as a design matter. Furthermore, the entire surface of the annular core 20, 40 does not necessarily have to be covered by the elastic portion 30, and a portion of the outer or inner surface of the peripheral wall 21, 45 may be exposed.

[0082] Furthermore, the manufacturing method of the grommet 10 is not limited to the insert molding shown in FIG.

[0083] REFERENCE SIGNS LIST 1 recess 1a inner wall surface 3 object 3a outer wall surface 10 grommet 11 opening 20 annular core material 20A spring 20A1 wire rod portion 20B annular plate body 21 peripheral wall 22 recess 22a groove portion 22ab bottom portion 23 ridge 24 thin-walled portion 30 elastic portion 31 inner elastic portion 31a ridge 31b groove 32 outer elastic portion 32a ridge 32b groove 33 upper end portion 34 lower end portion 40 annular core material (laminated ring body) 40A laminated ring body (wave spring body) 40A1 ring portion 41 peak portion 42 valley portion 43 recess (through opening) 44 contact portion 45 peripheral wall 50 forming mold 51 upper mold 52 Lower mold 53 Molding cavity 54 Material injection port

Claims

1. A grommet comprising an annular core material and an elastic part, which is fitted between the inner wall surface of a recess and the outer wall surface of an object fitted into said recess, wherein the elastic part is provided on the inner and outer surfaces of the peripheral wall of said annular core material, and a recess is formed along the circumferential direction on at least one of the inner and outer surfaces of said peripheral wall.

2. A grommet according to claim 1, wherein the recess is formed as a groove portion that continues in the circumferential direction on at least one of the inner and outer surfaces of the peripheral wall.

3. A grommet according to claim 1, wherein the recess is a groove extending in the circumferential direction, and the bottom of the groove is thinner than the adjacent portion of the groove in the axial direction.

4. A grommet according to claim 1, characterized in that the annular core material is a spring.

5. A grommet as claimed in claim 1, wherein the annular core material is made of wire material and comprises a laminated ring body having multiple stages of ring portions each consisting of one circumference of the wire material, the ring portions have peaks and valleys of amplitude along the axial direction of the laminated ring body, alternating in the circumferential direction, the laminated ring body having two adjacent ring portions arranged vertically such that the upper peak and the lower valley face each other, and a through opening is formed between the opposing peaks and valleys, and the recesses are made up of a plurality of through openings formed along the circumferential direction and penetrating the peripheral wall.

6. A grommet according to claim 5, wherein the laminated ring body is a coiled wave spring formed by connecting the ring portions.

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