HELICAL SPRING DEVICE

Abstract

A helical spring includes a main body spring (11) and an insulator (12). The insulator is provided with a support groove (13) extending around a helical axis (O) in which a lower end portion of the main body spring fits. A lower end portion of the main body spring adheres to an inner surface (13a) of the support groove. The inner surface of the support groove is provided with a plurality of spacer projections (14) supporting an outer peripheral surface of a wire rod (W). The support groove extends at an angle range of 180° or more and 360° or less around the helical axis.and a proportion of a volume of the spacer projections occupying a space between the inner surface of the support groove and the outer peripheral surface of the wire rod in a central part of space in a circumferential direction around the helical axis is greater than that of the other parts of space in the circumferential direction.

Description

HELICAL SPRING DEVICE TECHNICAL FIELD The present invention relates to a helical spring device. Priority is claimed in Japanese Patent Application No. 2020-064642, filed on March 31, 2020, the contents of which are incorporated herein by reference. PRELIMINARY TECHNIQUE As a helical spring device used by mounting on a suspension device, conventionally, a helical spring device including a main body spring in which a wire extends vertically in a spiral form around a helical axis and an insulator supporting a lower end portion of the main body spring from below the main body spring is known. Here, the insulator is provided with a support groove extending around a helical axis and into which the lower end portion of the main body spring fits, the lower end portion of the main body spring adheres to an inner surface of the support groove, and the inner surface of the support groove is provided with a plurality of spacer projections supporting an outer peripheral surface of the wire. List of appointments Patent literature Patent document 1 Japanese unexamined patent application, first publication No. 201715249 Compendium of the invention Technical problem However, with the conventional helical spring device, there is room for improvement to reduce cost and ensure adhesive strength between the lower end portion of the main body spring and the inner surface of the support groove. The present invention is made in view of the circumstances described above, and an object of the present invention is to provide a helical spring device capable of reducing cost while ensuring adhesive strength between a lower end portion of a main body spring and an inner surface of a support groove. SOLUTION TO THE PROBLEM To solve the problems described above, a helical spring device of a first aspect of the present invention includes: a main body spring in which a wire extends vertically in a spiral form around a helical axis; and an insulator supporting a lower end portion of the main body spring from below, wherein the insulator is provided with a support groove extending around the helical axis and in which the lower end portion of the main body spring fits, wherein the lower end portion of the main body spring adheres to an inner surface of the support groove, wherein the inner surface of the support groove is provided with a plurality of spacer projections supporting an outer peripheral surface of the wire.where the support groove extends over an angle range of 180° or more and 360° or less around the helical axis, and where a proportion of a volume of the spacer projections occupying a space between the inner surface of the support groove and the outer peripheral surface of the wire rod in a central part of the space in a circumferential direction around the helical axis is greater than that of the other parts of the space in the circumferential direction. According to the present invention, the proportion of the spacer protrusion's volume that occupies the space between the inner surface of the support groove and the outer peripheral surface of the wire rod in the central part of the space in the circumferential direction is greater than that in the other parts of the space in the circumferential direction. Thus, when a compressive force is applied vertically to the main body spring, in the adhesive layer between the lower end portion of the main body spring and the inner surface of the support groove, the volume of the adhesive layer in the central part in the circumferential direction, which has a relatively low applied load, becomes smaller, while, for example, the volume of the adhesive layer in the end portion in the circumferential direction, which has a relatively high applied load, becomes larger.As a result, it is possible to guarantee strength at the end portion in the circumferential direction. Consequently, it is possible to reduce the amount of adhesive used and the cost while ensuring adhesive strength between the lower end portion of the main body spring and the inner surface of the support groove. A second aspect of the present invention is the helical spring device of the first aspect of the present invention, wherein the plurality of spacer projections is formed to have the same size and shape. In this case, since the plurality of spacer protrusions is configured to have the same size and shape, the plurality of spacer protrusions can be easily formed and the outer peripheral surface of the wire rod can be easily supported on the plurality of spacer protrusions with little bias. Advantageous effects of the invention According to the present invention, it is possible to reduce the cost while ensuring an adhesive force between a lower end portion of a main body spring and an inner surface of a support groove. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a helical spring device according to an embodiment of the present invention. Fig. 2 is a plan view showing a portion of the helical spring device of Fig. 1. Fig. 3 is a cross-sectional view taken through line lll-lll of the helical spring device shown in Fig. 2. DESCRIPTION OF MODALITIES The following describes a modality of a helical spring device according to the present invention with reference to Figs. 1 to 3 A helical spring device 1 includes a main body spring 11 in which a wire W extends vertically in a spiral form around a helical axis O and an insulator 12 that supports a lower end portion of the main body spring 11 from below the main body spring 11. That is, the vertical direction is the direction of the helical axis O. The helical spring device 1 is used by mounting it, for example, on a damper inserted in the main body spring 11 and a suspension device having a strut mount attached to the upper end of the damper or similar. The main body spring 11 is an open-ended helical spring in which an end portion w1 of wire W is vertically separated from the adjacent wire W on the inside of the helical axis direction O. The cross-sectional shape of wire W is the same along its entire length, including the end portion w1. In the example shown in the drawings, the cross-sectional shape of wire W is circular. Furthermore, a closed-end helical spring in which the end portion w1 of wire W contacts and overlaps with the wire W adjacent to the end portion w1 on the inside of the helical axis direction O can be adopted as the main body spring 11. In this configuration, the end portion w1 of wire W can be, for example, ground to form a flat surface extending in the horizontal direction orthogonal to the vertical direction and facing outwards in the vertical direction. The cross-sectional shape of wire W can be, for example, rectangular or similar. Insulator 12 is made of an elastic material such as rubber. As shown in Fig. 2, insulator 12 is arc-shaped and extends around the helical axis O when viewed from the vertical direction. Insulator 12 extends over an angle range of 180° or more and 360° or less with respect to the helical axis O. The insulator 12 is provided with a support groove 13 that extends around the helical axis O and into which the lower end portion of the main body spring 11 fits. The support groove 13 extends over an angle range of 180° or more and 360° or less with respect to the helical axis O. As shown in Fig. 3, an adhesive layer 16 is provided between an inner surface 13a of the support groove 13 and the lower end portion of the main body spring 11, where the lower end portion of the main body spring 11 is bonded to the inner surface 13a of the support groove 13. The inner surface 13a of the support groove 13 is formed in a concave curved shape along the outer peripheral surface of the wire rod W. The support groove 13 opens integrally to one side in the circumferential direction around the helical axis O, upwards, and outwards in the radial direction (orthogonal to the direction of the helical axis O). Additionally, such as support slot 13, for example, a configuration can be adopted in which the support slot opens towards both circumferential sides, a configuration in which the radial outside of the support slot is closed, or similar. The inner surface 13a of the support groove 13 is provided with a plurality of spacer projections 14 that support the outer peripheral surface of the wire rod W. The proportion of the volume of the spacer protrusion 14 that occupies the space between the inner surface 13a of the support groove 13 and the outer peripheral surface of the wire rod W exceeds 10%, and the proportion of the volume of the adhesive layer 16 that occupies the space is less than 90%. The volume of the spacer protrusion 14 also includes the volume of the space within the spacer protrusion 14 when the spacer protrusion 14 has a tubular shape. The proportion of the volume of the spacer projection 14 that occupies the space between the inner surface 13a of the support groove 13 and the outer peripheral surface of the wire rod W in the central part of the space in the circumferential direction around the helical axis O is greater than the proportion of the volume of the spacer projection 14 in the other parts of the space in the circumferential direction. That is, the proportion of the volume of the adhesive layer 16 that occupies the space in the central part of the space in the circumferential direction is smaller than the proportion of the volume of the adhesive layer 16 that occupies the space in the other parts of the space in the circumferential direction. The central part in space in the circumferential direction is a portion circumferentially interleaved by the respective portions that are located on both circumferential sides of the circumferential center in space and separated by 5% or more and 45% or less of the total circumferential length of space from the circumferential center in space (the circumferential center in space is a portion located at the same distance from one end and the other end in the circumferential direction in space). In the example shown in the drawings, the proportion of the volume of the spacer protrusion 14 that occupies space gradually decreases as the distance in the circumferential direction from the center increases, and the proportion of the volume of the adhesive layer 16 occupying space gradually increases as the distance in the circumferential direction from the center increases. At the end portion of the circumferential space, the proportion of the volume occupied by the spacer protrusion 14 is 10% or less, and the proportion of the volume occupied by the adhesive layer 16 is 90% or more. Furthermore, the proportion of the volume of the protruding spacer 14 that occupies the space may be the same throughout the entire area, excluding the central portion in a circumferential direction, or throughout the entire area, excluding the end portion in a circumferential direction. The proportion of the volume of the protruding spacer 14 that occupies the space may exceed 10% throughout the entire area. The difference between the proportion of the volume of the spacer protrusion 14 occupying the central part in the circumferential direction in space and the proportion of the volume of the spacer protrusion 14 occupying the end part in the circumferential direction in space is 80% or less. If this difference exceeds 80%, the difference in the strength of adhesive layer 16 between the central part and the end part in the circumferential direction becomes large and the durability of adhesive layer 16 may decrease. The plurality of spacer protrusions 14 are formed to have the same size and shape. That is, the number of spacer protrusions 14 per unit volume of the space in the central part in the circumferential direction is greater than that in the other parts of the space in the circumferential direction. The plurality of spacer protrusions 14 are provided on the inner surface 13a of the support groove 13 at intervals in the circumferential direction and at intervals in the radial direction. The plurality of spacer protrusions 14 are provided across the entire area on the inner surface 13a of the support groove 13. Furthermore, the number of spacer protrusions 14 per unit volume of the space can be the same throughout the entire area of ​​the space, and the size of the spacer protrusion 14 located in the central part in the circumferential direction can be larger than the size of the spacer protrusion 14 located in other portions of the space. Additionally, the plurality of spacer protrusions 14 can have different shapes. As described above, according to the helical spring device 1 of this embodiment, the proportion of the volume of the spacer protrusion 14 that occupies the space between the inner surface 13a of the support groove 13 and the outer peripheral surface of the wire rod W in the central part of the space in the circumferential direction is greater than that of the other parts of the space in the circumferential direction. Thus, when a compressive force is applied vertically to the main body spring 11, the volume of the adhesive layer 16 between the lower end portion of the main body spring 11 and the inner surface 13a of the support groove 13 in the central part in the circumferential direction, which has a relatively low applied load, becomes smaller.On the other hand, for example, the volume of the adhesive layer in the circumferential end portion, which has a relatively high applied load, is increased, thus ensuring strength in the circumferential end portion. Consequently, it is possible to reduce the amount of adhesive used and the cost while ensuring adhesive strength between the lower end portion of the main body spring 11 and the inner surface 13a of the support groove 13. Since the plurality of spacer protrusions 14 are formed to have the same size and shape, the plurality of spacer protrusions 14 can be easily formed and the outer peripheral surface of the wire rod W can be easily supported by the plurality of spacer protrusions 14 with little bias. Furthermore, the technical scope of the present invention is not limited to the modality described above, and various modifications can be made without departing from the objective of the present invention. Furthermore, the constituent elements of the above-described modality can be suitably replaced with well-known constituent elements without departing from the objective of the present invention, and the above-described modality and the modified example can be suitably combined. Industrial applicability The present invention can be used in a helical spring device comprising a main body spring and an insulator having a support slot 5 provided with a plurality of spacer projections.

Claims

1. A helical spring device characterized in that it comprises: a main body spring in which a wire rod extends vertically in a spiral form around a helical axis; and an insulator supporting a lower end portion of the main body spring from below the main body spring, wherein the insulator is provided with a support groove extending around the helical axis and in which the lower end portion of the main body spring fits, wherein the lower end portion of the main body spring adheres to an inner surface of the support groove, wherein the inner surface of the support groove is provided with a plurality of spacer projections supporting an outer peripheral surface of the wire rod, wherein the support groove extends over an angle range of 180° or more and 360° or less around the helical axis,and wherein a proportion of a volume of the spacer projections that occupies a space between the inner surface of the support groove and the outer peripheral surface of the wire rod in a central part in space in a circumferential direction around the helical axis is greater than that in other parts of space in the circumferential direction.

2. The helical spring device according to claim 1, characterized in that the plurality of spacer projections are formed to have the same size and shape.

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