Spring plunger and method of manufacturing same

Abstract

The spring plunger (1) extends along an axis (L), is open at least on the second direction side (X2), and has a cylindrical shape that is rotationally symmetrical with respect to the axis (L), and includes a protrusion (2) having a tip portion (21) located on the first direction side (X1) and a rear end portion (22) that is connected to the second direction side (X2) of the tip portion (21) and has a larger inner diameter than the tip portion (21), and a spring (3) having a compression spring structure extending coaxially with the protrusion (2), the end portion on the first direction side (X1) being lightly pressed into the inside of the tip portion of the protrusion (2) and being integrated with the protrusion (2), and the second direction side (X2) protruding from the rear end portion (22) of the protrusion (2) in an uncompressed state. This spring plunger (1) is easy to install in a device, the spring load can be finely adjusted, and the spring (3) is unlikely to tilt.

Description

[Technical field]

[0001] The present invention relates to a spring plunger and a method for manufacturing the same. [Background technology]

[0002] In order to obtain a good clicking sensation when operating a switch device or the like, a spring plunger is used which includes a spring having a compression spring structure and a protrusion such as a ball, pin, or cap that is biased by the spring (see, for example, Patent Document 1).

[0003] The switch device disclosed in Patent Document 1 includes a case (31), a cam (37) that rotates at a position facing the bottom of the case (31), and a spring plunger disposed in a hollow portion (37d) of the cam (37) so as to be in sliding contact with the bottom of the case (31). The spring plunger is composed of a spring (41) and a hollow cap-shaped protrusion (40) biased by the spring (41). In the switch device disclosed in Patent Document 1, the spring plunger fits into a detent valley (31d) that sandwiches a detent ridge (31c) formed on the bottom of the case (31) to determine the rotational position of the cam (37), providing a good operational feel.

[0004] In addition, in the spring plunger used in the switch device disclosed in Patent Document 1, the prong (40) and the spring (41) are not integrated, and their relative positions are fixed only after they are assembled into the device, making handling them until assembly difficult. However, spring plungers that make handling easier until assembly are now available (see, for example, Non-Patent Document 1).

[0005] The spring plunger disclosed in Non-Patent Document 1 consists of a hollow cap-shaped protrusion and a spring inserted into the protrusion. This spring plunger has a protrusion (dowel) formed at one point on the inner peripheral surface by striking the peripheral wall of the protrusion from the outer circumferential side inward with a punch or the like, and the spring inserted into the protrusion gets caught on this protrusion and does not come out, so that the protrusion and the spring are integrated. As a result, when the spring plunger disclosed in Non-Patent Document 1 is incorporated into a device, the protrusion and the spring do not separate and can be handled as a single unit, making it easy to incorporate into the device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-134641 [Non-patent literature]

[0007] [Non-Patent Document 1] http: / / konishi-mfg.com / goods / plun / gn31.php Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the spring plunger disclosed in Non-Patent Document 1, the spring is caught by a protrusion on the inner circumferential surface of the protrusion and fixed to the protrusion, so that the total length adjustment (adjustment of the spring protrusion) can only be done in units of the winding pitch of the spring, which can lead to poor load accuracy. Also, in the spring plunger disclosed in Non-Patent Document 1, the spring is fixed by a protrusion that protrudes laterally from one point on the inner circumferential surface, so that in particular when the gap (clearance) between the inner diameter dimension of the protrusion and the outer diameter dimension of the spring is large, the spring is fixed at an angle to the protrusion and movement accuracy can be poor.

[0009] In view of the above, an object of the present invention is to provide a spring plunger that is easy to install in a device, allows fine adjustment of the spring load, and is less likely to tilt, and also to provide a method for manufacturing such a spring plunger. [Means for solving the problem]

[0010] In order to solve the above problems, the spring plunger according to the present invention comprises: a protrusion extending along an axis extending from a first direction side to a second direction side, opening at least on the second direction side, having a cylindrical shape rotationally symmetrical with respect to the axis, the protrusion including a tip portion located on the first direction side, and a rear end portion connected to the second direction side of the tip portion and having an inner diameter larger than that of the tip portion; a spring having a compression spring structure extending coaxially with the protrusion, the end on the first direction side being lightly pressed into the inside of the tip end of the protrusion to be integrated with the protrusion, and the spring having a second direction side protruding from the rear end of the protrusion in an uncompressed state; The present invention is characterized by comprising:

[0011] In the spring plunger according to the present invention, the end face of the protrusion on the first direction side is semispherical.

[0012] In the spring plunger according to the present invention, a gap is ensured between the rear end of the projection and the spring.

[0013] In addition, the spring plunger according to the present invention may be configured so that the inside diameter of the tip portion is constant or gradually increases in the second direction.

[0014] In addition, in the spring plunger of the present invention, one or more crimping grooves may be formed in the tip portion, which are recessed around the outer circumferential surface so that the inner circumferential surface is pushed out and protruded around the entire circumference.

[0015] The method for manufacturing a spring plunger according to the present invention includes the steps of: a protrusion setting process for setting a protrusion that extends along an axis extending from a first direction side to a second direction side, has a cylindrical shape that is rotationally symmetrical with respect to the axis, and has a tip portion located on the first direction side and a rear end portion connected to the second direction side of the tip portion and having an inner diameter dimension larger than that of the tip portion; a light press-fitting process in which a spring having a compression spring structure is applied with a compressive force from a second direction side to the protrusion set in the protrusion setting process, and the end portion on the first direction side is lightly pressed and fitted to be integrated with the protrusion; The present invention is characterized in that it includes:

[0016] The method of manufacturing a spring plunger according to the present invention may further include an overall length adjustment step of releasing the compressive force applied in the light press-fitting step, protruding the second direction side of the spring from the rear end of the projection, and applying a compressive or tensile force to the protruding portion of the spring as necessary to keep the overall length within a predetermined range.

[0017] The method for manufacturing a spring plunger according to the present invention may further include, after the light press-fitting step, a crimping step in which one or more of the outer circumferential surfaces of the tip of the protrusion are pressed inward along the entire circumference to extrude the inner circumferential surface of the protrusion along the entire circumference.

[0018] In the method for manufacturing a spring plunger according to the present invention, in the light press-fitting step, the spring may be lightly press-fitted into the plunger while checking the reaction force of the spring. Effect of the Invention

[0019] According to the present invention, it is possible to provide a spring plunger that is easy to install in a device, allows fine adjustment of the spring load, and is less likely to tilt. Also, according to the present invention, it is possible to provide a method for manufacturing such a spring plunger. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an external view of a spring plunger according to a first embodiment. [Diagram 2] FIG. 2 is a longitudinal sectional view of the spring plunger of FIG. 1. [Diagram 3] 4 is a flowchart showing a method for manufacturing the spring plunger according to the first embodiment. [Figure 4] FIG. 11 is a vertical cross-sectional view of a spring plunger according to a second embodiment. [Diagram 5] FIG. 11 is a vertical cross-sectional view of a spring plunger according to a third embodiment. [Figure 6] 10 is a flowchart showing a method for manufacturing a spring plunger according to a third embodiment. [Figure 7] FIG. 13 is an external view showing a modified example of the protrusion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A spring plunger according to an embodiment of the present invention will be described below with reference to the drawings. Note that the drawings do not necessarily strictly reflect the actual dimensions.

[0022] [Embodiment 1] (Spring plunger 1 configuration) Fig. 1 is an external view showing the appearance of the spring plunger 1 of embodiment 1, and Fig. 2 is a longitudinal sectional view thereof. The spring plunger 1 of embodiment 1 is used, for example, in intermittent switches such as dial switches and slide switches, movement mechanisms, etc., to constitute a positioning mechanism, a click mechanism, a stopper mechanism, etc. by sliding against a mating part having a ridge, groove, hole, etc.

[0023] As shown in Figures 1 and 2, the spring plunger 1 includes a cylindrical projection 2 extending along an axis L extending from a first direction side X1 to a second direction side X2, and a spring 3 having a compression spring structure, with at least the end portion on the first direction side X1 fitted into the cylindrical projection 2.

[0024] The protrusion 2 is made of metal or resin, has a hemispherical end face on the first direction side X1, is open on the second direction side X2, and has a bottomed cylindrical shape that is rotationally symmetrical with respect to the axis L. The protrusion 2 has a thin, uniform side wall. The protrusion 2 comprises a tip portion 21 located on the first direction side X1, and a rear end portion 22 connected to the tip portion 21 on the second direction side X2.

[0025] The tip portion 21 is composed of a hemispherical portion 21a on the first direction side X1 and a cylindrical portion 21b that has a constant inner diameter and extends straight from the end of the hemispherical portion 21a toward the second direction side X2 for a predetermined length. The cylindrical portion 21b of the tip portion 21 has an inner diameter dimension that allows the spring 3 described below to be lightly pressed into it, and a length dimension that allows the spring 3 to be held when the spring 3 is lightly pressed into it.

[0026] The rear end 22 is composed of a tapered portion 22a that is connected to the front end 21 and gradually expands in diameter toward the second direction side X2, and a cylindrical portion 22b that has a constant inner diameter and extends straight from the end of the tapered portion 22a toward the second direction side X2 for a predetermined length. The inner diameter of the cylindrical portion 22b of the rear end 22 is set so as to be larger than the inner diameter of the cylindrical portion 21b of the front end 21 and the outer diameter of the spring 3 described below. The length of the rear end 22 is set appropriately based on the location where it is installed, the amount by which the spring 3 is desired to enter the protrusion 2 when compressed, the method of restricting the collapse of the spring 3, etc. The rear end 22 may have chamfered corners on the inner diameter side of the mouth to make it easier to guide the spring 3 when pressing in the spring 3, chamfered corners on the outer diameter side of the mouth to make it easier to slide against the mating side when in use, or may have protrusions arranged in rotational symmetry around the periphery to make it harder to rotate relative to the mating side when in use.

[0027] The spring 3 is a so-called coil spring having a compression spring structure, and extends coaxially with the projection 2. The spring 3 is wound at an equal pitch with a constant diameter, and its end on the first direction side X1 is lightly pressed into the inside of the tip end 21 of the projection 2 to be integrated with the projection 2. When not compressed, the spring 3 has its second direction side X2 protruding from the rear end 22 of the projection 2. A gap is secured between the inner wall surface of the rear end 22 of the projection 2 and the spring 3, and the spring 3 expands and contracts smoothly within the rear end 22 of the projection 2.

[0028] The spring plunger 1 thus constructed, with the protrusion 2 and the spring 3 integrated, is installed, for example, in a bottomed hole formed in a member to be incorporated and used. In the installed spring plunger 1, when the tip 21 of the protrusion 2 is pressed toward the second direction side X2 with the end face on the second direction side of the spring 3 abutting against a fixed surface of the member to be incorporated, the portion of the spring 3 located on the second direction side relative to the tip 21 of the protrusion 2 is deflected and its overall length is shortened, and a biasing force (reaction force) that tries to push the tip 21 of the protrusion 2 back toward the first direction side X1 is generated according to the amount of deflection.

[0029] (Method of manufacturing the spring plunger 1) Fig. 3 is a flowchart showing a manufacturing method of the spring plunger 1 according to embodiment 1. Next, the manufacturing method of the spring plunger 1 will be described with reference to Fig. 3. As shown in Fig. 3, the spring plunger 1 is manufactured through a thrust setting process ST1, a light press-fitting process ST2, a total length adjustment process ST3, a reaction force measurement process ST4, and an appearance inspection process ST5, in that order.

[0030] First, in the prong setting step ST1, the prong 2 is set in the manufacturing equipment with the semispherical portion 21a of the tip 21 facing the first direction side X1.

[0031] Next, in the light pressing process ST2, the spring 3 is set in a position coaxial with the second direction side X2 of the projection 2 set in the projection setting process ST1, and a compressive force is applied to the spring 3 from the second direction side X2 to lightly press and fit the end of the spring 3 on the first direction side X1 into the tip 21 of the projection 2, thereby integrating the spring 3 with the projection 2.

[0032] Next, in the overall length adjustment process ST3, the compressive force applied in the light press-fitting process ST2 is released, and the second direction side X2 of the spring 3 is caused to protrude from the rear end 22 of the protrusion 2. Then, the overall length of the spring plunger 1 or the protrusion length of the spring 3 from the protrusion 2 is measured, and if it is longer than specified, a compressive force is applied to the spring 3 from the second direction side X2, and if it is shorter than specified, a tensile force is applied to the spring 3 toward the second direction side X2, thereby adjusting the overall length of the spring plunger 1 to fall within a predetermined range.

[0033] Next, in the reaction force measuring process ST4, the spring plunger 1 whose overall length has been adjusted in the overall length adjusting process ST3 is deflected, and an inspection device including a pressure gauge is used to measure whether the reaction force is within a predetermined range.

[0034] Next, in the appearance inspection process ST5, the final appearance is inspected by visual inspection or with an inspection device including a camera to check whether the spring 3 has fallen off, whether the spring 3 is installed at an angle, whether the total length is within a specified range, whether the outer diameter is within a specified range, whether there are scratches or dents that would cause defects, etc. The spring plunger 1 is completed through the above processes.

[0035] (Action and effect) The spring plunger 1 of the first embodiment has a cylindrical shape rotationally symmetrical with respect to the axis L, and includes a protrusion 2 having a tip portion 21 located on the first direction side X1 and a rear end portion 22 connected to the second direction side X2 of the tip portion 21 and having an inner diameter larger than that of the tip portion 21, and a spring 3 that is lightly pressed into the inside of the tip portion 21 of the protrusion 2 and is integrated with the protrusion 2, and the second direction side X2 protrudes from the rear end portion 22 of the protrusion 2 in an uncompressed state. That is, in the spring plunger 1, the spring 3 is lightly pressed into the tip portion 21 of the protrusion 2, and a part of the outer circumferential surface of the first direction side X1 of the spring 3 is held evenly, so that the protrusion 2 and the spring 3 are integrated. Therefore, the spring plunger 1 is easy to handle and easy to install in a device because the protrusion 2 and the spring 3 are integrated. Furthermore, with the spring plunger 1, the outer peripheral surface of the spring 3 is held by light press-fitting on the tip 21 of the protrusion 2, so it is possible to shift the positional relationship between the protrusion 2 and the spring 3 in the axial direction without separating them. Furthermore, with the spring plunger 1, the outer peripheral surface of the spring 3 is evenly held on the tip 21 of the protrusion 2, so the spring 3 is unlikely to tilt relative to the protrusion 2. Therefore, the spring plunger 1 is easy to incorporate into a device, allows fine adjustment of the spring load, and is a spring plunger that is unlikely to tilt.

[0036] In addition, according to the spring plunger 1, the end face of the protrusion 2 on the first direction side X1 is hemispherical, so that when the spring plunger 1 is incorporated into a device, it can smoothly slide against a mating part that has ridges, grooves, holes, etc.

[0037] Furthermore, according to the spring plunger 1, a gap is secured between the rear end portion 22 of the projection 2 and the spring 3, so that the spring 3 can move smoothly when expanding and contracting.

[0038] The manufacturing method of the spring plunger 1 of the first embodiment includes a projection setting step ST1 for setting the projection 2, and a light press-fitting step ST2 for lightly press-fitting the spring 3 into the projection 2 to integrate it with the projection 2. According to this manufacturing method, it is possible to manufacture the spring plunger 1 in which the projection 2 and the spring 3 are integrated, which provides the above-mentioned effects.

[0039] Furthermore, in the manufacturing method of the spring plunger 1 of embodiment 1, the compressive force applied in the light pressing process ST2 is released, the spring 3 is protruded from the protruding member 2, and an overall length adjustment process ST3 is performed in which a compressive or tensile force is applied to the protruding portion of the spring 3 as necessary to keep the overall length within a predetermined range, so that a spring plunger 1 with good overall length accuracy can be manufactured.

[0040] Furthermore, in the manufacturing method of the spring plunger 1 of embodiment 1, a reaction force measurement process ST4 is performed in which the spring plunger 1 is bent and the reaction force is measured to see if it falls within a specified range, so that a spring plunger 1 with good accuracy in the biasing force of the protrusion 2 can be manufactured.

[0041] [Embodiment 2] Fig. 4 is a vertical cross-sectional view of the spring plunger 101 according to the second embodiment. The spring plunger 101 according to the second embodiment has a basic configuration similar to that of the spring plunger 1 according to the first embodiment, but the shape of the protrusion is slightly different from that of the spring plunger 1 according to the first embodiment. The spring plunger 101 according to the second embodiment will be described below. Note that the shape of the spring 3 is similar to that of the first embodiment, and therefore the same reference numerals in Fig. 4 as those in Fig. 2 are used, and description thereof will be omitted.

[0042] In the spring plunger 101, the protrusion 102 has a hemispherical end face on the first direction side X1, is open on the second direction side X2, and has a bottomed cylindrical shape that is rotationally symmetrical with respect to the axis L. The protrusion 102 has a thin, uniform side wall. The protrusion 102 consists of a tip portion 121 located on the first direction side X1, and a rear end portion 122 that connects to the tip portion 121 on the second direction side X2.

[0043] The tip portion 121 is composed of a hemispherical portion 121a on the first direction side X1 and a tapered cylindrical portion 121b whose inner diameter gradually increases from the end of the hemispherical portion 121a toward the second direction side X2, unlike in embodiment 1. The tapered cylindrical portion 121b of the tip portion 121 has a tapered inner diameter dimension that is specified so that the spring 3 is lightly press-fitted into it.

[0044] The rear end 122 has a constant inner diameter and extends straight a predetermined length toward the second direction side X2 from the end of the tapered cylindrical portion 121b of the front end 121. The inner diameter of the rear end 122 is set so as to be larger than the inner diameter of the front end 121 and the outer diameter of the spring 3.

[0045] In the spring plunger 101, the inner diameter dimension of the tip portion 121 gradually increases toward the second direction side X2, but similar to the spring plunger 1 of the first embodiment, the spring 3 is lightly press-fitted into the tip portion 121 of the protrusion 102 and a part of the outer circumferential surface of the spring 3 on the first direction side X1 is held uniform, thereby integrating the protrusion 102 and the spring 3. Therefore, the spring plunger 101 has the same effects as the spring plunger 1 of the first embodiment described above.

[0046] [Embodiment 3] FIG. 5 is a vertical cross-sectional view of a spring plunger 201 according to the third embodiment, and FIG. 6 is a flow chart showing a method for manufacturing the spring plunger 201. The spring plunger 201 according to the third embodiment has a basic configuration similar to that of the spring plunger 1 according to the first embodiment, but the shape of the protrusion is slightly different from that of the spring plunger 1 according to the first embodiment, and the manufacturing method is also slightly different in order to form the different shape. The spring plunger 201 according to the third embodiment will be described below. Note that the shape of the spring 3 is similar to that of the first embodiment, and therefore the same reference numerals in FIG. 5 as those in FIG. 2 are used, and description thereof will be omitted.

[0047] In the spring plunger 201, the protrusion 202 has a hemispherical end face on the first direction side X1, is open on the second direction side X2, and has a bottomed cylindrical shape that is rotationally symmetrical with respect to the axis L. The protrusion 202 has a thin, uniform side wall. The protrusion 202 is composed of a tip portion 221 located on the first direction side X1, and a rear end portion 222 connected to the tip portion 221 on the second direction side X2.

[0048] The tip portion 221 is composed of a hemispherical portion 221a on the first direction side X1 and a cylindrical portion 221b extending a predetermined length from the end of the hemispherical portion 221a toward the second direction side X2. The cylindrical portion 221b of the tip portion 221 has an inner diameter dimension defined so that the spring 3 is lightly press-fitted, and a length dimension defined so that the spring 3 can be held when the spring 3 is lightly press-fitted, in that it is similar to the cylindrical portion 21b of the tip portion 21 of the first embodiment. However, the cylindrical portion 221b of the tip portion 221 has a different shape from the cylindrical portion 21b of the tip portion 21 of the first embodiment in that a plurality of crimping grooves 221c are formed by recessing the periphery of the outer periphery so that the inner periphery is pushed out and protruded all around.

[0049] The rear end 222 is made up of a tapered portion 222a that is connected to the front end 221 and gradually expands in diameter toward the second direction side X2, and a cylindrical portion 222b that has a constant inner diameter and extends straight from the end of the tapered portion 222a toward the second direction side X2 for a predetermined length. The rear end 222 has the same shape as the rear end 22 of the first embodiment.

[0050] As shown in FIG. 6, the spring plunger 201 is manufactured through a thrust setting process ST1, a light press-fitting process ST2, a total length adjusting process ST3, a reaction force measuring process ST4, a crimping process ST6, and an appearance inspection process ST5.

[0051] The thrust setting process ST1, the light press-fitting process ST2, the overall length adjustment process ST3, the reaction force measuring process ST4, and the appearance inspection process ST5 are similar to those in the first embodiment, and therefore description thereof will be omitted.

[0052] In the crimping process ST6, after the light press-fitting process ST2, after the compressive force is released in the full length adjustment process ST3, or after the reaction force is measured in the reaction force measurement process ST4 (FIG. 6 shows after the reaction force measurement process ST4 as an example), the outer circumferential surface of the tip 221 of the protrusion 202 is pressed inward all around to extrude the inner circumferential surface of the protrusion 202 into multiple protrusions all around. Crimping grooves 221c are formed on the outer circumferential surface of the tip 221 of the protrusion 202, and the spring 3 is held by the protrusions formed on the inner circumferential surface so that it is more difficult to come out.

[0053] The spring plunger 201 has a crimping groove 221c formed in the tip 221 by recessing the outer circumferential surface so that the inner circumferential surface is pushed out over the entire circumference to form a protrusion, and similarly to the spring plunger 1 of the first embodiment, the spring 3 is lightly press-fitted into the tip 221 of the protrusion 202 to adjust the overall length, and then a part of the outer circumferential surface of the first direction side X1 of the spring 3 is evenly held by the crimped protrusion, so that the protrusion 202 and the spring 3 are more firmly integrated. Therefore, the spring plunger 201 has the same effect as the spring plunger 1 of the first embodiment described above.

[0054] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment. The present invention can be embodied in various forms without departing from the spirit of the present invention, and for example, the following modifications are also possible.

[0055] (1) The materials, thicknesses, dimensional relationships, tip shapes, and the like described in the above embodiments are merely examples and may be changed without impairing the effects of the present invention.

[0056] (2) In the above embodiment, the spring 3 is described as being wound with an equal pitch, but the present invention is not limited to this. The way in which the spring is wound can be set appropriately depending on the design specifications that reflect the requirements of use and the efficiency of manufacturing, such as equal pitch, unequal pitch, a pitch that allows partial contact, the number of turns of the seat, the shape of the seat, etc.

[0057] (3) In the above-mentioned embodiments 1 and 2, the protrusions 2, 102 are described as having thin and uniform side walls, but the present invention is not limited to this. The protrusions may be formed with a thick wall or with uneven thickness as long as they have a rotationally symmetrical cylindrical shape and a front end and a rear end whose inside diameter is larger than that of the front end.

[0058] (4) In the above-described third embodiment, a plurality of crimping grooves 221c are formed. However, only one crimping groove may be formed.

[0059] (5) In the above embodiment, the light press-fitting step ST2, the full length adjustment step ST3, and the reaction force measurement step ST4 are described as being performed in separate steps, but the present invention is not limited to this. These steps can be performed simultaneously (for example, the light press-fitting step ST2 can incorporate the contents performed in the full length adjustment step ST3 or the reaction force measurement step ST4). Depending on the specifications, the order of the full length adjustment step ST3 and the reaction force measurement step ST4 can be reversed. Depending on the specifications, at least one of the full length adjustment step ST3 and the reaction force measurement step ST4 can be omitted. For example, a pressure gauge can be provided on the pressing tool used to apply a compressive force in the light press-fitting step ST2, and the spring 3 can be lightly pressed into the protruding member 2 while checking the reaction force of the spring 3, thereby incorporating the contents performed in the reaction force measurement step ST4 into the light press-fitting step ST2. Also, for example, in cases where the free length is not important during use but the spring force of the protrusion 2 is important, the overall length adjustment process ST3 may be omitted, and conversely, in cases where the free length is important during use but the spring force of the protrusion 2 is not important, the reaction force measurement process ST4 may be omitted.

[0060] (6) In the above embodiment, the projections 2, 102, 202 have different shapes, but the shape of the projection is not limited to these as long as it is rotationally symmetrical about the axis L and the spring can be lightly pressed in to hold the outer circumferential surface of the spring evenly. The projections can also be modified, for example, as follows:

[0061] FIG. 7 is an external view showing modified examples of the protrusion, with FIG. 7(a) showing a first modified example and FIG. 7(b) showing a second modified example.

[0062] The protrusion 302 in the first modified example shown in FIG. 7(a) has a bottomed cylindrical shape that is rotationally symmetrical with respect to the axis L, similar to the embodiment, and is composed of a tip portion 321 located on the first direction side X1 and a rear end portion 322 that is connected to the second direction side X2 of the tip portion 321. The tip portion 321 has a shape similar to the tip portion 21 in the first embodiment, and is composed of a hemispherical portion 321a on the first direction side X1 and a cylindrical portion 321b that extends straight from the end of the hemispherical portion 321a toward the second direction side X2 with a constant outer diameter dimension for a predetermined length. The cylindrical portion 321b of the tip portion 321 has an inner diameter dimension that allows a spring to be lightly pressed into it. The rear end portion 322 is composed of a cylindrical shape that extends straight toward the second direction side X2 with a constant outer diameter dimension. The rear end 322 has an outer dimension one size larger than that of the cylindrical portion 321b of the front end 321, and is connected to the front end 321 with a step. The inner diameter of the rear end 322 is set so as to be larger than the inner diameter of the cylindrical portion 321b of the front end 321 and the outer diameter of the spring 3.

[0063] The protrusion 402 in the second modified example shown in FIG. 7(b) has a bottomed cylindrical shape that is rotationally symmetrical with respect to the axis L, as in the embodiment, and is composed of a tip portion 421 located on the first direction side X1 and a rear end portion 422 connected to the second direction side X2 of the tip portion 421. The tip portion 421 has a shape similar to that of the tip portion 21 in the first embodiment, and is composed of a hemispherical portion 421a on the first direction side X1 and a cylindrical portion 421b that extends straight from the end of the hemispherical portion 421a toward the second direction side X2 with a constant inner diameter dimension for a predetermined length. The cylindrical portion 421b of the tip portion 421 has an inner diameter dimension that allows the spring to be lightly pressed in. The rear end portion 422 has a tapered shape that is connected to the tip portion 421 and gradually expands in diameter toward the second direction side X2. The inner diameter dimension of the rear end portion 422 is specified so that it is larger than the outer diameter dimension of the spring 3.

Claims

1. a protrusion extending along an axis extending from a first direction side to a second direction side, opening at least on the second direction side, having a cylindrical shape rotationally symmetrical with respect to the axis, the protrusion including a tip portion located on the first direction side, and a rear end portion connected to the tip portion on the second direction side and having an inner diameter larger than that of the tip portion; a spring having a compression spring structure extending coaxially with the projection, the end portion on the first direction side being fitted inside the tip portion of the projection in a lightly pressed state with the outer peripheral surface evenly held against the inner peripheral surface of the projection over one winding pitch or more so that the end portion can move continuously along the axis when an external force of a predetermined magnitude or more is applied, and the spring is integrated with the projection, the second direction side protruding from the rear end portion of the projection in an uncompressed state; A spring plunger comprising:

2. 2. The spring plunger of claim 1, The protrusion is a spring plunger having a hemispherical end face on the first direction side.

3. 2. The spring plunger of claim 1, A gap is provided between the rear end of the protrusion and the spring.

4. 2. The spring plunger of claim 1, A spring plunger in which the inner diameter dimension of the tip portion is constant or gradually increases toward the second direction.

5. 2. The spring plunger of claim 1, A spring plunger in which one or more crimping grooves are formed at the tip portion by recessing the spring and the protrusion so that the inner circumferential surface is pushed out and protruded around the entire periphery of the outer circumferential surface after the spring is integrated with the protrusion.

6. a protrusion setting process for setting a protrusion, the protrusion extending along an axis extending from a first direction side to a second direction side, having a cylindrical shape rotationally symmetrical with respect to the axis, the protrusion including a tip portion located on the first direction side and a rear end portion connected to the tip portion on the second direction side and having an inner diameter dimension larger than that of the tip portion; a light press-fitting process in which a spring having a compression spring structure is fitted into the protrusion set in the protrusion setting process in a light press-fit state in which an outer circumferential surface of an end portion on the first direction side is evenly held against an inner circumferential surface of the protrusion over a period of one winding pitch or more so that the spring can be moved continuously along the axis by an external force of a predetermined value or more; and A method for manufacturing a spring plunger comprising the steps of:

7. 7. The method of claim 6, further comprising the steps of: a total length adjustment step of releasing the compressive force applied in the light press-fitting step, protruding the second direction side of the spring from the rear end of the protrusion, and applying a compressive or tensile force to the protruding portion of the spring as necessary to keep the total length within a predetermined range.

8. 7. The method of claim 6, further comprising the steps of: The method for manufacturing a spring plunger further includes a crimping process after the light press-fitting process, in which one or more outer circumferential surfaces of the tip end of the protrusion are pressed inward over the entire circumference to push out and protrude the inner circumferential surface of the protrusion over the entire circumference.

9. The method for manufacturing a spring plunger according to any one of claims 6 to 8, In the light press-fitting step, the spring is lightly press-fitted into the plunger while checking the reaction force of the spring.