JP6804002B1 - Manufacturing method of resin molded member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesion between a bottom surface of an annular groove and a sealing material in a resin molding member provided with an annular groove which becomes an undercut portion at the time of molding and a method for manufacturing the same. SOLUTION: A piston rod 3 has a small diameter portion 31 forming a bottom surface 5a of an annular groove 5 in which a sealing material 4 is arranged, and a first large diameter portion 32 and a first large diameter portion 32 arranged on both sides of the small diameter portion 31 in the axial direction. It includes two large diameter portions 33. At the time of manufacturing the piston rod 3, in the primary molding step, after molding the first portion 30A having no parting line on the outer peripheral surface using a single first mold member 101 having a tubular inner peripheral surface, the secondary portion 30A is formed. In the molding step, the second portion 30B is molded in a part of the first portion 30A in the axial direction by using the second mold member 102 that can be divided in the circumferential direction. As a result, the piston rod 3 provided with the annular groove 5 having the outer peripheral surface of the first portion 30A having no parting line as the bottom surface 5a can be formed. [Selection diagram] Fig. 3

Description

The present invention relates to a method for producing a resin molded member having an annular groove in which the seal member is arranged.

A wide structure is used to prevent leakage of liquid or gas by inserting a shaft member such as a piston rod into a cylinder filled with a liquid or gas such as oil or water and using a sealing material such as an O-ring fitted on the outer peripheral surface of the shaft member. It has been adopted. In this type of sealed structure, a shaft member provided with an annular groove for arranging the sealing material on the outer peripheral surface is used. Further, also in a joint portion such as a pipe, a joint member provided with an annular groove for arranging a sealing material on the outer peripheral surface is used in order to maintain the airtightness.

When a shaft member or a joint member having an annular groove formed on the outer peripheral surface is manufactured from resin, the annular groove becomes an undercut portion, so that the slide slides in a direction intersecting the movable mold opening direction with respect to the fixed mold. Use the core. Therefore, parting lines, which are traces of the dividing lines of the slide core, are formed at at least two places on the bottom surface of the annular groove formed in the resin molding member.

In the above-mentioned sealing structure, the sealing material is brought into close contact with the bottom surface of the annular groove to ensure the sealing property. However, if a parting line is formed on the bottom surface of the annular groove, the adhesion of the sealing material is lowered and the airtightness is lowered. In order to ensure airtightness, cutting and polishing must be performed to remove the parting line after molding. In this case, processing marks such as cutting marks and polishing marks remain on the bottom surface of the annular groove.

Patent Document 1 discloses a resin molded member having no trace of a mold dividing line on the sealing surface and a method for manufacturing the same. The resin molded member of Patent Document 1 is provided with a flexible lip adjacent to the annular seat portion which is a sealing surface, and the sealing material is held by the lip. Since the lip is flexible, it can be released by force. Therefore, since the annular seat portion can be formed without using the slide core, the parting line is not formed on the annular seat portion (seal surface).

JP-A-2009-502565

The manufacturing method of Patent Document 1 is limited to a shape that can be forcibly removed. For example, since it is difficult to bend a solid resin molded member toward the inner peripheral side, it is difficult to manufacture the solid resin molded member by the manufacturing method of Patent Document 1. Further, if the force is pulled out, a large force is applied to the portion bent toward the inner peripheral side, which may cause deformation or decrease in strength. In addition, the shape accuracy of the portion bent toward the inner peripheral side may decrease. If the shape accuracy of the annular groove is lowered, there is a problem that the adhesion with the sealing material cannot be ensured.

An object of the present invention is to improve the adhesion between the bottom surface of the annular groove and the sealing material in a resin molded member having an annular groove that becomes an undercut portion during molding. In particular, is to provide a production method of the release time of the risk is small in lowering of strength reduction and shape accuracy due to the force is applied, it does not require machining of the surface after molding the resin molded member.

In order to solve the above problems, in the method for manufacturing a resin molded member of the present invention, a first cavity is formed by using a single first mold member having a tubular inner peripheral surface extending in the axial direction. A primary molding step of forming a first portion extending in the axial direction, a first molding step of separating the first mold member from the first portion in the axial direction, and the first molding step. A second molding step of forming a second cavity using a second mold member surrounding the outer peripheral side of the portion and molding a second portion connected to a part of the outer peripheral surface of the first portion in the axial direction. Further, it is characterized in that a secondary molding step of performing a second mold release step of dividing the second mold member in the circumferential direction and releasing the mold from the second portion in the radial direction is performed.

According to the present invention, a single first mold member is used to form a first portion having an outer peripheral surface without a parting line, and then a second mold member that can be divided in the circumferential direction is used. A second portion connected to a part of the outer peripheral surface in the axial direction of one portion is formed. Therefore, since the second portion having a diameter larger than that of the first portion can be formed in a part of the first portion in the axial direction, an annular groove to be an undercut portion can be formed. Further, when molding the first portion, since the first mold member having the tubular inner peripheral surface is released without being divided in the circumferential direction, a parting line is not formed on the outer peripheral surface of the first portion. , The parting line is not formed on the bottom surface of the annular portion. Therefore, the adhesion between the sealing material arranged in the annular groove and the bottom surface of the annular groove can be improved. Further, since the second mold member is not forcibly removed when the mold is released, there is little possibility that the strength or the shape accuracy is lowered due to the force applied at the time of the mold release. Further, since the parting line is not removed after molding, the manufacturing process of the resin molded member can be simplified.

In the present invention, in the primary molding step, the first portion is molded by the first resin, and in the secondary molding step, the second portion is molded by a second resin different from the first resin. In this way, the type of resin can be properly used as needed. For example, it is possible to manufacture a resin molded member having a small diameter portion composed of the first portion and a large diameter portion composed of the second portion having different strengths.

In the present invention, the first resin and the second resin are preferably compatible resins. The compatible resin is a resin in which the first resin and the second resin are melted together at the interface between the first resin and the second resin to form a uniform composition. By using a compatible resin, the integrity of the first portion and the second portion can be enhanced, so that the small diameter portion composed of the first portion and the large diameter portion composed of the second portion are integrated. Can be enhanced. Therefore, the strength of the resin molded member can be increased.

In the present invention, in the primary molding step, a flow path forming member is arranged in the first cavity to form a flow path inside the first portion, and in the secondary molding step, the flow path is passed through the flow path. The second cavity is filled with resin. In this way, even if the resin cannot be filled directly into the second cavity from the gate, the resin can be filled into the second cavity from the flow path formed inside the first portion. That is, even if the gate for filling the resin cannot be arranged in the second mold member in the secondary molding step, the resin can be filled in the second cavity. Further, since the resin filled in the flow path is cured to form an anchor portion, the integrity of the first portion and the second portion can be enhanced, and the small diameter portion composed of the first portion and the second portion. It is possible to enhance the integrity of the large diameter portion composed of. Therefore, the strength of the resin molded member can be increased.

In the present invention, in the primary molding step, it is preferable that the distance between the surface of the flow path forming member and the inner surface of the first cavity is 0.5 mm or more. In this way, the wall thickness of the resin surrounding the flow path becomes 0.5 mm or more, so that the first part is deformed by the resin pressure during filling and the party by the mold (second mold member) in the secondary molding step. It can suppress parting line transcription. Since the bottom surface of the annular groove is formed by the first portion, it is possible to suppress a decrease in the dimensional accuracy of the annular groove.

In the present invention, in the primary molding step, the first cavity is formed between the first mold member and the third mold member, and in the secondary molding step, the second mold member and the third mold member are formed. The second cavity is formed between the two cavities, and the deviation of the central axis of the second cavity with respect to the central axis of the first portion held by the third mold member is within 0.1 mm. It is preferable to position the third type member and the second type member. By doing so, the axial deviation (center deviation) between the first portion and the second portion can be reduced, so that the small diameter portion forming the bottom surface of the annular groove and the large diameter portion adjacent to the small diameter portion in the axial direction can be reduced. The axis deviation (center deviation) with and can be reduced. Therefore, since it is possible to suppress a decrease in the shape accuracy of the annular groove, it is possible to suppress a decrease in the sealing property when the sealing material is arranged in the annular groove.

In the present invention, the first portion includes a small diameter portion adjacent to the second portion in the axial direction, and the tubular inner peripheral surface includes a first tubular inner peripheral surface portion for molding the small diameter portion. It is preferable that the second type member includes an annular contact surface that contacts the outer peripheral surface of the small diameter portion, and the inner diameter of the annular contact surface is smaller than the inner diameter of the first tubular inner peripheral surface portion. .. In the present invention, the dimensions of the second mold member used in the secondary molding step are set on the premise that the dimensions of the molded product change due to the shrinkage of the resin. That is, the inner diameter of the surface (annular contact surface) of the second mold member to be applied to the outer peripheral surface (outer peripheral surface of the small diameter portion) of the primary molded product is the molding surface (first) of the first mold member for molding the primary molded product. Set smaller than the inner diameter of the tubular inner peripheral surface). As a result, the second mold member can be brought into close contact with the surface of the molded product, so that the possibility of resin leaking from the second cavity to the outside can be reduced. Therefore, the second portion can be appropriately molded.

In the method for manufacturing a resin molded member of the present invention, a parting line is not formed on the bottom surface of the annular groove that is the undercut portion of the resin molded member, so that the adhesion to the sealing material can be improved. Further, since the mold is not forcibly removed at the time of mold release, there is little possibility that the strength and the shape accuracy are lowered due to the force applied at the time of mold release. Further, since the parting line is not removed after molding, the manufacturing process of the resin molded member can be simplified.

It is explanatory drawing which shows the structure of the air damper provided with the resin molding member manufactured by the manufacturing method to which this invention is applied. It is a side view and a cross-sectional view of the piston rod which concerns on 1st Embodiment, and is a sectional view of the primary molded product. It is a figure explaining the manufacturing process of the piston rod which concerns on 1st Embodiment. It is a side view and a sectional view of the piston rod which concerns on 2nd Embodiment, and is a sectional view of the primary molded product. It is a figure explaining the manufacturing process of the piston rod which concerns on 2nd Embodiment.

The resin molding member manufactured by the manufacturing method to which the present invention is applied is a molded product manufactured by injection molding using a mold. The resin molded member is provided with an annular groove on the outer peripheral surface on which a sealing material is arranged, and is used for dampers, joints, connectors, etc. that ensure airtightness by the sealing material. In the embodiment described below, the piston rod used for the air damper will be described as an example of the resin molded member. The present invention is not limited to the embodiments described below.

(Air damper)
1 (a) and 1 (b) are explanatory views showing the configuration of an air damper 1 provided with a resin molded member manufactured by a manufacturing method to which the present invention is applied. As shown in FIGS. 1A and 1B, the air damper 1 includes a cylindrical cylinder case 2, a piston rod 3 that can move in the axial direction inside the cylinder case 2, and a sealing material 4. .. The piston rod 3 is a resin molded member. In the present specification, L is the central axis of the piston rod 3, L1 is one side of the direction along the central axis L (hereinafter referred to as the axis direction), and L2 is the other side of the axis direction. In addition, in FIGS. 1A and 1B, the cross-sectional structure of the cylinder case 2 and the sealing material 4 is displayed, and the side view of the piston rod 3 is displayed.

As shown in FIG. 1A, the tip of the piston rod 3 is inserted into the cylinder case 2. The sealing material 4 is mounted in an annular groove 5 provided at the tip of the piston rod 3 to seal the gap between the inner peripheral surface of the cylinder case 2 and the piston rod 3. In this embodiment, the sealing material 4 is an O-ring.

FIG. 1B is an explanatory view showing the configuration of an air damper having a double seal structure. In the example shown in FIG. 1 (b), the sealing material 4 is mounted on the annular groove 5 provided at the tip of the piston rod 3, and the annular groove 6 is provided at a position separated from the annular groove 5 in the axial direction. The sealing material 4a is attached to the. The sealing materials 4 and 4a seal the gap between the inner peripheral surface of the cylinder case 2 and the piston rod 3.

(First Embodiment)
(Structure of piston rod)
Hereinafter, with reference to the drawings, the configuration of the piston rod 3 that can be used for the air damper 1 of FIGS. 1 (a) and 1 (b) and the embodiment of the manufacturing method thereof will be described. FIG. 2A is a side view of the piston rod 3 according to the first embodiment. FIG. 2B is a cross-sectional view of the piston rod 3 according to the first embodiment. FIG. 2C is a cross-sectional view of the primary molded product.

As shown in FIG. 2A, an annular groove 5 extending in the circumferential direction is provided at the tip of L1 on one side in the axial direction of the piston rod 3. The piston rod 3 has a small diameter portion 31 forming the bottom surface 5a of the annular groove 5, a first large diameter portion 32 adjacent to the small diameter portion 31 on one side L1 in the axial direction, and a small diameter portion 31 on the other side in the axial direction. A second large diameter portion 33 adjacent to each other is provided. The annular groove 5 of the piston rod 3 is composed of a first large diameter portion 32, a small diameter portion 31, and a second large diameter portion 33.

The first large-diameter portion 32 is located at the tip of L1 on one side in the axial direction of the piston rod 3, and the second large-diameter portion 33 is located at the center of the piston rod 3 in the axial direction. The axial length of the first large diameter portion 32 is larger than the axial width of the annular groove 5. The axial length of the second large diameter portion 33 is larger than the axial width of the annular groove 5. The lengths of the first large diameter portion 32 and the second large diameter portion 33 in the axial direction are not limited to such dimensions, and can be changed as appropriate. For example, the width of the first large diameter portion 32 and the second large diameter portion 33 in the axial direction may be equal to or less than the width of the annular groove 5 in the axial direction. Further, the piston rod 3 includes a base portion 34 provided at the end of L2 on the other side in the axial direction of the second large diameter portion 33, and a neck portion 35 connecting the second large diameter portion 33 and the base portion 34. The base 34 is provided with a through hole 34a orthogonal to the axial direction. The through hole 34a is used for passing a connecting pin or the like for attaching the air damper 1 to the mating component.

As shown in FIG. 2A, an annular groove 6 extending in the circumferential direction is provided in the portion of the piston rod 3 on the other side L2 in the axial direction. The bottom surface 6a of the annular groove 6 is formed by the outer peripheral surface of the neck portion 35. The annular groove 6 is composed of a second large diameter portion 33, a neck portion 35, and a base portion 34.

The piston rod 3 is a solid member. The first large diameter portion 32, the small diameter portion 31, the second large diameter portion 33, and the neck portion 35 have a circular cross-sectional shape orthogonal to the axial direction and are arranged coaxially. In this embodiment, the first large diameter portion 32 and the second large diameter portion 33 have the same diameter. The neck portion 35 has a smaller diameter than the first large diameter portion 32 and the second large diameter portion 33, and has a larger diameter than the small diameter portion 31. The outer diameters of the first large diameter portion 32, the second large diameter portion 33, the small diameter portion 31, and the neck portion 35 are not limited to dimensions that satisfy the above-mentioned magnitude relationship.

In the piston rod 3, the bottom surface 5a of the annular groove 5 formed by the outer peripheral surface of the small diameter portion 31 and the bottom surface 6a of the annular groove 6 formed by the outer peripheral surface of the neck portion 35 are smooth surfaces, and the bottom surfaces 5a and 6a have a smooth surface. Does not have a parting line, which is a split mark of the mold during molding. Further, the bottom surfaces 5a and 6a have no processing marks such as polishing marks and cutting marks. Therefore, when the sealing material 4 is arranged in the annular groove 5, the sealing material 4 comes into close contact with the bottom surface 5a. Further, when the sealing material 4a is arranged in the annular groove 6, the sealing material 4a adheres to the bottom surface 6a.

The piston rod 3 is a member molded by a resin double mold. The piston rod 3 forms a first portion 30A, which is a primary molded product shown in FIG. 2C, in the primary molding step, and then in the secondary molding step, a part of the outer peripheral surface of the first portion 30A in the axial direction. Manufactured by forming a second portion 30B in. The second portion 30B is connected to the outer peripheral surface of the first portion 30A and projects radially outward from the outer peripheral surface of the first portion 30A.

As shown in FIG. 2C, the first portion 30A, which is a primary molded product, includes a small diameter portion 31, a base portion 34, and a neck portion 35. Further, the first portion 30A is a portion of the second large diameter portion central portion 331 which is the central portion of the second large diameter portion 33 and the portion L2 on the other side in the axial direction of the central portion of the first large diameter portion 32. 1 A large diameter portion center portion 321 is provided. The first portion 30A continuously extends from the base portion 34 to the central portion 321 of the first large diameter portion.

As shown in FIG. 2B, the second portion 30B is a second large diameter portion outer peripheral portion 332 which is an outer peripheral portion of the second large diameter portion 33, and a first outer peripheral portion of the first large diameter portion 32. A large-diameter portion outer peripheral portion 322 and a first large-diameter portion tip portion 323 which is an end portion of one side L1 in the axial direction of the central portion of the first large-diameter portion 32 are provided. In this way, the second portion 30B is formed at two locations separated in the axial direction. The outer peripheral surfaces of the first large diameter portion 32 and the second large diameter portion 33 are composed of the second portion 30B.

As will be described later, the first portion 30A, which is a primary molded product, is molded using the first mold member 101, which is a single mold member. The first type member 101 is provided with a tubular inner peripheral surface which is a molding surface, and the outer peripheral surfaces of the small diameter portion 31 and the neck portion 35 are molded by the tubular inner peripheral surface. Therefore, no parting line is formed on the outer peripheral surfaces of the small diameter portion 31 and the neck portion 35.

On the other hand, the second portion 30B formed by the secondary molding is formed by using a second mold member which is a split mold that can be divided in the circumferential direction. Therefore, as shown in FIG. 2A, a parting line PL is formed on the outer peripheral surfaces of the first large diameter portion 32 and the second large diameter portion 33.

In this embodiment, the resin used for molding the first portion 30A is the same as the resin used for molding the second portion 30B. The first portion 30A and the second portion 30B may be molded with different resins. That is, the first resin for molding the first portion 30A and the second resin for molding the second portion 30B may be different resins. In this case, if a resin having high compatibility is selected as the first resin and the second resin, the bonding strength between the first portion 30A and the second portion 30B can be improved. As a result, the integrity of the first portion 30A and the second portion 30B can be enhanced, so that the strength of the piston rod 3 can be improved.

(Manufacturing method of piston rod)
Next, a method of manufacturing the piston rod 3 will be described with reference to FIG. FIG. 3 is a diagram illustrating a manufacturing process of the piston rod 3 according to the first embodiment. In FIG. 3, ST1 is the first molding step and ST2 is the first mold release step. In the primary molding step, the first molding step ST1 and the first mold release step ST2 are performed. Further, ST3 is a second molding step, and ST4 is a second mold release step. In the secondary molding step, the second molding step S
T3 and the second release step ST4 are performed.

First, in the primary molding step, in the first molding step ST1, the first cavity C1 which is the first resin filling space for molding the first portion 30A is formed. Specifically, the first mold member 101 provided in the movable mold and the third mold member 103 provided in the fixed mold are brought into contact with each other. As a result, the first cavity C1 is formed between the first mold member 101 and the third mold member 103.

The first mold member 101 is a single mold having a tubular inner peripheral surface extending in the axial direction. The tubular inner peripheral surface includes a first tubular inner peripheral surface portion 101a and a second tubular inner peripheral surface portion 101b. The first tubular inner peripheral surface portion 101a is a cylindrical surface, and has an inverted shape of the first large diameter portion central portion 321 and the small diameter portion 31 and the second large diameter portion central portion 331. The second tubular inner peripheral surface portion 101b has an inverted shape of the neck portion 35, and is a cylindrical surface having a diameter larger than that of the first tubular inner peripheral surface portion 101a. The third type member 103 includes a recess 103a which is an inverted shape of the base 34. A slide pin 103b for forming a through hole 34a is arranged in the recess 103a.

The first type member 101 is provided with a gate 201 for filling the first cavity C1 with resin. In the first molding step ST1, the first cavity C1 is filled with resin from the gate 201. By curing the filled resin, the first portion 30A, which is a primary molded product, is molded.

Subsequently, in the first mold release step ST2, the first mold member 101 is moved in the axial direction of the first tubular inner peripheral surface portion 101a (that is, the axial direction of the first portion 30A) and separated from the first portion 30A. Mold. As described above, the first mold member 101 is a single mold, and the first tubular inner peripheral surface portion 101a and the second tubular inner peripheral surface portion 101b are not divided in the circumferential direction. Therefore, no parting line is formed on the outer peripheral surfaces of the first large diameter portion central portion 321 and the small diameter portion 31, the second large diameter portion central portion 331, and the neck portion 35.

Next, in the secondary molding step, in the second molding step ST3, the second cavity C2, which is the second resin filling space for molding the second portion 30B, is formed. Specifically, the third mold member 103 provided on the fixed mold and the second mold member 102 provided on the slide core are brought into contact with each other. Further, the second type member 102 and the fourth type member 104 provided in the movable type are brought into contact with each other. As a result, the second cavity C2 is formed on the outer peripheral side of a part of the first portion 30A in the axial direction.

In the second molding step ST3, the first portion 30A is not released from the third mold member 103. The first portion 30A held by the third mold member 103 is arranged inside the second mold member 102 to form the second cavity C2. The second cavity C2 is formed at two locations separated in the axial direction. That is, the second cavity C2 includes a second cavity C2a that surrounds the outer peripheral side of the tip end portion of the first portion 30A, and a second cavity C2b that surrounds the outer peripheral side of the central portion in the axial direction of the first portion 30A. In step ST3, the deviation amount of the central axis of the second cavity C2 with respect to the central axis L of the first portion 30A held by the third type member 103 is 0.1 mm or less with respect to the third type member 103. The second mold member 102 is positioned.

The second type member 102 includes a penetrating portion penetrating the center in the radial direction, and the first portion 30A is arranged in the penetrating portion. The second type member 102 includes a large diameter penetrating portion 102a provided at the central portion of the second type member 102 in the axial direction, and a large diameter member 102 provided at an end portion of L1 on one side in the axial direction of the second type member 102. A diameter recess 102b is provided. The large diameter penetrating portion 102a forms the second cavity C2a. Further, a second cavity C2b is formed between the large diameter recess 102b and the fourth type member 104.

The second type member 102 has a first annular contact surface 102c that abuts on the outer peripheral surface of the first portion 30A on one side L1 in the axial direction of the second cavity C2a, and the other side L2 in the axial direction of the second cavity C2a. A second annular contact surface 102d that abuts on the outer peripheral surface of the first portion 30A is provided. In this embodiment, the first annular contact surface 102c and the second annular contact surface 102d are brought into contact with the outer peripheral surface of the first portion 30A to seal the second cavity C2a and prevent the resin from leaking. For example, the first annular contact surface 102c and the second annular contact surface 102d are configured to compress the first portion 30A inward in the radial direction by about 0 to 0.1 mm, respectively, so that the first annular contact surface 102c And the second annular contact surface 102d is brought into close contact with the outer peripheral surface of the first portion 30A.

In the present embodiment, the inner diameter of the first annular contact surface 102c is set to be smaller than the inner diameter of the first tubular inner peripheral surface portion 101a provided on the first type member 101. Further, the inner diameter of the second annular contact surface 102d is set to be smaller than the inner diameter of the second tubular inner peripheral surface portion 101b. As a result, the inner diameter of the first annular contact surface 102c becomes smaller than the outer diameter of the small diameter portion 31 with which the first annular contact surface 102c abuts. Further, the inner diameter of the second annular contact surface 102d is smaller than the outer diameter of the neck portion 35 with which the second annular contact surface 102d abuts. In this embodiment, the inner diameters of the first annular contact surface 102c and the second annular contact surface 102d are set in consideration of the amount of shrinkage when the resin is cured in the primary molding step. Therefore, the first annular contact surface 102c and the second annular contact surface 102d can be brought into close contact with the outer peripheral surface of the first portion 30A.

In the second molding step ST3, the second cavity C2a is filled with resin from the gate 202 formed in the second mold member 102. Further, the second cavity C2b is filled with resin from the gate 203 formed in the fourth type member 104. By curing the filled resin, the second portion 30B is formed on the outer peripheral surface of the first portion 30A. More specifically, the tip end portion 323 of the first large diameter portion and the outer peripheral portion 322 of the first large diameter portion are formed, and the outer peripheral portion 332 of the second large diameter portion is formed. As a result, the first large diameter portion 32 and the second large diameter portion 33 are formed, and the piston rod 3 provided with the annular groove 5 is formed.

Subsequently, in the second mold release step ST4, the third mold member 103 and the fourth mold member 104 are moved in the axial direction with respect to the piston rod 3 which is a molded product to release the mold. Further, by moving the slide core provided with the second mold member 102 along an angular pin (not shown), the second mold member 102 is divided in the circumferential direction and released to the outer peripheral side. A parting line PL is formed on the second portion 30B formed by the second mold member 102, which is a split mold. Therefore, a parting line PL is formed on the first large diameter portion 32 and the second large diameter portion 33.

(Main effects of the first embodiment)
As described above, in the first embodiment, in the primary molding step, the first portion 30A having no parting line on the outer peripheral surface was molded by using a single first mold member 101 having a tubular inner peripheral surface. Later, in the secondary molding step, the second portion 30B connected to a part of the outer peripheral surface of the first portion 30A in the axial direction is formed by using the second mold member 102 that can be divided in the circumferential direction. As a result, the first large diameter portion 32 can be formed on one side L1 in the axial direction of the small diameter portion 31 formed by the first portion 30A, and the second large diameter portion 33 can be formed on the other side L2 in the axial direction of the small diameter portion 31. Can be formed. Therefore, the annular groove 5 serving as the undercut portion can be formed. Further, when molding the first portion 30A, since the first mold member 101 is released without being divided in the circumferential direction, a parting line is not formed on the outer peripheral surface of the first portion 30A, and the annular groove 5 is formed. No parting line is formed on the bottom surface 5a. Therefore, the adhesion between the sealing material 4 arranged in the annular groove 5 and the bottom surface 5a of the annular groove 5 can be improved. Further, since the second mold member 102 is not forcibly removed when the mold is released, there is little possibility that the strength or the shape accuracy is lowered due to the force applied at the time of the mold release. Further, since the parting line is not removed after molding, the manufacturing process of the piston rod 3 can be simplified.

Further, in the first embodiment, the second large diameter portion 33 is formed on one side L1 of the neck portion 35 in the axial direction. Therefore, the annular groove 6 serving as the undercut portion can be formed. A parting line is not formed on the bottom surface 6a of the annular groove 6 as in the bottom surface 5a of the annular groove 5. Therefore, the adhesion between the sealing material 4a arranged in the annular groove 6 and the bottom surface 6a of the annular groove 6 can be improved.

In the first embodiment, the resin for molding the first portion 30A and the resin for molding the second portion 30B are the same resin, but as described above, the type of resin can be used properly. For example, if the first portion 30A and the second portion 30B are molded from resins having different strengths, it is possible to manufacture a piston rod 3 having different strengths for the small diameter portion 31, the first large diameter portion 32, and the second large diameter portion 33. When different resins are used, the strength of the piston rod 3 can be increased because the integrity of the first portion 30A and the second portion 30B can be enhanced by selecting a compatible resin.

In the first embodiment, in the secondary molding step, the deviation of the central axes of the second cavities C2a and C2b with respect to the central axis of the first portion 30A held by the third mold member 103 is within 0.1 mm. , The third mold member 103 and the second mold member 102 are positioned. As a result, the axial deviation (center deviation) between the small diameter portion 31, the first large diameter portion 32, and the second large diameter portion 33 can be reduced. Therefore, the shape accuracy of the annular groove 5 can be improved, and deterioration of the sealing property when the sealing material 4 is arranged in the annular groove 5 can be suppressed.

In the first embodiment, the dimensions of the second mold member 102 used in the secondary molding step are set on the premise that the dimensions of the molded product change due to the shrinkage of the resin. Specifically, the first portion 30A, which is a primary molded product, is provided with a small diameter portion 31 and a neck portion 35 adjacent to the second portion 30B in the axial direction, and the tubular inner peripheral surface for forming the first portion 30A is A first tubular inner peripheral surface portion 101a for molding the small diameter portion 31 and a second tubular inner peripheral surface portion 101b for forming the neck portion 35 are provided. Since the second mold member 102 includes a first annular contact surface 102c that contacts the outer peripheral surface of the small diameter portion 31 in the secondary molding step, the inner diameter of the first annular contact surface 102c is set within the first tubular shape. The size should be smaller than the inner diameter of the peripheral surface portion 101a. Further, since the second mold member 102 includes a second annular contact surface 102d that abuts on the outer peripheral surface of the neck portion 35 in the secondary molding step, the inner diameter of the second annular contact surface 102d has a second tubular shape. The size should be smaller than the inner diameter of the inner peripheral surface portion 101b. For example, the first annular contact surface 102c and the second annular contact surface 102d are applied to the outer peripheral surface of the first portion 30A, which is a primary molded product, so that the amount of contact is about 0 to 0.1 mm. The inner diameters of the contact surface 102c and the second annular contact surface 102d are set. As a result, in the secondary molding step, the second mold member 102 can be brought into close contact with the outer peripheral surface of the primary molded product, so that there is little risk of resin leaking from the second cavities C2a and C2b. Therefore, the second portion 30B can be appropriately molded.

The piston rod 3 of the first embodiment is manufactured by the above manufacturing method, and has no parting line on the bottom surface 5a of the annular groove 5 and the bottom surface 6a of the annular groove 6 which are undercut portions during molding. Further, there are no machining marks (cutting marks or polishing marks) from which the parting line is removed on the bottom surface 5a of the annular groove 5 and the bottom surface 6a of the annular groove 6. Therefore, when the sealing materials 4 and 4a are arranged in the annular groove 5 and the annular groove 6, the adhesion between the bottom surface 5a of the annular groove 5 and the sealing material 4 and the adhesion between the bottom surface 6a of the annular groove 6 and the sealing material 4a High adhesion. Therefore, the sealing effect of the sealing materials 4 and 4a can be enhanced. For example, when the piston rod 3 is used as a component constituting a sealed structure such as a joint, an air damper, or an oil damper, the airtightness can be improved.

The piston rod 3 of the first embodiment is a solid member. Therefore, since the shape is difficult to pull out by force, a parting line is formed on the bottom surface 5a of the annular groove 5 and the bottom surface 6a of the annular groove 6 in the conventional manufacturing method. In the manufacturing method of the first embodiment, it is possible to prevent a parting line from being formed on the bottom surface 5a of the annular groove 5 and the bottom surface 6a of the annular groove 6 which are undercut portions during molding even if the shape is difficult to pull out. is there.

(Second Embodiment)
(Structure of piston rod)
Next, the piston rod 3C and the manufacturing method thereof according to the second embodiment will be described with reference to FIG. FIG. 4A is a side view of the piston rod 3C according to the second embodiment. FIG. 4B is a cross-sectional view of the piston rod 3C according to the second embodiment. FIG. 4C is a cross-sectional view of the primary molded product. Hereinafter, the configurations common to those of the first embodiment are designated by the same reference numerals, description thereof will be omitted, and different configurations will be described.

The piston rod 3C of the second embodiment is molded by a resin double mold as in the first embodiment. The piston rod 3C includes a first portion 30C formed in the primary forming step and a second portion 30D formed on a part of the outer peripheral surface of the first portion 30C in the secondary forming step in the axial direction. As shown in FIG. 4C, the second embodiment is different from the first embodiment in that the first portion 30C, which is a primary molded product, has a flow path 36 inside. Further, as shown in FIG. 4B, the second embodiment is different from the first embodiment in that the anchor portion 37 is formed inside the piston rod 3C.

As shown in FIG. 4C, the flow path 36 formed in the first portion 30C includes a first flow path 361 extending in the axial direction and a second flow path 362 extending in the radial direction. The first flow path 361 is arranged at the center of the first portion 30C in the radial direction, and opens at the end surface of one side L1 of the first portion 30C in the axial direction. Therefore, one end of the first flow path 361 is opened at the position of the gate filled with the resin in the primary molding step. The other end of the first flow path 361 is connected to the second flow path 362.

One end and the other end of the second flow path 362 open to the outer peripheral surface of the first portion 30C. Similar to the first embodiment, the first portion 30C of the second embodiment has the first large diameter portion center portion 321C and the second large diameter portion center in which the second portion 30D is formed on the outer peripheral surface by the secondary molding step. A unit 331 is provided. The second flow path 362 is formed inside the second large-diameter portion central portion 331, and opens on the outer peripheral surface of the second large-diameter portion central portion 331. Therefore, as will be described later, when the second cavity C2a is formed in the secondary molding step, one end and the other end of the second flow path 362 are opened to the inner surface of the second cavity C2a, respectively. Therefore, it is possible to fill the second cavity C2a with the resin via the first flow path 361 and the second flow path 362.

The flow path 36 is not limited to the shape of this embodiment, and may have a shape in which one end opens at the gate position and the other end opens on the outer peripheral surface of the second large diameter portion central portion 331. ..

As shown in FIG. 4B, the anchor portion 37 is formed by curing the resin filled in the flow path 36, and has a second large diameter made of the same resin as the outer peripheral portion 332 of the second large diameter portion. It is integrally molded with the outer peripheral portion 332. Further, in the present embodiment, the anchor portion 37 uses the same resin as the first large diameter portion tip portion 323 and the first large diameter portion outer peripheral portion 322 to form the first large diameter portion tip portion 323 and the first large diameter portion outer peripheral portion 322. It is molded integrally with.

The piston rod 3C of the second embodiment has a length in the axial direction of the central portion 321C of the first large diameter portion provided at the tip portion different from that of the first embodiment, and has a first large diameter of the second embodiment. The central portion 321C is longer than the central portion 321 of the first large diameter portion of the first embodiment. Therefore, the first portion 30C formed by the primary molding step is longer in the axial direction than the first portion 30A of the first embodiment.

(Manufacturing method of piston rod)
Next, a method of manufacturing the piston rod 3C of the second embodiment will be described with reference to FIG. FIG. 5 is a diagram illustrating a manufacturing process of the piston rod 3C according to the second embodiment. In the second embodiment, the primary molding step and the secondary molding step are performed as in the first embodiment. In the primary molding step, the first molding step ST1 and the first mold release step ST2 are performed. Further, in the secondary molding step, the second molding step ST3 and the second mold release step ST4 are performed.

In the primary molding step, in the first molding step ST1, the first cavity C1 which is the first resin filling space for molding the first portion 30C is formed. The second embodiment is different from the first embodiment in that the first slide pin 105 and the second slide pin 106, which are flow path forming members, are arranged in the first cavity C1. Inside the first cavity C1, the first slide pin 105 extends in the axial direction and the second slide pin 106 extends in the direction orthogonal to the axial direction. The first slide pin 105 and the second slide pin 106 are in contact with each other at the radial center of the first cavity C1.

In the second embodiment, in the first molding step ST1, the first cavity C1 in which the first slide pin 105 and the second slide pin 106 are arranged is filled with resin from the gate 201. Subsequently, in the first mold release step ST2, the first slide pin 105 and the second slide pin 106 are removed from the first mold member 101 before the first mold member 101 is released from the mold. After that, as in the first embodiment, the first mold member 101 is moved in the axial direction with respect to the first portion 30C to release the mold. As a result, the first portion 30C provided with the first flow path 361 and the second flow path 362 is formed. The first portion 30C is a molded product having no parting line on the outer peripheral surface.

In the second embodiment, the position of the first slide pin 105 and the position of the first slide pin 105 so that the distance from the outer peripheral surface of the first slide pin 105 to the tubular inner peripheral surface forming the inner surface of the first cavity C1 is 0.5 mm or more. The dimensions and the shape of the first type member 101 are set. As a result, the first portion 30C is formed into a shape in which the wall thickness of the resin surrounding the outer peripheral side of the first flow path 361 is 0.5 mm or more.

Next, in the secondary molding step, in the second molding step ST3, the second cavity C2, which is the second resin filling space for molding the second portion 30B, is formed. More specifically, the second cavity C2a is formed in the central portion in the axial direction of the second type member 102, and the second cavity C2b is formed between the second type member 102 and the fourth type member 104.

In the second molding step ST3, the gate 204 formed in the fourth mold member 104 is connected to the flow path 36, and the second cavity C2a is filled with resin from the gate 204 via the flow path 36. 1 Different from the embodiment. Further, as in the first embodiment, the second cavity C2b is filled with resin from the gate 203 formed in the fourth mold member 104. By curing the filled resin, the second portion 30D is formed on the surface of the first portion 30C. More specifically, the tip end portion 323 of the first large diameter portion and the outer peripheral portion 322 of the first large diameter portion are formed, and the outer peripheral portion 332 of the second large diameter portion is formed.

Subsequently, in the second mold release step ST4, similarly to the first embodiment, the third mold member 103 and the fourth mold member 104 are moved in the axial direction with respect to the piston rod 3 which is a molded product to release the mold. Further, the second mold member 102 is divided in the circumferential direction and released to the outer peripheral side.

(Main effects of the second embodiment)
The piston rod 3C of the second embodiment and the method for manufacturing the piston rod 3C can obtain the same effects as those of the first embodiment described above. That is, the piston rod 3C provided with the annular groove 5 and the annular groove 6 as the undercut portion can be formed, and the parting line is not formed on the bottom surface 5a of the annular groove 5 and the bottom surface 6a of the annular groove 6. Therefore, the adhesion between the sealing material 4 arranged in the annular groove 5 and the bottom surface 5a of the annular groove 5 can be improved. Further, when the sealing material 4a is also arranged in the annular groove 6 to form a double seal structure, the adhesion between the bottom surface 6a of the annular groove 6 and the sealing material 4a can be improved. Further, since the piston rod 3C is not forcibly pulled out when it is molded, there is little possibility that the strength or the shape accuracy is lowered due to the force applied at the time of mold release. Further, since the parting line is not removed after molding, the manufacturing process of the piston rod 3C can be simplified.

Further, as in the first embodiment, the deviation of the central axes of the second cavities C2a and C2b with respect to the central axis of the first portion 30C held by the third mold member 103 is within 0.1 mm. Since the 3rd type member 103 and the 2nd type member 102 are positioned, there is little axial deviation (center deviation) between the small diameter portion 31, the 1st large diameter portion 32, and the 2nd large diameter portion 33. Therefore, deterioration of the sealing property when the sealing material 4 is arranged in the annular groove 5 and the annular groove 6 can be suppressed. Further, in the secondary molding step, since the second mold member 102 can be brought into close contact with the outer peripheral surface of the primary molded product, there is little possibility that the resin leaks from the second cavities C2a and C2b to the outside. Therefore, the second portion 30D can be appropriately molded.

In the second embodiment, the flow path forming members (first slide pin 105 and second slide pin 106) are arranged in the first cavity C1 in the primary molding step to form the flow path 36 inside the first portion 30A. In the secondary molding step, the second cavities C2a and C2b are filled with resin via the flow path 36. Therefore, even if the gate for filling the resin in the secondary molding step cannot be arranged in the second mold member 102 and the resin cannot be directly filled in the second cavity C2a from the gate, the second cavity C2a is filled with the resin. be able to.

In the second embodiment, the resin filled in the flow path 36 is cured to form an anchor portion 37 integrated with the second portion 30D. Specifically, the anchor portion 37 extends inside the first large diameter portion central portion 321C, the second large diameter portion central portion 331, and the small diameter portion 31, and the second large diameter portion outer peripheral portion 332, the first. It is integrally molded with the large diameter portion tip portion 323 and the first large diameter portion outer peripheral portion 322. Therefore, the integrity of the first portion 30C and the second portion 30D can be enhanced, and the strength of the piston rod 3C can be enhanced. As in the first embodiment, the first portion 30C molded in the primary molding step and the second portion 30D molded in the secondary molding step may be molded with the same resin, or different resins. It may be molded with.

In the second embodiment, the distance from the surface of the first slide pin 105 to the inner peripheral surface of the first cavity C1 is set to 0.5 mm or more. As a result, the wall thickness of the resin surrounding the flow path 36 can be made 0.5 mm or more, so that in the secondary molding step, the first portion 30C is deformed by the resin pressure when the second cavity C2a is filled with the resin. Can be suppressed, and the parting line transfer by the second mold member 102 in the secondary molding step can be suppressed. By suppressing the deformation of the first portion 30C, it is possible to suppress a decrease in the dimensional accuracy of the small diameter portion 31 constituting the bottom surface 5a of the annular groove 5, so that when the sealing material 4 is arranged in the annular groove 5, the airtightness is deteriorated. Can be suppressed. Further, by suppressing the parting line transfer, it is possible to suppress a decrease in the adhesion of the sealing material 4.

(Other prevailing forms)
The structure of the mold used in the method for manufacturing the resin molded member of the present invention is not limited to the configurations described in the first embodiment and the second embodiment. The mold configuration is such that the first mold member 101, which is a single mold having a tubular inner peripheral surface, and the second mold member 102, which is a split mold, are included. Good.

In the first embodiment and the second embodiment, the resin molding member is a piston rod, but the resin molding member is not limited to the piston rod. For example, the resin molded member may be a hollow pipe used for a joint or the like.

The structure of the resin molded member manufactured by the manufacturing method to which the present invention is applied is not limited to the structure of the piston rod described in the first embodiment and the second embodiment. For example, the position, number, width, and depth of the annular groove can be freely set. According to the present invention, after molding a primary molded product, an annular groove is formed by forming a large-diameter portion in a part of the primary molded product in the axial direction, so that the position, number, width, and depth of the annular groove are formed. Can be freely designed. For example, in the first embodiment and the second embodiment, the annular groove 5 and the annular groove 6 have different radial depths, and the annular groove 6 is shallower than the annular groove 5, but the annular groove 5 The shape of the piston rod 3 may be set so that the depth of the piston rod 6 and the depth of the annular groove 6 are the same.

1 ... Air damper, 2 ... Cylinder case, 3, 3C ... Piston rod, 4, 4a ... Sealing material, 5 ... Circular groove, 5a ... Bottom surface, 6 ... Circular groove, 6a ... Bottom surface, 30A, 30C ... First part, 30B , 30D ... 2nd part, 31 ... small diameter part, 32 ... 1st large diameter part, 33 ... 2nd large diameter part, 34 ... base, 34a ... through hole, 35 ... neck, 36 ... flow path, 37 ... anchor part , 101 ... 1st type member, 101a ... 1st tubular inner peripheral surface portion, 101b ... 2nd tubular inner peripheral surface portion, 102 ... 2nd type member, 102a ... Large diameter penetrating portion, 102b ... Large diameter concave portion, 102c ... 1st annular contact surface, 102d ... 2nd annular contact surface, 103 ... 3rd mold member, 104 ... 4th mold member, 103a ... recess, 103b ... slide pin, 105 ... 1st slide pin, 106 ... 2nd slide pin, 201, 202, 203, 204 ... Gate, 321 and 321C ... Central part of 1st large diameter part, 322 ... Outer part of 1st large diameter part 2 Central part of large diameter part 332 ... Second large diameter part outer peripheral part, 361 ... First flow path, 362 ... Second flow path, C1 ... First cavity, C2, C2a, C2b ... Second cavity, L ... Center Axial line, L1 ... one side in the axial direction, L2 ... the other side in the axial direction, PL ... parting line

Claims (7)

A first molding step in which a first cavity is formed using a single first mold member having a tubular inner peripheral surface extending in the axial direction to form a first portion extending in the axial direction, and the first molding step. A primary molding step of performing a first mold release step of releasing the first mold member from a portion in the axial direction, and
A second cavity is formed by using a second mold member surrounding the outer peripheral side of the first portion, and a second portion connected to a part of the outer peripheral surface of the first portion in the axial direction is formed. Resin molding characterized by performing a molding step and a secondary molding step of performing a second molding step of dividing the second mold member in the circumferential direction and releasing the mold from the second portion in the radial direction. Manufacturing method of parts. In the primary molding step, the first portion is molded with the first resin.
The method for manufacturing a resin molding member according to claim 1, wherein in the secondary molding step, the second portion is molded by a second resin different from the first resin. The method for manufacturing a resin molding member according to claim 2, wherein the first resin and the second resin are compatible resins. In the primary molding step, a flow path forming member is arranged in the first cavity to form a flow path inside the first portion.
The method for manufacturing a resin molding member according to any one of claims 1 to 3, wherein in the secondary molding step, the second cavity is filled with a resin via the flow path. The method for manufacturing a resin molding member according to claim 4, wherein in the primary molding step, the distance between the surface of the flow path forming member and the inner surface of the first cavity is 0.5 mm or more. In the primary molding step, the first cavity is formed between the first mold member and the third mold member.
In the secondary molding step, the second cavity is formed between the second mold member and the third mold member.
The third type member and the second type member are placed so that the deviation of the central axis of the second cavity with respect to the central axis of the first part held by the third type member is within 0.1 mm. The method for manufacturing a resin molded member according to any one of claims 1 to 5, wherein the resin molded member is positioned. The first portion includes a small diameter portion adjacent to the second portion in the axial direction.
The tubular inner peripheral surface includes a first tubular inner peripheral surface portion for forming the small diameter portion.
The second type member includes an annular contact surface that contacts the outer peripheral surface of the small diameter portion.
The method for manufacturing a resin molded member according to any one of claims 1 to 6, wherein the inner diameter of the annular contact surface is smaller than the inner diameter of the first tubular inner peripheral surface portion.

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