WO2022202605A1

WO2022202605A1 - Method for producing seal ring, and molding die

Info

Publication number: WO2022202605A1
Application number: PCT/JP2022/012263
Authority: WO
Inventors: 真也小田; 幸三筧
Original assignee: Ntn株式会社
Priority date: 2021-03-22
Filing date: 2022-03-17
Publication date: 2022-09-29
Also published as: JP2022146093A; JP7551546B2

Abstract

Provided are: a method for producing a seal ring that is capable of preventing the occurrence of sticking during mold opening, as well as deformation caused by such sticking, and that is capable of maintaining sealing performance; and a molding die for said method. This method for producing a seal ring has: a molding step for filling the inside of a cavity 15 formed by a fixed-side template 10, a movable-side template 11, and a core pin 12 with a molten resin to mold a seal ring; a mold-opening step for moving the movable-side template 11 and the core pin 12 in one direction with respect to the fixed-side template 10 to open the mold; and a protrusion step for moving the core pin 12 in the opposite direction from that in the mold-opening step to cause the inner-diameter-side end part of the seal ring to protrude using a step portion 13 provided on the outer peripheral surface of the core pin 12. The core pin 12 has a convex portion 14 protruding radially outward on the outer peripheral surface further toward the distal-end side than the step portion 13. In the mold-opening step, the convex portion 14 hooks into a recess on the inner peripheral surface of the seal ring, the recess being formed corresponding to the convex portion, so that the seal ring moves together with the core pin 12.

Description

SEAL RING MANUFACTURING METHOD AND FORMING MOLD

The present invention relates to a method of manufacturing a seal ring that prevents leakage of hydraulic oil filled in a device that uses fluid pressure, such as an automatic transmission of an automobile, and a molding die used in the manufacturing method.

　In devices such as automatic transmissions, oil seal rings are installed at key points to seal the hydraulic oil. For example, it is attached to a pair of spaced-apart annular grooves provided on a rotary shaft inserted through a shaft hole of a housing, and hydraulic oil supplied from an oil passage between the two annular grooves is supplied to the side and inner peripheral surfaces of both seal rings. The side wall of the annular groove and the inner peripheral surface of the housing are sealed by the opposite side surface and the outer peripheral surface. Each seal surface of the seal ring maintains the hydraulic pressure of hydraulic oil between the two seal rings while making sliding contact with the side wall of the annular groove and the inner peripheral surface of the housing. This seal ring is an annular body with a substantially rectangular cross section and has a joint at one place in the circumferential direction.

For example, Patent Document 1 describes a seal ring in which an annular projecting portion (stepped portion) having a smaller axial width than the annular portion is formed on the inner periphery of the annular portion as a seal ring. and a molding die used for the manufacturing method are disclosed. This molding die has a fixed side mold plate, a movable side mold plate, and a core pin, and molds the inner peripheral surface of the stepped portion of the seal ring and the inner diameter portion on one side surface of the stepped portion on the movable side mold plate. A core pin is provided to be slidable in the axial direction. In this manufacturing method, first, the movable side mold plate and the core pin are clamped to the fixed side mold plate, and the cavity formed between them is filled with a molten resin to mold the molded body. Then, after opening the movable side mold plate and the core pin, the core pin is slid in the axial direction to project the molded body remaining on the movable side mold plate, thereby obtaining the seal ring.

In recent years, the automotive industry has accelerated the development of fuel-efficient vehicles against the backdrop of environmental issues. As part of this, the need for low oil leakage is increasing along with the increasing demand for the idling stop function when waiting for traffic lights. For example, Patent Literature 2 describes a resin seal ring that is excellent in quality and maintains stable sealing performance over a long period of time while reducing rotational sliding friction and leakage. As a specific configuration, the side surface of the seal ring is provided with a linear contact portion that linearly contacts the side wall of the annular groove on the non-sealed fluid side, and is continuously provided over the entire circumference from one side to the other side of the joint. A line contact portion provided on one side of the joint and a line contact portion provided on the other side of the joint are provided radially apart from each other. Further, in this seal ring, the corners of the outer peripheral surface and the side surface are chamfered to form inclined surfaces.

JP-A-2004-9306 WO2004/011827

The resin seal ring as described above is obtained, for example, by injection molding of a resin composition. Here, as an example, FIG. 8 shows a process diagram of a method of manufacturing a seal ring having an inclined surface on its outer peripheral surface. FIG. 8(a) shows the molding process, and FIGS. 8(b) and 8(c) show the mold opening process. As shown in FIG. 8(a), the molding die has a stationary mold plate 51, a movable mold plate 52, and core pins 53, which abut against each other to form a cavity 54. As shown in FIG. The cavity 54 is filled with the molten resin, and after the pressure is maintained, the molded body 55 is obtained by cooling for a certain period of time. An inclined surface 55a is formed from the outer peripheral surface of the molded body 55 to the side surface.

Subsequently, in the mold opening process, the movable side mold plate 52 and the core pin 53 are moved in the X direction with respect to the fixed side mold plate 51 . At this time, although the molded body 55 would normally move in the X direction along with the movement of the core pins 53, the molded body 55 may stick to the stationary side template 51 (see FIG. 8B). ). When partial sticking occurs, the molded body 55 is released from the stationary mold plate 51, but the release is distorted (see FIG. 8(c)). Therefore, the seal ring is likely to be deformed, and for example, the flatness of the side surface is deteriorated, which may increase oil leakage. In addition, sticking may affect subsequent product take-out, etc., making continuous molding difficult. Such sticking occurs more frequently in a seal ring with an inclined surface than in a seal ring without an inclined surface because the contact area with the fixed side mold plate 51 increases due to the mold split. It's easy to do.

The present invention has been made in view of such circumstances, and provides a method for manufacturing a seal ring that can prevent the occurrence of sticking when the mold is opened and deformation due to the sticking, and can maintain the sealing performance, and a molding die for the same. intended to provide

The method for manufacturing a seal ring of the present invention is a method for manufacturing a seal ring made of synthetic resin. a molding step of filling the cavity with molten resin to mold a seal ring; a mold opening step of moving the movable side mold plate and the core pin in one direction with respect to the fixed side mold plate to open the mold; a projecting step of moving the core pin in a direction opposite to the mold opening step and projecting the inner diameter side end portion of the seal ring from a step provided on the outer peripheral surface of the core pin, wherein The inner periphery of the seal ring formed in correspondence with the protrusion in the mold opening step has a protrusion that protrudes radially outward on the outer peripheral surface on the tip side of the seal ring. It is characterized in that the seal ring is moved together with the core pin by being caught in the concave portion of the surface.

The manufacturing method includes, after the projecting step, a removing step of removing the seal ring from the core pin by engaging a jig with a side surface of the seal ring held by the core pin and moving the jig. It is characterized by

A molding die for a seal ring of the present invention is a molding die used in a method for manufacturing a seal ring of the present invention, wherein the molding die includes the stationary side template, the movable side template, and the core pin. and

The height of the protrusion of the core pin is 1% to 10% of the radial length of the seal ring.

The axial width of the protrusion of the core pin is 2% to 60% of the axial length of the seal ring.

The convex portion of the core pin is provided continuously along the circumferential direction, and the formation range of the convex portion in the circumferential direction is 15% or more of the inner circumference length of the seal ring. Characterized by

The method for manufacturing a seal ring of the present invention includes a molding step of filling a molten resin into a cavity formed by a fixed side mold plate, a movable side mold plate, and a core pin to mold the seal ring; a mold opening step of moving the movable side mold plate and the core pin in one direction to open the mold; , the outer peripheral surface of the seal ring on the tip side of the stepped portion has a convex portion that protrudes radially outward, and in the mold opening step, the convex portion is formed corresponding to the convex portion on the inner peripheral surface of the seal ring. Since the seal ring moves together with the core pin by being caught in the concave portion of the mold, it is possible to prevent the seal ring from sticking to the fixed side mold plate in the mold opening process, and also to prevent deformation due to sticking. As a result, it is possible to obtain a seal ring that maintains sealing properties.

A molding die for a seal ring of the present invention is a molding die used in the manufacturing method of the present invention, and includes the stationary side template, the movable side template, and the core pin. In the above, it is possible to prevent the seal ring from sticking to the fixed side mold plate due to being sucked, and to prevent deformation due to the sticking.

Since the height of the convex portion of the core pin is 1% to 10% of the radial length of the seal ring, it is possible to remove the seal ring from the core pin while ensuring followability of the seal ring to the core pin in the mold opening process. Excellent.

Since the width of the convex portion of the core pin is 2% to 60% of the axial length of the seal ring, the short circuit in the seal ring can be prevented by limiting the width of the corresponding concave portion while making it easier for the convex portion to be caught on the seal ring. You can suppress the occurrence of shots.

The convex portion of the core pin is provided continuously along the circumferential direction, and the formation range of the convex portion in the circumferential direction is 15% or more of the inner circumference length of the seal ring. On the other hand, almost the entire core pin can be hooked.

FIG. 2 is a plan view showing an example of a seal ring obtained by the manufacturing method of the present invention; 2 is a cross-sectional view of the seal ring of FIG. 1; FIG. FIG. 2 is an explanatory diagram of a molding die for manufacturing the seal ring of FIG. 1; 1. It is process drawing of the manufacturing method of the seal ring of FIG. It is process drawing which shows the manufacturing method of another seal ring. It is process drawing which shows the manufacturing method of another seal ring. FIG. 2 is a cross-sectional view showing a state in which the seal ring of FIG. 1 is assembled in an annular groove; It is process drawing of the manufacturing method of the conventional seal ring.

An example of the seal ring obtained by the manufacturing method of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view of the seal ring, and FIG. 2 is a sectional view taken along the line AA. As shown in FIG. 1, the seal ring 1 is an annular body formed by injection molding using a molding die and having a substantially rectangular cross section. The seal ring 1 is a cut-type ring having a joint 8 at one place in the circumferential direction, and is mounted in the annular groove after being expanded in diameter by elastic deformation.

The joint 8 is composed of a pair of ends. The shape of the pair of end portions may be straight cut, angle cut, or the like, but it is preferable to adopt the composite step cut shown in FIG. 1 because of its excellent oil sealing performance. In the compound step cut, one joint has a butting surface on the inner diameter surface side of the seal ring, and a lip protruding from the butting surface and a recessed pocket on the outer diameter surface side of the seal ring, and the other joint has the above-mentioned butting surface. It has a surface, the lip and pocket, and a complementary mating mating surface, pocket and lip.

The size of the seal ring (outer diameter φ, inner diameter φ, thickness T (radial length), width W (axial length), etc.) is appropriately set depending on the application. For example, the inner diameter φ of the seal ring is 9 mm to 75 mm, and the outer diameter φ is 13 mm to 80 mm.

In the seal ring 1, the side surface 4 or 4' serves as a sliding surface with the side wall surface of the annular groove. As shown in FIG. 2, the corners of the inner peripheral surface 2 and the side surfaces 4, 4' are provided with stepped portions 5, 5' that will protrude from the mold during injection molding. In FIG. 2, the stepped portions 5 and 5' are radially recessed portions provided at the inner diameter side end portions on both sides in the axial direction. In addition, inclined surfaces 6 and 6' are provided at both corners of the outer peripheral surface 3 and the side surfaces 4 and 4'. The inclined surfaces 6, 6' are provided over the entire circumference of the seal ring and serve as non-contact portions with the side wall surfaces of the annular groove. Incidentally, a plurality of lubricating grooves, which are concave portions, may be formed in the side surfaces 4, 4' so as to be spaced apart in the circumferential direction.

The depth of the inclined surfaces 6, 6' from the sliding surface (side surface 4 or 4') increases radially outward. In the axial cross section of the seal ring 1, the inclination angle α of the inclined surfaces 6, 6' with respect to the outer peripheral surface 3 is, for example, 20 degrees to 60 degrees. The inclination angle α is preferably 30 degrees to 50 degrees, more preferably 30 degrees to 45 degrees, and even more preferably 40 degrees to 45 degrees. If the inclination angle α is less than 20 degrees, when the seal ring has a large eccentricity (protrusion from the annular groove) during assembly to the housing, it is likely to come into contact with the end face of the housing, and galling may occur. Moreover, if the inclination angle α exceeds 60 degrees, the seal ring may not be guided smoothly when it hits the end face of the housing.

As shown in FIG. 2, the seal ring 1 has a radially recessed recess 7 on the inner peripheral surface 2 between the pair of stepped portions 5, 5'. The concave portion 7 is formed corresponding to a convex portion provided on the outer peripheral surface of the core pin, as shown in FIG. 3 which will be described later. This concave portion 7 is an undercut portion in the mold opening process. The undercut portion is a portion that engages with the convex portion of the core pin, that is, the portion that is caught on the core pin. In FIG. 2, the recess 7 is an arcuate groove having an arcuate cross-section formed continuously along the circumferential direction. This circular arc groove is not open to the stepped portions 5, 5' on both sides, but forms a recessed groove that is closed within the inner peripheral surface. In FIG. 2, the width of the inner peripheral surface 2 in the axial direction of the seal ring 1 is _wa .

FIG. 3 shows a schematic cross-sectional view of a molding die for manufacturing a seal ring. As shown in FIG. 3 , the molding die 9 has a stationary mold plate 10 , a movable mold plate 11 and core pins 12 . FIG. 3 shows them abutted to form a cavity 15. FIG. A seal ring is molded by filling the cavity 15 with a molten resin composition. Note that dimensions T, W, and _wa shown in FIG. 3 correspond to the thickness, width, and inner peripheral surface width of the seal ring, respectively.

As shown in FIG. 3, the movable side mold plate 11 forms the outer peripheral surface of the seal ring and the inclined surface and side surface on one axial side of the seal ring, and the core pin 12 forms the inner peripheral surface of the seal ring and the seal A stepped portion is formed on one axial side of the ring. In addition, the fixed-side mold plate 10 forms an inclined surface, a side surface, and a stepped portion on the other side in the axial direction of the seal ring.

The core pin 12 is a cylindrical member that can slide in the axial direction, and has a large-diameter portion 12a and a small-diameter portion 12b located on the distal end side of the large-diameter portion 12a. The part 12b is connected. The stepped portion 13 is formed perpendicular to the axial direction of the core pin 12 and the seal ring, and the stepped portion 13 forms one stepped portion of the seal ring. As will be described later, in the projecting step, the core pin 12 is moved to one side in the axial direction so that the stepped portion 13 projects the stepped portion of the seal ring.

As shown in FIG. 3, the inner peripheral surface of the seal ring is formed by the small diameter portion 12b of the core pin 12. A convex portion 14 projecting radially outward is formed on the outer peripheral surface of the small diameter portion 12b, and a concave portion 7 (see FIG. 2) is formed on the inner peripheral surface of the seal ring corresponding to the convex portion 14. . In FIG. 3, the convex portion 14 is a convex portion having an arcuate cross-section formed continuously along the circumferential direction of the core pin. The shape of the protrusion is not particularly limited, and may be, for example, a protrusion with a rectangular cross section or a protrusion with a triangular cross section. In this case, the shape of the concave portion of the seal ring also changes according to the shape of the convex portion, and for example, a square groove with a rectangular cross section or a triangular groove with a triangular cross section is formed. The dimensions of the projections and the like will be described below.

The height _ta of the projection 14 of the core pin 12 is preferably 1% to 10% of the thickness T of the seal ring. The thickness T is the maximum radial thickness of the seal ring, and is the length between the inner peripheral surface 2 and the outer peripheral surface 3 in FIG. 2, for example. The height t _a of the convex portion 14 is the length of a perpendicular drawn from the most protruding point of the convex portion to the virtual plane F of the outer peripheral surface of the small-diameter portion 12b when it is assumed that no convex portion is formed. . _If the height ta is less than 1%, the mold may not be easily caught when the mold is opened, and sticking may occur. Also, if the height _ta exceeds 10%, the core pin 12 is strongly caught, and it may become difficult to remove from the core pin 12 . The height _ta is preferably 3% to 5% of the thickness T of the sealing ring.

From another point of view, the height t _a of the projection 14 is preferably smaller than the height (radial length) of the stepped portion 13 of the core pin 12 . _A specific numerical value of the height ta of the projection 14 is about 0.05 mm to 0.2 mm. The stepped portion 13 of the core pin 12 is a portion from which the seal ring is projected in the step of pushing out. is provided.

The axial width _wb of the protrusion 14 of the core pin 12 is not particularly limited. However, if the width _wb is small, the catching is weak when the mold is opened, and sticking may occur. If the width _wb is large, short shots may occur in the seal ring, for example, when a material with high melt viscosity is used. Therefore, the width _wb of the projection 14 is preferably 2% to 60% of the width W, more preferably 5% to 40%. The width W refers to the maximum axial width of the seal ring, for example in FIG. 2 it is the length between one side 4 and the other side 4'. From another point of view, the width w _b of the projection 14 is preferably 10% to 50%, more preferably 15% to 25%, of the inner peripheral surface width w _a .

Further, it is desirable that the product of the ratio (%) of the height _ta to the thickness T and the ratio (%) of the width _wb to the width W of the convex portion 14 is in the range of 10 or more and 500 or less. If it is less than 10, it is difficult to obtain an anchoring effect when the mold is opened, and sticking may occur.

The formation range of the protrusions 14 in the circumferential direction is preferably 15% or more, more preferably 50% or more, of the inner circumference length of the seal ring. By setting the formation range of the projections 14 to 15% or more, the anchor effect can be easily obtained. On the other hand, around the joint 8 (see FIG. 1), for example, around the joint 8, the convex portion 14 of the core pin 12 is formed so as not to form a concave portion within a range of ±10° in the circumferential direction of the seal ring centered on the joint 8. is preferably formed. The upper limit of the formation range of the protrusions 14 in the circumferential direction is, for example, 90% of the inner circumference length of the seal ring, preferably 80%.

In FIG. 3, the convex portion formed continuously along the circumferential direction is shown as the convex portion, but the convex portion is composed of a plurality of (for example, two) convex portions divided in the circumferential direction. good too. In this case, the formation range of the plurality of protrusions in the ring circumferential direction (total of the protrusions) is preferably 15% or more, more preferably 50% or more, of the inner peripheral length of the seal ring. The upper limit is, for example, 90%, preferably 80%.

Further, the convex portion 14 of the core pin 12 is not limited to a convex portion continuously formed along the circumferential direction, and may be composed of a plurality of independent projections. In this case, for example, a plurality of protrusions can be arranged in a circumferential direction with a space therebetween. For the height of the projection, the width in the axial direction, and the formation range in the circumferential direction (in the case of a plurality of projections, the total thereof), the numerical ranges described above can be adopted.

The above seal ring is an injection molded body of a resin composition. As the base resin of the resin composition, any injection-moldable synthetic resin can be used. For example, thermoplastic polyimide resin, polyether ketone (PEK) resin, polyether ether ketone (PEEK) resin, polyphenylene sulfide (PPS) resin, polyamideimide (PAI) resin, polyamide (PA) resin, polybutylene terephthalate (PBT) ) resin, polyethylene terephthalate (PET) resin, polyethylene (PE) resin, polyacetal (POM) resin, phenol (PF) resin, and the like. These resins may be used alone, or may be used as a polymer alloy in which two or more kinds are mixed. Among these resins, it is preferable to use PEK resin, PEEK resin, PPS resin, or PAI resin as the base resin because it is particularly excellent in friction and wear properties, flexural modulus, heat resistance, and slidability. These resins have a high modulus of elasticity, are resistant to cracking even when the diameter is expanded when incorporated into the annular groove, can be used even when the temperature of the hydraulic oil to be sealed is high, and is free from solvent cracks.

In addition, if necessary, the base resin may be added with fibrous reinforcing materials such as carbon fiber, glass fiber and aramid fiber, spherical fillers such as spherical silica and spherical carbon, scaly reinforcing materials such as mica and talc, and potassium titanate whiskers. Microfiber reinforcing materials such as can be blended. Solid lubricants such as polytetrafluoroethylene (PTFE) resin, graphite and molybdenum disulfide, sliding reinforcing materials such as calcium phosphate and calcium sulfate, and pigments such as carbon black can also be blended. These may be blended singly or in combination.

The above raw materials are melted and kneaded to form pellets for molding, which are then molded into a predetermined shape by injection molding.

The method of manufacturing a seal ring of the present invention comprises at least a molding step of filling a cavity with molten resin to mold a seal ring, and moving a movable side mold plate and a core pin in one direction with respect to a fixed side mold plate. It comprises a mold opening step of opening the mold, and an ejecting step of moving the core pin in a direction opposite to the mold opening step to eject the seal ring. Moreover, it is preferable that this manufacturing method further includes a removing step of removing the seal ring on the core pin from the core pin using a jig after the ejecting step.

Each step will be described below with reference to FIG. FIGS. 4(a)-(d) respectively show the four steps.

<Molding process>
As shown in FIG. 4(a), the movable side mold plate 11 and the core pin 12 are clamped to the fixed side mold plate 10 to form a cavity 15 therewith. Cavity 15 is filled with a molten resin composition, and after pressure retention, it is cooled for a certain period of time to obtain molded body (seal ring) 16 . A concave portion 16 a is formed on the inner peripheral surface of the compact 16 corresponding to the convex portion 14 formed on the outer peripheral surface of the small diameter portion 12 b of the core pin 12 . In addition, the stepped portion 13 of the core pin 12 forms a stepped portion on one side in the axial direction of the compact 16 . In FIG. 4(a), the abutting surfaces of the fixed side template 10 and the movable side template 11 are arranged on the boundary line between the outer peripheral surface of the compact 16 and the inclined surface on the other side in the axial direction. The abutment surface between 10 and core pin 12 is arranged on the extension line of the step portion on the other side in the axial direction of molded body 16 .

<Mold opening process>
As shown in FIG. 4B, the movable side template 11 and the core pin 12 are moved in the X direction with respect to the fixed side template 10 to open the mold. At this time, since the concave portion 16 a is caught by the convex portion 14 of the core pin 12 , the compact 16 also moves in the X direction following the movement of the core pin 12 . In this manner, the recessed portion 16a serves as an undercut portion, and the molded body 16 is physically fixed, so sticking to the fixed side template 10 is suppressed.

<Ejection process>
As shown in FIG. 4(c), by moving the core pins 12 in the direction opposite to the mold opening process, that is, in the Y direction toward the stationary mold plate 10, the steps 13 of the core pins 12 form the compact 16. The molded body 16 is protruded by pressing the stepped portion. As a result, the molded body 16 is released from the movable side mold plate 11 .

<Extraction process>
Then, the compact 16 held by the core pin 12 is taken out in the take-out step. As shown in FIG. 4D, the molded body 16 is removed from the core pin 12 by engaging the engaging portion 17a of the take-out hand 17 with a part of the side surface 16b of the molded body 16 and moving it in the Z direction. be

The joints of the molded body obtained by the above series of steps are in a state where the pair of ends are separated from each other, but are closed by heat fixation or the like, and the seal ring 1 shown in FIG. 1 is obtained.

The manufacturing method of the present invention is not limited to the method shown in FIG. For example, as shown in FIG. 5, a wide convex portion 14 may be provided on the outer peripheral surface of the small diameter portion 12b of the core pin 12'. Also in this case, as shown in FIG. 5(b), it is possible to prevent sticking to the fixed side mold plate 10 in the mold opening process. Moreover, the height _ta of the projection 14 preferably satisfies 1% to 10% of the ring thickness T. As shown in FIG. As a result, it is possible to easily take out from the mold while maintaining the same level of sealing performance and recession of the ring as those of the conventional seal ring. If the height of the protrusion is increased, for example, as shown in FIG. 6A, the core pin 12 is more likely to be caught, and a load is applied to the periphery of the recess during the extraction process, making it easier for the seal ring to deform. .

In addition to the inner peripheral surface of the seal ring, the formation position of the concave portion that will be the undercut portion can be the side surface or the outer peripheral surface. (See FIG. 6(b)). In addition, in the case of the outer peripheral surface, the molded body is restrained by the mold when ejected, so that the molded body cannot be ejected and continuous molding is difficult. Therefore, by forming a concave portion on the inner peripheral surface, that is, by forming a convex portion on the outer peripheral surface of the core pin, as shown in FIG. .

Although FIGS. 1 to 5 show a seal ring having an inclined surface on the outer peripheral surface, the manufacturing method of the present invention is not limited to such a method of manufacturing a seal ring. That is, it can also be applied to a method of manufacturing a seal ring in which the corners of the outer peripheral surface are not chamfered.

Next, the outline of the usage pattern of the seal ring will be described with reference to FIG. The seal ring 1 is mounted in an annular groove 21 a provided in a rotating shaft 21 inserted through a shaft hole 22 a of a housing 22 . The arrow in the drawing indicates the direction in which the pressure from the hydraulic oil is applied, and the right side in the drawing is the unsealed fluid side. The side surface 4 of the seal ring 1 is in slidable contact with the side wall surface 21b of the annular groove 21a on the non-sealed fluid side. Further, the outer peripheral surface 3 is in contact with the inner peripheral surface of the shaft hole 22a. This seal structure seals the annular gap between the rotary shaft 21 and the shaft hole 22a. Moreover, the type of hydraulic oil is appropriately used according to the application. For example, the oil temperature is about −30 to 150° C., the oil pressure is about 0 to 3.0 MPa, and the rotational speed of the rotating shaft is about 0 to 7000 rpm.

As shown in FIG. 7 , in the seal ring 1 , recessed portions serving as undercut portions are not formed on the outer peripheral surface 3 or the side surface 4 related to oil leakage. A low oil leak property can be maintained. Furthermore, since the recess 7 suppresses sticking to the fixed side mold plate when the mold is opened, it is possible to suppress deformation due to sticking, such as deterioration of the flatness of the side surface 4, and as a result, it leads to maintenance of sealing performance.

According to the method for manufacturing a seal ring of the present invention, the occurrence of sticking when the mold is opened can be suppressed, and the seal performance of the seal ring can be maintained. It can be used as a method for manufacturing rings. In particular, it can be suitably used in a method of manufacturing a seal ring for improving fuel efficiency in hydraulic equipment such as AT and CVT in automobiles and the like.

REFERENCE SIGNS LIST 1 seal ring 2 inner peripheral surface 3 outer peripheral surface 4, 4' side surface 5, 5' step portion 6, 6' inclined surface 7 concave portion 8 joint 9 molding die 10 fixed side template 11 movable side template 12, 12' Core pin 13 Stepped portion 14 Protruding portion 15 Cavity 16 Molded body 17 Extraction hand (jig)
21 rotating shaft 22 housing

Claims

A method for manufacturing a seal ring made of synthetic resin,
The manufacturing method includes a molding step of clamping the movable side mold plate and the core pin to the fixed side mold plate and filling a molten resin into a cavity formed by them to mold the seal ring; a mold opening step of moving the movable side mold plate and the core pin in one direction with respect to the plate to open the mold; a projecting step of projecting the inner diameter side end of the seal ring at the stepped portion,
The core pin has a convex portion projecting radially outward from the outer peripheral surface on the tip side of the stepped portion,
A seal characterized in that, in the mold opening step, the convex portion is caught by a concave portion formed on the inner peripheral surface of the seal ring corresponding to the convex portion, so that the seal ring moves together with the core pin. How the ring is made.
The manufacturing method includes, after the ejecting step, a removing step of removing the seal ring from the core pin by engaging a jig with a side surface of the seal ring held by the core pin and moving the jig. The method of manufacturing a seal ring according to claim 1, characterized in that:
2. A seal used in the method of manufacturing a seal ring according to claim 1, wherein said molding die comprises said stationary side template, said movable side template, and said core pin. Ring mold.
The mold for molding a seal ring according to claim 3, wherein the height of the protrusion of the core pin is 1% to 10% of the radial length of the seal ring.
The mold for molding a seal ring according to claim 3, wherein the axial width of the projection of the core pin is 2% to 60% of the axial length of the seal ring.
The convex portion of the core pin is provided continuously along the circumferential direction, and the formation range of the convex portion in the circumferential direction is 15% or more of the inner circumference length of the seal ring. A molding die for a seal ring according to claim 3.