JP2006347032A - Mold and molding method for oil seal ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for an oil seal ring that has a simple design and in which the cutting plane of a gate section resin is also finished finely, and to provide a molding method of the oil seal ring. <P>SOLUTION: Movable molds 6, 7 are clamped to a fixed mold 5 having a submarine gate 12, a molten resin is injected in the cavity formed by these molds, an oil seal ring 1 in which an annular protrusion having an axial direction width smaller than a loop section is formed in the loop section inner periphery having a rectangular cross section is molded, after the molding, the fixed mold 5 cuts a resin 12' of a gate section by the mold opening operation. Since the resin of the gate section is cut by the mold opening operation, the design becomes simple and since it is cut by the mold opening operation in an early stage of the resin curing, the cutting plane becomes beautiful. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molding die for an oil seal ring that is mounted on a shaft portion of a machine part and prevents oil leakage from the shaft portion, and a method for molding the oil seal ring.

  2. Description of the Related Art An oil seal ring is known which is a mechanical part and is partially cut away to show a convex cross section as shown in FIG. The oil seal ring 1 has a ring shape in which an annular protrusion 3 having a smaller axial width than the annular portion 2 is provided on the inner periphery of the annular portion 2 having a rectangular cross-sectional shape.

  Such an oil seal ring 1 is required to have high surface accuracy with respect to the outer peripheral surface 2a and the two side surfaces 2b and 2c of the annular portion 2 serving as a seal surface. In addition, since the oil seal provided on the rotating shaft is sealed in contact with the rotating portion, the oil seal ring is required to have heat resistance and wear resistance.

  There is a technique for molding such an oil seal with a heat-resistant synthetic resin that can be injection-molded (see, for example, Patent Document 1). In the invention disclosed in this patent document, the movable side mold plate is clamped with respect to the fixed side mold plate, the molten resin is press-fitted into a cavity formed between both mold plates, and an oil seal ring is formed. After the mold opening of the movable side mold plate after molding, the stepped core pin is slid in the axial direction to protrude the oil seal ring remaining on the movable side mold plate. Then, by providing a gate on the outer peripheral surface of the portion forming the inner peripheral surface of the annular projecting portion of the core pin, it is possible to prevent a gate mark from remaining on one side surface which is a sealing surface of the annular portion.

  In the above prior art, the oil seal ring remaining on the movable side plate is projected together with the core pin by sliding the stepped core pin in the axial direction, and a stopper plate having a bifurcated portion is used to further remove the projected oil seal ring from the core pin. It is considered that the movement is performed in the axial direction after moving to a position straddling the core pin, and the gate is also cut at the same time as the movement of the stopper plate in the axial direction.

  However, the installation of the stopper plate with such a moving operation complicates the structure of the mold, and after the mold opening, that is, when the resin has hardened after a considerable amount of time has passed since the press-fitting of the resin. When the gate resin is cut, the cut surface may become rough.

JP 2004-9306 A

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a mold for forming an oil seal ring and a method for forming an oil seal ring that have a simple structure and a clean cut surface of a gate portion resin. .

In order to achieve the above object, according to a first aspect of the present invention, a movable mold is clamped with respect to a fixed mold, a molten resin is press-fitted into a cavity formed between the molds, and an annular shape having a rectangular cross section is obtained. A mold for forming an oil seal ring in which an annular projecting portion having an axial width smaller than the annular portion is formed on the inner periphery of the part, and the stationary mold has a submarine gate.
Here, the fixed mold has a sprue, the movable mold has a runner, and an extruding pin having an undercut at the tip (claim 2).
According to a third aspect of the present invention, a movable mold is clamped with respect to a fixed mold formed with a submarine gate, and a molten resin is press-fitted into a cavity formed between the molds. Forming an oil seal ring with an annular protrusion with an axial width smaller than the annular part on the inner periphery of the rectangular annular part, and then cutting the gate resin with a fixed mold by mold opening operation It was.

  In the present invention, since the gate is cut by the mold opening operation immediately after filling with the resin, the cut surface of the gate is clean, and since the gate is cut by the mold by the mold opening operation, a special member for cutting is used. There is no need for a simple mold configuration.

Embodiments of the present invention will be described below.
In FIG. 2, the mold for forming the oil seal ring according to the present invention includes one fixed mold 5, two movable molds, that is, an upper movable mold upper 6 and a lower movable mold in the figure. It consists of the following three types. The fixed mold 5 has a substantially cylindrical shape, is supported by a non-illustrated immovable member, and a sprue 8 is formed on the central axis thereof.

  The movable mold upper 6 has a substantially cylindrical shape and is inserted into the fixed mold 5. The movable mold upper 6 can be moved downward relative to the fixed mold 5 with the position shown in FIG. 2 as the home position. The upper surface of the lower movable mold 7 is in close contact with the lower surface of the upper movable mold 6 and the lower surface of the fixed mold 5, and the parting line PL 1 and the movable mold are in contact with the fixed mold 5. Parting lines PL <b> 2 are formed by the contact surfaces with the upper 6. The parting line PL1 is a central portion of the lower movable mold 7 and is a contact surface in which the lower part of the fixed mold 5 is shallowly fitted. The parting line PL2 is composed of a movable mold upper 6 and a movable mold lower 7 And is formed around the fixed mold 5.

  An annular cavity 9 is formed so as to wind the outer periphery of the lower end of the fixed mold 5. The cavity 9 is a portion where three molds of the fixed mold 5, the movable mold upper 6, and the movable mold lower 7 intersect, and is constituted by a space surrounded by these three molds. That is, the lower outer peripheral surface of the fixed mold 5 is a surface corresponding to the inner peripheral surface 3d of the annular protrusion 3 shown in FIG. The side surface 2b and the inner peripheral surface 2d of the annular portion 2 and surfaces corresponding to the side surface 3b of the annular projecting portion 3 are configured, and the lower movable mold 7 is an outer peripheral surface of the annular portion 2 shown in FIG. 2a, inner peripheral surfaces 2c and 2e, and a surface corresponding to the side surface 3c of the annular protrusion 3 are formed.

  The sprue 8 reaches the inside of the movable mold 7 below the parting line PL1, and is sealed with an extrusion pin 10 mounted on the extension. A Z-shaped undercut is formed at the top end of the push pin 10 to prevent the resin filled in the sprue 8 and the like from being held on the movable mold 7 side when the mold is opened.

  In FIG. 3, which is a plan view of the movable mold 7, for convenience of explanation, the cavity 9 is shown filled with the oil seal ring 1. As shown in the figure, in this example, the oil seal ring 1 is not a complete ring, but has a shape in which a part of the ring is open, and the open ends are stepped so that they can mesh with each other. It is formed and used in a state in which these stepped portions are engaged with each other.

  2 and 3, the sprue 8 is located at the center of the cavity 9, and a runner 11 branched in a V shape from the sprue 8 is formed in a U-shaped groove shape on the upper surface of the lower movable mold 7. . In FIG. 4, in which the vicinity of the tip end portion of the runner 11 is enlarged, the tip end portion of the runner 11 communicates with a submarine gate 12 having a V-shaped cross section formed in the vicinity of the outer periphery of the fixed mold 5. Is open to the cavity 1. Thus, it is the feature in this embodiment of the present invention that the fixed mold 5 has the submarine gate 12.

  A hole communicating with the runner 11 is formed in the lower movable mold 7, and this hole is sealed with an extrusion pin 14. A Z-shaped undercut is formed at the top end of the push pin 14 to prevent it from coming off. Further, a plurality of push pins 15 are dispersedly arranged with the tip portion located at a portion of the cavity 9 corresponding to the side surface 3c of the annular protrusion 3 shown in FIG.

Hereinafter, the oil seal ring forming process will be described in order.
(A) 1st process (mold closing, resin filling completion)
As shown in FIGS. 2 and 4, the lower movable mold 7 abuts against the fixed mold 5 at the parting line PL 1, and the upper movable mold 6 at the parting line PL 2 against the movable mold lower 7. The sprue 8, the runner 11, the submarine gate 12, and the cavity 9 are formed under the closed mold state where the runner 11 and the runner 11 contact the submarine gate 12 through the sprue 8. After that, resin is press-fitted into the cavity 9 to form the oil seal ring 1. In the figure, the filled resin portions are shown as dots.

(B) Second step (first stage of mold opening)
As shown in FIG. 5, with the cylindrical outer diameter portion of the fixed mold 5 as a guide, the movable mold upper 6 is integrated with the movable mold lower 7 with respect to the fixed mold 5 with the arrow 16. The mold opens away from the parting line PL1 as a boundary by moving in the direction indicated by. When the mold is opened, the undercut portion of the push pin 10 holds the resin 8 ′ filled in the spool 8 on the lower side of the movable mold 7 so that the upper end of the resin 8 ′ has a base end portion with the smallest diameter. Cut at 8a.

  Since the undercut portion of the push pin 14 holds the resin 11 ′ filled in the runner 11 on the movable mold 7 side, the portion of the resin 12 ′ (resin filled in the submarine gate 12) on the extension of the resin 11 ′ However, as a result of staying on the lower side of the movable mold 7, the tip end portion of the resin 12 ′ having a V-shaped cross section and gradually decreasing in diameter is cut by the fixed mold 5 at the inner peripheral surface 3 d of the oil seal ring 1. Separated from the oil seal ring 1. The portion of the resin 12 ′ separated from the oil seal ring 1 passes through the submarine gate 12 according to the mold opening operation, and maintains an integral state with the resin 11 ′.

  Here, the cut by the cutting at the inner peripheral surface 3d of the oil seal ring 1 and the tip of the resin 12 ′ is performed at the initial stage of resin curing, ie, mold opening operation after resin filling. It becomes a clean cut along the peripheral surface 3d. A portion below the fixed die 5 and above the surface corresponding to the inner peripheral surface 3d is a tapered portion 17 in order to improve the efficiency of the mold opening operation.

(C) Third step (second stage of mold opening)
As shown in FIG. 6, when the movable mold upper 6 integrated with the movable mold 7 moves in the direction indicated by the arrow 18, the mold is opened apart from the parting line PL2. By this mold opening, the oil seal ring 1 in the lower movable mold 7 is in a state where there are no obstacles when it is taken out upward. Similarly, the resin 11 ′ separated from the oil seal ring 1 and the resin 8 ′ integrated with the resin 11 ′ are in a state where there are no obstacles when taken upward.

(D) Fourth step (product removal)
As shown in FIG. 7, by pushing a plurality of push pins 15, the oil seal ring 1 is pushed out from the lower movable mold 7 by the push pins 15. Further, by extruding the extrusion pin 14, the resin 8 ′ and the resin 11 ′ integrated with the resin 8 ′ are extruded from the lower movable mold 7 and fall off from the extrusion pin 14.

It is a partial appearance perspective view of an oil seal ring. It is sectional drawing of a metal mold | die. It is a top view on a moving metal mold | die. It is a fragmentary sectional view of a metal mold | die. It is a fragmentary sectional view of a metal mold | die. It is a fragmentary sectional view of a metal mold | die. It is a fragmentary sectional view of a metal mold | die.

Explanation of symbols

5 Fixed mold 6 Movable mold upper 7 Movable mold lower 12 Submarine gate

Claims (3)

The movable mold is clamped with respect to the fixed mold, and the molten resin is press-fitted into a cavity formed between the molds. A mold for molding an oil seal ring in which a protrusion is formed,
A mold for molding an oil seal ring, wherein the fixed mold has a submarine gate. The mold for molding an oil seal ring according to claim 1,
A mold for forming an oil seal ring, characterized in that the fixed mold has a sprue, the movable mold has a runner, and an extrusion pin with an undercut at the tip. The movable mold is clamped with respect to the fixed mold formed with the submarine gate, the molten resin is press-fitted into the cavity formed between the molds, and the annular section is formed on the inner periphery of the annular section having a rectangular cross section. An oil seal ring formed with an annular projecting portion having a smaller axial width is formed, and after the molding, the gate resin is cut by the fixed mold by a mold opening operation. Method.

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