JP2005321101A - Plastic seal for bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic seal for a bearing which enables an improvement in joint strength of a welding part, and a reduction in manufacturing costs. <P>SOLUTION: The ring-shaped plastic seal 20 for the bearing is molded by injecting molten resin with reinforced fiber 12 into a ring-shaped cavity 19 from a gate 10 for injecting the resin installed on the peripheral end part of the ring-shaped cavity 19 formed within a molding die 21. Then the center of the welding part P2 is formed by the confluence of each of the heads, which are reverse to each other, of the molten resin which is injected within the ring-shaped cavity 19 after injection molding, and is divided into two flows. Then the center of the welding part P2 is projected circumferentially in the ring-shaped cavity 19 in a nonflat convex shape. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plastic seal for a rolling bearing, and more particularly to a plastic seal for a bearing with improved weld strength.

  As shown in FIG. 6, the ball bearing 2 which is a kind of rolling bearing has a plurality of balls (rolling elements) 5 disposed between the outer ring 3 and the inner ring 4, and the interval between the balls 5 is as follows. The cage 6 is held between the inner and outer rings. Further, on one or both surfaces of the ball bearing 2, a bearing plastic seal 1 is mounted to prevent foreign matter from entering between the inner and outer rings 3 and 4 and leakage of a lubricant such as filled grease. ing.

  The bearing plastic seal 1 is a ring-shaped member, and there are an inner ring fixing type in which its inner peripheral edge is fitted and fixed to the inner ring of the bearing, and an outer ring fixing type in which its outer peripheral edge is fitted and fixed to the outer ring of the bearing. Generally, an outer ring fixed type such as the plastic seal 1 for bearings shown in FIG. 6 is often used. The bearing plastic seal 1 is slidably contacted with the fitting groove 1a fitted in the fitting groove 7 provided in the outer ring 3 and the sealing groove 8 provided in the inner ring 4, or a slight gap is provided. A lip portion 1b that forms a labyrinth with the seal groove 8 and a connecting portion 1c that connects the fitting portion 1a and the lip portion 1b are integrally formed by injection molding with a resin material as appropriate. .

  On the side surface of the outer ring 3 to which the bearing plastic seal 1 is mounted, a minimum diameter portion 7 a having an inner diameter smaller than that of the fitting groove 7 is formed. The mounting fitting portion 1a of the bearing plastic seal 1 is set to have an outer diameter larger than the minimum diameter portion 7a. When the bearing plastic seal 1 is mounted on the outer ring 3 of the ball bearing 2, the bearing plastic is used. The seal 1 is elastically deformed inward to pass through the minimum diameter portion 7 a and is inserted into the fitting groove 7. And the plastic seal 1 for bearings is attached to the outer ring | wheel 3 by distorting the attachment fitting part 1a between the fitting groove outer side surface 7b and the fitting groove inner side surface 7c, and carrying out close fitting in the fitting groove 7. FIG. The fitting is fixed.

  On the other hand, when a resin ring such as a plastic seal 1 for bearings is injection-molded, a ring-shaped cavity 9 is formed in a molding die 11 as shown in FIG. In general, an injection molding method of molding a resin ring having a predetermined shape by injecting a resin material as appropriate from a resin injection gate 10 provided in the section. However, the molten resin injected into the ring-shaped cavity 9 from the resin injection gate 10 becomes two flows in the cavity 9, and then the weld P1 (resin injection gate) where the flowing molten resin ends merge again. The weld line L is formed on the side substantially opposite to the line 10.

  Although it differs depending on the resin material, it is generally well known that the joint strength of the weld part in such injection molding is lowered. Therefore, as a method of making the weld line L inconspicuous, there is a method of degassing or providing a resin reservoir in the weld portion, a response by molding conditions such as raising the temperature of the molten resin or raising the mold temperature, and vacuum drawing molding. Methods such as local heating of the weld section have been performed.

  By the way, when the plastic seal 1 for a bearing as described above is used for, for example, a plastic seal of a rolling bearing for high-speed rotation that requires high durability and high molding accuracy, a reinforced fiber such as glass fiber is used as a resin material. The strength is improved by using a fiber reinforced resin to which is added or using a liquid crystal polymer as a resin material.

  However, as shown in FIG. 8, in the case of the fiber reinforced resin to which the reinforcing fiber 12 such as glass fiber is added, the added reinforcing fiber 12 and the molecular chain are in the flow perpendicular direction (along the weld line L) in the weld part P1. Direction), the entanglement becomes difficult to occur, and the bonding strength of the weld portion P1 of the plastic seal 1 for bearings is lowered.

  In addition, the liquid crystal polymer has a low joint strength even in the case of a non-reinforced resin that does not include the reinforcing fibers 12, and further decreases in the case of a fiber reinforced resin that includes the reinforcing fibers 12. For this reason, in the case of the plastic seal 1 for bearings which uses a liquid crystal polymer as a resin material, there existed a problem that it would crack from the weld part P1 by the elastic deformation at the time of bearing assembly.

  Further, in order to avoid the problem of a decrease in bonding strength at the weld part P1, a resin ring injection molding method has been developed in which the resin injection gate is changed to a disk gate so that the weld line itself does not occur. However, in the injection molding method using a disk gate, since the gate mark cannot be reduced, there is a problem that the post-processing amount of the molded product is greatly increased and the production cost is increased. Further, it is difficult to increase the accuracy of the coaxiality of the inner and outer diameters of the molded product, and it is not suitable as an injection molding method for a plastic seal for bearings.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a plastic seal for bearings that can improve the weld strength of the weld and reduce the production cost. There is to do.

The above object of the present invention can be achieved by the following constitution.
(1) Ring-shaped bearing plastic molded by injecting molten resin added with reinforcing fibers into a ring-shaped cavity from a resin injection gate provided at the periphery of the ring-shaped cavity formed in a molding die The center of the weld, which is a seal and is formed by joining the tips of the molten resin injected into the ring-shaped cavity after injection molding to face each other, is the ring-shaped cavity. A plastic seal for bearings, which protrudes in a non-flat convex shape in the circumferential direction.
(2) The bearing plastic seal is provided with a resin reservoir into which a part of the molten resin can flow in at the peripheral edge of the ring-shaped cavity separated from the weld, and the resin reservoir is positioned on the peripheral edge from the resin injection gate. Is set to a range that does not exceed 5/6 of the peripheral distance between the resin injection gate and the weld portion, and the opening cross-sectional area of the communication portion that connects the resin reservoir and the ring-shaped cavity is defined as the ring-shaped cavity. The molten resin injected into the ring-shaped cavity is set to a size that limits the amount of molten resin flowing from the ring-shaped cavity to the resin reservoir so that the resin reservoir is filled, The plastic seal for bearings according to (1), which is formed by injecting molten resin from a resin injection gate into a ring-shaped cavity.
(3) The plastic seal for bearings according to (1) or (2), wherein the molten resin is a fiber reinforced resin or a liquid crystal polymer to which reinforcing fibers are added.

  According to the plastic seal for bearings of the present invention, the center of the weld portion formed by joining the respective tip portions of the molten resin which are injected into the ring-shaped cavity after injection molding into two flows and facing each other. However, since it protrudes in a non-flat convex shape in the circumferential direction of the ring-shaped cavity, the contact area of the molten resin in the weld portion can be increased, and the molecular chain can be oriented in the flow direction of the molten resin. The bonding strength of the weld portion can be improved.

  Also, according to the above configuration, after being injected into the ring-shaped cavity to form two flows, the leading ends of the flowing molten resin reach the weld portion where they merge again, and the ring-shaped cavity is filled with the molten resin After that, the molten resin in the ring-shaped cavity near the resin reservoir flows into the resin reservoir by the injection pressure, and the molten resin is filled in the resin reservoir.

  Therefore, the pressure balance at each tip portion of the molten resin that confronts and merges at the weld portion collapses, and resin flow occurs in the resin reservoir side along the circumferential direction, so that the opposite surface of each molten resin protrudes toward the resin reservoir side. It becomes a non-flat shape. Accordingly, the contact area of the molten resin to be joined increases in the weld portion, and the molecular chain is also oriented in the flow direction of the molten resin, so that the bonding strength of the resin in the weld portion is increased.

  Preferably, the opening cross-sectional area of the communication portion is made smaller than the opening cross-sectional area of the ring-shaped cavity. In this case, the molten resin can be filled in the resin reservoir after being filled in the ring-shaped cavity in a state where the capacity of the resin reservoir is set to the minimum necessary size.

  Preferably, a resin reservoir is provided between the resin injection gate and the weld at the peripheral edge of the ring-shaped cavity and within a range of 5/6 from the resin injection gate. By setting the installation position of the resin reservoir within the above-described range, a sufficient resin flow can be generated at the weld portion, and higher bonding strength can be obtained.

  Preferably, a resin reservoir is formed between the protruding pins in the molding die. In this case, the capacity of the resin reservoir can be easily changed by changing the length of the protruding pin.

  Further, according to the above configuration, the gate trace does not become large as in the conventional injection molding method using a disk gate, and the resin injection gate and the communication portion of the molded product taken out from the molding die are cut. Therefore, the post-processing amount of the molded product can be greatly reduced. Thereby, production cost can be reduced.

  Furthermore, according to the above configuration, since the molten resin is a fiber reinforced resin or liquid crystal polymer to which reinforcing fibers are added, the weld strength of the weld portion can be further improved, and the strength of the plastic seal for bearings can be greatly increased. It can be improved, and high durability and high molding accuracy can be achieved.

Hereinafter, in order to describe an embodiment of a plastic seal for bearings according to the present invention, an injection molding method of the plastic seal for bearings will be described in detail with reference to the drawings.
FIG. 1 is a partial horizontal sectional view of a molding die for explaining an injection molding method of a plastic seal for bearings according to the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIG. FIG. 4 is a schematic explanatory view showing the state of the molten resin at the weld in the ring cavity of the molding die, and FIG. 4 is a partial horizontal sectional view for explaining a modification of the molding die.

  As shown in FIGS. 1 and 2, the injection molding method for a plastic seal for bearings according to the present invention includes a ring-shaped cavity from a resin injection gate 10 provided at a peripheral portion of a ring-shaped cavity 19 formed in a molding die 21. The plastic seal 20 for bearings of a predetermined shape is manufactured by injecting molten resin into the inside 19.

  Then, on the peripheral edge of the ring-shaped cavity 19, the ring-shaped cavity 19 is located between the weld portion P <b> 2 that has advanced from the gate position of the resin injection gate 10 by about a half turn in the circumferential direction of the ring-shaped cavity 19 and the resin injection gate 10. A resin reservoir 23 into which a part of the molten resin injected into the resin can flow is provided. In the case of this injection molding method, the position where the resin reservoir 23 is formed is a position moved about 45 ° along the circumferential direction from the position where the resin injection gate 10 is formed, as shown in FIG.

  The resin reservoir 23 communicates with the ring-shaped cavity 19 via a communication portion 27 having an opening cross-sectional area smaller than the opening cross-sectional area of the ring-shaped cavity 19. When molten resin is injected from the resin injection gate 10 into the ring-shaped cavity 19, the amount of the molten resin flowing into the resin reservoir 23 from the ring-shaped cavity 19 is limited by the communication portion 27.

  That is, after being injected into the ring-shaped cavity 19 to form two flows, the respective tip portions of the flowing molten resin reach the weld portion P2 where they merge again, and the ring-shaped cavity 19 is filled with the molten resin. At the time, as shown in FIG. 2, the opening cross-sectional area of the communication portion 27 and the capacity of the resin reservoir 23 are set so that a void 23 a remains in the resin reservoir 23. In the case of this injection molding method, the resin reservoir 23 is formed between the protruding pin 25 in the molding die 21 as shown in FIG. 2, and the capacity of the resin reservoir 23 is adjusted by the mold. Even if it does not perform, it can adjust easily by the change of the length of the protrusion pin 25. FIG.

  Then, the molten resin is partially flown in the ring-shaped cavity 19 in the vicinity of the resin reservoir 23 after the respective tip portions of the molten resin that have reached two flows reach the weld portion P2 and are filled in the ring-shaped cavity 19. The molten resin flows into the resin reservoir 23 by the injection pressure, and is filled in the resin reservoir 23.

  That is, the pressure balance at each tip of the molten resin that confronts and merges at the weld P2 is broken, and resin flow occurs on the resin reservoir 23 side in the circumferential direction, so that each tip of the molten resin after injection molding is As shown in FIGS. 1 and 3, the center of the facing surface Z of each molten resin, which is a weld portion P <b> 2 formed by joining together, is a convex shape that is not flat in the circumferential direction of the ring-shaped cavity 19. Protruding. Therefore, in the weld part P2, the contact area of the molten resin to be joined increases and the molecular chain is oriented in the flow direction of the molten resin, so that the bonding strength of the resin in the weld part P2 is increased.

  Further, as the resin material of the plastic seal 20 for bearings of the present embodiment, as shown in FIG. 3, fiber reinforced resin or liquid crystal polymer added with reinforcing fibers 12 such as glass fibers (glass fibers) is used. In the part P2, since the opposing surface Z has a convex shape on one side, the added reinforcing fiber 12 is also oriented in the flow direction of the molten resin, and entanglement occurs.

  Therefore, the plastic seal 20 for bearings molded by the injection molding method described above is a facing surface Z of each molten resin that is a weld portion P2 formed by joining and joining the respective leading ends of the molten resin after injection molding. The center of the ring-shaped cavity 19 protrudes in a non-flat convex shape in the circumferential direction. As a result, a fiber reinforced resin or liquid crystal polymer obtained by adding reinforced fibers 12 to the resin material is used, and the bonding strength of the weld portion P2 is improved despite injection molding using the molding die 21 as described above. can do. The injection molding method described above is basically a molding method in which a molten resin is injected from a single resin injection gate 10 provided on the periphery of the ring-shaped cavity 19.

  Further, unlike the conventional injection molding method using a disk gate, the gate trace does not increase, and the molded product taken out from the molding die 21 only cuts the resin injection gate 10 and the communication portion 27. Therefore, the post-processing amount of the molded product can be greatly reduced, and the production cost can be reduced. Further, it is possible to easily increase the accuracy of the coaxiality of the inner and outer diameters of the molded product.

  Therefore, according to the plastic seal 20 for bearings of this embodiment, it forms when each front-end | tip part of the molten resin which injected into the ring-shaped cavity 19 after injection molding and became two flows merges oppositely. Since the center of the weld part P2 protrudes in a non-flat convex shape in the circumferential direction of the ring-shaped cavity 19, the contact area of the molten resin in the weld part P2 can be increased, and the molecular chain can be Since it can be oriented in the direction, the bonding strength of the weld portion P2 can be improved.

  Further, according to the bearing plastic seal 20 of the present embodiment, the bearing plastic seal 20 has the resin reservoir 23 into which a part of the molten resin can flow into the peripheral edge portion of the ring-shaped cavity 19 that is removed from the weld portion P2. Provided, the installation position of the resin reservoir 23 is set in a range in which the distance on the peripheral edge from the resin injection gate 10 does not exceed 5/6 of the peripheral distance between the resin injection gate 10 and the weld portion P2, and the resin After the molten resin injected into the ring-shaped cavity 19 is filled in the ring-shaped cavity 19, the resin cross-sectional area 23 is filled with the opening cross-sectional area of the communication portion 27 that communicates the reservoir 23 with the ring-shaped cavity 19. In such a manner, the size is set so as to limit the amount of molten resin flowing from the ring-shaped cavity 19 into the resin reservoir 23, and the molten resin is injected into the resin injection gate 1. Since the resin is molded by being injected into the ring-shaped cavity 19, the gate trace does not increase as in the conventional injection molding method using a disk gate, and the resin of the bearing plastic seal 20 taken out from the molding die is used. Since it is only necessary to cut the injection gate 10 and the communication part 27, the post-processing amount of the molded product can be greatly reduced. Thereby, production cost can be reduced.

  Moreover, according to the plastic seal 20 for bearings of this embodiment, since molten resin is the fiber reinforced resin or liquid crystal polymer which added the reinforced fiber, while being able to further improve the joint strength of the weld part P2, a bearing The strength of the plastic seal 20 can be greatly improved, and high durability and high molding accuracy can be achieved.

  Further, according to the injection molding method, the resin reservoir 23 communicates with the ring-shaped cavity 19 via the communication portion 27 having an opening cross-sectional area smaller than the opening cross-sectional area of the ring-shaped cavity 19. It can be configured such that the molten resin is filled into the ring-shaped cavity 19 and then filled into the resin reservoir 23 in a state where the capacity of the reservoir 23 is set to the minimum necessary size. Thereby, the inflow amount of the molten resin flowing into the resin reservoir 23 can be reduced, the waste of the resin material can be minimized, and an increase in the size of the molding die 21 can be suppressed.

  As a modification of the molding die used in the injection molding method, a molding die 31 may be used instead of the molding die 21. As shown in FIG. 4, the molding die 31 changes the position where the resin reservoir 23 is formed to a position moved about 150 ° along the circumferential direction from the position where the resin injection gate 10 is formed, and also changes the cross-sectional shape. Is the same configuration as the molding die 21 described above.

  And when the plastic seal 20 for bearings was manufactured using this shaping die 31, the fiber reinforced resin or reinforcement fiber 12 which added the reinforcement fiber 12 to the resin material was used like the case where the said shaping die 21 was used. Even when the added liquid crystal polymer was used, the plastic seal 20 for bearings having high durability and high molding accuracy could be obtained without being cracked from the weld due to elastic deformation during the bearing assembly.

  However, when the bearing plastic seal 20 is molded using a molding die in which the resin reservoir 23 is formed closer to the weld part P2, the bonding strength at the weld part P2 cannot be improved as expected. It was. This is because, when the formation position of the resin reservoir 23 is close to the weld part P2, the resin flow due to the collapse of the pressure balance of the molten resin that confronts and merges at the weld part P2 is reduced, and each molten resin that is the weld part P2 It is presumed that the facing surface Z is nearly flat.

  Therefore, in order to improve the bonding strength of the weld part P2 by increasing the resin flow in the circumferential direction of the molten resin in the vicinity of the weld part P2 and by flattening the opposing surface Z of the weld part P2, a resin pool is obtained. 23 is preferably provided between the resin injection gate 10 and the weld portion P2 at the peripheral edge of the ring-shaped cavity 19 and within a range of 5/6 from the resin injection gate 10.

In addition, this invention is not limited to the said embodiment, A deformation | transformation, improvement, etc. are possible suitably.
For example, the injection molding method is not limited to the injection molding method of the plastic seal for bearings, and can be applied to general resin rings in general.
Moreover, although fiber reinforced resin and liquid crystal polymer were used for the resin material, it is not limited to this, and various resins may be used. Further, the molding die used in the injection molding method is a side gate, However, the present invention is not limited to this, and may be applied to a submarine gate or the like.

  Next, a bending strength test performed to confirm the function and effect of the plastic seal 20 for bearings of the present invention molded by the above injection molding method will be described.

  In this test, the bearing plastic seal 20 molded by the injection molding method of the present embodiment using the molding die 21 shown in FIG. 1 is used as an example product, and the molding die 11 shown in FIG. Using the bearing plastic seal 1 molded by the injection molding method as a comparative product, the bending strength of each was measured. As the resin material, a liquid crystal polymer filled with 30 wt% glass fiber was used. Further, relative bending strengths of the example products when the bending strength of the comparative product was set to 1 were compared. The results are shown in the graph of FIG.

  As is apparent from the graph of FIG. 5, it was found that the example product which is the plastic seal for bearings of the present invention has a bending strength 5 times or more that of the comparative product. Further, in the test of incorporating the example product into the bearing, no cracks occurred in the weld portion.

It is a partial horizontal sectional view of the molding die for demonstrating the injection molding method of the plastic seal for bearings which concerns on this invention. It is an II-II cross-sectional arrow view in FIG. It is a schematic explanatory drawing which shows the state of the molten resin in the weld part in the ring-shaped cavity of the shaping die shown in FIG. It is a partial horizontal sectional view for demonstrating the modification of a shaping die. It is a graph which shows the strength of the bending strength in an Example. It is principal part sectional drawing of the ball bearing provided with the plastic seal for bearings. It is a partial horizontal sectional view of a molding die for explaining a conventional resin ring injection molding method. It is a schematic explanatory drawing which shows the state of the molten resin in the weld part in the ring-shaped cavity of the shaping die shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Injection gate 12 Reinforcement fiber 19 Ring-shaped cavity 20 Plastic seal for bearing 21 Molding die 23 Resin reservoir 25 Projection pin 27 Communication part P2 Weld part Z Opposite surface

Claims (3)

A ring-shaped plastic seal for bearings molded by injecting molten resin added with reinforcing fibers into the ring-shaped cavity from a resin injection gate provided at the periphery of the ring-shaped cavity formed in the molding die. There,
The center of the weld portion formed by joining the ends of the molten resin that have been injected into the ring-shaped cavity after injection molding into two flows is opposed to the circumference of the ring-shaped cavity. A plastic seal for bearings that protrudes in a non-flat convex shape in the direction. The plastic seal for bearings is provided with a resin reservoir into which a part of the molten resin can flow into a peripheral edge portion that is separated from the weld portion in the ring-shaped cavity,
The installation position of the resin reservoir is set to a range in which the distance on the periphery from the resin injection gate does not exceed 5/6 of the peripheral distance between the resin injection gate and the weld part,
In addition, the opening cross-sectional area of the communication portion that communicates the resin reservoir and the ring-shaped cavity is set in the resin reservoir after the molten resin injected into the ring-shaped cavity is filled in the ring-shaped cavity. Is set to a size that limits the amount of molten resin flowing from the ring cavity into the resin reservoir,
2. The plastic seal for bearings according to claim 1, wherein the molten resin is molded by injecting the molten resin from the resin injection gate into the ring-shaped cavity.   3. The plastic seal for a bearing according to claim 1, wherein the molten resin is a fiber reinforced resin or a liquid crystal polymer to which reinforcing fibers are added.

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