JP6977947B2 - Manufacturing method of bearing cage, mold for bearing cage, and bearing cage - Google Patents

Description

The present invention relates to a resin-made rolling bearing cage used for railroad vehicles, automobiles, industrial machines, etc., an injection molding die used for manufacturing the same, and a method for manufacturing a cage using the die.

Rolling bearings arrange rolling elements such as balls and cylindrical rollers in the raceway space between the inner ring and the outer ring, and hold these rolling elements by a cage. From the viewpoint of cost reduction and weight reduction of bearings, the cage may be made of resin, for example, it is manufactured by injection molding using a resin material. When an annular cage is manufactured by injection molding using a resin material, the molten resin 19 is injected into the molding cavity 18 through the runner 20 and the gate 21 with high pressure as shown in FIG. .. At this time, the molten resin 19 ejected from the gate 21 into the molding cavity 18 branches in a complicated manner, and after moving equidistantly, rejoins to form a molten resin joint portion called a weld portion 22. It has also been found that the strength of the welded portion is generally about half that of the non-welded portion. Therefore, improving the strength of the weld portion is an important issue for the cage using the resin material.

Conventionally, various proposals have been made for a resin cage as a method for ensuring the strength and accuracy of such a welded portion. For example, Patent Document 1 proposes a resin cage for bearings in which a weld line is inclined in the radial direction by providing a predetermined convex shape or the like in the cavity. Patent Document 2 proposes a resin cage for tapered roller bearings in which a weld line is provided on one of the annular portions and a wire member penetrating the formed surface is provided.

Japanese Unexamined Patent Publication No. 2016-8050 Japanese Unexamined Patent Publication No. 2016-142381

However, as in Patent Document 1, since a fixed shape and a convex shape are provided in the mold, adjustment of the resin material and injection molding conditions becomes complicated, and the strength (tension) of the weld portion desired for the usage conditions is complicated. It is not easy to manufacture a bearing cage that secures strength). Further, in the case where the wire member is provided in the weld line as in Patent Document 2, the number of parts is large and the product cost is high. In order to avoid an increase in manufacturing cost, it is desired to improve this strength by a simpler manufacturing method.

The present invention has been made in view of such a background, and is a cage for bearings having excellent strength in a welded portion, an injection molding die used for this production, and a method for manufacturing a cage using the mold. The purpose is to provide.

The bearing cage of the present invention is an annular bearing cage which is an injection molded body of a resin composition, and the cage is located between a plurality of pocket portions for holding a rolling element and each pocket portion. A pillar portion to be provided and both ring portions for fixing the pillar portion on both sides in the axial direction are provided, and at least one of the ring portions has a weld line at one or a plurality of points in the circumferential direction, and the weld line has a weld line. It is characterized in that it is convex on one side in the circumferential direction. Here, "the weld line is convex to one side in the circumferential direction" means that the weld line gradually follows the circumferential direction of the ring portion from the surface layer portion of the ring portion to the inside.

The bearing cage is a cage for tapered roller bearings, has a large-diameter ring portion and a small-diameter ring portion as the ring portion, and has one ring portion of the large-diameter ring portion and the small-diameter ring portion. It is characterized by having the weld line having a convex shape on one side in the circumferential direction.

The mold for a bearing cage of the present invention is a mold for a bearing cage for manufacturing an annular bearing cage by injection molding of a resin composition, and the bearing cage is a plurality of molds for holding a rolling element. A pocket portion, a pillar portion located between the pocket portions, and both ring portions for fixing the pillar portions on both sides in the axial direction are provided, and the molding cavity of the mold is in the shape of the bearing cage. The gate is arranged so that a weld line is formed at one or a plurality of points in the circumferential direction in at least one ring portion, and is connected to the cavity portion forming the at least one ring portion to form the weld line. Two or more resin pools are arranged at different positions, and the resin pool has a mechanism capable of drawing resin from the molding cavity due to a volume change and / or re-injecting the resin into the molding cavity. It is characterized by having.

The gate is arranged so as to form the weld line at a plurality of places of the ring portion, and any one resin pool is arranged so as to be sandwiched between the two weld lines, and the arbitrary one weld line is arranged. It is characterized in that it is adjacent to only one resin pool.

The bearing cage is a cage for tapered roller bearings, has a large-diameter ring portion and a small-diameter ring portion as the ring portion, and the gate is one of the large-diameter ring portion and the small-diameter ring portion. It is characterized in that it is arranged in a ring portion and the resin pool is arranged in the other ring portion.

The method for manufacturing a bearing cage of the present invention is a manufacturing method for manufacturing an annular bearing cage by injection molding of a resin composition using the mold of the present invention, and the molding cavity is passed through the gate. It has an injection filling step of injecting and filling the molten resin, and in the step, the volume of the resin pool is expanded to draw in the molten resin, and / or the volume of the resin pool is compressed to obtain the molten resin. It is characterized in that the weld line in the ring portion is convex to one side in the circumferential direction by reinjecting into the molding cavity.

The bearing cage of the present invention is an annular bearing cage which is an injection-molded body of a resin composition, and has a plurality of pocket portions for holding a rolling element, a pillar portion located between the pocket portions, and the same. It is provided with both ring portions for fixing the pillar portion on both sides in the axial direction, and at least one of the ring portions has a weld line at one or a plurality of points in the circumferential direction, and the weld line is on one side in the circumferential direction. Since it has a convex shape, the joint area at the weld portion can be increased, and the cage has excellent strength at the weld portion without providing a separate member or the like.

The bearing cage is a cage for tapered roller bearings, has a large-diameter ring portion and a small-diameter ring portion as ring portions, and has one ring portion of the large-diameter ring portion and the small-diameter ring portion in the circumferential direction. Since the weld line is convex on one side, the strength of the weld line can be improved in the tapered roller bearing cage in which the weld line is formed on the one ring portion side.

The mold for a bearing cage of the present invention is a mold for a bearing cage for manufacturing an annular bearing cage by injection molding of a resin composition, and the molding cavity thereof has the shape of the bearing cage. A gate is arranged so that a weld line is formed at one or a plurality of points in the circumferential direction in at least one ring portion, and the weld line is connected to a cavity portion forming the ring portion having the weld line, and the weld line is defined as the weld line. Since two or more resin pools are arranged at different positions, the resin pool has a mechanism capable of drawing the resin from the molding cavity due to the volume change and / or re-injecting the resin into the molding cavity. The capacity of the resin pool can be changed during injection filling (including holding pressure), and the resin can be drawn in and re-injected into the cavity of the resin once taken in. As a result, the weld line can be adjusted to follow the resin flow direction. As a result, a resin cage in which the weld line is convex on one side in the circumferential direction is obtained.

Further, in this mold, gates are arranged so as to form weld lines at a plurality of places in the ring portion, one resin pool is arranged between two weld lines, and one weld line is one resin. Since it is adjacent only to the pool, the weld line can be efficiently improved in the annular ring portion where a plurality of weld lines are formed.

The method for manufacturing a bearing cage of the present invention uses the above-mentioned mold, and in the injection filling step, the volume of the resin pool is expanded to draw in the molten resin, and / or the volume of the resin pool is compressed. Since the molten resin can be re-injected into the molding cavity and the weld line in the ring portion can be convex on one side in the circumferential direction, a cage having excellent weld strength can be manufactured.

It is a perspective view which shows the cage for the tapered roller bearing of this invention. It is a schematic diagram for the mold for a bearing cage of this invention. It is a partial perspective view of the cage molded by the mold of FIG. It is a figure which shows the outline of the molding mechanism by a resin pool. It is a figure which shows the cage tensile test result. It is a figure which shows the relationship between the water absorption rate and the tensile strength. It is a schematic diagram which shows the state of the resin in a weld part.

The bearing cage of the present invention will be described with reference to FIG. FIG. 1A is a perspective view showing an annular cage for tapered roller bearings. The bearing cage 1 is an injection-molded body of a resin composition, and has a plurality of pockets 5 for holding tapered rollers as rolling elements, a pillar 4 located between the pockets 5, and a pillar 4. It is provided with both ring portions 2 and 3 fixed on both sides in the axial direction. The bearing cage 1 holds a tapered tapered roller as a rolling element, and the ring portion has a small diameter side and a large diameter side when viewed in the axial direction. In the form shown in FIG. 1, a small diameter ring portion 2 and a large diameter ring portion 3 are provided. Since the gate at the time of injection molding is provided only between the pillars of the small diameter ring portion 2 (ring inner diameter side), a weld line (weld portion 8) is formed between the pillars of the large diameter ring portion 3. By providing the gate between all the pillars of the small diameter ring portion, a weld line is formed between all the pillars of the large diameter ring portion 3.

In order to improve the strength of the weld portion in the resin cage, it is important to increase the joint area in the weld portion. At the gate position as described above, the normal weld line is formed by merging the resins that have flowed substantially evenly from both sides in the ring circumferential direction, so that the weld line is along the axial direction between the pillars of the large diameter ring portion. It becomes a nearly vertical plane. On the other hand, in the bearing cage 1 of the present invention, as shown in FIG. 1 (b), the weld line is placed on one side in the ring circumferential direction by a special mold for molding the cage and a manufacturing method described later. It is said to be convex. This is a state in which the weld line gradually follows the circumferential direction (resin flow direction) of the ring portion from the surface layer portion of the large diameter ring portion 3 to the inside. In FIG. 1B, 6 is a resin portion and 7 is a fibrous filler. As a result, the bonding area is increased, a high bonding force is obtained, the fibrous filler is also along the resin flow, and the tensile strength at the weld portion is excellent. Therefore, it is possible to prevent problems such as damage to the cage at the weld portion.

The structure of the bearing cage mold of the present invention will be described with reference to FIGS. 2 and 3. FIG. 2 is a schematic view of the mold, and FIG. 3 is a partial perspective view of a cage molded by the mold. As shown in FIG. 2, the mold 11 is a bearing holder mold for manufacturing an annular bearing holder 1 by injection molding of a resin composition. The mold 11 has at least a fixed mold 12 and a movable mold 13 that can be clamped and opened with respect to the fixed mold 12, and by abutting these, a forming cavity having a desired bearing cage shape is provided. 14 is formed. One or a plurality of gates, which are resin injection ports, are provided in the molding cavity 14, and molten resin is injected from these gates to fill the molding cavity. When the inside of the molding cavity is filled with the resin, pressure is applied to compress the resin in the molding cavity (holding pressure). After the molten resin is cooled and solidified in the mold for a certain period of time, the mold is opened to obtain a resin bearing cage. The pocket portion of the annular cage can also be formed by a mold using a slide core.

The mold 11 of the present invention is connected to a cavity portion forming at least one ring portion, and two or more resin pools 16 are arranged at positions different from the weld line. The resin pool 16 is characterized by having a mechanism capable of drawing the resin from the molding cavity 14 due to a volume change and / or re-injecting the resin into the molding cavity. As the mode of the above mechanism of the resin pool 16, (1) the resin can be drawn from the molding cavity due to the volume change, (2) the resin can be re-injected into the molding cavity due to the volume change, (3) (1). And (2) are all possible, there are three aspects. Further, in the plurality of resin pools, the mode of the mechanism may be the same or different.

As shown in FIG. 3, by providing the gate 15 in the mold between the adjacent pillar portions 4 in the small diameter ring portion 2, a weld line is formed between the adjacent pillar portions 4 of the large diameter ring portion 3. The pillar. The weld line (dotted line of the ring portion) shown in the figure is for indicating the position, and the specific shape is as shown in FIG. 1 (b). In the form shown in FIG. 3, one resin pool 16 is arranged so as to be sandwiched between two weld lines, and one weld line is adjacent to only one resin pool 16. That is, the resin pool 16 is arranged between the weld lines skipped by one in the circumferential direction, and one resin pool 16 is responsible for improving the two weld lines. The weld line can be improved with a smaller number of resin pools as compared with the case where two resin pools sandwiching the weld line are provided for one weld line.

FIG. 4 shows an outline of the molding mechanism by the resin pool 16. As shown in FIG. 4A, the mold 11 is provided with a resin pool 16 leading to the molding cavity 14. The resin pool 16 is provided with a piston 17 that changes its volume. As shown in FIGS. 4A and 4B, when the molding cavity 14 is filled with the resin through the gate, the resin also flows into the resin pool 16. As shown in FIG. 4 (c), at the timing when the resin forms a weld in the molding cavity 14, the piston 17 installed in the resin pool 16 on the left side of the figure is operated so that the volume of the resin pool 16 is reduced. , The resin in the resin pool 16 is re-injected into the molding cavity 14. Further, the resin pool 16 on the right side in the drawing operates the piston 17 so that the volume of the resin pool 16 increases, and draws the resin in the molding cavity 14 into the resin pool 16.

By re-injecting and drawing the resin into the molding cavity 14 using the resin pool 16 in this way, internal flow of the filled resin is generated in the weld portion. As a result, the weld line, which is originally close to perpendicular to the circumferential direction of the ring portion, gradually becomes a state along the circumferential direction of the ring portion from the surface layer portion to the inside, and the tensile strength of the weld portion increases. Since the surface layer portion is located on the surface side of the mold, the cooling speed is faster than that inside, and the fluidity is inferior. Therefore, when the ring portion is pulled in or reinjected, the above state is obtained.

The control method of the variable resin pool mechanism by the resin pool 16 and the piston 17 is not limited to that shown in FIG. For example, as shown in FIG. 3, in the circumferential direction of the ring portion, when the resin pool 16 is arranged between the weld lines skipped by one in the circumferential direction, one resin pool 16 is responsible for improving the two weld lines. become. Therefore, reinjection and pull-in cannot be applied to one weld line at the same time. Therefore, in this case, either re-injection or pull-in is performed in all the resin pools 16, and the two weld lines adjacent to the resin pools 16 are set along the circumferential direction of the ring portion. Internal flow of the resin around it (both sides in the circumferential direction of the ring) can be caused by only reinjection or pulling in. If the resin pools cannot be arranged at equal intervals due to the number of pockets, the resin pools and the piston may be additionally provided at arbitrary locations.

When there are a plurality of weld lines, each weld line may be convex (along the flow direction) on one side in the ring circumferential direction, and the convex direction is the same among the weld lines. May be in the opposite direction. When one resin pool is responsible for improving two weld lines, the convex shapes on both side weld lines sandwiching the resin pool are in opposite directions.

Any known mechanism can be adopted as the variable resin pooling mechanism by the piston. In the example shown in FIG. 2, the mechanism is provided on the movable mold 13 side, but it may be provided on the fixed mold 12 side or the like. Further, the piston can be driven not only during injection filling but also during the holding time after filling. In addition, when driving the piston, a means for preventing backflow of resin from the gate can be appropriately adopted.

In addition, in the mold of the present invention, the weld line may be located at any ring portion, and the gate position may be provided at either the pillar portion or the ring portion. The number of gates can be set as appropriate. Further, as the gate method, a tunnel gate, a side gate, a disk gate and the like can be appropriately provided according to the forming position.

In addition, in FIG. 3, the resin pool is connected to the cavity portion forming the large diameter ring portion and is provided at a position different from the weld line, but the resin pool forms the small diameter ring portion. You may adopt the arrangement which connects to the cavity part to be provided and is provided at the position different from the weld line. Further, the resin pool may be connected to the cavity portion forming each ring of the large diameter ring portion and the small diameter ring portion, and may be arranged at a position different from the weld line.

The method for manufacturing the cage for bearings of the present invention is a method for manufacturing the cage of the present invention as described above, and the above-mentioned mold is used to expand the volume of the resin pool in the injection filling step. This is a method in which the molten resin is drawn in and / or the volume of the resin pool is compressed and the molten resin is reinjected into the molding cavity to make the weld line in the ring portion convex to one side in the circumferential direction.

As the resin composition used as the material of the bearing cage of the present invention, any resin composition can be used as long as it can be injection molded and has sufficient heat resistance and mechanical strength as the cage material. Examples of the synthetic resin serving as the base resin of this resin composition include polyamide 6 (PA6) resin, polyamide 6-6 (PA66) resin, polyamide 6-10 (PA610) resin, and polyamide 6-12 (PA612) resin. Polyamide (PA) resin such as polyamide 4-6 (PA46) resin, polyamide 9-T (PA9T) resin, polyamide 6-T (PA6T) resin, polymethoxylen adipamide (polyamide MXD-6) resin, injection molding Possible fluororesins, low density polyethylenes, high density polyethylenes, polyethylene (PE) resins such as ultrahigh molecular weight polyethylenes, polyacetal (POM) resins, polyphenylene sulfide (PPS) resins, polyether ether ketone (PEEK) resins, polyamideimide ( Examples thereof include PAI) resin, polyetherimide (PEI) resin, and injection moldable polyimide (PI) resin. Among these synthetic resins, PA resin is preferably used because it is excellent in heat resistance and injection moldability. Further, each of these synthetic resins may be used alone or may be a polymer alloy in which two or more kinds are mixed.

In addition, in order to improve the mechanical strength such as the elastic coefficient of the cage, these resin compositions include glass fiber, aramid fiber, carbon fiber, various mineral fibers (whisker), etc. as long as they do not impair the injection moldability. It is preferable to add the fibrous reinforcing material of. In particular, it is preferable to blend glass fiber or carbon fiber because of its excellent reinforcing effect and availability. The blending range of the fibrous reinforcing material is, for example, about 15 to 40% by weight with respect to the entire resin composition. In addition, additives other than the fibrous filler can be blended as long as the function of the cage and the injection moldability are not impaired.

In the welded part, the amount of resin per unit area that contributes to joining is important, and when a fibrous filler is blended, the strength can be ensured in the non-welded part, but the amount of fiber resin in the welded part is small, so on the contrary. The strength tends to decrease. In particular, when the fiber orientation is perpendicular to the resin flow direction, it is likely to break in the circumferential vertical cross section. In the present invention, as described above, since the weld line is convex on one side in the circumferential direction, the fibrous filler has the same orientation, and even in a configuration including the fibrous filler, the weld portion has sufficient strength. Can be maintained.

The rolling bearing using the bearing cage of the present invention can prevent problems such as damage to the cage in the weld. In addition, by adopting a resin cage, the cost and weight of the bearing can be reduced.

Example A cage having the shape shown in FIG. 3 (the overall shape is shown in FIG. 1) was molded with the mold shown in FIG. 2 using molding pellets of a resin material containing 25% by weight of glass fiber in PA66 resin. The positions of the resin pool and the gate are as shown in FIG. At the time of injection molding, the piston was driven from injection filling to holding pressure, and the weld line of the large-diameter ring portion was adjusted to be convex to one side in the circumferential direction. In order to confirm the tensile strength of the welded portion of this cage, a cage tensile test was carried out using the prepared cage, and the tensile strength (MPa) was measured. The results are shown in FIG. In addition, the relationship between the water absorption rate of this cage (water absorption amount (% by weight) with respect to the total weight of the cage) and the tensile strength (MPa) was investigated. The results are shown in FIG.

Comparative Example A cage was manufactured with the same materials and conditions as in Example 1 except that a mechanism consisting of a resin pool and a piston was not provided in the mold, and the tensile strength of the weld portion was determined by the same test as in Example 1. , The relationship between the water absorption rate of the cage and the tensile strength was investigated. The results are shown in FIGS. 5 and 6.

As shown in FIGS. 5 and 6, as a result of the test, it was confirmed that the example was superior in the tensile strength of the weld portion to that of the comparative example, and it was easy to maintain the tensile strength even when water was absorbed.

Since the bearing cage of the present invention has excellent strength in the weld portion, it can be widely used as a cage for rolling bearings used in railway vehicles, automobiles, industrial machines and the like. In particular, it can be suitably used as a cage for tapered roller bearings in which a weld line is formed on one ring portion side.

1 Bearing cage 2 Small diameter ring part 3 Large diameter ring part 4 Pillar part 5 Pocket part 6 Resin part 7 Fibrous filler 8 Weld part 11 Mold 12 Fixed type 13 Movable type 14 Molding cavity 15 Gate 16 Resin pool 17 Piston 18 Molding cavity 19 Molten resin 20 Runner 21 Gate 22 Weld part

Claims (5)

An annular bearing cage that is an injection molded product of a resin composition.
The cage comprises a plurality of pockets for holding the rolling elements, a pillar located between the pockets, and both ring portions for fixing the pillar on both sides in the axial direction.
At least one ring portion has weld lines at a plurality of points in the circumferential direction, and the weld lines are convex on one side in the circumferential direction, and the convex directions are opposite to each other between adjacent weld lines. Bearing cage characterized by being. The bearing cage is a cage for tapered roller bearings, and has a large-diameter ring portion and a small-diameter ring portion as the ring portion.
The bearing cage according to claim 1, wherein one of the large-diameter ring portion and the small-diameter ring portion has the weld line having a convex shape on one side in the circumferential direction. A mold for a bearing cage for manufacturing an annular bearing cage by injection molding of a resin composition, wherein the bearing cage is between a plurality of pockets for holding a rolling element and each pocket. It is provided with a pillar portion to be located and both ring portions for fixing the pillar portion on both sides in the axial direction.
The molding cavity of the mold has the shape of the bearing cage, and gates are arranged so that weld lines are formed at a plurality of points in the circumferential direction at at least one ring portion.
Two or more resin pools are arranged at positions different from the weld line in connection with the cavity portion forming the at least one ring portion, and any one resin pool is skipped in the circumferential direction. Placed between weld lines,
The resin pool is a mold for a bearing cage, which has a mechanism capable of drawing resin from the molding cavity due to a change in volume or re-injecting the resin into the molding cavity. The bearing cage is a cage for tapered roller bearings, and has a large-diameter ring portion and a small-diameter ring portion as the ring portion.
The mold for a bearing cage according to claim 3, wherein the gate is arranged in one ring portion of the large diameter ring portion and the small diameter ring portion, and the resin pool is arranged in the other ring portion. .. A manufacturing method for manufacturing an annular bearing cage by injection molding of a resin composition using the mold according to claim 3 or 4.
The molding cavity has an injection filling step of injecting and filling the molten resin through the gate.
In the step, the volume of the resin pool is expanded to draw in the molten resin, or the volume of the resin pool is compressed to re-inject the molten resin into the molding cavity, and the weld line in the ring portion is circumferentially oriented. A method for manufacturing a bearing cage, which is characterized by having a convex shape on one side.

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