JP7684173B2 - Rolling bearing retainer and rolling bearing - Google Patents

Description

The present invention relates to a roller bearing retainer and a roller bearing, and in particular to a roller bearing retainer and a roller bearing used to support a rotating member that rotates at high speed, such as the main shaft of a machine tool.

In rolling bearings, rolling elements such as balls or cylindrical rollers are arranged in the raceway space between the inner and outer rings, and these rolling elements are held in place by a cage. Traditionally, bearing cages have been made from metal materials such as iron or high-strength brass, but there has been a shift towards using plastic materials for cages in order to extend the life of bearings and reduce their weight.

For example, duplex angular ball bearings and cylindrical roller bearings are widely used as bearings that support the main shafts of machine tools. Patent Document 1 describes a resin cage used in cylindrical roller bearings. This resin cage is a cage that includes one annular portion, multiple pillar portions, and multiple pockets formed between adjacent pillar portions in the circumferential direction, and is a cage known as a comb-type cage.

Patent Document 2 also describes a method for manufacturing a retainer (see also FIG. 1) having an annular portion and a columnar portion by injection molding using a resin material. Specifically, it describes that the molten resin injected into the cavity flows in two streams on both sides in the circumferential direction inside the cavity, and then merges again at a position on the opposite side radially opposite the gate, where the two streams are joined together to form a weld.

Patent No. 4387162 JP 2016-50616 A

As described above, in a resin cage formed by injection molding, molten resin is injected from a gate, and a weld is formed at the location where the flowing molten resin collides. Depending on the resin composition and molding conditions, a raised portion of the resin (hereinafter also referred to as a convex portion) may be formed in the weld. In addition, when the bearing rotates, the cage may come into sliding contact with a mating component such as a rolling element or raceway, and if a raised portion of the resin is formed in such a sliding contact area, there is a concern that this could lead to increased friction, increased torque, heat generation, etc.

The present invention was made to address these circumstances, and aims to provide a retainer for rolling bearings and a rolling bearing that can suppress increases in friction and torque during bearing operation, even in a retainer in which a resin protrusion (convex portion) is formed in the weld portion.

The rolling bearing retainer of the present invention has an annular portion and a number of pillar portions extending from the annular portion in one axial direction, and holds rolling elements between the pillar portions in the circumferential direction. The rolling bearing retainer is characterized in that the annular portion and the pillar portions are integrally formed by injection molding, at least the annular portion has a weld portion, and a protrusion that rises in the axial direction is formed on the axial end side of the annular portion where the weld portion is formed.

When the axial dimension of the protrusion is H and the axial thickness of the annular portion at the location where the protrusion is not formed is T, the relationship (H x 100/T) < 6.5% is satisfied.

The weld portion is formed to extend axially from the annular portion to the column portion.

The above-mentioned rolling bearing retainer is characterized in that the above-mentioned protrusions are formed in a plurality at equal intervals in the circumferential direction.

The number of the protrusions is half the number of the pillars.

The above-mentioned rolling bearing retainer is a comb-type retainer, and is characterized in that an extrusion pin mark is formed on the end side opposite to the axial end side where the above-mentioned protrusion is formed.

The above-mentioned rolling bearing retainer is characterized by having polyether ether ketone (PEEK) resin as the base resin and containing a fiber reinforcing agent.

The rolling bearing of the present invention is a rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a retainer that holds the rolling elements, characterized in that the retainer is the rolling bearing retainer of the present invention.

The rolling bearing is a double-row cylindrical roller bearing, and is characterized in that the retainer has a pair of separate comb-shaped retainers in the left and right rows, and the above-mentioned convex portion is formed on the mating surfaces of these retainers.

The roller bearing retainer of the present invention has a weld portion at least in the annular portion, and a protrusion that rises in the axial direction is formed on the axial end side of the annular portion where the weld portion is formed. Therefore, for example, the sliding form of the retainer can be selected taking into consideration the position of the protrusion in the weld portion, and therefore, increases in friction and torque during bearing operation in the retainer can be suppressed.

When the axial dimension of the protrusion is H and the axial thickness of the annular portion at the location where the protrusion is not formed is T, (H x 100/T) < 6.5% is satisfied, so even if the sliding form of the retainer is a form in which the axial end side of the annular portion is in sliding contact with the mating member, increases in friction and torque during bearing operation can be effectively suppressed.

The weld portion is formed to extend axially from the annular portion to the column portion, ensuring the strength of the weld portion.

In the above-mentioned rolling bearing retainer, multiple protrusions are formed at equal intervals in the circumferential direction, providing excellent rotational stability.

The rolling bearing of the present invention is a rolling bearing equipped with the rolling bearing retainer of the present invention, and in particular, the rolling bearing is a double row cylindrical roller bearing, and has a pair of separate comb retainers for the left and right rows as retainers, with convex portions formed on the mating surfaces of these retainers, which makes it possible to suppress increases in friction and torque during bearing operation.

1 is a perspective view showing an example of a cage for a rolling bearing of the present invention. 2 is a view of the rolling bearing retainer of FIG. 1 as viewed from the radial outside. FIG. 2 is a view of the rolling bearing retainer of FIG. 1 as viewed from one axial side. FIG. 1 is an axial cross-sectional view of an example of a rolling bearing (double row cylindrical roller bearing) of the present invention. FIG. FIG. 1 is a schematic diagram of an injection molding die.

An example of the roller bearing retainer of the present invention will be described with reference to Figure 1. Figure 1 is a perspective view of a comb-type retainer for a cylindrical roller bearing. The roller bearing retainer of the present invention is an annular member, and the direction parallel to the central axis of the retainer is called the "axial direction," the direction perpendicular to the central axis is called the "radial direction," and the direction around the axis centered on the central axis is called the "circumferential direction."

The cage 1 shown in FIG. 1 comprises an annular portion 2, a plurality (e.g., an even number) of column portions 3 extending in one axial direction from the inner surface 2a of the annular portion 2, and a plurality of pocket portions 4 formed between the circumferential side surfaces of the column portions 3 adjacent in the circumferential direction and which rotatably hold cylindrical rollers. The cage 1 is an injection molded body that is injection molded using a resin material, and the annular portion 2 and the column portions 3 are formed integrally.

When a retainer as shown in FIG. 1 is manufactured by injection molding, a weld is formed in the area where the molten resin joins during injection molding. The rolling bearing retainer of the present invention has a weld formed in at least the annular portion, and the position and dimensions of the raised portion (protrusion) of the resin caused by the formation of the weld are controlled to suppress an increase in friction. This protrusion will be explained using FIG. 2.

Figure 2 shows the retainer of Figure 1 as seen from the radial outside. In Figure 2, welds W are formed in the areas surrounded by dotted lines. That is, in retainer 1, welds W are formed in annular portion 2 and column portion 3, and more specifically, welds W are formed so as to extend in the axial direction from annular portion 2 to column portion 3. In column portion 3, welds W are located approximately in the center of column portion 3 in the circumferential direction. By forming welds W on column portion 3 as well, the area of the welds is larger than when they are formed only on annular portion 2, and the strength of the welds can be ensured.

In the retainer 1, a convex portion 5 that rises in the axial direction is formed on the axial end side of the annular portion 2 where the weld portion W is formed. The convex portion 5 is formed by the resin rising when the molten resin joins during injection molding, and is formed in a curved shape that bulges in the axial direction. In FIG. 2, the convex portion 5 is formed only on the outer surface 2b of the annular portion 2. On the other hand, the outer diameter surface of the retainer 1 (including the outer diameter surface 2c of the annular portion 2 and the outer diameter surface of the column portion 3) and the inner diameter surface of the retainer 1 are not formed with a convex portion due to the rise of the resin, and are annular. In addition, the tip surface of the column portion 3 is not formed with a convex portion due to the rise of the resin. In addition, a weld line is formed linearly toward the axis center on the outer surface 2b of the retainer 1. In this way, in the retainer for a rolling bearing of the present invention, the position of the convex portion in the weld portion is limited.

In addition, in the roller bearing retainer of the present invention, the circumferential positions of the retainer where the welds are formed coincide with the circumferential positions of the retainer where the protrusions are formed. In addition, the number of welds is the same as the number of protrusions.

Furthermore, by controlling the height (axial dimension) of the protrusion 5, as shown in FIG. 4 described later, it is possible to suppress an increase in friction, an increase in torque, heat generation, etc., even when the outer surface 2b is in sliding contact with a mating member. Specifically, when the axial dimension of the protrusion 5 is H and the axial thickness dimension of the annular portion 2 at the portion where the protrusion 5 is not formed is T, it is preferable to satisfy (H x 100/T) < 6.5%. If (H x 100/T) exceeds 6.5%, the protrusion ratio of the protrusion becomes large, which may be disadvantageous in terms of an increase in friction, an increase in torque, heat generation, etc. The axial dimension H of the protrusion 5 is the difference between the axial dimension of the portion of the outer surface 2b where the protrusion 5 is most raised in the axial direction and the axial dimension of the portion where the protrusion is not formed.

The protrusions 5 are present on the outer surface 2b from the outer diameter side to the inner diameter side of the retainer 1, and the axial dimension of the protrusions 5 near the outer diameter side is approximately the same as the axial dimension of the protrusions 5 near the inner diameter side. It is preferable that the protrusions 5 are uniformly present with approximately the same dimensions from the outer diameter side to the inner diameter side, as this makes them less susceptible to wear. In the present invention, a protrusion is defined as one where (H x 100/T) is greater than 0.5%. (H x 100/T) is more preferably 2.0% or more and less than 6.5%, and even more preferably 3.5% or more and less than 5.0%.

In the cage for rolling bearings of the present invention, the number of protrusions is not particularly limited, but it is preferable that multiple protrusions are formed. In particular, in a configuration in which multiple protrusions are formed, it is preferable that the protrusions are formed at equal intervals from each other in the circumferential direction. By arranging the protrusions evenly, rotational stability is easily obtained.

In the retainer 1 shown in FIG. 2, the number of protrusions 5 (the number of welds W) is set to half the number of columns 3. For example, the number of columns 3 is 28, while the number of protrusions 5 is set to 14. In addition, in the retainer 1 shown in FIG. 2, columns with welds W formed therein and columns without welds W formed therein are arranged alternately in the circumferential direction. In other words, the welds W are formed on every other column 3 in the circumferential direction.

Next, FIG. 3 shows the retainer of FIG. 1 as seen from one axial side (the tip side of the column portion). In other words, it shows the side opposite to the axial end side where the protrusion is formed. As shown in FIG. 3, the opposing pocket inner surfaces 3a of the column portions 3 adjacent in the circumferential direction of the annular portion 2 are each recessed in a shape that conforms to the circumferential surface of the cylindrical roller 7, and the shape of the pocket is a column that accommodates the cylindrical roller 7. In addition, the pocket inner surface 3a of the column portion 3 is provided with a groove-shaped lubricant reservoir portion 3b and a cutout portion 3c. The cutout portion 3c is formed on the axial end side of the inner diameter side of the column portion 3, and plays a role in encouraging the flow of lubricant from the outside into the pocket.

As shown in FIG. 3, the ejector pin mark 6 is formed on the end side opposite to the axial end side where the above-mentioned protrusion is formed. Specifically, the ejector pin mark 6 is formed on the tip surface 3d of the column portion 3 extending in one axial direction. The ejector pin mark 6 is formed by pressing the ejector pin when the molded body is removed from the injection molding die. For example, the ejector pin mark 6 is formed on the surface of the tip surface (axial end surface) of the column portion 3, in a concave shape that is slightly recessed from the tip surface, and the presence or absence of the ejector pin mark 6 can be confirmed visually. Note that the ejector pin mark 6 is located in approximately the center of the column portion 3 in the circumferential direction.

When a push-out pin mark is formed on a surface that comes into sliding contact with a mating member (such as the inner surface of a pocket or the inner surface of an annular portion), the roughness of the push-out pin mark may lead to an increase in friction. Therefore, as shown in Figure 3, by forming the push-out pin mark 6 on the tip surface 3d of the column portion 3, it is possible to suppress the increase in friction caused by the push-out pin mark 6.

Here, assuming that the diameter dimension of the ejection pin mark 6 is D and the minimum circumferential thickness of the column portion 3 is A, it is preferable to satisfy 0.10 < (D/A) < 0.90. If (D/A) is less than 0.10, the area of the ejection pin is small and the pressure is high, so the ejection pin mark formed becomes deep, and for example, there is a possibility that the column portion 3 may be deformed. Also, if (D/A) is greater than 0.90, there is a possibility of interference with the mold.

Here, in the present invention, the minimum circumferential thickness of the column means the minimum distance between the side surfaces of the column facing the pocket. In Figure 3, the axial end (front side of the figure) of column 3 is formed so that the distance between the side surfaces (circumferential thickness of the column) decreases stepwise or continuously from the outer diameter side to the inner diameter side, and the inner diameter side end is the part with the minimum circumferential thickness. In this case, the thickness of the axial end on the inner diameter side of column 3 is dimension A.

On the other hand, the diameter dimension D of the ejection pin mark is the diameter when the ejection pin mark 6 is circular, as shown in FIG. 3. The shape of the ejection pin mark corresponds to the shape of the axial cross section of the tip of the ejection pin, and is not limited to the circular shape of FIG. 3, and may be other shapes. For example, it may be a polygonal shape such as a triangle, a square, or a pentagon. When the ejection pin mark is a substantially regular polygon, the diameter dimension D of the ejection pin mark may be the diameter of a circle that passes through all of the vertices.

The above (D/A) value may be 0.50<(D/A)<0.90, 0.60<(D/A)<0.90, or 0.60<(D/A)<0.80. It may also be 0.10<(D/A)<0.50, 0.10<(D/A)<0.40, or 0.10<(D/A)<0.30.

As shown in FIG. 3, it is preferable that multiple ejector pin marks 6 are formed. In a configuration in which multiple ejector pin marks 6 are formed, it is more preferable that the ejector pin marks 6 are formed at equal intervals (equally distributed) from each other in the circumferential direction. This allows the multiple ejector pins to apply force evenly when removing the molded body from the injection molding die, allowing for stable ejection and suppressing deformation of the retainer. Also, in FIG. 3, the ejector pin marks 6 are formed on the tip surface 3d of each of all of the column portions 3.

In terms of the positional relationship with the weld portion, it is preferable that the ejector pin mark 6 is formed so as to overlap the weld portion formed at the axial end. In FIG. 3, the weld portion is formed in the axial direction including the axial end of every other column portion 3, for example, and the ejector pin mark 6 is formed so as to overlap the axial end of all of these weld portions. From the viewpoint of deformation of the molded body, it is more advantageous to use an ejector pin to eject from above the weld portion during extrusion. Furthermore, it is more preferable that the approximate center of the ejector pin mark 6 is in the weld portion (or the weld line) so that the left and right sides of the weld portion can be ejected approximately evenly.

Figure 4 shows a double row cylindrical roller bearing as an example of a cylindrical roller bearing to which the above-mentioned cylindrical roller bearing retainer is applied. The double row cylindrical roller bearing 11 includes an inner ring 12 and an outer ring 13, a plurality of cylindrical rollers 14, 14 arranged in two rows spaced apart in the axial direction between the inner ring 12 and the outer ring 13, and the above-mentioned two retainers 1, 1. The inner ring 12 is a double row raceway ring with a center flange in the axial center and outer flanges on both ends in the axial direction. The two retainers 1, 1 are arranged so that their annular portions 2, 2 are adjacent to each other, and the pocket portions 4, 4 hold the cylindrical rollers 14, 14 of each row at regular intervals in the circumferential direction. If necessary, lubricants such as grease are filled around the cylindrical rollers 14, 14 for lubrication. For example, the inner ring 12 is fitted to a main shaft of a machine tool or the like, and the outer ring 13 is fitted to a housing or the like, so that the double row cylindrical roller bearing 11 supports the main shaft in a rotatable state.

As shown in FIG. 4, in the double row cylindrical roller bearing 11, the retainers 1, 1 are arranged with the axial end faces of the annular portions 2, 2 (the back faces of the retainers 1, 1) facing each other. The retainers 1, 1 are a pair of comb-shaped retainers in separate left and right rows, and when the bearing rotates, the back faces of the retainers 1, 1 slide against each other. Even if the retainer has such a sliding configuration, by controlling the position and dimensions of the protrusions as described above, it is possible to suppress an increase in friction due to the sliding contact of the retainers 1, 1.

In addition, by using a retainer with multiple convex portions arranged at equal intervals in the circumferential direction as shown in Figure 2, for example, the retainers can be arranged or rotated so that a portion of one retainer where the convex portions are formed faces a portion of the other retainer where the convex portions are not formed, which is thought to achieve stable rotation.

In the above Figures 1 to 4, a cylindrical roller bearing cage is shown as an example of a rolling bearing cage of the present invention, but resin cages such as crown cages used for ball bearings are also annular molded bodies with welds formed in part thereof, to which the present invention can be applied. Furthermore, as long as the cage shape has a weld formed during injection molding, the present invention can also be applied to any other ball bearing, cylindrical roller bearing, tapered roller bearing, or needle roller bearing.

The rolling bearing cage of the present invention is a resin cage made by injection molding a resin material. The mold used to manufacture a resin cage by injection molding consists of a fixed mold (fixed side mold) and a movable mold (movable side mold) that can be clamped and opened relative to the fixed mold. Molten resin is injected from the gate into the molding cavity formed by the clamped fixed mold and movable mold, filling it and solidifying it, thereby molding a cage that corresponds to the shape of the molding cavity. The type, position, and number of gates can be set as appropriate.

For example, gates such as tunnel gates can be arranged at every other gate in the circumferential direction of the cavity portion that forms the inner diameter portion of the column portion. In this case, gate marks are formed on the inner diameter surface 3e (see Figure 3) of every other column portion 3 in the circumferential direction of the cage. By arranging in this way, weld portions are formed in every other column portion.

Figure 5 shows a schematic diagram of an injection molding die. The resin material used for injection molding of the retainer is molding pellets obtained by mixing and kneading a predetermined amount of fiber reinforcement and other materials into a base resin. The molding pellets are fed into a hopper 22 of an injection molding machine 21, and are introduced from the hopper 22 into a cylinder 23. The molding pellets are then heated and melted by a heater 24 in the cylinder 23, while being pushed by a screw 25, and passed through a metering section to be filled into the cylinder nozzle 26 as one shot of molten resin for a molded product. Molten resin is injected from the cylinder nozzle 26 through a gate 27a into a cavity in a mold 27 with the desired retainer shape (for example, the shape in Figure 1) to fill the cavity.

After molding, the fixed and movable dies are opened, and the compact is removed, for example, by advancing a number of ejection pins 28 toward the compact. These ejection pins 28 leave ejection pin marks 6 (see FIG. 3) on the retainer. The diameter of the tip of the ejection pin 28 can be set, for example, taking into account the shape of the retainer so as to satisfy the above-mentioned (D/A) relationship.

The base resin of the resin material of the roller bearing retainer of the present invention can be injection molded and can be any resin that has sufficient heat resistance and mechanical strength as a retainer material. Examples of synthetic resins that can be used as the base resin include polyamide (PA) resins such as polyamide 6 (PA6) resin, polyamide 6-6 (PA66) resin, and polyamide 4-6 (PA46) resin, injection moldable fluororesins such as PEEK resin, polytetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, and ethylene-tetrafluoroethylene copolymer (ETFE) resin, polyethylene (PE) resins such as low-density polyethylene, high-density polyethylene, and ultra-high molecular weight polyethylene, polycarbonate (PC) resin, polyacetal (POM) resin, wholly aromatic polyester resin, polysulfide (PPS) resin, polyamideimide (PAI) resin, polyetherimide (PEI) resin, and injection moldable polyimide (PI) resin. In each polyamide resin, the number indicates the number of carbon atoms between the amide bonds. Each of these synthetic resins may be used alone or as a polymer alloy of two or more types.

Among these, it is preferable to use at least one of PEEK resin, PA resin, and PPS resin as the base resin because of its excellent mechanical strength, rigidity, heat resistance, etc., and it is more preferable to use PEEK resin. PEEK resin is a crystalline thermoplastic resin with a polymer structure in which benzene rings are linked to carbonyl groups at the para position by ether bonds.

Here, when using PEEK resin, which has a relatively high viscosity, if the number of gates for pouring the molten resin is small, the strength of the welds may be weakened. Therefore, when using PEEK resin, it is preferable to have a larger number of gates than when using PA resin (e.g., PA66 resin). As a result, a cage that uses PEEK resin as the base resin is likely to have a large number of welds. For example, a cage that uses PEEK resin as the base resin has more than half the number of welds as the number of columns.

In addition, in order to improve mechanical strength such as elastic modulus, it is preferable to blend fiber reinforcing agents such as carbon fiber, glass fiber, aramid fiber, boron fiber, and various mineral fibers (whiskers) into the resin material, as long as the injection moldability is not hindered. As the fiber reinforcing agent, it is more preferable to blend glass fiber or carbon fiber, as these have excellent reinforcing effects and are easily available.

The amount of fiber reinforcement is preferably 10% to 50% by mass, and more preferably 10% to 40% by mass, of the total resin material. By keeping it within the above range, it becomes easier to improve the mechanical strength of the cage while ensuring the fluidity of the molten resin.

Additives other than fiber reinforcement agents can be added to the resin material as long as they do not impair the function or injection moldability of the cage. Other additives that can be added include, for example, solid lubricants such as polytetrafluoroethylene resin, inorganic fillers, antioxidants, antistatic agents, and mold release agents.

The materials constituting the above resin material can be mixed as necessary using a Henschel mixer, ball mixer, ribbon blender, or the like, and then melt-kneaded in a melt extruder such as a twin-screw kneading extruder to obtain pellets for molding. Note that the filler may be added using a side feed when melt-kneading in a twin-screw extruder, etc.

The roller bearing retainer of the present invention has a resin protrusion (convex portion) formed in the weld portion, but is able to suppress increases in friction and torque during bearing operation, making it suitable for use as a retainer for various roller bearings used in automobiles, motors, machine tools, etc.

REFERENCE SIGNS LIST 1 Cage 2 Annular portion 3 Column portion 4 Pocket portion 5 Convex portion 6 Ejector pin mark 7 Cylindrical roller 11 Double row cylindrical roller bearing 12 Inner ring 13 Outer ring 14 Cylindrical roller 21 Injection molding machine 22 Hopper 23 Cylinder 24 Heater 25 Screw 26 Cylinder nozzle 27 Mold 28 Ejector pin W Weld portion

Claims (8)

A cage for a rolling bearing having an annular portion and a plurality of column portions extending in one axial direction from the annular portion, the cage holding rolling elements between the column portions in a circumferential direction,
The retainer for a rolling bearing is characterized in that the annular portion and the column portion are integrally formed by injection molding, at least the annular portion has a weld portion , the weld portion is formed so as to extend in the axial direction from the annular portion to the column portion, and a convex portion raised in the axial direction is formed only on the axial end face of the annular portion where the weld portion is formed. The cage for a rolling bearing according to claim 1, characterized in that, when the axial dimension of the protrusion is H and the axial thickness of the annular portion at the location where the protrusion is not formed is T, (H x 100/T) < 6.5% is satisfied. 3. The cage for a rolling bearing according to claim 1, wherein the protrusions are formed in a plurality of portions at equal intervals in the circumferential direction. 4. The cage for a rolling bearing according to claim 1 , wherein the number of said projections is half the number of said pillars. 5. The rolling bearing retainer according to claim 1, wherein the rolling bearing retainer is a comb-type retainer, and an ejection pin mark is formed on an axial end side opposite to an axial end side on which the convex portion is formed. 6. The cage for a rolling bearing according to claim 1 , wherein the cage for a rolling bearing has a polyether ether ketone (PEEK) resin as a base resin and contains a fiber reinforcing agent. A rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage that holds the rolling elements,
7. A rolling bearing, wherein the cage is a rolling bearing cage according to any one of claims 1 to 6 . The rolling bearing according to claim 7, characterized in that the rolling bearing is a double row cylindrical roller bearing, the retainer has a pair of separate comb-type retainers in left and right rows, and the convex portion is formed on the mating surfaces of these retainers.

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