JP7534107B2 - Strength control method for plastic cages - Google Patents

Description

The present invention relates to a plastic cage that is incorporated into a rolling bearing.

As a plastic cage to be incorporated into a rolling bearing, the technology described in JP 2011-085231 A (Patent Document 1) is known. The synthetic resin cage described in Patent Document 1 is a cage to be incorporated into a tapered roller bearing, and has a large diameter rim portion, a small diameter rim portion, and multiple pillar portions that span these rim portions, and is manufactured by injection molding.

Molten synthetic resin is supplied from a runner to the cavity of the mold that corresponds to the cage in Patent Document 1. The unsolidified molten synthetic resin fed from different directions meets within this cavity. Such a meeting point is called a weld, and the strength of the synthetic resin cage decreases at the weld. Therefore, in Patent Document 1, the weld is positioned in a part that is not connected to the rim part and the column part, to prevent a decrease in strength.

JP 2011-085231 A

There are multiple welds located within the plastic cage. As shown in Patent Document 1, the multiple welds are scattered throughout the rim and column sections. The location of the multiple welds that meets last is called the final weld, and it has particularly low strength among the multiple welds. Patent Document 1 does not specify the location of the final weld, leaving room for improvement in improving the strength of plastic cages.

The purpose of the present invention is to further improve the durability and reliability of plastic cages by specifying the position of the final weld and managing its strength.

For this purpose, the resin cage of the present invention is a cage that includes a pair of ring parts arranged with a distance Lc in the axial direction, and multiple pillar parts, one end of which is connected to one ring part and the other end of which is connected to the other ring part, and the one ring part and the other ring part are each injection molded with resin, and among the pockets defined by the pillar parts adjacent to each other in the circumferential direction of the cage, the distance between the pocket surface of one pillar part and the pocket surface of the other pillar part is Lp, and the pillar parts have one end of an axial dimension Lp that is defined to be equal to the distance Lp, the other end of an axial dimension Lp that is defined to be equal to the distance Lp, and a central range of the remaining axial dimension Lc-2Lp based on the above-mentioned pillar part distance Lp and ring part distance Lc, and the unsolidified resin injected into a mold corresponding to the cage meets at multiple points to form welds, and the final weld that meets last among the multiple welds exists in the central range of the above-mentioned axial dimension Lc-2Lp of the pillar parts.

According to the present invention, the position of the final weld is specified to be within the central range of the column portion, sufficiently away from the pocket corners of the plastic cage, thereby improving the strength and durability of the plastic cage compared to conventional methods.

In a preferred aspect of the present invention, the welds are provided only in the column portion. According to this aspect, no welds, which would be a weak point in terms of strength, are formed in the ring portion, further improving the strength and durability of the plastic cage. More preferably, all of the multiple welds are disposed in the central ranges described above. In another aspect of the present invention, a weld that is not a final weld is formed in the ring portion.

The inventor's plastic cage holds rollers, and is particularly suitable for needle rollers. The needle roller with cage of the present invention comprises the above-mentioned plastic cage and needle rollers held in the pocket. In another aspect, the above-mentioned plastic cage may be a cage that holds rollers other than needle rollers.

The location of the needle roller with cage of the present invention is not particularly limited, but in one aspect of the present invention, the needle roller with cage is provided in a planetary gear mechanism that includes a sun gear, a ring gear, a planetary gear, and a carrier, and is disposed in an annular gap defined by the center hole of the planetary gear and a pinion shaft that is erected on the carrier and passed through the center hole of the planetary gear. This aspect improves the strength and durability of the plastic cage in the pinion shaft that receives centrifugal force due to revolution. Therefore, the strength and durability of the planetary gear mechanism are improved compared to conventional methods.

The strength management method of the present invention involves preparing multiple plastic cages as described above, selecting at least one test plastic cage from the group of plastic cages, cutting each ring portion of the test plastic cage to cut out the column portion including the final weld and the ring portions that connect to both ends of the column portion, measuring the strength of the final weld by pulling one end side and the other end side that sandwich the final weld of the cut-out cage portion including the final weld, and managing the strength of the multiple plastic cages based on the measurement results. With this method, the strength of the plastic cages can be appropriately managed.

In this way, the present invention improves the strength of the plastic cage. In addition, the strength of the plastic cage is properly managed, improving the durability and reliability of the plastic cage.

FIG. 1 is a front view showing a planetary gear mechanism equipped with a rolling bearing according to the present invention. FIG. 1 is a perspective view showing a roller and cage assembly according to an embodiment of the present invention. FIG. 3 is a perspective view showing a resin cage taken out from FIG. 2 . FIG. 3 is a side view showing the resin cage taken out from FIG. 2 . 5 is a side view showing one post portion cut out from the resin cage of FIG. 4. FIG.

The following describes in detail an embodiment of the present invention with reference to the drawings. FIG. 1 is a front view showing a planetary gear mechanism equipped with a rolling bearing of the present invention. The planetary gear mechanism 100 includes an internal gear (ring gear) 101 that has internal teeth and surrounds the outer periphery, a sun gear (sun gear) 102 that has external teeth and is positioned at the center of the internal gear 101, and a number of planetary gears (pinions) 103 that have external teeth and are positioned between the internal gear 101 and the sun gear 102.

Each planetary gear 103 meshes with one internal gear 101 and one sun gear 102. A shaft-shaped pinion shaft 105 passes through the central hole of each planetary gear 103. The wall surface of the central hole forms the inner peripheral surface of the planetary gear 103. A roller with cage 10 is arranged in the annular space defined by the inner peripheral surface of the planetary gear 103 and the outer peripheral surface of the pinion shaft 105.

The ends of each pinion shaft 105 are fixed to a common carrier (not shown). This allows multiple planetary gears 103 to be supported by a single carrier. Each planetary gear 103 is also supported rotatably by a roller cage 10.

For example, if the sun gear 102 rotates clockwise as shown by the arrow in FIG. 1 while the internal gear 101 is stopped rotating, each planetary gear 103 rotates counterclockwise and revolves clockwise around the outer periphery of the sun gear 102, causing the carrier to rotate clockwise.

The planetary gear mechanism 100 is used, for example, in automatic transmissions for automobiles, which are becoming increasingly multi-stage. A roller cage 10 is used to support the planetary gear 103 in the planetary gear mechanism 100 so that it can revolve and rotate about its axis.

Figure 2 is a perspective view showing a roller and cage assembly according to one embodiment of the present invention. Figure 3 is a perspective view showing the cage removed from Figure 2. Figure 4 is a side view showing the cage removed from Figure 2. In the following explanation, the direction along the central axis of the roller and cage assembly 10 is called the "axial direction", the direction perpendicular to the central axis is called the "radial direction", and the circumferential direction around the central axis is called the "circumferential direction". The roller and cage assembly 10 is composed of multiple rollers 12 and one cage 13. The cage 13 has multiple pockets 14 that hold the rollers 12. The rollers 12 are metallic needle rollers, and the roller length is at least twice the roller diameter. The cage 13 is made of resin.

The outer peripheral surface of the pinion shaft 105 (Figure 1) is the inner raceway surface on which the rollers 12, which are rolling elements, roll. The inner peripheral surface of the planetary gear 103 includes the outer raceway surface on which the rollers 12 roll.

The cage 13 is a cage type and has a pair of ring portions 30 and a number of pillar portions 31 that connect the pair of ring portions 30 to each other. The pillar portions 31 extend in the axial direction of the cage 13 and are connected to the pair of ring portions 30 at both ends 32, 32. A pocket 14 in which the rollers 12 are placed is defined between the pillar portions 31, 31 adjacent in the circumferential direction. The pocket 14 is surrounded by pocket surfaces 33, 33 formed on the adjacent pillar portions 31, 31 and facing each other in the circumferential direction, inner end surfaces 34, 34 formed on the pair of ring portions 30 and facing each other in the axial direction, and four corners 14r that connect the pocket surfaces 33 and the inner end surfaces 34.

The pocket surface 33 extends from one end 32 to the other end 32 and faces the rolling surface of the roller 12. The inner end surface 34 faces the end surface of the roller 12. The distance Lp between the opposing pocket surfaces 33, 33 is larger than the diameter of the roller 12, and the distance Lc between the opposing inner end surfaces 34, 34 is larger than the overall length of the roller 12. When viewed from the outer diameter side of the cage 13, the pocket 14 is rectangular, and the four corners 14r are formed in an arc shape. Note that the distance Lp refers to the distance in the short direction (bearing circumferential direction) of the pocket 14, and more specifically, refers to the distance from the end of the column portion 31 to the end of the column portion 31 that faces each other through the pocket 14. When the corner 14r of the pocket 14 is formed in an R (arc) shape as in this embodiment, it should be understood that the distance Lp includes the arc radius of one corner 14r and the arc radius of the other corner 14r. The same applies when the pocket 14 is an irregular pocket.

Although not shown, roller stopper protrusions are formed on the inner diameter side and outer diameter side portions of the pocket surface 33. The roller stopper protrusions restrict the radial movement of the rollers 12 to hold the rollers 12 in the pockets 14. The axial position and number of the roller stopper protrusions are not particularly limited. In a cross section perpendicular to the axis of the cage 13, the cross-sectional shape of the pockets 14 is rectangular. In contrast, the cross-sectional shape of the column portion 31 is a trapezoid that is larger on the outer diameter side than on the inner diameter side.

The cage 13 is manufactured by injection molding, and unsolidified synthetic resin is pumped into a cavity in a mold that corresponds to the cage 13. The position of the final weld can be adjusted by adjusting the number of liners connected to the mold cavity, their arrangement, and the flow rate. The unsolidified resin meets approximately in the center of the length of the column 31 to form weld 31w. Note that weld 31w should be understood as a three-dimensional region distributed along the length of column 31, rather than a clearly visible surface such as a cross section perpendicular to the axis of the cage.

The last weld to be formed among the multiple welds 31w is called the final weld 31y. The position of the final weld 31y is determined by performing a short shot (incomplete filling) on one randomly selected retainer during the manufacturing process of the multiple retainers 13.

In this embodiment, the axial length of the end 32 is defined as the distance Lp between the pocket surfaces 33, 33 described above. The position of the final weld 31y is defined and arranged in a region of the column portion 31 excluding both ends 32, 32. The distance between the pair of ring portions 30, 30, i.e., the axial length of the column portion 31, is Lc, so the position of the final weld 31y is included in the central range that occupies the center of the column portion 31. Based on the distance Lp and the distance Lc, the longitudinal dimension of the central range of the column portion 31 is defined as Lc-2Lp.

Of the multiple welds, the weld farthest from the liner (gate position) (not shown) is the part where the unsolidified synthetic resin meets last, and therefore is the part with the weakest strength (final weld). In this embodiment, the location of this final weld is specified, and the strength of the group of retainers 13, 13, ... is also managed. This ensures the strength of the resin retainer 13.

In this embodiment, the final weld 31y is positioned at the column portion 31, and is spaced from the corner 14r of the pocket 14 by at least the distance Lp, which is the short dimension of the pocket 14. By spaced the final weld 31y, which has the weakest strength, from the pocket corner 14r in this way, the final weld 31y is not affected by the stress generated at the pocket corner 14r. As a result, the retainer 13 does not break prematurely, and retainer strength can be ensured.

Strength management is performed according to the following procedure. First, a test resin cage is randomly selected from the multiple resin cages 13, 13.... Next, each ring portion 30 of the test resin cage is cut at circumferential locations x, x shown by dashed lines in Figure 4, and one column portion 31 with a final weld 31y is cut out. The distance between the two circumferential locations x, x is greater than the circumferential dimension of the column portion 31. The cut surface formed in the ring portion 30 at the circumferential location x connects with the pocket 14. Figure 5 is a side view showing the cut-out test specimen T. The test specimen T includes the column portion 31 and ring portions 30p, 30p that are respectively connected to both ends of the column portion 31.

Next, the ring portions 30p, 30p at both ends of the test specimen T are gripped and pulled in the longitudinal direction of the column portion 31, i.e., the axial direction of the retainer 13, until it breaks. By controlling the breaking stress at this time, the strength of the final weld 31y can be easily and reliably controlled during manufacturing. A gripping margin is required during the tensile test of the final weld 31y, but since the position of the final weld 31y is set at a distance from the pocket corner 14r, the final weld 31y is not gripped and the strength of the final weld 31y is measured correctly. If the gripping margin is small and slips, it is possible to grip at least one of the one end 32 and the other end 32 of the column portion in addition to the ring portions 30p, 30p, while avoiding the final weld 31y.

Although the embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the illustrated embodiment. Various modifications and variations can be made to the illustrated embodiment within the same scope as the present invention or within an equivalent scope.

The present invention can be advantageously used in rolling bearings.

10 roller and cage; 12 roller; 13 cage;
14 pocket, 14r pocket corner, 30 ring portion,
30p ring part, 31 column part, 31w weld,
31y final weld, 32 end, 33 pocket surface,
34 Axial inner end surface, 100 Planetary gear mechanism,
105 pinion shaft, Lc, Lp spacing, T test specimen.

Claims (2)

a cage including a pair of ring portions arranged with an interval Lc in an axial direction, and a plurality of pillar portions each having one end coupled to one of the ring portions and the other end coupled to the other of the ring portions, the one ring portion and the other ring portion being injection molded from a resin,
Among pockets defined by the column portions adjacent to each other in the circumferential direction of the cage, a distance between a pocket surface of one of the column portions and a pocket surface of the other of the column portions is defined as Lp, and the column portions each have one end portion having an axial dimension Lp equal to the distance Lp, another end portion having an axial dimension Lp equal to the distance Lp, and a central range of an axial dimension Lc-2Lp based on the distance Lp and the distance Lc,
The unsolidified resin injected into the cavity of the mold corresponding to the retainer meets at a plurality of points to form welds;
preparing a plurality of resin cages, each of which has a final weld that meets last among the plurality of welds in the central region of the column portion;
Selecting at least one test resin cage from the plurality of resin cages;
The ring portion of the test resin cage is cut to cut out the column portion including the final weld and ring portions connected to both ends of the column portion,
measuring the strength of the final weld by pulling one end side and the other end side of the cut-out retainer portion including the final weld,
A method for managing strength of a resin cage, the method comprising managing the strength of the plurality of resin cages based on the measurement results. The strength management method for a plastic cage according to claim 1, in which the weld is provided only on the column portion.

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