Strength management method for resin cage

Abstract

The resin cage (13) includes a pair of ring portions (30, 30) arranged at intervals (Lc) in the axial direction, and a plurality of column portions (31) with one end joined to one ring portion and the other end joined to the other ring portion. The one ring portion and the other ring portion are injection-molded from resin respectively. Among them, the interval between the pocket surface (33) of one column portion and the pocket surface (33) of the other column portion in the pocket (14) divided by adjacent column portions (31, 31) in the circumferential direction of the cage is set as (Lp). The column portion (31) is composed of an end portion (32) with an axial dimension (Lp) equal to the interval (Lp), an end portion (32) with an axial dimension (Lp) equal to the interval (Lp), and a central range of the remaining axial dimension (Lc - 2Lp) obtained based on the interval (Lp) and the interval (Lc). The uncured resin injected into the mold corresponding to the cage converges at multiple locations to form weld lines (31w, 31w····, 31y). The final weld line (31y) that converges last among the multiple weld lines exists within the central range of the axial dimension (Lc - 2Lp) of the column portion (31).

Description

Technical Field

[0001] The present invention relates to a resin cage fitted into a rolling bearing. Background Art

[0002] As a resin cage fitted into a rolling bearing, a technique described in, for example, Japanese Unexamined Patent Application Publication No. 2011-085231 (Patent Document 1) has been conventionally known. The synthetic resin cage described in Patent Document 1 is a cage fitted into a tapered roller bearing, and includes a large-diameter flange portion, a small-diameter flange portion, and a plurality of column portions bridging the flange portions, and is manufactured by injection molding.

[0003] Molten synthetic resin is supplied from a runner to a cavity of a mold corresponding to the cage of Patent Document 1. The uncured molten synthetic resin fed from different directions meets in the cavity. The meeting portion is called a weld line, and the strength of the synthetic resin cage decreases at the weld line. Therefore, in Patent Document 1, the weld line is located at a portion deviated from the continuous portion of the flange portion and the column portion to prevent a decrease in strength.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-085231 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] Weld lines are located at multiple positions within the resin cage. As also shown in the drawings of Patent Document 1, a plurality of weld lines are scattered in the flange portion and the column portion. The portion where the meeting of the plurality of weld lines is the latest is called the final weld line, and its strength is particularly small among the plurality of weld lines. In Patent Document 1, the position of the final weld line is not specified, and there is still room for improvement in enhancing the strength of the resin cage.

[0009] An object of the present invention is to further improve the durability and reliability of the resin cage by specifying the position of the final weld line and performing strength management.

[0010] Means for Solving the Problems

[0011] To achieve this object, the resin cage of the present invention includes a pair of ring portions arranged at an axial interval Lc, and a plurality of column portions having one end coupled to one ring portion and the other end coupled to the other ring portion. The one ring portion and the other ring portion are respectively injection-molded from resin. Among them, the interval between the pocket surface of one column portion and the pocket surface of the other column portion in the pockets defined by adjacent column portions in the circumferential direction of the cage is set as Lp. The column portion is composed of an end portion with an axial dimension Lp defined to be equal to the interval Lp, an end portion with an axial dimension Lp defined to be equal to the interval Lp, and a central range of the remaining axial dimension Lc - 2Lp obtained based on the interval Lp of the column portion and the interval Lc of the ring portion. The uncured resin injected into the mold corresponding to the cage converges at multiple locations to form weld lines, and the final weld line where the multiple weld lines finally converge exists in the central range of the axial dimension Lc - 2Lp of the column portion.

[0012] According to the present invention described above, the position of the final weld line is defined to be included in the central range of the column portion that is sufficiently separated from the pocket corner of the resin cage. Therefore, the strength and durability of the resin cage are improved compared to the prior art.

[0013] As a preferred embodiment of the present invention, the weld lines are provided only on the column portions. According to the above embodiment, the weld lines, which are the weak points in terms of strength, are not formed on the ring portions at all. Therefore, the strength and durability of the resin cage are further improved. More preferably, all of the multiple weld lines are respectively arranged within the above-mentioned central range. As another embodiment of the present invention, weld lines that are not the final weld line are formed on the ring portions.

[0014] The resin cage of the present inventor holds rollers and is particularly suitable for needle rollers. The needle roller with a cage of the present invention includes the above-mentioned resin cage and needle rollers held in the pockets. As another embodiment, the above-mentioned resin cage can be a cage for holding rollers other than needle rollers.

[0015] The arrangement position of the needle roller with a cage of the present invention is not particularly limited. However, as one embodiment of the present invention, the needle roller with a cage is provided in a planetary gear mechanism including a sun gear, a ring gear, planetary gears, and a planet carrier, and is arranged in an annular gap defined by the central hole of the planetary gear and a pinion shaft that is erected on the planet carrier and passes through the central hole of the planetary gear. According to the above embodiment, in the pinion shaft that bears the centrifugal force generated by revolution, the strength and durability of the resin cage are improved. Therefore, the strength and durability of the planetary gear mechanism are also improved compared to the prior art.

[0016] The strength management method of the present invention is as follows: Prepare a plurality of the above resin cages, select at least one test resin cage from this group of resin cages, cut each ring portion of the test resin cage, cut out a column portion including the final weld mark and ring portions respectively combined with both ends of the column portion, stretch one end side and the other end side sandwiching the final weld mark in the cut cage portion including the final weld mark, thereby measuring the strength of the final weld mark, and manage the strength of a plurality of resin cages based on the measurement result. According to the above method, the strength of the resin cage can be appropriately managed.

[0017] Advantages of the Invention

[0018] Thus, according to the present invention, the strength of the resin cage is increased. Moreover, the strength of the resin cage can be appropriately managed, and the durability and reliability of the resin cage are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a front view showing a planetary gear mechanism including a rolling bearing of the present invention.

[0020] Figure 2 is a perspective view showing a roller with a cage according to an embodiment of the present invention.

[0021] Figure 3 is taken from Figure 2 a perspective view showing a resin cage removed.

[0022] Figure 4 is taken from Figure 2 a side view showing a resin cage removed.

[0023] Figure 5 is a side view showing a column portion cut out from a resin cage of Figure 4 . DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a front view showing a planetary gear mechanism including a rolling bearing of the present invention. The planetary gear mechanism 100 includes: an internal gear (ring gear) 101 having internal teeth and surrounding the outer periphery; a sun gear (sun wheel) 102 having external teeth and disposed at the center of the internal gear 101; and a plurality of planetary gears (pinions) 103 having external teeth and disposed between the internal gear 101 and the sun gear 102.

[0025] Each planetary gear 103 meshes with an internal gear 101 and a sun gear 102. A shaft-shaped pinion shaft 105 passes through the center hole of each planetary gear 103. The hole wall surface of the center hole constitutes the inner peripheral surface of the planetary gear 103. The roller 10 with a cage is arranged in the annular space divided by the inner peripheral surface of the planetary gear 103 and the outer peripheral surface of the pinion shaft 105.

[0026] The ends of the pinion shafts 105 are fixed to a common planetary carrier (not shown). Thus, a plurality of planetary gears 103 are supported by one planetary carrier. Furthermore, each planetary gear 103 is rotatably supported by the rollers 10 with cages.

[0027] For example, when the internal gear 101 stops rotating, the sun gear 102 Figure 1 When rotating in the clockwise direction as indicated by the arrow, each planetary gear 103 rotates in the counterclockwise direction and revolves in the clockwise direction on the outer circumference of the sun gear 102, and the planetary carrier rotates in the clockwise direction.

[0028] The planetary gear mechanism 100 is used in, for example, an automatic transmission of an automobile whose gears are becoming increasingly multi-speed. The rollers 10 with cages are used to support the planetary gears 103 in the planetary gear mechanism 100 so as to be capable of orbital and rotational movement.

[0029] Figure 2 It is a perspective view showing a roller with a cage according to an embodiment of the present invention. Figure 3 is from Figure 2 Take out the stereogram showing the cage. Figure 4 is from Figure 2 A side view showing the cage being removed. In the following description, the direction along the center axis of the roller 10 with a cage is referred to as the "axial direction", the direction orthogonal to the center axis is referred to as the "radial direction", and the circumferential direction around the center axis is referred to as the "circumferential direction". The roller 10 with a cage is composed of a plurality of rollers 12 and a cage 13. The cage 13 has a plurality of pockets 14 for holding each roller 12. The roller 12 is a needle-shaped roller made of metal, and the roller length is more than twice the roller diameter. The cage 13 is made of resin.

[0030] Pinion shaft 105( Figure 1 ) is an inner raceway surface for the rollers 12 as rolling elements to roll on. The inner raceway surface of the planetary gear 103 includes an outer raceway surface for the rollers 12 to roll on.

[0031] The cage 13 is cage-shaped, having a pair of ring portions 30 and a plurality of column portions 31 that connect the pair of ring portions 30 to each other. The column portions 31 extend along the axial direction of the cage 13 and are joined to the pair of ring portions 30 through end portions 32, 32 at both ends. Pocket holes 14 for arranging the rollers 12 are defined between the circumferentially adjacent column portions 31, 31. The pocket holes 14 are surrounded by pocket hole surfaces 33, 33 that are respectively formed on the adjacent column portions 31, 31 and face each other in the circumferential direction, inner end surfaces 34, 34 that are respectively formed on the pair of ring portions 30 and face each other in the axial direction, and four corners 14r that connect the pocket hole surfaces 33 and the inner end surfaces 34.

[0032] The pocket hole surfaces 33 extend from one end portion 32 to the other end portion 32 and face the rolling surfaces of the rollers 12. The inner end surfaces 34 face the end surfaces of the rollers 12. The interval Lp between the opposing pocket hole surfaces 33, 33 is larger than the diameter of the roller 12, and the interval 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 holes 14 are rectangular, and the four corners 14r are formed in an arc shape. It should be noted that the interval Lp refers to the interval in the short side direction (circumferential direction of the bearing) of the pocket hole 14. More specifically, it refers to the interval from the end portion of the column portion 31 facing the pocket hole 14 to the end portion of the column portion 31. In the case where the corners 14r of the pocket hole 14 are formed in a rounded (arc) shape as in the present embodiment, the interval Lp can be understood to include the arc radius of one corner 14r and the arc radius of the other corner 14r. The same applies to the case where the pocket hole 14 is a special-shaped pocket hole.

[0033] It should be noted that although not shown, roller restricting protrusions are formed on the inner diameter side portion and the outer diameter side portion of the pocket hole surface 33. The roller restricting protrusions restrict the radial movement of the rollers 12 and hold the rollers 12 in the pocket holes 14. The axial position and number of the roller restricting protrusions are not particularly limited. In a cross-section perpendicular to the axis of the cage 13, the cross-sectional shape of the pocket hole 14 is rectangular. In contrast, the cross-sectional shape of the column portion 31 is trapezoidal with the outer diameter side larger than the inner diameter side.

[0034] The cage 13 is manufactured by injection molding, and uncured synthetic resin is fed into the cavity of the mold corresponding to the cage 13. The position of the final weld mark can be adjusted by adjusting the number of connections, arrangement, and flow rate of the runners connected to the cavity of the mold. The uncured resin converges at approximately the center in the length direction of the column portion 31 to form a weld mark 31w. It should be noted that it is desirable to understand that the weld mark 31w is not a surface clearly shown as in a cross-section perpendicular to the axis of the cage, but a three-dimensional region distributed over the length direction of the column portion 31.

[0035] The last formed weld mark among a plurality of weld marks 31w is referred to as the final weld mark 31y. The position of the final weld mark 31y is known by underfilling (incomplete filling) a randomly selected one of the plurality of cages 13 during the manufacturing process.

[0036] In the present embodiment, the axial length of the end portion 32 is defined as the interval Lp between the aforementioned pocket surfaces 33, 33. And the position of the final weld mark 31y is defined to be arranged in a region of the column portion 31 other than the two end portions 32, 32. The interval between the pair of ring portions 30, 30, that is, the axial length of the column portion 31 is Lc. Therefore, the position of the final weld mark 31y is included in the central range occupying the center of the column portion 31. Based on the interval Lp and the interval Lc, the lengthwise dimension of the central range of the column portion 31 is defined as Lc - 2Lp.

[0037] Among the plurality of weld marks, the weld mark far from the runner (gate position) (not shown) is the portion where the uncured synthetic resin meets the latest, that is, the weakest portion (final weld mark) in terms of strength. In the present embodiment, the location of this final weld mark is specified, and further, the strength of a group of cages 13, 13 ··· is managed. Thereby, the strength of the resin cage 13 is ensured.

[0038] In the present embodiment, the position of the final weld mark 31y is set to the column portion 31 and is set to be at least the width dimension (interval Lp) away from the corner 14r of the pocket 14. In this way, the weakest final weld mark 31y is separated from the pocket corner 14r. As a result, the final weld mark 31y is not affected by the stress generated at the pocket corner 14r. As a result, the cage 13 does not break prematurely, and the cage strength can be ensured.

[0039] Strength management is carried out according to the following steps. First, a test resin cage is randomly selected from a plurality of resin cages 13, 13 ···. Next, each ring portion 30 of the test resin cage is cut at the circumferential portions x, x shown by the single-dot chain line in Figure 4 to cut out a column portion 31 where the final weld mark 31y exists. The interval between the two circumferential portions x, x is larger than the circumferential dimension of the column portion 31. The circumferential portion x is formed at the cut surface of the ring portion 30 and is connected to the pocket 14. Figure 5 It is a side view showing the cut test piece T. The test piece T includes a column portion 31 and ring portions 30p, 30p respectively joined to both ends of the column portion 31.

[0040] Next, the ring portions 30p, 30p that grip both ends of the test body T are stretched along the length direction of the column portion 31, that is, the axial direction of the cage 13, until it breaks. By managing the breaking stress at this time, it is possible to easily and reliably manage the strength of the final weld mark 31y during manufacturing. When performing the tensile test on the final weld mark 31y, a gripping margin is required. However, since the position of the final weld mark 31y is at a distance from the pocket corner 14r, the strength of the final weld mark 31y can be accurately measured without gripping the final weld mark 31y. In the case where the gripping margin is small and there is slippage, at least one of the one end portion 32 and the other end portion 32 of the column portion may be gripped in addition to the ring portions 30p, 30p to avoid the final weld mark 31y.

[0041] As described above, the embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to the illustrated embodiments. Various modifications and deformations can be made within the same scope or an equivalent scope as the present invention for the illustrated embodiments.

[0042] Industrial Applicability

[0043] The present invention can be advantageously used for rolling bearings.

[0044] Symbol Explanation:

[0045] 10 Roller with cage, 12 Roller, 13 Cage, 14 Pocket, 14r Pocket corner, 30 Ring portion, 30p Ring part, 31 Column portion, 31w Weld mark, 31y Final weld mark, 32 End portion, 33 Pocket surface, 34 Axial inner end face, 100 Planetary gear mechanism, 105 Pinion shaft, Lc, Lp Spacing, T Test body.

Claims

1. A method for managing the strength of a resin cage, wherein, prepare a plurality of resin cages, the resin cage includes a pair of ring portions arranged at an interval Lc in the axial direction, and a plurality of column portions with one end combined with one of the ring portions and the other end combined with the other ring portion. One of the ring portions and the other ring portion are respectively injection-molded by resin, set the interval between the pocket surface of one column portion and the pocket surface of the other column portion in the pocket formed by the column portions adjacent to each other in the circumferential direction of the cage as Lp. The column portion is composed of an end portion with an axial dimension Lp equal to the interval Lp, an end portion with an axial dimension Lp equal to the interval Lp, and a central range with an axial dimension Lc - 2Lp obtained based on the interval Lp and the interval Lc, the uncured resin injected into the cavity of the mold corresponding to the cage converges at multiple locations to form weld lines, the final weld line where the last convergence among the multiple weld lines exists in the central range of the column portion, select at least one test resin cage from the plurality of resin cages, cut off the ring portion of the test resin cage, and cut out the column portion containing the final weld line and the ring portions respectively combined with both ends of the column portion, stretch the one end side and the other end side sandwiching the final weld line in the cut-out cage portion containing the final weld line, thereby measuring the strength of the final weld line, manage the strength of the plurality of resin cages based on the measurement result.

2. The method for managing the strength of a resin cage according to claim 1, wherein, the weld line is only provided on the column portion.

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