Resin retainer

Abstract

To provide a resin cage having fatigue strength U or higher in the range of a maximum load applied to the resin cage without protruding from the axial side face of a deep groove ball bearing.SOLUTION: A thickness t in the axial direction of a pocket part 5a holding balls 4 in a crown type resin cage 5 at its portion having a minimum axial cross section area is set so that, when a predetermined maximum load F is applied to the crown type resin cage 5, stress generated in the portion having the minimum axial cross section area is lower than the fatigue strength U of the crown type resin cage 5, and the crown type resin cage 5 is located in a range inside a width B in the axial direction of the deep groove ball bearing 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin cage.

Background Art

[0002] Conventionally, a resin cage for a deep groove ball bearing manufactured by injection molding has been known. The resin cage is formed, for example, by injection molding using a mold in which a corresponding annular cavity is formed. The molten resin injected into the cavity separates and merges as it moves within the cavity. The molten resin within the cavity is joined to each other in a merged state and solidifies to form a weld portion.

[0003] On the other hand, in a deep groove ball bearing in which rolling elements are held by a resin cage, relative movement of the rolling elements with respect to the cage (advance or delay of the rolling elements) occurs due to the difference between the revolution speed of the rolling elements and the revolution speed of the resin cage. Due to the relative movement between the rolling elements and the resin cage, the pocket portion of the resin cage causes the rolling elements to repeatedly collide during rotation of the deep groove ball bearing. The resin cage repeatedly undergoes elastic deformation due to collisions with the rolling elements. That is, repeated stress is generated in the resin cage due to collisions with the rolling elements. In the resin cage, since the repeated stress concentrates on the weld portion, it has been disadvantageous in terms of affecting the fatigue life. Therefore, a resin cage is known in which the joining strength of the weld portion is improved to suppress the influence on the fatigue life of the resin cage. For example, it is as described in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The mold for molding the resin cage described in Patent Document 1 is configured such that the opening area of the resin reservoir portion connected to the cavity is larger than the opening area of the resin injection gate connected to the cavity. As a result, the molten resin filled in the cavity smoothly flows in without staying in the resin reservoir portion. As a result, convection of the molten resin occurs in the cavity after the weld portion is formed, and the contact area between the molten resins increases due to deformation of the weld portion. Therefore, even when a resin material with a relatively high melt viscosity is used, the strength of the weld portion of the resin cage can be improved. However, in the technique described in Patent Document 1, the deformation state of the weld portion in the cavity cannot be grasped. That is, it is not clear whether the strength of the weld portion of the resin cage is above the fatigue limit. For this reason, the resin cage was disadvantageous in that it was designed based on a safety factor that was larger than necessary so that the resin cage had a strength above the fatigue limit within the range of the maximum load applied to the resin cage.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a resin cage that does not protrude from the axial side surface of a deep groove ball bearing and has a strength above the fatigue limit within the range of the maximum load applied to the resin cage.

Means for Solving the Problems

[0007] That is, a first invention is a resin cage that holds a plurality of rolling elements of a deep groove ball bearing at equal intervals. The width in the axial direction of the portion where the axial cross-sectional area in the pocket portion that holds the rolling element in the resin cage is the smallest is such that when a predetermined maximum load is applied to the resin cage, the stress generated in the portion where the axial cross-sectional area is the smallest is less than the fatigue limit of the resin cage and the resin cage is located within the range inside the axial width of the deep groove ball bearing, and is included in the range calculated from Equation (1).

Number

[0008] The second invention is that the resin forming the resin cage is a polyamide synthetic resin.

[0009] The third invention is that the resin forming the resin cage contains a fiber-reinforced resin.

[0010] The fourth invention is that the reduction rate indicating the ratio by which the fatigue limit of the resin constituting the resin cage is reduced by the welded portion is 0.6 or more and 0.8 or less.

Advantages of the Invention

[0011] As an effect of the present invention, the following effects are achieved.

[0012] That is, in the first invention, the shape of the portion where the axial cross-sectional area of the pocket portion where the largest stress is considered to occur in the resin cage is the smallest is determined to satisfy formula (1). The resin cage incorporated in the deep groove ball bearing has a radial width that does not contact the inner and outer rings of the deep groove ball bearing, and when the assumed maximum load of the resin cage is applied to the resin cage, the stress generated in the portion where the axial cross-sectional area is the smallest is less than the fatigue limit of the resin constituting the resin cage. The axial thickness is such that. Further, formula (1) includes the reduction rate of the fatigue limit reduced by the welded portion. Therefore, the stress generated in the portion where the axial cross-sectional area of the resin cage is the smallest is less than the fatigue limit of the resin constituting the resin cage even if there is a welded portion in the portion where the axial cross-sectional area is the smallest. Furthermore, the pre-resin cage incorporated in the deep groove ball bearing has a thickness that does not protrude from the axial side surfaces of the inner and outer rings. As a result, it is possible to have a strength equal to or higher than the fatigue limit within the range of the maximum load applied to the resin cage without protruding from the axial side surfaces of the deep groove ball bearing.

[0013] The second and third inventions are to make the crown-shaped resin cage composed of a polyamide synthetic resin excellent in toughness, impact resistance and flexibility, or a fiber-reinforced resin containing glass fiber (GF), carbon fiber (CF), etc., so that the fatigue limit of the crown-shaped resin cage is improved. As a result, the crown-shaped resin cage can expand the range of the axial thickness required to have a strength above the fatigue limit within the range of the maximum load applied to the resin cage without protruding from the axial side surface of the deep groove ball bearing.

[0014] The fourth invention is to consider the reduction rate of the fatigue limit due to the weld portion of the resin cage, so that even if the portion with the minimum axial cross-sectional area has a weld portion, when the assumed maximum load of the cage is applied to the resin cage, the stress generated in the weld portion is less than the fatigue limit of the resin forming the resin cage. As a result, the crown-shaped resin cage can have a strength above the fatigue limit within the range of the maximum load applied to the resin cage without protruding from the axial side surface of the deep groove ball bearing.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] With reference to FIGS. 1 and 2, a deep groove ball bearing 1 according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of the deep groove ball bearing. FIG. 2 is a side view of a crowned resin cage according to an embodiment of the present invention.

[0017] As shown in FIGS. 1 and 2, the deep groove ball bearing 1 includes an inner ring 2, an outer ring 3, a plurality of balls 4 that are rotatably interposed between the inner ring 2 and the outer ring 3, and a crowned resin cage 5 that houses the balls 4. Hereinafter, the axial direction refers to the direction along the axis P of the deep groove ball bearing 1. The radial direction indicates a direction perpendicular to the axis P of the deep groove ball bearing 1.

[0018] The inner ring 2 is a radially inner raceway ring that guides the balls 4. The inner ring 2 has an annular inner ring raceway surface 2a on its outer peripheral surface for the balls 4 to roll. The inner ring raceway surface 2a is a groove having a cross-section on an arc when viewed in the axial cross-section.

[0019] The outer ring 3 is a radially outer raceway ring that guides the balls 4. The outer ring 3 has an inner diameter larger than the outer diameter of the inner ring 2. The outer ring 3 has an annular outer ring raceway surface 3a on its inner peripheral surface for the balls 4 to roll. The outer ring raceway surface 3a is a groove having a cross-section on an arc when viewed in the axial cross-section. The outer ring 3 is located on the same axis P as the inner ring 2. Also, the outer ring 3 is positioned such that the outer ring raceway surface 3a overlaps the inner ring raceway surface 2a when viewed in the radial direction.

[0020] The plurality of balls 4, which are rolling elements, are spherical rolling elements. The curvature of the surfaces of the plurality of balls 4 is substantially the same as the curvature of the inner ring raceway surface 2a and the outer ring raceway surface 3a. The balls 4 are positioned between the inner ring 2 and the outer ring 3 and arranged in the circumferential direction of the inner ring 2 and the outer ring 3. The plurality of balls 4 are in contact with the inner ring raceway surface 2a. Also, the plurality of balls 4 are in contact with the outer ring raceway surface 3a. That is, the plurality of balls 4 are sandwiched between the inner ring raceway surface 2a and the outer ring raceway surface 3a. The plurality of balls 4 roll on the inner ring raceway surface 2a and the outer ring raceway surface 3a. Thereby, the plurality of balls 4 support the outer ring 3 so as to be relatively rotatable with respect to the inner ring 2.

[0021] The crown-shaped resin retainer 5, which is a resin retainer, is a member that holds a plurality of balls 4. The crown-shaped resin retainer 5 is composed of polyamide 46 (PA46), polyamide 66 (PA66), polyamide 9T (PA9T), etc., which are polyamide synthetic resins. Note that as a reinforcing material, glass fiber (GF), carbon fiber (CF), etc. may be included in the synthetic resin. The crown-shaped resin retainer 5 is formed in a cylindrical shape. The crown-shaped resin retainer 5 has a plurality of pocket portions 5a that independently hold the balls 4. The plurality of pocket portions 5a are arranged at equal intervals in the circumferential direction of the crown-shaped resin retainer 5. The pocket portion 5a is a spherical concave portion that is recessed from one end portion in the axial direction toward the other end portion. The curvature of the pocket portion 5a is smaller than the curvature of the ball 4. That is, the pocket portion 5a is composed of a spherical surface with a radius larger than that of the ball 4. Thereby, when the ball 4 is positioned in the pocket portion 5a, a gap is generated between the surface of the ball 4 and the surface of the pocket portion 5a in the crown-shaped resin retainer 5.

[0022] As shown in FIG. 2, the crown-shaped resin retainer 5 has a pair of claw portions 5b extending to one side in the axial direction for each of the plurality of pocket portions 5a. The side surfaces on the pocket portion 5a side of the pair of claw portions 5b have spherical surfaces that are continuous with the spherical surface of the pocket portion 5a. Also, the spherical portion of the pocket portion 5a and the spherical portion of the claw portion 5b have the same curvature. Thereby, the claw portion 5b constitutes a part of the spherical portion of the pocket portion 5a. The minimum distance between the tips of the pair of claw portions 5b is smaller than the maximum width in the circumferential direction of the crown-shaped resin retainer 5 in the pocket portion 5a. That is, the pair of claw portions 5b limits the amount of movement of the ball 4 in the axial direction within the pocket portion 5a. Thus, the crown-shaped resin retainer 5 can hold the ball 4 in the pocket portion 5a by the pair of claw portions 5b and the ball 4 can roll within the pocket portion 5a. Also, the crown-shaped resin retainer 5 holds the ball 4 movably within the pocket portion 5a within the range of the gap between the ball 4 and the pocket portion 5a.

[0023] As shown in FIGS. 1 and 2, the deep groove ball bearing 1 configured as described above has an outer ring 3 and an inner ring 2 configured to be relatively rotatable via a plurality of balls 4. The plurality of balls 4 are held at regular intervals by a crowned resin cage 5 between the inner ring 2 and the outer ring 3. When the outer ring 3 and the inner ring 2 of the deep groove ball bearing 1 rotate relative to each other, the plurality of balls 4 roll on the inner ring raceway surface 2a and the outer ring raceway surface 3a while being held in the pocket portions 5a of the crowned resin cage 5. The plurality of balls 4 revolve in the circumferential direction of the deep groove ball bearing 1 together with the crowned resin cage 5 while rotating on their own axes within the pocket portions 5a. The crowned resin cage 5 revolves together with the plurality of balls 4 while moving radially by the amount of the gap between the balls 4 and the pocket portions 5a.

[0024] Next, with reference to FIGS. 3 and 4, the advance and delay of the balls 4 with respect to the pocket portions 5a of the crowned resin cage 5 will be described. FIG. 3 is a schematic diagram of the load state due to the advance and delay of the rolling elements with respect to the crowned resin cage according to an embodiment of the present invention. FIG. 4 is a graph showing the relationship between the load and the rolling element diameter under predetermined conditions in the crowned resin cage according to an embodiment of the present invention.

[0025] As shown in FIG. 3, when a radial load and an axial load are applied to the deep groove ball bearing 1, the revolution speed of the ball 4 varies depending on the contact angle, which is the angle between the direction of the load applied between the inner ring raceway surface 2a or the outer ring raceway surface 3a and the ball 4 and the direction perpendicular to the axis P of the deep groove ball bearing 1. On the other hand, the revolution speed of the crowned resin cage 5 is constant. Therefore, in the deep groove ball bearing 1, a state occurs in which the ball 4 moves (advances) in the revolution direction faster than the crowned resin cage 5 and a state occurs in which the ball 4 moves (lags) in the revolution direction slower than the crowned resin cage 5 due to the variation of the contact angle. When the revolution speed of the ball 4 is slower than the revolution speed of the crowned resin cage 5, the crowned resin cage 5 presses the ball 4 in the revolution direction. When the revolution speed of the ball 4 is faster than the revolution speed of the crowned resin cage 5, the ball 4 presses the crowned resin cage 5 in the revolution direction. As a result, a compressive load and a tensile load are generated in the crowned resin cage 5 while fluctuating during revolution (see the black-painted arrow). Further, in the crowned resin cage 5, a maximum compressive stress and a maximum tensile stress are generated in the cross section of the bottom portion of the pocket portion 5a having the minimum cross-sectional area in the axial direction.

[0026] As shown in FIG. 4, when the deep groove ball bearing 1 is used in a transmission under, for example, the following usage conditions, the load applied to the crowned resin cage 5 can be calculated by Equation (2) based on the measurement results. As shown in Equation (2), the maximum load F applied to the crowned resin cage 5 can be approximated by a linear function having the diameter Da of the ball 4 as a variable. As shown in Equation (2), a predetermined maximum load F applied to the crowned resin cage 5 is calculated from the diameter Da of the ball and the usage and usage conditions of the deep groove ball bearing 1.

Equation

[0027] Next, with reference to FIG. 5, the reduction rate α of the fatigue limit U due to the weld portion W of the crown-shaped resin retainer 5 will be described. FIG. 5 is a schematic diagram of a fatigue test of the crown-shaped resin retainer according to an embodiment of the present invention. The weld portion W refers to a streak-like joint portion generated by the confluence of molten resins whose tip portions are cooled and whose viscosity increases within a mold.

[0028] As shown in FIG. 5, in the fatigue test of the crown-shaped resin retainer 5, a predetermined force is applied to the inner peripheral surface of the crown-shaped resin retainer 5 in the radially outward direction by a pair of semi-circular jigs J in a predetermined cycle (see the black arrows). A radially outward tensile load is repeatedly applied to the crown-shaped resin retainer 5. At this time, the fatigue test is performed on the crown-shaped resin retainer 5 with the weld portion W positioned in the gap between one jig J and the other jig J. Therefore, the largest tensile load is applied to the weld portion W of the crown-shaped resin retainer 5. As a result, the fatigue limit Uw at the weld portion W of the crown-shaped resin retainer 5 is estimated by the fatigue test. In addition, the fatigue limit U of the resin material of the crown-shaped resin retainer 5 is estimated using an un-reinforced dumbbell test piece without the weld portion W.

[0029] The reduction rate α due to the weld portion W in the fatigue limit U of the crown-shaped resin retainer 5 is calculated from the ratio of the fatigue limit Uw at the weld portion W of the crown-shaped resin retainer 5 to the fatigue limit U of the un-reinforced dumbbell test piece. The reduction rate α of the fatigue limit U due to the weld portion W can be expressed as Uw / U, for example, when the fatigue limit U of the un-reinforced dumbbell test piece and the fatigue limit Uw at the weld portion W of the crown-shaped resin retainer 5 are used. For example, when the reduction rate α of the fatigue limit U due to the weld portion W = 0.63, the fatigue limit Uw at the weld portion W of the crown-shaped resin retainer 5 is reduced to 63% of the fatigue limit U of the resin material of the crown-shaped resin retainer 5 due to the weld portion W. The reduction rate α of the fatigue limit U due to the weld portion W varies depending on the material used for the crown-shaped resin retainer 5 and fluctuates between 0.6 and 0.8 as an example.

[0030] Next, with reference to FIG. 6, the relationship between the fatigue limit U of the resin material and the shape in the crown-shaped resin retainer 5 will be described. FIG. 6 is a graph showing the relationship between the radial thickness of the crown-shaped resin retainer according to the embodiment of the present invention and the rolling element diameter.

[0031] As shown in FIG. 6, the crown-shaped resin retainer 5 will not undergo fatigue failure even if it has a weld portion W as long as the maximum stress value generated in the crown-shaped resin retainer 5 is less than 60% to less than 80% of the fatigue limit U of the resin material of the crown-shaped resin retainer 5. Therefore, in the crown-shaped resin retainer 5, the bottom portion of the pocket portion 5a that has a weld portion W and has the smallest axial cross-sectional area will not undergo fatigue failure even when a predetermined maximum load F is applied by satisfying Equation (3).

Equation

[0032] Also, the cross-sectional area S of the bottom portion of the pocket portion 5a in the crown-shaped resin retainer 5 where the axial cross-sectional area is the smallest (hereinafter referred to as "pocket bottom cross-sectional area S") can be calculated by Equation (4).

Equation

[0033] The crowned resin cage 5 is positioned between the inner ring 2 and the outer ring 3 such that the axis P of the inner ring 2 and the outer ring 3 coincides with the axis P of the crowned resin cage 5. Further, the crowned resin cage 5 holds a plurality of balls 4 in a state rotatable relative to the inner ring 2 and the outer ring 3. That is, in the deep groove ball bearing 1, the inner ring 2, the outer ring 3, and the crowned resin cage 5 are always separated from each other (see FIG. 1). Therefore, the radial thickness h of the crowned resin cage 5 is included in a range where it does not contact the inner ring 2 and the outer ring 3 even if it moves radially by the gap between the ball 4 and the pocket portion 5a.

[0034] Also, in the deep groove ball bearing 1, the radial interval between the inner ring 2 and the outer ring 3 is determined according to the diameter Da of the ball 4. Similarly, the radial thickness h of the crowned resin cage 5 is determined according to the diameter Da of the ball 4 to be held. The radial thickness h is proportional to the diameter Da of the ball 4. The radial thickness h is calculated by Equation (3).

Equation

[0035] The pocket bottom cross-sectional area S of the crowned resin cage 5 is calculated by Equation (6) shown from the axial thickness t of the bottom portion of the pocket portion 5a and the diameter Da of the ball 4 based on Equation (4) and Equation (5). Note that the bottom portion of the pocket portion 5a of the crowned resin cage 5 is spherical. Therefore, the axial thickness t of the bottom portion of the pocket portion 5a is the thinnest thickness as the thickness t.

Equation

[0036] From the above, the axial thickness t of the crowned resin cage 5 is shown by the maximum load F applied to the crowned resin cage 5, the diameter Da of the ball 4, and the fatigue limit U of the resin forming the crowned resin cage 5, from Equation (3) and Equation (6). The crowned resin cage 5 does not cause fatigue failure even if it has the weld portion W when the axial thickness t satisfies Equation (7).

Number

[0037] On the other hand, in the deep groove ball bearing 1, the crowned resin cage 5 does not protrude from the axial side surfaces of the inner ring 2 and the outer ring 3. That is, in the crowned resin cage 5, the axial thickness t of the bottom portion of the pocket portion 5a is smaller than the difference between the radius of the ball 4 and half of the axial width B of the inner ring 2 and the outer ring 3, based on the axial center of the deep groove ball bearing 1. Therefore, the axial thickness t of the crowned resin cage 5 satisfies the relationship shown in Equation (8), and is located within the range inside the axial width B of the inner ring 2 and the outer ring 3.

Number

[0038] By setting the axial thickness t of the crowned resin cage 5 so as to satisfy Equation (1) derived based on Equation (7) and Equation (8), the crowned resin cage 5 does not protrude from the axial side surfaces of the inner ring 2 and the outer ring 3, and fatigue failure does not occur even when the maximum load F is applied.

Number

[0039] In the crown-shaped resin cage 5 in the present embodiment, the axial thickness t of the pocket bottom cross-sectional area S where the maximum stress is considered to occur is determined so as to satisfy the formula (1). The crown-shaped resin cage 5 incorporated in the deep groove ball bearing 1 has a radial thickness h that does not contact the inner ring 2 and the outer ring 3, and when the assumed maximum load F of the crown-shaped resin cage 5 is applied to the resin cage, the stress generated in the pocket bottom cross-sectional area S is less than the fatigue limit U of the resin constituting the crown-shaped resin cage 5. Further, the crown-shaped resin cage 5 incorporated in the deep groove ball bearing 1 has the bottom portion of the pocket portion 5a located axially between the axial side surfaces of the inner ring 2 and the outer ring 3 and the ball 4. That is, the crown-shaped resin cage 5 is included within the volume of the deep groove ball bearing 1 surrounded by the inner ring 2 and the outer ring 3. Thus, the formula (1) calculates the range of the axial thickness t required for the crown-shaped resin cage 5 to satisfy the function from the axial width B of the deep groove ball bearing 1, the diameter Da of the ball 4, and the allowable load (maximum load F) of the crown-shaped resin cage 5. Thereby, the crown-shaped resin cage 5 can have a strength equal to or higher than the fatigue limit U within the range of the maximum load F applied to the crown-shaped resin cage 5 without protruding from the axial side surfaces of the inner ring 2 and the outer ring 3.

[0040] Also, by forming the crown-shaped resin cage 5 of a polyamide synthetic resin excellent in toughness, impact resistance, and flexibility, or by containing glass fiber (GF), carbon fiber (CF), etc., the fatigue limit U of the crown-shaped resin cage 5 is improved. Thereby, the crown-shaped resin cage 5 can expand the range of the axial thickness t required to have a strength equal to or higher than the fatigue limit U within the range of the maximum load F applied to the crown-shaped resin cage 5 without protruding from the axial side surfaces of the inner ring 2 and the outer ring 3.

[0041] Also, by considering the reduction rate α of the fatigue limit U due to the weld portion W of the crowned resin cage 5, even if the weld portion W is located at the bottom of the pocket portion 5a where the maximum stress occurs in the crowned resin cage 5, the stress generated when the assumed maximum load F of the crowned resin cage 5 is applied to the crowned resin cage 5 will be less than the fatigue limit U of the resin forming the crowned resin cage 5. As a result, the crowned resin cage 5 can have a strength equal to or greater than the fatigue limit U within the range of the maximum load F applied to the crowned resin cage 5 without protruding from the axial side surfaces of the inner ring 2 and the outer ring 3.

[0042] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to such embodiments at all, and is merely illustrative. Of course, the present invention can be implemented in various other forms without departing from the gist of the present invention. The scope of the present invention is indicated by the description in the claims, and further includes the equivalent meaning described in the claims and all modifications within the scope.

[0043] In addition, in the present embodiment, the deep groove ball bearing 1 has been described, but it can be applied to all bearings having a plurality of rolling elements. Similarly, in the present embodiment, the crowned resin cage 5 has been described, but it can be applied to resin cages that hold rolling elements.

[0044] In addition, in the present embodiment, the crowned resin cage 5 is made of a polyamide synthetic resin, but is not limited thereto. The crowned resin cage may be made of a synthetic resin.

Explanation of Reference Numerals

[0045] 1 Deep groove ball bearing 2 Inner ring 2a Inner ring raceway surface 3 Outer ring 3a Outer ring raceway surface 4 Ball 5 Crowned resin cage 5a Pocket portion F Maximum load applied to the crowned resin cage Fatigue limit U of the resin constituting the U-shaped resin retainer Reduction rate α of fatigue limit U due to the weld part W of the α-shaped resin retainer Diameter of the ball Da Axial thickness of the bottom part of the pocket part t Axial width of the deep groove ball bearing B Cross-sectional area S of the part where the axial cross-sectional area of the U-shaped resin retainer is the smallest Radial thickness h of the U-shaped resin retainer

Claims

1. A resin cage made of polyamide synthetic resin that holds a plurality of rolling elements of a deep groove ball bearing at equal intervals, The thinnest thickness in the axial direction of the portion where the axial cross-sectional area in the pocket portion for holding the rolling elements is the smallest is, When a predetermined allowable load is applied to the resin cage, the stress generated in the portion where the axial cross-sectional area is the smallest is less than the fatigue limit of the resin cage and the resin cage is located within the range inside the axial width of the deep groove ball bearing, and is included in the range calculated from Equation (1), Resin cage. 【Number 1】 F: Allowable load applied to the resin cage, U: Fatigue limit U of the resin constituting the resin cage, α: Reduction rate indicating the rate at which the fatigue limit of the resin constituting the resin cage is reduced by the weld portion which is the joint portion of the resin, Da: Diameter of the rolling element, t: Thickness in the axial direction of the minimum cross-sectional area, B: Axial width of the deep groove ball bearing, provided that (0.595·Da - 0.4181) > 0

2. The resin cage according to Claim 1, The resin forming the resin cage contains a fiber-reinforced resin, Resin cage.

3. The resin cage according to Claim 1 or 2, The reduction rate indicating the rate at which the fatigue limit of the resin constituting the resin cage is reduced by the weld portion is 0.6 or more and 0.8 or less, Resin cage.

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