Ball bearing

Abstract

To avoid interference between a crown-shaped resin holder and a bearing ring while suppressing a load on the resin holder due to delay in advance of a ball during operation of a ball bearing comprising the resin holder.SOLUTION: When a pocket diameter on a circumferential cut surface of a resin holder 4 is defined as dc, a pocket diameter on a radial cut surface of the resin holder 4 is defined as dr, and a diameter of a ball 3 is defined as Da, Da<dr<1.07Da≤dc is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ball bearing, and more particularly to a ball bearing having a cage formed in a crown shape from resin. [Background technology]

[0002] Conventionally, ball bearings for high speed rotation have adopted crown-shaped resin cages that are relatively lightweight and have excellent self-lubricating properties (for example, Patent Documents 1 and 2).

[0003] The crown-shaped plastic cage houses balls in pockets that are open on the inner and outer periphery and on one axial side of the plastic cage. In general, the plastic surface that forms the pockets is spherical. The diameter of the sphere in the spherical shape is set larger than the diameter of the balls to provide a pocket clearance between the plastic cage and the balls. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-263280 A [Patent Document 2] JP 2011-117609 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the load conditions, lubrication conditions, etc. applied to ball bearings have been becoming severer year by year. When the advance and retardation of balls during the rotation of a ball bearing become larger than the pocket clearance, the column portion of the crown-shaped resin cage is strongly pressed by the advanced balls, or the retarded balls are strongly pressed by the column portion, resulting in a load on the resin cage. If the ball diameter of the pocket shape is increased and the pocket clearance is set large, it is possible to avoid the occurrence of such a load. On the other hand, since the amount by which the resin cage can freely move in the radial direction with respect to the balls increases, there is a problem that the radial clearance between the resin cage and the race ring decreases, and interference between the two is likely to occur.

[0006] In view of the above background, the problem to be solved by the present invention is to suppress the load on the resin cage due to the advance and retardation of balls during the operation of a ball bearing provided with a crown-shaped resin cage, and to avoid interference between the resin cage and the race ring.

Means for Solving the Problem

[0007] In order to solve the above problems, the present invention provides a ball bearing including an inner ring, an outer ring, a plurality of balls disposed between the inner ring and the outer ring, and a resin cage that houses the balls in a plurality of pockets opened on one axial side. When the pocket diameter in the circumferential cross-section of the resin cage is dc, the pocket diameter in the radial cross-section of the resin cage is dr, and the diameter of the ball is Da, a ball bearing characterized by satisfying Da < dr < 1.07Da ≦ dc is adopted as Configuration 1.

[0008] According to Configuration 1 above, since 1.07Da ≦ dc is satisfied, it is difficult for the pocket clearance to become insufficient in the circumferential direction with respect to the advance and retardation of balls during the operation of the ball bearing, and the load on the crown-shaped resin cage can be suppressed. At the same time, since Da < dr < 1.07Da is satisfied, the pocket clearance is not too large in the radial direction with respect to the balls, and interference with the race ring (inner ring, outer ring) due to the radial movement of the resin cage can also be avoided.

[0009] In the above configuration 1, configuration 2 can be adopted in which the bearing is operated under operating conditions that satisfy the following: when the basic dynamic load rating is C and the dynamic equivalent load is P, the radial load (C / P) value is 0.17 or less, the axial load (C / P) value is 0.30 or less, and the relative inclination misalignment value between the inner ring and the outer ring is 1 / 300 (mm / mm) or less.

[0010] According to the above configuration 2, the advance / delay of the balls does not become larger than the pocket clearance, and it is possible to prevent the occurrence of a load on the resin cage due to the advance / delay of the balls.

[0011] In the above configuration 1 or 2, a configuration 3 can be adopted in which the resin cage is made of a thermoplastic engineering plastic or a thermosetting engineering plastic.

[0012] In the above configuration 1 or 2, a configuration 4 can be adopted in which the resin cage is made of fiber reinforced resin. Effect of the Invention

[0013] As described above, by adopting the above-mentioned configuration 1, the present invention makes it possible to suppress the load on the resin cage due to the advance / delay of the balls when a ball bearing having a crown-shaped resin cage is in operation, while avoiding interference between the resin cage and the raceway ring. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a partial cross-sectional view showing a circumferential cross section of a resin cage according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view showing a ball bearing equipped with the resin cage of FIG. [Diagram 3] FIG. 2 is a partial perspective view of the pocket of FIG. [Figure 4] Graph showing the relationship between ball advance / lag and pocket shape in a ball bearing according to an embodiment [Diagram 5]Graph showing the relationship between the radial movement amount of the resin cage and the pocket shape in the ball bearing according to the embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ball bearing according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0016] The ball bearing shown in Figures 1 to 3 (hereinafter simply referred to as "this ball bearing") comprises an inner ring 1, an outer ring 2, a plurality of balls 3 arranged between the inner ring 1 and the outer ring 2, and a crown-shaped resin cage 4 that holds these balls 3.

[0017] Hereinafter, the direction along the bearing center axis of this ball bearing (not shown, same below) will be referred to as the "axial direction", the direction perpendicular to the bearing center axis will be referred to as the "radial direction", and the circumferential direction going around the central axis will be referred to as the "circumferential direction".

[0018] The inner ring 1 and the outer ring 2 are single-row raceway rings for radial bearings having raceway grooves 1a and 2a, respectively, along the circumferential direction. The raceway grooves 1a and 2a have a radial groove depth relative to the outer diameter surface of the corresponding inner ring 1 or the inner diameter surface of the corresponding outer ring 2.

[0019] The resin retainer 4 is a ring-shaped resin part that forms pockets 4a at equal intervals in the circumferential direction, and is composed of a circular ring portion 4b that continues around the entire circumference, and a number of column portions 4c, 4c that extend in a cantilever manner from the circular ring portion 4b to one side in the axial direction.

[0020] The pocket 4a is made up of an annular portion 4b and multiple pillar portions 4c extending in a cantilever fashion from the annular portion 4b to one axial side, and is a portion that accommodates the balls 3 formed between adjacent pillar portions 4c in the circumferential direction. The pocket 4a is open on the inner circumference, outer circumference, and one axial side surface of the resin cage 4. The opening on one axial side of the pocket 4a is an opening for passing the balls 3 between the circumferentially adjacent pillar portions 4c, 4c and arranging them in the pocket 4a.

[0021] The entire resin cage 4 is formed seamlessly as a single piece by injection molding of resin. For example, a thermoplastic engineering plastic, a thermosetting engineering plastic, or a fiber-reinforced resin can be used as the resin.

[0022] Here, the engineering plastic may be at least one of thermoplastic resin and thermosetting resin, and may be either crystalline resin or non-crystalline resin. The synthetic resin may be a resin mainly composed of a thermosetting resin or a thermoplastic resin, and may contain other thermosetting resins, thermoplastic resins, rubber, glass fiber (GF), carbon fiber, carbon black, graphite, etc., as appropriate. For example, a resin having a heat resistance of 100°C or more and a tensile strength of 40 MPa or more may be adopted as the engineering plastic. The fiber-reinforced resin refers to a composite material in which a matrix resin as a base material is mixed with fibers as a reinforcing material at a predetermined ratio. Examples of the reinforcing material include carbon fiber and glass fiber.

[0023] A radial gap δi is provided between the resin cage 4 and the outer diameter surface of the inner ring 1. A radial gap δo is provided between the resin cage 4 and the inner diameter surface of the outer ring 2. The gaps δi and δo are set to be the same dimension.

[0024] The resin cage 4 is provided in a rolling element guided form guided by the balls 3 .

[0025] FIG. 1 shows a circumferential cut surface near the pocket 4a of the plastic cage 4, developed into a plane, and in particular shows a state in which the balls 3 are most offset to one side in the circumferential direction in a circumferential cross section including the geometric center of the pocket 4a and the center of the balls 3. FIG. 2 shows a radial cut surface of this ball bearing and plastic cage 4, and in particular shows a radial cut surface including the geometric center of the pocket 4a and the center of the balls 3. FIG. 3 shows a perspective view of one half of the pocket 4a, which is circumferentially divided into two equal halves, as viewed from one axial side and from the radially outer side. Here, the circumferential cut surface refers to a cross section on an imaginary cylindrical surface along the circumferential direction. Also, the radial cut surface refers to a cross section on an imaginary plane perpendicular to the bearing center axis. In addition, the geometric center of the pocket 4a refers to the intersection of an imaginary plane that bisects the pocket 4a in the circumferential direction, an imaginary plane that bisects the axial depth of the pocket 4a and is perpendicular to the bearing center axis, and an imaginary cylindrical surface that bisects the radial length of the pocket 4a.

[0026] Of the resin cage 4, the resin surface portion that forms the pocket 4a is a resin surface portion that allows contact with the balls 3 when the ball bearing rotates. In other words, the resin surface portion that forms the pocket 4a is made of a resin surface portion that restricts the range within which the resin cage 4 can freely move in the circumferential, axial, and radial directions relative to the multiple balls 3 by contacting the balls 3. For example, when a concave shape such as an oil groove that cannot come into contact with the balls is formed in a column portion or the like to hold or guide a lubricant between the balls and the resin cage, the concave resin surface portion does not correspond to a resin surface portion that forms a pocket.

[0027] A pocket gap is set between the resin surface portion forming the pocket 4a and the ball 3. The pocket gap is provided in the circumferential direction, the radial direction, and the axial direction based on the geometric shape of the resin surface portion forming the pocket 4a and the diameter of the ball 3.

[0028] The resin surface portion forming the pocket 4a is not spherical with the center of the sphere at the geometric center of the pocket 4a. As shown in FIG. 3, the resin surface portion forming the pocket 4a has a curvature in the direction of arrow A from the tip side of the column portion 4c toward the bottom side of the pocket 4a and a curvature in the direction of arrow B from the outer peripheral side to the inner peripheral side of the resin retainer 4, and is a curved surface with the curvature in the direction of arrow B set smaller than the curvature in the direction of arrow A.

[0029] Here, as shown in FIG. 1, let the pocket diameter in the circumferential cross-section of the resin retainer 4 be dc, as shown in FIG. 2, let the pocket diameter in the radial cross-section of the resin retainer 4 be dr, and let the diameter of the ball 3 be Da. The pocket diameters dc and dr are diameters based on the curved lines drawn by the resin surface portion forming the pocket 4a in the corresponding circumferential cross-section (see FIG. 1) or radial cross-section (see FIG. 2), and correspond to dimensions obtained by doubling the radius of curvature of the curved lines.

[0030] In order to provide a clearance between the resin retainer 4 and the ball 3, the relationship between the diameter Da of the ball 3 and the pocket diameters dc and dr (see FIGS. 1 and 2) is set to satisfy Da < dc and Da < dr.

[0031] In order to suppress the load on the resin retainer 4 due to the advance and retardation of the ball 3 generated during the rotation of this ball bearing, the relationship between the diameter Da of the ball 3 and the pocket diameter dc is set to satisfy 1.07Da ≦ dc.

[0032] In this numerical analysis model of the ball bearing, assuming the usage conditions of a general ball bearing, the amount of advance and retardation of the ball 3 generated when the ball 3 revolves in the circumferential direction under those usage conditions is calculated. Also, the ratio of the pocket diameter dc to the diameter Da of the ball 3 is set variously, and the size of the clearance of the pocket in the circumferential cross-section of the resin retainer 4 (refer to the pocket clearance δ shown in FIG. 1) is calculated for each ratio. A graph based on those calculation results is shown in FIG. 4.

[0033] The advance and delay of ball 3 (please refer to FIGS. 1 and 2 as appropriate below) occur because the revolution speed of ball 3 changes with the change in the contact angle between ball 3 and raceways 1a and 2a. The contact angle changes according to the magnitude of the load acting on the contact points between ball 3 and raceways 1a and 2a and the magnitude of the misalignment of the inclination between inner ring 1 and outer ring 2.

[0034] The usage conditions in the above numerical analysis are as follows: when the basic dynamic rated load of this ball bearing is C and the dynamic equivalent load is P, the value of (C / P) for the radial load is 0.17, the value of (C / P) for the axial load is 0.30, and the value of the misalignment of the relative inclination between inner ring 1 and outer ring 2 is 1 / 300 (mm / mm). The amount of advance and delay of ball 3 generated under these usage conditions was approximately 0.8 mm in the circumferential direction at the maximum on both the advancing side and the delaying side. The maximum value of the amount of advance and delay of ball 3 is shown by the horizontal broken line in FIG. 4.

[0035] When the amount of advance and delay of ball 3 is less than the clearance of the pocket in the circumferential cross-section of resin cage 4, the advanced ball 3 or the delayed ball 3 and the pillar portion 4c of resin cage 4 do not strongly press against each other, and no load on resin cage 4 due to the advance and delay of ball 3 occurs.

[0036] As can be read from FIG. 4, the size of the clearance of the pocket in the circumferential cross-section of resin cage 4 becomes equal to the amount of advance and delay of ball 3 when 1.07Da = dc, and becomes larger than the amount of advance and delay of ball 3 when 1.07Da < dc. Therefore, it can be understood that when 1.07Da ≤ dc is satisfied, it is effective in suppressing the load on resin cage 4 due to the advance and delay of ball 3, while when 1.07Da > dc is satisfied, such a load cannot be suppressed.

[0037] When the aforementioned radial load (C / P) value is less than 0.17, the axial load (C / P) value is less than 0.30, and the tilt misalignment value is less than 1 / 300 (mm / mm), the lead / lag amount of balls 3 will be less than the maximum value shown in Figure 4. Therefore, as long as this ball bearing is operated under conditions where the radial load (C / P) value is 0.17 or less, the axial load (C / P) value is 0.30 or less, and the relative tilt misalignment value between the inner ring and the outer ring is 1 / 300 (mm / mm) or less, no load will be generated on resin cage 4 due to lead / lag of balls 3.

[0038] In order to avoid interference between the resin cage 4 and the inner ring 1 and outer ring 2 by making the amount by which the resin cage 4 can freely move radially relative to the multiple balls 3 (hereinafter simply referred to as the "radial movement amount of the resin cage 4") smaller than the gaps δi, δo, the relationship between the diameter Da of the balls 3 and the pocket diameter dr is set to satisfy dr < 1.07 Da.

[0039] In the above-mentioned numerical analysis model, the ratio of the pocket diameter dr to the diameter Da of the balls 3 was set in various ways, and the radial movement of the resin cage 4 was calculated for each ratio. A graph based on the calculation results is shown in Fig. 5.

[0040] The amount of radial movement of the resin cage 4 is affected by the relative size between the pocket diameter dr and the diameter Da of the balls 3. As the pocket diameter dr increases relative to the diameter Da of the balls 3, the amount of radial movement of the resin cage 4 increases. If the amount of radial movement of the resin cage 4 is smaller than the gaps δi, δo, no interference will occur between the resin cage 4 and the inner ring 1 or outer ring 2. The dimensions of the gaps δi, δo are indicated by the horizontal dashed lines in Figure 5.

[0041] As can be read from FIG. 5, the radial movement amount of the resin cage 4 becomes equal to the clearances δi and δo when 1.07Da = dr, and becomes smaller than the clearances δi and δo when dr < 1.07Da. Therefore, when dr < 1.07Da is satisfied, interference between the resin cage 4 and the inner ring 1 and the outer ring 2 can be avoided, while when dr ≧ 1.07Da is satisfied, it can be seen that such interference cannot be avoided.

[0042] As described above, this ball bearing includes an inner ring 1, an outer ring 2, a plurality of balls 3 disposed between the inner ring 1 and the outer ring 2, and a resin cage 4 that houses the balls 3 in a plurality of pockets 4a that open on one axial side. In particular, when the pocket diameter in the circumferential cross-section of the resin cage 4 is dc, the pocket diameter in the radial cross-section of the resin cage 4 is dr, and the diameter of the ball 3 is Da, by satisfying Da < dr < 1.07Da ≦ dc, during the operation of this ball bearing, it is difficult for the clearance between the pockets to become insufficient in the circumferential direction with respect to the advance and retardation of the balls 3, and the clearance between the pockets is not too large in the radial direction with respect to the balls 3. Therefore, while suppressing the load on the crown-shaped resin cage 4 due to the advance and retardation of the balls 3, interference between the resin cage 4 and the race rings (inner ring 1, outer ring 2) can be avoided.

[0043] Further, in this ball bearing, when the basic dynamic rating load is C and the dynamic equivalent load is P, the value of (C / P) for the radial load is 0.17 or less, the value of (C / P) for the axial load is 0.30 or less, and the misalignment value of the relative inclination between the inner ring and the outer ring is 1 / 300 (mm / mm) or less. By operating under the use conditions that satisfy these, the advance and retardation of the balls 3 do not become larger than the clearance between the pockets, so that the load on the resin cage 4 due to the advance and retardation of the balls 3 can be prevented from occurring.

[0044] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0045] 1. Inner Circle 2 Outer ring 3 balls 4 Resin retainer 4a Pocket 4b Circular ring 4c Pillar Da ball diameter dc Pocket diameter in circumferential cross section of resin cage dr: Pocket diameter in radial cross section of resin cage

Claims

1. A ball bearing including an inner ring, an outer ring, a plurality of balls disposed between the inner ring and the outer ring, and a resin cage that houses the balls in a plurality of pockets that open to one axial side, A ball bearing characterized in that, when a pocket diameter at a circumferential cut surface of the resin cage is dc, a pocket diameter at a radial cut surface of the resin cage is dr, and a diameter of the ball is Da, Da < dr < 1.07Da ≦ dc is satisfied.

2. 2. A ball bearing according to claim 1, which is operated under operating conditions which satisfy the following: when the basic dynamic load rating is C and the dynamic equivalent load is P, the radial load (C / P) value is 0.17 or less, the axial load (C / P) value is 0.30 or less, and the relative inclination misalignment value between the inner ring and the outer ring is 1 / 300 (mm / mm) or less.

3. 3. The ball bearing according to claim 1, wherein the resin cage is made of a thermoplastic engineering plastic or a thermosetting engineering plastic.

4. 3. The ball bearing according to claim 1, wherein the resin cage is made of a fiber-reinforced resin.

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