Bearings and reducers

Abstract

The present invention provides a bearing that can further reduce the occurrence of skew in rolling elements, and a gearbox whose reliability is further improved by the bearing. [Solution] The bearing (100) comprises rolling elements (2) having a cylindrical surface and a cage (1) that holds a plurality of rolling elements around a central axis. The cage (1) includes a side circumferential portion that houses a plurality of rolling elements along the circumference of the central axis, annular plate-shaped end face portions (12a, 12b) extending radially from the axial ends of the side circumferential portion, and a reinforcing portion (13) disposed on the end face portion. The reinforcing portion (13) has projections (14e, 14f) that overlap with the trajectory surface of the rotation axis of the rolling element (2) and restrict the positions of both ends in the circumferential direction centered on the central axis of the rolling element.

Description

Technical Field

[0001] The present invention relates to a bearing and a speed reducer.

Background Art

[0002] Patent Document 1 discloses a structure for improving the strength of a cage of a needle bearing. The cage has a thick reinforcing portion on a part of a wall portion that regulates the positions of rolling elements from one side and the other side in a direction along the rotation axis.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even in the cage having the above-described reinforcing portion, there are cases where the suppressing effect on the skew of the rolling elements (a phenomenon of tilting about an axis extending in the radial direction of the bearing) is insufficient.

[0005] An object of the present invention is to provide a bearing capable of further reducing the occurrence of skew of rolling elements, and a speed reducer having improved reliability by the bearing.

Means for Solving the Problems

[0006] A bearing according to one aspect of the present invention is a bearing having rolling elements having a cylindrical surface and a cage that holds a plurality of the rolling elements around a central axis, where the cage includes a side peripheral portion in which a plurality of the rolling elements are housed along the periphery of the central axis, an annular plate-shaped end face portion extending radially from an axial end portion of the side peripheral portion, and a reinforcing portion disposed on the end face portion. The reinforcing portion has projections that overlap with the trajectory plane of the rotation axis of the rolling element and that restrict the positions of both ends in the circumferential direction with respect to the central axis of the rolling element.

[0007] Another embodiment of the present invention is a bearing, A bearing having rolling elements with cylindrical surfaces and a cage that holds a plurality of the rolling elements around a central axis, The retainer has a side circumferential portion in which a plurality of the rolling elements are housed along the circumference of the central axis, An annular plate-shaped end face portion extending radially from the axial end of the side circumference, The rolling element comprises a reinforcing portion arranged on the end face so as to overlap with the trajectory plane of the rotation axis of the rolling element, The axial end face of the rolling element has an outer portion that protrudes axially more than the inner circumference.

[0008] A gearbox according to one aspect of the present invention is The above bearing is incorporated. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a bearing that can further reduce the occurrence of skew in rolling elements, and a gearbox with improved reliability and durability as a result of the bearing. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partially fractured side view showing a bearing according to Embodiment 1 of the present invention. [Figure 2] This is a front view showing a part of the bearing in Figure 1. [Figure 3] This is a cross-sectional view along the line indicated by arrow AA in Figure 2. [Figure 4] Figure 2 shows a cross-sectional view along the line indicated by arrow BB. [Figure 5] Figure (A) shows the view in the direction of arrow C in Figure 1, and Figure (B) is a magnified view of a part C0 of the retainer in (A). [Figure 6] This is a partially fractured side view showing a bearing according to Embodiment 2 of the present invention. [Figure 7] Figure 6 shows (A) as seen in the direction of arrow C, and (B) is a magnified view of a part C1 of the rolling element in (A). [Figure 8] This is a cross-sectional view showing a speed reducer according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. In the following, the radial direction of bearings 100 and 100A will be simply referred to as "radial direction".

[0012] (Embodiment 1) Figure 1 is a partially broken side view showing a bearing of Embodiment 1 of the present invention. Figure 2 is a front view showing a part of the bearing of Embodiment 1. Figure 3 is a cross-sectional view along the line of arrow AA in Figure 2. Figure 4 is a cross-sectional view along the line of arrow BB in Figure 2. Figure 5 is a view (A) in the direction of arrow C in Figure 1, and an enlarged view (B) of a part C0 of the cage 1 shown in Figure 5(A). In Figure 1, only four rolling elements 2 are shown, but the rolling elements 2 are filled around the entire circumference with spacing between them.

[0013] The bearing 100 of Embodiment 1 includes a cylindrical rolling element 2 having a cylindrical surface and a cage 1 that holds a plurality of rolling elements 2. The bearing 100 is a cylindrical roller bearing or a needle roller bearing. The rolling element 2 may have any shape such as cylindrical or columnar as long as it has a cylindrical surface, and the material may be metal. The bearing 100 is positioned between an outer member having a cylindrical inner surface S1 (see FIG. 1) that contacts the plurality of rolling elements 2 from the outside and an inner member having a cylindrical outer surface S2 (see FIG. 1) that contacts the plurality of rolling elements 2 from the inside, and the outer member supports the inner member via the bearing 100 in a state where the first member and the second member are relatively rotatable about the central axis O1. Alternatively, the inner member supports the outer member via the bearing 100. The cage 1 holds the plurality of rolling elements 2 around the central axis O1 in a state where the outer member and the inner member are present. The central axis O1 means the axis of the rotation center of the inner member and the outer member that rotate relatively via the bearing 100. The central axis O1 may be a fixed axis or a moving axis.

[0014] In FIG. 1, an example in which the bearing 100 does not have an outer ring and an inner ring is shown, but the bearing 100 may include an outer ring, an inner ring, or both of them.

[0015] The cage 1 includes a side peripheral portion 11 around which the plurality of rolling elements 2 are accommodated. As shown in FIG. 2, the side peripheral portion 11 has a plurality of opening windows 11a arranged in the circumferential direction at intervals, and the plurality of rolling elements 2 are accommodated in the side peripheral portion 11 such that a part of one rolling element 2 fits into one opening window 11a. The opening window 11a is, for example, rectangular when viewed in the radial direction, larger than the rolling element 2 in the axial direction, and smaller than the diameter of the rolling element 2 in the circumferential direction.

[0016] Generally, to increase the power density of a gearbox incorporating a bearing 100, the filling density of the rolling elements 2 in the bearing 100 is sometimes increased. In this case, the frame portion 11b between two adjacent opening windows 11a becomes narrower. Furthermore, if skew occurs in the rolling elements 2, the tilted rolling elements 2 will come into contact with a part of the frame of the opening window 11a, causing stress to concentrate at the base of the frame portion 11b. Therefore, in conventional bearings, increasing the filling density of the rolling elements makes it difficult to ensure the strength of the cage.

[0017] The retainer 1 further includes annular plate-shaped end faces 12a and 12b (see Figures 1 to 4) that extend radially from the axial ends of the side circumference 11. Figure 3 shows a longitudinal cross-section of the end face 12a. The end faces 12a and 12b are provided on both the one and the other axial sides. The end faces 12a and 12b are arranged with a clearance between them in the axial direction of the rolling element 2.

[0018] Parts of the end faces 12a and 12b have reinforcing portions 13 that are thicker (specifically, axial thickness) than other parts of the retainer 1 (for example, the central part between the outer and inner ends of the retainer 1) (see Figures 1 and 4). As shown in Figure 1, the reinforcing portion 13 is strip-shaped when viewed through from the axial direction and extends in the circumferential direction. In Embodiment 1, the reinforcing portion 13 may be replaced by projections 14e and 14f, which will be described later. In that case, it is not necessary for the thickness to be increased along the entire circumference in the circumferential direction.

[0019] As shown in Figures 4 and 5, the reinforcing portion 13 has a plurality of protrusions 14e and 14f that project in the axial direction toward the side where the rolling element 2 is located. The protrusions 14e and 14f are positioned at a height that coincides with the trajectory plane of the rotation axis O2 of the rolling element 2. The rotation axis O2 corresponds to the central axis of the cylindrical surface of the rolling element 2. Height refers to the distance from the central axis O1 in the radial direction. Furthermore, when viewed from the axial direction, the protrusions 14e and 14f are positioned to coincide with both ends of the rolling element 2 in the circumferential direction of the bearing 100 (the parts facing the protrusions 14e and 14f in Figure 1).

[0020] With this arrangement, when skew occurs in the rolling element 2, the protrusions 14e and 14f abut against the circumferential end of the bearing 100 at the axial end face E2 of the rolling element 2, thereby restricting the position of the end. By restricting the position as described above, the skew angle of the rolling element 2 can be accurately reduced. In other words, the occurrence of large skew in the rolling element 2 can be greatly reduced. As a result, the rigidity of the bearing 100 is improved. Furthermore, since the stress concentration at the base of the frame portion 11b is reduced, the durability of the cage 1 is improved, and consequently, the durability of the bearing 100 is improved.

[0021] Furthermore, because the protrusions 14e and 14f are arranged as described above, the effect of reducing the skew angle can be obtained with almost no influence from dimensional errors of the retainer 1 and rolling elements 2, as well as assembly errors.

[0022] Here, the "end portion" to which the protrusions 14e and 14f abut refers to the outermost portion of the axial end face E2 of the rolling element 2, which is divided into three equal intervals from the rotation axis O2 to the outer circumference of the rolling element 2, and is located in a region where the distance from the central axis O1 is approximately the same as that of the rotation axis O2. The trajectory surface of the rotation axis O2 refers to the trajectory surface when the rotation axis O2 is rotated around the central axis O1. Alternatively, the trajectory surface of the rotation axis O2 may be rephrased as the trajectory surface of the rotation axis O2 of the rolling element 2 when the rolling element 2 is rolled against the inner member described above. Furthermore, the positions of the reinforcing portion 13 and the protrusions 14e and 14f described above refer to the positions when the retainer 1 is positioned so that its center coincides with the central axis O1. Since the retainer 1 is located around the rolling element 2 with a clearance in between, it will be displaced if an external force is applied. However, when the bearing 100 is in use, the lubricant causes the cage 1 to be positioned so that its center coincides with the central axis O1.

[0023] As shown in Figure 5(B), the projections 14e and 14f have rounded edges on the projection portions Pa1 and Pa2 and the base portions Pb1 and Pb2. The areas where the rounding is provided are the boundary portions between the high and low parts in the projection direction caused by the projection. Figure 5(B) shows the projection 14f, but the same applies to the projection 14e. The rounding corresponds to an r-shape that rounds off a convex corner and an r-shape that rounds off a concave corner. This rounding increases the fluidity of the lubricant (e.g., grease) around the projections 14e and 14f, and maintains high lubricity of the rolling elements 2 in the bearing 100. Note that the projections 14e and 14f may have rounding on at least one of the projection portion and the base portion, and even in that case, the fluidity of the lubricant can be increased compared to when there is no rounding.

[0024] As described above, according to the bearing 100 of Embodiment 1, the projections 14e and 14f of the cage 1, and the arrangement of the projections 14e and 14f, can significantly reduce the occurrence of large skew in the rolling elements 2. Therefore, the rigidity and durability of the bearing 100 can be improved. In addition, since the occurrence of large skew can be reduced, irregular forces applied to the frame portion 11b of the cage 1 are suppressed. Therefore, the frame portion 11b can be made thinner, and the filling rate of the rolling elements 2 can be increased.

[0025] Furthermore, according to the bearing 100 of this embodiment, the projections 14e and 14f have rounded edges on the projections and base portions. This prevents lubricant from accumulating on the projections 14e and 14f and the surrounding corner portions. Thus, the lubricity of the bearing 100 is improved, and the durability of the bearing 100 is improved.

[0026] (Embodiment 2) Figure 6 is a partially broken side view showing a bearing according to Embodiment 2 of the present invention. Figure 7(A) is a view in the direction of arrow C in Figure 6. Figure 7(B) is an enlarged view of a portion C1 of the rolling element 2 shown in Figure 7(A). In Figure 6, only four rolling elements 2 are shown, but the rolling elements 2 are filled around the entire circumference with spacing between them.

[0027] The bearing 100A of Embodiment 2 differs from Embodiment 1 in that the protrusions 14e and 14f of Embodiment 1 are omitted, while the shape of the axial end face E2 of the rolling element 2 is different; however, the other configurations are the same as those of Embodiment 1.

[0028] The retainer 1 has reinforcing portions 13 on its end faces 12a and 12b that have increased thickness (specifically, axial thickness). More specifically, the reinforcing portions 13 have increased axial thickness compared to other parts of the retainer 1 (for example, the central part between the outer and inner ends of the retainer 1). The reinforcing portions 13 are located at a height that coincides with the trajectory plane of the rotation axis O2 of the rolling element 2. Height refers to the distance from the central axis O1 in the radial direction. The reinforcing portions 13 may have increased thickness around the entire circumference in the circumferential direction compared to other parts of the end faces 12a and 12b.

[0029] As shown in Figures 6 and 7, the axial end face E2 of the rolling element 2 has an outer peripheral portion 22 that protrudes axially more than the inner peripheral portion. That is, the amount of axial protrusion of the outer peripheral portion 22 is greater than that of the central portion of the axial end face E2. The outer peripheral portion 22 corresponds to the outermost portion of the radius r, which is divided into three equal intervals from the axis of rotation O2 to the outer peripheral end of the rolling element 2 when viewed in the axial direction (see Figure 7).

[0030] The protruding outer circumference 22 of the rolling element 2 and the reinforcing portion 13 of the cage 1 cause the reinforcing portion 13 of the cage 1 to contact the circumferential end of the axial end face E2 of the rolling element 2 (i.e., the circumferential end of the bearing 100A) when skew occurs in the rolling element 2, thereby restricting the position of that end. By restricting the position as described above, the skew angle of the rolling element 2 can be accurately reduced. In other words, the occurrence of large skew in the rolling element 2 can be greatly reduced. Thus, the rigidity and durability of the bearing 100 can be improved. Furthermore, by arranging the protruding outer circumference 22 of the axial end face E2 of the rolling element 2 as described above, the effect of reducing the skew angle can be obtained with almost no influence from dimensional errors of the cage 1 and rolling element 2, as well as assembly errors.

[0031] As shown in Figure 7(B), the protruding outer circumference 22 of the rolling element 2 is provided with rounded edges on the protruding portion P1 and the base portion P2. The areas where the edges are rounded are the boundary portions between the high and low parts in the direction of protrusion caused by the protrusion. The rounding corresponds to an r-shape that rounds off a convex corner and an r-shape that rounds off a concave corner. This rounding increases the fluidity of the lubricant (e.g., grease) around the protruding outer circumference 22, thereby maintaining the high lubricity of the rolling element 2. Note that the outer circumference 22 may have rounding on at least one of the protruding portion and the base portion, and even in this case, the fluidity of the lubricant can be increased compared to when there is no rounding.

[0032] As described above, the bearing 100A of Embodiment 2 significantly reduces the occurrence of large skew in the rolling elements 2 due to the reinforcing portion 13 of the cage 1 and the outer peripheral portion 22 that protrudes axially in the rolling elements 2. Therefore, the rigidity and durability of the bearing 100 can be improved. In addition, since the occurrence of large skew can be reduced, irregular forces applied to the frame portion 11b of the cage 1 are suppressed. Therefore, the frame portion 11b can be made thinner and the filling rate of the rolling elements 2 can be increased.

[0033] Furthermore, according to the bearing 100A of Embodiment 2, the outer peripheral portion 22 that protrudes axially from the rolling element 2 is provided with rounded edges at the protruding portion and the base portion. This prevents the lubricant from accumulating in the uneven portions of the outer peripheral portion 22. Thus, the lubricity of the bearing 100A is improved, and the durability of the bearing 100A can be improved.

[0034] In addition, the cage 1 having the protrusions 14e and 14f of Embodiment 1 may also be used in the bearing 100A of Embodiment 2. With this configuration, when skew occurs in the rolling element 2, the protrusions 14e and 14f of the cage 1 come into contact with the outer peripheral portion 22 of the rolling element 2 that protrudes in the axial direction, thereby more effectively reducing the skew angle of the rolling element 2.

[0035] (reducer) Figure 8 is a cross-sectional view showing a speed reducer according to an embodiment of the present invention. In this embodiment, the speed reducer 50 uses the bearings 100 of Embodiment 1 as bearings (for example, eccentric bearing 57A and eccentric shaft bearing 57B) that support the rotating part. Some or all of the bearings 100 may be replaced with the bearing 100A of Embodiment 2. With this configuration, the rotating part is supported via bearings 57A and 57B with less skew of the rolling elements 2, thereby improving the rigidity and durability of the speed reducer 50.

[0036] More specifically, the gearbox 50 of this embodiment is a distribution-type eccentric oscillating gearbox, comprising external gears 52A and 52B, an eccentric shaft (crankshaft) 51 that oscillates the external gears 52A and 52B, an eccentric shaft bearing (corresponding to a first bearing) 57B that supports the eccentric shaft 51, and an eccentric bearing (corresponding to a second bearing) 57A located between the external gears 52A and 52B and the eccentric shaft 51. The bearing 100 of Embodiment 1 is applied to both the eccentric shaft bearing 57B and the eccentric bearing 57A. The eccentric bodies 51a and 51b correspond to inner members having cylindrical outer surfaces that contact the plurality of rolling elements 2 of the eccentric bearing 57A from the inside. The external gears 52A and 52B correspond to outer members having cylindrical inner surfaces that contact the plurality of rolling elements 2 of the eccentric bearing 57A from the outside. The shaft portion of the eccentric shaft 51 corresponds to an inner member having a cylindrical outer surface that contacts the plurality of rolling elements 2 of the eccentric shaft bearing 57B from the inside. Part of the output shaft 54 ​​and part of the support plate 541 correspond to an outer member having a cylindrical inner surface that contacts the plurality of rolling elements 2 of the eccentric shaft bearing 57B from the outside.

[0037] As shown in Figure 8, the speed reducer 50, which is a distribution-type eccentric oscillating speed reducer, has an eccentric shaft 51 having eccentric bodies 51a and 51b, a first external gear 52A through which the eccentric body 51a passes through a through hole offset from the axis (central axis Ax), and a second external gear 52B through which the eccentric body 51b passes through a through hole offset from the axis.

[0038] The eccentric shaft 51 has an eccentric shaft gear 53 that meshes with the output shaft of a motor (not shown), and rotation is input from the input shaft via the eccentric shaft gear 53. Through holes in the external gears 52A and 52B are provided at multiple locations (for example, three locations) in the circumferential direction, and multiple eccentric shafts 51 pass through them. The eccentric bodies 51a and 51b are rotatably positioned in the through holes of the external gears 52A and 52B via eccentric bearings 57A.

[0039] Furthermore, the reduction gear 50 comprises an output shaft (carrier body) 54, a support plate 541 fixed to the opposite side of the output shaft 54, and a housing 55 having an internal gear 55g that meshes with external gears 52A and 52B. The internal gear 55g has a plurality of external pins that function as internal teeth. Eccentric shaft bearings 57B are positioned between the eccentric shaft 51 and the output shaft 54, and between the eccentric shaft 51 and the support plate 541, respectively. The housing 55 rotatably supports the output shaft 54 ​​and the support plate 541 via main bearings 58a and 58b. The output shaft 54 ​​is fixed to a driven member (not shown).

[0040] In this configuration, when rotational motion is transmitted to the eccentric shaft 51 via the eccentric shaft gear 53 by the motor drive, the eccentric bodies 51a and 51b rotate, causing the external gears 52A and 52B to eccentrically oscillate. This eccentric oscillation changes the meshing position between the external gears 52A and 52B and the internal gear 55g in the circumferential direction, and because the number of teeth on each gear is different, the external gears 52A and 52B rotate (spin). The rotation component of the external gears 52A and 52B is then output to the driven member via the output shaft 54.

[0041] In the reduction gear 50 of this embodiment, the load applied between the external gears 52A, 52B and the eccentric shaft 51, as well as the load applied between the eccentric shaft 51 and the housing 55, can cause a force that generates skew in the rolling elements 2 of the eccentric bearing 57A and the bearing for the eccentric shaft 57B. However, by applying the bearing 100 of Embodiment 1 to the bearings 57A and 57B, the skew generated in the rolling elements 2 of the eccentric bearing 57A and the bearing for the eccentric shaft 57B can be suppressed, thereby improving the rigidity and durability of the reduction gear 50. The same applies if the bearing 100A of Embodiment 2 is applied instead of the bearing 100 of Embodiment 1.

[0042] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiments, a so-called distribution-type eccentric oscillating reduction gear in which a shaft having an eccentric body is arranged offset from the axis of the gear device was shown as a reduction gear into which the bearing according to the present invention is incorporated. However, this reduction gear may be applied to a so-called cylindrical flexible meshing gear device, a so-called cup-type or top-hat-type flexible meshing gear device, a center-crank type eccentric oscillating reduction gear in which a shaft having an eccentric body is arranged in the center of the gear device, or a simple planetary gear device. Furthermore, the reduction gear into which the bearing according to the present invention is incorporated may be a worm-type reduction gear or a gear train type reduction gear, or any other type of reduction gear. In these reduction gears, the bearing according to the present invention may be applied to support various rotating bodies. Furthermore, although the above embodiments showed an example in which the bearing according to the present invention is incorporated into a reduction gear, it is not limited to this, and the bearing according to the present invention may be used as a configuration to support various rotating bodies. In addition, the details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0043] 100, 100A bearings O1 center axis 1 Cage 11 Side circumference 11a Opening window 11b Frame 12a, 12b end section 13 Reinforcement section 14e, 14f protrusion 2 Rolling elements 22 Outer periphery E2 Axial end face O2 rotation axis 50 reducer 51 Eccentric axis 51a, 51b eccentric body 52A, 52B External gears 53 Eccentric shaft gear 54 Output shaft 57A Eccentric bearing (bearing) 57B Eccentric shaft bearing (bearing)

Claims

1. A bearing having rolling elements with cylindrical surfaces and a cage that holds a plurality of the rolling elements around a central axis, The retainer has a side circumferential portion in which a plurality of the rolling elements are housed along the circumference of the central axis, An annular plate-shaped end face portion extending radially from the axial end of the side circumference, The end face portion comprises a reinforcing portion, The reinforcing portion has projections that overlap with the trajectory plane of the rotation axis of the rolling element and that restrict the positions of both ends in the circumferential direction with respect to the central axis of the rolling element. Bearing.

2. The projection portion and the base portion of the projection have a rounded shape. The bearing according to claim 1.

3. The axial end face of the rolling element has an outer circumferential portion that protrudes axially more than the inner circumferential side. The bearing according to claim 1 or claim 2.

4. A bearing having rolling elements with cylindrical surfaces and a cage that holds a plurality of the rolling elements around a central axis, The retainer has a side circumferential portion in which a plurality of the rolling elements are housed along the circumference of the central axis, An annular plate-shaped end face portion extending radially from the axial end of the side circumference, The rolling element comprises a reinforcing portion arranged on the end face so as to overlap with the trajectory plane of the rotation axis of the rolling element, The axial end face of the rolling element has an outer circumferential portion that protrudes axially more than the inner circumferential side. Bearing.

5. A gearbox incorporating the bearing described in claim 1 or claim 4.

6. The aforementioned reduction gear is an eccentric oscillation type reduction gear, The device comprises an external gear, an eccentric shaft that pivots the external gear, a first bearing that supports the eccentric shaft, and a second bearing located between the external gear and the eccentric shaft. Each of the first bearing and the second bearing is the bearing, The gearbox according to claim 5.

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