JP2019031990A - Ball bearing - Google Patents

Abstract

The rotational torque of a grease lubricated ball bearing having a crown-shaped cage is further reduced. A pocket portion 41 of a cage 40 has edges 41a and 41b capable of scraping grease Gr from the ball 30 by line contact with the ball 30 held in the pocket portion 41. The retainer 40 is a grease reservoir 45 having a shape recessed from the inner diameter d of the retainer 40 toward the outer diameter side at a position on the other side in the axial direction with respect to the connecting portion 42 continuous in the circumferential direction across the adjacent pocket portions 41. And a protruding wall portion 46 that prevents the grease Gr from scattering at a position between the claw portions 43 and 44 adjacent on the one side in the axial direction with respect to the connecting portion 42 and a position on the outer diameter side of the cage 40. Based on the edges 41a and 41b of the pocket portion 41, the grease reservoir 45 and the protruding wall portion 46, the stirring resistance of the grease Gr is synergistically suppressed. [Selection] Figure 1

Description

  The present invention relates to a ball bearing including a crown-shaped cage and having grease sealed between an inner ring and an outer ring.

  Conventionally, in ball bearings, so-called crown-shaped cages are used as cages that equally distribute a plurality of balls interposed between an inner ring and an outer ring in the circumferential direction. Here, the crown-shaped cage means a pocket portion having a shape opened to the inner diameter side, outer diameter side and one axial side of the cage, and a connecting portion continuous in the circumferential direction between pocket portions adjacent to each other in the circumferential direction. And a pair of claw portions protruding to one side in the axial direction so as to form both end portions on one side in the axial direction of the pocket portion from the connecting portions on both sides adjacent to the pocket portion. Such a crown-shaped cage holds balls in the pocket by moving the cage claw side toward the ball in the axial direction with a plurality of balls arranged between the inner ring and the outer ring. It is possible to make it.

  In a grease lubricated ball bearing, a predetermined amount of grease is sealed between an inner ring and an outer ring. The grease lubricated type is easy to handle, simplifies the design of the sealing device, does not require resupply, and has excellent maintainability. On the other hand, the grease lubrication type is known to increase frictional torque and generate heat due to the stirring resistance of grease stirred inside the bearing when the bearing rotates. As conventional techniques for reducing the friction torque, there are those disclosed in Patent Documents 1 and 2.

  The friction torque reduction measure disclosed in Patent Document 1 improves lubrication characteristics by improving grease. When a semi-solid lubricant such as grease is used, even if the grease is improved, the rotational torque of the bearing becomes larger than that of the oil lubricated type because of the stirring resistance caused by the lubricant.

  Although it is possible to reduce the rotational torque by optimizing the type of grease and reducing the amount of grease, these torque reduction measures lead to an increase in manufacturing costs and a decrease in bearing life. There is a need for means for reducing rotational torque without greatly changing the type and amount of grease, etc. from existing products.

  In the ball bearing disclosed in Patent Document 2, the rotational torque is reduced by making the crown-shaped cage into a special shape. That is, in the case of an ordinary crown-shaped cage, the pocket portion holds the ball only with a concave surface having a curvature smaller than the curvature of the ball. When the bearing rotates, the ball contacts the vicinity of the center of the radial thickness of the concave surface. In this case, the grease adhering to the ball during the rotation of the bearing moves back and forth between the concave surface and the ball and is constantly stirred. On the other hand, the pocket part disclosed by patent document 2 has an edge which can scrape away grease from the said ball | bowl by the line contact with the ball | bowl currently hold | maintained here. In this case, when the bearing rotates, the edge of the pocket portion scrapes off the grease adhering to the balls, so that the stirring resistance can be reduced.

Japanese Patent No. 3330755 JP 2012-31914 A

  However, as in Patent Document 2, even if a crown-shaped cage that scrapes grease from the ball by the edge of the pocket is adopted, if the amount of grease filled increases, the grease supply to the ball exceeds the amount of grease scraped. The amount increases, and a decrease in stirring resistance cannot be expected.

  In view of the above background, the problem to be solved by the present invention is to further reduce the rotational torque of a grease lubricated ball bearing having a crown-shaped cage.

  In order to achieve the above object, the present invention comprises an inner ring, an outer ring, a plurality of balls interposed between the inner ring and the outer ring, and a cage for holding the plurality of balls, Grease is sealed between the outer ring, and the cage is adjacent to the plurality of pocket portions having a shape opened on the inner diameter side, outer diameter side, and one axial side of the cage, in the circumferential direction. It protruded to the one side of the axial direction so as to form both ends on the one side in the axial direction of the pocket part from the connecting part that is continuous in the circumferential direction across the pocket parts and the joint part on both sides adjacent to the pocket part. A pair of claw portions, and the pocket portion has an edge capable of scraping the grease from the ball by line contact with the ball held in the pocket portion, and the retainer Of the cage at a position on the other axial side with respect to the A grease reservoir that is recessed from the diameter to the outer diameter side, and the grease is prevented from scattering at a position between the claw portions adjacent on one side in the axial direction with respect to the connecting portion and a position on the outer diameter side of the cage. The ball bearing further includes a projecting wall portion.

  According to the above configuration, when the ball bearing is rotated, the grease is scraped off from the ball by the edge of the pocket portion of the rotating cage, so that the stirring of the grease by the ball is suppressed. In addition, on the other side in the axial direction with respect to the connecting portion of the rotating cage, the grease is held by the grease reservoir and is rotated together. For this reason, the flow of grease inside the bearing is suppressed, the supply of grease to the balls is suppressed, and the stirring of the grease is further suppressed. In addition, on one side in the axial direction relative to the joint of the rotating cage, the grease is prevented from being scattered by the protruding wall portion located between the claws that cannot be received by the grease reservoir, and the grease is Therefore, the flow of grease inside the bearing is suppressed, and the agitation of grease is further suppressed. The rotational torque of the ball bearing is further reduced by the synergistic effect of the agitation suppression action of grease based on the edge of the pocket portion, the grease reservoir and the protruding wall portion.

  For example, the protruding wall portion of the cage is continuous in the circumferential direction between adjacent claw portions, and protrudes from the connecting portion to one axial side. If it does in this way, grease can be held with a projection wall part, both the nail | claw parts adjacent to this, and a connection part.

  For example, the protruding wall portion of the cage protrudes from the connecting portion to the one side in the axial direction at a position away from each of the adjacent claw portions in the circumferential direction. If it does in this way, it can prevent that the elastic deformation of a nail | claw part is inhibited by a protruding wall part.

  For example, the retainer extends in the circumferential direction from the first protruding wall portion that extends in the circumferential direction from one of the adjacent claw portions, and the other opposite to the one of the adjacent claw portions. A second protruding wall portion. If it does in this way, grease can be held by each projection wall part, a claw part adjacent to this, and a joint part.

  For example, when a virtual imaginary straight line passing through the center of the pocket portion is a pocket central axis, the edges of the pocket portion are both ends around the pocket central axis on the inner diameter side and the outer diameter side of the cage, respectively. It is formed over. If it does in this way, even if a ball contacts with respect to a pocket part from which direction, grease can be scraped off by an edge.

  In the vicinity of the virtual axial plane including the center of the pocket portion, the thickness of the cage portion becomes thin, and the thickness here greatly affects the centrifugal strength of the cage. If the edge that scrapes off the grease from the ball is disposed on the position, it must be formed in a deep concave shape that cannot contact the ball except for the edge, and it is difficult to ensure the thickness at the position. In order to obtain the centrifugal strength of the cage, the thickness of the cage portion in the vicinity of the virtual axial plane including the center of the pocket portion may be ensured by the device of the shape of the pocket portion.

  Specifically, the pocket portion has a bottom surface that can contact the ball at a position on a virtual axial plane including the center of the pocket portion. When the bottom surface having a shape capable of contacting with the ball is disposed on the position, the thickness here is increased and the centrifugal strength of the cage can be easily obtained.

  For example, the bottom surface of the pocket portion has a shape that can come into contact with the ball on a radial position having the same diameter as the center of the pocket portion. Since the pocket portion is a portion that is recessed toward the other side in the axial direction on the position, it is preferable to secure the wall thickness by arranging the bottom surface at the position.

  For example, when a radial virtual straight line passing through the center of the pocket portion is a pocket central axis and the virtual axial plane is at a 0 ° position around the pocket central axis, the bottom surface of the pocket portion is the pocket center It is formed only within the range of −30 ° to 30 ° around the axis. When the bottom surface is arranged only in the angular range, the edge for grease scraping can be arranged in a wide range and the stirring resistance can be reduced while obtaining the centrifugal strength of the cage.

  For example, the bottom surface of the pocket portion is formed on the inner diameter side of the cage, and the edge of the pocket portion is formed between both ends around the pocket central axis on the outer diameter side of the cage. Has been. In this way, the thickness of the cage portion is increased by the bottom surface on the inner diameter side of the cage, whereas on the outer diameter side of the cage, grease is scraped off at the edge regardless of which direction the ball contacts. Can do.

  For example, the bottom surface of the pocket portion has a concave shape with a curvature smaller than the curvature of the ball. Such a bottom can allow contact with the ball and increase the thickness of the cage portion.

  The centrifugal strength of the cage may be improved by contriving the shape of the side surface of the cage on the other side in the axial direction that is the back surface with respect to the pocket portion.

  Specifically, when the virtual axial plane including the center of the pocket portion is at a 0 ° position around the pocket central axis, the cage is −30 ° around the pocket central axis of the pocket portion. A portion located on the other side in the axial direction with respect to the range of ˜30 ° has a width surface portion along the radial direction. If it does in this way, since the site | part which becomes a back will become the width | variety surface part along radial direction with respect to the range where it is difficult to ensure the thickness of a cage | basket part, the thickness stealing dented in the axial direction in this range is eliminated, The centrifugal strength of can be improved.

  For example, the edge of the pocket portion is formed of an edge of a concave curved surface having a curvature larger than the curvature of the ball. Since such a curved surface contacts the ball only at the edge, it becomes an edge for scraping off the grease from the ball.

  For example, the amount of grease filled is 100% or less of the static space volume inside the bearing. If the amount of grease filled exceeds 100% of the static space volume, it is difficult to suppress the grease flow at the grease reservoir or the protruding wall, so it is preferably 100% or less. When the volume of the static space inside the bearing is 75% or less, the grease flow can be more suitably suppressed by the grease reservoir and the protruding wall portion. From the viewpoint of bearing life, it is preferable that the amount of grease enclosed be 75 to 100%.

  For example, the cage is made of a synthetic resin. Considering the lubrication between the pocket edge and the ball, the complexity of the shape of the cage and the weight reduction of the cage, if synthetic resin is used as the cage material, the ball at the pocket edge In addition, it is difficult to form a cage shape having a grease reservoir or a protruding wall portion, and the cage can be reduced in weight.

  According to the present invention, by adopting the above-described configuration, the grease agitating resistance is synergistically suppressed by the action of the scraping edge of the pocket portion, the grease reservoir and the protruding wall portion, and a grease lubricated ball having a crown-shaped cage is provided. The rotational torque of the bearing can be further reduced.

Sectional drawing which shows the ball bearing which concerns on 1st embodiment of this invention The perspective view which shows the external appearance of the holder | retainer of FIG. The partial expanded sectional view which shows the radial direction cross section of the pocket part of the holder | retainer of FIG. The partial expanded sectional view which shows the circumferential direction cross section of the pocket part of the holder | retainer of FIG. The graph which shows the test result of the Example corresponding to 1st embodiment, and a comparative example The graph which shows another test result of the Example corresponding to 1st embodiment, and a comparative example The partial expansion perspective view which shows the external appearance of the holder | retainer concerning 2nd embodiment of this invention The partial expansion perspective view which shows the external appearance of the holder | retainer which concerns on 3rd embodiment of this invention The partial expansion perspective view which shows the external appearance of the holder | retainer which concerns on 4th embodiment of this invention The partial expanded sectional view which shows the circumferential direction cross section of the pocket part of FIG. The partial expansion perspective view which shows the external appearance of the holder | retainer which concerns on 5th embodiment of this invention The schematic diagram which shows the shape of the circumferential cross section of the pocket part of FIG. The schematic diagram which shows the relationship between the shape of the radial cross section on the 0 degree position of the pocket part of FIG. The partial expansion perspective view which shows the external appearance of the holder | retainer which concerns on 6th embodiment of this invention The schematic diagram which shows the shape of the circumferential cross section of the pocket part of FIG. Schematic diagram showing the relationship between the shape of the cross section in the radial direction on the 0 ° position of the pocket portion of FIG.

  As an example of this invention, the ball bearing which concerns on 1st embodiment is demonstrated based on FIGS. As shown in FIGS. 1 and 2, the ball bearing includes an inner ring 10, an outer ring 20, a plurality of balls 30 interposed between the inner ring 10 and the outer ring 20, and a cage that holds the plurality of balls 30. 40 and a sealing member 50. Between the outer periphery of the inner ring 10 and the inner periphery of the outer ring 20, grease Gr (the grease is shown in a dot pattern in FIG. 1) is enclosed.

  Here, the direction along the bearing central axis (not shown), which is the central axis in design of this ball bearing, is referred to as “axial direction”. It can be said that the bearing center axis is an ideal rotation center in the relative rotation among the inner ring 10, the outer ring 20, and the cage 40. The axial direction corresponds to the left-right direction in FIG. One direction along the axial direction is referred to as “one axial direction”. One of the axial directions corresponds to the right direction in FIG. In addition, the direction opposite to one in the axial direction is referred to as “the other in the axial direction”. The other axial direction corresponds to the left direction in FIG. The radial direction perpendicular to the bearing central axis is referred to as “radial direction”. The radial direction corresponds to the vertical direction in FIG. A direction along the circumference around the bearing central axis is referred to as a “circumferential direction”. A virtual plane including the bearing central axis is referred to as a “virtual axial plane”. A virtual plane orthogonal to the bearing central axis is referred to as a “virtual radial plane”.

  The inner ring 10 and the outer ring 20 are each formed of an annular member having an inner periphery and an outer periphery. The outer periphery of the inner ring 10 has a raceway groove 11 that is continuous with the entire circumference in the circumferential direction. The inner circumference of the outer ring 20 has a raceway groove 21 that is continuous with the entire circumference in the circumferential direction.

  The plurality of balls 30 are interposed between the raceway grooves 11 of the inner ring 10 and the raceway grooves 21 of the outer ring 20. In FIG. 1, the contact angle between the ball 30 and the raceway grooves 11 and 21 is 90 °.

  As shown in FIGS. 1 and 2, the retainer 40 is a so-called crown-shaped retainer. That is, the cage 40 includes a pocket portion 41 having a shape opened to the inner diameter side, the outer diameter side, and the one axial side of the cage 40, and a connecting portion 42 that is continuous in the circumferential direction between adjacent pocket portions 41. The pair of claw portions 43 and 44 project from one side in the axial direction so as to form both end portions on one side in the axial direction of the pocket portion 41 from the connecting portions 42 on both sides adjacent to the pocket portion 41.

  The pocket portion 41 includes a cage surface portion that forms a pocket that is a space for accommodating the balls 30. Both end portions on one side in the axial direction of the pocket portion 41 consist of circumferentially opposed surfaces of the pair of claw portions 43 and 44, and the circumferential direction is smaller than the ball diameter of the ball 30 on the side surface on one side in the axial direction of the cage 40. A wide opening is formed. The connecting portion 42 extends in the circumferential direction at an intermediate position in the axial direction of the cage 40.

  As shown in FIG. 1, with a plurality of balls 30 disposed between the raceway grooves 11 of the inner ring 10 and the raceway grooves 21 of the outer ring 20, the claw portions 43 and 44 side of the cage 40 are directed toward the balls 30. By moving in the direction, the pair of claw parts 43, 44 are pressed against the ball 30 to cause elastic deformation of the claw parts 43, 44 in the direction of widening the opening width between the pair of claw parts 43, 44. When the cage 40 is moved in the axial direction until the claw portions 43 and 44 are elastically restored, the ball 30 can be held in the pocket portion 41.

  The entire cage 40 is made of a single annular member made of synthetic resin. Examples of the synthetic resin include PA46 (polyamide 46), PA66 (polyamide 66), PEEK (polyetheretherketone), and the like. The synthetic resin may be fiber reinforced.

  A gap between the outer periphery of the inner ring 10 and the inner periphery of the outer ring 20 is sealed by a pair of sealing members 50. As the sealing member 50, a contact-type seal member that is attached to the outer ring 20 and slides in the circumferential direction with respect to the outer periphery of the inner ring 10 is illustrated. However, a shield plate may be employed.

  When the ball bearing rotates, in a space surrounded by the outer periphery of the inner ring 10, the inner periphery of the outer ring 20, and the pair of sealing members 50 (inside the bearing sealed by the pair of sealing members 50), the cage 40 is It is driven by a ball 30 that revolves between the raceway grooves 11 and 21.

  The amount of grease Gr enclosed is 75 to 100% of the static space volume inside the bearing. Here, the static space volume inside the bearing means the volume of the space through which the ball 30 and the cage 40 do not pass during bearing rotation in the space volume surrounded by the pair of sealing members 50 and the outer periphery of the inner ring 10 and the inner periphery of the outer ring 20. I mean.

  During the rotation of the ball bearing, the grease Gr present in the space between the raceway groove 11 of the inner ring 10 and the raceway groove 21 of the outer ring 20 is agitated by the ball 30 and the cage 40. The cage 40 has a special shape for reducing the amount of grease Gr stirred by the balls 30 and suppressing the flow of the grease Gr inside the bearing. The details will be described below.

  Here, as shown in FIG. 3, the center of each ball 30 interposed between the raceway groove 11 of the inner ring 10 and the raceway groove 11 of the outer ring 20 arranged concentrically with the bearing center axis is exactly the same virtual circumference (pitch The position of the center of the ball 30 in a state of being evenly spaced in the circumferential direction on the circle PC) is referred to as “the center O of the pocket portion 41”. The radial virtual straight line passing through the center O is referred to as “pocket center axis Cp”. FIG. 3 shows a cross section when the cage 40 is cut along a virtual radial plane including the pocket center axis Cp and the vicinity of the pocket portion 41 is viewed in the axial direction.

  The pocket portion 41 has a mirror image symmetrical shape with a virtual axial plane Pa passing through the center O as a mirror surface. FIG. 4 shows a cross section when the cage 40 is cut by a virtual cylindrical surface passing through the center O of the pocket portion 41 and concentric with the bearing central axis, and the vicinity of the pocket portion 41 is viewed from the pocket central axis Cp direction. As shown in FIGS. 2 to 4, the pocket portion 41 forms an opening directed in the radial direction on the inner diameter side of the cage 40. The edge 41a of the opening has an arc shape along the circumferential direction around the pocket central axis Cp. Further, the pocket portion 41 forms an opening directed in the radial direction on the outer diameter side of the cage 40. The edge 41b of the opening also has an arc shape along the circumferential direction around the pocket central axis Cp. Moreover, the pocket part 41 forms the opening which turned to the axial direction one side between the pair of claw parts 43 and 44. The edge of this opening consists of a pair of edges 41c connecting the edges 41a and 41b. The pair of edges 41 c have an arc shape along a circumferential direction around an imaginary straight line (not shown) passing through the center O of the pocket portion 41. Both ends of the pocket portion 41 around the pocket central axis Cp are on a pair of edges 41c.

  As shown in FIG. 3, the pocket portion 41 is formed of a concave curved surface having a curvature larger than the curvature of the ball 30 held in the pocket portion 41. The pocket portion 41 includes a pocket center axis Cp and an arbitrary virtual plane that intersects with the pocket portion 41, and covers the entire radial thickness of the pocket portion 41 (edges that are both ends of the radial thickness of the pocket portion 41). 41a and 41b) and has a cross-sectional shape recessed from the edges 41a and 41b in a direction away from the ball 30 with a curvature larger than the curvature of the surface of the ball 30. For this reason, on the virtual plane, the pocket portion 41 can contact the ball 30 only by the edges 41a and 41b.

  As shown in FIGS. 2 and 3, the edges 41a and 41b of the pocket portions 41 are formed in series between both ends (a pair of edges 41c) around the pocket center axis Cp. The ball 30 can be in line contact with the ball 30 from any direction orthogonal to the ball 30. That is, the pocket portion 41 has edges 41 a and 41 b that can scrape the grease Gr from the ball 30 by line contact with the ball 30 held in the pocket portion 41.

  As shown in FIGS. 1 and 2, the connecting portion 42 of the cage 40 is continuous in the circumferential direction across the roots of the adjacent claw portions 43 and 44 and has a planar side surface along the radial direction. .

  The cage 40 has a grease reservoir 45 having a shape recessed from the inner diameter d of the cage 40 toward the outer diameter side at a position on the other axial side with respect to the connecting portion 42. The grease reservoir 45 has a shape opened toward the other side in the axial direction and radially inward. The grease reservoir 45 having such a shape does not cause an undercut when the cage 40 is formed by a two-part mold in the axial direction.

  The axial depth of the grease reservoir 45 is set to be larger than half of the axial width of the cage 40. The radial depth of the grease reservoir 45 is set to be larger than half of the radial thickness of the cage 40. Both ends in the circumferential direction of the grease reservoir 45 are located on the other side in the axial direction with respect to the claw portions 43 and 44 on the same side.

  Here, the axial width of the cage 40 is a virtual radial plane (not shown) including the end located on the most axial side of the cage 40 and a virtual including the end located on the other side in the axial direction. The distance between two surfaces of a radial plane (not shown). The radial thickness of the cage 40 includes a virtual cylindrical surface (not shown) concentric with the bearing central axis and inscribed in the cage 40, and a virtual cylindrical surface concentric with the bearing central axis and circumscribed in the cage 40 (illustrated). It means the distance between the two surfaces.

  When the grease Gr is sealed between the outer periphery of the inner ring 10 and the inner periphery of the outer ring 20 in a state where the retainer 40 holds the plurality of balls 30, a part of the sealed grease Gr adheres to the grease reservoir 45. Since the adhered grease Gr is held in the grease reservoir 45 from the beginning of the operation of the ball bearing, it is rotated by the cage 40. When the bearing rotates, the grease Gr that is not held in the cage 40 and is not positioned in the stationary space is caused to flow inside the bearing by the revolution of the ball 30 or the rotation of the cage 40. This flowing grease Gr tends to flow from the inner diameter side to the outer diameter side of the cage 40 by the action of centrifugal force. A part of the flowing grease Gr is held in the grease reservoir 45 and is rotated around the cage 40.

  Furthermore, the retainer 40 has a protruding wall portion 46 that prevents the grease Gr from being scattered at a position between the claw portions 43 and 44 adjacent to each other on one side in the axial direction with respect to the connecting portion 42 and a position on the outer diameter side of the retainer 40. Have.

  The protruding wall portion 46 is continuous in the circumferential direction between adjacent claw portions 43 and 44, and protrudes from the connecting portion 42 to the one side in the axial direction. A recess is formed by the protruding wall portion 46, the claw portions 43 and 44 adjacent to the protruding wall portion 46, and the connecting portion 42. The axial depth of the recess is shallower than the grease reservoir 45.

  The outer diameter surface of the projecting wall portion 46 is an arc surface having the same diameter as the outer diameter of the cage 40. Further, the inner diameter surface of the projecting wall portion 46 has an arcuate shape along the outer diameter surface of the projecting wall portion 46. The radial thickness of the protruding wall portion 46 is set to a thickness that can realize the elastic deformability of the claw portions 43 and 44 necessary for holding the plurality of balls 30 in the cage 40.

  As described above, a part of the grease Gr enclosed enters the recess formed by the protruding wall portion 46, the claw portions 43 and 44, and the connecting portion 42, and adheres thereto. The grease Gr held in the recess from the beginning of the operation of the ball bearing is rotated around the retainer 40 as it is. As described above, a part of the grease Gr flowing inside the bearing is not held by the grease reservoir 45, but tends to scatter to the outer diameter side of the cage 40 through the space on one side in the axial direction from the connecting portion 42. . The grease Gr to be scattered is prevented from flowing to the outer diameter side of the cage 40 by the protruding wall portion 46 protruding from the connecting portion 42 to the one side in the axial direction. For this reason, scattering of the grease Gr is prevented. A portion of the grease Gr that cannot flow to the outer diameter side of the retainer 40 by the projecting wall portion 46 is retained in the above-described recess formed by the projecting wall portion 46 and the like, and is rotated around the retainer 40. Further, the grease Gr that cannot flow to the outer diameter side of the retainer 40 by the protruding wall portion 46 and that is not retained in the above-described recesses easily flows to the side of the retainer 40. For this reason, the grease Gr that is not held by the cage 40 easily reaches the stationary space inside the bearing and is difficult to go around on the outer periphery of the cage 40, so that it is difficult to be supplied to the balls 30.

  This ball bearing is as described above. Since the grease Gr is scraped off from the ball 30 by the edges 41a and 41b of the pocket portion 41 of the rotating retainer 40 when the bearing rotates, the grease Gr is stirred by the ball 30. Is suppressed. Further, the grease Gr is held by the grease reservoir 45 of the rotating cage 40 and is rotated together. For this reason, the flow of the grease Gr inside the bearing is suppressed, the adhesion of the grease Gr to the ball 30 is suppressed, and the stirring of the grease Gr is further suppressed. Further, between the claw portions 43 and 44 that cannot be received by the grease reservoir 45, the protruding wall 46 prevents the grease Gr from being scattered, and the grease Gr is held in the vicinity of the protruding wall 46. The flow of the grease Gr is suppressed, and the stirring of the grease Gr is further suppressed. The rotational torque of the ball bearing is further reduced by the synergistic effect of the stirring suppression action of the grease Gr based on the edges 41a and 41b of the pocket part 41, the grease reservoir 45 and the protruding wall part 46.

  As described above, this ball bearing is a grease lubricated ball bearing having a crown-shaped cage 40, and acts by the grease scraping edges 41 a and 41 b, the grease reservoir 45 and the protruding wall portion 46 of the pocket portion 41. The stirring resistance of the grease Gr can be suppressed synergistically, and the rotational torque of the ball bearing can be further reduced.

  Further, this ball bearing has a protruding wall portion 46, which is continuous in the circumferential direction between adjacent claw portions 43, 44 and protrudes from the connecting portion 42 to the one side in the axial direction. The grease Gr can be held by the claw portions 43 and 44 and the connecting portion 42 adjacent to each other. Therefore, it is possible to increase the amount of grease retained on the retainer 40 by making maximum use of the space between the claw portions 43 and 44.

  Further, in this ball bearing, the grease scraping edges 41a and 41b of the pocket portion 41 are formed on both the inner diameter side and the outer diameter side of the cage 40 over both ends around the pocket center axis Cp ( 2 and 3), the grease Gr can be scraped off by the edges 41 a and 41 b no matter which direction the ball 30 contacts the pocket portion 41.

  The test which investigates the reduction effect of a bearing rotational torque was done using the Example applicable to this ball bearing, and Comparative Examples 1-4. The ball bearing of the example is model number 6204. The difference between the example and Comparative Examples 1 to 4 is only the cage shape.

  Comparative Example 1 is a general crown-shaped cage. Compared to the embodiment, the pocket portion faces the ball only with a concave surface having a curvature smaller than the curvature of the ball, and a grease reservoir from the cage. And the point that the protruding wall portion is omitted. For this reason, in Comparative Example 1, there is no dent in the inner diameter surface of the cage, and the space between the claw portions of the adjacent pocket portions is completely space.

  Comparative Example 2 is different from Comparative Example 1 only in that a grease reservoir is employed.

  Comparative Example 3 is different from Comparative Example 2 only in that a pocket portion made of a concave curved surface having a curvature larger than the curvature of the ball is employed.

  Comparative Example 4 is different from Comparative Example 2 only in that a protruding wall portion for preventing grease scattering is employed.

An axial load of 20N was applied to the outer ring, restrained by a load cell, the bearing was rotated by rotating the inner ring, and the rotational torque of the ball bearing (torque generated by the ball bearing) was measured. The rotation speed of the inner ring is 3600 min ⁻¹ . Lithium soap grease using ester oil as the base oil was used as the grease. The amount of grease filled is 100% of the static space volume. Grease was sealed with a sealing member made of a shield plate. The test was performed in a room temperature atmosphere (25 ° C.). Table 1 shows the test results of the rotational torque. This rotational (friction) torque [Nmm] is a value after one hour operation.

  As shown in Table 1, the reduction rate of each rotational torque of Comparative Examples 2 to 4 with respect to the rotational torque of Comparative Example 1 is about 10 to 20%. On the other hand, the reduction rate of the rotational torque of the Example with respect to the rotational torque of Comparative Example 1 is over 80%. That is, in the embodiment, it is understood that a synergistic effect of reducing the stirring resistance of the grease is achieved based on the combined use of the edge of the pocket portion, the grease reservoir, and the protruding wall portion, thereby greatly reducing the rotational torque.

  In Comparative Example 1, the grease cannot be held on the cage, and the grease is agitated. Further, the grease attached to the surface of the ball also enters the clearance between the ball and the pocket portion and is subjected to shearing, so that frictional torque (shear torque) is generated. For this reason, rotational torque is high.

  In Comparative Example 2, the grease is held in the grease reservoir. However, since the amount of grease filled is large, the entire grease flow cannot be stopped, and not only the grease is stirred, but also the grease attached to the surface of the ball enters the gap between the ball and the pocket. Shear torque is generated. For this reason, rotational torque is high.

  In Comparative Example 3, in addition to the effect of Comparative Example 2, the shear torque was reduced by scraping the grease attached to the surface of the ball at the edge of the pocket portion. However, since the amount of grease is large, the entire grease flow cannot be stopped, and not only the grease is stirred, but also more grease than scraped from the balls enters between the pocket and the balls. Shear resistance is occurring. For this reason, rotational torque is large.

  In Comparative Example 4, the grease flow on the cage is suppressed, but the grease attached to the surface of the ball enters the clearance between the ball and the pocket portion, and shear torque is generated. For this reason, rotational torque is large.

  In the embodiment, the grease is held on the cage, and the grease attached to the surface of the ball is scraped off at the edge of the pocket portion. The rotational torque can be greatly reduced by suppressing both the shear between the ball and the pocket and the stirring of the grease.

  The time-dependent change of the rotational torque of the comparative example 1 and an Example is shown in FIG. 5 and FIG. FIG. 5 shows the results when the amount of grease filled is 100% of the static space volume. FIG. 6 shows the results when the grease filling amount is 75% of the static space volume. In the case of FIG. 5, in the example, a torque spike in which the rotational torque temporarily increased was observed about once in one hour. This is because the amount of grease filled is large, so that it was not possible to completely retain the grease on the cage, and it was assumed that the grease that could not be retained was being stirred. On the other hand, in the case of FIG. 6, generation of torque spikes was not observed in the example, and the rotational torque could always be reduced by about 80% compared to the same enclosed amount of Comparative Example 1. From this, it can be seen that in the cage of the example, when the amount of grease filled is 75% or less of the static space volume, a particularly good rotational torque reduction effect is exhibited.

  As shown in the example of FIG. 6 of the embodiment, it is ideal that all the grease existing outside the stationary space is held on the surface of the cage when the bearing rotation time has exceeded a certain time. In order to achieve this state, it is ideal to define the pocket edge formation range, the grease pool capacity, and the protruding wall formation range according to the ratio of the amount of grease filled to the static space volume. It is.

  It is not essential that the protruding wall portion of the cage is continuous in the circumferential direction between adjacent claw portions as in the first embodiment and examples described above, and the protruding wall divided between the claw portions. Even if it is a part, the grease retention effect is obtained. As an example, a second embodiment of the present invention will be described with reference to FIG. In the following, only differences from the first embodiment will be described.

  As shown in FIG. 7, the protruding wall portion 61 of the cage 60 according to the second embodiment protrudes from the connecting portion 42 to the one axial side at a position away from each of the adjacent claw portions 43 and 44 in the circumferential direction. ing. The circumferential length of the projecting wall portion 61 is set to be not less than half of the minimum circumferential interval between the adjacent claw portions 43 and 44. Both ends in the circumferential direction of the protruding wall portion 61 are in positions where they cannot contact the claw portions 43 and 44 that are elastically deformed when the ball is inserted into the pocket portion 41. For this reason, in the second embodiment, the protruding wall portion 61 can prevent the elastic deformation of the claw portions 43 and 44 from being hindered.

  A third embodiment of the present invention is shown in FIG. The retainer 70 according to the third embodiment includes a first projecting wall portion 71 extending in the circumferential direction from one of the adjacent claw portions 43 and 44, and the adjacent claw portions 43 and 44. And a second projecting wall portion 72 extending in the circumferential direction from the other claw portion 44 opposite to the other. The circumferential lengths of the protruding wall portions 71 and 72 are set to 1/3 or more of the minimum circumferential interval between the adjacent claw portions 43 and 44. In the third embodiment, the grease Gr can be held by the first protruding wall portion 71, the claw portion 43 adjacent to the first protruding wall portion 71, and the connecting portion 42. In the third embodiment, the grease Gr can be held by the second protruding wall portion 72, the claw portion 44 adjacent to the second protruding wall portion 72, and the connecting portion 42.

  In the above-described embodiments and examples, the surface portion of the cage that is located on the other side in the axial direction with respect to the pocket portion 41 is shaped along the pocket portion 41, but the shape of the surface portion is changed. This may improve the centrifugal strength of the cage. A fourth embodiment as an example thereof will be described with reference to FIGS.

  FIG. 10 shows the cage 80 according to the fourth embodiment cut along a virtual cylindrical surface passing through the center O of the pocket portion 41 and concentric with the bearing central axis, and the vicinity of the pocket portion 41 is viewed from the pocket central axis Cp direction. A cross section is shown. Here, the virtual axial plane Pa of the pocket portion 41 is set to a 0 ° position in the rotation angle around the pocket central axis Cp.

  In general, in a crown-shaped cage, in order to secure an axial depth in which a ball (not shown) is accommodated in the pocket portion, the thickness of the cage portion is reduced near the center in the circumferential direction of the pocket portion. Thickness greatly affects the centrifugal strength of the cage. In particular, the pocket portion 41 has an axial depth that cannot contact the ball in the vicinity of the virtual axial plane Pa, and the thickness of the cage portion in the vicinity affects the centrifugal strength of the cage 80.

  As shown in FIGS. 9 and 10, the cage 80 is a portion in the range of −30 ° to 30 ° from the virtual axial plane Pa around the pocket central axis Cp in the pocket portion 41 (p1 in FIG. A flat width surface portion 81 along the radial direction is provided at a portion located on the other side in the axial direction with respect to the arc line portion between p2. The width surface portion 81 is located at the other end in the axial direction of the cage width of the cage 80. As described above, the fourth embodiment can eliminate the stealing of the thickness that is recessed in the axial direction in a range in which it is difficult to secure the thickness of the cage portion, and can improve the centrifugal strength of the cage 80.

  In addition, if the width surface portion is formed at a site on the other side in the axial direction with respect to the range of −30 ° or less and 30 ° or more from the virtual axial plane Pa, the centrifugal strength can be further increased.

  In each of the above-described embodiments and examples, the scraping of grease can be performed at all the edges of the inner and outer openings formed by the pocket portion. However, the range in which the scraping of grease can be performed is limited, and the centrifugal strength of the cage is improved. May be. A fifth embodiment as an example thereof will be described with reference to FIGS.

  The pocket portion 91 of the cage 90 according to the fifth embodiment has a bottom surface 91a having a shape that can contact the ball 30 at a position on the virtual axial plane Pa, and a curved surface 91b that cannot contact the ball 30.

  FIG. 12 shows the shape of the pocket portion 91 in a cross section viewed from the pocket central axis Cp direction by cutting the cage 90 along a virtual cylindrical surface passing through the center O of the pocket portion 91 and concentric with the bearing central axis. This cross section is on the radial position having the same diameter as the center O of the pocket portion 91. Here, the virtual axial plane Pa of the pocket portion 91 is set to a 0 ° position in the rotation angle around the pocket central axis Cp. 13 shows the shape of the bottom surface 91a on the virtual axial plane Pa in FIG. 12 by a solid line, and shows the shape of the curved surface 91b on the virtual plane including the pocket center axis Cp at the position of the AA line in FIG. It is a schematic diagram which shows with the dashed-dotted line and shows the surface of the ball 30 on the same virtual plane with the dashed-dotted line.

  As shown in FIGS. 11 and 13, the bottom surface 91 a of the pocket portion 91 has a concave shape with a curvature smaller than the curvature of the ball 30. The bottom surface 91a is continuous between the edges 41a and 41b. The bottom surface 91a is formed around the pocket central axis Cp only within the range of −30 ° to 30 ° from the virtual axial plane Pa.

  The curved surface 91 b of the pocket portion 91 has a concave shape with a curvature larger than the curvature of the ball 30. The curved surface 91b is continuous between the edges 41a and 41b. Further, the curved surface 91b is formed in the entire region other than the range of −30 ° to 30 °, between both ends around the pocket central axis Cp.

  As can be seen from FIG. 13, the bottom surface 91a of the pocket portion 91 can be in contact with the ball 30 at a position on the cross section of FIG. 12 and on the virtual axial plane Pa. It is. On the other hand, the curved surface 91b of the pocket portion 91 can contact the ball 30 only at the inner and outer edges of the curved surface 91b, that is, only in the entire region of the edges 41a and 41b other than the range of −30 ° to 30 °.

  As described above, the fifth embodiment increases the thickness of the cage portion in the vicinity of the virtual axial plane Pa by allowing the bottom surface 91a of the pocket portion 91 to contact the ball 30, thereby increasing the centrifugal strength of the cage 90. Easy to get.

  In particular, in the fifth embodiment, the bottom surface 91a is shaped so as to be able to contact the ball 30 on the radial position having the same diameter as the center O of the pocket portion 91. Therefore, the shape of the pocket portion 91 is particularly recessed toward the other side in the axial direction. Thickness can be secured at the cage part.

  In the fifth embodiment, the bottom surface 91a of the pocket portion 91 is formed around the pocket central axis Cp only within the range of −30 ° to 30 ° from the virtual axial plane Pa. While obtaining the strength, the edges 41a and 41b for scraping the grease can be arranged in the entire region other than the range of −30 ° to 30 ° to reduce the stirring resistance.

  A sixth embodiment is shown in FIGS. The cage 100 according to the sixth embodiment is a modified example from the fifth embodiment, and is different from the fifth embodiment only in that the shape and formation range of the bottom surface 101a of the pocket portion 101 are changed.

  FIG. 15 shows the shape of the pocket portion 101 in a cross section when the cage 100 is cut along a virtual cylindrical surface passing through the center O of the pocket portion 101 and concentric with the bearing central axis, as viewed from the pocket central axis Cp direction. 16 shows the shape of the bottom surface 101a on the virtual axial plane Pa in FIG. 15 by a solid line, and shows the shape of the curved surface 91b on the virtual plane including the pocket center axis Cp at the position of the line BB in FIG. It is a schematic diagram which shows with the dashed-dotted line and shows the surface of the ball 30 on the same virtual plane with the dashed-dotted line.

  The bottom surface 101a of the pocket portion 101 has a concave shape in which the curvature gradually increases as the pocket portion 101 approaches from the outer diameter side edge 41b to the inner diameter side edge 41a in the radial direction. The bottom surface 101 a can contact the ball 30 only on the inner diameter side of the cage 100. On the inner diameter side of the bottom surface 101a, in the vicinity of the edge 41a, an axial thickness similar to that of the fifth embodiment is secured. The edge 41b on the outer diameter side of the pocket portion 101 can contact the ball 30 across both ends around the pocket central axis Cp. The edge 41a on the inner diameter side of the pocket portion 101 can contact the ball 30 only in the entire region other than the range of −30 ° to 30 °, as in the fifth embodiment.

  Thus, in the sixth embodiment, the thickness of the cage portion is increased by the bottom surface 101a of the pocket portion 101 on the inner diameter side of the cage 100, whereas on the outer diameter side of the cage 100, which ball 30 is Even when contact is made from the direction, the grease can be scraped off at the edge 41 b of the pocket portion 101.

  Comparing the fifth embodiment with the sixth embodiment, the sixth embodiment has a wider range in which the grease can be scraped off at the edge 41b of the pocket portion, and the contact probability with the ball 30 is higher. The rotational torque reduction effect is increased.

  In the cage of the fifth embodiment or the sixth embodiment described above, the width surface portion of the fourth embodiment may be further added. Moreover, you may employ | adopt the protruding wall part of 2nd embodiment or 3rd embodiment in the holder | retainer of 4th embodiment-6th embodiment.

  In each of the embodiments and examples disclosed this time, the pocket portion shape on an arbitrary virtual plane including the pocket center axis is a shape in which a single or a plurality of concave curves are smoothly continuous. However, the rotational torque reduction effect of the ball bearing can be obtained similarly. In short, it is only necessary to set a concave shape so that the ball and the pocket portion can contact only at the edge within a predetermined angular range around the central axis of the pocket where the edge of the pocket portion for scraping the grease is disposed.

  The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. Therefore, the scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10 Inner ring 20 Outer ring 30 Ball 40, 60, 70, 80, 90, 100 Cage 41, 91, 101 Pocket part 41a, 41b Edge 42 Connecting part 43, 44 Claw part 45 Grease reservoir 46, 61, 71, 72 Projection wall Part 50 Sealing member 81 Width surface portion 91a, 101a Bottom surface 91b Curved surface

Claims (14)

An inner ring, an outer ring, a plurality of balls interposed between the inner ring and the outer ring, and a cage for holding the plurality of balls,
Grease is sealed between the inner ring and the outer ring,
The cage includes a plurality of pocket portions that are open on the inner diameter side, the outer diameter side, and one axial side of the cage, and a connecting portion that is continuous in the circumferential direction between the pocket portions adjacent in the circumferential direction. And a pair of claw portions projecting on one side in the axial direction so as to form both end portions on one side in the axial direction of the pocket portion from the joint portions on both sides adjacent to the pocket portion,
The pocket portion has an edge capable of scraping the grease from the ball by line contact with the ball held in the pocket portion,
The retainer is adjacent to the joint portion on one side in the axial direction with respect to the joint portion and a grease reservoir having a shape recessed from the inner diameter to the outer diameter side of the retainer at a position on the other axial side with respect to the joint portion. A ball bearing further comprising a protruding wall portion that prevents the grease from scattering at a position between the claw portions and a position on the outer diameter side of the cage.   The ball bearing according to claim 1, wherein the protruding wall portion of the cage is continuous in the circumferential direction between adjacent claw portions and protrudes from the connecting portion to one axial side.   2. The ball bearing according to claim 1, wherein the protruding wall portion of the cage protrudes from the connecting portion to one axial side at a position separated from each of the adjacent claw portions in the circumferential direction.   The cage includes a first protruding wall portion extending in the circumferential direction from one of the adjacent claw portions, and a second extending in the circumferential direction from the other of the adjacent claw portions opposite to the one. The ball bearing according to claim 1, comprising the protruding wall portion.   When a virtual imaginary straight line passing through the center of the pocket portion is defined as a pocket central axis, the edge of the pocket portion extends over both ends around the pocket central axis on each of the inner diameter side and the outer diameter side of the cage. The ball bearing according to any one of claims 1 to 4, wherein the ball bearing is formed.   The ball bearing according to any one of claims 1 to 4, wherein the pocket portion has a bottom surface that can contact the ball at a position on a virtual axial plane including a center of the pocket portion.   The ball bearing according to claim 6, wherein the bottom surface of the pocket portion has a shape that can come into contact with the ball at a radial position having the same diameter as the center of the pocket portion.   When the virtual straight line in the radial direction passing through the center of the pocket portion is a pocket central axis and the virtual axial plane is at 0 ° around the pocket central axis, the bottom surface of the pocket portion is around the pocket central axis. The ball bearing according to claim 6, wherein the ball bearing is formed only within a range of −30 ° to 30 °. The bottom surface of the pocket portion is formed on the inner diameter side of the cage,
The ball bearing according to claim 8, wherein the edge of the pocket portion is formed between both ends around the pocket central axis on the outer diameter side of the cage.   The ball bearing according to claim 6, wherein the bottom surface of the pocket portion has a concave shape with a curvature smaller than the curvature of the ball.   When the virtual axial plane including the center of the pocket portion is set to a 0 ° position around the pocket central axis, the cage is in a range of −30 ° to 30 ° around the pocket central axis of the pocket portion. The ball bearing according to any one of claims 1 to 10, wherein the ball bearing has a width surface portion along a radial direction at a portion positioned on the other side in the axial direction.   The ball bearing according to any one of claims 1 to 11, wherein the edge of the pocket portion includes an edge of a concave curved surface having a curvature larger than the curvature of the ball.   The ball bearing according to any one of claims 1 to 12, wherein an amount of the grease enclosed is 75 to 100% of a static space volume inside the bearing.   The ball bearing according to claim 1, wherein the cage is formed of a synthetic resin.

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