JP2012189206A - Ball bearing, and motor and spindle device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life ball bearing in which a retention property of grease inside a pocket is enhanced, and the pocket of a retainer and a sliding contact part with balls are reliably lubricated, and to provide a motor and a spindle device using the ball bearing.SOLUTION: An angular ball bearing 10 includes an outer ring 11, an inner ring 12, a plurality of balls 13 arranged between the outer ring 11 and the outer ring 12, and a retainer 14 having a plurality of pockets 15 each holding a plurality of balls 13. The pocket 15 of the retainer 14 has an inner surface 15a formed by a cylindrical surface, and the inner surface 15a formed by the cylindrical surface is formed with a recess groove 24 in a noncontact area 18 out of contact with the ball 13.

Description

  The present invention relates to a ball bearing, a motor using the same, and a spindle device, and more specifically, to a drive motor used in general industrial machines and machine tools, a spindle device of a machine tool, and the like that rotate at high speed. The present invention relates to a ball bearing, a motor using the same, and a spindle device.

  Conventional lubrication methods for lubricating high-speed motors and rolling bearings that support the spindle of machine tools include a small amount of lubrication, such as grease lubrication, oil air / oil mist lubrication, etc., to reduce the stirring resistance of the lubricant and suppress temperature rise. The law is adopted. Oil / oil mist lubrication improves seizure resistance at high speeds compared to grease lubrication, but the supply / exhaust mechanism is complicated and the cost increases, and the wind noise of air blown from the nozzle toward the bearing It is necessary to consider the generation of noise caused by oil leakage and the lubricating oil spill after use from the oil drain hole and labyrinth. For this reason, in recent years, there has been a growing demand for high-speed motors and rolling bearings that support high-speed spindles due to grease lubrication that does not release lubricant to the outside.

On the other hand, in grease lubrication, the grease filled in the bearing is consumed with use or gradually flows out from the openings at both ends of the bearing, and the bearing life tends to be shortened compared to oil-air / oil mist lubrication. is there. In addition to the rolling contact portion between the ball and the inner and outer rings, the lubricant must be supplied to the contact portion inside the ball and the cage pocket. Due to the action, it is easy to move to the outer ring side, and the grease in the pocket tends to be insufficient. For the above reasons, the life of grease tends to decrease at high speed rotation.
In particular, the spindle of a machine tool has recently been frequently subjected to continuous machining at a high speed and cycle machining at a rapid acceleration / deceleration operation, and the grease life tends to decrease.

  Also, in grease lubrication, when the grease consumption and deterioration progresses and the formation of a lubricating oil film on the cage and rolling element or on the cage and outer / inner ring guide surface becomes unstable, the frictional resistance of the sliding contact surface fluctuates. As a result, self-excited vibration of the cage occurs, which may cause abnormal noise and deterioration of rotation accuracy. In order to prevent such a phenomenon, there has been proposed a ball bearing that uses a ball guide type synthetic resin cage in which the cage is guided by a ball, and that easily holds grease inside the pocket ( For example, see Patent Document 1.)

Further, in the ball bearing described in Patent Document 2, the pocket has a recess in the surface on the axial direction side of the ball bearing, the pocket contains more lubricant, and the ball does not contact the inner surface of the recess. It is disclosed to prevent the cage sound from being induced.
Furthermore, in the ball bearing described in Patent Document 3, a non-contact portion that does not contact the ball rolling surface is provided on the inner surface of the central portion of the pocket, and a lubricant is provided between the non-contact portion and the ball rolling surface. Hold. As a result, the frictional force acting on the contact portion where the inner surface of the pocket and the rolling surface of the ball come into contact is reduced, and the generation of the cage noise is reduced.

JP 2003-42160 A JP 2002-98150 A JP 2000-39024 A

By the way, in recent years, the spindle of a machine tool is used in a region where the dmn value (dm: pitch circle diameter (mm) of rolling elements, n: shaft rotational speed (min ⁻¹ )) exceeds 1 million. It is increasingly demanded. In the spindle used in such a region, even if the ball bearing having the ball guide type cage described in Patent Document 1 is adopted, the lubricating oil is depleted at the sliding contact portion between the cage pocket and the ball. However, self-excited vibration may occur, and further improvement in the durability of grease lubrication has been desired.

  Further, in the ball bearing described in Patent Document 2, there is a possibility that the ball contacts the edge at the rising portion of the recess, and there is a possibility that problems such as heat generation and wear at the edge portion occur. Furthermore, in the ball bearing described in Patent Document 3, the contact portion with which the ball contacts is not cylindrical, and the lubricant held between the non-contact portion and the rolling surface of the ball is less than the non-contact portion. Further, since the amount supplied to the contact portion on the radially inner side is different from the amount supplied to the contact portion on the radially outer side, further improvement is desired.

  In addition, a ceramic ball with a small specific gravity is used to reduce the centrifugal force acting on the ball during high-speed rotation, thereby suppressing the heat generation of the bearing and the method of suppressing the thermal deterioration of the grease. Even if such measures are taken, there is a limit to the reduction in heat generation, and there has been a demand for a method that can ensure a lubricating oil film in the vicinity of the sliding contact portion between the cage pocket and the ball.

  The present invention has been made in view of the above-described problems, and its purpose is to increase the grease retention in the pocket, to reliably lubricate the sliding contact portion between the pocket of the cage and the ball, and to have a long service life. An object of the present invention is to provide a ball bearing, a motor using the ball bearing, and a spindle device.

The above object of the present invention can be achieved by the following constitution.
(1) A ball bearing comprising an outer ring, an inner ring, a plurality of balls disposed between the outer ring and the inner ring, and a cage having a plurality of pockets for holding the plurality of balls,
The cage pocket has an inner surface formed by a cylindrical surface;
A ball bearing, wherein a concave groove is formed in a non-contact area where the ball does not contact the inner surface formed by the cylindrical surface.
(2) The ball bearing according to (1), wherein the non-contact region in which the concave groove is formed is located radially inward from the contact region with which the ball contacts.
(3) The cage is a ball guide system,
On the inner diameter side end portion of the pocket, a convex portion that protrudes in contact with the ball and restricts the radial movement of the cage is provided,
The ball bearing according to (1) or (2), wherein the non-contact region in which the concave groove is formed is formed between the contact region and the convex portion.
(4) The ball bearing according to any one of (1) to (3), which is lubricated with grease.
(5) The cage includes a pair of annular portions on both sides in the axial direction and a plurality of pillars connecting the pair of annular portions, and an inner surface of the pocket is formed in a cylindrical shape,
The said recessed groove is formed along the circumferential direction of the said pocket, The ball bearing in any one of (1)-(4) characterized by the above-mentioned.
(6) The cage includes an annular portion and a plurality of pillar portions extending in the axial direction from the annular portion, and the pocket is formed in a cylindrical shape that opens one axial direction,
The said recessed groove is formed along the circumferential direction of the said pocket, The ball bearing in any one of (1)-(4) characterized by the above-mentioned.
(7) A motor using the ball bearing according to any one of (1) to (6).
(8) A spindle device characterized in that the machine tool spindle is rotatably supported by using the ball bearing according to any one of (1) to (6).

According to the ball bearing of the present invention, the pocket of the cage has an inner surface formed by a cylindrical surface, and a concave groove is formed on the inner surface formed by the cylindrical surface in a non-contact region where the ball does not contact. The Accordingly, the lubricant can be accumulated in the recessed groove formed in the non-contact area where the ball does not contact, and the ball and the pocket are prevented by the lubricant collected in the recessed groove while preventing the lubricant in the recessed groove from being scraped off by the ball. The proper lubrication state is maintained well, and the lubrication life can be extended.
In addition, with the cage assembled in the ball bearing, a certain clearance in the radial direction and the axial direction is maintained between the ball and the pocket, and the ball has an inner surface of the pocket due to this clearance. Contact in a limited area. Since this concave groove is formed in a non-contact area where the ball does not contact even when the ball has moved the maximum amount, the ball does not contact the edge of the concave groove and can prevent local contact with the edge. It is possible to prevent problems such as heat generation and wear of the part.

  In particular, in the case of grease lubrication, the non-contact area where the recess groove is formed is located radially inward from the contact area where the ball contacts, so that the grease is gradually removed from the grease held in the recess groove by the action of centrifugal force. Since the base oil discharged to the ball is supplied to the contact portion between the ball and the pocket, it is possible to prevent the bearing from being damaged due to the lack of lubricant inside the pocket at high speed rotation.

It is sectional drawing of the ball bearing which concerns on one Embodiment of this invention. (A) is a partial top view of the holder | retainer in FIG. 1, (b) is a fragmentary sectional view which follows the II-II line in (a). (A) is a figure which shows the contact position of a bearing ring and a ball at the time of stationary, (b) is sectional drawing which shows the contact position of a bearing ring and a ball at the time of rotation. It is a fragmentary sectional view showing the 1st modification of a cage. It is a fragmentary sectional view showing the 2nd modification of a cage. It is a fragmentary sectional view showing the 3rd modification of a cage. (A) is sectional drawing which shows the 4th modification of a holder | retainer, (b) is a fragmentary top view of a holder | retainer, (c) is a fragmentary sectional view of a holder | retainer. It is sectional drawing which shows the 5th modification of a holder | retainer.

  Hereinafter, an embodiment of a ball bearing according to the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the angular ball bearing 10 of the present embodiment includes an outer ring 11 having an outer ring raceway surface 11a on an inner peripheral surface, an inner ring 12 having an inner ring raceway surface 12a on an outer peripheral surface, and an outer ring raceway surface. A plurality of balls 13 that are rotatably arranged between the inner ring raceway surface 11a and the inner ring raceway surface 12a, and are arranged between the outer ring 11 and the inner ring 12 while holding the balls 13 in a pocket 15 so as to roll freely. A machined cage 14 is provided. In addition, grease as a lubricant is sealed in the internal space of the angular ball bearing 10.

  On the inner peripheral surface of the outer ring 11, a shoulder portion 11b is formed on one side of the outer ring raceway surface 11a. Further, on the outer peripheral surface of the inner ring 12, a shoulder portion 12 b is formed at a position symmetrical to the shoulder portion 11 b about the ball 13. The angular ball bearing 10 has a contact angle α when stationary, and applies a radial load and a thrust load. In addition, a seal member 16 formed in an annular shape with a core metal covered with an elastic body such as rubber is attached to openings on both side surfaces of the outer ring 11 and the inner ring 12 to prevent grease from flowing out from the inside. .

  The cage 14 is a ball guide cage made of a synthetic resin, and as shown in FIG. 2, the annular portions 22a and 22a on both sides in the axial direction, and a plurality of column portions 23 that connect the annular portions 22a and 22a. These annular portions 22a, 22a and the adjacent pillar portion 23 constitute a plurality of pockets 15 for holding the ball 13 so as to roll freely.

  The pocket 15 of the cage 14 has an inner surface 15 a formed by a cylindrical surface and has a substantially cylindrical shape penetrating in the radial direction. The inner diameter of the cage 15 is slightly larger than the outer diameter of the ball 13.

  Further, a convex portion 21 is provided on the inner diameter side end portion of the pocket 15 of the cage 14 so as to protrude toward the inside of the pocket 15. The convex portion 21 protrudes from the column portion 23 into the pocket 15 along the circumferential direction. As shown in FIG. 2A, the shape of the end edge of the convex portion 21 protruding into the pocket 15 is formed in an arc shape when viewed from the radial direction.

  The convex portion 21 is in contact with the ball 13 and restricts the movement of the cage 14 in the radial direction. A certain clearance in the radial direction and the axial direction is held between the inner surface 15a of the pocket 15 and the ball 13, and accordingly, the ball 13 and the cage 14 are radially disposed on the inner surface 15a of the pocket 15. A contact area 17 with which the ball 13 comes into contact when relative movement is defined.

  Further, a non-contact region 18 where the ball 13 does not contact is formed on the inner surface formed by the cylindrical surface between the contact region 17 and the convex portion 21 in the radial direction from the contact region 17, that is, in the radial direction. . A recess groove 24 having a semicircular cross section is formed in the non-contact region 18 along the circumferential direction of the pocket 15.

As a synthetic resin material for the cage 14, phenol, polyamide 66, polyamide 46, polyphenylene sulfide, thermoplastic polyimide, polyether ether ketone, or the like can be used as a base material. Furthermore, it is preferable to add 10 to 30% by weight of carbon fiber or aramid fiber or 10 to 40% by weight of glass fiber to improve the strength. Moreover, in order to use at high speed rotation, although carbon fiber and an aramid fiber are more preferable, glass fiber can also be selected according to use conditions. If the added amount of carbon fiber or aramid fiber is less than 10% by weight, sufficient strength cannot be obtained, and if it is more than 30% by weight, the moldability deteriorates and the appearance deteriorates. By making the addition amount of carbon fiber or aramid fiber 20 to 30% by weight, both strength and formability are improved, which is more preferable. For the same reason, the glass fiber is preferably added in an amount of 10 to 40% by weight.
The cage 14 may be a metal material such as iron or copper alloy in addition to the synthetic resin material.

  Such a cage 14 can be manufactured by various methods. For example, all of the cages 14 may be manufactured by cutting, or may be manufactured by cutting only the recessed groove 24 after injection molding, or all by injection molding. It can also be produced.

  In the angular ball bearing 10 configured as described above, after grease is sealed inside, the grease contacts the sliding contact portion between the ball 13 and the pocket 15, and the raceway surfaces 11 a and 12 a of the balls 13 and the outer inner rings 11 and 12. A so-called leveling operation is performed in which the number of revolutions is gradually increased in the initial stage of the operation so as to reach a portion requiring lubrication such as a rolling contact portion. Thereby, when the grease adhering to the ball 13 is scraped off by the convex portion 21, the grease can easily enter the concave groove 24, so that the grease can be sufficiently held in the concave groove 24.

  Further, during normal operation, the grease can be stored in the concave groove 24 formed in the non-contact area 18, and the grease in the concave groove 24 is prevented from being scraped off by the balls 13 and the grease collected in the concave groove 24. As a result, an appropriate lubrication state between the balls 13 and the pockets 15 can be satisfactorily maintained, and the lubrication life can be extended. Further, since the recess groove 24 is formed in the non-contact region 18 where the ball 13 does not contact even when the ball 13 has moved the maximum amount, the ball 13 does not contact the edge portion of the recess groove 24 and Local contact can be prevented, and defects such as heat generation and wear at the edge can be prevented.

  In particular, in the case of grease lubrication, the non-contact region 18 where the recess groove 24 is formed is positioned radially inward from the contact region 17 with which the ball 13 contacts, so that the recess groove 24 is held by the centrifugal force action. Since the base oil component gradually discharged from the grease is supplied to the contact portion between the ball 13 and the pocket 15, damage to the ball bearing 10 due to lack of lubricant inside the pocket at high speed rotation can be prevented.

  Furthermore, even if the excess grease other than the concave groove 24 once adheres to the peripheral portion in the ball bearing 10, not all of the grease is supplied to a portion that requires grease such as a rolling contact portion. Only grease near the center of rotation, such as near, is supplied. In addition, the grease adhering to the non-rotating part such as the outer ring, only the base oil on the surface of the grease near the rolling contact part contributes to lubrication. On the other hand, most of the grease attached to the outer peripheral surface of the inner ring is likely to be dispersed due to the centrifugal force during high-speed rotation.

  On the other hand, most of the grease held by the recessed grooves 24 of this embodiment can contribute to lubrication. Moreover, the base oil content in the grease can gradually ooze out into the pocket by the centrifugal force effect during the revolution of the cage 14.

  The revolution number of the cage 14 is normally about 40% of the inner ring speed in the case of inner ring rotation (conversely, about 60% of the outer ring speed in the case of outer ring rotation). The base oil content from the grease due to the centrifugal force is moderate, and the base oil content can be supplied to the rolling contact portion or the sliding contact portion over a long period of time.

Further, in the case of high-speed rotation in which the dmn value exceeds 1 million (particularly in constant pressure preload), the ball 13 is displaced toward the outer ring 11 by the centrifugal force Fc acting on the ball 13 as shown in FIG. The contact angle α _e with the outer ring 11 is closer to the bottom of the raceway surface 11a (in a direction smaller than the contact angle α when not rotating), and the contact angle α _i of the inner ring 12 is closer to the shoulder 12b of the raceway surface 12a ( In a direction larger than the contact angle α of the non-rotating shaft. That is, the contact surface pressure acting on the ball 13 changes from the stationary directions Q _i and Q _e to the rotating directions Q _1i and Q _1e . In this case, on the inner ring 12 side, it becomes easy to supply the base oil from grease adhering to the bearing end face side such as the shoulder 12b of the inner ring 12, while on the outer ring 11 side, the balls 13 are closer to the groove bottom. The base oil is difficult to be supplied due to the tendency to move away from the grease adhering to the shoulder 11b of the outer ring 11. However, since the recessed groove 24 is provided in the non-contact region 18 as in this embodiment, the base oil is oozed out from the grease held in the recessed groove 24 and supplied to the outer ring side via the balls 13 by centrifugal force. can do.

(First modification)
FIG. 4 is a partial cross-sectional view showing a first modification of the cage. In this retainer 14a, a concave groove 24a having a U-shaped cross section is formed in the circumferential direction in the non-contact region 18 on the inner surface 15a of the pocket 15 formed by a cylindrical surface. By forming such a U-shaped concave groove 24a, it is possible to secure a wide space for holding the lubricant.

(Second modification)
FIG. 5 is a partial cross-sectional view showing a second modification of the cage. In this retainer 14b, a concave groove 24b having a V-shaped cross section is formed in the circumferential direction in the non-contact region 18 on the inner surface 15a of the pocket 15 formed by a cylindrical surface. By forming such a concave groove 24b having a V-shaped cross section, the lubricant can be held and the lubricant can be smoothly supplied to the rolling contact portion and the sliding contact portion.

(Third Modification)
FIG. 6 is a partial cross-sectional view showing a third modification of the cage. In this retainer 14c, in the inner surface 15a of the pocket 15 formed by the cylindrical surface, a recess-shaped groove 24c having a substantially spoon-shaped cross section that is narrow at the opening and widened inside is formed in the non-contact region 18 in the circumferential direction. Is formed. By forming the concave groove 24c having a substantially spoon-shaped cross section, the retention of the lubricant is improved, for example, the outflow of the base oil due to the centrifugal force can be suppressed even during high-speed rotation, and the base oil can be It is possible to give continuity discretely.

In addition, the cross-sectional shape of the recessed groove 24 is not limited to the above-described embodiment and each modification, and can be formed in any cross-sectional shape.
Moreover, although it is desirable for lubrication to form the recessed groove 24 in all the pockets 15, it may be provided only in a specific pocket 15 as necessary.
Furthermore, the recessed groove 24 may be formed over the entire circumference in the circumferential direction of the inner surface of the pocket 15 or may be formed only in a specific phase in the circumferential direction. Moreover, if it is in the non-contact area | region 18, the recessed part groove | channel 24 may not be formed along the circumferential direction, but multiple things formed along the radial direction may be arrange | positioned in the circumferential direction, for example.

(Fourth modification)
FIGS. 7A to 7C show a fourth modification of the cage. This retainer 14d has an annular portion 22a and a plurality of column portions 23 extending in the axial direction from the annular portion 22a, and the pocket 15 is formed in a cylindrical shape that opens in one axial direction. It is a vessel. The retainer 14 d is also a ball guide retainer that is provided with a protruding portion 21 protruding from the inner diameter side end of the pocket 15 and restricts the movement of the balls 13 in the radial direction.
Also in this retainer 14d, the recessed groove 24 is formed along the circumferential direction of the pocket 15 in the non-contact region 18 of the inner surface 15a of the pocket 15 forming the cylindrical surface.
Therefore, the crown-type cage 14d can achieve the same effects as those of the above embodiment.

(5th modification)
FIG. 8 shows a fifth modification of the cage. The retainer 14e has an even number of pockets 15 (eight in FIG. 8), and at least every other pocket (every four in FIG. 8) pockets 15 are equally spaced in the circumferential direction. 15 concave grooves 24 are provided along the circumferential direction.

Thus, by providing the recessed groove 24 in at least every other pocket 15, the circumferential minimum wall thickness of the column portion 23 of the pocket 15 can be increased.
For example, in an angular ball bearing, when it is desired to increase the bearing load capacity and the bearing rigidity, the specification has a large number of balls, and the circumferential thickness of the column portion 23 of the pocket 15 must be reduced. In such a cage, when the recessed grooves 24 are provided in the pockets 15 on both sides of the pillar part 23, the thickness of the pillar part 23 in the circumferential direction is locally reduced, and the strength of the pillar part 23 is reduced. Concerned. However, in the configuration of this modified example, the recessed grooves 24 are not provided in the pockets 15 on both sides of the column portion 23, and the strength of the column portion 23 can be ensured.

  The supply of a lubricant such as grease inside each pocket 15 is performed by the lubricant accumulated in the concave groove 24 in the pocket 15 having the concave groove 24, and the pocket 15 having no concave groove 24. Then, the lubricant in the recessed groove 24 is replenished to the rolling contact surfaces (the inner ring raceway surface 12a and the outer ring raceway surface 11a) through the balls 13 by rotation, and then adheres to the balls 13 in the pockets 15 that do not have the recessed grooves 24. Then replenished.

  Further, since the pockets 15 in which the recessed grooves 24 are formed are arranged in the circumferential direction, the cage 14e does not have an unbalanced shape, and does not apply an eccentric load during high-speed rotation, The cage 14e does not rotate eccentrically, and a part of the cage 14e does not wear or break.

In the fifth modified example, at least every other pocket 15 in which the recessed grooves 24 are provided may be arranged at equal intervals in the circumferential direction. For example, when the number of the pockets 15 is 18, the concave grooves 24 are formed by every other nine (40 ° interval) pockets 15 and every other six (60 ° interval) pockets 15, 5. It suffices if it is provided in any one of every third pocket 15 (120 ° interval) and every other eight pockets 15 (180 ° interval).
Further, the fifth modified example can be applied in combination with any of the present embodiment and the first to fourth modified examples. Further, as described above, the recessed groove 24 has a cross-sectional shape and a circumferential length of the pocket 15. The direction can be arbitrarily formed.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.
The angular ball bearing 10 of the present embodiment may be suitably used to support the main shaft in a main shaft device such as a machine tool, or may be applied to support the motor shaft of a high-speed motor.
Further, in the above-described embodiment and each modified example, the present invention is applied to the ball guide type cage, but it may be an outer ring guide type or an inner ring guide type cage. The pocket of the vessel has an inner surface formed by a cylindrical surface, and a concave groove is formed on the inner surface formed by the cylindrical surface in a non-contact region where the ball does not contact.

DESCRIPTION OF SYMBOLS 10 Angular contact ball bearing 11 Outer ring 12 Inner ring 13 Ball 14 Cage 15 Pocket 15a Inner surface 17 Contact area 18 Non-contact area 24 Recess groove

Claims (8)

A ball bearing comprising an outer ring, an inner ring, a plurality of balls disposed between the outer ring and the inner ring, and a cage having a plurality of pockets for holding the plurality of balls, respectively.
The cage pocket has an inner surface formed by a cylindrical surface;
A ball bearing, wherein a concave groove is formed in a non-contact area where the ball does not contact the inner surface formed by the cylindrical surface.   2. The ball bearing according to claim 1, wherein the non-contact region in which the concave groove is formed is located radially inward from the contact region with which the ball contacts. The cage is a ball guide system,
On the inner diameter side end portion of the pocket, a convex portion that protrudes in contact with the ball and restricts the radial movement of the cage is provided,
The ball bearing according to claim 1, wherein the non-contact region in which the concave groove is formed is formed between the contact region and the convex portion.   The ball bearing according to claim 1, wherein the ball bearing is lubricated with grease. The retainer has a pair of annular portions on both sides in the axial direction, and a plurality of pillars connecting the pair of annular portions, and the inner surface of the pocket is formed in a cylindrical shape,
The ball bearing according to claim 1, wherein the recessed groove is formed along a circumferential direction of the pocket. The retainer has an annular portion and a plurality of column portions extending in the axial direction from the annular portion, and the pocket is formed in a cylindrical shape that opens in one axial direction,
The ball bearing according to claim 1, wherein the recessed groove is formed along a circumferential direction of the pocket.   A motor using the ball bearing according to claim 1.   A spindle apparatus characterized by using a ball bearing according to any one of claims 1 to 6 to rotatably support a machine tool spindle.

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