JP2000266060A - Ball bearing and motor for driving memory disk therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball bearing and a motor for driving memory disk therewith capable of increasing its life by improving lubricity without problems such as reduction in stiffness, noise generation, and increase in friction torque. SOLUTION: This ball bearing 1 is formed so that an annular rolling element retainer 4 involving a plurality of lines of accommodating parts 10 containing a rolling element 7 circumferentially may be disposed between an inner ring 2 and an outer ring 3 which is cylindrical and disposed concentrically with each other, and a plurality of rolling elements 7 rotatably-retained by the accommodating part 10 with lubricant may be disposed so as to come into rolling contact with the inner ring 2 and outer ring 3 respectively, wherein a contact part on which the rolling member 7 comes into contact with the containing part 10 is orthogonal to a self-rotating shaft S of the rolling element 7, and a plane including both parts 17, 18 to be transferred of which the rolling element 7 comes into rolling contact with the inner ring 2 and outer ring 3 is intersected with the inner surface of the containing part 10 to form an arc shape. A lubricant retaining groove 19 is formed along the arc. The objective motor for diving a memory disk is provided the ball bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball bearing used for OA equipment, home electric appliances, and the like, and a motor for driving a recording disk having such a ball bearing. Ball bearings and recording disk drive motors.

[0002]

2. Description of the Related Art In a known ball bearing, an annular rolling element retainer is interposed between an inner ring and an outer ring which are cylindrical and arranged concentrically with each other. Spherical rolling elements (balls) are rotatably held in a plurality of accommodation sections, and both the inner ring and the outer ring are rotatable with each other. The housing portion has a spherically concave surface without any irregularities, and is filled with a lubricant to facilitate the rolling of the rolling element. Such ball bearings are mainly applied to motors in a wide range of equipment such as OA equipment to home appliances.

[0003] In recent years, as ball bearings have been reduced in size and power consumption have been promoted, it has been required to reduce rotation torque in order to reduce power consumption in addition to miniaturization. It has become To meet these demands,
For example, means for reducing the diameter of the ball inside the ball bearing or reducing the preload applied to the ball bearing are conceivable. The preload is a pressure applied to the inner ring or the outer ring in the axial direction for the purpose of increasing the rigidity of the ball bearing.

[0004] However, such means reduces not only the rotational torque but also the rigidity of the ball bearing itself, causing rattling and making it difficult to meet the performance required of the equipment used.

Another means for reducing the rotational torque without reducing the rigidity of the ball bearing is to reduce the amount by focusing on grease sealed as a lubricant in the ball bearing.
Alternatively, it is conceivable that the viscosity of the base oil that is contained in grease and performs a lubricating action is reduced. However, even with such a means, when the amount of grease is reduced, the grease is insufficient at the contact portion of the ball (the portion where the ball contacts the accommodating portion of the rolling element retainer) at an early stage, and the grease is removed. Depletion may occur and shorten the life. On the other hand, when the viscosity of the grease base oil is reduced, the oil film thickness becomes small, and the lubricating action becomes insufficient. In addition, the inner surface of the housing for holding the ball of the rolling element retainer is formed in a spherical curved surface slightly larger than the diameter of the ball, and the ball is subjected to an axial load, that is, a preload, on the inner ring or the outer ring. The rolling of the inner ring and the outer ring causes the lubricant of each rolling portion on both sides of the ball to be scraped off by the contact portion of the rolling element retainer. In any case, the friction torque of the ball bearing was increased due to insufficient holding of the lubricant, and the life was shortened due to the occurrence of seizure and noise and leakage of the lubricant.

[0006]

By the way, as a ball bearing for improving the holding force of the lubricant, for example, Japanese Patent Application Laid-Open No. Hei 8-1
Japanese Patent No. 84318 proposes an inner surface of a receiving portion such as a circular hole for holding a ball in a rolling element retainer interposed between an inner ring and an outer ring, which is formed into an uneven surface in which parallel narrow grooves are densely arranged. Have been. According to the gazette, the rolling element retainer of the ball bearing is made of synthetic resin and needs to prevent deformation due to heat generation. Therefore, by forming an uneven surface, the contact area between the rolling element retainer and the ball is reduced. The main purpose is to reduce the heat generation due to the sliding contact between the rolling element retainer and the ball, but by providing the narrow grooves, the holding power of the lubricant is increased and the lubrication performance life is improved. Has been described.

The narrow groove disclosed in the publication is a groove for reducing the contact area with the ball or for increasing the holding force of the lubricant. In this way, the capacity of holding the lubricant is increased, the holding force of the lubricant is increased, and the contact area of the inner surface of the housing portion with which the ball contacts can be reduced.

However, such a configuration may be able to reduce the contact area between the ball and the accommodating portion of the rolling element retainer and increase the holding force of the lubricant, but it is not possible to increase the lubrication force of the ball on the inner surface of the accommodating portion. In some cases, the lubricant was distributed irrespective of the contact area. It is desirable that the lubricant be concentrated at the contact portion of the housing portion in order to maintain the lubricating performance. However, in the configuration of the publication, even though the lubricant is not insufficient, if the lubricant spreads to the contact portion In the end, it is necessary to fill the lubricant more than necessary, which causes a problem such as increasing the rotational torque or leaking the lubricant.

Of course, when such a ball bearing is applied to a device, the ball bearing constitutes a main component of the device, and therefore, malfunctions, repairs, or replacements of the device due to problems such as increased power consumption and leakage of lubricant occur. I do. For example, in the case of a recording disk drive motor such as a hard disk that requires high precision, the occurrence of noise and lubricant leakage is a serious problem in a hard disk drive, and the application of such a ball bearing is not reliable. Some improvement is needed.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a lubrication system without causing problems such as a reduction in rigidity, generation of noise, or an increase in friction torque. An object of the present invention is to provide a ball bearing capable of achieving a longer life by improving performance and a recording disk drive motor provided with the same.

[0011]

In order to achieve the above object, a ball bearing of the present invention accommodates a rolling element between an inner ring and an outer ring which are cylindrical and concentrically arranged with each other. An annular rolling element retainer in which a plurality of housing portions are arranged in the circumferential direction is interposed, and a plurality of rolling elements rotatably held in the housing portion together with the lubricant so as to rollly contact the inner ring and the outer ring, respectively. In the ball bearing that is arranged, a contact portion of the housing portion where the rolling element contacts is orthogonal to a rotation axis of the rolling element, and a plane including both transfer portions where the rolling element is in rolling contact with the inner ring and the outer ring. An arc formed by intersecting the inner surface of the housing portion, and a lubricant holding groove is formed along the arc.

[0012] In this ball bearing, since the contact portion with the rolling element in the accommodating portion of the rolling element retainer is provided with the lubricant holding groove along the arc, that is, along the rotation locus, the lubricant is supplied into the groove. In addition to simply maintaining the function, the lubricant is concentrated on the contact area so that it can be used to the maximum with a small amount, so that the friction torque is dramatically reduced without increasing the amount of lubricant. In addition, seizure and noise due to poor lubrication can be reliably prevented for a long period of time, and the life can be extended. Further, since the lubricant holding groove is formed only at a minimum necessary portion, no abnormal noise is generated, and molding can be easily performed. The lubricant holding groove may be arranged on an arc that is a rotation locus, or may be arranged off the arc.

[0013] In the ball bearing of the present invention, the lubricant holding groove has a plurality of V-shaped grooves positioned on a line passing through a portion that rotates while being in contact with the two rolling portions of the rolling element;
It is preferable that the tip of the bent portion of the V-shaped groove is formed so as to face the rotation direction of the rolling element.

Thus, in the lubricant holding groove, the lubricant in the V-shaped groove flows toward the center (near the bent portion) as the rolling element rotates, and the surface of the rolling element and the V-shaped groove are separated. The pressure of the lubricant collected during the period increases, and a dynamic pressure is generated.
Therefore, since the lubricant can be efficiently concentrated on the portion of the rolling locus of the rolling portion between the inner ring and the outer ring in the rolling element, the friction torque is reduced, and the lubricating performance is further improved, and the rolling performance is further improved. The rolling of the moving body is remarkably stabilized. Further, since the lubricant holding groove is formed regularly along the rotation direction of the rolling element, no noise is generated. Further, since only a small amount of lubricant is required, there is no fear of leakage.

The recording disk drive motor according to the present invention comprises a stationary member, a rotating member rotatable relative to the stationary member, and the rotating member interposed between the rotating member and the stationary member. A ball bearing for rotatably holding a member to the stationary member, wherein the ball bearing of the present invention is used as the ball bearing.

In this recording disk drive motor, a lubricant is applied to a rolling element holding surface of a rolling element retainer of a ball bearing, through which a portion of a rolling trajectory that comes into contact with both rolling portions of an inner ring and an outer ring of a rolling element passes. Efficient concentration reduces friction torque dramatically, which reduces power consumption,
The rotation of the rolling elements is stabilized, so that noise can be reduced. In addition, seizure due to poor lubrication can be reliably prevented over a long period of time due to the remarkable improvement in the lubrication performance of the ball bearing, and the life can be extended.

[0017]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 are longitudinal sectional views showing a ball bearing 1 according to an embodiment of the present invention. FIG. Each state of the arrangement is shown, and when it is attached to the lower side, it is attached to the upper side in an arrangement that is upside down from the attached state.

In these figures, the ball bearing 1 is provided as a rolling element on a ball retainer (rolling element retainer) 4 between an inner ring 2 and an outer ring 3 which are cylindrical and arranged concentrically. Balls 7 made of a plurality of steel balls rotatably held at equal intervals in the direction are interposed. Ball retainer 4
As shown in the perspective view of FIG. 3, a plurality of pairs of holding pieces 9 facing each other are provided on one end face of a cage body 8 formed in an annular shape. Between the opposing surfaces of the pair of holding pieces 9, 9, there is formed a housing portion 10 having a spherical shape and a diameter slightly larger than the diameter of the ball 7. The plurality of balls 7 are individually rotatably held in the respective accommodating portions 10, and as shown in FIGS. 1 and 2,
The portions protruding from both sides from the housing portion 10 are in contact with the spherically concave rolling surfaces 11 and 12 of the inner ring 2 and the outer ring 3 so as to be in rolling contact therewith. The space between the inner ring 2 and the outer ring 3 on the opening side of the housing portion 10 of the ball retainer 4 in the ball bearing 1 is sealed with a sealing material 15.

When the upper and lower ball bearings 1 and 1 are attached, generally, the outer rings 3 of the upper and lower ball bearings 1 and 1 are fixed to the inner surface of the rotating body 14 by means of an adhesive or the like. The inner ring 2 of the upper ball bearing 1
As shown by arrows in FIG. 1, the inner ring 2 of the lower ball bearing 1 is fixed with an adhesive while applying a biasing force downward (axially) along the axis of the fixed main shaft 13. As shown by the arrows in FIG. 2, the ball bearings 1 and 1 are fixed by applying an urging force in an upward direction (axial direction) along the axis of the fixed main shaft 13 with an adhesive. Axial load (preload)
Is provided.

Thus, the ball 7 of the upper ball bearing 1
Is a rolling part 1 which is in contact with the rolling surface 11 of the inner ring 1 at an upper position.
Rolling part 1 that contacts below 7 with rolling surface 12 of outer ring 3
8 and sandwiched. On the other hand, the ball 7 of the lower ball bearing 1
Is a rolling part 1 that rolls below the rolling surface 11 of the inner ring 1
Rolling part 1 that rolls up against rolling surface 12 of outer ring 3
8 and sandwiched. As shown in FIGS. 1 and 2, the rolling portions 17 and 18 are provided with rolling surfaces 11 and 12 and a ball 7 having different curvatures.
Is the trajectory drawn by the contact point with the spherical surface on the inner ring 2 and the outer ring 3,
It becomes a circle. By applying a predetermined preload to the ball 7 as described above, the rigidity of the ball bearings 1 and 1 is improved and rattling is prevented, and smooth rotation of the rotating body 14 is ensured.

As the outer ring 3 rotates integrally with the rotating body 14, the ball 7 includes the inner ring 2 and the outer ring 3 shown in FIGS.
Ball 7 perpendicular to the straight line Q connecting the rolling parts 17 and 18 of the ball 7
Spindle 13 while rotating around axis S passing through the center of
Revolve around the axis L. On the other hand, as shown in an enlarged view of a part of the ball retainer 4 in FIG. 4, the accommodation portion 10 of the ball retainer 4 has a portion (rotation locus) that rotates while being in rolling contact with the rolling portions 17 and 18. A plurality of V-shaped grooves 19a are formed on a line T (arc) through which the lubricant-holding groove 19 passes. The part where the rotation locus is located in the accommodation part 10 is a contact part with which the ball 7 contacts.
The line T is formed by cutting a spherical surface of the housing portion 10 with a straight line Q orthogonal to the axis S, and forms a circular arc on the pair of holding pieces 9. The tip of the bent portion of the V-shaped groove 19a is the ball 7
Is oriented in the direction of rotation. Therefore, the lubricant holding groove 19 is
The ball 7 is arranged in parallel along the plane including the straight line Q.
Are formed in such a direction as to generate a dynamic pressure between them.

For example, FIG. 4 illustrates a case where the outer ring 3 rotates in the direction of the arrow R and the ball 7 rotates in the direction of the arrow P. Therefore, as shown in FIG. 3, the two surfaces of the ball holding surface 10 facing each other are provided with the ball 7.
Since the directions in which they move while rolling are opposite to each other, a plurality of lubricant holding grooves 19 are formed in an arrangement in which the V-shape is opposite to each other.

The lubricant holding groove 19 of the ball bearing 1 is provided in the housing 10 of the ball retainer 4 along the rotation locus of the ball 7 in contact with the rolling portions 17 and 18 of the inner ring 2 and the outer ring 3.
, Respectively.
This is completely different from the one having the function of merely holding the lubricant on the ball holding surface 10 as disclosed in Japanese Patent No. 4318, and is different from the rolling parts 17 and 18, that is, the rolling ball 7.
The lubrication performance can be significantly improved.

In addition, the lubricant holding groove 19 is formed as a plurality of V-shaped grooves 19a, and the bent portion thereof is rotated to contact the rolling portions 17, 18 of the ball 7 between the inner ring 2 and the outer ring 3. The tip of the bent portion of the V-shaped groove 19a is formed so as to match the line T passing through the trajectory and to face the ball 7 in the rotation direction. Therefore, in the lubricant holding groove 19, the lubricant in each V-shaped groove 19 a flows toward the bent portion side as the ball 7 rotates, and the ball 7 and the V-shaped groove 1 a
9a and the pressure of the lubricant collected between them increases, and a dynamic pressure is generated. Therefore, the lubricant is effective for the rotation trajectory of the rolling portions 17, 18 between the inner ring 2 and the outer ring 3 in the ball 7,
In addition, since the lubrication performance can be efficiently concentrated, the lubrication performance is dramatically improved, and the rolling of the ball 7 is remarkably stabilized. The angle of the V-shaped groove 19a is not limited as long as the tip of the bent portion is oriented in the rotation direction of the ball 7.

For this reason, the ball bearing 1 is provided at a location where the rotating portion of the ball retainer 4 that rotates while being in rolling contact with the rolling portions 17 and 18 of the ball 7 that requires the most lubricant is passed. Since the lubricant can be concentrated and held, the lubrication performance is further improved with a small amount of the lubricant. Further, the frictional torque of the ball bearing 1 can be reduced even if a preload is applied without impairing the rigidity, and the occurrence of seizure due to poor lubrication can be reliably prevented for a long period of time, and the life of the ball bearing 1 can be extended.

As described above, in the ball bearing 1, since the internal lubricant can be used to the maximum extent, the rotational torque can be reduced without lowering the rigidity. The desired purpose can be achieved without changing the specifications of the lubricant, such as reducing the viscosity or reducing the viscosity of the base oil. In addition, the lubricant holding groove 19 can be formed at the same time when the ball retainer 4 is manufactured with a mold, and the subsequent assembling process is the same as that of an existing ball bearing, and the number of processes is not increased, so that the manufacturing cost is reduced. Does not rise significantly.

FIG. 5 is a longitudinal sectional view showing a recording disk driving motor constituted by using the above-described ball bearing 1. As shown in FIG. This recording disk is a hard disk. In the figure,
A fixed shaft 21 made of a ferromagnetic material is fixed to a thick base portion 22 provided at a central portion of a motor bracket 20 serving as a motor base body by press-fitting means. 1 and 2 on the outer peripheral surface.
The inner cylindrical wall portion 24 of the cylindrical rotor hub 23 is rotatably supported via a pair of upper and lower ball bearings 1, 1 shown in FIG. The respective outer rings 3 are bonded to the inner peripheral surface of the support cylinder wall portion 24 in a state where the respective ball bearings 1 and 1 are maintained at a mutual interval in the axial direction with an annular spacer member 27 interposed therebetween. The inner ring 2 is adhered to the outer peripheral surface of the fixed shaft 21 in a state where a preload is applied in the directions shown in FIGS.

At the outer peripheral edge of the motor bracket 20,
An annular support projection wall 29 having a step portion 28 is integrally formed upward. The stator 30 in which the coil 32 is wound around the stator core 31 is fixed to the stepped portion 28 of the support projection wall 29 by being externally fitted thereto, and is disposed concentrically with the fixed shaft 21. A cylindrical rotor magnet 34 is internally fitted and fixed to the inner peripheral surface of the outer cylindrical wall portion 33 of the rotor hub 23, and is opposed to the stator core 31 with a gap in the radial direction. Further, a flange portion 37 for supporting a recording disk (not shown) externally fitted to the outer cylindrical wall portion 33 is provided on an outer peripheral portion of the outer cylindrical wall portion 33. A magnetic fluid seal device 39 is fitted into the ball bearing insertion hole 38 in the rotor hub 23, and the magnetic fluid seal device 39 seals the space between the rotor hub 23 and the fixed shaft 21 so that the ball bearing 1, 1 This prevents the lubricant from scattering and the unclean air from scattering into the disk chamber.

The motor comprises a coil 32 of the stator 30
, A magnetic action occurs between the stator 30 and the rotor magnet 34, and the rotor hub 23 uses the fixed shaft 21 as a rotation support shaft to rotate the pair of ball bearings 1, 1.
Rotate through. This recording disk drive motor is particularly required to have low power consumption, low noise, and a long life. However, the use of the ball bearings 1 and 1 whose friction torque is remarkably reduced as described above consumes less power. The electric power is reduced, and both rolling portions 1 of the inner ring 2 and the outer ring 3 in the ball 7
Since the lubricant is efficiently concentrated in the accommodating portion 10 through which the rotation trajectories that contact the rolling bearings 7 and 18 pass, the rolling of the ball 7 can be stabilized, noise can be reduced, and the lubrication performance of the ball bearing 1 is remarkably improved. By the improvement of the lubrication, the occurrence of seizure due to poor lubrication can be reliably prevented for a long period of time, and the life can be extended. Further, since a small amount of the lubricant is sufficient, the lubricant does not leak. Therefore, this motor becomes a high-performance recording disk drive motor by applying the above-described ball bearing.

Although one embodiment according to the present invention has been described above, the present invention is not limited to this.
That is, for example, the lubricant holding groove is arranged on the line T which is the rotation locus in the above description, but is not limited to this line, and may be arranged along this line as a reference. Further, each of the lubricant holding grooves of the above-described ball bearing is formed of a plurality of V-shaped grooves so as to generate a dynamic pressure, but may be a groove shape other than the V-shaped groove. Further, for example, a groove that does not actively generate dynamic pressure may be used as an annular groove. In any case, the groove may be located on the passing line of the rotation trajectory that comes into contact with both rolling portions 17 and 18 of the ball. In addition, although the one using a sphere as the rolling element is shown, other elements can be applied.

[0032]

As described above, according to the ball bearing of the present invention,
Since a plurality of lubricant holding grooves are arranged in the accommodating portion of the ball retainer along the rotation locus of rolling contact with both the inner ring and the outer ring rolling portions of the ball, the lubricating agent is different from the conventional lubricating groove. Not just to secure the
Since the internal lubricant can be effectively concentrated on the rolling parts and can be used to the maximum extent, even if a preload is applied to a sufficient degree of rigidity, friction torque will be significantly reduced and noise will be reduced. The occurrence of seizure due to the occurrence or poor lubrication can be reliably prevented for a long period of time, and the life can be extended. Further, since only a small amount of the lubricant is required, leakage of the lubricant can be prevented.

Further, according to the recording disk drive motor of the present invention, since it is constituted by using the ball bearing of the present invention in which the friction torque is remarkably reduced, the power consumption can be reduced, and the inner and outer rings of the ball can be reduced. The lubricant is efficiently concentrated on the ball holding surface through which the part of the rotation trajectory that makes contact with both rolling parts passes, so that ball rolling can be stabilized and noise can be reduced, and the lubrication performance of ball bearings By the remarkable improvement, the occurrence of burn-in due to poor lubrication can be reliably prevented over a long period of time, and the life can be extended, thereby satisfying the high-performance requirements for recording disk drive.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a ball bearing according to one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a ball bearing showing an embodiment in which the ball bearing is installed at a lower portion when two ball bearings are provided as a pair.

FIG. 3 is a perspective view showing a ball retainer in the ball bearing according to the first embodiment.

FIG. 4 is an enlarged perspective view of a part of the ball retainer according to the first embodiment.

FIG. 5 is a longitudinal sectional view showing a recording disk drive motor according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball bearing 2 Inner ring 3 Outer ring 4 Ball retainer 7 Ball 10 Housing part 13 Fixed main spindle (stationary member) 14 Rotating body (Rotating member) 17 Rolling part between ball and inner ring 18 Rolling part between ball and outer ring 19 Lubrication Agent holding groove 19a V-shaped groove 21 Fixed shaft (stationary member) 23 Rotor hub (rotating member)

Claims (3)

[Claims] 1. An annular rolling element retainer in which a plurality of accommodating portions for accommodating rolling elements are arranged in a circumferential direction between an inner ring and an outer ring which are cylindrical and arranged concentrically with each other, In a ball bearing in which a plurality of rolling elements rotatably held together with a lubricant in the housing portion are arranged so as to be in rolling contact with the inner ring and the outer ring, respectively, a contact portion with which the rolling elements in the housing portion contact Is an arc formed by intersecting a plane that is orthogonal to the rotation axis of the rolling element and that includes the transfer portions where the rolling element rolls into contact with the inner ring and the outer ring intersects the inner surface of the housing section. A ball bearing, wherein a lubricant holding groove is formed along the ball bearing. 2. The lubricant holding groove according to claim 1, wherein a plurality of V-shaped grooves are located, and a tip of a bent portion of the V-shaped groove is formed in a direction of rotation of the rolling element. Become a ball bearing. 3. A stationary member, a rotating member rotatable relative to the stationary member, and a rotating member interposed between the rotating member and the stationary member for rotatably holding the rotating member on the stationary member. 3. The motor for driving a recording disk according to claim 1, further comprising: a ball bearing configured to drive the recording disk. 4.