JPH04231718A - Compound fluid bearing device - Google Patents

Abstract

PURPOSE:To provide a compound bearing device excellent in the wear resistance of a thrust bearing and rotating performance and having low frictional torque. CONSTITUTION:A dynamic pressure type fluid bearing is used for a radial bearing 8. A thrust bearing 7 is provided with a nearly spherical shaft end 2A and with a thrust receiver 4 tilted by 2/1000-12/1000 relative to a plane normal to a shaft 2. This provides a compound fluid bearing device having sufficient wear resistance of the thrust bearing 7 while maintaining high accuracy rotating performance of the radial bearing 8.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION The present invention relates to a composite fluid bearing device used in video tape recorders, disk drives, etc., in which the thrust bearing is a pivot bearing and a radial bearing is combined with a hydrodynamic shaft. It is something.

0002

[Prior Art] In recent years, the performance of video tape recorders, disk drives, etc. has been improved, and their rotational drive shafts are equipped with bearings that have high precision, low friction torque, and excellent wear resistance. In response to this demand, a composite fluid bearing is used, which combines a radial fluid bearing with excellent centripetal performance to the shaft center and a thrust bearing with a pivot bearing, which has low friction torque due to point contact. .

An example of the above-mentioned conventional composite hydrodynamic bearing device will be described below with reference to the drawings. FIG. 5 is a sectional view of a conventional composite hydrodynamic bearing device. In FIG. 5, 11 is a frame, and a shaft 12 is fixed at the center. The upper end surface of the shaft 12 is machined into a roughly spherical surface, contacts the thrust receiver 14, holds the thrust lubricant 15, and constitutes a thrust bearing 17. Thrust receiver 1
4 is fixed to the end surface of the disk 13 with screws or the like. The disk 13 has a bearing hole 13A in the center, and the shaft 12
It is rotatably provided around the outer periphery of the Dynamic pressure generating grooves 12B and 12C are provided on either the outer circumference of the shaft 12 or the bearing hole 13A of the disk, and radial lubricants 16A,
16B is held to constitute a radial dynamic pressure type fluid bearing 18. 19 is a motor rotor, and 20 is a motor stator.

The operation of the composite hydrodynamic bearing device constructed as described above will be explained below. First, when the motor stator 20 is energized, the motor rotor 19 rotates together with the disk 13 and the thrust receiver 14 . At this time, the dynamic pressure generation grooves 12B and 12C generate pumping pressure, and the disk 13 rotates with high performance without contact with the shaft 12 and without rotational runout, and the thrust receiver 14 is rotated as shown in E in the figure. Although force is applied due to its own weight, etc., it rotates lightly with small friction torque while making point contact with the shaft tip 12A.

[0005]

However, the above configuration has the following problems. In order to prevent wear of the thrust bearing 17, the shaft 12 must be made of hard steel, and the thrust receiver 14 must be made of an expensive material such as silicon carbide or silicon nitride. However, the wear resistance is still insufficient, and the shaft tip 12
The thrust lubricant 15 cannot enter the point contact area between A and the thrust receiver 14, and it is necessary to avoid wear of about 5 micrometers from either the thrust receiver 14 or the shaft tip 12 due to poor lubrication. was difficult. On the other hand, in another conventional example (not shown) in which a ball bearing or an oil-impregnated bearing is used as a radial bearing, the rotation accuracy in the radial direction is poor and the shaft runout is about 20 micrometers. Uke 1
The point where 4 abuts on the tip of the shaft is constantly moved during one rotation, no concentrated load is applied to the thrust bearing, and wear on the thrust bearing 17 is relatively small. In comparison, the conventional example shown in Fig. 5 uses a hydrodynamic bearing as the radial bearing, so although the rotational performance is good, the thrust bearing 14 always comes into contact with the same point on the shaft tip 12A, so the thrust bearing Preventing wear was difficult.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a composite hydrodynamic bearing device that has a thrust bearing with excellent wear resistance, low friction torque, and good rotational performance.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the composite hydrodynamic bearing device of the present invention uses a hydrodynamic bearing as the radial bearing, and the thrust bearing has one end of the shaft having a substantially spherical shape. , 2/1000 to 1 from the plane perpendicular to the axis
It is tilted by 2/1000.

[0008]

According to the present invention, with the above-described configuration, it is possible to obtain a composite hydrodynamic bearing device having sufficient wear resistance of the thrust bearing while maintaining high rotational performance of the radial bearing.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A composite hydrodynamic bearing device according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 4. Figure 1
FIG. 2 is a sectional view of a composite fluid bearing according to an embodiment of the present invention.

In FIG. 1, 1 is a frame, and an axis 2
is fixed in the center. The upper end surface of the shaft 2 is machined into an approximately spherical surface, or at least a portion thereof has an approximately spherical surface, and the vicinity of the center of this spherical surface is in contact with the thrust receiver 4, and the thrust lubricant 5 is held, so that the thrust A bearing 7 is configured. The thrust receiver 4 is fixed to the end surface of the disk 3 with screws or the like. The disk 3 has a bearing hole 3A in the center and is rotatably provided with respect to the shaft 2. 3C is a ventilation hole. Dynamic pressure generating grooves 2B, 2C are provided on either the outer circumference of the shaft 2 or the bearing hole 3A of the disk, and radial lubricants 6A, 6B such as liquid or gas are provided.
is held to constitute a radial dynamic pressure type fluid bearing 8. 9 is a motor rotor, and 10 is a motor stator. In FIG. 2, the thrust receiver 4 is fixed at an angle with respect to the shaft 2 by inserting a spacer 3B, etc., as shown in a in the figure. This inclination is 2/1000 to 12/1000 with respect to the plane perpendicular to the axis of axis 2.
has an angle of This inclination corresponds to angle G in FIG.

The operation of the composite hydrodynamic bearing device constructed as described above will be explained below. First, when the motor stator 10 is energized, the motor rotor 9 rotates together with the disk 3 and the thrust receiver 4. At this time, the dynamic pressure generation grooves 2B and 2C generate pumping pressure, and the disk 3 rotates with high performance without contact with the shaft 2 and without any rotational runout, and the thrust receiver 4 is rotated as shown in F in the figure. Although it is subjected to its own weight or a force that is the sum of its own weight and the suction force of the motor rotor 9, it rotates lightly with a small frictional torque while making point contact with the shaft tip 2A.

The thrust receiver 4 is installed with an inclination as shown in FIG. Since it constantly moves during rotation, no concentrated load is applied to the shaft tip 2A. Also, when the contact point moves,
As shown by the arrow d in the figure, the thrust lubricant is drawn into the contact point, providing good lubrication and greatly improving wear resistance.

Furthermore, in the present invention, even if an oil-impregnated bearing is used instead of a hydrodynamic bearing as the radial bearing, the effect of improving the wear resistance of the thrust bearing can be obtained.

Further, the amount of inclination shown in FIG. 2A has no effect when the angle is less than 2/1000;
If it exceeds 00, the circumferential speed at the contact point becomes faster and wear increases.

Further, in the present invention, the shaft is made of hard martensitic hardened stainless steel, and the thrust bearing is made of cermet (composite metal) mainly composed of titanium carbide or partially stabilized zirconia (composite metal).
PSZ), and its surface roughness is precisely finished to 0.2 microns or less. As the thrust lubricant 5, ester oil, alpha olefin oil, fluorine-based lubricant, or the like is used.

According to the present invention, the wear resistance of the thrust bearing is such that alumina<silicon carbide=silicon nitride=sapphire<
PSZ = titanium carbide cermet order PS
By using Z or titanium carbide cermet, it is possible to further guarantee the life span. In addition, as shown in Fig. 1 F, by applying the suction force of the magnet of the motor rotor 9 to the thrust receiver 4 in addition to the weight of the rotating body in the thrust direction, lifting and vibration of the rotating body are prevented and stability is achieved. It provides excellent rotational performance.

As described above, according to this embodiment, it is possible to obtain a composite hydrodynamic bearing device that has good lubrication at the contact points of the pivot bearing, has high rotational accuracy, and has excellent wear resistance. .

Note that the dynamic pressure generating grooves 2B and 2C may be located not on the outer periphery of the shaft but on the inner periphery of the bearing hole. Also, the same problem occurs even if the disk and thrust receiver do not rotate, but the shaft rotates. Further, the same applies even if the spacer 3A is a stepped portion provided integrally with the disk 3.

[0019]

As described above, according to the present invention, the radial bearing is a hydrodynamic bearing, the thrust bearing is made of a shaft having an approximately spherical shape, and the thrust bearing is in contact with the tip of the shaft, and the thrust bearing is attached to the surface perpendicular to the axis. against 2/1000~12/10
Tilt by 00 to improve lubrication at the contact point,
A composite hydrodynamic bearing device with high rotational accuracy and excellent wear resistance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a composite hydrodynamic bearing device according to an embodiment of the present invention.

[Figure 2] Detailed sectional view of Figure 1

[Fig. 3] Cross-sectional view in the b-b direction of Fig. 2

[Fig. 4] Configuration diagram of the composite hydrodynamic bearing device in this embodiment

[Fig. 5] Cross-sectional view of a conventional composite hydrodynamic bearing device

[Explanation of symbols]

2 axis 2A Shaft tip 2B, 2C Dynamic pressure generation groove 3 Disc 4 Thrust receiver 6A, 6B Radial lubricant

Claims (4)

[Claims] 1. A shaft having a shaft, a disk rotatably provided with respect to the shaft, and a thrust receiver integrally fixed with the disk and abutting one end of the shaft, the one end of the shaft having a substantially spherical surface. A composite hydrodynamic bearing device in which a liquid or semi-solid lubricant is applied, and the thrust receiver is fixed at an angle of 2/1000 to 12/1000 with respect to a plane perpendicular to the shaft center. 2. The composite hydrodynamic bearing device according to claim 1, further comprising a dynamic pressure generating groove on either the outer periphery of the shaft or the bearing hole formed in the center of the disk. 3. The composite hydrodynamic bearing device according to claim 1, wherein the thrust bearing is made of cermet containing titanium carbide or partially stabilized zirconia. 4. The composite hydrodynamic bearing device according to claim 1, wherein the thrust receiver is pressed against one end of the shaft by the suction force of a magnet of a motor rotor integrally fixed to the disk.