JPH04277314A - Fluid bearing type rotational head cylinder - Google Patents

Abstract

PURPOSE:To provide a fluid bearing type rotational head cylinder used in a video tape recorder or the like, which has a thrust bearing excellent in abrasion- resistance, and a bearing excellent in rotational ability with a low frictional torque. CONSTITUTION:A dynamic pressure fluid bearing is used as a radial bearing 8. A thrust bearing 7 has a shaft 2 whose one end is substantially semi- spherically formed. A thrust pad 4 is abutted against a contact point of the end of the shaft, eccentrically from a shaft center by 15 to 100 micrometers. A fluid bearing rotational head cylinder wherein high accuracy of rotational ability of the radial bearing is maintained and the thrust pivot bearing is provided with sufficient abrasion-resistance is obtained.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to video tape recorders,
This relates to a hydrodynamic rotating head cylinder used in digital audio tape recorders, etc., in which the thrust bearing is a pivot bearing, and a radial bearing is used in combination with a hydrodynamic bearing.

0002

[Prior Art] In recent years, the performance of video tape recorders and the like has been improved, and their rotary drive main shafts have high precision and
There is a demand for bearings that have low friction torque and excellent wear resistance. In order to meet this demand, we have developed a fluid bearing type rotary head cylinder that uses a combination of a radial fluid bearing with excellent centripetal performance toward the shaft center and a thrust bearing with a pivot bearing that has the characteristic of low friction torque due to point contact. It is about to be used.

An example of the above-mentioned conventional fluid bearing type rotary head cylinder will be described below with reference to the drawings. FIG. 5 is a sectional view of a conventional rotary head cylinder. In FIG. 5, 11 is a lower cylinder, and a shaft 12 is fixed at the center. The upper tip 12A of the shaft 12 is machined to have an approximately spherical surface, or has at least a portion of the approximately spherical surface, and this spherical surface abuts on the thrust bearing 14, holds the thrust lubricant 15, and operates the thrust bearing. 1
7 are made up. The thrust receiver 14 is integrally fixed to the end surface of the upper cylinder 13, and the upper cylinder 13 has a bearing hole 13A in the center and is rotatable around the outer circumference of the shaft 12. Dynamic pressure generating grooves 12B, 12 are provided on either the outer circumference of the shaft 12 or the bearing hole 13A of the upper cylinder.
C is provided, and radial lubricants 16A and 16B are held, thereby forming a radial dynamic pressure type fluid bearing 18. 1
Magnetic heads 3B and 13C are fixed to the upper cylinder and are used to record and reproduce signals from a magnetic tape (not shown) or the like. 19 is a motor rotor, and 20 is a motor stator.

The operation of the hydrodynamic bearing rotary head cylinder constructed as described above will be explained below. First, when the motor stator 20 is energized, the motor rotor 19 is connected to the upper cylinder 13 and the magnetic head 1.
3B, 13C, and rotate together with the thrust receiver 14. At this time, the dynamic pressure generation grooves 12B and 12C generate pumping pressure, and the upper cylinder 13 rotates with high performance without contact with the shaft 12 and without rotational runout, and the thrust receiver 14
Although force due to its own weight etc. is applied as shown in E in the figure, the shaft tip 12A
It rotates lightly with small friction torque while making point contact with.

[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 nitrogen. 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 possible to avoid wear of about 5 micrometers from either the thrust receiver 14 or the shaft tip 12 due to poor lubrication. was difficult. However, when this wear occurs as a rotating head cylinder, the magnetic tape (not shown) and the magnetic head 13B
, 13C, which significantly reduces performance, so it must be kept to about 2 microns or less, including initial wear. 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 10 micrometers, making it difficult to stably record and reproduce data using the magnetic head. On the other hand, due to the effect of this shaft runout, the point where the thrust receiver 14 contacts the tip of the shaft is constantly moved during one rotation, so that no concentrated load is applied to the thrust receiver, and the thrust There was relatively little wear on the bearing 17. In comparison, the conventional example shown in Fig. 5 uses a hydrodynamic bearing for 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. It was difficult to prevent wear.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a hydrodynamic bearing type rotary head cylinder having a thrust bearing with excellent wear resistance, low friction torque, and good rotational performance.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the fluid bearing type rotary head cylinder of the present invention uses a hydrodynamic fluid bearing as the radial bearing, and the thrust bearing has one end of the shaft having a substantially spherical tip. The contact point at the tip of this shaft is
The thrust receiver is made to come into contact with the thrust receiver eccentrically by 15 to 100 micrometers from the center of the shaft.

[0008]

[Operation] With the above-described structure, the present invention can provide a hydrodynamic bearing type rotary head cylinder that maintains the rotational performance of the radial bearing with high accuracy and has sufficient wear resistance of the thrust pivot bearing.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid bearing type rotary head cylinder according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a sectional view of a rotary head cylinder according to an embodiment of the present invention. In FIG. 1, 1 is a lower cylinder, and a shaft 2 is fixed at the center. The shaft end surface 2A of the shaft 2 is machined into an approximately spherical surface, or at least partially has an approximately spherical surface, and the center of this spherical surface is located at an angle of 15 mm with respect to the axis of the shaft 3.
-100 micrometer eccentricity. The center of this eccentric spherical surface comes into contact with the thrust receiver 4, and the thrust lubricant 5 is held therein, thereby forming a thrust bearing 7. The thrust receiver 4 is fixed to the end surface of the upper cylinder 3 with screws or the like. The upper cylinder 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 and 2C are provided on either the outer circumference of the shaft 2 or the bearing hole 3A of the upper cylinder.
is provided, and radial lubricant 6A, such as liquid or gas,
6B is held to constitute a radial dynamic pressure type fluid bearing 8. 9 is a motor rotor, and 10 is a motor theta.

The operation of the hydrodynamic bearing rotary head cylinder constructed as described above will be explained below. First, when the motor stator 10 is energized, the motor rotor 9 is moved into the upper cylinder 3 and the thrust receiver 4.
rotates with. At this time, the dynamic pressure generating grooves 2B and 2C generate pumping pressure, and the upper cylinder 3 rotates with high performance without contact with the shaft 2 and without any rotational runout, and the thrust receiver 4 is rotated at F in the figure. As shown, the force applied to the shaft tip 2 is applied by its own weight or the sum of its own weight and the suction force of the motor rotor 9.
It rotates lightly with small friction torque while making point contact with A.

The shaft tip 2A is eccentric by the distance shown in FIG. 2a, but due to this eccentricity, the contact point between the thrust receiver 4 and the shaft tip 2A is shifted by one rotation as shown in FIG. 3c. Since it constantly moves in between, no concentrated load is applied to the shaft tip 2A. Further, when the contact point moves, the thrust lubricant is drawn into the contact point as shown by arrow d in FIG. 4, and good lubrication is achieved, so that wear resistance is greatly improved. In this way, highly accurate positioning is performed between the magnetic tape (not shown) and the magnetic heads 3D, 3E, and good signal recording and reproduction is performed.

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 eccentricity shown in FIG. 2a has no effect if it is 10 microns, and if it exceeds 100 microns, the circumferential speed at the contact point increases 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 (P).
SZ), 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 in the order of aluminum <silicon carbide = silicon nitrogen = sapphire <PSZ = titanium carbide cermet, and by using PSZ or titanium carbide cermet. Furthermore, it becomes possible to guarantee the service life.

Furthermore, as shown in FIG. 1F, in addition to the weight of the rotating body, the suction force of the magnet of the motor rotor 9 is applied to the thrust receiver 4 in the thrust direction, thereby preventing the rotating body from lifting up or vibrating. This results in stable rotation performance.

As described above, according to this embodiment, it is possible to obtain a hydrodynamic bearing type rotary head cylinder that has good lubrication at the contact point of the pivot bearing, has high rotational accuracy, and has excellent wear resistance. Can be done.

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.

[0019] The same thing applies even if the upper cylinder and thrust receiver do not rotate but the shaft rotates.

Note that the same applies even if the spacer 3A is a stepped portion provided integrally with the upper cylinder 3.

[0021]

As described above, according to the present invention, the radial bearing is a hydrodynamic bearing, and the contact point between the shaft tip and the thrust receiver is an eccentric pivot bearing with a distance of 15 to 100 microns from the axis. Good lubrication at points,
A hydrodynamic bearing type rotary head cylinder with high rotational accuracy and excellent wear resistance can be obtained.

[Brief explanation of the drawing]

[Fig. 1] A sectional view of an embodiment of the fluid bearing type rotary head cylinder of the present invention.

[Figure 2] Detailed sectional view of Figure 1

[Figure 3] Cross-sectional view in the bb direction of Figure 2

[Figure 4] Explanatory diagram of the shaft tip

[Fig. 5] Cross-sectional view of a conventional hydrodynamic bearing type rotary head cylinder

[Explanation of symbols] 1 Lower cylinder 2 Shaft 2A Shaft tip 2B, 2C Dynamic pressure generating groove 3 Upper cylinder 3A Bearing hole 3D, 3E Magnetic head 4 Thrust receiver 5 Thrust lubricant 6A, 6B
Radial lubricant 7 Thrust bearing 8 Radial bearing 9 Motor rotor 10 Motor stator

Claims (4)

[Claims] 1. A shaft having a shaft, an upper cylinder rotatably provided with respect to the shaft, and a thrust receiver integrally fixed with the upper cylinder and abutting one end of the shaft, the one end of the shaft being , a substantially spherical surface coated with a liquid or semi-solid lubricant, the center of the spherical surface being eccentric from 15 to 100 micrometers with respect to the center of the axis, and having a magnetic head in the upper cylinder; A hydrodynamic bearing type rotary head cylinder that has a motor that rotationally drives the cylinder or lower cylinder. 2. The fluid bearing rotary head cylinder according to claim 1, wherein the hydrodynamic bearing type rotary head cylinder has a dynamic pressure generating groove in either the outer periphery of the shaft or the bearing hole formed in the center of the upper cylinder. 3. The hydrodynamic bearing rotary head cylinder according to claim 1, wherein the thrust receiver is made of cermet containing titanium carbide or partially stabilized zirconia. 4. The hydrodynamic bearing rotary head cylinder 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 upper cylinder.