JPH03163212A - Dynamic pressure type fluid bearing device - Google Patents

Abstract

PURPOSE:To conduct high speed rotation stably and to securely retain lubricant in a space even at a high speed by providing the space closed between two sets of grooves for generating dynamic pressure having specified depth and specified angles relative to a rotational direction. CONSTITUTION:A groove 3A for generating dynamic pressure is formed on a thrust plate 3 which in contact with the end face 1A of a shaft 1 and fixed to the end face of a sleeve 2, and lubricant 4 is filled in the groove to construct a thrust bearing. Two sets of grooves 2A, 2B for generating dynamic pressure are formed on the inner circumference of the sleeve 2 or the outer circumference of the shaft 1, and a radial bearing filled with the lubricant 4 is constructed. Angles of the grooves 2A, 2B for generating dynamic pressure beta1, beta2 relative to the rotational directions are set less than 20 degrees, the depth of the grooves is set 4mum or more, a space 2E is provided between the two grooves 2A, 2B for generating dynamic pressure and air is filled in the space. The lengths L1, L4 of portions outside the grooves 2A, 2B for generating dynamic pressure are set longer than the lengths L2, L3 toward the space therebetween and the grooves 2A, 2B are formed in an unsymmetrical pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a hydrodynamic bearing device that has excellent high-speed rotation performance and is used in rotary head cylinders of video tape recorders and the like.

2. Description of the Related Art In recent years, in order to improve the performance of video tape recorders and the like, a bearing that can rotate with high precision is required for the rotating main shaft of a rotating head cylinder, and a hydrodynamic bearing has been used.

An example of the conventional hydrodynamic bearing device described above will be described below with reference to the drawings. FIG. 3 is a sectional view of a conventional hydrodynamic bearing device. In FIG. 3, reference numeral 11 is a shaft, which is rotatably fitted together with the sleeve 12. A thrust plate 13 is in contact with the end surface 11A of the shaft 11 and is fixed to the end of the sleeve 12. Thrust plate 13
A dynamic pressure generating groove 13A is provided in the bearing, and a lubricant 14 is applied to form a thrust bearing. Dynamic pressure generating grooves 12A and 12B are provided on the inner periphery of the sleeve 12 or on the outer periphery of the shaft 1, and are filled with a lubricant 14 to form a radial bearing. These dynamic pressure generating grooves have angles of θ1 and θ2 with respect to the rotation direction, and these angles are generally 25 degrees to 40 degrees. The sleeve 12 has ventilation holes 12C. 12D is open.

The operation of the hydrodynamic bearing configured as described above will be described below. First, when the motor (not shown) is energized, the shaft 11 or the sleeve 12 and the thrust plate 1 are connected to each other.
3 starts rotating.

The lubricant 14 generates pressure by the bombing action of the dynamic pressure generating grooves 11A, 12A, and 12B, and rotates without contact. still,
As shown in Japanese Unexamined Patent Publication No. 60-78106, the ventilation hole 12C is for discharging the air in the space 12E when the shaft 11A is inserted into the sleeve 12 and assembled, and the ventilation hole 12D is for controlling the temperature. This is to communicate with the outside air so that the pressure within this space does not change when the pressure changes and the volume of the air in the space 12F changes.

Problems to be Solved by the Invention However, the above configuration has the following problems. In recent years, there has been a demand for hydrodynamic bearings that can rotate at even higher speeds than before, but in conventional hydrodynamic bearings, during high-speed rotation, the hydrodynamic grooves 12A and 12B of the sleeve 12 are lubricated. The lubricant 14 flowing out from the vent hole 12D due to centrifugal force causes the bearing to lack rigidity and run out, which may eventually lead to seizure.

Means for Solving the Problems In order to solve the above-mentioned problems, the hydrodynamic bearing device of the present invention has two sets of hydrodynamic bearings with a depth of 4 microns or more and an angle of less than 20 degrees with respect to the rotation direction. A sealed cavity is provided between the generation grooves, and the outer portions of the two sets of dynamic pressure generation grooves are longer than the length of the sealed cavity side, and are arranged in an asymmetrical pattern. .

Effects of the present invention With the above-described configuration, air can be easily discharged from the hydrodynamic bearing, allowing stable high-speed rotation, and even at high-speed rotation, the lubricant is reliably held in the empty space to prevent it from flowing out to the outside. It is intended to prevent

Embodiment A hydrodynamic bearing device according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view of the device. In FIG. 1, reference numeral 1 denotes a shaft, which is rotatably fitted together with a sleeve 2.

A thrust plate 3 is in contact with the end surface IA of the shaft 1 and is fixed to the end surface of the sleeve 2. A dynamic pressure generating groove 3A is provided in the thrust plate 3, and a lubricant 4 is applied to the thrust plate 3 to protect the thrust bearing. 2 on the inner circumference of sleeve 2 or on the outer circumference of shaft 1.
A set of dynamic pressure generating grooves 2A and 2B are provided and constitute a radial bearing in which a lubricant 4 is applied. This dynamic pressure generating groove 2A,
2B has angles β1 and β2 with respect to the rotation direction as shown in FIG. 1, and these angles are acute angles of less than 20 degrees. Further, the groove depth has a sufficient depth of 4 micrometers or more. The sleeve has a ventilation hole 2C connected to the cavity 20. 2E is a space between the two dynamic pressure generating grooves 2A and 2B, and is sealed with air.

The operation of the hydrodynamic bearing configured as described above will be described below. First, when a motor (not shown) is energized, the shaft 1 or the sleeve 2 and thrust plate 3 begin to rotate. The lubricant 4 is applied to the dynamic pressure generating groove IA. 2A, 2B
The pumping action generates pressure and rotates without contact. Incidentally, the ventilation hole 2C is for discharging air from the space 2E when the shaft IA is inserted into the sleeve 2 and assembled.

In this embodiment, if the temperature increases or the ambient pressure decreases during high-speed rotation, the air trapped in the space 2E tries to escape to the outside, but the two sets of dynamic pressure generating grooves 2A. The angle 2B is an acute angle of less than 20' degrees, and the air is smoothly discharged because there is little resistance to the flow velocity. At this time, if the angle is 20 degrees or more as in the conventional case, it is difficult to exhaust air and stable rotation cannot be performed. Further, since the depth of the grooves 2A and 2B is 4 micrometers or more, the trapped air is more easily discharged more smoothly. One side dynamic pressure generating groove 2
When the depth of A and 2B is 3 microns or less, air is difficult to be discharged. As described above, in this embodiment, since the air is smoothly discharged, the pongee holder is always filled with lubricant and can stably rotate at high speed.

Further, since no ventilation hole is provided in the cavity 2E as in the conventional case, lubricant does not flow out from the ventilation hole.

In addition, in this embodiment, the dynamic pressure generating groove 2A shown in FIG.
length Ll, L2, and length L3 of the dynamic pressure generating groove 2B.
L4 has a relationship of Ll>L2 and L3<L4, respectively, that is, the lengths Ll and L2 of both outer portions of the two sets of dynamic pressure generating grooves 2A and 2B having angles β1 and β2 with respect to the rotation direction , is longer than the lengths L2 and L3 of the void side located in the middle, and has an asymmetrical A-groove pattern. As a result, M in Figure 2,
A gas-liquid boundary layer between the air and the lubricant 4 is formed at the location indicated by N, and the lubricant 4 is retained in the sealed space 2E without leaking outside, making it difficult for the lubricant 4 to run out and making it stable. It can rotate at high speed.

As described above, according to this embodiment, two sets of dynamic pressure generating grooves 2A. By providing a sealed space between the two sets of dynamic pressure generating grooves 2A. 2B has an asymmetrical pattern in which the lengths of the outer parts Ll and L4 are longer than the lengths L2 and L3 of the sealed space side, so that the lubricant 4 does not leak out and stable high-speed rotation is achieved. A dynamic pressure fluid bearing that can be used is obtained.

Note that the end surface IA is a part of a spherical surface, and may include a pivot bearing.

Effects of the Invention As described above, the present invention provides a sealed cavity between two sets of dynamic pressure generating grooves having a depth of 4 microns or more and an angle of less than 20 degrees with respect to the flow velocity. The air in the empty space can be smoothly exhausted. In addition, the two sets of dynamic pressure generating grooves have an asymmetrical pattern in which the length of the outer part is longer than the length of the sealed cavity side, so that there is no lubricant leakage and stable high-speed rotation can be achieved. A pressure fluid bearing is obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hydrodynamic bearing device according to an embodiment of the present invention, FIG. 2 is an explanatory view of lubricant retention, and FIG. 3 is a sectional view of a conventional hydrodynamic bearing device. 1...Shaft, 2...Sleeve, 2A, 2
B...Dynamic pressure generating groove, 2E...Vacancy, 4
······lubricant.

Claims (2)

[Claims] (1) It has a shaft and a sleeve fitted to be rotatable relative to the shaft, and at least two sets of dynamic pressure generating grooves are provided on either the outer periphery of the shaft or the inner periphery of the sleeve. a lubricant such as oil or grease is held between the shaft and the sleeve, a sealed cavity is formed between the two sets of dynamic pressure generating grooves, and the dynamic pressure generating groove has a depth. 4
A hydrodynamic bearing device characterized in that the angle is an acute angle of less than 20 degrees with respect to the rotational direction of the shaft or sleeve, and the angle is a micrometer or more. (2) The dynamic pressure generating groove has an asymmetrical pattern in which the length of the outer part is longer than the length of the sealed cavity side.
The hydrodynamic bearing device described above.