JPH028511A - Fluid bearing device - Google Patents

Abstract

PURPOSE:To maintain normal rotation preventing a shaft and a thrust receiver from causing their seizure by providing a spiral groove in one of the shaft and the thrust receiver, in the case of a fluid bearing device for a video tape recorder. CONSTITUTION:A lubricant 5 is provided, being interposed in a fine clearance between a shaft 2 and a sleeve 3 and in a fine clearance between the shaft 2 and a thrust receiver 6. The thrust receiver 6 is fixed to the sleeve 3, having a spiral groove 6a in a surface opposed facing to an upper end surface 2b of the shaft 2, and the thrust receiver 6 consists of material of silicon carbide. Thus, the shaft and the thrust receiver can be prevented from causing their seizure so that normal rotation can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a hydrodynamic bearing device that can be used in a rotating head drum device of a video tape recorder.

BACKGROUND OF THE INVENTION FIG. 4 is a cross-sectional view of a rotary head drum device using a conventional hydrodynamic bearing device, and FIG. 6 is an enlarged cross-sectional view of the main part of FIG. 4.

In FIGS. 4 and 6, 1 is a fixed drum that guides the magnetic tape, 2 is a shaft made of stainless steel,
It has Heringbo-ni/type grooves 2a processed, for example, by etching, at two locations on the upper and lower outer circumferential surfaces in the axial direction,
It is press-fitted coaxially into the center of the fixed drum 1.

3 is a sleeve that is rotatable coaxially with the shaft 2 and has a bearing inner diameter 3a; 4 is fixed to the sleeve 3, and has a spiral group 4a on a surface facing the upper end surface 2b of the shaft 2;
The stainless steel thrust bearing 6 is a lubricant that is present in the minute gap between the herringbone type group 2a and the bearing inner diameter 3a, and in the minute gap between the upper end surface 2b of the shaft 2 and the spiral group 4a.

The operation of the conventional hydrodynamic bearing device configured as described above will be briefly explained below.

When the rotating part including the sleeve 3 of this hydrodynamic bearing device rotates, the centripetal nature of the rotating part is maintained by the pumping action of the radial bearing composed of the herringbone group 2a, the bearing inner diameter 3a, and the lubricant 5, and the spiral group 4a, the upper end surface 2b of the shaft 2, and the lubricant 5, the pumping action of the Nulast bearing provides a stable floating position of the rotating part and maintains normal rotation.

Problem to be Solved by the Invention However, in the above configuration, since the shaft 2 and the thrust receiver 4 are both made of the same material of stainless steel, metal contact may occur in the low speed rotation range when starting and stopping the device. Seizure occurred and the upper end surface 2b of the shaft 2 and the spiral group 4a of the thrust receiver 4 were damaged, resulting in a problem that a sufficient flying height could not be obtained and normal rotation could not be maintained.

In view of the above problems, the present invention provides a hydrodynamic bearing device that can prevent the shaft and thrust receiver from seizing and maintain normal rotation.

Means for Solving the Problems In order to solve the above problems, the hydrodynamic bearing device of the present invention includes a shaft, a sleeve provided coaxially with the shaft, and an upper end surface of the sleeve that faces the upper end surface of the shaft. a thrust receiver fixed to the shaft, a lubricant interposed in a minute gap between the shaft and the sleeve, and a minute gap between the shaft and the thrust receiver; a spiral group is provided on either the shaft or the thrust receiver; The present invention is characterized in that at least one of the shaft and the thrust receiver is made of silicon carbide.

Function The present invention can prevent the shaft and thrust receiver from seizing and maintain normal rotation with the above-described configuration.

Embodiment A hydrodynamic bearing device according to an embodiment of the present invention will be described below. FIG. 1 is a sectional view of this embodiment, and FIG. 2 is an enlarged sectional view of the main part of FIG. 1, showing the fixed drum 1. Shaft 2. Sleeve 3. The lubricant 5 has the same structure as shown in FIG. 6 is a thrust receiver fixed to the sleeve 3 and having a spiral group 6a on the surface facing the upper end surface 2b of the shaft 2 and made of silicon carbide.

The operation of the hydrodynamic bearing device configured as described above will be described below.

As in the conventional example, when the rotating part including the sleeve 3 rotates, the centripetal nature of the rotating part and a stable floating position are obtained by the pumping action. Furthermore, even if metal contact occurs in the low-speed rotation region when the rotating part starts and stops, seizure will not occur because the shaft 2 is made of stainless steel and the thrust receiver 6 is made of different materials, such as silicon carbide. Moreover, since the hardness of silicon carbide is approximately six times that of stainless steel, normal rotation can be maintained without damaging the spiral group 6a.

As described above, according to this embodiment, by using silicon carbide as the material of the thrust receiver 6, normal rotation can be maintained. In this embodiment, the material of the thrust receiver 6 is silicon carbide, but the surface may be coated with silicon carbide.

Next, a hydrodynamic bearing device according to another embodiment of the present invention will be described. FIG. 3 is an enlarged sectional view of the main parts of this embodiment, showing the fixed drum 1. Shaft 2. Sleeve 3. Lubricant 5 is the fourth
The configuration is the same as the one shown in the figure. 7 is fixed to the sleeve 3, and has a spiral group 7b with a groove depth h on the surface facing the upper end surface 2b of the shaft 2, and a silicon carbide 7b with a thickness t on the convex portion near the center of the spiral group 7a. It is a covered thrust receiver.

The operation of the hydrodynamic bearing device configured as described above will be described below.

When the rotating part including the sleeve 3 rotates, the pumping action maintains the centripetal nature of the rotating part and a stable floating position (flying height a).
) is obtained. Here, the coating thickness t of silicon carbide 7b is
The spiral group 7
There is no damage to a. Furthermore, since t(a), the upper end surface 2b of the shaft 2 and the thrust receiver 7 are not in contact with each other during rotation, so there is no problem and normal rotation can be maintained.

As described above, according to this embodiment, the convex portion near the center of the spiral group 7a of the thrust receiver 7 has a thickness t(t(a
) can maintain normal rotation by coating with silicon carbide. In this embodiment, the convex portion of the spiral group 7 is coated with silicon carbide, but the groove portion (concave portion) may be coated with silicon carbide to a thickness of t'(t'<a+h).

Effects of the Invention As described above, according to the present invention, normal rotation of the hydrodynamic bearing device can be maintained.

[Brief explanation of the drawing]

1 is a sectional view of a hydrodynamic bearing device according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the main part of FIG. 1, and FIG. 3 is a sectional view of a hydrodynamic bearing device according to another embodiment of the present invention. Enlarged cross-sectional view of main parts, No. 4
The figure is a sectional view of a rotary head drum device using a conventional hydrodynamic bearing device, and FIG. 5 is an enlarged sectional view of the main part of FIG. 4. 6... Thrust receiver, 6a... Spiral crew-7', 7 Old... Thrust receiver 1rj, 7a
- Old...Spike/leg loop, 7b...Silicon carbide coating.

Claims (1)

[Claims] a shaft, a sleeve provided coaxially with the shaft, a thrust receiver facing the upper end surface of the shaft and fixed to the upper end surface of the sleeve, a minute gap between the shaft and the sleeve, and the shaft and the thrust receiver. a lubricant interposed in a minute gap between the shaft and the thrust bearing, a spiral group being provided on one of the shaft and the thrust bearing, and at least one of the shaft and the thrust bearing being made of silicon carbide. .