JPS5942388B2 - rotating seat device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary seat device that hydrodynamically improves the rotational stability of the sheet and improves the stability of recording and reproducing information on the sheet surface. be.

A flexible sheet is rotated with a gap of several tens of microns between a disk or a rigid surface that forms a curved surface (hereinafter referred to as the back plate), an air film is generated within the gap, and the pressure of the air film is Rotating sheet devices that align the rotating shape of the sheet with the shape of the back plate are being developed as inexpensive information recording or reproducing devices by using detection systems such as magnetic heads, piezoelectric elements, or laser beams. ing.

The important points regarding such a rotary seat device are how to remove seat vibration and how to maintain the relative positional relationship between the seat and the detection element.

Various considerations for sheet stability have been made and proposed in the past. However, with the recent increase in recording and playback density, the amplitude of sheet vibration is required to be several microns or less, and the conventional back plate method is unable to maintain the sheet's planar shape or eliminate minute vibrations. , the current situation requires many improvements. This invention makes the pressure effect of the air film in the conventional back plate method uniform along the radial direction of the seat by providing micro holes in the back plate, improving the rotating shape of the seat and eliminating minute vibrations if possible. It is closed.

This will be explained below using figures.

FIGS. 1 and 2 are schematic diagrams of a conventional back plate system, in which a rotating seat 1 is fastened to a rotating shaft of a motor 5 by a flange 2 and driven. The rotating seat 1 is held with a small gap (approximately 50μ) between the rotating seat 1 and the back plate 3, and the viscous air existing in the gap between the rotating seat 1 and the back plate 3 is affected by centrifugal force and becomes a vortex toward the outer periphery of the motor drive shaft. Fresh air is supplied from the opening.
At this time, an air film with a pressure gradient is formed in the gap between the rotary seat 1 and the back plate 3, and a state of equilibrium with the centrifugal force, rigidity force, and internal stress caused by its own weight generated within the rotary seat 1 is maintained. along the back plate 3. A detection element 4 such as a magnetic head or a laser head is mounted on a rotating sheet 1.
is moved in the radial direction of the sheet 1 to record or reproduce information concentrically or spirally on the sheet 1. The most important thing at this time is that the relative positional relationship between the detection element 4 and the rotary sheet 1 must be maintained constant in order to improve the stability of recording and reproduction on the sheet. Generally the detection element 4
Since the rotary seat 1 mechanically moves on a parallel line, the rotating seat 1 is required to maintain a parallel plane along the radial direction and eliminate seat vibration. However, according to the conventional planar back plate, the rotary seat 1 forms a concave curve in the radial direction with respect to the back plate 3, as shown in FIG. This is because the air flowing in from the inner circumference of the back plate 3 is restricted, so the pressure of the air film in the gap becomes negative pressure, and the back plate 3 This is because it is attracted to the direction. Also, since the thickness of the air film is not constant along the radial direction,
The damping effect of the air film on seat vibrations is not uniform over the entire surface of the seat, making it impossible to completely eliminate minute vibrations of the seat due to rotation. FIG. 4 is a diagram showing the radial velocity distribution of the air flow within the gap.

This figure shows the velocity distribution when the inflow air from the inner periphery of the back plate 3 is almost zero. If air is supplied from the inner periphery, the air flow in the gap at each radius will change. The radial velocity is ν. The shape of the rotating seat 1 is determined by the balance between the pressure of the air film in the gap and the internal stress of the rotating seat 1. The internal stress of the rotary seat 1 is affected by centrifugal force and its own weight, but since the self-weight of the seat 1 can be almost ignored compared to the influence of centrifugal force, the internal stress in the rotary seat 1 is influenced by the horizontal plane of the rotary seat 1. It can be thought that it occurs within the Therefore, the pressure of the air film in the gap must match the atmospheric pressure at the open surface of the rotary seat 1, which is necessary Dp in order to make the rotary seat 1 a horizontal surface.

The pressure gradient of the air film is air density 0dr degree f1 rotation speed ω
, the flow rate Q1, the gap h1, and the viscosity coefficient μ of the air are expressed by the following equation.

Here, in order to hold the rotary seat 1 on a horizontal plane, it is understood that Dp can be set to zero by setting the pressure gradient in the above equation to zero.

After all, taking into account that the radial velocity of the air flow is proportional to the radius r, the condition that the air inlet is provided in proportion to the radius r is derived. Based on the above-mentioned conclusion, the present invention is based on concentrically drilling minute holes 3a in a number proportional to the radial distance in the back plate 3, driving the rotary seat 1 on the back plate 3, and driving the rotary seat 1 on the back plate 3&. In contrast, it is maintained in a horizontal plane.

FIG. 5 shows an embodiment of the present invention, in which air is not supplied from the seat flange 2 portion, and the pressure gradient accompanying the radial velocity of the air flow due to centrifugal force is applied to the microholes 3a of the back plate 3. This is corrected by a small amount of air drawn in from the area. The diameter of the microhole 3a of the back plate 3,
The number is determined by factors such as the thickness of the rotary sheet 1 and the sheet rotation speed. The pressure correction by the micro holes 3a provided in the back plate 3 is performed by changing the rotating seat 1 into a shape Q parallel to the back plate 3, and adjusting the equilibrium state between the seat and the air film at each radial position to the entire surface of the rotating seat 1. Figure 6 shows that when the thickness of the rotating seat is large, the air flow between the rotating seat and the back plate is large. This is an application example of the present invention when generating negative pressure. That is, in this example, an arcuate hole 3b is provided on a concentric circle of the back plate 3, and the overall width of the hole is proportional to the radius. Therefore, the effect is considered to be equivalent to the case where the number of microholes is provided in proportion to the radial distance. Further, although not shown in the drawings, the application of providing microholes in the back plate can be implemented in the same manner in a saddle-shaped back plate.

[Brief explanation of drawings]

Figures 1 and 2 are sectional views showing a conventional device, Figure 3 is a view showing the radial shape of the sheet when a flat back plate is used, and Figure 4 is a view showing the radial velocity of the air film. , FIG. 5 is a perspective view showing one embodiment of the invention, and FIG. 6 is a plan view showing a back plate of another embodiment of the invention. In the figure, 1 is a rotating seat, 2 is a flange, 3 is a back plate, 3a and 3b are holes, 4 is a detection element, and 5 is a motor.

Claims (1)

[Claims] 1 Rotation in which a flexible sheet is rotated along the rigid surface using an air film generated in the gap between it and a rigid surface that is a flat or curved surface, and information is recorded or reproduced on the sheet by a recording element or a reading element. A rotary seat device, characterized in that the rigid surface is provided with a number of minute holes or minute elongated holes concentrically arranged in a number corresponding to the seat rotation radius distance, and the seat is rotated on the rigid surface.