JP3653861B2 - Spindle device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spindle device suitable for inspection equipment such as a magnetic disk and a magnetic head.
[0002]
[Prior art]
In this type of spindle device, a spindle as a rotating shaft is supported by a cylindrical housing via a static pressure gas bearing. The rotating shaft has a cylindrical shape, and one end opening is a vacuum suction portion. For example, a magnetic disk or the like is attracted and held by using the vacuum attracting unit to perform a predetermined inspection. The housing, the static pressure gas bearing, and the rotating shaft are all made of a conductive material.
[0003]
[Problems to be solved by the invention]
By the way, when inspecting a magnetic disk or the like, a voltage may be applied separately on the housing side and the rotating shaft side. In this case, it is necessary to electrically insulate between the housing and the rotating shaft. However, in the conventional spindle apparatus, electrical insulation is performed by a bearing gap between the static pressure gas bearing and the rotating shaft.
[0004]
However, if the housing and the rotary shaft are electrically insulated in this way between the bearing gaps, the presence of very little dust etc. is not allowed between the bearing gaps. There is a disadvantage that the efficiency is lowered.
[0005]
In addition, despite the long time required for cleaning and assembling work, it is not surprising that dust or the like enters the bearing gap as time passes and the insulation environment is destroyed.
[0006]
The present invention has been made in order to eliminate such inconvenience, and provides a spindle device capable of reliably performing electrical insulation between a housing and a rotating shaft and improving productivity. For the purpose.
[0007]
[Means for Solving the Problems]
In order to achieve this object, a spindle apparatus according to the present invention includes two static pressure gas bearings made of porous graphite material and a large-diameter hole portion that fits the outer diameter surface of the static pressure gas bearing in the axial direction. A spindle device comprising: a housing having both ends of the housing; and a rotary shaft supported by the housing via the hydrostatic gas bearing , wherein an outer diameter surface of the hydrostatic gas bearing and an inner circumference of the large-diameter hole portion An insulating material is disposed between the surface and the inner end surface of the static pressure gas bearing and the bottom surface portion of the large-diameter hole portion .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory sectional view for explaining a spindle apparatus which is an example of an embodiment of the present invention.
[0009]
This spindle device includes a stationary body 3 having a housing 1 and a static pressure gas bearing 2 attached to the inner peripheral surface of the housing 1, and a rotating shaft 4 supported by the housing 1 via the static pressure gas bearing 2. Prepare. In this embodiment, the housing 1, the static pressure gas bearing 2 and the rotating shaft 4 are all made of a conductive material.
[0010]
The housing 1 has a cylindrical shape, and two large-diameter holes 5 are formed in the inner peripheral surfaces of both end portions in the axial direction so as to be cut out in an annular shape and open outward in the axial direction. Each large-diameter hole 5 is fitted with a cylindrical porous member constituting the hydrostatic air bearing 2 by means such as adhesion or interference fit. The porous member 2 is made of a porous graphite material or the like, and is finished by cutting or grinding so that the inner diameter surface is used as the radial bearing surface 6 and the outer end surface is used as the thrust bearing surface 7.
[0011]
The portion where the porous member 2 and the large-diameter hole portion 5 face each other, that is, between the outer diameter surface of the porous member 2 and the inner peripheral surface of the large-diameter hole portion 5 and the inner end surface of the porous member 2 is large. A surface treatment film as an insulating material 8 is interposed between the bottom surface of the diameter hole portion 5, and thereby, the space between the housing 1 and the porous member 2, and the space between the housing 1 and the rotating shaft 4. It is electrically insulated so that a voltage can be separately applied to the housing 1 and the rotating shaft 4. The surface treatment film is formed of polyamideimide or a fluorine compound. Here, in this embodiment, the outer diameter surface and the inner end surface of the porous member 2 are coated with the surface treatment film 8, but instead, the inner peripheral surface and the bottom surface of the large diameter hole portion 5 The surface treatment film 8 may be coated.
[0012]
The porous member 2, the rotation shaft 4 is inserted into and presence of bearing clearance S _1. The length of the rotating shaft 4 in the axial direction is substantially the same as that of the housing 1, and a through hole 4 a penetrating along the axis is formed inside. The outer peripheral surface of the rotating shaft 4 is a radial receiving surface 12 that faces the radial bearing surface 6 of the porous member 2 with a bearing clearance S ₁ therebetween, and the radial receiving surface 12 and the radial bearing surface 6 serve as a radial bearing. A bearing is constructed.
[0013]
Further, flanges 9 are detachably fixed to both ends of the rotating shaft 4 via bolts 10, respectively. The flange portion 9 faces the end surface of the housing 1, and a suction hole 9 a that communicates with the through hole 4 a of the rotating shaft 4 is formed in the center portion. The outer end surface of one flange portion 9 forms a workpiece suction portion 11 that can be used for suction holding of a magnetic disk or the like. The inner end surface of the flange portion 9 is a thrust receiving surface 13 that faces the thrust bearing surface 7 of the porous member 2 with a bearing clearance S ₂ therebetween, and the thrust bearing surface 13 and the thrust bearing surface 7 constitute a thrust bearing. Is configured.
[0014]
Three circumferential grooves 15, 16, and 17 that are continuous in the circumferential direction are formed on the inner circumferential surface of the housing 1 located between the porous members 2 at predetermined intervals in the axial direction. One end of an exhaust hole (not shown) formed in the wall portion of the housing 1 communicates with the circumferential groove 15, 17 located at a position adjacent to the porous member 2 among these circumferential grooves 15, 16, 17. The other end of the exhaust hole is open to the outer surface of the housing 1.
[0015]
One end of an air intake hole 18 formed in the wall portion of the housing 1 communicates with the circumferential groove 16 at the intermediate position, and the other end of the air intake hole 18 opens to the end surface of the housing 1 and is shown at the opening end thereof. Pipes such as vacuum pumps are not connected. The circumferential groove 16 communicates with one end of an intake hole 19 that extends in the radial direction in the wall portion of the rotary shaft 4 and the other end of the intake hole 19 communicates with the through hole 4a. ing. A plurality of intake holes 19 are formed at predetermined intervals in the circumferential direction.
[0016]
One end of the air supply hole 14 is opened on the end surface of the housing 1, and the other end of the air supply hole 14 branches into two in the wall portion of the housing 1 to reach the outer diameter surface of each porous member 2. ing. By feeding compressed air from a pressurized air supply source (not shown) into the air supply hole 14, the compressed air enters the bearing clearance S ₁ of the radial bearing and the bearing clearance S ₂ of the thrust bearing through the porous member 2 that functions as a throttle. As a result, a fluid film is formed, and the rotary shaft 4 is levitated and supported with respect to the fixed body 3 without contact.
[0017]
The compressed air ejected from the thrust bearing surface 7 is discharged to the outside through the bearing clearance S ₂ , and the compressed air ejected from the radial bearing surface 6 is partially discharged from the bearing clearance S ₂ to the outside. The remaining portion is discharged to the outside through the exhaust holes from the circumferential grooves 15 and 17 adjacent to the porous member 2.
[0018]
In the spindle device having such a configuration, a magnetic disk (not shown) is mounted on the work attracting portion 11 of the flange portion 9 provided at the end of the rotating shaft 4 to operate the vacuum generation source, and the air in the through hole 4a is sucked. The magnetic disk is attracted and held by vacuum suction through the hole 19, the circumferential groove 16, and the suction hole 18, and then the magnetic disk is rotated at a constant rotational speed together with the rotating shaft 4 by a driving means (not shown). Then, a brush supported by a conductive plate spring from the fixed body 3 is brought into contact with the rotary shaft 4 to bring the housing 1 and the rotary shaft 4 into a conductive state of the same potential, or the fixed body 3 and the conductive plate spring. The fastening portion is insulated with an insulating material such as vinyl chloride, and the housing 1 and the rotating shaft 4 are insulated to inspect the magnetic disk. When the magnetic disk is inspected with the housing 1 and the rotary shaft 4 in an insulated state, the large diameter hole between the porous member 2 and the housing 1 is formed between the housing 1 and the rotary shaft 4 as described above. Since it is electrically insulated by the surface treatment film 8 interposed in the part facing the part 5, as in the past, slight dust etc. existing in the bearing gap of the hydrostatic air bearing 2 can be ignored. As a result, the housing 1 and the rotary shaft 4 can be reliably insulated regardless of the passage of time.
[0019]
Further, since the slight dust existing in the bearing gap of the hydrostatic air bearing 2 can be ignored, the time required for cleaning and assembling work can be greatly shortened compared to the conventional case. It is possible to improve the performance.
[0020]
In the above embodiment, the housing 1, the static pressure gas bearing 2 and the rotary shaft 4 are all formed of a conductive material, and surface treatment is performed on the facing portion between the static pressure air bearing 2 and the large-diameter hole 5 of the housing 1. By interposing the membrane 8, the housing 1 and the rotary shaft 4 are electrically insulated from each other. Instead, at least one of the rotary shaft 4, the hydrostatic air bearing 2 and the housing 1 is provided. An insulating material such as ceramic may be used to electrically insulate between the housing 1 and the rotating shaft 4.
[0021]
Further, in the above embodiment, the case where a porous member is used as the static pressure air bearing 2 is taken as an example, but instead of this, for example, a multi-hole type static pressure air provided with an orifice throttle or a self-contained throttle A bearing or a surface-restricted hydrostatic air bearing may be used.
[0022]
【The invention's effect】
As is apparent from the above description, an insulating material is disposed on at least one of the fixed body and the rotary shaft rotatably supported by the fixed body to electrically insulate between the housing and the rotary shaft. Therefore, as in the past, slight dust and the like existing in the clearance of the hydrostatic air bearing can be ignored, and as a result, the housing and the rotating shaft are reliably insulated regardless of the passage of time. The effect that it can do is acquired.
[0023]
In addition, since it is possible to ignore a small amount of dust and the like existing in the bearing gap of the hydrostatic air bearing, the time required for cleaning and assembly work can be greatly shortened compared to the conventional method. The effect that improvement of can be aimed at is acquired.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view for explaining a spindle apparatus which is an example of an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Housing 2 ... Static pressure gas bearing 3 ... Fixed body 4 ... Rotating shaft 8 ... Insulating material

Claims (1)

Two hydrostatic gas bearings made of porous graphite material, a housing having large-diameter hole portions fitted in the outer diameter surface of the hydrostatic gas bearing at both axial ends, and the hydrostatic gas bearing in the housing A spindle device with a rotating shaft supported via
An insulating material is disposed between the outer diameter surface of the static pressure gas bearing, the inner peripheral surface of the large diameter hole portion, and the inner end surface of the static pressure gas bearing and the bottom surface portion of the large diameter hole portion. Spindle device to do.

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