JPH08166020A - Spindle device with attraction mechanism - Google Patents

Abstract

PURPOSE: To provide a spindle device with an attraction mechanism which prevents foreign matter which enters a ventilation passage of an attraction mechanism from entering a clearance of static pressure gas bearing so as to prevent the generation of galling. CONSTITUTION: In a spindle device with an attraction mechanism, a pair of static pressure gas bearings 2, 2 provided in a housing 80 across an interval in the axial direction support a hollow rotary shaft 1, and one opening end 4 side of a hollow hole 1A of the hollow rotary shaft 1 is an attraction face. The hollow rotary shaft 1 is extended up to the outside of the housing 80 of the spindle device on the opposite side to the attraction face, and an extended end 33A is supported by a bearing section 25. The bearing section 25 is mounted on a housing 40 through an elastic member 41 and provided with a distribution hole 48 which communicates the hollow hole 1A of the hollow rotary shaft 1 with the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a spindle device with a suction mechanism, which effectively prevents foreign matter such as chips from being caught in the bearing clearance of the spindle.

[0002]

2. Description of the Related Art As a conventional spindle device with an adsorption mechanism, as shown in FIG. 6, a pair of static pressure gas bearings 2, in which a spindle, which is a hollow rotary shaft 1, is axially arranged at intervals. It is supported by a cylindrical housing 3 via 2 and one open end 4 of the hollow rotary shaft 1 serves as a workpiece suction surface. The clearance dc between the housing inner diameter surface 3a of the bearing intermediate portion 3A sandwiched between the pair of static pressure gas bearings 2 and 2 and the hollow rotating shaft 1 is equal to the radial bearing clearance dA of the static pressure gas bearing 2. It is formed to have the following size (dA ≧ dc). Then, on the inner diameter surface 3a of the housing of the bearing intermediate portion 3A, annular grooves 6, 7, 7 continuous in the circumferential direction are formed at at least three positions in the axial direction, and the intermediate groove 6 and the housing Outer surface 3b
A plurality of exhaust holes 9, 9 which communicate with the housing outer surface 3b and a flow hole 8 which communicates with each other and the grooves 7 and 7 on both sides are provided so as to penetrate the housing 3 in the radial direction. On the other hand, the hollow hole 1A of the hollow rotary shaft 1 communicates with the groove 6 at the intermediate position.

A flow hole 8 in the bearing intermediate portion 3A is a vacuum exhaust passage for air sucked by the vacuum pump from the hollow hole 1A of the hollow rotary shaft 1. Also, the exhaust holes 9, 9 on both sides
Is the compressed air supply path 12 that opens to the housing outer surface 3b.
It is used as an exhaust passage for compressed air supplied to the static pressure gas bearings 2 and 2 via. A magnetic disk, which is an object to be adsorbed (work), is applied to the adsorption surface of one open end 4 of the hollow hole 1A of the hollow rotary shaft 1 and a vacuum pump is connected to the opening 8a of the flow hole 8 so that the inside of the hollow hole 1A The air is exhausted and the magnetic disk is adsorbed and held. Compressed air supplied from the compressed air supply path 12 to the static pressure gas bearings 2 and 2 is jetted from the radial bearing surfaces 2a and 2a into the radial bearing gap dA to support the hollow rotary shaft 1 in a non-contact manner. The compressed air ejected into the radial bearing gap dA is discharged to the outside of the housing from the axially outer ends of the compressed air exhaust grooves 7 and 7 opening in the housing inner diameter surface 3a and the static pressure gas bearings 2 and 2. It Then, the hollow rotary shaft 1 is rotationally driven by the motor M.

[0004]

However, in the above-mentioned conventional spindle device with a suction mechanism, the groove 6 at the intermediate position of the bearing intermediate portion 3A of the housing has the radial bearing clearance dA of the hydrostatic gas bearing 2 and the housing inner diameter surface 3a. And the hollow rotary shaft 1 communicate with each other through a clearance dc. As described above, when a part of the ventilation path for adsorbing and holding the work is in close communication with the bearing gap dA of the static pressure gas bearing, chips, grinding fluid or cutting generated when the work is processed is performed. When a foreign substance such as a liquid is removed from the suction surface during replacement or the like, the foreign matter enters the hollow hole 1A through the open end 4 and the hollow hole 1A
As a result of reaching the radial bearing clearance dA from the intake hole 11 via the clearance dc, there is a problem that galling is likely to occur in the static pressure gas bearing 2.

Also, during machining of the workpiece, grinding fluid, cutting fluid, and chips produced from the hollow hole 1A cause radial bearing clearance d.
Easy to infiltrate A. Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems. By disposing the ventilation path of the suction mechanism so as to be separated from the bearing gap of the static pressure gas bearing, foreign matter can be opened on the suction surface of the work. It is an object of the present invention to provide a spindle device with an adsorption mechanism, which does not reach the bearing clearance of a static pressure gas bearing even if it enters the ventilation path from the end, and prevents galling.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a pair of hydrostatic gas bearings axially arranged in a housing support a hollow rotary shaft, and one of the hollow holes of the hollow rotary shaft is supported. In a spindle device with a suction mechanism, the opening end side of which is a suction surface, the hollow rotary shaft is extended to the outside of the housing of the spindle device on the side opposite to the suction surface, and the extended end is supported by a bearing portion. Is attached to the housing via an elastic member, and is provided with a flow hole that communicates the hollow hole of the hollow rotating shaft with the outside.

[0007]

The hollow hole of the hollow rotary shaft that communicates the one open end on the suction surface side with the other open end on the opposite end side does not form a bearing gap between the hydrostatic gas bearing and the hollow rotary shaft. Since they are independent, there is no room for foreign matter such as chips generated during machining of the workpiece to enter the bearing gap of the static pressure gas bearing from the hollow hole that is the ventilation path of the adsorption mechanism, and therefore the static pressure gas bearing may be galled. There is no.

The elastic member interposed between the bearing portion supporting the extended end portion of the hollow rotary shaft and the housing absorbs a large whirling of the extended end portion of the hollow rotary shaft. The bearing part vibrates finely in synchronism with the rotation of the extension end, so that galling with the extension end is prevented.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The same or corresponding parts as in the conventional case are designated by the same reference numerals. First, the overall structure will be described. FIG. 1 is an overall sectional view of an embodiment of the present invention. The main body of the spindle device is divided into four parts in the axial direction. The static pressure air bearing portion 21 at the right end of the figure, the motor portion 22 on the left side thereof, the encoder portion 23 on the left side thereof, and the left side of the encoder portion 23 are
The bearing portion 25 is connected. The encoder unit 23
The illustration of the configuration is omitted.

The housing 3 of the static pressure air bearing portion 21 forming the housing 80 is integrally connected to the housing 24 of the motor portion 22 forming the housing 80 by a bolt B ₂₄ . The radial bearing surfaces 2a of the pair of hydrostatic gas bearings 2 and 2 mounted axially on the inner diameter surface 3a of the housing 80 have a slight bearing clearance dA on the outer diameter surface of the hollow rotary shaft 1. A radial bearing is formed so as to face each other in a non-contact manner. A thrust bearing surface 2s is formed on the axially outer end surface of each of the static pressure gas bearings 2 and 2.

At both ends of the hollow shaft 1B constituting the hollow rotary shaft 1, flange-shaped flange portions 31 constituting the hollow rotary shaft 1 are provided.
32 are removably attached with bolts B ₃₁ and B ₃₂ , respectively, and the inner side surfaces of the flange portions 31 and 32 are flat thrust receiving surfaces 31S and 32S, respectively, and the thrust bearing surface of the static pressure gas bearing 2 is provided. The thrust bearing is configured so as to face the 2S in a non-contact manner with a slight bearing gap.

Then, compressed air is sent from a pressurized gas supply source (not shown) to the static pressure gas bearing 2 through the compressed air supply path 12 of the housing 80, and each radial is supplied from the porous static pressure gas bearing 2 which functions as a throttle. A fluid film is formed by ejecting the fluid into the thrust bearing gap to support the hollow rotating shaft 1 in a non-contact manner by floating. Housing 8
On the inner diameter surface 3a of the bearing intermediate portion 3A of No. 0, two annular grooves 7, 7 continuous in the circumferential direction are formed adjacent to the radial bearing clearance dA at two positions in the axial direction. Exhaust holes 9, 9 that communicate with the outer surface 3b of the housing are provided so as to penetrate the housing 80 in the radial direction.
However, the grooves 7 and 7 may be provided on the outer surface of the hollow rotary shaft 1.

A rotary shaft extension 33 constituting the hollow rotary shaft 1 is fixed to the flange 32 facing the motor unit 22 side with a bolt B ₃₃ , and the rotary shaft extension 33 is attached to the motor unit 22. Further, it penetrates through the shaft center of the encoder section 23 and projects to the outside of the housing 40 of the encoder section 23 that constitutes the housing 80. The other flange 31 has a housing 80.
The opening end 4 of the through hole 34, which is provided so as to project from the end surface of the hollow shaft 1, is the opening end 4 of the hollow hole 1A of the hollow rotary shaft 1.

A brushless DC motor M is built in the motor unit 22. That is, the motor housing 24
The motor stator 35 is fixed to the inner diameter surface of the. On the other hand, the rotor 37, which is composed of a magnet and faces the stator via an air gap, is fixedly attached to the outer diameter surface of the rotary shaft extension 33. The housing 40 of the encoder portion 23 constituting the housing 80 is fixed to the motor housing 24 of the motor portion 22 on the end surface on the left end side in the figure by an appropriate method. A rotary position sensor, such as a fully non-contact rotary encoder, is optionally incorporated.

An elastic member 4 such as urethane rubber is formed on the outer end surface of the housing 40 of the encoder portion 23.
The bearing portion 25 is attached by means of bolts B ₂₃ through 1. The bearing portion 25 includes a cylindrical case 42 having a mounting flange 42f, and a cylindrical sliding body 43 made of, for example, graphite, which constitutes the bearing portion 25, is attached and fixed to the inner peripheral surface of the case 42. The extended end portion 33A extended to the outside of the housing 80 of the hollow rotary shaft 1 is the bearing portion 2
5, the other end of the hollow hole 1A penetrating through the shaft of the hollow rotary shaft 1 is closed by a stopper 44 to make it blind, and the hollow hole 1A is off-axis near the blind end of the hollow hole 1A. It has a ventilation hole 45 in the radial direction that opens to the radial surface. This vent 45
And the annular groove 4 in the circumferential direction on the inner diameter surface of the sliding body 43.
6 is formed, and the flow hole 4 for communicating the groove 46 with the connection port 47 of the vacuum pump provided on the outer surface of the case 42.
8 is provided so as to penetrate the sliding body 43 and the case 42 in the radial direction. The connection port 47 of the vacuum pump is the other opening end with respect to the one opening end 4. The annular groove 46 may be provided on the outer surface of the extension end 33A instead of the sliding body 43.

Next, the operation will be described. A pressurized gas supply source is connected to the compressed air supply path 12 that opens to the outer surface of the housing 80. An exhaust source such as a vacuum pump is connected to the connection port 47 of the bearing portion 25, which is open to the outer surface of the case 42. A magnetic disk (not shown) is attached to the open end 4 at the tip of the hollow rotary shaft 1, and a vacuum pump (not shown) is operated to suck the air in the hollow hole 1A through the groove 46 and the flow hole 48, so that the magnetic disk Hold by adsorption.

Then, the brushless motor M is started to rotate the magnetic disk together with the hollow rotary shaft 1 at a constant rotational speed to perform predetermined machining. At this time, the bearing portion 25
Is located outside the housing 80, and the hollow hole 1A, the flow hole 48, etc. forming the ventilation path of the adsorption mechanism are isolated from the radial bearing clearance dA between the hydrostatic gas bearing 2 and the hollow rotating shaft 1 completely independently of each other. Therefore, there is room for foreign matter such as chips generated during machining of the workpiece or foreign matter such as dust around the workpiece to enter the radial bearing clearance dA of the static pressure gas bearing 2 from the ventilation path of the adsorption mechanism when the workpiece is removed. There is therefore no galling of the hollow rotary shaft 1.

The action of the hydrostatic air bearing 2 which is performed in advance at the time of starting the rotation is as follows. Housing 8
The pressurized gas from the pressurized gas supply source connected to the compressed air supply path 12 opening to the outer surface 3b of 0 is sent to the static pressure gas bearing 2 made of a porous member through the groove 2A. The pressurized gas passes through the inside of the porous member and is throttled to a predetermined pressure and flow rate, and is divided into a radial bearing surface 2a and a thrust bearing surface 2S to obtain a uniform pressure and flow rate in the radial bearing clearance and the thrust bearing clearance. , The hollow rotary shaft 1 is supported in the radial direction and the thrust direction in a non-contact manner.

The gas ejected from the thrust bearing surface 2S is
The hollow rotary shaft 1 is discharged to the outside through a gap between the hollow rotary shaft 1 and the flange portions 31 and 32. In addition, a part of the gas ejected from the radial bearing surface 2a is discharged to the outside through the gap between the thrust bearing surface 2S and the flange portions 31 and 32 of the rotary shaft, and the rest is the inner diameter of the bearing intermediate portion 3A. It is discharged to the outside from the exhaust holes 9, 9 through the grooves 7, 7 adjacent to the radial bearing gap dA on the surface 3a.

As described above, whirling does not occur in the hollow rotary shaft 1 which is directly supported by the static pressure gas bearing 2 and rotates, but the extension end 33A of the hollow rotary shaft 1 is hollow. A certain degree of eccentricity with respect to the shaft 1 is unavoidable, and it rotates whirling. Since the elastic member 41 is interposed between the encoder housing 40 and the bearing portion 25 that supports the extension end portion 33A that rotates while swinging, the bearing portion 25 is synchronized with the whirling movement of the extension end portion 33A. Vibrate. Due to the synchronous vibration, it is possible to prevent a phenomenon in which the hollow rotary shaft 1 that rotates on the sliding body 43 of the bearing member 25 bites and galling occurs.

Further, when foreign matter such as chips is sucked by the exhaust pump from the hollow hole 1A through the flow hole 48, the sliding member 4
3 may be caught in the minute bearing clearance between the extended end portion 33A and the extended end portion 33A, in which case the bearing portion 25 can be pulled out from the hollow rotary shaft 1 simply by removing the bolt B _23. Because it is possible, it can be easily repaired.

2 to 4 show another embodiment of the connecting structure of the bearing portion 25 and the spindle device main body (the spindle device main body is the same and is not shown). Figure 2
Is a second embodiment, and as the elastic member interposed between the outer end surface of the housing 40 of the encoder unit 23 and the bearing unit 25, a plurality of U-shaped curved plates are used instead of the rubber elastic member 41. The point that the spring 50 is used is different from the first embodiment. One end of the leaf spring 50 is fixed to the housing 40 of the encoder section with a bolt B ₂₃ , and the other end is fixed with a bolt B ₂₅ to the bearing section 2.
It is fixed at 5.

The action and effect of the leaf spring 50 are similar to those of the rubber elastic body (preventing galling and easiness of repair) in the first embodiment. FIG. 3 shows a third embodiment, and the first point is that a plurality of compression coil springs 51 are used as elastic members interposed between the outer end surface of the housing 40 of the encoder section 23 and the bearing section 25. Is different from the embodiment described above. One end of the coil spring 51 is fixed to the housing 40 of the encoder section 23 with a bolt B ₂₃ , and the other end is fixed with a bolt B ₂₅ to the bearing section 25.
It is fixed to.

The action and effect of this coil spring 51 are similar to those of the first embodiment. There is an advantage that a commercially available coil spring can be used. FIG. 4 shows a fourth embodiment, in which a plurality of O-rings 5 are used as elastic members interposed between the outer end surface of the housing 40 of the encoder section 23 and the bearing section 25.
2 is different from the first embodiment. Each O-ring 52 is arranged so as to fit the bearing portion 25 movably in the axial direction through the bolt B ₂₃ attached to the housing 40 of the encoder portion 23. The action and effect of this O-ring 52 are also as described above. Similar to the case of the first embodiment, there is an advantage that a commercially available O-ring can be used.

FIG. 5 shows a fifth embodiment. In this embodiment, the connecting structure of the bearing portion 25 and the housing 80 is the same as that of the second embodiment, but the structure of the bearing portion 25 is different from that of each of the above embodiments. That is, inside the cylindrical case 42, a static pressure air bearing made of a cylindrical porous body 60 is mounted and fixed in place of a sliding body made of graphite as a bearing member. This porous body 60
The inner diameter surface 61 of the hollow rotary shaft 1 has a slight bearing gap.
A radial bearing surface that faces the outer diameter surface of the extended end portion 33A. On the inner diameter surface 61, an annular groove for discharging the compressed air, which is jetted from the radial bearing surface of the porous body 60 into the bearing gap and supports the hollow rotary shaft 1, to the outside on both sides of the annular groove 46. 62, 62 are formed. Each of the annular grooves 62, 62 has a porous body 60 and a case 4
2 is communicated with the outside through exhaust passages 63, 63 that pass through 2 in the radial direction.

Further, annular grooves 64, 64 are formed on the outer diameter surface of the porous body 60 outside the exhaust passages 63. Each of these annular grooves 64, 64 is formed in the case 4
2 is communicated with compressed air supply ports 66, 66 provided on the outer surface of the case 42 via air supply passages 65, 65 penetrating radially through the housing 2. By connecting a compressed air source to the compressed air supply ports 66, 66 and supplying compressed air, the porous body 60
Functions as a static pressure air bearing, supports the extended end portion 33A of the hollow rotary shaft 1 in the radial direction in a non-contact manner, and allows stable and smooth rotation. The porous body 60 has a structure in which both end surfaces, the annular grooves 46, 62, the flow holes 48 and the exhaust passage 63 are impregnated with resin to close the porous eyes and prevent the compressed air from flowing at the portions impregnated with resin. ing.

The rotation of the hollow rotary shaft 1 in each of the above embodiments is controlled by feeding back a detection signal of a rotary encoder (not shown) built in the encoder section 23 to a controller (not shown) of the brushless motor M. Accurate rotation of the attracted body such as a magnetic disk can be ensured, but the present invention is also applicable to a rotary encoder such as one having no rotation sensor.

In each of the above embodiments, the vacuum suction method is used as the workpiece suction mechanism, but the invention is not limited to this, and instead of vacuum chucking the workpiece, the bearing portion 25 is used.
A compressed air source is connected to the vacuum pump connection port 47 of the above, and compressed air is sent from the circulation hole 48 to the hollow hole 1A of the hollow rotary shaft 1 to a pressurizing fluid type chuck adapter (not shown) previously attached to the opening end 4. The present invention can also be applied to a device that uses a pressure adsorption mechanism of a system that chucks a work by creating a reduced pressure based on a high-speed air flow.

[0029]

As described above, according to the spindle device with the suction mechanism of the present invention, the suction mechanism is provided in which one open end of the hollow rotary shaft supported through the static pressure gas bearing is the suction surface. The hollow rotary shaft in the spindle device is extended to the side opposite to the suction surface, and the bearing part that supports the extended end is provided with a gas ventilation path for operating the suction mechanism, so that foreign matter is vented from the open end of the suction surface of the workpiece. Even if it enters the path, there is no room to enter into the bearing clearance far from the exhaust path of the static pressure gas bearing, and as a result, galling of the static pressure gas bearing is prevented.

Further, since the bearing portion is attached to the housing from the outside, the bearing portion can be easily repaired even if it is galled. Further, the bearing portion supporting the extended end portion of the hollow rotary shaft is attached to the housing via the elastic member, and when the extended end portion swirls, the bearing portion also vibrates in synchronization, and as a result, the hollow rotary shaft It is also possible to prevent galling between the extended end portion and the bearing portion.

[Brief description of drawings]

FIG. 1 is an overall sectional view of a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view illustrating a support structure for a hollow rotary shaft extension end portion according to a second embodiment of the present invention.

FIG. 3 is a partial cross-sectional view illustrating a support structure for a hollow rotary shaft extension end portion according to a third embodiment of the present invention.

FIG. 4 is a partial cross-sectional view illustrating a support structure for a hollow rotary shaft extension end portion according to a fourth embodiment of the present invention.

FIG. 5 is a partial cross-sectional view illustrating a support structure for a hollow rotary shaft extension end portion according to a fifth embodiment of the present invention.

FIG. 6 is an overall sectional view of a conventional spindle device with a suction mechanism.

[Explanation of symbols]

 1 Hollow Rotating Shaft 1A Hollow Hole 2 Hydrostatic Gas Bearing 4 (One) Opening End 25 Bearing Part 33 (Hollow Rotating Shaft) Extended End 41 Elastic Member 47 (Other) Opening End 48 Circulation Hole 50 Elastic Member 51 Elastic Member 52 elastic member 80 housing

Claims (1)

[Claims] 1. A pair of hydrostatic gas bearings axially arranged in a housing to support a hollow rotary shaft, and one opening end side of a hollow hole of the hollow rotary shaft is an adsorption surface. In the spindle device with a suction mechanism, the hollow rotary shaft is extended to the outside of the housing of the spindle device on the side opposite to the suction surface, and an extended end portion is supported by a bearing portion, and the bearing portion has an elastic member in the housing. A spindle device with a suction mechanism, which is equipped with a suction hole and is provided with a through hole that communicates the hollow hole of the hollow rotating shaft with the outside.