JPH0333508A - Hydrostatic fluid bearing - Google Patents

Abstract

PURPOSE:To prevent the shape of a land or a guide surface from being damaged so as to maintain the accuracy of a bearing for a long time by providing a controller for pressing a plunger against a guide and housing the plunger inside a cylinder. CONSTITUTION:Outside a land 10, there is provided a plurality of cylinders 13 with each central shaft thereof perpendicular to the surface of a guide 1. One end of a bellows 15 serving as an expandable member is fixed at the bottom of the cylinder 13, and a plunger 14 is secured in the other end of the bellows 15. At the same time that the supply of a high pressure fluid to a hydrostatic fluid bearing 4 is ceased, the bellows 15 is expanded so that the plunger 14 secured in the bellows 15 is projected from the lower surface of a table 2, to lift the table 2 in a state pressed against the guide surface. Therefore, a space between the land and the guide surface can be kept so that the shape of the land and the guide surface can be prevented from being damaged, thereby maintaining the accuracy of the bearing for a long time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydrostatic fluid bearing that utilizes the static pressure of a fluid such as hydraulic pressure or air pressure used in bearings for tables, main shafts, etc. of machine tools. .

[Prior Art] Conventionally, in a hydrostatic fluid bearing, as shown in FIG. 7, for example, a load 3 is mounted on a table 2 that is linearly guided by a guide 1, and there is a A hydrostatic fluid bearing 4 is constructed. High pressure fluid F is supplied to the hydrostatic fluid bearing 4 from a fluid circulation device 5 via a bearing controller 6 and a feed pipe 7 . As shown in FIG. 8, the high-pressure fluid F supplied to the hydrostatic fluid bearing 4 flows into the pocket 9 through the throttle 8, passes through the bearing gap between the land 10 and the guide 1 facing the land 10, and enters the pocket. 9 , is collected through the discharge hole 11 into the discharge pipe 12 , and returned to the fluid circulation device 5 . In this process, the load of the load 3 and the weight of the table 2 are supported by the static pressure of the high-pressure fluid F in the pocket 9, and if the fluid is a liquid, a fluid film is formed between the land 10 and the guide l; In this case, an air layer is formed. Therefore, the table 2 can slide on the guide 1 with low friction while carrying the load 3 (for example,
No. 49416, Japanese Utility Model Application Publication No. 147920/1983).

[Problem to be Solved by the Invention] However, when the operation of the table 2 is finished and the control valve of the bearing controller 6 is closed, or the fluid circulation device 5 is stopped and the supply of high-pressure fluid F is stopped, the table 2 falls due to the weight of the load 3 and the table 2, the fluid film formed between the land 10 and the guide 1 also disappears, and finally the land IO and the guide 1 come into direct contact. In this situation, the weight of the load 3 and the table 2 (for example,
A table equipped with a spindle motor for a machine tool (approximately 300 kilograms in weight) is supported only by the narrow land lO, which is usually only a few millimeters wide. This has disadvantages such as increased surface roughness, which reduces the load capacity and slidability of the hydrostatic fluid bearing.

An object of the present invention is to maintain bearing accuracy by preventing direct contact between the land and the guide when the supply of high-pressure fluid F is stopped.

[Means for Solving the Problems] The present invention provides a hydrostatic fluid bearing that levitates and supports a table by supplying fluid to pockets surrounded by lands provided opposite to each other through a gap in a guide surface. A plurality of cylinders are provided on the outer periphery of a land with their central axes perpendicular to the guide surface, a plunger is made up of a sliding member that slides inside the cylinder, and an expandable cylinder is provided between the bottom surface of the cylinder and the plunger. a member, when the supply of fluid to the pocket is stopped, the telescoping member is extended to press the plunger against the guide, and when fluid is to be supplied to the pocket, the telescoping member is contracted to push the plunger against the cylinder. This is a hydrostatic fluid bearing characterized in that it is comprised of a control device for controlling storage in the hydrostatic bearing.

[Operation] At the same time as the supply of high pressure fluid to the hydrostatic fluid bearing stops,
As the telescopic member expands and contracts, a plunger fixed to the telescopic member protrudes from the underside of the table, presses against the guide surface, and lifts the table. Therefore, contact between the land and the guide surface can be prevented.

[Example] An example of the present invention shown in the drawings will be described. In addition, the seventh
Components having the same functions as those of the conventional example shown in the drawings are indicated by the same names and symbols, and explanations thereof will be omitted.

FIG. 1 is a configuration diagram showing an embodiment of the present invention, in which a hydrostatic fluid bearing 4 is constructed between a guide 1 and a table 2. As shown in FIG.

FIG. 2 is an enlarged sectional view of a main part A of the hydrostatic fluid bearing 4 shown in FIG. The hydrostatic fluid bearing 4 includes a guide 1, a land lO,
It is formed by a pocket 9 surrounded by a land 10 and provided with an aperture 8. A plurality of cylinders 13 are provided on the table 2 outside the land 10 with their central axes perpendicular to the plane of the guide l. Inside the cylinder 13 is a plunger 1 made of a self-lubricating material such as oil-impregnated alloy or fluororesin.
4 is provided so as to be able to slide in the direction of the central axis of the cylinder 13. One end of a bellows 15, which is a telescopic member whose expansion and contraction can be controlled, is fixed to the bottom surface of the cylinder l3, and a plunger 14 is fixed to the other end of the bellows 15.

One end of the bellows 15 is connected to a first flow port of an electromagnetic three-way valve 17 via a communication pipe 16.

The second flow port of the three-way valve 17 is connected to the feed pipe 7 between the bearing controller 6 and the fluid circulation device 5, and the third flow port is connected to the feed pipe 7 between the bearing controller 6 and the fluid circulation device 5. It is connected to the discharge pipe 12.

The switching operation of the three-way valve 17 is linked to the opening/closing operation of the bearing controller 6. When the opening operation sends the high pressure fluid F to the hydrostatic fluid bearing 4, the communication pipe 16 is communicated with the discharge pipe 12, and when the closing action sends the high pressure fluid F to the hydrostatic fluid bearing 4. When the system is stopped, the communication pipe 16 is connected to the feed pipe 7.

In such a configuration, when the table 2 is in operation, the communication pipe 16 communicates with the discharge pipe 12 of the fluid circulation device 5, so the inside of the communication pipe 16 becomes negative pressure, and the bellows 15 contracts. Therefore, since the plunger 14 is drawn into the cylinder 13, the table 2 is guided by the guide 1 and slides without any problem.

When the operation of the table 2 is finished and the supply of high pressure fluid F to the hydrostatic fluid bearing 4 is stopped by the operation of the bearing controller 6, the three-way valve 17 is switched and the communication pipe 16 is connected to the fluid circulation device 5.
The pressure in the communication pipe 16 becomes high because it communicates with the feed pipe 7 of the bellows 15, and the high-pressure fluid F is sent to the bellows 15. Bellows 1
5 extends to push the plunger 14 out of the cylinder 13 and press against the guide 1, lifting the table 2 from the guide 1 and maintaining the gap between the table 2 and the guide 1.

In addition, in order to stop the fluid circulation device 5 after the table 2 has finished operating, an on-off valve 18 is provided in the communication pipe 16 between the three-way valve 17 and the bellows 15, as shown in FIG. After the three-way valve 17 is switched and the high-pressure fluid F is sent to the bellows 15, the bearing controller 6 may be linked to close the on-off valve 18.

Further, the expandable member is not limited to a bellows, but may be a diaphragm operated by fluid pressure.

Further, as shown in FIG. 4, the expandable member may be a stack of a plurality of piezoelectric elements 19 that expand when a voltage is applied and contract when the voltage is applied due to the piezoelectric effect. Piezoelectric element 19
The operation is linked with the opening/closing operation of the bearing controller 6 by the voltage controller 20 shown in FIG. A voltage is applied when fluid F is stopped.

In this case, when the plunger 14 fixed to the piezoelectric element 19 presses the guide 1, the contact pressure is applied to the piezoelectric element 19 so as to be constant even if the tip of the plunger 14 or the guide l is worn out. Based on the relationship between the voltage and the amount of displacement of the plunger 14, the voltage of the piezoelectric element 19 can be adjusted by the controller 20.

Further, as shown in FIG. 6, a stepped part 21 is provided near the opening facing the guide surface in the cylinder 13 to fix one end of the ring-shaped piezoelectric element 19, and a collar is attached to one end of the plunger 14. A shaped portion 22 is provided, and a stepped portion 21 and a brim shaped portion 22 are provided.
A piezoelectric element 19 is fixed between the plunger 14 and
You may arrange|position so that the other end may protrude from between the stepped parts 21.

In this case, a voltage is applied to the piezoelectric element 19 only while the table 2 is in operation to cause the piezoelectric element 19 to expand, and the plunger 14
Push up and store it in the cylinder 13. When the operation of the table 2 is finished, the power to the piezoelectric element 19 is turned off, the piezoelectric element 19 is contracted, and the plunger 14 is
Protrude downward and lift table 2. Therefore, while the table 2 is stopped, the power to the piezoelectric element 19 as well as the fluid circulation device 5 can be kept off.

Further, the telescopic member may be an electromagnetic linear actuator such as a solenoid having a short operating length, which is linked to the opening/closing operation of the bearing controller 6.

[Effect of the invention] As described above, according to the present invention, the table stops,
Even if the static pressure inside the pocket of a hydrostatic fluid bearing decreases, the gap between the land and guide surface is maintained, which prevents damage to the land shape and guide surface and maintains bearing accuracy for a long time. effective.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main part thereof, Fig. 3 is a block diagram showing another embodiment, and Fig. 4 is a block diagram showing an embodiment of the present invention.
The figure is an enlarged sectional view of the main part of another embodiment, FIG. 5 is a configuration diagram thereof, FIG. 6 is an enlarged sectional view of the main part of another embodiment, FIG. 7 is a configuration diagram showing a conventional example, and FIG. 8 is an enlarged sectional view of the main part thereof. 1... Guide, 2... Table, 3... Load, 4...
...Static pressure fluid bearing, 5...Fluid circulation device, 6...Bearing controller, 7...Feed pipe, 8...Aperture, 9...Pocket, IO...Land, 11...・Discharge hole, 12...
Discharge pipe, 13... cylinder, 14... plunger,
15... Bellows, I6... Communication pipe, 17... Three-way valve, 18... Open/close valve, 19... Piezoelectric element, 20...
・Voltage controller, 21...Stepped part, 22...Brim part K: \ ,)

Claims (1)

[Claims] 1. In a hydrostatic fluid bearing that levitates and supports a table by supplying fluid to a pocket surrounded by lands provided oppositely through a gap in a guide surface, a plurality of cylinders with their axes perpendicular to the guide surface;
a plunger consisting of a sliding member that slides within the cylinder; a telescoping member provided between the bottom surface of the cylinder and the plunger; and a telescoping member that extends when the supply of fluid to the pocket is stopped. and a control device that controls the plunger to be pressed against the guide and to contract the telescopic member and house the plunger in the cylinder when fluid is supplied to the pocket. Pressure fluid bearing. 2. The extensible member is a bellows, and when fluid is supplied to the pocket, the control device controls the electromagnetic three-way valve to supply fluid from the fluid circulation device to the bellows through the electromagnetic three-way valve. A hydrostatic fluid bearing according to claim 1. 3. The hydrostatic fluid bearing according to claim 2, wherein an on-off valve is provided between the bellows and the electromagnetic three-way valve, and the on-off valve is controlled to close after fluid is sent to the bellows. 4. The hydrostatic fluid bearing according to claim 1, wherein the expandable member is a piezoelectric element, and a voltage is applied to the piezoelectric element when fluid supply is stopped. 5. A stepped part is provided in the cylinder near the opening facing the guide surface, a collar-shaped part is provided at one end of the plunger, and the piezoelectric element is disposed between the stepped part and the collar-shaped part. 2. The hydrostatic fluid bearing according to claim 1, wherein the plunger is fixed, the other end of the plunger is arranged so as to be able to protrude from between the stepped portions, and a voltage is applied to the piezoelectric element when fluid is supplied.