JP2003156042A - Hydrostatic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrostatic bearing which can reduce the friction resistance even at high-speed rotation, suppress heat generation and power consumption, and increase the supporting rigidity at low-speed rotation. SOLUTION: Compressed air is used at the high-speed rotation and water is used at the low-speed rotation by switching the pressurized support fluid to be fed to the bearing.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatic bearing for supplying a pressurized fluid between two objects and supporting one in the non-contact state. 2. Description of the Related Art In a conventional hydrostatic bearing, for example, in the case of a rotary shaft using liquid as hydraulic oil, as shown in FIG. 2, a plurality of hydrostatic pockets are formed on the inner surface of a cylindrical bearing body 22. 25a-2
5d is formed, and lubricating oil supply sections 24a to 24d are provided in each of the static pressure pockets 25a to 25d. The lubricating oil 30 in the tank 29 is pressurized by the pump 31 and supplied to each supply via a piping system 37. Static pressure pocket 25a from parts 24a to 24d
Rotating shaft 23 supplied to the bearing body 22
Are rotatably supported. The supplied lubricating oil is discharged into the unformed part of the static pressure pocket 2
From 6a to 26d, the water is collected at a lower portion through a recovery path 27 provided between the bearing body 22 and the outer cylinder 23, and returns to the tank 30 through the recovery pipe 38 from the opening 28. [0003] Such a hydrostatic bearing supported by a lubricating oil has no solid contact, has good rotational accuracy, has a long life, and can increase supporting rigidity by increasing supply pressure. Since the viscosity is large, frictional resistance is increased at high speed rotation, power consumption is increased, and heat generation is also increased. Therefore, in high-speed rotation, compressed air having low viscosity is used instead of lubricating oil. However, a hydrostatic bearing using compressed air has low rigidity and cannot support a large load. [0004] Therefore, the operating range is limited to certain operating conditions, that is, the main shaft of a measuring instrument, a drilling machine, a grinding machine, or the like, and the rotation speed range is from low speed to high speed as in a machining center. However, it has been difficult to use the bearing under a condition in which the load is applied from a light load to a high load. As an example of such a constraint, that is, an attempt to reduce the frictional resistance of a fluid bearing during high-speed rotation and to expand the range of use of a hydrostatic bearing, Japanese Patent Laid-Open No. 2000-32000
46072. As shown in FIG. 3, this is a hydrostatic bearing device including a supply mechanism for selectively supplying a plurality of types of liquids having different viscosities as working fluids. As shown in FIG. 3, a three-way valve 53 is provided in a pipe 57 communicating with the supply ports 44a to 44d, and the water 5 in the tank 49 is provided.
0 is increased in pressure by a pump 51 and sent to one supply port of the three-way valve 53. Further, the tank 59 is filled with lubricating oil, and the pressure is increased by the pump 61 and sent to the other supply port of the three-way valve 53. By switching the three-way valve 53, the working fluid to be supplied to the static pressure pockets 45a to 45d of the static pressure bearing can be selected. [0006] The working fluid supplied to the static pressure pockets 45a to 45d is recovered through outlets 46a to 46d provided outside the static pressure pockets 45a to 45d.
It returns to the respective tanks 49 and 59 via the three-way valve 63 provided in the middle of 4. With this configuration, a plurality of types of liquids having different viscosities can be switched and used, and the range of the number of rotations and the rigidity of the support can be measured.
That is, in high-speed rotation, a low-viscosity liquid is used to reduce frictional resistance and power consumption is reduced, and in low-speed rotation, a high-viscosity liquid is used to increase supporting rigidity. [0008] However, in the above-described prior art, two kinds of liquids are mixed.
In order to separate the mixed liquid, for example, when water and lubricating oil are used, an oil adsorbing filter 55
For example, a device for separating oil components is required. Further, it is necessary to provide a drain valve 70 in the lubricating oil tank 59 to separate and collect water having a high specific gravity. Further, the number of tanks and pumps is reduced by the number of lubricating oils, which causes problems such as complicated and expensive devices, and troublesome maintenance. Since the lubricating oil has a high viscosity, it cannot be completely removed from the hydrostatic bearing portion, and may remain in a narrow land portion, and it is difficult to exhibit the initial performance. In view of the above, an object of the present invention is to realize a hydrostatic bearing that can reduce friction resistance at high speed rotation and increase supporting rigidity at low speed rotation with a simpler device. [0009] At least two kinds of working fluids are placed on a hydrostatic bearing which can be used by switching between them. As a pressure fluid, compressed air is used at high speeds, and low speed rotations requiring high support rigidity are required. In case of using water. Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, a plurality of static pressure pockets 5a to 5d are formed on the inner surface of a cylindrical bearing body 2, and a supply portion 4a of compressed fluid is provided in each of the static pressure pockets 5a to 5d.
To 4d. The compressed air is compressed by the compressor 14 and sent to one supply port of the three-way valve 13 via the accumulator 15. On the other hand, water 10 in the tank 9 is pressurized by the pump 11 and sent to the other supply port of the three-way valve 13 through the piping system 12. Therefore, in the case of a high-speed rotation, for example, in order to reduce frictional resistance, the three-way valve 13 is set so as to send compressed air having a low viscosity, and the three-way valve 13 is supplied from each of the supply parts 4a to 4d to the static pressure pockets 5a to 5d. The rotating shaft 1 that is inserted into the bearing body 2 is rotatably supported. The supplied compressed air is supplied to an outlet 6a formed in an unformed portion of the static pressure pocket.
6d, the recovery path 7 provided between the bearing body 2 and the outer cylinder 3 is dissipated into the air from an opening 8a provided at the upper part of the outer cylinder. Further, for example, when it is desired to increase the supporting rigidity, the three-way valve 13 is switched so that high-viscosity water is pumped up by the pump 11 and sent from each of the supply units 4a to 4d along the same route as the compressed air. The rotary shaft 1 is supplied to the pockets 5a to 5d and inserted into the bearing body 2 to freely rotate.
The supplied water enters the recovery path 7 provided between the bearing main body 2 and the outer cylinder 3 from the discharge ports 6a to 6d formed in the unformed part of the static pressure pocket, and collects at the lower part by gravity. It returns to the tank 9 via the drainage pipe 18 from the release port 8b provided in the lower part of the outer cylinder 3. The use of water as a liquid is less dangerous than fire with other low-viscosity fluids, such as gasoline, and is easier to handle. No air bubbles are mixed in. Also, when switching from water to compressed air, water evaporates.For example, when switching from water to compressed air, water can be completely removed from the hydrostatic bearing by sending compressed air heated first. This is because there is an effect. According to the present invention, by switching between compressed air and water as a working fluid, it is a simple device, high speed rotation, low friction, high bearing rigidity in a low speed range, and a wide range of static pressure. There is an effect that a bearing can be realized. In this example, a rotary type hydrostatic bearing is described, but the same effect can be obtained with a direct acting type.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a hydrostatic bearing according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a conventional hydrostatic bearing. FIG. 3 is a diagram showing a configuration of a conventional hydrostatic bearing using a plurality of liquids. [Description of reference numerals] 1, 21, 41 Rotation axis 11, 3
1,51,61 Pump 2,22,42 Bearing body 13,5
3, 63 Three-way valve 3 Outer cylinder 14 Compressor 4, 24, 44 Supply unit 15 Accumulator 5, 25, 45 Static pressure pocket 6, 26, 46 Discharge port 8 Release port

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Claims (1)

Claims: 1. A compressed air is supplied as a pressurized fluid to be supplied into a static pressure pocket in a hydrostatic bearing in which a fluid under pressure is supplied between two objects and one of them supports the other. Hydrostatic bearing characterized by switching between water and water.