Air hydrostatic bearing

Abstract

The objective of the present invention is to provide an air hydrostatic bearing that has a simple structure and can ensure the desired bearing rigidity even when the bearing clearance changes. [Solution] An air hydrostatic bearing 1 has an air supply device 30 that supplies air A to the bearing portion 11 and a control device 40 that controls the air supply device 30, wherein the air supply device 30 has a plurality of air supply systems 31, 32, and each of the air supply systems 31, 32 can be switched between an air supply state and a stopped state, and the control device 40 reduces the number of air supply systems that are in the air supply state when the bearing clearance decreases.

Description

Technical Field

[0001] The present invention relates to an air static pressure bearing.

Background Art

[0002] An air static pressure bearing is used as a bearing mechanism. The air static pressure bearing is used not only to support the radial load or thrust load of a rotating shaft, but also to support the load of a linear moving part such as a linear guide. In an air static pressure bearing, in order to obtain a desired bearing rigidity, it is necessary to appropriately design conditions such as the throttle hole diameter, the number of holes, and the bearing clearance of the air supply. Among these design conditions, the bearing clearance changes due to thermal deformation and centrifugal force during operation, and as a result, the desired rigidity cannot be obtained. In response to such changes in the bearing clearance due to thermal deformation and centrifugal force, in a hydrodynamic bearing, a countermeasure using a variable throttle mechanism has been taken (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the above-described variable throttle mechanism is applied to an air static pressure bearing to cope with changes in the bearing clearance due to thermal deformation and centrifugal force, there are the following problems. In air hydrostatic bearings, since compressible air is used, self-excited vibration (pneumatic hammer phenomenon) can occur if the bearing clearance is narrowed to the point where it forms a surface throttling, if a large pocket is provided, or if the effective bearing area is large relative to the flow rate, making it impossible to maintain bearing accuracy. To prevent such pneumatic hammer phenomenon, it is necessary to suppress the volume of air in between, and for that purpose, the bearing clearance and the variable throttling mechanism must be brought close together. However, the installation space available around the bearing is limited, making it difficult to install the variable throttling mechanism while preventing the pneumatic hammer phenomenon. While attempts have been made to construct small variable apertures using piezoelectric elements and to employ variable aperture mechanisms with minute structures, problems such as structural complexity and manufacturing costs remain unavoidable.

[0005] The object of the present invention is to provide an air hydrostatic bearing that has a simple structure and can ensure the desired bearing rigidity even when the bearing clearance changes. [Means for solving the problem]

[0006] The air hydrostatic bearing of the present invention is an air hydrostatic bearing having an air supply device that supplies air to the bearing portion and a control device that controls the air supply device, wherein the air supply device has a plurality of air supply systems, each of the air supply systems can be switched between an air supply state and a stopped state, and the control device reduces the number of air supply systems in the air supply state when the bearing clearance decreases.

[0007] In the present invention, the multiple air supply systems can be piping or conduits that can supply air from an air supply source to the bearing section at a predetermined flow rate and can be switched between an air supply state and a stopped state (closed state) using a solenoid valve or the like. Each of the multiple air supply systems has an air supply port that opens to the bearing surface or a static pressure pocket facing the bearing section, and it is preferable that the air supply ports of each system are evenly distributed on the bearing surface. It is preferable that the groups of air supply ports of the multiple air supply systems are arranged superimposed on the same bearing surface, and that the amount of air supplied to the bearing section increases substantially uniformly across the entire bearing surface by increasing the number of air supply systems that are in an air supply state.

[0008] In this invention, by keeping some of the multiple air supply systems in an air supply state while keeping others in a stopped state, a predetermined flow rate of air suitable for the bearing gap is supplied to the bearing from the air supply system in the air supply state, thereby ensuring the desired bearing rigidity in the bearing. In other words, when the bearing clearance decreases in the bearing section due to thermal deformation or centrifugal force, the control device switches a portion of the air supply system that is currently supplying air to a stopped state, reducing the number of air supply systems that are currently supplying air. This reduces the flow rate of air supplied to the bearing section, and the desired bearing rigidity is maintained in the bearing section. On the other hand, when the bearing clearance increases in the bearing section, the control device switches the air supply system, which was in a stopped state, to an air supply state, thereby increasing the amount of air supplied to the bearing section and maintaining the desired bearing rigidity in the bearing section. Thus, in the air hydrostatic bearing of the present invention, the desired bearing rigidity can be ensured even when the bearing clearance changes. In other words, by using multiple air supply systems and intermittently supplying some of them, the range of bearing rigidity provided by each system can be connected and expanded. Furthermore, as described above, by ensuring bearing rigidity against changes in bearing clearance, it becomes unnecessary to use variable aperture mechanisms in multiple air intake systems, thereby preventing structural complexity caused by variable aperture mechanisms and preventing the pneumatic hammer phenomenon associated with the complexity or size of variable aperture mechanisms. As described above, the present invention provides an air hydrostatic bearing that has a simple structure and can ensure the desired bearing rigidity even when the bearing clearance changes.

[0009] In the air hydrostatic bearing of the present invention, it is preferable that the control device has a gap sensor for detecting the value of the bearing gap. In this invention, the control device can use the bearing gap value obtained from the gap sensor to control the switching of multiple air supply systems. As a result, the control by the control device can be made appropriate according to the actual bearing gap of the bearing section.

[0010] In the air hydrostatic bearing of the present invention, it is preferable that the air supply system has a valve device that switches between the air supply state and the stopped state by intermittently interrupting the flow of air under the control of the control device. In this invention, the switching control of the air supply system can be easily performed by a control device using a valve device such as a solenoid valve.

[0011] In the air hydrostatic bearing of the present invention, the control device may reduce the number of air supply systems in the air supply state by switching one of the air supply systems from the air supply state to the stopped state when the value of the bearing clearance falls below a predetermined reference clearance value. In this invention, by using a predetermined reference gap, the switching control of multiple air supply systems in the control device can be easily and reliably performed.

[0012] In the air hydrostatic bearing of the present invention, it is preferable that the control device sets the reference gap for each of the air supply systems, and the value of the reference gap is such that the bearing gap stiffness characteristic when the air supply system is in the stopped state and the bearing gap stiffness characteristic when the air supply system is in the air supply state are the same. In this invention, the control device can easily set a reference gap that serves as the basis for operation in switching control of multiple air supply systems. In particular, the bearing clearance stiffness characteristics of each of the multiple air supply systems, that is, the relationship between bearing clearance and bearing stiffness, can be obtained by measurement or calculation, and the reference gap for switching operations of the air supply systems can be set efficiently from the obtained characteristic data.

[0013] In the air hydrostatic bearing of the present invention, it is preferable that the control device performs control to predict the value of the bearing clearance from the operating conditions of the bearing section. In this invention, the control device predicts the bearing clearance value based on data indicating the operating status of the bearing section (the operating state of the machine in which the bearing section is installed), and uses this value to control the switching of multiple air supply systems. For example, if the air supply pressure and the number of supply systems are constant, the clearance will be determined once the air flow rate is determined. Therefore, if the relationship between the flow rate and the clearance is measured in advance, the clearance can be estimated from the flow rate. Alternatively, the relationship between the rotational speed, the temperature of each part of the main shaft, and the clearance may be measured multiple times in advance, and the clearance may be calculated from the rotational speed and temperature using an AI (artificial intelligence) system that has been trained on this data. By using predicted values ​​of bearing clearance when controlling the switching of the air supply system by the control device, it is possible to omit clearance sensors and other devices that would otherwise be required to obtain actual measured values, and to perform switching control of multiple air supply systems in advance of actual fluctuations in bearing clearance. As a control method for predicting such bearing clearance values, it is possible to appropriately use a method of obtaining the bearing clearance values ​​for each operating condition of the air hydrostatic bearing by actual measurement or calculation, and then creating a database or training the database. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an air hydrostatic bearing that has a simple structure and can ensure the desired bearing rigidity even when the bearing clearance changes. [Brief explanation of the drawing]

[0015] [Figure 1] A partially broken perspective view showing a first embodiment of the present invention. [Figure 2] A schematic diagram showing the planar arrangement of the bearing section and the air supply system of the first embodiment. [Figure 3] A graph showing the switching control of the air supply system in the first embodiment. [Figure 4] A graph showing the switching control of a modified example of the first embodiment. [Figure 5] A schematic diagram showing the planar arrangement of the bearing section and the air supply system of the second embodiment of the present invention. [Figure 6] Schematic diagram showing the elevation arrangement of the bearing portion and the air supply system of the second embodiment.

Mode for Carrying Out the Invention

[0016] 〔First Embodiment〕 Figures 1 and 2 show the aerostatic bearing 1 of the first embodiment of the present invention. In Figure 1, the aerostatic bearing 1 has a shaft member 10 arranged along the rotation axis C and a bearing member 20 that rotatably supports the shaft member 10. An aerostatic bearing portion 11 having a predetermined bearing clearance is formed between the inner peripheral surface of the bearing member 20 and the outer peripheral surface of the shaft member 10. The bearing portion 11 has the inner peripheral surface of the bearing member 20 as the bearing surface, and by supplying pressurized air to this bearing surface, the shaft member 10 is supported in a non-contact manner.

[0017] In order to supply pressurized air to the bearing portion 11, a plurality of ventilation pipelines 21 extending in the radial direction with respect to the rotation axis C are formed in the bearing member 20. The inner end of the ventilation pipeline 21 is a supply port 22 that opens to the inner peripheral surface of the bearing member 20. A plurality of supply ports 22 are arranged in the circumferential direction around the rotation axis C on the inner peripheral surface of the bearing member 20. In the middle of the ventilation pipeline 21, in the vicinity of the supply port 22, a fixed throttle portion 23 necessary for functioning as an aerostatic bearing is formed. Separating the supply port 22 and the throttle portion 23 is the case of an orifice throttle or a capillary throttle, and in the case of a self-forming throttle method, the function of the throttle portion 23 is integrally formed at the supply port 22. Outside the ventilation pipeline 21, an air supply device 30 is connected to supply pressurized air A to the bearing portion 11.

[0018] In Figure 2, the air supply device 30 has an air supply source 39 that supplies pressurized air A and a plurality of air supply systems 31, 32 that supply the pressurized air A from the air supply source 39 to the bearing portion 11. The first air supply system 31 has a distribution pipeline 311 outside the bearing member 20. The second air supply system 32 has a distribution pipe passage 321 on the outside of the bearing member 20. The ventilation pipes 21 formed in the bearing member 20 are connected to either the distribution pipes 311 or 321.

[0019] The air inlet 22 of the ventilation pipe 21 connected to the distribution pipe 311 is designated as the air inlet 221 of the first air supply system 31. The air inlet 22 of the ventilation pipe 21 connected to the distribution pipe 321 is designated as the air inlet 222 of the second air supply system 32. In this embodiment, one-third of the multiple air intake ports 22 are designated as the first air intake system 31, and two-thirds are designated as the second air intake system 32. On the inner circumferential surface of the bearing member 20 facing the bearing portion 11, a repeating arrangement of air intake ports 221, air intake ports 222, and air intake ports 222 is formed in the circumferential direction.

[0020] In the first air supply system 31, pressurized air A from the air supply source 39 is constantly supplied to the air inlet 221. In the second air supply system 32, an openable / closable solenoid valve 322 is installed in the middle, allowing the pressurized air A supplied from the air supply source 39 to the air inlet 222 to be intermittently supplied. The air supply device 30 has a control device 40 for switching control of the solenoid valve 322, and a gap sensor 41 for detecting the bearing gap of the bearing section 11.

[0021] The control device 40 is configured using an embedded microcomputer system and switches the solenoid valve 322 on and off according to the result of comparing the bearing gap value detected by the gap sensor 41 with a predetermined reference gap, which will be described later. The control device 40 may have other configurations; for example, it may utilize part of the control system of the device in which the air hydrostatic bearing 1 is installed.

[0022] The predetermined reference gap in the control device 40 described above is set by the following procedure. When setting the reference clearance, first the air hydrostatic bearing 1 is activated and the correlation between the bearing clearance and bearing stiffness between the shaft member 10 and the bearing member 20 is measured. In Figure 3, when the solenoid valve 322 is closed and pressurized air A is supplied to the bearing section 11 only by the first air supply system 31, the bearing clearance and bearing rigidity between the shaft member 10 and the bearing member 20 are as shown in data series R2 (indicated by ◇). When the solenoid valve 322 is open and pressurized air A is supplied to the bearing section 11 by the first air supply system 31 and the second air supply system 32, the bearing clearance and bearing rigidity between the shaft member 10 and the bearing member 20 are as shown in data series R1 (□).

[0023] As shown in Figure 3, when pressurized air A is supplied to the bearing section 11 by both the first air supply system 31 and the second air supply system 32, a larger amount of pressurized air A is supplied to the bearing section 11 than when supplied by the first air supply system 31 alone, resulting in high bearing rigidity even in regions with relatively small bearing clearances. On the other hand, when pressurized air A is supplied to the bearing section 11 by both the first air supply system 31 and the second air supply system 32, the bearing rigidity becomes lower in regions with relatively large bearing clearances than when supplied by the first air supply system 31 alone, and the data sequences R1 and R2 intersect at the value Cr. This value Cr is set as the reference clearance in the control device 40. In setting the reference gap as described above, it is ideal to measure the correlation by detecting the change in bearing stiffness when the bearing gap between the shaft member 10 and the bearing member 20 changes. However, in radial bearings, the bearing gap is radial, making it difficult to change the gap with the same shaft member 10 and bearing member 20. Therefore, by preparing multiple shaft members 10 with different diameters and sequentially measuring the bearing gap and bearing stiffness of each, the correlation between the bearing gap and bearing stiffness can be measured.

[0024] When the bearing gap detected by the gap sensor 41 is less than the reference gap Cr, the control device 40 closes the solenoid valve 322 and supplies pressurized air A to the bearing section 11 only through the first air supply system 31. As a result, the bearing section 11 obtains the bearing rigidity shown in data series R2 in Figure 3. On the other hand, when the bearing gap detected by the gap sensor 41 is greater than or equal to the reference gap Cr, the solenoid valve 322 is opened and pressurized air A is supplied to the bearing section 11 by the first air supply system 31 and the second air supply system 32. As a result, the bearing rigidity shown in data series R1 of Figure 3 is obtained in the bearing section 11. In this way, the control device 40 switches the air supply state at the reference gap Cr, thereby obtaining the bearing stiffness characteristic Rm (shown as a solid line in Figure 3) in the bearing section 11 by combining the data series R1 and R2.

[0025] This embodiment provides the following effects. In this embodiment, by keeping the first air supply system 31 (part of multiple air supply systems) in an air supply state while keeping the second air supply system 32 (another part) in a stopped state, a predetermined flow rate of pressurized air A is supplied to the bearing section 11, and the desired bearing clearance is formed in the bearing section 11. When the bearing clearance in the bearing section 11 decreases due to thermal deformation or centrifugal force, the control device 40 refers to the detection signal from the clearance sensor 41 and switches the supply air system 32, which is in the supply air state, to the stopped state, thereby reducing the number of supply air systems. In other words, the system switches from supplying air through two systems, the first supply air system 31 and the second supply air system 32, to supplying air through only one system, the first supply air system 31. As a result, the flow rate of pressurized air A supplied to the bearing section 11 decreases, and the desired bearing rigidity can be maintained in the bearing section 11. On the other hand, when the bearing clearance in the bearing section 11 decreases, the control device 40 refers to the detection signal from the clearance sensor 41 and switches the air supply system 32, which was in a stopped state, to an air supply state, thereby increasing the amount of pressurized air A supplied to the bearing section 11 and maintaining the desired bearing rigidity in the bearing section 11.

[0026] Thus, in the air hydrostatic bearing 1 of this embodiment, the desired bearing rigidity can be ensured even if the bearing clearance changes. In other words, by using multiple air supply systems 31 and 32 and partially interrupting them, the range of bearing rigidity provided by each air supply system 31 and 32 can be connected and expanded. Furthermore, as described above, by ensuring bearing rigidity against changes in bearing clearance, it becomes unnecessary to use a variable aperture mechanism in multiple air supply systems 31 and 32, thereby preventing structural complexity caused by the variable aperture mechanism and preventing the pneumatic hammer phenomenon associated with the complexity or size of the variable aperture mechanism. As described above, this embodiment provides an air hydrostatic bearing 1 that has a simple structure and can ensure the desired bearing rigidity even when the bearing clearance changes.

[0027] In this embodiment, the control device 40 can use the bearing gap value obtained by the gap sensor 41 to control the switching of multiple air supply systems 31 and 32. As a result, the control by the control device 40 can be made appropriate according to the actual bearing gap of the bearing section.

[0028] In this embodiment, the second air supply system 32 used a solenoid valve 322 that intermittently interrupted the flow of air using an electrical signal to switch between an air supply state and a stopped state by the control device 40. This allowed for a simplified control system configuration and facilitated switching control of the air supply system by the control device 40.

[0029] In this embodiment, the control device 40 reduces the number of air supply systems 31 and 32 in the air supply state by switching the second air supply system 32 (one of the air supply systems) from the air supply state to the stopped state when the bearing clearance value falls below a predetermined reference clearance Cr value. In this way, by using a predetermined reference clearance Cr, the control device 40 can easily and reliably control the switching of multiple air supply systems 31 and 32.

[0030] In this embodiment, the control device 40 has a reference gap Cr set for the second air supply system 32, and the value of the reference gap Cr is set to the gap value at which the bearing gap stiffness characteristics (data series R1) when the second air supply system 32 is in an air supply state and the bearing gap stiffness characteristics (data series R2) when the second air supply system 32 is in a stopped state are the same. By doing this, the reference gap Cr, which serves as the basis for operation when the control device 40 controls the switching of multiple air supply systems, can be easily set. In particular, the reference gap can be set efficiently by obtaining the bearing gap stiffness characteristics of each of the multiple air supply systems, that is, the relationship between bearing gap and bearing stiffness, by measurement or calculation, and setting the reference gap for switching operations of the air supply systems from the obtained characteristic data.

[0031] [Modification of the first embodiment] In the first embodiment described above, a first air supply system 31 that continuously supplies air and a second air supply system 32 that can be switched between a stopped state and an air supply state by a solenoid valve 322 are provided as multiple air supply systems, and a reference gap Cr is used for switching the second air supply system 32. In contrast to this first embodiment, three or more air supply systems may be used, and the amount of air supplied may be increased by sequentially increasing the number of air supply systems in the air supply state from one.

[0032] In Figure 4, for example, in an air supply device having four air supply systems, the bearing clearance and bearing stiffness when each system is sequentially switched to the air supply state are given by the data series R1 to R4. Specifically, data series R4 represents the case where only the first system is supplied with air, and the other systems are stopped. Data series R3 represents the case where the first and second systems are supplied with air, and the third and fourth systems are stopped. Data series R4 represents the case where the first to third systems are supplied with air, and the fourth system is stopped. Data series R1 represents the case where all systems from the first to the fourth systems are supplied with air. In such an air supply device, the intersection points of each data series can be obtained using the same procedure as in the first embodiment, and the bearing gap values ​​at each point can be used as the reference gap. Specifically, the reference gap Cr4 is calculated from the bearing gap value at the intersection of data series R4 and data series R3, and this reference gap Cr4 can be used as a switching criterion when switching from a state where only the first system is supplied to a state where both the first and second systems are supplied. Similarly, the reference gap Cr3 is obtained from the intersection of data series R2 and R3, and the reference gap Cr2 is obtained from the intersection of data series R1 and R2, and these can be used as criteria when sequentially switching the third and fourth systems to a state where they are supplied, respectively.

[0033] [Second Embodiment] Figures 5 and 6 show an air hydrostatic bearing 2 according to a second embodiment of the present invention. The air hydrostatic bearing 1 of the first embodiment described above was a radial bearing. That is, a bearing portion 11 was formed between the surface of the shaft member 10 and the inner circumference of the bearing member 20, and air intake ports 22 for supplying air to the bearing portion 11 were arranged circumferentially on the inner surface of the bearing member 20. In contrast, the air hydrostatic bearing 2 of this embodiment is a thrust bearing, with a disc portion 12 formed on the shaft member 10A, and a bearing portion 13 formed between the disc portion 12 and the surface of the bearing member 20A facing it. On the surface of the bearing member 20A facing the bearing portion 13, a plurality of air intake ports 22 for supplying air to the bearing portion 13 are arranged in an annular shape around the rotation axis C of the shaft member 10A.

[0034] The bearing member 20A has a ventilation pipe 21 that communicates with a plurality of air intake ports 22. A fixed throttling section 23 is formed in the ventilation pipe 21 near the air intake ports 22. These air intake ports 22, ventilation pipe 21, and throttling section 23 are the same as those in the first embodiment described above, although their arrangements differ. An air supply device 30A for supplying pressurized air A to the bearing section 13 is connected to the end of the ventilation pipe 21 opposite to the air inlet 22.

[0035] The air supply device 30A has an air supply source 39 that supplies pressurized air A, and also has a plurality of air supply systems 31, 32, and 33 that supply pressurized air A from the air supply source 39 to the bearing section 13. That is, in the first embodiment described above, two air supply systems 31 and 32 were used, but in this embodiment, three air supply systems 31 to 33 are used. The first to third air supply systems 31, 32, and 33 each have distribution pipes 311, 321, and 331 near the bearing member 20A, respectively. The ventilation pipes 21 formed in the bearing member 20A are each connected to one of the distribution pipes 311, 321, and 331.

[0036] The air inlet 22 of the ventilation pipe 21 connected to the distribution pipe 311 is designated as the air inlet 221 of the first air supply system 31. The air inlet 22 of the ventilation pipe 21 connected to the distribution pipe 321 is designated as the air inlet 222 of the second air supply system 32. The air inlet 22 of the ventilation pipe 21 connected to the distribution pipe 331 is designated as the air inlet 223 of the third air supply system 33. In this embodiment, the multiple air intake ports 22 are distributed equally among the air intake systems 31 to 33, with each receiving 1 / 3 of the ports. On the surface of the bearing member 20A facing the bearing portion 13, a repeating arrangement of air intake ports 221, 222, and 223 is formed in the circumferential direction.

[0037] The air supply device 30A is equipped with solenoid valves 312, 322, and 332 for each of the first to third air supply systems 31, 32, and 33, respectively, and can intermittently supply pressurized air A from the air supply source 39 to each air supply system 31, 32, and 33. These solenoid valves 312, 322, and 332 are switched and controlled by the control device 40A.

[0038] The control device 40A may determine the measured gap from the gap sensor 41 based on the reference gap Cr as described in the first embodiment above when controlling the switching of the first to third air supply systems 31, 32, and 33. Alternatively, it may predict the value of the bearing gap based on data indicating the operating status of the bearing section 13 (the operating status of the machine equipment on which the bearing section 13 is installed), and use this value to control the switching of the first to third air supply systems 31 to 33. As a control method for predicting such bearing clearance values, it is possible to appropriately use a method of obtaining the bearing clearance values ​​for each operating condition of the air hydrostatic bearing by actual measurement or calculation, and then creating a database or training the database.

[0039] According to this embodiment, in addition to the same effects as the first embodiment described above, the following effects can be obtained. In this embodiment, the thrust bearing can bear a load in the direction of the rotation axis C. Thus, the air hydrostatic bearing of the present invention can be configured as a radial bearing, such as the air hydrostatic bearing 1 of the first embodiment, and as a thrust bearing, such as the air hydrostatic bearing 2 of this embodiment.

[0040] In this embodiment, by using predicted values ​​of the bearing gap when controlling the switching of the first to third air supply systems 31, 32, and 33 by the control device 40A, it is possible to omit the gap sensor 41 and other devices that would otherwise be required to obtain measured values, and to perform the switching control of the first to third air supply systems 31, 32, and 33 prior to actual fluctuations in the bearing gap.

[0041] In this embodiment, solenoid valves 312, 322, and 332 are provided in each of the first to third air supply systems 31, 32, and 33, respectively, so that continuous air supply or minimal air supply can be performed by any of the air supply systems 31, 32, and 33. That is, in the first embodiment described above, continuous air supply was fixed to the first air supply system 31, but in this embodiment, continuous air supply may be set to any of the first to third air supply systems 31, 32, and 33.

[0042] [Other embodiments] The first and second air supply systems 31, 32 in the first embodiment, or the first to third air supply systems 31, 32, 33 in the second embodiment, are not limited to supplying pressurized air A at the same flow rate; for example, the first and second air supply systems 31, 32 may be set to have different flow rates. In the embodiments described above, solenoid valves 312, 322, and 332 were used as switching valves for each air supply system, but other types of valve devices may be used as long as they allow switching between the systems. [Industrial applicability]

[0043] This invention can be used in air-hydrostatic bearings. [Explanation of Symbols]

[0044] 1,2...Air hydrostatic bearing, 10,10A...Shaft member, 11,13...Bearing section, 12...Disc section, 20,20A...Bearing member, 21...Ventilation pipe, 22,221,222,223...Air inlet, 23...Throttle section, 30,30A...Air supply device, 31...First air supply system, 311,321,331...Distribution pipe, 312,322,332...Solenoid valve, 32...Second air supply system, 33...Third air supply system, 39...Air supply source, 40,40A...Control device, 41...Gap sensor, A...Pressurized air, C...Rotating shaft, Cr,Cr2,Cr3,Cr4...Reference gap, R1,R2,R3,R4...Data series, Rm...Bearing stiffness characteristics.

Claims

1. An air-hydrostatic bearing comprising an air supply device for supplying air to the bearing portion and a control device for controlling the air supply device, The aforementioned air supply device has multiple air supply systems, Each of the aforementioned air supply systems can be switched between an air supply state and a stopped state. The control device is an air-static bearing that reduces the number of air supply systems in the air supply state when the bearing clearance decreases.

2. In the air hydrostatic bearing described in claim 1, The control device is an air-static bearing having a gap sensor for detecting the value of the bearing gap.

3. In the air hydrostatic bearing described in claim 1, The air supply system is an air hydrostatic bearing having a valve device that switches between the air supply state and the stopped state by intermittently interrupting the flow of air under the control of the control device.

4. In the air hydrostatic bearing according to any one of claims 1 to 3, The control device reduces the number of air supply systems in the air supply state by switching one of the air supply systems from the air supply state to the stopped state when the value of the bearing clearance falls below a predetermined reference clearance value.

5. In the air hydrostatic bearing described in claim 4, The control device is an air hydrostatic bearing in which the reference gap is set for each of the air supply systems, and the value of the reference gap is such that the bearing clearance stiffness characteristic when the air supply system is in the stopped state and the bearing clearance stiffness characteristic when the air supply system is in the supply state are the same.

6. In the air hydrostatic bearing described in claim 1, The control device is an air-hydrostatic bearing that performs control to predict the value of the bearing clearance from the operating conditions of the bearing section.

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