JP2004019760A - Hydrostatic bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrostatic bearing having a simplified and low-cost constitution. <P>SOLUTION: In the passage of a fluid as a throttle, the values of a, b, L are suitably determined to adjust the flow rate Q in the (1') formula. Accordingly, in designing a hydrostatic bearing, the quantity of a supplied fluid and the dimensions of the respective parts of a guide 2 are adjusted to provide the hydrostatic bearing not damaging the atmosphere of a process chamber P even if a groove open to the atmosphere is omitted. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrostatic bearing used for high-precision positioning in a vacuum atmosphere or a special gas atmosphere, for example.
[0002]
[Prior art]
2. Description of the Related Art In a semiconductor manufacturing apparatus and the like, a processing operation and an inspection are performed by placing a work on a moving member such as a table and moving and rotating the work in a process chamber maintained in a vacuum atmosphere. Here, in recent years, as semiconductors to be manufactured have become finer, it has been necessary to further increase the degree of vacuum in the process chamber.
[0003]
When a driving device for moving a moving member is provided in such a process chamber, high-precision positioning is required. Also, if the moving member is movably supported by using a rolling bearing, for example, the lubricant or the like may be scattered in the process chamber or the rolling may generate dust. It is. Therefore, a hydrostatic bearing that supports a moving member using a fluid such as a gas instead of a rolling element has been developed (see Japanese Patent No. 2602648 and Japanese Patent No. 2587227).
[0004]
[Problems to be solved by the invention]
By the way, since the hydrostatic bearing in such an application supports a moving member in a non-contact state by supplying gas or the like from the outside with a pump or the like, for example, if the process chamber is in a vacuum state, A system for recovering the gas supplied to the hydrostatic bearing is required so as not to impair the degree of vacuum. Therefore, in the above-described hydrostatic bearing of the cited example, the air release groove is disposed adjacent to the hydrostatic bearing and communicates with the outside of the process chamber. And a negative pressure groove connected to the source.The gas that overflows from the static pressure bearing flows out to the outside through the open-to-atmosphere groove, and gas that cannot be recovered in the open-to-atmosphere groove is removed by the negative-pressure groove. Gas recovery is performed in two stages, such as recovery.
[0005]
However, providing two types of grooves in this way makes the configuration of the housing in which the hydrostatic bearings are provided larger and more complicated, and increases the number of pipings to the outside of the process chamber. is there. Note that the above-described problem may occur not only when the process chamber is in a vacuum atmosphere, but also when it is necessary to regulate the amount of discharge from the bearing even in the atmosphere, for example.
[0006]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a hydrostatic bearing having a more simplified and low-cost configuration.
[0007]
[Means for Solving the Problems]
The hydrostatic bearing of the present invention,
In a hydrostatic bearing for supporting the second member movably with respect to the first member,
A bearing portion provided on one of the first member and the second member and connected to an external fluid supply source;
A differential pressure chamber disposed adjacent to and surrounding the bearing portion, and further connected to an external negative pressure source;
Fluid leaked from the bearing portion is to be collected in the differential pressure chamber,
It is characterized in that the bearing section and the differential pressure chamber do not communicate with the outside.
[0008]
[Action]
The hydrostatic bearing according to the present invention is a hydrostatic bearing for supporting a second member (for example, a slider) so as to be displaceable with respect to a first member (for example, a guide), wherein the first member and the second member are connected to each other. And a bearing portion (for example, a concave portion or a large-diameter portion) connected to an external fluid supply source (for example, a positive pressure pump), and disposed adjacent to and surrounding the bearing portion. A differential pressure chamber connected to a pressure source (for example, a negative pressure pump); fluid leaking from the bearing portion is collected in the differential pressure chamber; Since the space between the pressure member and the pressure chamber is not communicated with the outside, the second member can be supported without impairing the external environment of the first member. Since there is no need to provide an open-to-atmosphere groove for communication, the configuration is simplified and the It can be miniaturized and low-cost.
[0009]
Consider the principles of the present invention. FIG. 1 is a diagram showing a modeled configuration of the present invention. FIG. 2 is a cross-sectional view showing a model of the configuration of the related art. In FIG. 1, a slider 1 is disposed on a guide 2. A bearing 1a is formed at the center of the lower surface of the slider 1 in FIG. The bearing 1a is connected to an external positive pressure pump. On the lower surface of the slider 1, a groove-shaped first differential pressure chamber 1b is continuously formed so as to surround the bearing portion 1a, and further, a groove-shaped second differential pressure chamber 1b is formed so as to surround the first differential pressure chamber 1b. The differential pressure chamber 1c is formed continuously. The first differential pressure chamber 1b is connected to an external first negative pressure pump, and the second differential pressure chamber 1c is connected to an external second negative pressure pump. In the configuration of FIG. 1 according to the present invention, the space between the bearing portion 1a and the first differential pressure chamber 1b (partition wall 1e) does not communicate with the outside to form a closed space. 2 only differs in that the space between the bearing portion 1a and the first differential pressure chamber 1b is opened to the outside via the atmosphere opening groove 1d.
[0010]
In the configuration of FIGS. 1 and 2, a fluid (for example, gas) is supplied into the bearing 1 a from the positive pressure pump, so that the pressure in a portion between the opposing surfaces of the bearing 1 a and the guide 2 increases. Thereby, the slider 1 can be floated with respect to the guide 2 and supported in a non-contact state. The slider 1 is movable in a direction indicated by an arrow (or a direction perpendicular thereto) by a driving device (not shown). Although the case where the slider 1 is a moving unit is discussed, the same applies to the case where the guide 2 is a moving unit. Alternatively, the present invention can also be applied to a case where a rotational displacement is possible instead of a movable state.
[0011]
Here, the fact that the slider 1 is supported in a non-contact state with respect to the guide 2 means that there is a gap between the guide 2 and the slider 1. Will leak to the surroundings through such a gap. For example, when the above-described hydrostatic bearing is provided in a chamber C which is a process chamber P whose inside is maintained in a vacuum atmosphere, such a fluid enters the process chamber P, and thereby the atmosphere is reduced. May be damaged. Therefore, in the case of the prior art shown in FIG. 2, the fluid leaking from the bearing portion 1a is first captured by the open-to-atmosphere groove 1d and flows out of the chamber C. The atmosphere in the process chamber P is protected by being captured in the chamber 1b and forcibly sucked out of the chamber C.
[0012]
On the other hand, in the case of the present invention according to FIG. 1, the structure of the slider 1 can be simplified and the number of pipes can be reduced by omitting the open-to-atmosphere groove 1d (FIG. 2). Moreover, the size of the slider 1 can be reduced. However, simply omitting the open-to-atmosphere groove requires collecting all leaked fluid with the first negative pressure pump, and an increase in the capacity is indispensable, which leads to an increase in cost. . Therefore, control of the amount of fluid leaking from the bearing 1a will be considered. As a result of intensive studies, the present inventors have invented a more preferable technical form of a hydrostatic bearing that can achieve a reduction in size and an increase in sealing performance by appropriately controlling the amount of fluid leakage. Such a hydrostatic bearing will be described.
[0013]
In the above-described hydrostatic bearing, the consumption flow rate of the bearing is limited to a predetermined amount (for example, Q described later). First, what should be obtained is the amount of gas leaking from the open-to-atmosphere groove 1d to the differential pressure chamber 1b in the model shown in FIG.
[0014]
FIG. 3 is a diagram modeling a passage through which a fluid flows from the high pressure side to the low pressure side between the parallel plates. In FIG. 3, although not shown, the upper surface of the passage is shielded by a slider (not shown), that is, the passage has a rectangular cross section. Here, when the height of the passage (the size of the minute gap) is a, the width is b, and the length is L, the fluid flowing through the passage is assumed to be a viscous flow, and is considered as a two-dimensional Poiseuille flow. , Its flow rate Q
Q = a ³ b (Po ² -Ph ² ) / (12 μL) [Pa · m ³ / S] (1)
Can be represented by Po is the pressure on the high pressure side (atmospheric pressure), Ph is the pressure on the differential pressure chamber side (pressure close to vacuum), and μ is the viscosity of the fluid (1.82 × 10 2 at 20 ° C. in the case of air). ^-5 [Pa · s]), but when applied to the hydrostatic gas bearing of FIG. 2, the pressure in the differential pressure chamber 1b is sufficiently small. ² >> Ph ² So, Po ² -Ph ² ≒ Po ² Therefore, equation (1) is as follows.
Q = a ³ b ・ Po ² / (12 μL) [Pa · m ³ / S] (1 ')
[0015]
Here, since Po and μ are constants, Q in the model of FIG. 3 is uniquely determined using a, b, and L as variables. The above equation (1) or (1 ′) is for the model of FIG. 3, and when the shape of the passage changes, for example, concentric as shown in FIG. I do. However, there is no problem if the above equation (1) or (1 ′) is approximately applied. Here, in a steady state, if the flow rate of the gas discharged from the bearing portion 1a (bearing consumption flow rate) is suppressed to be lower than the flow rate Q of the equation (1 ′), high sealing performance can be obtained even if the open-to-atmosphere groove is omitted. Can be obtained, which is preferable. In other words, the flow rate Q of the equation (1 ′) is determined by appropriately determining a, b, and L of the seal portion. Therefore, when designing a hydrostatic bearing, the consumption flow rate of the bearing is reduced by the above (1 ′). The flow rate can be set to be equal to or less than the flow rate Q obtained by the equation. In this case, the atmosphere in the process chamber P is not impaired even if the air release groove is omitted and only the two stages of the differential pressure chambers 1b and 1c are used. In addition, a hydrostatic bearing having a compact configuration can be provided. The method of adjusting the bearing consumption flow rate is roughly classified into a method of suppressing the flow rate from the pump, which is a fluid supply source, and a method of reviewing the specifications of the bearing portion and the like reaching the differential pressure chamber. In the latter case, if the bearing portion is a porous throttle having a high drawing effect, the specifications of the bearing throttle (clogging amount, etc.), and if the drawing effect is relatively low such as a self-contained drawing, the bearing is used. In some cases, the adjustment is performed by adjusting the shape (width, length) of the land portion and the size of the clearance.
[0016]
Further, when the bearing portion is made of a porous material, a uniform pressure distribution is easily formed, and the loss is smaller than that of other types of hydrostatic bearings at the same flow rate. Further, a throttle having a small flow rate can be easily formed, a clearance can be reduced, high rigidity can be obtained with a small flow rate, and a more compact configuration is provided. In this case, the clearance between the bearing 2 and the guide 2 at the portion between the bearing 1a and the differential pressure chamber 1b may be increased.
[0017]
Further, it is preferable that the outside of the housing is maintained in an atmosphere that is damaged by the leakage of the fluid, because the function and effect of the hydrostatic bearing of the present invention can be further exhibited. The “environment impaired by leakage of the fluid” refers to a vacuum atmosphere in which the degree of vacuum is impaired by the inflow of air when the fluid is air, or a special gas atmosphere in which the gas concentration is reduced. But not limited to them.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 4A is a cross-sectional view of the hydrostatic bearing according to the first embodiment, and FIG. 4B is a cross-sectional view taken along line IVB-IVB of the configuration of FIG. FIG. 5 is a sectional view of a hydrostatic bearing according to a comparative example corresponding to the first embodiment. FIG. 5A is a sectional view taken along line VB-VB of FIG. FIG. The hydrostatic bearing shown in FIG. 4 is basically similar to the configuration shown in FIG. The same applies to FIG.
[0019]
In FIG. 4A, a process chamber P in a chamber C is maintained in a vacuum atmosphere. In the chamber C, a slider (housing) 11 is provided so as to be slidable on a guide 12. A cylindrical recess 11a is formed in the center of the lower surface of the housing 11 in FIG. A porous material 13 made of a porous material such as graphite or ceramic and forming a bearing portion is attached to the concave portion 11a having a supply chamber by a bolt B. The porous material 13 may be adhered to the concave portion 11a or may be press-fitted. A ring-shaped groove 13a (when the fixing of the porous material 13 is not performed by bolts, a cylindrical groove may be used) is formed on the upper surface of the porous material 13 in FIG. That is, an annular space is formed between the concave portion 11a and the porous material 13. This annular space is connected to the positive pressure pump P1 outside the chamber C via the piping section 14. In addition, the ratio d1 / d0 of the outer diameter d0 of the porous material 13 to the bore diameter d1 of the counterbore for the bolt B is regulated to 0.2 to 0.6, so that the dynamic rigidity is excellent and the bearing load capacity is sacrificed very much. Without this, the bearing consumption flow rate is suppressed.
[0020]
On the lower surface of the housing 11 in FIG. 4 (a), a groove-shaped first differential pressure chamber 11b is formed continuously so as to surround the recess 11a, and further to surround the first differential pressure chamber 11b. A second differential pressure chamber 11c is formed continuously (see FIG. 4B). The first differential pressure chamber 11b is connected to a first negative pressure pump P2 outside the chamber C via a pipe portion 15, and the second differential pressure chamber 11c is connected to a portion outside the chamber C via a pipe portion 16. It is connected to the second negative pressure pump P3. The hydrostatic bearing of FIG. 5 according to the comparative example is different from the hydrostatic bearing of FIG. 1 in that an open-to-atmosphere groove extending continuously between the recess 11a and the first differential pressure chamber 1b. 11d, and is only open to the outside of the chamber C via the pipe section 17.
[0021]
4 and 5, air is pumped into the concave portion 11a from the positive pressure pump P1, spreads over the entire circumference along the groove 13a, passes through the inside of the porous material 13, goes to the lower surface, or is uniform there. In order to create a static pressure, the slider 11 can be separated from the guide 12 and supported in a non-contact state. The slider 11 can be moved, for example, in the direction of the arrow by a driving device (not shown).
[0022]
When the unit of the slider 11 as described above is used for a linear guide mechanism, for example, as shown in FIG. 8A described later, a housing as a slider is inserted through a predetermined clearance so as to surround a prismatic guide member. It is conceivable to provide the slider 11 on each of the four surfaces facing the guide member of the housing. Further, by adjusting the balance between the repulsive force of the hydrostatic bearing in one unit and the suction force in the differential pressure chamber, it is possible to provide a slider constituted by only two surfaces that do not face each other. In this case, if the present invention is applied, it is possible not only to reduce the size and weight, but also to obtain a necessary degree of vacuum with a small capacity pump.
[0023]
Here, when the outer diameter of the air opening groove 11d is φ60 mm, and the radial width of the partition wall between the air opening groove 11d and the differential pressure chamber 11b is 5 mm, the configuration of FIG. Then, when the leak amount Q of the air to be released to the atmosphere is calculated (accordingly, b = 60πmm and L = 5 mm), the gap between the partition 12 and the guide 12 between the air release groove 11d and the differential pressure chamber 11b is 10 μm. In this case, approximately Q = 0.90 [Pa · m ³ / S]. Therefore, in the configuration of FIG. 4, the consumption flow rate of the bearing is reduced to 0.90 [Pa · m] by adjusting the throttle by the porous material 13 or adjusting the supply amount from the positive pressure pump P1 to the recess 11a. ³ / S] or less, the air opening groove 11d shown in FIG. 5 can be omitted, and the sealing performance is further improved. The partition wall 11e constitutes a bearing land portion, and is flush with the bearing surface and other partition walls, but is not necessarily so, and may be recessed (increase the clearance between the guide). Good.
[0024]
For example, in the case of a linear guide mechanism, if the slider is small, the weight of the slider is reduced and if the size is reduced, the length of the guide is also reduced. In particular, in the case of the type in which the guide guide is fixed at both ends and the slider moves between the guide guides, the support span of the guide guide is also shortened, so that the slider itself is reduced in weight and the guide accuracy (vertical straightness, Pitting resistance) can be improved.
[0025]
In addition, a porous restrictor, a surface restrictor, an orifice restrictor, a self-contained restrictor, etc. are provided on the discharge surface of the hydrostatic bearing. The resistance is 2-3, the leakage resistance of the orifice diaphragm is 5-15, and the leakage resistance of the self-contained diaphragm is 10-30. Therefore, in order to obtain high sealing performance, a porous diaphragm is most preferable. Other apertures can be used as long as The porous material is not limited to graphite and ceramics, but may be other materials such as sintered metal. The effect of a change in the shape of the bearing land and a change in the clearance between the bearing land and the guide on a change in the consumption flow rate of the bearing is due to the small leakage resistance (large throttling effect). In the case of a system having a small leakage resistance and a large leakage resistance (small aperture effect), the value is large. Therefore, the change in the bearing consumption flow rate due to the review of the shape of the hydrostatic bearing is substantially determined only by adjusting the throttle of the bearing portion substantially in the case of, for example, a porous throttle, and, for example, in the case of a self-generated throttle, the shape of the land portion is changed. The effect of adjusting the clearance between the land and the guide is large.
[0026]
FIG. 6 is a sectional view similar to FIG. 4B of the hydrostatic bearing according to the second embodiment. 6, two porous members 23 having the same configuration as the porous member 13 of FIG. 4 are fixed to the housing 21 by bolts B, respectively. Air is supplied from an external positive pressure pump (not shown) via a pipe (not shown) disposed behind each porous material 23. When such a unit is applied to, for example, a linear guide device, the same unit as described in the first embodiment can be used.
[0027]
A land portion 21e flush with the surface (bearing surface) of the porous material 23 and the partition walls 21f and 21g is formed so as to include the porous material 23, and a track groove-shaped differential pressure is formed outside the land portion 21e. A chamber 21b is formed. The land portion 21e is not necessarily flush with the bearing surface and the partition walls 21f and 21g, and may be recessed. A track groove-shaped differential pressure chamber 21c is formed outside the differential pressure chamber 21b with a partition wall 21f interposed therebetween. Further, the outside of the differential pressure chamber 21c across the partition 21g is a process chamber P maintained in a vacuum atmosphere. The differential pressure chamber 21b is connected to an external negative pressure pump (not shown) via a piping section 25 arranged at intervals, and the differential pressure chamber 21c is connected to a piping section 26 arranged at intervals. Via an external negative pressure pump (not shown).
[0028]
In the present embodiment, assuming that the differential pressure chamber 21b is an open-to-atmosphere groove and the peripheral length of the partition wall 21f is 288 mm and the width is 5 mm, the amount of air leaking from the open-to-atmosphere groove is calculated by the formula (1 ′). By calculation, when the gap with the slider (not shown) is 10 μm, about 1.38 [Pa · m] ³ / S], and when the gap is 5 μm, about 0.17 [Pa · m] ³ / S]. Therefore, the throttle of the porous material may be adjusted or the gas supply amount from the positive pressure pump may be adjusted so that the bearing consumption flow rate does not exceed the calculated value of the flow rate according to the size of the gap. As in the case of the first embodiment, when a self-contained throttle type is used as the hydrostatic bearing, for example, the shape of the bearing land 21e and the shape of the bearing land 21e and the guide are adjusted as a method of adjusting the consumption flow rate of the bearing. There is also a change in the size of the gap with the guide.
[0029]
FIG. 7 is a bottom view of the hydrostatic bearing according to the third embodiment (a view as seen from the same direction as FIG. 4B). In FIG. 7, four porous members 33 having the same configuration as the porous member 13 in FIG. 4 are fixed to the housing 31 by bolts B at equal intervals. Air is supplied from an external positive pressure pump (not shown) through a pipe (not shown) disposed behind each porous material 33. When such a unit is applied to, for example, a linear guide device, the same unit as described in the first embodiment can be used.
[0030]
A land portion 31e flush with the surface (bearing surface) of the porous material 33 and the partition walls 31f and 31g is formed so as to include the porous material 33, and a track groove-shaped differential pressure is formed outside the land portion 31e outside the land portion 31e. A chamber 31b is formed. The land portion 31e is not necessarily flush with the bearing surface and the partition walls 31f and 31g, and may be recessed. A track groove-shaped differential pressure chamber 31c is formed outside the differential pressure chamber 31b with a partition wall 31f interposed therebetween. Further, the outside of the differential pressure chamber 31c with the partition wall 31g interposed therebetween is a process chamber P maintained in a vacuum atmosphere. The differential pressure chamber 31b is connected to an external negative pressure pump (not shown) via a piping section 35 disposed at intervals, and the differential pressure chamber 31c is connected to a piping section 36 disposed at intervals. Via an external negative pressure pump (not shown).
[0031]
In the present embodiment, assuming that the differential pressure chamber 31b is an open-to-atmosphere groove, and the peripheral length of the partition wall 31f is 488 mm and the width is 5 mm, the amount of air leaking from the open-to-atmosphere groove is calculated by the equation (1 ′). By calculation, when the gap with the slider (not shown) is 10 μm, about 2.34 [Pa · m] ³ / S], and when the gap is 5 μm, approximately 0.29 [Pa · m] ³ / S]. Therefore, the throttle of the porous material may be adjusted or the gas supply amount from the positive pressure pump may be adjusted so that the consumption flow rate of the bearing does not exceed the calculated value of the flow rate according to the size of the gap. Similarly to the case of the first embodiment, when a self-contained throttle type or the like is adopted as the hydrostatic bearing, for example, the shape of the bearing land 31e and the shape of the bearing land 31e and the guide are adjusted as a method of adjusting the consumption flow rate of the bearing. There is also a change in the size of the gap with the guide.
[0032]
FIG. 8 is a diagram showing a hydrostatic bearing according to a fourth embodiment, and FIG. 8A is a perspective view of such a hydrostatic bearing (a piping portion is not shown), and FIG. FIG. 8A is a view of the configuration of FIG. 8A cut along the line VIIIB-VIIIB and viewed in the direction of the arrow, and FIG. 8C is a view of the configuration of FIG. FIG. 4 is a view showing a portion facing the guide 42 when viewed in the direction of the arrow. The hydrostatic bearing shown in FIG. 8 is configured by disposing the hydrostatic bearings of FIGS. 8B and 8C on each surface of the slider 41 so as to face each surface of the prismatic guide 42. is there. Since the configuration of each hydrostatic bearing is basically common, only one hydrostatic bearing will be described, and description of the other hydrostatic bearings will be omitted.
[0033]
In FIG. 8, the process chamber P outside the housing (slider) 41 is maintained in a vacuum atmosphere. The housing 41 is installed so as to sandwich the guide 42 vertically and horizontally. In FIG. 8B, two concave portions 41a are formed on the lower surface of the housing 41. A porous material 43 made of a porous material such as graphite or ceramic and constituting a bearing portion is attached to the concave portion 41a with a bolt B. The porous material 43 may be bonded or press-fitted into the concave portion 41a. A ring-shaped groove 43a is formed on the upper surface of the porous material 43 in FIG. That is, an annular space is formed between the concave portion 41a and the porous material 43. This annular space is connected to a positive pressure pump P1 outside the chamber (not shown) via a piping section 44.
[0034]
On the lower surface of the housing 41 in FIG. 8B, a track groove-shaped first differential pressure chamber 41b is formed so as to surround the porous material 43, and further to surround the first differential pressure chamber 41b so as to surround the track. A groove-shaped second differential pressure chamber 41c is formed (see FIG. 8C). The first differential pressure chamber 41b is connected to a first negative pressure pump P2 outside the chamber (not shown) via a piping section 45, and the second differential pressure chamber 41c is connected to a first negative pressure pump P2 via a piping section 46 (not shown). Is connected to a second negative pressure pump P3 outside the chamber.
[0035]
In the configuration of FIG. 8, air is pumped into the concave portion 41a by the positive pressure pump P1 and spreads over the entire circumference along the groove 43a, and passes through the inside of the porous material 43 to the lower surface, or has a uniform static pressure. To form That is, the slider 41 can be separated from the guide 42 by the upper, lower, left and right hydrostatic bearings, and can be supported in a non-contact state. The slider 41 is movable in the direction of the arrow by a driving device (not shown).
[0036]
As compared with the embodiment of FIG. 6, since the area of the outermost partition wall 41g is larger, if other conditions such as the size of the clearance are the same, the sealing effect can be further enhanced.
[0037]
FIG. 9 is a view similar to FIG. 8A showing a modification of the fourth embodiment. In this modified example, the configuration and arrangement of the two porous members 41 and the positions of the pipe portions 45 and 46 are the same as those of the fourth embodiment, but the shapes of the differential pressure chambers 51b and 51c are different. Differently, it has a substantially rectangular shape when viewed in the direction of FIG. Thereby, the area of the bearing land portion 51e can be increased, that is, the bearing load capacity can be increased.
[0038]
FIG. 10 is a sectional view of a hydrostatic bearing according to the fifth embodiment. In FIG. 10, the process chamber P outside the housing 61 constituting the slider is maintained in a vacuum atmosphere. A round guide 62 is arranged in a circular opening 61h of the housing 61. A large diameter portion 61a is formed at the center of the opening 61h of the housing 61. A cylindrical porous material 63 formed of a porous material such as graphite or ceramic is adhered to the large diameter portion 61a. Note that press-fitting or fixing with bolts may be used. On the outer peripheral surface of the porous material 63, a thin cylindrical groove 63a is formed. That is, an annular space is formed between the large diameter portion 61a and the porous material 63. This annular space is connected to a positive pressure pump P1 outside the chamber (not shown) via a piping section 64.
[0039]
In the circular opening 61h of the housing 61, a circumferential groove-shaped differential pressure chamber 61b is formed outside the partition wall 61e with the partition wall 61e interposed therebetween. A circumferential groove-shaped differential pressure chamber 61c is formed outside the differential pressure chamber 61b with a partition wall 61f interposed therebetween. Further, the outside of the differential pressure chamber 61c across the partition wall 61g is a process chamber P maintained in a vacuum atmosphere. The differential pressure chamber 61b is connected to an external negative pressure pump P2 via a piping section 65, and the differential pressure chamber 61c is connected to an external negative pressure pump P3 via a disposed piping section 66.
[0040]
In the configuration of FIG. 10, air is pumped into the large-diameter portion 61a from the positive pressure pump P1 and spreads over the entire circumference along the groove 63a, passes through the inside of the porous material 63, and goes to the inner peripheral surface, Creates a uniform static pressure. That is, the outer peripheral surface of the guide 62 can be separated from the inner peripheral surface of the porous material 63 and supported in a non-contact state. The housing 61 is movable in the axial direction by a driving device (not shown).
[0041]
In the present embodiment, assuming that the differential pressure chambers 61b on both sides are open-to-atmosphere grooves, and the outer diameter of the guide 62 is 40 mm and the width of the partition wall 61f is 5 mm, the open-to-atmosphere grooves are obtained by the formula (1 ′). When the amount of air leaking from the slider is calculated, when the gap with the slider (not shown) is 10 μm, 1.21 [Pa · m ³ / S] and 0.15 [Pa · m] when the gap is 5 μm. ³ / S]. Therefore, the amount of air supplied to the large diameter portion 61a may be appropriately adjusted so as not to exceed the flow rate calculated according to the size of the gap. Alternatively, the aperture of the porous material 63 may be adjusted. Furthermore, for example, when a self-contained throttle is used as the hydrostatic bearing, as a method of adjusting the consumption flow rate of the bearing, a change in the shape of the bearing land portion 61e or the size of the gap between the bearing land portion 61e and the guide is also exemplified. Can be In the fifth embodiment, a case is described in which a combination of a round shaft guide and a cylindrical slider is provided, and a circumferential groove-shaped differential pressure chamber is provided on the inner peripheral surface of the slider. ), It is also possible to adopt a configuration in which the differential pressure chamber is provided in a circumferential groove shape.
[0042]
As described above, the present invention has been described with reference to the embodiments. However, the present invention should not be construed as being limited to the above embodiments, and it is needless to say that modifications and improvements can be made as appropriate. For example, in the above-described embodiment, the sealing performance is reduced by reducing the amount of air supplied to the hydrostatic bearing with respect to the amount of air leaking outward when the differential pressure chamber is assumed to be open to the atmosphere. Although an attempt was made to improve the performance, the amount of air leaking out was slightly larger than the amount of air supplied to the hydrostatic bearing, although this would balance with the performance of the negative pressure pump and the required sealing performance. May be good. Further, the present invention can be used even when used at atmospheric pressure. For example, in the case of using the balance in which the repulsive force of the hydrostatic bearing and the suction force of the differential pressure chamber are balanced, it is possible to reduce the size and weight of the apparatus by omitting the air opening groove. .
[0043]
【The invention's effect】
The hydrostatic bearing according to the present invention is a hydrostatic bearing for supporting a second member (for example, a slider) so as to be displaceable with respect to a first member (for example, a guide), wherein the first member and the second member are connected to each other. And a bearing portion (for example, a concave portion or a large-diameter portion) connected to an external fluid supply source (for example, a positive pressure pump), and disposed adjacent to and surrounding the bearing portion. A differential pressure chamber connected to a pressure source (for example, a negative pressure pump); fluid leaking from the bearing portion is collected in the differential pressure chamber; Since the space between the pressure member and the pressure chamber is not communicated with the outside, the second member can be supported without impairing the external environment of the first member. Since there is no need to provide an open-to-atmosphere groove for communication, the configuration is simplified and the It can be miniaturized and low-cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a modeled configuration of the present invention.
FIG. 2 is a cross-sectional view showing a model of a configuration of a conventional technique.
FIG. 3 is a diagram illustrating a model of a passage of a fluid leaking from an open-to-atmosphere groove.
FIG. 4 is a diagram showing a hydrostatic bearing according to the first embodiment.
FIG. 5 is a diagram showing a hydrostatic bearing according to a comparative example corresponding to the first embodiment.
FIG. 6 is a sectional view of a hydrostatic bearing according to a second embodiment.
FIG. 7 is a sectional view of a hydrostatic bearing according to a third embodiment.
FIG. 8 is a diagram showing a hydrostatic bearing according to a fourth embodiment.
FIG. 9 is a diagram showing a hydrostatic bearing according to a modification of the fourth embodiment.
FIG. 10 is a diagram showing a hydrostatic bearing according to a fifth embodiment.
[Explanation of symbols]
1, 11, 21, 31, 41, 51, 61 slider
2, 12, 22, 32, 42, 52, 62 Guide (housing)
3,13,23,33,43,53,63 Porous material

Claims (5)

In a hydrostatic bearing that displaceably supports a second member relative to a first member in a non-contact manner,
A bearing portion provided on one of the first member and the second member and connected to an external fluid supply source;
A differential pressure chamber disposed adjacent to and surrounding the bearing portion, and further connected to an external negative pressure source;
The fluid leaked from the bearing portion is collected in the differential pressure chamber, and the bearing portion and the differential pressure chamber are not communicated with the outside. Hydrostatic bearing. The hydrostatic bearing according to claim 1, wherein the fluid is a gas. The static pressure bearing according to claim 1, wherein the static pressure bearing is provided in a closed space, and the fluid supply source and the negative pressure source are provided outside the closed space. The bearing consumption flow rate of the bearing portion is set such that the fluid is a viscous flow, and leakage from the differential pressure chamber to another differential pressure chamber located outside when the differential pressure chamber is assumed to be open to the atmosphere. The hydrostatic bearing according to any one of claims 1 to 3, wherein the static flow bearing is regulated to a flow rate equal to or less than the flow rate. The hydrostatic bearing according to any one of claims 1 to 4, wherein the bearing portion is formed of a porous material.

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