Abstract:
A fluid bearing that dampens without requiring a special braking device, and further, without affecting the fluid bearing surfaces. A slide member that is guided by a guide member so as to move linearly is supported by fluid bearing surfaces. The guide member protrudes from the bottom of an opening provided in the bottom of the slide member and its side wall surfaces function as braking surfaces that press against the braking surfaces of the slide member. When fluid of an adequate pressure is supplied to the fluid bearing surfaces, the slide member deforms, a gap appears between the braking surfaces, and further, the slide member, which is supported by the fluid bearing surfaces, enters a state of non-contact with the guide member and the movement of the slide member is damped, thus making it possible to obtain a fluid bearing that can dampen movement without requiring a special braking device, and further, without scratching the bearing surfaces.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a fluid bearing.  
         [0003]     2. Description of the Related Art  
         [0004]     Normally, in order to stop the operation of rotary bodies or linear motion bodies such as rotary shafts, rotary tables and linear motion slides, a braking device is used. The braking device stops the movement of the rotary body or linear motion body by pressing a brake shoe or a brake band and a brake pad against a member such as a brake drum or a brake disk that rotates or moves linearly as a single unit together with the rotary body or the linear motion body.  
         [0005]     At the same time, as a bearing for the rotating body or the linear motion body, a fluid bearing that contactlessly supports moving parts using a fluid under pressure is well known. In the braking of such a rotary body or a linear motion body using this fluid bearing as well, a braking device is commonly used.  
         [0006]     In addition, a method is known in which, in a mechanism that supports a slide member with a hydrostatic bearing and slides a slide member, when the rigidity of the bearing is weakened and pressurized fluid is supplied to the bearing, the bearing elastically deforms and a gap is formed between the bearing and a ram to smoothen the slide of the slide mechanism and the supply of pressurized fluid is stopped, causing the deformation of the bearing to disappear and the bearing to tighten on the slide member so as to constrict the movement of the slide member and providing braking, and a slide device is known in which a guided member is provided on a table that moves while being guided by a guide base, such that, when a hydrostatic bearing is formed between the bottom of the table and the top of the guide pedestal as well as between the guided member and the guide base and pressurized fluid is supplied to the hydrostatic bearing, a gap is formed between the bottom of the table and the top of the guide base so as to raise the table, and further, when the guided member elastically deforms to form a gap between the guided member and the guide base so as to permit the table to move while being guided in the direction of movement of the table and the supply of pressurized fluid is stopped, the weight of the table causes the bottom of the table to contact the top of the guide base, and moreover, the deformation of the guided member disappears and the guided member and the guide base contact each other so as to dampen the movement of the table (for example, JP 06-094031A).  
         [0007]     However, providing a braking device for the rotary shaft and linear motion slide moving members as is commonly used conventionally has proportionate disadvantages in terms of cost and in terms of efficient use of space.  
         [0008]     With respect to the foregoing point, the slide device described in JP 06-094031A utilizes hydrostatic bearing pressurized fluid in a structure in which a guide surface of the hydrostatic bearing is compressed, and does not provide a special braking device. However, since the guide surfaces of the fluid bearing forms the braking surfaces, in the course of countless compressing and braking actions the guide surfaces becomes scratched, uneven and warped, causing a risk of the fluid bearing surface biting or of operational accuracy deteriorating.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides a fluid bearing capable of braking without requiring a special braking device and without affecting fluid bearing surfaces.  
         [0010]     According to one aspect of the present invention, the fluid bearing comprises: a slide member having a bearing surface; and a guide member having a bearing surface for supporting and guiding the slide member linearly movably with fluid supplied between the bearing surfaces of the guide member and the slide member, wherein at least one of the slide member and the guide member has a deformable portion that deforms with pressure of the fluid supplied between the bearing surfaces, and both of the slide member and the guide member have braking surfaces provided separate from the bearing surfaces to come in contact with each other when pressure of the fluid supplied between at least part of the bearing surfaces is decreased below a predetermined value such that deformation of the deformable portion is reduced. When fluid of sufficient pressure is supplied between the bearing surfaces of the slide member and the guide member, a gap appears between the braking surfaces, and the slide member becomes movably supported in non-contact with the guide member. When the pressure of the fluid is decreased, the braking surfaces press against each other to brake the movement of the slide member.  
         [0011]     According to another aspect of the present invention, the fluid bearing comprises: a rotary member having a bearing surface; and a stationary member having a bearing surface for rotatably supporting the rotary member with fluid supplied between the bearing surfaces of the stationary member and the rotary member, wherein at least one of the rotary member and the stationary member has a deformable portion that deforms with pressure of the fluid supplied between the bearing surfaces, and both of the rotary member and the stationary member have braking surfaces provided separate from the bearing surfaces to come in contact with each other when pressure of the fluid supplied between at least par of the bearing surfaces is decreased below a predetermined value such that deformation of the deformable portion is reduced. When fluid of sufficient pressure is supplied between the bearing surfaces of the rotary member and the stationary member, a gap appears between the braking surfaces, and the rotary member becomes rotatably supported in non-contact with the stationary member. When the pressure of the fluid is decreased, the braking surfaces press against each other to brake the rotation of the rotary member.  
         [0012]     As a result, the present invention achieves a fluid bearing that operates simply by adjusting the pressure of the fluid that is supplied under pressure to the fluid bearing, without the need for a special braking device, and that is capable of braking simply and at low cost.  
         [0013]     In addition, since the braking surface is provided separately from the bearing surface of the fluid bearing, there is no risk of the fluid bearing surface biting or of operational accuracy deteriorating. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a diagram showing a schematic perspective view of a first embodiment of the present invention, in which the fluid bearing of the present invention is adapted to a linear motion slide;  
         [0015]      FIGS. 2   a  and  2   b  are diagrams illustrating the operation of the fluid bearing of the present invention using central sectional views of the first embodiment;  
         [0016]      FIG. 3  is a diagram showing a schematic perspective view of a second embodiment of the present invention, in which the fluid bearing of the present invention is adapted to the bearing of a rotary member; and  
         [0017]      FIGS. 4   a  and  4   b  are diagrams illustrating the operation of the fluid bearing of the present invention using central sectional views cut along the central axis of rotation of a rotary member of the second embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 1  is a diagram showing a schematic perspective view of a first embodiment of the present invention, in which the fluid bearing of the present invention is adapted to a linear motion slide.  FIGS. 2   a  and  2   b  are diagrams showing sectional views along a central line A-A shown in  FIG. 1 , in which  FIG. 2   a  shows a state when pressurized fluid is not supplied and  FIG. 2   b  shows a state when fluid of an adequate pressure is supplied.  
         [0019]     A slide member  10  is formed so as to enclose a guide member  11  except for a portion of the bottom edge thereof, with opposed surfaces of the slide member  10  and the guide member  11  forming fluid bearing surfaces  15  (indicated by hatching in  FIGS. 2   a  and  2   b ), such that the slide member  10  is supported by the guide member  11 .  
         [0020]     A portion of the bottom of the guide member  11  protrudes from an opening in the bottom edge of the slide member  10 , so that lateral wall surfaces of the protruding portion of the guide member  11  and corresponding inner lateral wall surfaces of the opening in the slide member  10  are disposed opposite each other, so as to form braking surfaces  12 ,  13 , In other words, the lateral wall surfaces of the protruding guide member  11  form guide member side braking surfaces  12  and the inner lateral wall surfaces of the opening in the slide member  10  form slide member side braking surfaces  13 . In addition, so that these two braking surfaces  12 ,  13  are alternatively pressed against and separated from each other by the pressure of a fluid supplied to the fluid bearing surfaces  15 , in this embodiment a deformable portion  14  is provided in the slide member  10 .  
         [0021]     As shown in  FIG. 2   a , in a state in which pressurized fluid is not supplied to the fluid bearing surfaces  15 , the braking surface  12  of the guide member  11  and the braking surface (the inner lateral wall surfaces)  13  of the slide member  10  contact each other. However, when fluid of a pressure adequate to cause the fluid bearing surfaces  15  to act as a fluid bearing is supplied, as shown in  FIG. 2   b  the deformable portion  14  of the slide member  10  deforms under the pressure of the fluid bearing, putting both braking surfaces  12 ,  13  in a state of non-contact. In addition, by decreasing the pressure of the fluid supplied to all or a portion of the fluid bearing surfaces  15 , as shown in  FIG. 2   a  the amount of deformation of the slide member  10  decreases, the slide member side braking surface  13  contacts the guide member side braking surface  12  and the slide member  10  is damped. The fluid bearing surfaces  15  are of such dimensions as to not contact each other at this time. In addition, the deformable portion  14  is formed on the slide member  10  so as to deform so that the braking surfaces (inner lateral wall surfaces)  13  of the slide member  10  separate from the guide member side braking surfaces  12  as shown in  FIG. 2   b  when fluid of an adequate pressure is supplied to the fluid bearing surfaces  15 .  
         [0022]     In this first embodiment of the present invention, the dimensions and materials of each portion of the slide member  10  are designed so that the deformable portion  14  deforms under pressure from the inside toward the outside when fluid of an adequate pressure is supplied to the fluid bearing surfaces  15 . As a result, when fluid of an adequate pressure is supplied to the fluid bearing surfaces  15 , the braking surfaces  13  of the inner lateral wall surfaces separate from the braking surfaces  12  of the slide member  10 . It should be noted that, in  FIG. 2   b , for descriptive convenience the extent of the deformation of the slide member  10  is exaggerated. The actual extent of the gap that appears between both braking surfaces  12  and  13  due to the deformation of the slide member  10  is on the order of several μm to several tens of μm.  
         [0023]     When fluid of an adequate pressure is supplied to the fluid bearing surfaces  15 , as shown in  FIG. 2   b  the slide member  10  is supported in a contactless state by the guide member  11  and the slide member  10  is permitted to move in a straight line along the guide member  11 . By contrast, when stopping the slide member  10  moving linearly, decreasing the pressure of the fluid supplied to the fluid bearing surfaces  15  below a certain value causes the deformation of the deformable portion  14  of the slide member  10  either to decrease or to disappear, returning the deformable portion  14  of the slide member  10  to its original position and, as shown in  FIG. 2   a , contacting both braking surfaces  12 ,  13  against each other, braking the linear motion of the slide member  10  and stopping the slide member  10 . At this time, the braking surfaces (inner lateral wall surfaces)  13  of the slide member  10  contact the braking surfaces  12 , but contact with the fluid bearing surfaces  15  at the sides of the slide member  10  is prevented by both braking surfaces  12 ,  13  contacting each other, so that there is virtually no contact. In addition, contact between the top of the guide member  11  and the fluid bearing surface  15  and the bottom of the interior of the slide member  10  is also similarly prevented by both braking surfaces  12 ,  13  contacting each other, so that such contact is slight. As a result, the fluid bearing surfaces  15  are not scratched, made uneven or warped, and consequently, there is no risk of the fluid bearing surface biting or of operational accuracy deteriorating. By greatly decreasing the pressure of the pressurized fluid supplied to the lateral (the sides of the guide member  11 ) and bottom surface portions of the fluid bearing surfaces  15  and decreasing the pressure of the pressurized fluid at the top surface portion of the fluid bearing surfaces  15  (the top of the guide member  11 ) to a level such as to support the weight of the slide member  10 , a braking action can be effected by the pressed contact between the two braking surfaces  12 ,  13  without any contact between the fluid bearing surfaces  15  of the top of the guide member  11  and the inner bottom side of the slide member  10 .  
         [0024]     It should be noted that, although in the first embodiment described above the guide member  11  is fixed and the slide member  10  moves, alternatively, the slide member  10  may be fixed and treated as the stationary member while the guide member  11  is made into the moving member. In other words, in  FIG. 1 , reference numeral  10  may be used to indicate the fixed member and reference numeral  11  the moving member, such that the fixed member  10  guides the moving member  11 .  
         [0025]     In addition, although in the embodiment described above the deformable portion that is deformed by the pressurized fluid is provide on the slide member, alternatively the deformable portion may be provided on either the slide member or the guide member or on both the slide member and the guide member, such that, when fluid of an adequate pressure is supplied to the fluid bearing surfaces, this deformable portion deforms so as to permit a gap to be formed between the two braking surfaces.  
         [0026]      FIG. 3  is a diagram showing a schematic perspective view of a second embodiment, in which the fluid bearing of the present invention is adapted to the bearing of a rotary member.  FIGS. 4   a  and  4   b  are diagrams illustrating the operation of the fluid bearing of the present invention using central sectional views cut along the central axis of rotation of the rotary member, in which  FIG. 4   a  represents a state when pressurized fluid is not supplied to the fluid bearing surfaces of the rotary member and  FIG. 4   b  shows a state in which fluid of a pressure adequate to cause the fluid bearing surfaces to function as a fluid bearing is supplied to the fluid bearing surfaces  15  of the rotary member.  
         [0027]     A disc part  26  with a portion of expanded diameter is provided on a rotary shaft that comprises a rotary member  20 . A stationary member  21  provided with surfaces disposed opposite the top and bottom as well as the periphery of the disc part  26  is provided, such that the top and bottom as well as the periphery of the disc part  26  comprise fluid bearing surfaces (portions indicated by hatching in  FIGS. 4   a  and  4   b ) and the rotary member  20  is supported by the stationary member  21  through this fluid bearing. A braking surface  22  is provided on a portion of the periphery of the rotary member  20  (in the embodiments shown in the drawings, the lower peripheral surface in  FIGS. 3, 4   a  and  4   b ), with the inner peripheral surface of the stationary member  21  disposed opposite this braking surface  22  and comprising stationary member side braking surface  23 . In the state shown in  FIG. 4   a , in which pressurized fluid is not supplied to the fluid bearing surfaces  25 , the two braking surfaces  22 ,  23  press against and contact each other. The dimensions of the fluid bearing surfaces  25  are designed so that no contact between them arises in this state.  
         [0028]     In addition, the dimensions of each part of the stationary member  21  are designed so that a deformable portion  24  deforms and a gap appears between the two braking surfaces  22 ,  23  as shown in  FIG. 4   b  when fluid of an adequate pressure is supplied to the fluid bearing surfaces  25 . In other words, when fluid of an adequate pressure is supplied to the fluid bearing surfaces  25 , that pressurized fluid causes an upward force to be exerted on the stationary member  21  at the position of the top edge surface of the disc part  26  of the rotary member  20  in  FIG. 4   b , a downward force to be exerted on the stationary member  21  at the bottom edge of the disc part  26  of the rotary member  20 , and further, a force expanding in the radial direction at the periphery of the disc part  26 . As a result, the deformable portion  24  of the stationary member  21  deforms, causing top and bottom openings in the stationary member  21  to expand and separating the stationary member side braking surfaces  23  from the rotary member side braking surfaces  22  and putting the two braking surfaces in a contactless state. In addition, at the fluid bearing surfaces  25  as well, a gap appears between the stationary member  21  and the rotary member  20 , enabling the rotary member  20  to be rotatably supported by the stationary member  21  in a contactless state. It should be noted that, in  FIG. 4   b , for descriptive convenience the extent of the deformation of the stationary member  21  is exaggerated, and the actual extent of the gap between the braking surfaces  22  and  23  is on the order of several μm.  
         [0029]     Thus, as described above, when fluid of an adequate pressure is supplied to the fluid bearing surfaces  25 , as shown in  FIG. 4   b , the rotary member  20  is rotatably supported in a contactless state by the stationary member  21 . By decreasing the pressure of the fluid supplied to part or all of the fluid bearing surfaces  25 , the extent of the deformation of the stationary member  21  decreases as shown in  FIG. 4   a  and the two braking surfaces  22 ,  23  are pressed together, braking the rotation of the rotary member  20 .  
         [0030]     It should be noted that, in this second embodiment as well, the rotary member  20  and the stationary member  21  may be reversed. In other words, in  FIGS. 3, 4   a  and  4   b , reference numeral  20  may be used to indicate the stationary member and reference numeral  21  the rotary member. In addition, the deformable portion may be provided on either the rotary member or the stationary member, or on both the rotary member and the stationary member.