JP6455177B2 - Hydrostatic bearing device, spindle device for machine tool using hydrostatic bearing device - Google Patents

Description

  The present invention relates to a hydrostatic bearing device and a spindle device for a machine tool using the hydrostatic bearing device.

  2. Description of the Related Art Conventionally, a hydrostatic bearing device that supports a rotating shaft that rotates at high speed, such as a main shaft of a machine tool, by static pressure of a pressurized fluid such as a lubricant (see Patent Document 1). For example, Patent Document 1 discloses a technique of a hydrostatic fluid bearing device including a bearing metal having a hydrostatic portion for rotating and supporting a rotating shaft. The static pressure part has a bearing surface part having a bearing gap with the surface of the rotating shaft and a plurality of pockets recessed adjacent to the circumferential direction of the bearing surface part, and a lubricant or the like is provided in the pocket. This is a technique for supporting the rotating shaft by fluid pressure (static pressure) by supplying fluid.

JP 2001-304260 A

  However, as shown in FIGS. 9 and 10, the lubricant used in the hydrostatic bearing device causes a so-called swirling flow in the pocket due to the rotation of the rotation shaft, and the flow in the rotation direction of the rotation shaft and the pocket A flow in the direction opposite to the rotation of the rotation shaft at the bottom occurs. Along with this, a large velocity gradient is generated in the vicinity of the surface of the rotating shaft in the hydrostatic bearing device, and there is a concern about power loss due to a large fluid shear resistance. Further, the inside of the pocket is a strong turbulent flow with a Reynolds number of 20000 to 30000, and there is a concern about the generation of a large velocity gradient near the surface of the rotating shaft and the power loss due to the large fluid shear resistance. This tendency becomes more remarkable as the rotating shaft rotates at a high speed.

  Therefore, the present invention has been made in view of the above points, and the problem to be solved by the present invention is to suppress an increase in the velocity gradient of the fluid in the pocket of the hydrostatic bearing device and reduce power loss. Is to plan.

  In order to solve the above problems, the hydrostatic bearing device of the present invention takes the following means. First, the hydrostatic bearing device according to the first aspect of the present invention is a hydrostatic bearing device, comprising a bearing metal having a hydrostatic portion for rotating and supporting a rotating shaft, and the hydrostatic portion is configured to rotate the rotating shaft. A bearing gap filled with a lubricant between the surface of the shaft, a bearing surface portion parallel to the surface of the rotary shaft, a plurality of pockets recessed adjacent to the circumferential direction of the bearing surface portion, and the pocket A land portion that protrudes from the bottom of the rotary shaft toward the surface of the rotating shaft and has a groove portion between an opposing surface parallel to the surface of the rotating shaft and an edge of the pocket, and the groove portion is the land portion. Side groove portions disposed on both sides of the rotating shaft, an upstream groove portion located on the upstream side in the rotational direction of the rotating shaft, and a downstream groove portion located on the downstream side, and communicated with the upstream groove portion. A supply path for supplying a lubricant to the static pressure part, and the bearing gap is A first bearing gap between the surface of the shaft and the bearing surface portion, and a second bearing gap between the surface of the rotary shaft and the facing surface, wherein the second bearing gap is the first bearing gap. When the density of the lubricant is ρ, the viscosity coefficient of the lubricant is μ, the peripheral speed of the rotating shaft is U, and the second bearing gap is H, the second bearing is larger than the bearing gap. The Reynolds number Re in the gap is represented by Re = ρUH / μ, and the flow of the lubricant in the second bearing gap in a state where the rotating shaft is rotationally supported is Re <2000.

  According to the first aspect of the present invention, the static pressure portion includes a land portion that protrudes from the bottom of the pocket toward the surface of the rotating shaft and has a groove portion between the facing surface parallel to the surface of the rotating shaft and the edge of the pocket. have. The groove portion includes a side groove portion disposed circumferentially on both sides of the land portion, an upstream groove portion located on the upstream side in the rotation direction of the rotating shaft, and a downstream groove portion located on the downstream side. A supply path for supplying a lubricant to the communicating static pressure part is provided. As a result, the flow of the lubricating liquid becomes a flow in the rotation direction of the rotation shaft on the opposite surface, and the side groove portion flows in a direction opposite to the rotation of the rotation shaft, so that it is difficult to exert an influence on each other. Thereby, it is possible to suppress an increase in the velocity gradient of the fluid in the pocket of the hydrostatic bearing device and to reduce power loss. Further, when the density of the lubricant is ρ, the viscosity coefficient of the lubricant is μ, the peripheral speed of the rotating shaft is U, and the second bearing gap is H, the Reynolds number Re in the second bearing gap is Re = ρUH / μ. It is represented by The flow of the lubricant in the second bearing gap in a state where the rotation shaft is rotationally supported is Re <2000. In other words, a large fluid shear resistance due to the flow of the lubricant in the second bearing gap is less likely to occur, and power loss can be suppressed.

  Next, the hydrostatic bearing device according to the second aspect of the invention is the hydrostatic bearing device according to the first aspect of the invention described above, wherein the lubricating liquid agent has a ratio of water or water in the composition of 90% or more. Or a low viscosity mineral oil.

  According to the second aspect of the present invention, the lubricating liquid is preferably water or an aqueous solution having a ratio of water to the composition of 90% or more, or a low viscosity mineral oil.

  Next, a hydrostatic bearing device according to a third invention is the hydrostatic bearing device according to the first invention or the second invention described above, wherein the rotating shaft is rotatably supported. The lubricating liquid agent in the two bearing gaps is a laminar flow flowing along the rotation direction of the rotating shaft, and a part of the laminar lubricating liquid agent passes through the side groove portion to the upstream groove portion having the supply path. It becomes a flow.

  According to the third aspect of the invention, the lubricant in the second bearing gap is a laminar flow that flows along the rotation direction of the rotating shaft, and a part of the laminar lubricant has a supply path via the side groove. The flow is to the upstream groove. Thereby, the land portion separates the laminar flow in the second bearing gap and the flow in the counter-rotating direction in the side groove portion. Therefore, it becomes difficult to have mutual influence. Therefore, the increase in the velocity gradient of the fluid in the pocket can be suppressed, and the power loss can be further reduced.

  Next, a fourth invention relates to a machine tool spindle device that rotatably supports a machine tool spindle in a machine tool using the hydrostatic fluid bearing device according to any one of the first to third inventions described above. To do. Thus, it is preferable to use the hydrostatic bearing device for the spindle device for machine tools.

  According to the present invention, by taking the measures of the respective inventions described above, an increase in the velocity gradient of the fluid in the pocket of the hydrostatic bearing device can be suppressed and power loss can be reduced.

It is a top view showing the whole grinding machine composition as an example of the spindle device for machine tools using the hydrostatic bearing device concerning an embodiment. It is a right view of the grinding machine shown in FIG. It is an expanded sectional view of the III section of FIG. It is the IV-IV sectional view taken on the line of FIG. It is the perspective view which partially cut off the bearing metal and showed the internal shape. FIG. 4 is an enlarged cross-sectional view taken along the line IV-IV in FIG. 3, illustrating a flow of a lubricant in a pocket. FIG. 6 is a velocity distribution diagram of the flow of the lubricant in the pocket. It is the figure which showed the power consumption of a hydrostatic bearing device. It is a velocity distribution diagram of the flow of the lubricant in the conventional pocket. It is the figure which showed the flow of the lubricating liquid agent in the conventional pocket.

  Hereinafter, a hydrostatic bearing device and a spindle device for a machine tool using the hydrostatic fluid bearing device will be described with reference to the drawings as an embodiment for carrying out the present invention.

  FIG. 1 is a plan view showing an overall configuration of a grinding machine 10 as an example of a spindle device for a machine tool using a hydrostatic bearing device according to an embodiment. FIG. 2 is a right side view of the grinding machine 10. In FIG. 2, the work holding device 150 including the holding table 151 is not shown. Here, in all drawings in which the X axis, the Y axis, and the Z axis are described, the X axis, the Y axis, and the Z axis are orthogonal to each other, the Y axis indicates a vertically upward direction, and the Z axis and the X axis The axis indicates the horizontal direction. The Z-axis direction indicates a direction parallel to the grindstone rotation axis L1 (in other words, the workpiece rotation axis direction), the X-axis direction is a direction orthogonal to the grindstone rotation axis L1, and the grindstone 132 is placed on the workpiece W. The direction of cutting is shown. The grindstone rotation axis L1, the workpiece rotation axis L2, and the truer rotation axis L3 are all parallel to the Z-axis direction.

  The grinding machine 10 shown in FIGS. 1 and 2 grinds the workpiece W by controlling the movement of the grindstone 132 relative to the workpiece W in the X-axis direction and the Z-axis direction. A Z-axis direction slide table 112 that is slidably guided by a pair of Z-axis direction guide rails 111 extending in the Z-axis direction is disposed at a substantially central portion on the base 110 that is formed in a rectangular shape in a planar shape. The Z-axis direction slide table 112 is slid in the Z-axis direction by the rotation operation of the Z-axis direction feed screw 113 using the Z-axis direction drive motor 114 controlled by the control means 180 (NC control device or the like) as a drive source. . Further, the Z-axis direction drive motor 114 detects the rotation angle of the output shaft of the Z-axis drive motor 114 and controls the detection signal in order to confirm the position of the Z-axis direction slide table 112 in the Z-axis direction. Z-axis direction position detecting means 115 such as an encoder for sending to 180 is provided. The control means 180 uses the Z-axis direction drive motor 114 to move the grindstone 132 relative to the truer 177 or the workpiece W in the Z-axis direction, and based on the detection signal from the Z-axis direction position detection means 115. The relative movement amount of the grindstone 132 in the Z-axis direction with respect to the truer 177 or the workpiece W can be detected.

  On the Z-axis direction slide table 112, an X-axis direction slide table 122 that is slidably guided by a pair of X-axis direction guide rails 121 extending in the X-axis direction is disposed. The X-axis direction slide table 122 is slid in the X-axis direction by the rotation operation of the X-axis direction feed screw 123 using the X-axis direction drive motor 124 controlled by the control means 180 as a drive source. The X-axis direction drive motor 124 detects the rotation angle of the output shaft of the X-axis direction drive motor 124 and controls the detection signal in order to confirm the position of the X-axis direction slide table 122 in the X-axis direction. An X-axis direction position detecting means 125 such as an encoder for sending to the means 180 is provided. The control means 180 uses the X-axis direction drive motor 124 to move the grindstone 132 relative to the truer 177 or the workpiece W in the X-axis direction, and based on the detection signal from the X-axis direction position detection means 125. The relative movement amount of the grindstone 132 in the X-axis direction with respect to the truer 177 or the workpiece W can be detected.

  A grindstone drive motor 126 and a grindstone shaft holder 130 are provided on the X-axis direction slide table 122, and a drive pulley 127 is provided on the output shaft of the grindstone drive motor 126. On the other hand, at the other end of the grindstone shaft 131 (the grindstone shaft rotating around the grindstone rotation axis L1 parallel to the Z-axis direction), which is rotatably supported by the grindstone shaft holder 130 and provided with a substantially cylindrical grindstone 132 at one end. Is provided with a driven pulley 128. A belt 129 is stretched between the driving pulley 127 and the driven pulley 128, whereby the torque of the output shaft of the grindstone driving motor 126 is transmitted to the grindstone shaft 131 via the belt 129.

  On the base 110, there are a workpiece holding device 140 and a workpiece holding device 150 that hold the shaft-like workpiece W around the workpiece rotation axis L2 in the Z-axis direction at a set position, and the workpiece parallel to the Z-axis direction. It is arrange | positioned on the rotating shaft L2. The workpiece holding device 140 includes a holding table 141 fixed on the base 110, a holding shaft housing 142 that can reciprocate on the workpiece rotation axis L <b> 2 with respect to the holding table 141, and a workpiece rotation axis within the holding shaft housing 142. A holding shaft member 143 supported rotatably around L2 is provided, and a center member 144 that supports the center of one end surface of the workpiece W is provided at the tip of the holding shaft member 143. The holding shaft member 143 is rotationally controlled to an arbitrary angle at an arbitrary angular velocity by using a holding shaft motor (not shown) that is controlled by the control unit 180 as a drive source. In addition, the work holding device 150 is configured to include a holding base 151, a holding shaft housing 152, a holding shaft member 153, and a center member 154, similarly to the work holding device 140. Further, the holding shaft housing 142 is provided with a truing device 160 including a truer 177 that is rotatably supported around the truer rotation axis L3. As shown in FIG. 2, the grindstone rotation axis L1, the workpiece rotation axis L2, and the truer rotation axis L3 are all on a virtual plane VM that is a plane parallel to the X-axis direction and the Z-axis direction.

  In this way, the grinding machine 10 performs grinding of the workpiece W by moving the grindstone 132 relative to the workpiece W or the truer 177 in the Z-axis direction and the X-axis direction, or the outer shape of the grindstone 132 by the truer 177. Reshape as appropriate.

  FIG. 3 is an enlarged cross-sectional view of the grindstone shaft holder 130 (part III in FIG. 1). 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a perspective view showing the internal shape by partially cutting the bearing metal. FIG. 6 is an enlarged cross-sectional view taken along the line IV-IV in FIG. 3 and shows the flow of the lubricant in the pocket. As shown in FIG. 3, the grindstone shaft holder 130 includes a grindstone shaft housing 12 and a bearing metal 14 fixed in the grindstone shaft housing 12. The grindstone shaft 131 (rotary shaft) is rotatably supported by the bearing metal 14. As shown in FIG. 4, the bearing metal 14 supplies fluid such as a lubricant R through the flow path 16 from the pump P (see FIG. 4) or the like into the bearing metal 14 to cause the grinding wheel shaft 131 to be fluid pressure ( It has a static pressure part 18 for rotational support by static pressure). As shown in FIG. 5, the bearing metal 14 is formed in a steel cylinder shape. As shown in FIG. 6, the static pressure portion 18 includes a bearing gap 20, a bearing surface portion 22, a plurality of pockets 24, and a land portion 30 on the inner peripheral surface of the bearing metal 14. The lubricating liquid R is preferably water or an aqueous solution having a ratio of water of 90% or more to the composition or a low-viscosity mineral oil.

  The bearing surface portion 22 is a surface parallel to the surface of the grindstone shaft 131 as shown in FIGS. The pocket 24 is a part for storing the lubricant R supplied from the pump P or the like via the flow path 16 (supply path). The pockets 24 are recessed in the bearing surface portion 22 of the bearing metal 14, and a plurality of pockets 24 are adjacent to each other in the circumferential direction. In the present embodiment, the lubricant R is supplied to each of the four pockets 24 via the flow path 16. The number of pockets 24 is not limited to four. In addition, the fluid that is used for static pressure support of the grindstone shaft 131 in the pocket 24 and the axial pocket (not shown) is recovered via a drain (not shown) and cooled by an oil cooler or the like. It is returned to the tank T (see FIG. 4).

  The land portion 30 has a groove portion 40 between the facing surface 32 that protrudes from the bottom portion 26 of the pocket 24 toward the surface of the grindstone shaft 131 and is parallel to the surface of the grindstone shaft 131 and the edge portion 28 of the pocket 24. The groove portion 40 includes a side groove portion 42 disposed in the circumferential direction on both sides of the land portion 30, an upstream groove portion 44 located on the upstream side in the rotation direction of the rotation shaft, and a downstream groove portion 46 located on the downstream side. . Further, the flow path 16 (supply path) that communicates with the upstream groove portion 44 and supplies the lubricant R to the static pressure portion 18 is provided.

  The bearing gap 20 is a space filled with the lubricant R between the surface of the grindstone shaft 131. The bearing gap 20 has a first bearing gap C between the surface of the grindstone shaft 131 and the bearing surface portion 22, and a second bearing gap H between the surface of the grindstone shaft 131 and the facing surface 32. The second bearing gap H is set so as to be larger than the first bearing gap C. The bearing metal 14 cuts the inner peripheral surface to form a plurality of pockets 24 and land portions 30 in the pockets 24. Thereby, the bearing metal 14 is adjacent to the surface of the grindstone shaft 131 with the bearing gap 20 filled with the lubricant R, the bearing surface portion 22 parallel to the surface of the grindstone shaft 131, and the circumferential direction of the bearing surface portion 22. A plurality of pockets 24 that are recessed, and a groove portion between the edge 28 of the pocket 24 and a facing surface 32 that protrudes from the bottom 26 of the pocket 24 toward the surface of the grindstone shaft 131 and is parallel to the surface of the grindstone shaft 131. The static pressure part 18 having the land part 30 having 40.

  The grindstone shaft 131 is supported by fluid pressure (static pressure) by supplying a fluid such as the lubricant R to the pocket 24. Here, when the density ρ of the lubricant R, the viscosity coefficient μ of the lubricant R, the peripheral speed U of the grindstone shaft 131, and the second bearing gap H, the Reynolds number Re in the second bearing gap H is Re = ρUH / It is expressed in μ. Here, the setting of the peripheral speed U of the grindstone shaft 131 is exemplified by setting as appropriate based on the design standard specification speed of the grindstone shaft 131, the rotation speed and the average speed that are assumed to be frequently used, and the like. The interval of the second bearing gap H is set so that the flow of the lubricant R in a state where the grindstone shaft 131 is rotationally supported is set to Re <2000. The lubricant R in the second bearing gap H in a state where the grindstone shaft 131 is rotationally supported becomes a laminar flow flowing along the rotation direction of the grindstone shaft 131, and a part of the laminar lubricant R is an edge of the pocket 24. The flow flows to the upstream groove 44 having the flow path 16 via the downstream groove 46 and the side groove 42. Therefore, the lubricant R flowing through the side groove portion 42 flows in the counter-rotating direction of the grindstone shaft 131.

  Here, as shown in FIGS. 9 and 10, the lubricant R in the pocket 224 having no conventional land portion 30 causes a so-called whirling flow in the pocket 224 due to the rotation of the grindstone shaft 231, and the grindstone shaft 231. A flow in the rotation direction and a flow in the direction opposite to the rotation of the grindstone shaft 231 at the bottom 226 of the pocket 224 are generated. Accordingly, in the hydrostatic bearing device, a large velocity gradient is generated in the vicinity of the surface of the grindstone shaft 231, and there is a concern about power loss due to a large fluid shear resistance. Under the condition of strong turbulent flow with the Reynolds number 20000 to 30000 in the bearing, the flow gradient of the lubricant R when the pocket depth K and the peripheral speed S of the grindstone shaft 231 are ∂S. / Represented as ∂K. Here, in the case of the viscosity coefficient μ of the lubricant R, the shearing force τ1 applied to the grindstone shaft 231 is expressed as τ1 = μ × (∂S / ∂K). The power loss P1 that the lubricant R in the pocket 224 exerts on the grindstone shaft 231 is expressed as P1 = S × τ1 × A where the opening area A of the pocket 224 is assumed. Assuming that the peripheral speed S of the grinding wheel shaft 231 and the opening area A of the pocket 224 are fixed values, it is the shearing force τ1 that affects the power loss P1. Further, if the temperature change of the lubricant R is constant, the viscosity coefficient μ is constant. Therefore, the speed gradient ∂S / ∂K at τ1 is a factor affecting the power loss P1.

  On the other hand, as shown in FIG. 6, when the flow of the lubricant R in the bearing is in a laminar flow state, the velocity gradient can be approximated to U / H. The shearing force τ2 related to the grindstone shaft 131 is expressed as τ2 = μ × (U / H). The power loss P2 that the lubricant R in the pocket 24 exerts on the grindstone shaft 131 is expressed as P2 = U × τ2 × A where the opening area A of the pocket 24 is assumed. Assuming that the peripheral speed U of the grindstone shaft 131 and the opening area A of the pocket 24 are fixed values, it is the shearing force τ2 that affects the power loss P2. Further, if the temperature change of the lubricant R is constant, the viscosity coefficient μ is constant. Therefore, τ2 is a factor in which H affects the power loss P2 in the U / H of the velocity gradient.

  Therefore, as shown in FIGS. 6 and 7, the static pressure unit 18 of the present embodiment has a laminar flow in the vicinity of the surface of the grindstone shaft 131, and the flow in the rotational direction of the grindstone shaft 131 and the side groove 42 of the pocket 24. In order to separate the flow in the direction opposite to the rotation of the grindstone shaft 131 in order not to affect each other, the land portion 30 was employed. The second bearing gap H between the facing surface 32 of the land portion 30 and the surface of the grindstone shaft 131 is set to the maximum within a range where laminar flow can be maintained. With the configuration of the land portion 30, the bearing gap 20 of the static pressure portion 18 is between the first bearing gap C between the surface of the grindstone shaft 131 and the bearing surface portion 22, and between the surface of the grindstone shaft 131 and the land portion 30. Second bearing gap H. Here, the second bearing gap H is set to be larger than the first bearing gap C. As described above, the lubricant R in the second bearing gap H in a state where the grindstone shaft 131 is rotatably supported becomes a laminar flow that flows along the rotation direction of the grindstone shaft 131. Further, the lubricant R in the side groove portion 42 of the pocket 24 returns to the flow path 16 as a flow in the counter-rotating direction of the grindstone shaft 131 while suppressing the influence of the second bearing gap H on the laminar flow. As a result, as shown in FIG. 8, the result of reducing the power consumption was obtained regardless of whether the lubricant R was water, an aqueous solution, or a low-viscosity mineral oil.

  As described above, according to the hydrostatic bearing device of the embodiment, the hydrostatic portion 18 includes the opposing surface 32 that protrudes from the bottom of the pocket 24 toward the surface of the grindstone shaft 131 and the pocket parallel to the surface of the grindstone shaft 131. A land portion 30 having a groove portion 40 is provided between 24 edge portions 28. The groove portion 40 includes a side groove portion 42 disposed circumferentially on both sides of the land portion 30, an upstream groove portion 44 positioned on the upstream side in the rotational direction of the grindstone shaft 131, and a downstream groove portion 46 positioned on the downstream side. And a flow path 16 (supply path) that communicates with the upstream groove portion 44 and supplies the lubricant R to the static pressure portion 18. Thereby, the flow of the lubricant R is a flow in the rotation direction of the grindstone shaft 131 on the opposing surface 32 and the side groove portion 42 is a flow in a direction opposite to the rotation of the grindstone shaft 131, so that it is difficult to influence each other. . Thereby, it is possible to suppress an increase in the velocity gradient of the fluid in the pocket 24 of the hydrostatic bearing device and to reduce power loss. Further, when the density of the lubricant R is ρ, the viscosity coefficient of the lubricant R is μ, the peripheral speed of the grindstone shaft 131 is U, and the second bearing gap H is Reynolds number Re in the second bearing gap H is Re = It is represented by ρUH / μ. The flow of the lubricant R in the second bearing gap H in a state where the grindstone shaft 131 is rotationally supported is Re <2000. That is, a large fluid shear resistance due to the flow of the lubricant R in the second bearing gap H is less likely to occur, and power loss can be suppressed.

  In addition, the lubricant R is preferably water or an aqueous solution having a ratio of water to the composition of 90% or more, or a low viscosity mineral oil.

  The lubricant R in the second bearing gap H is a laminar flow that flows along the rotation direction of the grindstone shaft 131, and a part of the laminar lubricant R is supplied through the upstream groove 44 and the side groove 42. It becomes the flow to the upstream groove part 44 which has. Thereby, the land portion 30 separates the laminar flow in the second bearing gap H and the flow in the counter-rotating direction in the side groove portion 42. Therefore, it becomes difficult to have mutual influence. Therefore, an increase in the fluid velocity gradient in the pocket 24 can be suppressed, and the power loss can be further reduced.

  In addition, it is preferable to use a hydrostatic bearing device having the above-described configuration as a machine tool spindle device that rotatably supports a machine tool spindle in a machine tool.

  Although the embodiments of the present invention have been described above, the hydrostatic bearing device of the present invention, the spindle device for machine tools using the hydrostatic bearing device, and the manufacturing method of the hydrostatic bearing device are limited to the embodiments. It can be implemented in various other forms.

DESCRIPTION OF SYMBOLS 10 Grinding machine 12 Grinding wheel shaft housing 14 Bearing metal 16 Flow path (supply path)
18 Hydrostatic part 20 Bearing gap 22 Bearing surface part 24 Pocket 26 Pocket bottom part 28 Pocket edge part 30 Land part 32 Opposing surface 40 Groove part 42 Side groove part 44 Upstream groove part 46 Downstream groove part 110 Base 111 Z-axis direction guide rail 112 Z axis Direction slide table 113 Z-axis direction feed screw 114 Z-axis direction drive motor 115 Z-axis direction position detecting means 121 X-axis direction guide rail 122 X-axis direction slide table 123 X-axis direction feed screw 124 X-axis direction drive motor 125 X-axis direction Position detection means 126 Grinding wheel drive motor 127 Drive pulley 128 Driven pulley 129 Belt 130 Grinding wheel shaft holder 131 Grinding wheel shaft (rotating shaft)
132 Grinding wheel 140 Work holding device 141 Holding stand 142 Holding shaft housing 143 Holding shaft member 144 Center member 150 Work holding device 151 Holding stand 152 Holding shaft housing 153 Holding shaft member 154 Center member 160 Truing device 177 Truer 180 Control means C First bearing Clearance H Second bearing clearance L1 Grinding wheel rotation axis L2 Work rotation axis L3 Truer rotation axis P Pump R Lubricant U

Claims (5)

A hydrostatic bearing device,
A bearing metal having a static pressure part for rotating and supporting the rotating shaft,
The static pressure portion is recessedly formed adjacent to the bearing clearance filled with a lubricant between the surface of the rotating shaft, a bearing surface portion parallel to the surface of the rotating shaft, and the circumferential direction of the bearing surface portion. A plurality of pockets, and a land portion that protrudes from the bottom of the pocket toward the surface of the rotating shaft and has a groove portion between an opposing surface parallel to the surface of the rotating shaft and an edge of the pocket. ,
The groove portion includes a side groove portion disposed circumferentially on both sides of the land portion, an upstream groove portion located on the upstream side in the rotation direction of the rotating shaft, and a downstream groove portion located on the downstream side,
A supply path that communicates with the upstream groove and supplies the lubricant to the static pressure section;
The bearing gap has a first bearing gap between the surface of the rotating shaft and the bearing surface portion, and a second bearing gap between the surface of the rotating shaft and the facing surface,
The second bearing gap is larger than the first bearing gap,
The density of the lubricant is ρ,
The viscosity coefficient of the lubricant is μ,
The peripheral speed of the rotating shaft is U,
When the second bearing gap is H,
The Reynolds number Re in the second bearing gap is represented by Re = ρUH / μ,
The hydrostatic bearing device in which the flow of the lubricant in the second bearing gap in a state where the rotating shaft is rotatably supported is Re <2000.   The hydrostatic bearing device according to claim 1,
  The hydrostatic bearing device, wherein the second bearing gap is less than the length of the facing surface from the bottom of the pocket in the land portion. The hydrostatic bearing device according to claim 1 or 2 , wherein
The lubricating fluid is a hydrostatic bearing device, wherein the lubricant is water or an aqueous solution having a ratio of water to 90% or more, or low-viscosity mineral oil. The hydrostatic bearing device according to any one of claims 1 to 3 ,
The lubricant in the second bearing gap in a state where the rotating shaft is rotatably supported is a laminar flow that flows along the rotation direction of the rotating shaft;
A hydrostatic bearing device in which a part of the laminar flow lubricant flows through the side groove to the upstream groove having the supply path. A spindle device for a machine tool that rotatably supports a spindle for a machine tool in a machine tool using the hydrostatic bearing device according to any one of claims 1 to 4 .

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