JP2020020347A - Rotary shaft member supporting device and grinder - Google Patents

Abstract

To provide a rotary shaft member supporting device having a static pressure fluid bearing which can suppress the occurrence of cavitation by applying preload, in a simple and inexpensive construction.SOLUTION: A rotary shaft member supporting device 70 includes a bearing 90 having a static pressure pocket 94 recessed in a bearing surface 93 of a bearing member 92 opposed to the outer peripheral face of a rotary shaft member 72, the bearing 90 having a peripheral groove 96 which is extendingly provided in a dynamic pressure generation land 95 along the peripheral direction of the bearing member 92, and is communicated at one end 96a side in the peripheral direction with a first static pressure pocket part 94a and closed at the other end 96b side in the peripheral direction, and of which the depth in the radial direction of the bearing surface 93 is greater than the size of a bearing gap and smaller than the depth in the radial direction of the first static pressure pocket part 94a.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a rotating shaft member supporting device and a grinding machine provided with the rotating shaft member supporting device.

  BACKGROUND ART Conventionally, for example, a fluid bearing disclosed in Patent Literature 1 below is known. This conventional fluid bearing includes a plurality of static pressure pockets formed on a bearing surface formed on an inner peripheral surface of the inner sleeve, and a land portion that generates dynamic pressure in a bearing surface area other than the static pressure pocket. ing.

  Conventionally, for example, a hydrodynamic bearing device disclosed in Patent Document 2 below is also known. This conventional hydrodynamic bearing device includes a U-shaped static pressure pocket and a dynamic pressure generating land at a portion surrounded by a U-shape, a rectangular static pressure pocket and a static pressure pocket formed on a bearing surface of a bearing member. And a land portion that generates

  In addition, conventionally, for example, a hydrostatic bearing device disclosed in Patent Document 3 below is also known. This conventional hydrostatic bearing device includes a U-shaped bearing pocket and a land portion surrounded by the bearing pocket, and the land portion is provided with a concave portion.

  Further, conventionally, for example, a combined static / dynamic pressure bearing disclosed in Patent Document 4 below is also known. This conventional bearing includes a concave helical bone groove provided on an arch-shaped cylindrical surface portion and a land.

  Furthermore, conventionally, for example, a hydrodynamic bearing device disclosed in Patent Document 5 below is also known. This conventional hydrodynamic bearing device includes a support portion that generates a static pressure, a land portion that is uniformly protruded from the support portion and generates a dynamic pressure, and a predetermined step formed between the support portion and the land portion. And steps.

JP 2003-172356 A JP 2001-304260 A Japanese Utility Model Publication No. 5-22843 JP-T-2002-515963 JP-A-54-90434

  Generally, in a rotating shaft member supporting device having a hydrostatic bearing, lubricating oil is supplied to a static pressure pocket provided in the hydrostatic bearing, and the rotating shaft member is statically supported by the supplied lubricating oil. Further, in the rotating shaft member supporting device having a hydrostatic bearing, when the rotating shaft member is eccentric, a wedge effect in a wedge-shaped gap formed by a difference between the outer diameter of the rotating shaft member and the inner diameter of the hydrostatic bearing is provided. The rotating shaft member is supported by dynamic pressure by generating dynamic pressure.

  By the way, in the conventional devices disclosed in Patent Documents 1 to 3, when the rotating shaft member is eccentric, the dynamic pressure in the dynamic pressure generating land that generates the dynamic pressure is small, and as a result, the hydrostatic bearing There is a possibility that the rotation of the rotating shaft member may become unstable due to cavitation generated inside.

  On the other hand, in the conventional devices disclosed in Patent Document 4 and Patent Document 5, the herringbone groove or the inclination such that the gap between the outer peripheral surface of the rotating shaft member and the outer peripheral surface of the rotating shaft member is reduced along the circumferential direction of the bearing surface. A step or the like is provided to increase the preload of the bearing. Thus, the occurrence of cavitation inside the hydrostatic bearing is suppressed, and the eccentricity (eccentric angle) of the rotating shaft member is suppressed.

  However, the herringbone groove, the slope, the step, and the like have a machining depth of about several μm to about several tens μm, which is equal to or less than the bearing gap between the rotating shaft member and the bearing surface. Therefore, in order to realize such a working depth, it is necessary to perform, for example, etching or ultra-precision working along the circumferential direction of the bearing surface, and the manufacturing cost becomes extremely high.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a rotating shaft member support having a hydrostatic bearing capable of suppressing cavitation by applying a preload with a simple configuration and at low cost. It is an object of the present invention to provide an apparatus and a grinding machine provided with the rotary shaft member supporting apparatus.

  The rotating shaft member supporting device according to the present invention includes a bearing housing, a bearing member fitted to the bearing housing, and a hydrostatic pocket formed in a concave shape on a bearing surface of the bearing member facing the outer peripheral surface of the rotating shaft member. A hydrodynamic bearing having a dynamic pressure generating land surrounded by a static pressure pocket and formed on a bearing surface, and a supply port provided in the static pressure pocket to regulate lubricating oil and supply the lubricating oil to the static pressure pocket. A rotating shaft member supporting device for rotatably supporting a rotating shaft member by a hydrostatic bearing, wherein the static pressure pocket is extended along an axial direction of the bearing member and supplied through a supply port. And a first static pressure pocket portion for supplying lubricating oil to at least a bearing gap formed between the rotating shaft member and the dynamic pressure generating land with the rotation of the rotating shaft member. Is composed of The pressure fluid bearing extends to the dynamic pressure generating land along the circumferential direction of the bearing member, and one end in the circumferential direction communicates with the first static pressure pocket portion, and the other end in the circumferential direction becomes a closed end, There is a circumferential groove in which the depth of the surface in the radial direction is larger than the size of the bearing gap and smaller than the radial depth of the first hydrostatic pocket portion.

  Further, the grinding machine according to the present invention includes a rotating shaft member rotatably supported by the rotating shaft member supporting device and holding a grinding wheel, a tank storing lubricating oil, a tank and a hydrostatic bearing. A flow passage for connecting and flowing the lubricating oil, a lubricating oil supply device disposed in the flow passage and supplying the lubricating oil stored in the tank to the hydrostatic pocket of the hydrostatic bearing, and discharging from the hydrostatic bearing And a return path for returning the lubricating oil to the tank.

  According to these, the hydrostatic bearing of the rotating shaft member supporting device has a circumferential groove larger than the size of the bearing gap and shallower than the depth of the first static pressure pocket portion with respect to the dynamic pressure generating land. Can be. Accordingly, the circumferential groove does not need to be formed by ultraprecision machining, and can be formed with a simple configuration and at a low cost. This reduces the manufacturing cost of the hydrostatic bearing, and thus the grinding machine provided with the rotating shaft member support device. Can be reduced.

  Also, by providing a circumferential groove in which one end communicates with the first static pressure pocket portion and the other end is a closed end with respect to the dynamic pressure generating land, the circumferential groove is present along with the rotation of the rotating shaft member. As a result, a turbulent flow occurs in the lubricating oil, and as a result, a preload can be effectively applied in a so-called wedge-shaped clearance generated due to the bearing clearance and the eccentricity of the rotating shaft member. Therefore, even when eccentricity occurs in the rotating shaft member, it is possible to suppress the occurrence of cavitation inside the hydrostatic bearing, and the hydrostatic bearing is provided between the rotating shaft member and the hydrostatic bearing. The rotation shaft member can be stably rotated by suppressing the occurrence of image sticking or the like.

It is a top view of a grinding machine of one embodiment of a rotating shaft member support device by the present invention. FIG. 2 is a cross-sectional view of the grindstone head taken along the line II-II shown in FIG. 1. It is a front view of the grindstone main body shown in FIG. FIG. 2 is a cross-sectional view illustrating a configuration of the hydrostatic bearing illustrated in FIG. 1. FIG. 4 is a partial cross-sectional view for explaining a static pressure generated in a static pressure pocket and a preload generated in a circumferential groove. It is a partial sectional view for explaining pressure generated between a rotating shaft member and a bearing surface (dynamic pressure generating land) by a static pressure pocket and a circumferential groove. FIG. 7 is a partial cross-sectional view for explaining pressure generated between a rotating shaft member and a bearing surface (dynamic pressure generating land) in the case of a comparative product having no circumferential groove. FIG. 13 is a partial cross-sectional view for describing a hydrostatic bearing in which the depth of a circumferential groove changes according to a first modification of the embodiment of the present invention. FIG. 14 is a view for explaining a hydrostatic bearing in which the width of a circumferential groove changes according to a second modification of the embodiment of the present invention. FIG. 13 is a view for describing a hydrostatic bearing having an axial groove according to a third modification of the embodiment of the present invention. FIG. 11 is a partial cross-sectional view for explaining a static pressure generated in a static pressure pocket and a preload generated in a circumferential groove and an axial groove in the hydrostatic bearing shown in FIG. 10. FIG. 16 is a diagram for describing a case where a supply port is provided in a second static pressure pocket portion according to another modification of the embodiment of the present invention. FIG. 14 is a view for explaining a case where the hydrostatic bearing has a rectangular hydrostatic pocket according to another modification of the embodiment of the present invention. FIG. 14 is a diagram for describing a case where a first static pressure pocket portion of a static pressure pocket has a curved shape according to another modification of the embodiment of the present invention. FIG. 16 is a diagram for describing a case where a circumferential groove is meandering according to another modification of the embodiment of the present invention. It is a figure for explaining a case where a hydrostatic fluid bearing has a hydrostatic pocket which omitted a 2nd hydrostatic pocket part concerning other modification of an embodiment of the present invention.

(1. Outline of grinding machine)
An embodiment of a rotating shaft member supporting device having a hydrostatic bearing of the present invention will be described with reference to the drawings. In the present embodiment, the rotating shaft member supporting device is used for a grinding machine 1 shown in FIG. The grinder 1 is a grindstone traverse type cylindrical grinder capable of grinding an axial workpiece W. The grinding machine 1 mainly includes a bed 10, a headstock 20, a tailstock 30, a grinding wheel support device 40, a sizing device 50, and a control device 60. In FIG. 1, the Z-axis direction is a traverse direction, the X-axis direction is a horizontal direction perpendicular to the traverse direction, and the Y-axis direction is a vertical direction perpendicular to the Z-axis direction and the X-axis direction. .

  The bed 10 is formed in a flat rectangular shape, and is fixed on an installation surface (floor). On the upper surface of the bed 10, a pair of Z-axis guide rails 11a and 11b that allow a grinding wheel base traverse base 41, which will be described later, constituting the grinding wheel support device 40 to slide are extended in parallel with each other along the Z-axis direction. Has been fixed. A Z-axis ball screw 11c for driving the wheel head traverse base 41 in the Z-axis direction is arranged between the pair of Z-axis guide rails 11a and 11b. A Z-axis motor 11d that rotationally drives the Z-axis ball screw 11c is fixed to the upper surface of the bed 10.

  The headstock 20 includes a headstock body 21, a spindle 22, a spindle motor 23, and a spindle center 24. The headstock main body 21 rotatably supports the inserted spindle 22. The headstock main body 21 is fixed to the upper surface of the bed 10 such that the axial direction of the spindle 22 faces the Z-axis direction and is parallel to the pair of Z-axis guide rails 11a and 11b.

  A spindle motor 23 is provided at one end of the spindle 22 (the left side in FIG. 1). As a result, the spindle 22 is driven to rotate around the Z-axis with respect to the headstock main body 21 by the spindle motor 23. The spindle motor 23 is provided with an encoder for detecting the rotation angle of the spindle motor 23. A spindle center 24 that supports one end in the axial direction of the shaft-shaped workpiece W is provided at the other end of the spindle 22 (right side in FIG. 1).

  The tailstock 30 includes a tailstock body 31 and a tailstock center 32. The tailstock main body 31 rotatably supports the inserted tailstock center 32. The tailstock main body 31 is fixed to the upper surface of the bed 10 so that the axial direction of the tailstock center 32 is oriented in the Z-axis direction and the rotation axis of the tailstock center 32 is coaxial with the rotation axis of the main shaft 22. Have been. That is, the tailstock center 32 supports both ends in the axial direction of the workpiece W together with the spindle center 24, and is arranged so that the workpiece W can rotate around the Z axis. The tailstock center 32 is configured so that the amount of protrusion from the end surface of the tailstock main body 31 can be changed according to the length of the workpiece W.

(2. Configuration of grinding wheel support device 40)
The grindstone support device 40 includes a grindstone traverse base 41, a grindstone table 42 serving as a rotating shaft member support device 70 described in detail below, and a disk-shaped grindstone wheel 43 as a tool. The grindstone traverse base 41 is formed in a rectangular flat plate shape, and is slidably provided on a pair of Z-axis guide rails 11 a and 11 b provided on the upper surface of the bed 10.

  The grindstone traverse base 41 is connected to a nut member (not shown) of the Z-axis ball screw 11c, and moves along a pair of Z-axis guide rails 11a and 11b by driving a Z-axis motor 11d. Note that the Z-axis motor 11d is provided with an encoder that detects the rotation angle of the Z-axis motor 11d.

  A pair of X-axis guide rails 41a and 41b, which enable the grinding wheel base 42 to slide, are fixedly extended along the X-axis direction on the upper surface of the grinding wheel traverse base 41. . An X-axis ball screw 41c for driving the wheel head 42 in the X-axis direction is disposed between the pair of X-axis guide rails 41a and 41b fixed to the upper surface of the wheel head traverse base 41. An X-axis motor 41d that rotationally drives the ball screw 41c is provided. Note that the X-axis motor 41d is provided with an encoder that detects the rotation angle of the X-axis motor 41d.

  The grindstone table 42 is provided so as to be slidable on a pair of X-axis guide rails 41a and 41b provided on the upper surface of the grindstone table traverse base 41. The grindstone table 42 is connected to a nut member (not shown) of the X-axis ball screw 41c, and is movable along a pair of X-axis guide rails 41a and 41b by driving an X-axis motor 41d. Thus, the wheel head 42 is configured to be relatively movable in the X-axis direction and the Z-axis direction (traverse feed direction) with respect to the bed 10, the headstock 20, and the tailstock 30. The details of the grindstone table 42 (rotary shaft member support device 70) will be described later.

  The sizing device 50 is a device for measuring the outer diameter of the workpiece W at a grinding portion. The sizing device 50 outputs a measurement signal indicating the measured outer diameter to the control device 60.

  The control device 60 is a device that controls the driving of each motor including the Z-axis motor 11d and the X-axis motor 41d. The control device 60 drives each motor to rotate the workpiece W and the grinding wheel 43 around the Z axis, and changes the relative position of the grinding wheel 43 to the workpiece W in the Z axis direction and the X axis direction. To grind the outer peripheral surface of the workpiece W.

(3. Details of the rotating shaft member support device 70 (grindstone 42))
As shown in FIG. 2, the rotating shaft member supporting device 70 as the grindstone head 42 includes a grindstone head body 71, a rotating shaft member 72, a bearing 73 as a hydrostatic bearing, a tank 74, a flow passage 75, , A pump 76 as a lubricating oil supply device, a pressure regulating valve 77, and a recirculation path 78. The grindstone main body 71 rotatably supports the rotating shaft member 72 with a bearing 73. As shown in FIGS. 2 and 3, legs 71 a and 71 b formed at the lower end of the wheel head main body 71 so as to extend in the X-axis direction and guided along a pair of X-axis guide rails 41 a and 41 b. (Only the leg 71b is shown in FIG. 2).

  The rotating shaft member 72 holds the grinding wheel 43 and is driven to rotate. The rotating shaft member 72 is supported on the upper surface of the grindstone main body 71 so as to be rotatable around the Z axis. A disk-shaped grinding wheel 43 is coaxially attached to one end of the rotating shaft member 72. A grinding wheel rotating motor 80 for rotating the rotating shaft member 72 together with the grinding wheel 43 is fixed to the upper surface of the grinding wheel base body 71 via a belt pulley mechanism 79 (see FIG. 1).

  The bearing 73 is a hydrostatic bearing, and rotatably supports the rotating shaft member 72 at a position separated along the Z-axis direction of the rotating shaft member 72 as shown in FIG. The lubricating oil stored in a tank 74 is supplied to the bearing 73 with a regulated pressure in order to statically support the rotating shaft member 72 (see FIG. 2). The configuration of the bearing 73 (90) will be described later in detail.

  As shown in FIGS. 1 to 3, the tank 74 is disposed above the grindstone main body 71 and stores lubricating oil. Specifically, the tank 74 is formed so as to be depressed downward (downward in FIG. 2) from the upper surface (upper side in FIG. 2) of the grindstone main body 71 and open upward. ing. The tank 74 is formed so as to have a portion located below the bearing 73.

  The flow passage 75 connects the tank 74 and the bearing 73, and is a flow passage through which the lubricating oil pumped from the tank 74 by the pump 76 flows. In this embodiment, as shown in FIG. 2, the flow passage 75 is provided outside the grindstone main body 71, but it is also possible to arrange the flow passage 75 inside the grindstone main body 71.

  The pump 76 is connected to the tank 74 and the flow passage 75, and pumps up the lubricating oil stored in the tank 74 and supplies it to the bearing 73. Specifically, as shown in FIG. 2, the pump 76 is fixed to the grindstone main body 71 with the suction port 76a immersed in the lubricating oil stored in the tank 74. Thus, the pump 76 pumps up the lubricating oil stored in the tank 74 from the suction port 76a, and supplies the lubricating oil thus pumped to the bearing 73 through the flow passage 75.

  Here, the pump 76 is electrically connected to the control device 60, and the operation thereof is controlled by the control device 60. Thereby, the pump 76 controls the flow rate, the liquid pressure, and the like of the lubricating oil flowing through the flow passage 75 by controlling the rotation speed and the like by the control device 60.

  The pressure regulating valve 77 is disposed upstream of the bearing 73 in the flow passage 75 as shown in FIG. With this arrangement, the pressure regulating valve 77 regulates the pressure of the lubricating oil supplied to the bearing 73, which is a hydrostatic bearing, to a predetermined pressure. Note that, for example, a direct-acting pressure reducing valve or the like can be used as the pressure adjusting valve 77, and can be omitted.

  The return passage 78 is a flow passage for returning the lubricating oil discharged from the bearing 73 to the tank 74 as shown in FIG. In the present embodiment, the return path 78 is formed by opening the lower end of the bearing 73 toward the tank 74. As a result, the lubricating oil that has passed through the bearing 73 is discharged to the tank 74 via the return path 78 by its own weight. In addition, the recirculation path 78 may be configured by a pipe separately provided so as to connect the bearing 73 and the tank 74.

(4. Details of bearing 90 (73))
As shown in FIG. 4, a bearing 90 which is a hydrostatic bearing includes a bearing housing 91, a bearing member 92, and a bearing surface 93. A cylindrical bearing member 92 having a bearing surface 93 is fitted and integrated into the inner peripheral surface of the bearing housing 91 by press fitting, shrink fitting or the like on the outer peripheral side of the rotating shaft member 72.

  The bearing 90 has a static pressure pocket 94, a dynamic pressure generating land 95, a circumferential groove 96, and a drain groove 97 provided on the bearing surface 93 of the bearing member 92. Thus, the bearing 90 can support the rotating shaft member 72 by static pressure and also can support dynamic pressure.

  The static pressure pocket 94 is provided in a U-shape so as to have a depth of about several mm from the bearing surface 93 as shown in FIG. Specifically, the static pressure pocket 94 is a first static pressure pocket extending along the axial direction of the bearing member 92 (a direction coinciding with the axial direction of the rotating shaft member 72, for example, the Z-axis direction). A portion 94a and a pair of two second static pressure pocket portions 94b extending along the circumferential direction of the bearing member 92 (a direction coinciding with the circumferential direction of the rotating shaft member 72). A plurality of, for example, about four to six, static pressure pockets 94 are provided along the circumferential direction of the bearing member 92.

  Here, in the description of this specification, the abstract, and the claims, "along the axial direction" includes a direction exactly coincident with the axis, and has a component in a direction orthogonal to the axis. This is a concept including a direction having an intersection with an axis when projected onto an imaginary plane (for example, a direction at 45 degrees or less with respect to the axis). In the description, the abstract, and the claims, "along the circumferential direction" includes a direction exactly coincident with an intersection line between a plane orthogonal to the axis and the circumferential surface, and This is a concept including a direction having a component in a direction perpendicular to the line and having an intersection with the intersection line when projected onto a virtual plane (for example, a direction having 45 degrees or less with respect to the intersection line).

  In the present embodiment, a supply port 94c for supplying lubricating oil is opened in the first static pressure pocket portion 94a. The supply port 94c is provided with a lubricating oil supply passage 91a provided in the bearing housing 91 so as to communicate with the flow passage 75, an annular groove 92a provided on the outer periphery of the bearing member 92 and communicating with the lubricating oil supply passage 91a, and an annular shape. It communicates with the communication hole 92b which communicates with the groove 92a and serves as a throttle.

  The dynamic pressure generating land 95 is formed at a portion of the U-shaped static pressure pocket 94 surrounded by the first static pressure pocket 94a and the pair of second static pressure pockets 94b. The dynamic pressure generating land 95 has substantially the same inner peripheral surface height as the bearing surface 93 of the bearing member 92, and generates dynamic pressure with the rotation of the rotary shaft member 72, as described later.

  As shown in FIG. 4, the circumferential groove 96 is formed in the dynamic pressure generating land 95, more specifically, between a pair of opposing second static pressure pocket portions 94 b constituting the static pressure pocket 94. It extends along. The circumferential groove 96 has a depth of about several hundred μm from the bearing surface 93 (the dynamic pressure generating land 95), that is, the first static pressure pocket portion constituting the static pressure pocket 94 as shown in FIG. It is provided so as to be shallower (smaller) than the depth of the 94a and the second static pressure pocket portion 94b. In the present embodiment, two circumferential grooves 96 are provided, but the number of circumferential grooves 96 may be one or three or more.

  In the circumferential groove 96, one end 96 a communicates with the first static pressure pocket 94 a constituting the static pressure pocket 94, while the other end 96 b includes the other static pressure pocket 94 adjacent in the circumferential direction. It is a closed end so as not to communicate with any of the static pressure pockets 94. Thereby, as described later, the lubricating oil supplied to the circumferential groove 96 via the first static pressure pocket portion 94a of the static pressure pocket 94 with the rotation of the rotating shaft member 72 is blocked by the other end 96b. As a result, turbulence is generated to generate dynamic pressure.

  The drain surface 97 of the bearing member 92 is positioned so as to be adjacent to the second static pressure pocket 94b of the U-shaped static pressure pocket 94, that is, at both ends in the axial direction of the static pressure pocket 94. 93. The drain groove 97 communicates with a discharge hole 92c and a discharge hole 91b provided in the bearing member 92 and the bearing housing 91. The discharge hole 92c and the discharge hole 91b communicate with the return path 78, and the lubricating oil flowing into the drain groove 97 is discharged to the tank 74 and collected.

  Here, the operation of the bearing 90 configured as described above will be described. The lubricating oil pumped by the pump 76 is regulated to a pressure of about several Mpa by passing through the flow passage 75 and the pressure regulating valve 77, and from the annular groove 92 a on the outer periphery of the bearing member 92 through the communicating hole 92 b which acts as a throttle. Finally, it is supplied to the static pressure pocket 94. Then, for example, when the rotating shaft member 72 rotating at 5000 to 6000 rpm is not eccentric with respect to the bearing member 92, the lubricating oil filled in the static pressure pocket 94 is applied to the outer peripheral surface of the rotating shaft member 72 and the dynamic pressure generation. By forcibly supplying a gap (bearing gap) with the bearing surface 93 including the land 95, a lubricating oil film is formed and a static pressure is generated. As a result, the non-eccentric rotating shaft member 72 is supported by static pressure.

  When a bearing gap exists between the dynamic pressure generating land 95 and the rotating shaft member 72, the rotating shaft member 72 is not eccentric. For this reason, the same static pressure as that of the U-shaped static pressure pocket 94 is generated in the dynamic pressure generating land 95 by the lubricating oil flowing from the U-shaped static pressure pocket 94.

  On the other hand, when the grinding wheel 43 contacts the workpiece W to perform the grinding, a processing (grinding) reaction force acts on the rotating shaft member 72, and the center axis of the rotating shaft member 72 is eccentric. Thus, when the center shaft is eccentric, the difference between the outer diameter of the rotating shaft member 72 and the inner diameter of the dynamic pressure generating land 95 (that is, the bearing surface 93) causes the bearing gap to gradually narrow to the eccentric side. A gap is formed. The lubricating oil is swung into the surface of the rotating shaft member 72 rotating and drawn into the wedge-shaped gap, so that a dynamic pressure is generated in the dynamic pressure generating land 95 and the rotating shaft member 72 is supported by the dynamic pressure.

  As shown in FIG. 5, the dynamic pressure generating land 95 is formed along the circumferential direction so as to be shallower than the static pressure pocket 94, and has one end 96a communicating with the static pressure pocket 94 and the other end. A circumferential groove 96 formed so that 96b becomes a closed end is provided. Thereby, the static pressure Pf is applied to the rotating shaft member 72 by the static pressure pocket 94 (more specifically, the second static pressure pocket 94b). Further, when the rotation shaft member 72 rotates, the lubricating oil flows from the static pressure pocket 94 into the one end 96a of the circumferential groove 96 regardless of whether or not the center axis of the rotation shaft member 72 is eccentric, and is a closed end. Turbulence flows toward the other end 96b.

  When the flow of the lubricating oil in the circumferential groove 96 becomes a turbulent flow, as shown in FIG. 5, a turbulent flow stress, so-called Reynolds stress, is generated at the position where the circumferential groove 96 is formed. This Reynolds stress acts on the outer peripheral surface as a preload Pg. That is, when the circumferential groove 96 is provided in the dynamic pressure generating land 95, the rotating pressure shaft member 72 is always subjected to the static pressure Pf and the preload Pg accompanying the Reynolds stress.

  Here, the static pressure and the dynamic pressure support of the rotating shaft member 72 by the bearing 90 will be described with reference to FIG. As shown in FIG. 6, in the bearing 90, the bearing surface formed between the second static pressure pocket portion 94b and the drain groove 97 by the pressure of the lubricating oil supplied to the static pressure pocket 94 as described above. The static pressure Pf generated at 93 acts on the rotating shaft member 72. In the portion corresponding to the second static pressure pocket 94b, the static pressure Pf is maintained as shown in FIG.

  The bearing 90 has two circumferential grooves 96 between the pair of second static pressure pocket portions 94b, that is, on the dynamic pressure generating lands 95. Further, the second static pressure pocket portion 94b and the circumferential groove 96 are provided apart from each other along the axial direction. For this reason, when the rotating shaft member 72 is rotating, the bearing groove 93 between the second static pressure pocket portion 94 b and the circumferential groove 96, that is, the dynamic pressure generating land 95 is provided with the circumferential groove 96. Since the internal lubricating oil flows by turbulent flow, a preload Pg based on Reynolds stress is generated in addition to the static pressure Pf, and acts on the rotating shaft member 72.

  In the dynamic pressure generating land 95 of the bearing 90, more specifically, in the dynamic pressure generating land 95 between the two circumferential grooves 96, a bearing gap is formed when the rotating rotary shaft member 72 is not eccentric. Thus, between the circumferential grooves 96, a supporting pressure Pa slightly lower than the sum of the static pressure Pf and the preload Pg is generated.

  In the dynamic pressure generating land 95, when the rotary shaft member 72 is eccentric, a large dynamic pressure Ph is generated by forming a wedge-shaped gap on the side where the rotary shaft member 72 approaches, and as a result, FIG. As indicated by a dashed line, a supporting pressure Pb which is convex upward is generated. On the other hand, on the side where the rotating shaft member 72 is separated, a gap larger than the bearing gap is generated. As a result, as shown by the broken line in FIG. 5, the support pressure Pc is greatly reduced.

(5. Comparison between Example and Comparative Example)
By the way, in the bearing 90 having the circumferential groove 96, the preload Pg is applied as described above. Therefore, even if the support pressure Pc is greatly reduced due to the eccentricity of the rotary shaft member 72, the support pressure Pc is prevented from becoming negative as shown in FIG. On the other hand, as shown in FIG. 7, in the case of the comparative product having the static pressure pocket 194 without the circumferential groove 96, only the static pressure Pf is applied by the second static pressure pocket 94b, and the circumferential groove is not provided. No preload Pg by 96 is applied. Therefore, when the rotary shaft member 72 is eccentric, as shown by the broken line in FIG. 7, the support pressure Pc becomes negative, and as a result, cavitation occurs inside the bearing 90, that is, in the bearing member 92.

  As described above, when the preload Pg by the circumferential groove 96 is acting on the rotating shaft member 72, the preload Pg is applied to the above-described support pressures Pa, Pb, and Pc, as shown in FIG. Therefore, for example, even when the rotating shaft member 72 oscillates (eccentric) due to the contact of the grinding wheel 43 with the workpiece W during grinding, the support pressure Pc (dynamic pressure) is negative. The occurrence of negative pressure is suppressed, and as a result, the occurrence of cavitation is suppressed.

  As shown in FIG. 6, the support pressures Pa and Pc (dynamic pressure) tend to decrease at a central portion in a direction along the axis of the dynamic pressure generating land 95, and in particular, the rotation shaft member 72 When the eccentricity is set so as to be separated from the dynamic pressure generating land 95, that is, when the wedge-shaped gap becomes large, the amount of decrease becomes large like the support pressure Pc. When the circumferential groove 96 is provided in the dynamic pressure generating land 95 in order to suppress such a reduction amount, the second static pressure pocket portion 94b constituting the static pressure pocket 94 by a predetermined distance set experimentally is used. It is preferable to provide the circumferential groove 96 at a position separated from the groove.

  In other words, it is preferable to provide the circumferential groove 96 near the center of the dynamic pressure generating land 95 so as to approach the center of the dynamic pressure generating land 95. Thereby, the circumferential grooves 96 generate Reynolds stress, so that the supporting pressures Pa and Pc (dynamic pressure), which tend to decrease in the central portion of the dynamic pressure generating land 95, can be suppressed and suppressed. . Therefore, generation of negative pressure in which the support pressures Pa and Pc (dynamic pressure) become negative is suppressed, and generation of cavitation is suppressed.

  As can be understood from the above description, the rotating shaft member supporting device 70 of the above embodiment is opposed to the outer peripheral surface of the bearing housing 91, the bearing member 92 fitted to the bearing housing 91, and the rotating shaft member 72. A static pressure pocket 94 formed in the bearing surface 93 of the bearing member 92 in a concave shape, a dynamic pressure generating land 95 surrounded by the static pressure pocket 94 and formed in the bearing surface 93, and provided in the static pressure pocket 94 and lubricated. A bearing 90 (73) as a hydrostatic fluid bearing having a supply port 94c for regulating oil and supplying it to the static pressure pocket 94, and a rotation for rotatably supporting the rotating shaft member 72 by the bearing 90 (73). In the shaft member supporting device, the static pressure pocket 94 extends in the axial direction of the bearing member 92 to store the lubricating oil supplied through the supply port 94c, and to rotate the rotation shaft member. The bearing 90 includes a first static pressure pocket portion 94a that supplies lubricating oil to at least a bearing gap formed between the rotating shaft member 72 and the dynamic pressure generating land 95 with the rotation of the bearing 90. (73) is extended to the dynamic pressure generating land 95 along the circumferential direction of the bearing member 92, one end 96a side in the circumferential direction communicates with the first static pressure pocket portion 94a, and the other end 96b side in the circumferential direction. It has a circumferential groove 96 which is a closed end and whose radial depth of the bearing surface 93 is larger than the size of the bearing gap and smaller than the radial depth of the first static pressure pocket portion 94a.

  Here, the grinding machine 1 including the rotating shaft member supporting device 70 as the grindstone table 42 is rotatably supported by the rotating shaft member supporting device 70 as the grinding wheel table 42, and includes a rotating shaft member 72 that holds the grinding wheel 43. A tank 74 for storing the lubricating oil, a flow passage 75 for connecting the tank 74 and the bearing 73 (90) to flow the lubricating oil, and a lubricating oil stored in the tank 74 that is provided in the flow passage 75. A pump 76 is provided as a lubricating oil supply device for supplying the static pressure pocket 94 of the bearing 73 (90), and a return path 78 for returning the lubricating oil discharged from the bearing 73 (90) to the tank 74.

  According to these, the bearing 90 (73) of the rotating shaft member supporting device 70 is arranged such that, with respect to the dynamic pressure generating land 95, the circumferential direction is larger than the size of the bearing gap and shallower than the depth of the first static pressure pocket portion 94a. It may have a groove 96. Accordingly, the circumferential groove 96 does not need to be formed by ultra-precision processing, and can be formed with a simple configuration and at a low cost, and the bearing 90 (73) and, consequently, the rotary shaft member support device 70 are used as the grindstone table 42. The manufacturing cost of the provided grinding machine 1 can be reduced.

  Further, by providing a circumferential groove 96 in which one end 96a communicates with the first static pressure pocket portion 94a and the other end 96b is a closed end with respect to the dynamic pressure generating land 95, the rotation shaft member 72 rotates. As a result, a turbulent flow occurs in the lubricating oil existing in the circumferential groove 96, and as a result, a preload Pg due to the Reynolds stress is effectively applied to the so-called wedge-shaped gap generated due to the eccentricity of the bearing gap and the rotating shaft member 72. can do. Therefore, even if the rotary shaft member 72 is eccentric, the occurrence of cavitation inside the bearing 90 (73) can be suppressed, and the bearing 90 (73) can be formed with the rotary shaft member 72 and the bearing 90 (73). ) Can be suppressed and the rotation shaft member 72 can be stably rotated.

  In these cases, the static pressure pocket 94 extends in the circumferential direction, communicates with the first static pressure pocket 94a, and is separated from the circumferential groove 96 along the circumferential direction. 94b. In this case, the static pressure pocket 94 is formed by connecting each end of the first static pressure pocket portion 94a in the axial direction with a pair of second static pressure pocket portions 94b spaced apart from each other in the circumferential direction. U-shaped.

  According to these, the bearing 90 (73) has a static pressure pocket 94 on the bearing surface 93 facing the rotating shaft member 72 and a first static pressure pocket portion 94 a extending along the axial direction along the circumferential direction. And an extended second static pressure pocket 94b. And when two second static pressure pocket parts 94b are paired, the static pressure pocket 94 can be U-shaped.

  As a result, an appropriate amount of static pressure Pf can be applied between the shaft gaps regardless of whether the rotation of the rotation shaft member 72 is stopped or rotated. Therefore, the occurrence of cavitation in the inter-shaft gap can be suppressed, and the bearing 90 (73) can further suppress the occurrence of seizure or the like between the rotating shaft member 72 and the bearing 90 (73). The shaft member 72 can be rotated stably.

  Further, in these cases, a plurality of circumferential grooves 96 are provided for the dynamic pressure generating lands 95. According to this, since a plurality of circumferential grooves 96 that generate turbulence in the lubricating oil with the rotation of the rotary shaft member 72 can be provided, the preload Pg due to the Reynolds stress is more reliably applied to the rotary shaft member 72. be able to. Therefore, even if the rotation shaft member 72 is eccentric, the occurrence of cavitation inside the bearing 90 (73) can be suppressed. Accordingly, the bearing 90 (73) can suppress the occurrence of seizure or the like between the rotating shaft member 72 and the bearing 90 (73), and can rotate the rotating shaft member 72 more stably.

(6. First modification)
In the above embodiment, the depth of the circumferential groove 96 provided in the bearing 90 is assumed to be constant along the circumferential direction. Instead, the depth of the circumferential groove 96 is smaller than the depth of the first static pressure pocket 94a (and the second static pressure pocket 94b), and from the one end 96a side to the other end 96b side. It can also be provided so as to be smaller toward the one end 96a side from the other end 96b side. Specifically, as shown in FIG. 8, the depth of the circumferential groove 96 at the one end 96a is made deeper (larger) or shallower (smaller) than the depth at the other end 96b, that is, in the circumferential direction. It is also possible to provide the groove 96 by changing the depth continuously along the circumferential direction.

  As a result, the depth of the circumferential groove 96 in the direction along the extending direction (circumferential direction) changes, so that turbulence easily occurs in the lubricating oil flowing through the circumferential groove 96, and It is possible to further increase the preload Pg due to the generated Reynolds stress. Therefore, it is possible to suppress the generation of the negative pressure in which the support pressures Pa and Pc (dynamic pressure) become negative, and to further suppress the generation of the cavitation.

(7. Second modification)
In the above embodiment, the width of the circumferential groove 96 provided in the bearing 90 is assumed to be constant along the circumferential direction. Instead, the circumferential groove 96 is formed such that the width of the other end 96b in the direction along the axial direction is larger than the width of the one end 96a in the direction along the axial direction. Can be provided.

  Specifically, as shown in FIG. 9, the width of the circumferential groove 96 on the one end 96a side is made larger or smaller than the width of the other end 96b side, that is, the width of the circumferential groove 96 is reduced in the circumferential direction. May be provided continuously or discontinuously. As a result, in the narrow portion of the circumferential groove 96, the flow of the lubricating oil in the circumferential groove 96 is restricted, and as a result, the stress due to the turbulent flow, that is, the preload Pg due to the Reynolds stress increases, and the supporting pressures Pa and Pc It is possible to suppress the occurrence of negative pressure in which (dynamic pressure) becomes negative, thereby suppressing the occurrence of cavitation.

(8. Third modification)
In the above embodiment, the circumferential groove 96 is provided such that one end 96 a of the circumferential groove 96 directly communicates with the first static pressure pocket 94 a of the static pressure pocket 94. Instead, as shown in FIG. 10, the bearing 90 (73) is adjacent to the first static pressure pocket 94a and communicates with the first static pressure pocket 94a, and the depth of the first static pressure pocket 94a. It has an axial groove 98 having a smaller depth than that of the axial groove 98, and the one end 96a side of the circumferential groove 96 can communicate with the first static pressure pocket 94a via the axial groove.

  When the axial groove 98 is provided in the static pressure pocket 94 in this manner, as shown in FIG. 11, a step stress effect by the axial groove 98 is exerted. As a result, as shown by the solid line in FIG. 11, the preload Pg accompanying the Reynolds stress in the circumferential groove 96 is larger than in the case where the axial groove 98 is not provided as shown by the two-dot chain line in FIG. It is possible to do. Thereby, the generation of negative pressure in which the support pressures Pa and Pc (dynamic pressure) become negative can be suppressed, and the generation of cavitation can be suppressed.

(9. Other modifications)
The implementation of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the purpose of the present invention.

  For example, in the above-described embodiment and each of the modifications, the supply port 94c for supplying the lubricating oil to the static pressure pocket 94 is provided in the first static pressure pocket portion 94a of the static pressure pocket 94. Alternatively, as shown in FIG. 12, a supply port 94c can be provided in the second static pressure pocket portion 94b of the static pressure pocket 94.

  In the above-described embodiment and each of the modifications, the static pressure pocket 94 provided on the bearing surface 93 of the bearing member 92 is configured such that one end of a pair of second static pressure pocket portions 94b extending in the circumferential direction is connected in the axial direction. The first static pressure pocket portion 94a extending in the shape of a letter U has a U-shape communicating therewith. Instead, as shown in FIG. 13, the static pressure pocket 94 is formed by a pair of two first static pressure pockets 94 b extending in the circumferential direction and having a pair of two first static pressure pockets 94 b extending in the axial direction. It is also possible to adopt a rectangular shape (O-shape) in which each of the static pressure pockets 94a communicates.

  In this case, the dynamic pressure generating land 95 is formed in an island shape at a portion surrounded by the pair of first static pressure pocket portions 94a and the pair of second static pressure pocket portions 94b. Also in this case, the circumferential groove 96 is provided in the dynamic pressure generating land 95 as in the above embodiment. However, in this case, one end 96a of the circumferential groove 96 communicates with only one of the pair of first static pressure pockets 94a, and the other end 96b communicates with any of the pair of first static pressure pockets 94a. do not do. That is, also in this case, the other end 96b side of the circumferential groove 96 is provided as a closed end.

  Therefore, also in this case, turbulence can be generated in the lubricating oil flowing through the circumferential groove 96 with the rotation of the rotary shaft member 72 as in the above-described embodiment. As a result, also in this case, similarly to the above-described embodiment, the circumferential groove 96 can generate Reynolds stress, which is a stress due to turbulent flow, and can generate a preload in the bearing 90.

  In the above-described embodiment and each of the above-described modifications, the first static pressure pocket portion 94a constituting the static pressure pocket 94 is provided linearly along the axial direction. Alternatively, as shown in FIG. 14, the first static pressure pocket 94a constituting the static pressure pocket 94 may be provided in a curved shape (arc shape).

  Further, in the above-described embodiment and each of the modified examples, the circumferential groove 96 is provided linearly along the circumferential direction. Alternatively, as shown in FIG. 15, the circumferential groove 96 may be provided so as to be curved (meandering) along the circumferential direction.

  In the above-described embodiment and each of the modifications, the static pressure pocket 94 has a pair of second static pressure pockets 94b. Alternatively, as shown in FIG. 16, the second static pressure pocket 94b can be omitted to form the static pressure pocket 94.

  Further, in the above-described embodiment and each of the above-described modified examples, the spindle device having the hydrostatic bearing is used for the grinding machine 1. Alternatively, the spindle device having a hydrostatic bearing can be used for devices other than the grinder 1, for example, various measuring instruments having a rotating shaft, and bearing devices for shafts of vehicles, ships, turbines, and the like. Needless to say, there is.

  DESCRIPTION OF SYMBOLS 1 ... Grinding machine, 10 ... Bed, 11a, 11b ... Z-axis guide rail, 11c ... Z-axis ball screw, 11d ... Z-axis motor, 20 ... Headstock, 21 ... Headstock main body, 22 ... Spindle, 23 ... Spindle motor , 24 ... Tailstock center, 30 ... Tailstock main body, 32 ... Tailstock center, 40 ... Grinding stone support device, 41 ... Grinding stone traverse base, 41a, 41b ... X-axis guide rail, 41c ... X Shaft ball screw, 41d: X-axis motor, 42: Grinding wheel (rotary shaft member supporting device), 43: Grinding wheel, 50: Sizing device, 60: Control device, 70: Rotating shaft member supporting device, 71: Grinding wheel head Body, 71a, 71b Leg, 72 Rotating shaft member, 73 Bearing (hydrostatic bearing), 74 Tank, 75 Flow path, 76 Pump (lubricating oil supply device), 76a Suction port, 77 ... pressure regulating valve, 78 ... reflux path, 79 Belt / pulley mechanism, 80: grinding wheel rotation motor, 90: bearing (hydrostatic bearing), 91: bearing housing, 91a: lubricating oil supply path, 91b: discharge hole, 92: bearing member, 92a: annular groove, 92b ... communication hole, 92c ... discharge hole, 93 ... bearing surface, 94 ... static pressure pocket, 94a ... first static pressure pocket portion, 94b ... second static pressure pocket portion, 94c ... supply port, 95 ... dynamic pressure generating land, 96: circumferential groove, 96a: one end, 96b: other end, 97: drain groove, 98: axial groove, 194: static pressure pocket, Pa, Pb, Pc: support pressure, Pf: static pressure, Pg: preload, Ph: dynamic pressure, W: workpiece

Claims (8)

A bearing housing,
A bearing member fitted to the bearing housing;
A static pressure pocket formed in a concave shape on the bearing surface of the bearing member facing the outer peripheral surface of the rotating shaft member;
A dynamic pressure generating land surrounded by the static pressure pocket and formed on the bearing surface;
A supply port provided in the static pressure pocket and configured to supply lubricating oil to the static pressure pocket to regulate the lubricating oil, comprising:
A rotating shaft member supporting device that rotatably supports the rotating shaft member by the hydrostatic bearing,
The static pressure pocket,
The lubricating oil is extended along the axial direction of the bearing member, stores the lubricating oil supplied through the supply port, and generates at least the rotating shaft member and the dynamic pressure with the rotation of the rotating shaft member. It is configured to include a first static pressure pocket portion that supplies the lubricating oil to a bearing gap formed between the land and a land,
The hydrostatic bearing,
The dynamic pressure generating land extends along the circumferential direction of the bearing member, and one end in the circumferential direction communicates with the first static pressure pocket portion and the other end in the circumferential direction becomes a closed end, A rotating shaft member supporting device, comprising: a circumferential groove having a radial depth of a bearing surface larger than the size of the bearing gap and smaller than the radial depth of the first hydrostatic pocket portion. The depth of the circumferential groove,
The first static pressure pocket portion is smaller than a depth of the first static pressure pocket portion, and is smaller from the one end side toward the other end side or from the other end side toward the one end side. Rotary shaft member supporting device. The circumferential groove,
The width of the other end side in the direction along the axial direction is larger than the width of the one end side in the direction along the axial direction. Rotary shaft member support device. The hydrostatic bearing,
Adjacent to the first static pressure pocket portion and communicated with the first static pressure pocket portion, has an axial groove of a depth smaller than the depth of the first static pressure pocket portion,
The one end side of the circumferential groove,
4. The rotating shaft member supporting device according to claim 1, wherein the rotating shaft member supporting device communicates with the first static pressure pocket portion through the axial groove. 5. The static pressure pocket,
The first static pressure pocket portion extending along the circumferential direction, communicating with the first static pressure pocket portion, and having a second static pressure pocket portion separated from the circumferential groove along the circumferential direction. Item 5. The rotating shaft member supporting device according to any one of items 4. The static pressure pocket,
The U-shaped shape in which each end of the first static pressure pocket in the axial direction and a pair of the second static pressure pockets separated from each other in the circumferential direction are connected. Item 6. The rotating shaft member supporting device according to Item 5. The circumferential groove,
The rotating shaft member supporting device according to any one of claims 1 to 6, wherein a plurality of the dynamic pressure generating lands are provided. The rotary shaft member rotatably supported by the rotary shaft member support device according to any one of claims 1 to 7, and holding a grinding wheel,
A tank for storing the lubricating oil,
A flow passage for connecting the tank and the hydrostatic bearing to flow the lubricating oil,
A lubricating oil supply device disposed in the flow passage, for supplying the lubricating oil stored in the tank to the hydrostatic pocket of the hydrostatic bearing;
A recirculation path for recirculating the lubricating oil discharged from the hydrostatic bearing to the tank.

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