JP2020200898A - Rotational shaft member support device and grinder - Google Patents

Abstract

To provide a rotational shaft that has a static pressure fluid bearing capable of applying a preload to suppress occurrence of cavitation with a simple and inexpensive structure, and provide a grinder.SOLUTION: A bearing 90 comprises a preload groove 96 that extends along an axial direction within a dynamic pressure generation land 95, of which a base end part 96a communicates with a second static pressure pocket part 94b of a static pressure pocket 94, and a tip part 96b is a recess part that becomes a closed end at a position where it is separated from a first static pressure pocket part 94a in a circumferential direction, and in which a depth of a bearing surface 93 in a radial direction is larger than at least the size of a bearing gap formed between a rotational shaft member 72 and the dynamic pressure generation land 95 as the rotational shaft member 72 rotates, and is smaller than a depth of the static pressure pocket 94 in the radial direction.SELECTED DRAWING: Figure 4

Description

The present invention relates to a rotary shaft member support device and a grinder provided with the rotary shaft member support device.

Conventionally, a fluid bearing used for a spindle of a machine tool or the like has been proposed to be provided with a discharge hole for discharging the lubricating oil in a land portion where the lubricating oil tends to generate heat due to the generation of dynamic pressure ( For example, see Patent Document 1 etc.).

Further, Patent Document 2 proposes a fluid bearing device in which a U-shaped static pressure pocket is provided in a direction in which dynamic pressure is applied to a rotating shaft member, and a quadrangular static pressure pocket is provided in the other direction. ing. According to this prior art device, the U-shaped static pressure pocket maintains the required rigidity and supports the load force acting on the rotating shaft, while the square static pressure pocket has a large area and therefore the rotating shaft. The chances of contact with cold lubricating oil increase and heat generation is prevented.

Further, Patent Document 3 proposes a hydrostatic bearing device in which a recess is provided in a land portion surrounded by a U-shaped bearing pocket. According to this conventional device, oil collects in a recess recessed in a land portion surrounded by a U-shaped bearing pocket, and even if a power failure occurs, the rotating shaft rotates for a while, and the oil in the recess Since the pressure does not escape, the rotating shaft is radially supported by the dynamic pressure between the rotating shaft and the recess and between the rotating shaft and the land portion, and the area of the land portion becomes relatively small, reducing friction loss and reducing power consumption. Reduce.

Further, Patent Document 4 describes a support portion that generates static pressure, a land portion that is uniformly projected from the support portion and generates dynamic pressure, and a predetermined step formed between the support portion and the land portion. A fluid bearing device having the above steps has been proposed.

Japanese Patent No. 4134541 Japanese Unexamined Patent Publication No. 2001-304260 Jikkenhei 5-22843 JP-A-54-90434

Generally, in a rotary shaft member support device having a hydrostatic fluid bearing, lubricating oil is supplied to a static pressure pocket provided in the hydrostatic fluid bearing, and the rotary shaft member is statically supported by the supplied lubricating oil. Further, in the rotary shaft member support device having a hydrostatic fluid bearing, when the rotary shaft member is eccentric, the wedge effect in the wedge-shaped gap formed by the difference between the outer diameter of the rotary shaft member and the inner diameter of the hydrostatic fluid bearing causes. The rotating shaft member is dynamically supported by generating a 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 dynamic pressure is small, and as a result, the hydrostatic fluid bearing The rotation of the rotating shaft member may become unstable due to the cavitation generated inside the rotating shaft member.

On the other hand, in the conventional device disclosed in Patent Document 4, the bearing is provided with an inclination, a step, or the like so as to reduce the gap between the bearing surface and the outer peripheral surface of the rotating shaft member along the circumferential direction of the bearing surface. It is designed to increase the preload. As a result, the occurrence of cavitation inside the hydrostatic fluid bearing is suppressed and the eccentricity (eccentric angle) of the rotating shaft member is suppressed.

However, the inclination, the step, etc. have a processing depth of about several μm to a dozen 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 processing depth, it is necessary to perform, for example, etching processing or ultra-precision processing along the circumferential direction of the bearing surface, and there is a problem that the manufacturing cost becomes extremely high.

An object of the present invention is to provide a rotary shaft member support device and a grinder having a hydrostatic fluid bearing capable of applying a preload and suppressing the occurrence of cavitation with a structure that can be manufactured easily and at low cost.

The rotating shaft member support device according to the present invention is a static pressure formed concavely on a bearing housing, a bearing member fitted in the bearing housing, and a bearing surface of the bearing member facing the outer peripheral surface of the rotating shaft member. A pocket, a dynamic pressure generating land surrounded by the static pressure pocket and formed on the bearing surface, and a supply port provided in the static pressure pocket to adjust the pressure of lubricating oil and supply it to the static pressure pocket. It is a rotary shaft member support device that includes a hydrostatic fluid bearing and rotatably supports the rotary shaft member by the hydrostatic fluid bearing.

Then, in the rotary shaft member support device according to the present invention, the static pressure pocket extends along the axial direction of the bearing member to store the lubricating oil supplied through the supply port, and also A first static pressure pocket portion for supplying the lubricating oil to a bearing gap formed at least between the rotating shaft member and the dynamic pressure generating land as the rotating shaft member rotates, and the first static pressure pocket. A pair of second static pressure pocket portions, each of which has a first end communicating with both ends in the axial direction of the portion and extends from the first end side to the second end side along the circumferential direction. It has a U-shape.

Further, the hydrostatic fluid bearing is further extended in a direction in which at least a part thereof has a component in the axial direction in the dynamic pressure generating land, the base end portion communicates with the hydrostatic pocket, and the tip portion A recess that becomes a closed end at a position separated from the first static pressure pocket portion in the circumferential direction, and the depth of the bearing surface in the radial direction is larger than the size of the bearing gap and the static pressure pocket is said to have the same. It has a preload groove that is smaller than the depth in the radial direction.

The grinding machine according to the present invention is rotatably supported by the rotary shaft member support device, and connects a rotary shaft member that holds a grind wheel, a tank that stores lubricating oil, a tank, and a hydrostatic fluid bearing. A flow passage for circulating lubricating oil, a lubricating oil supply device for supplying the lubricating oil stored in the tank to the static pressure pocket of the static pressure fluid bearing, and a lubricating oil supply device disposed in the flow passage, and discharged from the static pressure fluid bearing. It is provided with a recirculation path for returning the lubricating oil to the tank.

According to these, the hydrostatic fluid bearing of the rotary shaft member support device is extended in the direction in which at least a part of the dynamic pressure generating land has an axial component, and the base end portion communicates with the static pressure pocket. A recess that becomes a closed end at a position where the tip portion is separated from the first static pressure pocket portion in the circumferential direction, and the depth of the bearing surface in the radial direction is larger than the size of the bearing gap and in the radial direction of the static pressure pocket. A preload groove that is smaller than the depth is provided. As a result, it is not necessary to form the preload groove by ultra-precision machining, and it can be formed with a simple structure and at low cost, and the manufacturing cost of the grinder equipped with the hydrostatic fluid bearing and the rotary shaft member support device is reduced. It has the effect of being able to.

Further, at least a part of the dynamic pressure generating land is extended in the direction having the component in the axial direction, the base end portion communicates with the static pressure pocket, and the tip portion extends from the first static pressure pocket portion in the circumferential direction. By providing the preload groove, which is a recess that serves as a closed end at a separated position, turbulence occurs in the lubricating oil existing in the preload groove as the rotating shaft member rotates. As a result, preload can be effectively applied in the so-called wedge-shaped gap, which is generated due to the bearing gap and the eccentricity of the rotating shaft member. Therefore, even when the rotary shaft member is eccentric, the occurrence of cavitation inside the hydrostatic fluid bearing can be suppressed, and the hydrostatic fluid bearing is located between the rotary shaft member and the hydrostatic fluid bearing. It has the effect of suppressing the occurrence of seizure and the like so that the rotating shaft member can be rotated stably.

It is a top view of the grinder of one Embodiment of the rotary shaft member support device which concerns on embodiment. It is sectional drawing of the grindstone stand along the line II-II shown in FIG. It is a front view of the grindstone stand main body shown in FIG. It is sectional drawing which shows the structure of the hydrostatic fluid bearing shown in FIG. It is a partial cross-sectional view for demonstrating the pressure generated between a rotary shaft member and a bearing surface (dynamic pressure generation land) by a static pressure pocket and a preload groove. It is explanatory drawing which shows typically the hydrostatic fluid bearing which concerns on the comparative example which does not have a preload groove. It is a partial cross-sectional view for demonstrating the pressure generated between a rotary shaft member and a bearing surface (dynamic pressure generation land) in a comparative example. It is explanatory drawing which shows typically the hydrostatic fluid bearing which concerns on 1st modification of embodiment of this invention. It is explanatory drawing which shows typically the hydrostatic fluid bearing which concerns on the 2nd modification of embodiment of this invention. It is explanatory drawing which shows typically the hydrostatic fluid bearing which concerns on the 3rd modification of embodiment of this invention. It is explanatory drawing which shows typically the hydrostatic fluid bearing which concerns on the 4th modification of embodiment of this invention.

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

The bed 10 is formed in a rectangular shape in a plane 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 the grindstone base traverse base 41, which will be described later, to form a grindstone support device 40, extend in parallel with each other along the Z-axis direction. It is fixed. A Z-axis ball screw 11c for driving the grindstone 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 on the upper surface of the bed 10.

The headstock 20 includes a headstock main 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 so that the axial direction of the main shaft 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 (on the left side in FIG. 1). As a result, the spindle 22 is rotationally driven around the Z axis with respect to the spindle base main body 21 by the spindle motor 23. The spindle motor 23 is provided with an encoder that detects the rotation angle of the spindle motor 23. Further, at the other end of the spindle 22 (on the right side of the paper surface in FIG. 1), a spindle center 24 for supporting one end of the shaft-shaped workpiece W in the axial direction is provided.

The tailstock 30 includes a tailstock main 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 faces the Z-axis direction and the rotation axis of the tailstock center 32 is coaxial with the rotation axis of the main shaft 22. Has been done. That is, the tailstock center 32 supports both ends of the workpiece W in the axial direction together with the spindle center 24, and is arranged so that the workpiece W can rotate around the Z axis. The push center 32 is configured so that the amount of protrusion from the end face of the push base main body 31 can be changed according to the length of the workpiece W.

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

The grindstone base 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 the Z-axis motor 11d. 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 that allow the grindstone base 42 to slide are fixed and extended in parallel with each other and along the X-axis direction on the upper surface of the grindstone base traverse base 41. .. An X-axis ball screw 41c for driving the grindstone base 42 in the X-axis direction is arranged between the pair of X-axis guide rails 41a and 41b fixed to the upper surface of the grindstone base traverse base 41, and the X-axis. An X-axis motor 41d that rotationally drives the ball screw 41c is arranged. The X-axis motor 41d is provided with an encoder that detects the rotation angle of the X-axis motor 41d.

The grindstone base 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 base traverse base 41. The grindstone base 42 is connected to a nut member (not shown) of the X-axis ball screw 41c, and can be moved along a pair of X-axis guide rails 41a and 41b by driving the X-axis motor 41d. As a result, the grindstone base 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 base 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 the grinding site. The sizing device 50 outputs a measurement signal representing the measured outer diameter to the control device 60.

The control device 60 is a device that controls the drive of each motor including the Z-axis motor 11d and the X-axis motor 41d. By driving each motor, the control device 60 rotates the workpiece W and the grindstone 43 around the Z-axis, and changes the relative positions of the grindstone 43 with respect to the workpiece W in the Z-axis direction and the X-axis direction. The outer peripheral surface of the workpiece W is ground.

(3. Details of the rotating shaft member support device 70 (grinding stone stand 42))
As shown in FIG. 2, the rotary shaft member support device 70 as the grindstone base 42 includes a grindstone base main body 71 as a support base, a rotary shaft member 72, a bearing 73 as a hydrostatic fluid bearing, and a tank 74. It includes a flow passage 75, a pump 76 as a lubricating oil supply device, a pressure regulating valve 77, and a return passage 78. The grindstone base body 71 rotatably supports the rotary shaft member 72 by a bearing 73. As shown in FIGS. 2 and 3, the lower end of the grindstone base body 71 is formed so as to extend in the X-axis direction and is guided along the pair of X-axis guide rails 41a and 41b. (In FIG. 2, only the leg portion 71b is shown) is provided.

The rotary shaft member 72 holds the grindstone 43 and is rotationally driven. The rotary shaft member 72 is rotatably supported around the Z axis on the upper surface of the grindstone base main body 71. A disk-shaped grindstone 43 is coaxially attached to one end of the rotating shaft member 72. Further, a grindstone rotation motor 80 for rotationally driving the rotary shaft member 72 together with the grindstone 43 is fixed on the upper surface of the grindstone base main body 71 via a belt / pulley mechanism 79 (see FIG. 1).

The bearing 73 is a hydrostatic fluid bearing, and as shown in FIG. 3, rotatably supports the rotary shaft member 72 at a position separated along the Z-axis direction of the rotary shaft member 72. In order to statically support the rotary shaft member 72, the lubricating oil stored in the tank 74 is adjusted and supplied to the bearing 73 (see FIG. 2). The configuration of the bearing 73 (90) will be described in detail later.

As shown in FIGS. 1 to 3, the tank 74 is arranged in the upper part of the grindstone base main body 71 and stores the lubricating oil. Specifically, the tank 74 is formed so as to be recessed from the upper surface (upper side of the paper surface in FIG. 2) of the grindstone base main body 71 toward the lower side (lower side of the paper surface in FIG. 2) and to open the upper side. ing. Further, 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 path through which the lubricating oil pumped from the tank 74 by the pump 76 flows. In the present embodiment, as shown in FIG. 2, the flow passage 75 is arranged outside the grindstone base main body 71, but it can also be arranged inside the grindstone base 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 base main body 71 in a state where the suction port 76a is immersed in the lubricating oil stored in the tank 74. As a result, the pump 76 pumps the lubricating oil stored in the tank 74 from the suction port 76a, and supplies the pumped lubricating oil to the bearing 73 via the flow passage 75.

Here, the pump 76 is electrically connected to the control device 60, and its operation is controlled by the control device 60. As a result, the pump 76 adjusts the flow rate, hydraulic 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.

As shown in FIG. 2, the pressure regulating valve 77 is arranged on the upstream side of the bearing 73 in the flow passage 75. With this arrangement, the pressure regulating valve 77 regulates the pressure of the lubricating oil supplied to the bearing 73, which is a hydrostatic fluid bearing, to a predetermined pressure. As the pressure adjusting valve 77, for example, a direct acting pressure reducing valve or the like can be used, or can be omitted.

As shown in FIG. 2, the return path 78 is a flow path for returning the lubricating oil discharged from the bearing 73 to the tank 74. 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 by its own weight via the return path 78. The return path 78 can also 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, the bearing 90, which is a hydrostatic fluid 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 on the outer peripheral side of the rotating shaft member 72 is fitted and integrated into the inner peripheral surface of the bearing housing 91 by press fitting, shrink fitting, or the like.

Further, the bearing 90 has a static pressure pocket 94, a dynamic pressure generating land 95, a pair of preload grooves 96, and a drain groove 97 provided on the bearing surface 93 of the bearing member 92. .. As a result, the bearing 90 can support the rotary shaft member 72 under static pressure and also at dynamic pressure.

As shown in FIG. 4, 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. Specifically, the static pressure pocket 94 is a first static pressure pocket extending along the axial direction of the bearing member 92 (a direction that coincides with the axial direction of the rotating shaft member 72, for example, the Z-axis direction). A pair of second static pressure pockets extending from both ends of the portion 94a and the first static pressure pocket portion 94a in the axial direction along the circumferential direction of the bearing member 92 (the direction corresponding to the circumferential direction of the rotating shaft member 72). It is composed of a part 94b and a part 94b. A plurality of static pressure pockets 94 are provided along the circumferential direction of the bearing member 92, for example, about four to six places.

Here, in the description of the present specification, the abstract, and the scope of claims, "along the axis direction" includes a direction that exactly coincides with the axis line and has a component in a direction orthogonal to the axis line. It is a concept including a direction having an intersection with an axis (for example, a direction of 45 degrees or less with respect to the axis) when projected onto a virtual plane. Further, in the description of the present specification, the abstract, and the scope of patent claims, "along the circumferential direction" includes a direction that exactly coincides with the line of intersection between the plane and the peripheral surface orthogonal to the axis, and intersects. It is a concept including a direction having a component in a direction orthogonal to the line and having an intersection with the line of intersection when projected on a virtual plane (for example, a direction of 45 degrees or less with respect to the line of intersection).

In the present embodiment, the first static pressure pocket portion 94a is opened with a supply port 94c for supplying lubricating oil. The supply port 94c includes a lubricating oil supply path 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 path 91a, and an annular shape. It communicates with the groove 92a and communicates with the communication hole 92b which acts as a drawing.

The dynamic pressure generating land 95 is formed in a portion of the U-shaped static pressure pocket 94 surrounded by the first static pressure pocket portion 94a and the pair of second static pressure pocket portions 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 as will be described later, the dynamic pressure is generated with the rotation of the rotating shaft member 72.

As shown in FIG. 4, the pair of preload grooves 96 communicate with each other in the pair of second static pressure pocket portions 94b near the tips in the circumferential direction and face each other, and move toward the dynamic pressure generation land 95 side in the axial direction. It has been extended. Each preload groove 96 is provided so as to have a depth of about several hundred μm from the dynamic pressure generating land 95 (bearing surface 93), as shown by the cross-sectional view substantially developed in FIG. That is, each preload groove 96 has a depth of the bearing surface 93 in the radial direction larger than the size of the bearing gap (several μm to ten and several μm), and the first static pressure pocket portion 94a constituting the static pressure pocket 94. The second static pressure pocket portion 94b is provided so as to be shallower (for example, about 1/10) than the depth (for example, 1 to 1.5 mm). That is, each preload groove 96 has a closed end that communicates with the second static pressure pocket portion 94b on the base end portion 96a side, and does not communicate with any portion of the static pressure pocket 94 on the tip end portion 96b side. As a result, as will be described later, the lubricating oil supplied to each base end portion 96a of each preload groove 96 via the pair of second static pressure pocket portions 94b with the rotation of the rotary shaft member 72 is supplied to each tip portion. By being blocked by 96b, it becomes a turbulent flow and dynamic pressure is generated.

The drain groove 97 is a bearing surface of the bearing member 92 so as to be adjacent to the second static pressure pocket portion 94b of the U-shaped static pressure pocket 94, that is, to be located at both ends in the axial direction of the static pressure pocket 94. It is provided in 93. The drain groove 97 communicates with the discharge holes 92c and the discharge holes 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 passage 78, and the lubricating oil flowing into the drain groove 97 is discharged to the tank 74 and recovered.

Here, the operation of the bearing 90 configured as described above will be described. The lubricating oil pumped up by the pump 76 is regulated to about several Mpa by passing through the flow passage 75 and the pressure regulating valve 77, and passes through the communication hole 92b that performs a drawing action from the annular groove 92a on the outer periphery of the bearing member 92. Finally, it is supplied to the static pressure pocket 94. Then, for example, in a state where the rotary 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 and the preload groove 96 is applied to the outer periphery of the rotary shaft member 72. A lubricating oil film is formed by forcibly supplying the surface to the gap (bearing gap) between the surface and the bearing surface 93 including the dynamic pressure generating land 95, and static pressure is generated. As a result, the non-eccentric rotating shaft member 72 is statically supported.

When there is a bearing gap between the dynamic pressure generating land 95 and the rotating shaft member 72, the rotating shaft member 72 is not eccentric. Therefore, the lubricating oil flowing from the U-shaped static pressure pocket 94 generates the same static pressure as the static pressure pocket 94 in the dynamic pressure generating land 95.

On the other hand, when the grindstone 43 comes into contact with the workpiece W for grinding, a machining (grinding) reaction force acts on the rotary shaft member 72 to eccentric the central shaft of the rotary shaft member 72. In this way, when the central shaft is eccentric, the bearing gap gradually narrows toward the eccentric side due to 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). A gap is formed. When the lubricating oil is drawn around the surface of the rotating shaft member 72 that rotates in the wedge-shaped gap, dynamic pressure is generated in the dynamic pressure generating land 95, and the rotating shaft member 72 is dynamically supported.

Here, the static pressure and dynamic pressure support of the rotary shaft member 72 by the bearing 90 will be described with reference to FIG. 5 in which the cylindrical bearing 90 is developed for convenience. As shown in FIG. 5, the dynamic pressure generating land 95 is formed along the axial direction so as to be shallower than the static pressure pocket 94, and the base end portion 96a communicates with the static pressure pocket 94 and the tip portion thereof. A preload groove 96 is provided so that 96b is a closed end. As a result, static pressure Pf is applied to the rotary shaft member 72 by the static pressure pocket 94 (more specifically, the second static pressure pocket portion 94b). Further, when the rotating shaft member 72 rotates, the lubricating oil flows from the static pressure pocket 94 into the base end portion 96a of each preload groove 96 and is blocked regardless of whether the central shaft of the rotating shaft member 72 is eccentric or not. It flows as a turbulent flow toward the tip portion 96b, which is the end.

When the flow of lubricating oil in the preload groove 96 becomes turbulent, as shown in FIG. 5, turbulent stress, so-called Reynolds stress, is generated at the formation position of the preload groove 96, and the outer peripheral surface of the rotary shaft member 72 is generated. This Reynolds stress acts as a preload Pg. That is, when the preload groove 96 is provided in the dynamic pressure generation land 95, the static pressure Pf and the preload Pg associated with the Reynolds stress always act on the rotating rotary shaft member 72.

As shown in FIG. 5, 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 in 93 acts on the rotary shaft member 72. As shown in FIG. 5, the static pressure Pf is maintained in the portion corresponding to the second static pressure pocket portion 94b.

The bearing 90 has two pairs of preload grooves 96 between the pair of second static pressure pocket portions 94b, that is, in the dynamic pressure generation land 95. Further, each tip portion 96b of the pair of preload grooves 96 is provided so as to be separated from the first static pressure pocket portion 94a in the circumferential direction. Therefore, in the state where the rotary shaft member 72 is rotating, the lubricating oil in the preload groove 96 flows through the dynamic pressure generation land 95 due to the turbulent flow, so that the preload Pg based on the Reynolds stress in addition to the static pressure Pf Is generated and acts on the rotary shaft member 72.

In the dynamic pressure generating land 95 of the bearing 90, a bearing gap is formed when the rotating rotating shaft member 72 is not eccentric, and the static pressure Pf and the preload Pg are formed between the pair of preload grooves 96. A bearing pressure Pa that is slightly lower than the total pressure is generated.

Then, in the dynamic pressure generating land 95, when the rotating shaft member 72 is eccentric, a large dynamic pressure Ph is generated due to the formation of a wedge-shaped gap on the side where the rotating shaft member 72 approaches, and as a result, FIG. As shown by the alternate long and short dash line, a supporting pressure Pb that is convex upward is generated. On the other hand, on the side where the rotary shaft member 72 is separated, a gap larger than the bearing gap is generated, and as a result, the support pressure Pc is greatly reduced as shown by the broken line in FIG.

(5. Comparison with comparative example)
Next, the pressure generated between the rotary shaft member 72 and the bearing surface 93 will be described in comparison with the bearing 90 of the present embodiment and the bearing 190 of the comparative example having no preload groove 96 shown in FIG. .. In the bearing 90 having the preload groove 96, the preload Pg is applied as described above. Therefore, even when the support pressure Pc is significantly reduced due to the eccentricity of the rotating shaft member 72, the support pressure Pc is prevented from becoming a negative pressure as shown in FIG. On the other hand, in the bearing 190 of the comparative example not having the preload groove 96 shown in FIG. 6, as shown in FIG. 7, only the static pressure Pf by the second static pressure pocket portion 94b is applied and the preload Pg by the preload groove 96 is applied. Not done. Therefore, when the rotating shaft member 72 is eccentric, the supporting pressure Pc becomes a negative pressure as shown by the broken line in FIG. 7, and as a result, cavitation occurs inside the bearing 90, that is, in the bearing member 92.

As described above, when the preload Pg formed by the preload groove 96 acts on the rotating shaft member 72, the preload Pg is applied to the above-mentioned support pressures Pa, Pb, and Pc as shown in FIG. Therefore, for example, even when the rotary shaft member 72 is shaken (eccentric) due to the grindstone 43 coming into contact with the workpiece W during grinding, the supporting pressure Pc (dynamic pressure) is negative. The generation of negative pressure is suppressed, and as a result, the generation of cavitation is suppressed.

(6. Summary)
As described above, according to the present embodiment, the bearing 90 is extended in the dynamic pressure generating land 95 in the direction having the component in the axial direction (particularly along the axial direction), and the base end portion 96a has a static pressure. A recess that communicates with the second static pressure pocket portion 94b of the pocket 94 and becomes a closed end at a position where the tip portion 96b is separated from the first static pressure pocket portion 94a in the circumferential direction in the radial direction of the bearing surface 93. The depth is at least larger than the size of the bearing gap formed between the rotating shaft member 72 and the dynamic pressure generating land 95 with the rotation of the rotating shaft member 72, and compared with the radial depth of the static pressure pocket 94. The small preload groove 96 is provided.

Further, the grinding machine 1 including the rotary shaft member support device 70 as the grindstone base 42 is rotatably supported by the rotary shaft member support device 70 as the grindstone base 42 to hold the grindstone wheel 43, and the rotary shaft member 72. The tank 74 for storing the lubricating oil, the flow passage 75 for connecting the tank 74 and the bearing 73 (90) to flow the lubricating oil, and the bearing for the lubricating oil disposed in the flow passage 75 and stored in the tank 74. It includes a pump 76 as a lubricating oil supply device for supplying the static pressure pocket 94 of the 73 (90), and a return passage 78 for returning the lubricating oil discharged from the bearing 73 (90) to the tank 74.

According to these, the preload groove 96 does not need to be formed by ultra-precision machining, can be formed with a simple structure and at low cost, and the bearing 90 (73) and the rotary shaft member support device 70 can be used as the grindstone base 42. This has the effect of reducing the manufacturing cost of the provided grinder 1.

In the present embodiment, the pair of preload grooves 96 are extended in the direction in which the axial direction is the main component as a whole, and each base end portion 96a is formed in the pair of second static pressure pocket portions 94b. In addition to communicating with each other, the tip portions 96b are extended so as to face each other. Further, the dynamic pressure generating land 95 is extended along the axial direction, the base end portion 96a communicates with the static pressure pocket 94 (second static pressure pocket portion 94b), and the tip portion 96b is the first static pressure portion 96b. A preload groove 96, which is a recess that serves as a closing end, is provided at a position separated from the compression pocket portion 94a in the circumferential direction (specifically, a position equivalent to the second end 94b2 of the second static pressure pocket portion 94b in the circumferential direction). As a result, turbulence is generated in the lubricating oil existing in the preload groove 96 as the rotary shaft member 72 rotates. As a result, the preload can be effectively applied in the so-called wedge-shaped gap, which is generated due to the bearing gap and the eccentricity of the rotating shaft member 72. Therefore, even when the rotating shaft member 72 is eccentric, the occurrence of cavitation inside the bearing 90 (73) can be suppressed, and the bearing 90 (73) can be the rotating shaft member 72 and the bearing 90 (73). ) Suppresses the occurrence of seizure and the like, and the rotary shaft member 72 can be stably rotated.

Further, the preload groove 96 is provided so that the tip portion 96b is closer to each second end 94b2 than each first end 94b1 of the pair of second static pressure pocket portions 94b in the circumferential direction. According to this configuration, a wide preload is applied in the circumferential direction within the dynamic pressure generation land 95, and the generation of negative pressure can be effectively suppressed.

Further, the preload grooves 96 are provided in pairs on both sides of the static pressure pocket 94 with the center in the axial direction interposed therebetween. According to this configuration, a wide preload is applied in the axial direction in the dynamic pressure generation land 95, and the generation of negative pressure can be effectively suppressed. Further, in the pair of preload grooves 96, each base end portion 96a communicates with each other in the vicinity of each second end 94b2 of the pair of second static pressure pocket portions 94b, and the respective tip portions 96b communicate with each other along the axial direction. It is extended so as to face each other. According to this configuration, a preload is widely and effectively applied in the dynamic pressure generation land 95, and the generation of negative pressure can be effectively suppressed.

(7. First modification)
In the above embodiment, in the pair of preload grooves 96, each base end portion 96a communicates with the pair of second static pressure pocket portions 94b, and the respective tip portions 96b face each other along the axial direction. However, the configuration of the preload groove 96 is not limited to this. The base end portion 96a of the preload groove 96 may be configured to communicate with the first static pressure pocket portion 94a of the static pressure pocket 94. Further, the preload groove 96 is not limited to one in which the entire extension direction is exactly along the axial direction, and only a part of the preload groove 96 may be exactly along the axial direction. For example, in the first modification, as shown in FIG. 8, each base end portion 96a of the pair of preload grooves 96 communicates with the first static pressure pocket portion 94a. Further, in this modification, each of the pair of preload grooves 96 includes a first portion 96c including a base end portion 96a and extending in a direction mainly in the circumferential direction, and a tip portion 96b and includes an axial direction. It has a second portion 96d extending in the direction of the main component. The first portion 96c is a portion extending from the base end portion 96a along the circumferential direction, and extends to the vicinity of the same position as each second end 94b2 of each second static pressure pocket portion 94b in the circumferential direction. .. The second portion 96d is bent at a right angle from the end portion of the first portion 96c opposite to the base end portion 96a toward the axial center side of the static pressure pocket 94, and the respective tip portions 96b are bent along the axial direction. It is extended so as to face each other. This modification also has the same effect as that of the above embodiment.

(8. Second modification)
In the first modification, a part of the preload groove 96 (first part 96c) is extended along the circumferential direction, and the remaining part (second part 96d) is extended along the axial direction. The entire groove 96 may be extended in an oblique direction having both an axial component and a circumferential component. In the second modification, as shown in FIG. 9, in the pair of preload grooves 96, each base end portion 96a communicates with the first static pressure pocket portion 94a, and the extension direction is mainly the circumferential component as a whole. It is a direction to be a component, is an oblique direction having both a circumferential component and an axial component, and is extended in a V shape in which the tip portions 96b are separated from each other in the axial direction. This modification also has the same effect as that of the above embodiment.

(9. Third modified example)
In the third modification, as shown in FIG. 10, each base end portion 96a of the pair of preload grooves 96 communicates with the first static pressure pocket portion 94a, and the extension direction is mainly composed of a circumferential component. It is extended in an inverted C shape having both a circumferential component and an axial component in an oblique direction and the tip portions 96b approach each other in the axial direction. This modification also has the same effect as that of the above embodiment.

(10. Fourth modified example)
In the fourth modification, as shown in FIG. 11, instead of the inverted C shape in the third modification in which the tip portions 96b of the pair of preload grooves 96 are separated from each other and are not in communication with each other, both The tip 96b is provided so as to communicate with each other and extends in a V shape that acts as one closed end. This modification also has the same effect as that of the above embodiment.

(11. Other modified examples)
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. In the above embodiment, two pairs of preload grooves 96 are provided, but only one preload groove 96 may be provided. Further, in the above embodiment, the preload groove 96 is extended in a straight line, but it may be extended in a curved line. In short, the preload groove 96 may be configured to extend in the direction in which at least a part of the dynamic pressure generation land 95 has a component in the axial direction.

Further, in the above-described embodiment and each modification, an example is shown in which the tip portion 96b of the preload groove 96 is provided near the same position as each second end 94b2 of each second static pressure pocket portion 94b in the circumferential direction. Is not limited. The preload groove 96 may be a closed end at a position where the tip portion 96b is separated from the first static pressure pocket portion 94a in the circumferential direction, and each first end of the pair of second static pressure pocket portions 94b in the circumferential direction. It is preferable that the configuration is provided closer to each second end 94b2 than 94b1. Further, in the above embodiment, the pair of preload grooves 96 are configured such that each base end portion 96a communicates with each other in the vicinity of each second end 94b2 of the pair of second static pressure pocket portions 94b. It may be configured to communicate with any position in the compression pocket portion 94b. Further, also in the above-described embodiment and the first modified example, as in the third modified example, the tip portions 96b may be provided in a communicative state to act as one closed end.

1 ... Grinding machine, 42 ... Grinding table (rotary shaft member support device), 43 ... Grinding wheel, 70 ... Rotating shaft member support device, 72 ... Rotating shaft member, 73 ... Bearing (hydrostatic fluid bearing), 74 ... Tank, 75 ... flow passage, 76 ... pump (lubricating oil supply device), 78 ... return path, 90 ... bearing (hydrostatic fluid bearing), 91 ... bearing housing, 92 ... bearing member, 93 ... bearing surface, 94 ... static pressure pocket , 94a ... 1st static pressure pocket, 94b ... 2nd static pressure pocket, 94b1 ... 1st end, 94b2 ... 2nd end, 94c ... Supply port, 95 ... Dynamic pressure generation land, 96 ... Preload groove, 96a ... Base end, 96b ... tip, 96c ... first part, 96d ... second part.

Claims (12)

Bearing housing and
The bearing member fitted to the bearing housing and
A static pressure pocket formed concavely on the bearing surface of the bearing member facing the outer peripheral surface of the rotating shaft member, and
A dynamic pressure generating land surrounded by the static pressure pocket and formed on the bearing surface,
A hydrostatic fluid bearing provided in the static pressure pocket is provided with a supply port for adjusting the pressure of lubricating oil and supplying the lubricating oil to the static pressure pocket.
A rotary shaft member support device that rotatably supports the rotary shaft member by the hydrostatic fluid bearing.
The static pressure pocket
The lubricating oil is extended along the axial direction of the bearing member to store the lubricating oil supplied through the supply port, and at least the rotary shaft member and the dynamic pressure are generated as the rotary shaft member rotates. The first static pressure pocket portion that supplies the lubricating oil to the bearing gap formed between the land and the land,
A pair of two second static pressures having a first end communicating with both ends of the first static pressure pocket portion in the axial direction and extending from the first end side to the second end side along the circumferential direction. It has a pocket and is formed in a U shape.
The hydrostatic fluid bearing further
At least a part of the dynamic pressure generating land is extended in the direction having the component in the axial direction, the base end portion communicates with the static pressure pocket, and the tip portion is from the first static pressure pocket portion in the circumferential direction. A preload groove that is a recess that becomes a closed end at a position separated from the bearing surface, and the depth of the bearing surface in the radial direction is larger than the size of the bearing gap and smaller than the depth of the static pressure pocket in the radial direction. Rotating shaft member support device. The rotation shaft according to claim 1, wherein the preload groove is provided at a tip portion closer to each second end of the pair of second static pressure pocket portions than each first end portion in the circumferential direction. Member support device. The rotary shaft member support device according to claim 1 or 2, wherein the preload grooves are provided in pairs on both sides of the static pressure pocket with the center in the axial direction interposed therebetween. The rotary shaft member support device according to claim 3, wherein each of the pair of preload grooves extends in a direction in which the axial direction is the main component. The fourth aspect of the present invention, wherein each of the pair of preload grooves communicates with the pair of second static pressure pocket portions, and the tip portions thereof extend so as to face each other. Rotating shaft member support device. In the pair of preload grooves, the base end portions communicate with each other in the vicinity of the second end portions of the pair of second static pressure pocket portions, and the tip portions thereof face each other in the axial direction. The rotary shaft member support device according to claim 5, which is extended to. The rotary shaft member support device according to claim 3, wherein each of the pair of preload grooves extends in a direction in which the component in the circumferential direction is a main component. Each of the pair of preload grooves has a first portion having the base end portion communicating with the first static pressure pocket portion and extending in a direction including the base end portion and having the circumferential direction as a main component. The rotary shaft member support device according to claim 7, further comprising a second portion including the tip portion and extending in a direction containing the axial direction as a main component. The pair of preload grooves are claimed so that the base end portion communicates with the first static pressure pocket portion and extends to the tip portion in a direction having the circumferential component and the axial component, respectively. Item 7. The rotating shaft member support device according to item 7. The rotary shaft member support device according to any one of claims 3 to 9, wherein the pair of preload grooves are provided in a non-communication state with each other. The rotary shaft member support device according to any one of claims 3 to 9, wherein the pair of preload grooves are provided in a state of communicating with each other. A rotary shaft member that is rotatably supported by the rotary shaft member support device according to any one of claims 1 to 11 to hold a grindstone.
A tank for storing the lubricating oil and
A flow passage that connects the tank and the hydrostatic fluid bearing to allow the lubricating oil to flow, and
A lubricating oil supply device disposed in the flow passage and supplying the lubricating oil stored in the tank to the static pressure pocket of the hydrostatic fluid bearing.
A grinder provided with a return path for returning the lubricating oil discharged from the hydrostatic fluid bearing to the tank.

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