JP2008298275A - Static pressure gas bearing and rotating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a static pressure gas bearing capable of easily adjusting a clearance between a rotor and a radial bearing pad. <P>SOLUTION: The static pressure gas bearing supporting the rotor comprises the radial bearing pad 3 supporting the rotor in a radial direction, a linear guide 1c moving the radial bearing pad 3, and a ball stud 4 rockingly uniting the radial bearing pad 3 to a linear guide 1c. A direction in which the linear guide 1c moves the radial bearing pad 3 intersects with a direction in which the rotation center of the rotor and the ball stud 4 are united. In regard to a change amount of a bearing clearance between the outer peripheral surface 2c of the rotor and the radial bearing pad 3, a movement adjusting amount for moving the radial bearing pad 3 by the linear guide 1c is large, so that a minute amount of the bearing clearance can be accurately adjusted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a static pressure gas bearing and a rotating device, and particularly to a static pressure gas bearing that supports a rotating body and a rotating device including the static pressure gas bearing.

  In the field where a rolling bearing has been used for supporting a rotating body, there are increasing examples of adopting a static pressure gas bearing in order to realize high-speed and high-precision rotation, low noise, low vibration, long life, and the like.

  For example, CT scanners in the field of medical diagnostic imaging have a rotating shaft that carries a radiation source and rotates. For purposes such as 1) increasing the speed of the CT scanner to reduce scan time, 2) obtaining quiet operation of the CT scanner, 3) eliminating wear on the contact area and reducing maintenance. There is an example in which a rotating shaft of a CT scanner is supported by a static pressure gas bearing (for example, see Patent Document 1).

  Patent Document 1 shows a structure in which a rotating shaft is supported by a plurality of static pressure gas bearing pads from a non-rotating portion for the above purpose. Here, the radial bearing pad supports the polished outer peripheral surface of the outer side of the rotating shaft, and the axial bearing pad supports the flat outer peripheral surface on the front side and the opposite side of the rotating shaft.

A radial ball stud is installed behind the radial bearing pad (on the opposite side to the rotating shaft), and a spring element is provided between the radial bearing pad and the ball stud. The radial bearing pad is disposed in the vicinity of the outer periphery of the rotating shaft, and is held at a predetermined position by a radial ball stud. That is, the radial ball stud is tightened from the back to the desired tension in the radial direction of the rotating shaft via the spring element, and the radial position of the radial bearing pad is adjusted by adjusting the radial ball stud.
Special table 2004-528113 gazette

  In Patent Document 1, the adjustment direction of the ball stud is a direction of a straight line connecting the rotation center of the rotation shaft and the tip of the ball stud. That is, the direction in which the ball stud moves the radial bearing pad is parallel to the direction connecting the rotation center of the rotating shaft and the tip of the ball stud. For this reason, the adjustment amount of the position of the ball stud determines the position of the radial bearing pad arranged ahead as it is relative to the rotating shaft, that is, the amount of the bearing gap (gap between the radial bearing pad and the rotating shaft).

  However, since this bearing gap is small (usually 1 mm or less), in order to adjust the amount of the bearing gap, a fine adjustment of the ball stud is required. In particular, in the use state of the rotating device disclosed in Patent Document 1, that is, in the state where the axial direction of the rotating body is arranged in a substantially horizontal direction, the radial bearing pad arranged below the rotating shaft has a weight of the rotating shaft. It will hang directly. In this state, it was very difficult to adjust the amount of the bearing gap with a screw attached to the outer periphery of the ball stud behind the pad, and it was difficult to adjust to the ideal gap.

  Therefore, a main object of the present invention is to provide a static pressure gas bearing and a rotating device that facilitate adjustment of a gap between the rotating body and the radial bearing pad.

  A static pressure gas bearing according to the present invention is a static pressure gas bearing that supports a rotating body, a radial bearing pad that supports the rotating body in a radial direction, a moving member that moves the radial bearing pad, and a moving member And a coupling portion that couples the radial bearing pad in a swingable manner. The direction in which the moving member moves the radial bearing pad intersects the direction connecting the rotation center of the rotating body and the coupling portion.

  In this case, the amount of change in the distance between the rotation center of the rotating body and the coupling portion, that is, the amount of change in the bearing gap can be reduced with respect to the movement adjustment amount by which the moving member moves the radial bearing pad. That is, since the movement adjustment amount of the radial bearing pad is large with respect to the change amount of the bearing gap, the fine adjustment of the bearing gap can be accurately performed.

  If the direction in which the moving member moves the radial bearing pad is perpendicular to or near the direction connecting the rotation center of the rotating body and the coupling portion, the movement adjustment of the radial bearing pad with respect to the amount of change in the bearing gap This is preferable because the amount can be further increased. For example, the angle formed between the direction in which the moving member moves the radial bearing pad and the direction connecting the rotation center of the rotating body and the coupling portion is preferably in the range of 90 ° ± 20 °, preferably 90 ° ± 10 °. If it is a range, it is more preferable. In order to adjust the bearing clearance (usually 1mm or less), the radial bearing pad is transferred using a feed screw in this configuration, but the thread pitch of the feed screw (distance between two adjacent threads) is usually 1mm. Degree. When the angle between the direction in which the moving member moves the radial bearing pad and the direction connecting the rotation center of the rotating body and the coupling portion is in the range of 90 ° ± 20 °, the radial bearing pad The ratio of the movement adjustment amount is 5 or more. Therefore, it is possible to perform a highly accurate adjustment in which the movement adjustment amount of the radial bearing gap is less than 0.2 mm by one rotation of the feed screw. In addition, when the angle is in the range of 90 ° ± 10 °, the ratio can be set to 10 or more, so that the movement adjustment amount is less than 0.1 mm by one rotation of the feed screw, and a more accurate adjustment is possible.

  In order to increase the movement adjustment amount of the radial bearing pad with respect to the amount of change in the bearing gap, the angle formed by the direction in which the moving member moves the radial bearing pad and the direction connecting the rotation center of the rotating body and the coupling portion is Any configuration that changes with the movement of the radial bearing pad may be used. With such a configuration, the moving direction of the radial bearing pad may be linear or curved. However, if the angle is always 90 °, the bearing gap cannot be changed. For example, when the radial bearing pad moves along a curve having the same curvature as that of the rotating body, the bearing gap does not change even if the radial bearing pad moves. That is, the configuration in which the angle is always 90 ° should be excluded.

  In the static pressure gas bearing, preferably, the moving member includes a ball stud having a spherical tip. A concave portion is formed in a portion of the radial bearing pad that does not face the rotating body. The coupling portion is configured by inserting the tip of the ball stud into the recess.

  In this case, the radial bearing pad and the rotating body are coupled via a spherical body at the tip of the ball stud. The radial bearing pad is supported by a ball stud so as to be freely tiltable with respect to the moving member. Therefore, the radial bearing pad can move in the circumferential direction of the rotating body while changing the inclination with respect to the moving member in accordance with the shape of the portion of the rotating body facing the radial bearing pad.

  Further, the coupling portion may be constituted by a hinge portion that allows the radial bearing pad to swing only in the circumferential direction of the rotating body. In this case, the radial bearing pad and the rotating body are coupled via a hinge portion. The radial bearing pad is supported by the hinge portion so as to be freely tiltable with respect to the moving member in the circumferential direction of the rotating body. Therefore, the radial bearing pad can move in the circumferential direction of the rotating body while changing the inclination with respect to the moving member in accordance with the shape of the portion of the rotating body facing the radial bearing pad.

  If the coupling portion is constituted by a hinge portion, the direction in which the radial bearing pad can tilt with respect to the moving member is limited to the movable direction of the hinge portion. If the moving direction of the hinge portion is arranged so as to match the circumferential direction of the rotating body, the radial bearing pad can be prevented from being inclined in the axial direction of the rotating body. That is, if the coupling portion is constituted by a hinge portion, there is no need to provide a stopper plate or the like for regulating the inclination of the radial bearing pad in the axial direction of the rotating body. Therefore, the static pressure gas bearing can be configured more simply.

  In the static pressure gas bearing, preferably, the moving member is a linear motion guide, and the radial bearing pad is moved by a reciprocating linear motion of the linear motion guide. In this case, the moving member performs a reciprocating linear motion. Therefore, the angle formed by the moving direction of the radial bearing pad and the direction connecting the rotation center of the rotating body and the coupling portion changes with the movement of the radial bearing pad. Therefore, the amount of the bearing gap changes with the movement of the radial bearing pad. Since the movement adjustment amount of the radial bearing pad is larger than the change amount of the bearing gap, the fine adjustment of the bearing gap can be performed by moving the radial bearing pad.

  The rotating device according to the present invention includes a rotating body. Further, the rotating device includes any one of the plurality of static pressure gas bearings described above that supports the rotating body in the radial direction. In this case, the amount of change in the distance between the rotation center of the rotating body and the coupling portion, that is, the amount of change in the bearing gap is reduced with respect to the movement adjustment amount by which the moving member of the static pressure gas bearing moves the radial bearing pad. be able to. That is, since the movement adjustment amount of the radial bearing pad is larger than the change amount of the bearing gap, the fine amount of the bearing gap of the rotating body can be adjusted more accurately.

  Preferably, the static pressure gas bearing is arranged so as to be symmetric with respect to a vertical plane passing through the rotation center of the rotating body. In this case, the rotating body can be supported more stably in the radial direction by the static pressure gas bearing.

  According to the static pressure gas bearing of the present invention, it is possible to easily adjust the gap between the rotating body and the radial bearing pad.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
1 is a partial cross-sectional schematic view showing the configuration of a static pressure gas bearing according to Embodiment 1 of the present invention. As shown in FIG. 1, the static pressure gas bearing includes a radial bearing pad 3 that supports the outer peripheral surface 2c of the rotating shaft in the pad bearing portion 3a in the radial direction of the rotating shaft. The surface facing the outer peripheral surface 2c of the pad bearing portion 3a has the same curvature as the outer peripheral surface 2c or a larger curvature by the bearing gap. A recess 3c is formed on the opposite side of the radial bearing pad 3 from the side where the pad bearing portion 3a facing the outer peripheral surface 2c of the rotating shaft is provided. The recess 3c is formed in a spherical shape. In addition, the recessed part 3c may be formed so that it may have a tapered surface.

  A plurality of air supply holes 3g are formed in the pad bearing portion 3a. The air supply hole 3g is narrowed toward the end on the side facing the outer peripheral surface 2c. That is, the air supply hole 3g is formed to have a smaller diameter as the air supply hole 3g approaches the opening to the outside of the air supply hole 3g. An air supply groove 3f is formed in the radial bearing pad 3 so as to communicate with the plurality of air supply holes 3g, and an air supply port 3e is formed so as to communicate with the air supply groove 3f. Compressed air is supplied from an external compressed air source (not shown) to the air supply port 3e, guided to the air supply groove 3f, and further toward the outer peripheral surface 2c of the rotating shaft from the narrowed opening of the air supply hole 3g. A jet, static pressure gas journal bearing is formed.

  A spherical tip 4a of the ball stud 4 is inserted into the recess 3c to form a coupling part. The base of the ball stud 4 is fixed to the upper plate 4b. The upper plate 4b is mounted and fixed on the fine movement table 4c. The fine motion table 4c is incorporated on a linear motion guide 1c as a moving member fixed on the table base 1b so as to be movable along the linear motion guide 1c.

  A screw end joining member 4d is attached to the upper plate 4b. On the table base 1b, a feed screw support 5b having a screw hole formed in the upper part thereof is installed. A feed screw 5a is inserted into the screw hole. The amount (feed amount) by which the feed screw 5a is inserted into the screw hole can be arbitrarily adjusted. The feed screw 5a having the feed amount adjusted and disposed at an appropriate position is obtained by, for example, a method in which a flange nut screwed to the feed screw 5a as a fixing member is tightened toward the feed screw column 5b. Its position is fixed.

  The front end surface of the feed screw 5a is in contact with the screw end joining member 4d. By rotating the feed screw 5a and adjusting the feed amount, the fine movement table 4c can be reciprocated linearly. When the upper plate 4b is moved by the reciprocating linear movement of the fine movement table 4c, the ball stud 4 fixed to the upper plate 4b is also moved, and the radial bearing pad 3 is also moved accordingly. The movement direction of the radial bearing pad 3 (that is, the movement direction of the fine movement table 4c) connects the rotation center of the rotary shaft 2 and the coupling portion formed by inserting the tip end portion 4a of the ball stud 4 into the recess 3c. It intersects with the direction. Since the radial bearing pad 3 moves in a straight line, the angle formed between the moving direction of the radial bearing pad 3 and the direction connecting the rotation center of the rotating shaft 2 and the coupling portion is accompanied by the movement of the radial bearing pad 3. Change.

  FIG. 2 is a diagram for explaining a change amount of the bearing gap with respect to a movement adjustment amount by which the moving member moves the radial bearing pad. With reference to FIG. 2, the relationship between the movement adjustment amount and the change amount of the bearing gap will be described. In FIG. 2, the rotation center of the rotation axis is O, the tip position of the ball stud is A, the tangent of the rotation axis at point A is h, and the line inclined at a predetermined angle θ with respect to the tangent h is i. A normal to h is X, a line inclined by an angle θ from the line X is Y, and an intersection of the line Y and the line i is B. Also, let C be the intersection of line Y and circle Z centered on point O and having a radius r from point O to point A.

  Consider a case where the ball stud tip position is adjusted to move straight along a line i from point A to point B. The distance between the ball stud tip position and the point O is r before the movement, but becomes a distance OB after the movement, and is shortened before and after the movement by the distance BC. The bearing gap changes by the amount of the distance BC. At this time, the ratio of the distance BC to the movement adjustment amount AB is BC / AB = r (1-cos θ) / rsin θ.

  For example, when θ = 10 °, BC / AB = 0.09. When θ = 20 °, BC / AB = 0.18. That is, the change amount BC of the bearing gap is significantly smaller than the movement adjustment amount AB.

  Therefore, as shown in FIG. 1, when the radial bearing pad 3 moves along with the reciprocating linear movement of the fine movement table 4c, the radial bearing pad 3 also moves in the radial direction of the rotating shaft. The radial movement amount of the rotary shaft with respect to the movement adjustment amount of the radial bearing pad 3 is reduced at a predetermined ratio based on the movement adjustment amount of the radial bearing pad 3. Thereby, the minute movement amount of the radial bearing pad 3 in the radial direction of the rotating shaft can be easily adjusted. That is, the fine adjustment of the bearing gap can be performed with higher accuracy.

  By forming the static pressure gas bearing by ejecting compressed gas toward the outer peripheral surface 2c of the rotating shaft, a force for supporting the rotating shaft is generated. At this time, the radial bearing pad 3 is loaded with a reaction force (bearing reaction force) for supporting the rotating shaft. In the radial bearing pad 3, the pad bearing portion 3 a is pressed against the tip end portion 4 a of the ball stud 4 by the bearing reaction force. In addition, since the spherical tip 4a of the ball stud 4 is inserted into the concave portion 3c having a spherical surface (or tapered surface), the radial bearing pad 3 is free from the linear motion guide 1c. Supported to tilt. Therefore, the radial bearing pad 3 moves linearly with the movement of the fine movement table 4c, and automatically tilts with respect to the linear motion guide 1c in accordance with the shape of the outer peripheral surface 2c of the rotating body facing the radial bearing pad 3. It is possible to move in the circumferential direction of the rotating shaft while adjusting the angle.

  Next, a rotating device including the above-described static pressure gas bearing will be described. FIG. 3 is a schematic diagram showing the configuration of the rotating device. As shown in FIG. 3, the rotating device includes a non-rotating portion 1 and a rotating shaft 2 as a rotating body. At the four corners of the non-rotating part 1, table columns 1a are installed. A plurality of static pressure gas bearings that support the rotary shaft 2 in the radial direction are arranged on a linear guide 1c fixed on a table base 1b installed on a table column 1a installed at an inclination. Built in so that it can move along.

  The rotating shaft 2 includes a protruding portion protruding toward the front side of the figure, and the tip surface 2a and the outer peripheral surface 2c constitute a protruding portion. The protruding portion has a cylindrical shape extending in the axial direction of the rotating shaft 2. The base portion of the protruding portion is fixed to an annular flange portion 2b formed in a flange shape. The rotating shaft 2 is comprised by the protrusion part and the flange part 2b. When a load is mounted on the rotary shaft 2, the load is mounted on the distal end surface 2 a of the protruding portion. For example, when a rotating device is used as the CT scanner, a radiation source, a radiation detector, a power supply device, and the like are mounted on the distal end surface 2a of the protruding portion.

  The rotating shaft 2 is supported by a plurality of static pressure gas bearings fixed to the non-rotating portion 1. The static pressure gas bearing supports the rotating shaft 2 in the radial direction on the outer peripheral surface 2c of the protruding portion. As shown in FIG. 3, the static pressure gas bearings are arranged at five locations on the outer peripheral surface 2 c of the rotary shaft 2, and three static pressure gas bearings are provided below the rotary shaft 2 and two above it. Has been placed. Thus, by arranging more static pressure gas bearings in the direction in which gravity by the load on the rotation shaft 2 and the load on the rotation shaft 2 acts, the minimum number of static pressure gas bearings allows efficient rotation of the rotation shaft 2. The load can be supported. The minimum number of static pressure gas bearings can be similarly adjusted not only by adjusting the arrangement of the static pressure gas bearings but also by adjusting other specifications of the static pressure gas bearings such as the diameter and number of the air supply holes 3g. As a result, an effect of efficiently supporting the load of the rotary shaft 2 can be obtained.

  The rotating shaft 2 is supported in the axial direction by a static pressure gas bearing including a plurality of axial bearing pads 6 in the flange portion 2b. A plurality of axial bearing pads 6 are respectively provided on the front surface of the flange portion 2b shown in FIG. 3 and on the opposite surface of the flange portion 2b (not shown) so as to face the flange portion 2b. Similarly to the radial bearing pad 3 described above, the axial bearing pad 6 is also supplied with compressed air, and the supplied compressed air is jetted toward both surfaces of the flange portion 2b of the rotary shaft 2 to generate a static pressure gas thrust. A bearing is formed. The rotary shaft 2 is supported in the axial direction by a static pressure gas thrust bearing. Thus, the rotary shaft 2 is supported in a non-contact manner in the axial direction and the radial direction by the static pressure gas bearing. Therefore, quiet high speed operation of the rotating shaft 2 is possible. Moreover, since it is non-contact, there is no wear part and it becomes maintenance-free.

  In the static pressure gas bearing that supports the rotary shaft 2 in the radial direction, the linear motion guide 1c as the moving member moves between the radial center of the rotary shaft 2 and the ball stud 4 with respect to the movement adjustment amount for moving the radial bearing pad 3. The amount by which the distance changes, that is, the amount of change in the bearing gap can be reduced. That is, since the movement adjustment amount of the radial bearing pad 3 is larger than the change amount of the bearing gap, the fine adjustment of the bearing gap in the radial direction of the rotary shaft 2 can be performed with higher accuracy.

  Further, the radial bearing pads 3 and 13 are disposed so as to be symmetric with respect to a vertical plane passing through the rotation center of the rotary shaft 2 (that is, a plane passing through the direction of gravity). Similarly, the radial bearing pads 23 and 33 are arranged so as to be symmetric with respect to a vertical plane passing through the rotation center of the rotary shaft 2. In FIG. 3, the vertical plane is indicated by a one-dot chain line in the vertical direction of the figure. Since the static pressure gas bearing is thus arranged, the rotary shaft 2 is supported more stably in the radial direction. Therefore, the rotating shaft 2 is supported by the static pressure expectation bearing so that the center of rotation during the rotational movement can be prevented.

  In the configuration of the first embodiment, the feed screw 5a is in contact with the screw end joining member 4d, and the feed screw 5a and the fine movement table 4c are always moved integrally, but an elastic member is interposed. It is good also as a structure. For example, an elastic member such as a spring may be interposed between the feed screw 5a and the screw end joining member 4d, or between the screw support 5b and the fine movement table 4c. In this way, the vibration associated with the rotation of the rotating shaft can be absorbed by the vibration of the fine movement table 4c, and a quiet rotation of the rotating device can be realized.

(Embodiment 2)
FIG. 4 is a partial cross-sectional schematic diagram showing the configuration of the static pressure gas bearing of the second embodiment. The static pressure gas bearing of the second embodiment and the static pressure gas bearing of the first embodiment described above basically have the same configuration. However, the second embodiment is different from the first embodiment in that the configuration of the coupling portion that couples the radial bearing pad 3 to the linear motion guide 1c as the moving member is the configuration shown in FIG. Is different. Specifically, the coupling portion is constituted by the hinge portion 7. The hinge portion 7 is arranged so that the radial bearing pad 3 can be moved only in the circumferential direction of the outer peripheral surface 2c.

  That is, the radial bearing pad 3 is supported by the hinge portion 7 so as to be freely tiltable with respect to the linear motion guide 1c in the circumferential direction of the rotating body. Therefore, the radial bearing pad 3 can move in the circumferential direction of the rotating body while changing the inclination with respect to the linear motion guide 1c in accordance with the shape of the outer peripheral surface 2c of the rotating body facing the radial bearing pad 3. .

  If the coupling portion is constituted by the hinge portion 7, the direction in which the radial bearing pad 3 can be inclined with respect to the linear motion guide 1 c is limited to the movable direction of the hinge portion 7. If the movable part of the hinge part 7 is arranged so as to match the circumferential direction of the rotating body, the radial bearing pad 3 can be prevented from being inclined in the axial direction of the rotating body. That is, since it is not necessary to provide a member (for example, a stopper plate) for restricting the inclination of the radial bearing pad 3 in the axial direction of the rotating body, the static pressure gas bearing can be configured more simply.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

FIG. 3 is a partial cross-sectional schematic diagram showing the configuration of the static pressure gas bearing of the first embodiment. It is a figure which shows the variation | change_quantity of the bearing clearance with respect to the movement adjustment amount of a moving member. It is a schematic diagram which shows the structure of a rotation apparatus. FIG. 4 is a partial cross-sectional schematic diagram showing a configuration of a static pressure gas bearing of a second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Non-rotating part, 1a Table support | pillar, 1b Table base, 1c Linear motion guide, 2 Rotating shaft, 2a Tip surface, 2b Flange part, 2c Outer peripheral surface, 3, 13, 23, 33 Radial bearing pad, 3a Pad bearing part, 3c recess, 3e air supply port, 3f air supply groove, 3g air supply hole, 4 ball stud, 4a tip, 4b upper plate, 4c fine movement table, 4d screw end joint member, 5a feed screw, 5b screw support, 6 axial bearing pad 7 Hinge part.

Claims (6)

A hydrostatic gas bearing for supporting a rotating body,
A radial bearing pad for supporting the rotating body in a radial direction;
A moving member for moving the radial bearing pad;
A coupling portion that pivotably couples the radial bearing pad to the moving member;
A static pressure gas bearing in which a direction in which the moving member moves the radial bearing pad intersects with a direction connecting the rotation center of the rotating body and the coupling portion. The moving member includes a ball stud having a spherical tip,
A concave portion is formed in a portion of the radial bearing pad not facing the rotating body,
The static pressure gas bearing according to claim 1, wherein the coupling portion is configured by inserting the tip end of the ball stud into the concave portion.   The static pressure gas bearing according to claim 1, wherein the coupling portion is configured by a hinge portion that allows the radial bearing pad to swing only in a circumferential direction of the rotating body. The moving member is a linear motion guide,
The static pressure gas bearing according to any one of claims 1 to 3, wherein the radial bearing pad is moved by a reciprocating linear motion of the linear motion guide. A rotating body,
A rotating device comprising a plurality of static pressure gas bearings according to claim 1, wherein the rotating body is supported in a radial direction.   The rotating device according to claim 5, wherein the static pressure gas bearing is arranged so as to be symmetric with respect to a vertical plane passing through a rotation center of the rotating body.

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