JP5267470B2 - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator hardly transmitting microvibration to an object mounted on a main bearing even when the main bearing is moved at high speed and suddenly accelerated or decelerated. <P>SOLUTION: The actuator includes: a driving pulley 1; a driven pulley 2; an endless belt 3 stretched between both pulleys 1, 2; a guide rail 4; the main bearing 5 connected to the endless belt 3 and linearly moving along the guide rail 4; a counter guide rail 6; and a counter bearing 7 connected to the endless belt 3 and linearly moving along the counter guide rail. The main bearing 5 is formed by connecting three axially arranged bearing members 5A, 5B, 5C by a connecting member 8. Out of these bearing members 5A, 5B, 5C, the bearing member 5B is a belt connection bearing member connected to the endless belt 3, and the bearing members 5A, 5C are mounted object bearing members mounted with the mounted object. The connecting member 8 is deformable in directions other than the axial direction without being deformed in the axial direction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an actuator.

For example, a manufacturing apparatus is provided with a linear guide bearing device for moving a workpiece, and Patent Documents 1 and 2 disclose actuators suitably used for such a linear guide bearing device.
The actuators disclosed in Patent Documents 1 and 2 include a driving pulley that is rotationally driven by a driving device, a driven pulley that is rotatably supported, an endless belt that is spanned between the driving pulley and the driven pulley, and a workpiece. Main bearings that move linearly with mounted items such as, guide rails that guide the linear movement of the main bearings, counter bearings that function as counterweights for the main bearings, and counter guide rails that guide the linear movement of the counter bearings And. The main bearing and the counter bearing are connected to an endless belt, and the counter bearing is connected to the side opposite to the side on which the main bearing is attached with the two pulleys in between.
In such an actuator, by moving the main bearing and the counter bearing in the opposite directions, the reaction force of the main bearing that occurs during acceleration, deceleration, etc. is suppressed, thereby suppressing vibrations. Yes.

JP 2008-101642 A JP 2001-248703 A

However, even if the conventional actuator as described above is suppressed as described above, if the main bearing moves at a high speed and is accelerated or decelerated rapidly, there is a possibility that a slight vibration may occur. there were. Therefore, the motion accuracy of the main bearing that moves linearly may be slightly reduced.
In normal applications, even if the motion accuracy is slightly reduced, there are often no significant adverse effects. However, in the case of high-precision actuators, the slight vibration transmitted to the main bearing via the endless belt has an adverse effect on the load. There was a risk of affecting. Therefore, further improvement of vibration suppression has been demanded.
Therefore, the present invention solves the problems of the prior art as described above, and even when the main bearing moves at a high speed and suddenly accelerates or decelerates, fine vibrations are transmitted to the load mounted on the main bearing. It is an object to provide an actuator that is difficult to perform.

  In order to solve the above problems, the present invention has the following configuration. That is, the actuator of the present invention is driven between a driving pulley that is driven to rotate by a driving device, a driven pulley that is rotatably supported, and between the driving pulley and the driven pulley. An endless belt that rotates in an axial direction, a guide rail that extends in the axial direction, and a main bearing that is connected to the endless belt and linearly moves in the axial direction along the guide rail as the endless belt rotates. In the actuator for mounting a load on a main bearing and moving it linearly, the main bearing is formed by connecting three or more bearing members arranged in the axial direction by connecting members, and some of these bearing members are endless. A belt connection bearing member connected to the belt, the other part being a load bearing member for mounting the load, and the connecting member changing in the axial direction; In the direction other than the axial direction without, characterized in that is deformable.

  With such a configuration, fine vibration from the endless belt is transmitted to the belt connecting bearing member, but is not directly transmitted to the load bearing member. Although the minute vibration transmitted to the belt connecting bearing member is transmitted to the load bearing member via the connecting member, the minute vibration is buffered by the deformation of the deformable connecting member as described above. Micro vibration transmitted to the member is greatly suppressed. Therefore, even when the main bearing moves at a high speed and is accelerated or decelerated rapidly, the slight vibration transmitted from the endless belt to the load is small, and therefore the fine vibration has an adverse effect on the load mounted on the main bearing. There is little fear.

In the actuator of the present invention as described above, the counter guide rail extending in the axial direction and the side to which the main bearing is connected are connected to the endless belt on the opposite side across the pulleys, and the endless belt It is preferable to further include a counter bearing that linearly moves along the counter guide rail in the axial direction along with the rotation.
In the actuator of the present invention as described above, it is preferable that the endless belt and the main bearing are connected at the center of gravity of the main bearing.

  With such a configuration, generation of useless moments in the main bearing due to the driving force of the endless belt during acceleration / deceleration is suppressed, and therefore vibration of the main bearing is further suppressed. If the load is mounted on the main bearing, the position of the center of gravity of the main bearing on which the load is mounted (that is, the position of the center of gravity of the combination of the main bearing and the load) ".

Furthermore, in the actuator of the present invention as described above, it is preferable that the guide rail has a substantially U-shaped cross section, and at least a part of the endless belt is disposed in the recess of the guide rail.
With such a configuration, it is possible to prevent the dust generated from the endless belt from adhering to the load so that the concave portion of the guide rail does not face the load.

  Furthermore, it is preferable that the connecting member is a member having a round shaft shape or a flat plate shape.

  In the actuator of the present invention, even when the main bearing moves at a high speed and is rapidly accelerated or decelerated, it is difficult for fine vibrations to be transmitted to an object mounted on the main bearing.

It is sectional drawing which shows the structure of a linear guide bearing apparatus provided with the actuator which concerns on this embodiment. It is a top view of the linear guide bearing apparatus of FIG. It is a side view of the linear guide bearing apparatus of FIG. It is AA sectional drawing of the linear guide bearing apparatus of FIG. It is BB sectional drawing of the linear guide bearing apparatus of FIG. It is sectional drawing which shows the structure of a linear guide bearing apparatus provided with the actuator of a modification. It is sectional drawing of the linear guide bearing apparatus of FIG.

  Embodiments of an actuator according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view (a cross-sectional view taken along a plane orthogonal to the axial direction) showing a structure of a linear guide bearing device including an actuator according to the present embodiment, and FIG. 2 is a linear guide bearing device of FIG. FIG. 3 is a side view of the linear guide bearing device of FIG. 1, FIG. 4 is an AA sectional view of the linear guide bearing device of FIG. 3, and FIG. 5 is a BB of the linear guide bearing device of FIG. It is sectional drawing.

  The actuator according to the present embodiment includes a drive pulley 1 that is rotationally driven by a motor 10, a driven pulley 2 that is rotatably supported, and an annular endless belt that is stretched between the drive pulley 1 and the driven pulley 2. 3, a guide rail 4 that extends in the axial direction, a main bearing 5 that moves linearly in the axial direction along the guide rail 4 as the endless belt 3 rotates, a counter guide rail 6 that extends in the axial direction, and the endless belt 3 And a counter bearing 7 that moves linearly in the axial direction along the counter guide rail 6.

  Below, the structure of a linear guide bearing apparatus provided with the actuator which concerns on this embodiment is demonstrated in detail. Rail support plates 12 and 13 are fixed to both ends of the guide rail 4 which also functions as a frame, as shown in FIGS. Round shaft-shaped counter guide rails 6 and 6 are attached in parallel to the guide rail 4 so as to be spanned between the rail support plates 12 and 13.

  2 to 4, the motor 10 is attached to the right rail support plate 13. The rotating shaft 10a of the motor 10 extends in a direction that is horizontal and orthogonal to the axis (axial direction) of the guide rail 4, and a driving pulley 1 is attached to the tip thereof. On the other hand, a pulley housing 14 that rotatably supports the driven pulley 2 is attached to the left rail support plate 12 in FIGS.

  An endless belt 3 is stretched between the drive pulley 1 and the driven pulley 2 in a direction (axial direction) along the guide rail 4. Therefore, the rail support plates 12 and 13 have through holes (not shown) through which the endless belt 3 is inserted. A plurality of teeth (not shown) arranged in the circumferential direction are formed on the surface (inner side surface) of the endless belt 3, and teeth (not shown) formed on the outer peripheral surfaces of the driving pulley 1 and the driven pulley 2. Z)). Therefore, the endless belt 3 is rotated by the rotation of the drive pulley 1.

  Further, since the main bearing 5 is connected to the endless belt 3 and is engaged with the guide rail 4, the main bearing 5 is guided by the guide rail 4 along the rotation of the endless belt 3 and linearly extends in the axial direction. It is movable. On the other hand, since the counter bearing 7 is connected to the endless belt 3 and engaged with the counter guide rail 6, the counter bearing 7 is guided by the counter guide rail 6 along the axial direction as the endless belt 3 rotates. It can move linearly (in the opposite direction to the main bearing 5). The counter bearing 7 is connected to the endless belt 3 on the side opposite to the side where the main bearing 5 is connected with both pulleys 1 and 2 therebetween.

  Here, the main bearing 5 and the guide rail 4 will be described in more detail. The shape of the guide rail 4 is not particularly limited, but is preferably substantially U-shaped as shown in FIG. That is, the guide rail 4 is composed of a belt-like bottom wall 21 and a pair of side walls 22, 22 vertically provided from both sides of the bottom wall 21. It has a letter shape.

  On the other hand, the main bearing 5 is formed by connecting three or more (three in the present embodiment) bearing members 5A, 5B, 5C arranged in the axial direction by a connecting member 8. And each bearing member 5A, 5B, 5C is substantially the same shape. The shape of the bearing members 5A, 5B, and 5C is not particularly limited as long as it is a shape that engages with the guide rail 4, but when the guide rail 4 has a substantially U-shaped cross section as described above, the guide It is a square cylindrical member that can contain the rail 4.

  That is, each bearing member 5A, 5B, 5C includes a bottom plate 31 that faces the bottom wall 21 of the guide rail 4, side plates 32 and 32 that face the side surfaces of the side walls 22 and 22 of the guide rail 4, and the guide rail 4 respectively. This is a rectangular tube-shaped member formed by connecting the top plates 33 facing the upper surfaces of the side walls 22 and 22, respectively. Thus, the main bearing 5 is engaged with the guide rail 4 so as to enclose the guide rail 4.

  Of the three bearing members 5A, 5B, 5C, the axially central bearing member 5B is a belt connecting bearing member for connecting the endless belt 3 (no load is mounted), and both axial bearing members. 5A and 5C are load bearing members for loading the load (not directly connected to the endless belt 3). The mounted object may be mounted anywhere on the bearing members 5A and 5C. However, when the mass balance of the main bearing 5 is lost due to the mounting of the mounted object, a balance weight that cancels the moment of the mounted object may be mounted. In the example of FIG. 1, since the load is mounted on the left side surface of the main bearing 5, the balance weight is mounted on the right side surface.

  The connecting member 8 that connects the bearing members 5A, 5B, and 5C is a round shaft member. The connecting member 8 is a metal member, for example, and is not deformable in the axial direction, and can be deformed in directions other than the axial direction. Since the mounting portion 15 in which a circular hole is formed is attached to each bearing member 5A, 5B, 5C with a bolt or the like, by inserting the connecting member 8 into the hole of the mounting portion 15, the bearing member 5A, 5B and 5C are connected. In addition, if the slit is provided in the attachment part 15 like FIG. 1, the connection member 8 can be fastened together by tightening a volt | bolt.

  The endless belt 3 and the main bearing 5 (belt connection bearing member) are connected by a fixture 16. That is, a part of the endless belt 3 is fixed to the bearing member 5 </ b> B via the fixing tool 16. More specifically, a square cylindrical fixture 16 is attached to the inner surface of the top plate 33 of the bearing member 5B by a conventional fixing means such as a bolt (not shown), and is endlessly attached to the inner surface of the fixture 16. The belt 3 is fixed by conventional fixing means such as bolts and adhesion.

  The connection position of the endless belt 3 and the fixture 16 is arranged at a position lower than the upper ends of the side walls 22 and 22 of the guide rail 4, that is, in the recess of the guide rail 4. In this way, by making the connection position of the endless belt 3 and the fixture 16 coincide with the position of the center of gravity of the main bearing 5, when the main bearing 5 is driven by the endless belt 3, an unnecessary moment is applied to the main bearing 5. Occurrence is suppressed.

  Further, on the inner surfaces of the bearing members 5A, 5B, and 5C facing the guide rails 4 of the bottom plate 31, the side plates 32 and 32, and the top plate 33, jet holes for jetting gas are provided. That is, a gas bearing is formed between the main bearing 5 and the guide rail 4. The type of gas is not particularly limited, but air is preferred. Moreover, you may install the jet nozzle which jets gas on the outer surface of the guide rail 4 contrary to this embodiment. In the present embodiment, as shown in FIG. 1, a plate-like static pressure pad SP formed of graphite porous is arranged as a jet outlet.

  Since the compressed air is supplied to the static pressure pad SP from an air source (not shown), the main bearing 5 is applied to the guide rail 4 by the pressure of the air ejected from the static pressure pad SP toward the outer surface of the guide rail 4. Slightly separated. Therefore, the main bearing 5 can move with little friction. Instead of providing the gas bearing, a slide bearing or a rolling bearing may be provided between the main bearing 5 and the guide rail 4.

  Next, the counter bearing 7 and the counter guide rail 6 will be described in detail. The counter guide rails 6 and 6 are intended to guide the counter bearings 7 and 7 for achieving a mass balance with respect to the main bearing 5, so that the accuracy is not required so much. Therefore, the round shaft can be manufactured at a relatively low cost. The counter bearings 7 and 7 have cylindrical holes through which the counter guide rails 6 and 6 are inserted.

  However, if there is one counter guide rail 6, the counter bearing 7 may rotate around the counter guide rail 6. Therefore, a plurality of counter guide rails 6 (two in the present embodiment) are arranged in parallel, and counter bearings 7 and 7 engaged with the counter guide rails 6 are connected by a substantially plate-like fixing member 17, respectively. It is preferable to limit the movement of 7 to only movement in the axial direction.

  As means for balancing the mass with the main bearing 5, there is means for mounting another balance weight on the counter bearings 7, 7. For example, the main bearing 5 is made of an aluminum alloy having a small specific gravity, and the counter bearing 7, On the other hand, a means for designing the balance of mass is also preferable, for example, 7 is made of a ferrous material having a large specific gravity. By doing so, it is possible to balance the mass with the main bearing 5 without adding a balance weight. If the mass is balanced, the counter bearings 7 and 7 may be small because the reaction force during acceleration on the counter bearings 7 and 7 is not generated as a moment load.

  The endless belt 3 and the counter bearings 7 and 7 are connected by a fixing member 17. That is, a part of the endless belt 3 is fixed to the counter bearings 7 and 7 via the fixing tool 17. More specifically, both end portions of the plate-shaped fixture 17 bent as shown in FIG. 1 are attached to the counter bearings 7 and 7 by conventional fixing means such as bolts, and are attached to the central portion of the fixture 17. The endless belt 3 is fixed by conventional fixing means such as bolts and adhesion.

  The fixture 17 is bent so that the central portion is lowered by one step, and the endless belt 3 is fixed to the lowered central portion. As described above, when the end bearing belt 3 and the fixture 17 are connected to the center of gravity of the counter bearings 7 and 7 so that the counter bearings 7 and 7 are driven by the endless belt 3, 7 is prevented from generating unnecessary moments.

  In addition, on the inner surfaces of the cylindrical holes of the counter bearings 7 and 7, an outlet for ejecting gas is provided. That is, a gas bearing is formed between the counter bearings 7 and 7 and the counter guide rails 6 and 6. The type of gas is not particularly limited, but air is preferred. In contrast to the present embodiment, a jet outlet for jetting gas may be provided on the outer surface of the counter guide rails 6 and 6. In the present embodiment, cylindrical static pressure pads SP, SP formed of graphite porous are arranged as jet nozzles on the inner surfaces of the cylindrical holes of the counter bearings 7, 7.

  Since the compressed air is supplied to the static pressure pads SP and SP from an air source (not shown), the counter guide is generated by the pressure of the air ejected from the static pressure pads SP and SP toward the outer surfaces of the counter guide rails 6 and 6. The counter bearings 7 and 7 are slightly separated from the rails 6 and 6. Therefore, the counter bearings 7 and 7 can move with almost no friction. Instead of providing the gas bearing, a slide bearing or a rolling bearing may be provided between the counter bearings 7 and 7 and the counter guide rails 6 and 6.

  Next, operation | movement of a linear guide bearing apparatus provided with the actuator which concerns on this embodiment is demonstrated. An inspection camera (not shown) is mounted on the lower surface of the main bearing 5 (bearing member 5A or 5C). Since the main bearing 5 can move linearly along the guide rail 4, the upper surface of the workpiece W (see FIG. 3) disposed below the main bearing 5 can be scanned by the camera.

  First, the main bearing 5 is kept slightly separated from the guide rail 4 by compressed air supplied to each static pressure pad SP from an air source (not shown), and the counter bearings 6 and 6 are counter bearings. 7 and 7 are kept slightly separated. Here, when the motor 10 drives the drive pulley 1, the main bearing 5 is moved along the guide rail 4 with little friction via the endless belt 3, and the counter bearing 7 is moved along the counter guide rails 6 and 6. 7 are moved almost without friction. Then, by controlling the driving of the driving pulley 1, the main bearing 5 can be reciprocated linearly between both ends of the guide rail 4.

  At this time, the driving reaction force of the main bearing 5 generated during acceleration or deceleration is canceled by the counter bearings 7 and 7 connected to the opposite side of the pulleys 1 and 2 with respect to the side to which the main bearing 5 is connected. Therefore, vibration is suppressed. If the total mass of the main bearing 5 and the load and the mass of the counter bearings 7 and 7 are substantially matched, the drive reaction force can be more effectively offset and vibration can be effectively suppressed.

  Further, in this embodiment, the bearing members 5A and 5C for mounting the load and the bearing member 5B for connecting the endless belt 3 are separate bodies, but the conventional product is an integral body, and the main bearing on which the load is mounted. An endless belt is connected to the drive to transmit the driving force. Therefore, in the conventional product, the vibration from the endless belt is transmitted to the load, and the load may be adversely affected. However, in the present embodiment, the bearing members 5A and 5C for mounting the load and the bearing member 5B for connecting the endless belt 3 are separate, and the vibration from the endless belt 3 is caused by the connecting member 8 for connecting them. Is buffered, the vibration from the endless belt 3 is not easily transmitted to the mounted object.

  More specifically, the vibration from the endless belt 3 is transmitted to the bearing member 5B, but the connecting member 8 is a round shaft-like member, and is not deformed in the axial direction and can be deformed in directions other than the axial direction. Due to the nature, the connecting member 8 is not deformed in the axial direction by the transmitted vibration, and is bent in a direction (radial direction) other than the axial direction. Strictly speaking, the connecting member 8 slightly expands and contracts in the axial direction. However, since the amount of deformation is negligible compared to the bending in the radial direction, it can be said that the connecting member 8 does not substantially deform in the axial direction.

  Therefore, although the vibration in the axial direction of the vibration from the endless belt 3 is slightly transmitted to the bearing members 5A and 5C via the connecting member 8, the vibration in the direction other than the axial direction is buffered by the deformation of the connecting member 8, and the bearing member. It is hardly transmitted to 5A and 5C. As a result, even when the main bearing 5 moves at a high speed and is rapidly accelerated or decelerated, fine vibration of the moving main bearing 5 is suppressed and high straightness is obtained. In addition, since the slight vibration is difficult to be transmitted to the load mounted on the main bearing 5, there is almost no possibility that the load is adversely affected by the vibration from the endless belt 3. And since the connection member 8 is a round shaft-shaped member, even if it bends to any direction if it is radial direction, the characteristic which buffers a vibration is the same, and the ease of buffering vibration changes with the direction of bending. There is no such thing.

  Further, the driving pulley 1 and the driven pulley 2 are the largest dust generation sources of this apparatus, but as a countermeasure, both pulleys 1 and 2 are covered with a cover (see FIG. 2). The inside of the cover is configured to collect dust and exhaust by an exhaust pump (not shown). Thereby, even when the main bearing 5 moves at high speed and is rapidly accelerated or decelerated, the adhesion of foreign matter to the workpiece W is extremely small.

  Further, the guide rail 4 has a substantially U-shaped cross section, and therefore, the outer surfaces of the side walls 22 and 22 and the bottom wall 21 are flat, so that there is an advantage that it is easy to improve processing accuracy (particularly straightness accuracy). Further, the closed lower side of the guide rail 4 can be directed to the workpiece W by disposing the endless belt 3 from the upper side where the guide rail 4 having a substantially U-shaped cross section opens. As a result, the dust generated from the endless belt 3 is suppressed from adhering to the work W, so that it is not necessary to provide a cover on the work W, and the cost can be reduced.

Such a linear guide bearing device can be suitably used in a manufacturing device, an inspection device, a conveying device, and the like. In particular, the linear guide bearing device is used under the condition that the main bearing moves at a high speed and is rapidly accelerated or decelerated. Even if it is operated, it is suitable for various devices that require high-precision linear movement of the main bearing.
In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, in the present embodiment, the main bearing 5 is formed by connecting three bearing members 5A, 5B, and 5C. However, the number of bearing members is not particularly limited as long as the number is three or more. Absent.

  Further, one of the three bearing members 5A, 5B, 5C was a belt connecting bearing member and two were bearing objects bearing members, but the number of these is not particularly limited, There may be a plurality of belt connecting bearing members, or a single bearing member may be mounted. Further, among the three bearing members 5A, 5B, and 5C, the axially central bearing member 5B is the belt connecting bearing member, but the bearing members 5A and 5C other than the axially central may be used as the belt connecting bearing member. The axial position of the belt connecting bearing member among the plurality of bearing members is not particularly limited.

Furthermore, when a round shaft-shaped member is used as the connecting member 8, the outer peripheral surface of the round shaft-shaped member is made of a material having vibration damping properties such as rubber in order to further enhance the property of suppressing vibration. You may cover with the comprised film. The round shaft member may be hollow and filled with rubber or liquid.
Furthermore, in this embodiment, although the example which used the member of the round shaft shape as the connection member 8 was shown, it has the property that it can deform | transform in directions other than an axial direction without deform | transforming in an axial direction. If so, the connecting member 8 is not limited to a round shaft member, and for example, a flat plate member as shown in FIGS. As the flat member, for example, a leaf spring is suitable.

  Since the configuration and the operation are almost the same as the case where a round shaft-like member is used as the connecting member 8, the description of the same part is omitted, but as shown in FIGS. The configured connecting member 8 is fixed to the main bearing 5 by being sandwiched between the plate nut 18 and the top plate 33 of the bearing members 5A, 5B, 5C. A spacer 19 is interposed between the top plate 33 and the connecting member 8. 6 and 7, the same or corresponding parts as those in FIGS. 1 and 5 are denoted by the same reference numerals as those in FIGS.

In the case where the connecting member 8 is a flat plate member, the characteristics of buffering vibration differ depending on the direction of bending, and there are directions in which vibration is easily buffered and directions that are difficult to be buffered. In the case of actually using a linear guide bearing device having an actuator, vibration in the rolling direction is the most problematic, so that deformation is slightly less likely in the yawing direction, so that it can be deformed in the rolling direction and the pitching direction. A flat connecting member 8 is attached. As a result, vibrations in the rolling direction and the pitching direction are sufficiently suppressed.
Further, in the present embodiment, the camera is exemplified as the mounted object to be mounted on the main bearing 5, but the mounted object is not limited to the camera, and various objects, processing devices, and the like are mounted on the main bearing 5. be able to.

DESCRIPTION OF SYMBOLS 1 Drive pulley 2 Driven pulley 3 Endless belt 4 Guide rail 5 Main bearing 5A, 5B, 5C Bearing member 6 Counter guide rail 7 Counter bearing 8 Connecting member 10 Motor

Claims (7)

A driving pulley that is rotationally driven by a driving device; a driven pulley that is rotatably supported; an endless belt that is stretched between the driving pulley and the driven pulley and rotates in accordance with the rotation of the driving pulley; A guide rail extending in a direction, and a main bearing connected to the endless belt and linearly moving in the axial direction along the guide rail as the endless belt rotates, and a load is mounted on the main bearing. For actuators that move linearly,
The main bearing is composed of three or more bearing members arranged in the axial direction by a connecting member, and a part of these bearing members is a belt connecting bearing member connected to the endless belt, and the other part Is a load bearing member for mounting the load, and the connecting member is not deformable in the axial direction and can be deformed in directions other than the axial direction. 2. The actuator according to claim 1 , wherein the guide rail has a substantially U-shaped cross section, and at least a part of the endless belt is disposed in a recess of the guide rail .   The actuator according to claim 1 or 2, wherein the endless belt and the main bearing are connected at a center of gravity of the main bearing. The actuator according to claim 1, wherein the connecting member is a flat plate member . The actuator according to any one of claims 1 to 3 , wherein the connecting member is a round shaft member. The counter guide rail extending in the axial direction and the side to which the main bearing is connected are connected to the endless belt on the opposite side across the pulleys, and along the counter guide rail as the endless belt rotates. The actuator according to claim 1, further comprising a counter bearing that linearly moves in an axial direction . The actuator according to any one of claims 1 to 6, wherein a gas bearing is formed between the main bearing and the guide rail.

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