JP4401872B2 - Position control device - Google Patents

Description

  The present invention relates to a position control device that controls the position of a movable member that can move in the longitudinal direction of a shaft member in accordance with the rotation of the shaft member.

  There is a position control device capable of controlling the position of the table in units of 10 nm (see, for example, Patent Document 1). The configuration of this position control device is shown in FIG.

  The guide portion of the table 31 is slidable with respect to the support member 34, and the table 31 is movable in the X-axis direction. A nut 32 is fixed to the table 31, and a screw shaft 33 that rotates by driving of the vibration wave motor 40 is inserted into the nut 32. One end of the screw shaft 33 is connected to a rotation shaft 39 of the vibration wave motor 40 by a coupling 38, and the screw shaft 33 is supported by a bearing 36. The bearing 36 suppresses the displacement of the screw shaft 33 in a direction substantially orthogonal to the X-axis direction and restricts the spatial position of the table 31.

  When the vibration wave motor 40 is driven, the driving force of the vibration wave motor 40 is transmitted to one end side of the screw shaft 33 via the rotation shaft 39. Here, immediately after the vibration wave motor 40 is driven, the other end side of the screw shaft 33 is difficult to immediately rotate due to the frictional force with the nut 32, so that the screw shaft 33 is elastic (twisted around the rotation shaft). Deformation occurs.

  When the vibration wave motor 40 is further driven, the screw shaft 33 rotates in an elastically deformed state, and the table 31 is moved. When the table 31 reaches the target position, the driving of the vibration wave motor 40 is stopped.

  Here, a case where an electromagnetic motor is used instead of the vibration wave motor 40 will be described. When the screw shaft 33 is rotated using the electromagnetic motor and the energization of the electromagnetic motor is interrupted when the table 31 reaches the target position, a restoring force is generated in the elastically deformed screw shaft 33.

  Here, since the other end side of the screw shaft 33 is held by a frictional force with the nut 32, the screw shaft 33 is not rotated by the restoring force. However, one end side of the screw shaft 33 is connected to the rotor of the electromagnetic motor through the rotation shaft 39, and the holding force of the rotor is small, so that the rotor is slightly rotated by the restoring force of the screw shaft 33.

  Thus, when the rotor rotates slightly, the elastically deformed screw shaft 33 is restored. In this case, the elastic deformation of the screw shaft 33 is allowed at least by the amount restored. When external vibration or the like is applied to the position control device in this state, the screw shaft 33 may be elastically deformed, and the position of the table 31 may be slightly shifted.

On the other hand, in the vibration wave motor 40, since a frictional force is generated between the vibration body 40a and the moving body 40b, the elastically deformed screw shaft 33 is difficult to restore even if the vibration wave motor 40 is cut off. Yes. In this way, by keeping the screw shaft 33 elastically deformed, even if external vibration or the like is applied to the position control device, the screw shaft 33 is suppressed from being elastically deformed, and the position of the table 31 is reduced. Can be prevented from shifting. Here, even when external vibration or the like acts to restore the screw shaft 33, the screw shaft 33 is held in an elastically deformed state by the frictional force between the vibrating body 40a and the moving body 40b.
JP 2003-29844 (paragraph numbers 0023 to 0027, FIG. 3 and the like)

  As described above, by using the vibration wave motor as the drive source of the position control device, the positional deviation of the table 31 due to the elastic deformation of the screw shaft 33 can be suppressed. May shift. That is, there is a possibility that the position of the table 31 is shifted due to the backlash in the bearing 36 that supports the screw shaft 33.

  The bearing 36 is provided in order to suppress the displacement of the screw shaft 33 in the direction substantially orthogonal to the X axis as described above, and is a rolling bearing in which balls (or rollers) are arranged between the inner ring and the outer ring. It is configured. In order to facilitate rotation at the bearing 36, a gap is provided between the ball and the inner ring and between the ball and the outer ring.

  Here, when external vibration or the like is applied to the position control device, the screw shaft 33 supported by the bearing 36 is displaced by the play of the gap, and as a result, the position of the table 31 is slightly shifted. There is a risk that.

The present invention includes a shaft member that rotates in response to a driving force from a drive source, first and second bearings that rotatably support the shaft member, and a longitudinal direction of the shaft member according to the rotation of the shaft member. A position control device that controls the position of the moving member by driving control of the driving source, and has an engaging member that engages with the shaft member,
Each of the first and second bearings has a configuration in which rolling elements are disposed between the inner ring and the outer ring. The inner ring of the first bearing is fixed to the shaft member, and the inner ring of the second bearing is fixed to the engaging member. In addition, the outer rings of the first and second bearings are fixed, and by changing the engagement state of the engaging member with respect to the shaft member, the position of the inner ring with respect to the outer ring of the first bearing and the second bearing The position of the inner ring with respect to the outer ring is moved in opposite directions.

  According to the present invention, it is possible to suppress the play in the bearing and improve the positional accuracy of the moving member by bringing the first and second members into pressure contact with the rolling elements using the pressing means. it can.

  Examples of the present invention will be described below.

  A position control apparatus that is Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the configuration of the position control apparatus of this embodiment.

  In FIG. 1, 1 is a table (moving member), and 2 is a nut fixed to the table 1. Reference numeral 3 denotes a screw shaft (ball screw, shaft member) that engages with the nut 2 and rotates around the X-axis by receiving a driving force from a vibration wave motor (drive source) 10 described later. When the screw shaft 3 rotates, the nut 2 moves in the X-axis direction together with the table 1.

  Reference numeral 4 denotes a support member (device main body) that supports various members arranged in the position control device. Reference numeral 5 denotes a guide plate arranged so as to sandwich the nut 2 and prevents the nut 2 from rotating together with the screw shaft 3.

  Reference numeral 6 denotes a bearing (rolling bearing, first bearing), an outer ring (second member) 6a fixed to the support member 4, an inner ring (first member) 6b fixed to the screw shaft 3, and an outer ring. 6a and an inner ring 6b, and rolling elements (balls, rollers, etc.) 6c.

  Reference numeral 7 denotes a thrust bearing (second bearing), which rotatably supports a coupling nut 8 described later. The thrust bearing 7 includes a first ring 7a fixed to the outer ring 6a of the bearing 6, a second ring 7b fixed to the coupling nut 8, and a rolling element 7c disposed between the first and second rings. And have.

  Reference numeral 8 denotes a coupling nut that is fixed to the rotary shaft 9 and functions as a coupling that connects the rotary shaft 9 and the screw shaft 3. That is, by inserting and engaging the screw shaft 3 in the groove portion of the coupling nut 8 fixed to the rotating shaft 9, the screw shaft 3 and the rotating shaft 9 rotate integrally.

  The coupling nut 8 is connected to the outer ring 6a of the bearing 6 through the thrust bearing 7, and can freely rotate around the X axis with respect to the outer ring 6a (first ring 7a) of the bearing 6.

The relative position of the screw shaft 3 and the rotary shaft 9 in the X-axis direction is changed by adjusting the tightening degree of the connecting nut (pressurizing means) 8 with respect to the screw shaft 3 (engagement state of the connecting nut 8 and the screw shaft 3). Can be made. That is, the positions of the screw shaft 3 and the rotating shaft 9 with respect to the support member 4 can be changed.

  Reference numeral 10 denotes a vibration wave motor as a drive source. The vibration body 10a that excites vibrations by applying alternating signals having different phases, and pressurizes and contacts the vibration body 10a, and receives vibration from the vibration body 10a. And a moving body 10b that rotates. The rotating shaft 9 is fixed to the moving body 10b and can rotate around the X axis together with the moving body 10b.

  Reference numeral 11 denotes a position sensor that detects the position of the table 1 in the X-axis direction. A signal (position information) detected by the position sensor is output to the CPU 20, and the position control of the table 1 is performed in the CPU 20. Here, the CPU 20 moves the table 1 in the X-axis direction by driving the vibration wave motor 10. Then, the CPU 20 determines the position of the table 1 based on the output of the position sensor 11, and stops the driving of the vibration wave motor 10 when the table 1 reaches the target position.

  In this embodiment, since the vibration wave motor 10 is used as a drive source, the screw shaft 3 rotates in a state of being twisted around the rotation shaft by elastic deformation as described above. That is, the screw shaft 3 remains twisted by elastic deformation while the table 1 is being driven and after the drive is stopped.

  In the position control device having the above-described configuration, when the coupling nut 8 is tightened with respect to the screw shaft 3, the rotary shaft 9 enters the groove 3a of the screw shaft 3, and the relative relationship between the rotary shaft 9 and the screw shaft 3 in the X-axis direction. The position changes. At this time, a force for displacing the inner ring 6b toward the vibration wave motor 10 (in the direction of the arrow X1 in FIG. 3) acts on the inner ring 6b of the bearing 6 fixed to the screw shaft 3. Further, the second ring 7b of the thrust bearing 7 fixed to the coupling nut 8 is subjected to a force that displaces the second ring 7b in the direction away from the vibration wave motor 10 (direction approaching the first ring 7a). To do.

  While the outer ring 6a of the bearing 6 is fixed to the support member 4, the inner ring 6b is displaced to the vibration wave motor 10 side (in the direction of the arrow X1 in FIG. 3) under the action of the above-described force. Then, they abut on a part of the inner ring 6b and the outer ring 6a (areas indicated by A and B in FIG. 3).

As a result, the rolling element 6c always comes into contact (pressure contact) with a part of the inner ring 6b and the outer ring 6a, and therefore between the rolling element 6c and the inner ring 6b and between the rolling element 6c and the outer ring 6a. It is possible to suppress the occurrence of play in the bearing 6 because there is no gap between them. And it can suppress that the position of the table 1 shifts slightly by suppressing generation | occurrence | production of the play in the bearing 6. FIG.

  On the other hand, when the force acts on the second ring 7b of the thrust bearing 7, the first ring 7a and the second ring 7b come into contact with the rolling element 7c. Thereby, it is possible to suppress the occurrence of play in the thrust bearing 7.

Here, if a lubricant or the like is applied to a portion where the inner ring 6b and the outer ring 6a are in contact with the rolling elements 6c , the screw shaft 3 can be smoothly rotated.

  On the other hand, the contact state (pressing force) of the outer ring 6a and the inner ring 6b with the rolling element 6c and the contact state of the first ring 7a and the second ring 7b with the rolling element 7c depend on the degree of tightening of the coupling nut 8 with respect to the screw shaft 3. Can be adjusted easily by changing The vibration wave motor 10 is attached to the rotary shaft 9 after adjusting the thrust force in the bearing 6 and the thrust bearing 7 (adjustment so as to eliminate backlash in the bearings 6 and 7).

  Further, the guide plate 5 is arranged along the outer shape of the nut 2, and the nut 2 rotates around the X axis by adjusting the gap (distance in the direction orthogonal to the X axis) between the nut 2 and the guide plate 5. Can be suppressed.

  Furthermore, by using the position sensor 11, it is possible to prevent one end of the screw shaft 3 from striking against the bottom surface of the groove portion 1 a of the table 1 and to easily move the table 1 to the initial position.

  According to the position control apparatus of the present embodiment, the table 1 can be positioned with higher accuracy by eliminating the backlash in the bearing 6 that supports the screw shaft 3 as described above.

  Next, a position control apparatus that is Embodiment 2 of the present invention will be described. FIG. 2 is a schematic diagram showing the configuration of the position control device of the present embodiment. In FIG. 2, the same reference numerals are used for the same members as those described in the first embodiment.

  In the first embodiment, the rotary shaft 9 fixed to the moving body 10b of the vibration wave motor 10 and the screw shaft 3 inserted into the nut 2 are connected via the coupling nut 8, but in this embodiment, A screw shaft 23 in which the rotary shaft 9 and the screw shaft 3 are integrally formed is used. Thus, the member corresponding to the rotating shaft 9 and the screw shaft 3 is constituted by the screw shaft 23 which is one member, so that a member for connecting the two members becomes unnecessary.

The screw shaft 23 is inserted into the table 21 at one end side, and is fixed to the moving body 10b of the vibration wave motor 10 at the other end side. Further, the inner ring 6 b of the bearing 6 is fixed to the screw shaft 23.

  In the first embodiment, the table 1 and the nut 2 are provided. In the present embodiment, the table 21 in which the table 1 and the nut 2 are integrally formed is provided.

The thrust bearing 7 is connected to a fixing nut (pressurizing means) 28. A screw portion is formed on the fixing nut 28, and the screw portion is engaged with the screw shaft 23. For this reason, the screw shaft 23 can be displaced in the thrust direction (X-axis direction) by tightening the fixing nut 28 with respect to the screw shaft 23 (rotating about the X-axis). That is, the position of the screw shaft 23 relative to the support member 4 can be changed in the X-axis direction.

  In the first embodiment, the coupling nut 8 is tightened to adjust the relative positions of the screw shaft 3 and the rotary shaft 9, thereby applying a pressing force in the X-axis direction to the bearing 6. On the other hand, in the present embodiment, the thrust in the thrust direction is applied to the bearing 6 and the thrust bearing 7 by tightening the fixing nut 28 and adjusting the position of the entire screw shaft 23 in the X-axis direction.

When the fixing nut 28 is tightened with respect to the screw shaft 23 , a force is generated that displaces the screw shaft 23, to which the inner ring 6b of the bearing 6 is fixed, toward the vibration wave motor 10 (corresponding to the arrow X1 direction in FIG. 3). By this force, the screw shaft 23 and the inner ring 6b are displaced toward the vibration wave motor 10 side.

  In the bearing 6, the outer ring 6 a is fixed to the support member 4, whereas the inner ring 6 b is displaced toward the vibration wave motor 10, so that a thrust force is applied to the rolling elements 6 c of the bearing 6 by the inner ring 6 b. Thereby, since the inner ring 6b and the outer ring 6a are in contact (pressing contact) with the rolling element 6c, it is possible to suppress the occurrence of play in the bearing 6 as in the first embodiment.

  Further, when the fixing nut 28 is tightened with respect to the screw shaft 23, the second ring 7b of the thrust bearing 7 fixed to the fixing nut 28 has a force in a direction to bring the second ring 7b closer to the first ring 7a. Works.

  Here, since the first ring 7a is fixed to the outer ring 6a of the bearing 6, the first ring 7a and the second ring 7b become the rolling elements 7c when the second ring 7b is subjected to the above action. Contact (pressure contact) will occur. Thereby, it is possible to suppress the occurrence of play in the thrust bearing 7.

  The vibration wave motor 10 is attached to the screw shaft 23 after adjusting the thrust force in the bearing 6 and the thrust bearing 7 (adjusting so as to suppress the play in the bearings 6 and 7).

  According to this embodiment, since the rotation shaft of the vibration wave motor 10 and the shaft for moving the table 21 are integrally formed, a member for connecting the two shafts becomes unnecessary. Further, since the table and the nut, which are separate members in the first embodiment, are integrated in the present embodiment, the rigid displacement of the members can be suppressed. In addition, since the rotation axis of the table 21 is easily matched with the rotation axis of the screw shaft 23, the driving efficiency of the table 21 accompanying the rotation of the screw shaft 23 can be improved.

  Furthermore, since the number of parts can be reduced by integrating a plurality of members as described above, the assembly man-hour of the position control device can be reduced, and the cost can be reduced.

The figure which shows the structure of the position control apparatus which is Example 1 of this invention. The figure which shows the structure of the position control apparatus which is Example 2 of this invention. The enlarged view of a bearing. The figure which shows the structure of the conventional position control apparatus.

Explanation of symbols

1: Table 3, 23: Screw shaft (ball screw)
6: bearing 6a: outer ring 6b: inner ring 6c: rolling element 8: coupling nut 10: vibration wave motor 28: fixed nut

Claims (2)

A shaft member that rotates in response to a driving force from a drive source, first and second bearings that rotatably support the shaft member, and movable in the longitudinal direction of the shaft member in accordance with the rotation of the shaft member A position control device that controls the position of the moving member by driving control of the driving source,
An engaging member that engages with the shaft member;
Each of the first and second bearings has a configuration in which rolling elements are disposed between an inner ring and an outer ring,
The inner ring of the first bearing is fixed to the shaft member, the inner ring of the second bearing is fixed to the engaging member, and the outer rings of the first and second bearings are fixed,
The position of the inner ring with respect to the outer ring of the first bearing and the position of the inner ring with respect to the outer ring of the second bearing are moved in opposite directions by changing the engagement state of the engagement member with the shaft member. A position control device.   The position control device according to claim 1, wherein the shaft member is elastically deformable so as to be twisted around the rotation axis.

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