JP2007193663A - Axial direction slight movement mechanism with rotary mechanism, and coarse and fine movement positioning apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial direction slight movement mechanism having a rotary mechanism which can achieve high accuracy and high-response fine movement operation and can prevent a piezoelectric actuator from being damaged. <P>SOLUTION: The axial direction fine movement mechanism with the rotation mechanism comprises two rolling bearing apparatuses which are arranged opposite and to which pre-load is applied, a housing fixed on a base board and allowed to be engaged with respective outer rings of the rolling bearing apparatuses; and two piezoelectric actuators arranged in parallel in an expanding direction. Respective inner rings of the rolling bearing apparatuses are engaged with a screw shaft, and the inner rings are fixed on the screw shaft in the axial direction. One of the outer rings is restricted in the axial direction, and a piston for pressing the other outer ring and a spacer allowed to be abutted against the piston and having a circular arc-like cross-sectional shape in the axial direction are arranged between the piezoelectric actuator and the other outer ring, to make the axial-direction distance between the outer rings by the expansion of the plurality of piezoelectric actuators change. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an axial fine movement mechanism with a rotation mechanism that performs high-precision fine positioning within a long stroke range, and a positioning device using the same, and in particular, is capable of fine movement operation with high precision and high responsiveness and piezoelectricity. The present invention relates to an axial fine movement mechanism and a coarse / fine movement positioning device with a rotation mechanism that can prevent the actuator from being damaged.

  A conventional coarse / fine positioning device combines a coarse motion mechanism that drives a long stroke range with a ball screw device in which a screw shaft and a nut are screwed together with a fine motion mechanism using a piezoelectric actuator, and performs coarse motion operation and fine motion operation. Is going. As a conventional coarse / fine movement positioning device, for example, a technique described in Non-Patent Document 1 is known. In the first configuration of Non-Patent Document 1, a piezoelectric actuator is disposed between the coarse movement table and the fine movement table, and the positions of the base and the fine movement table are changed by expansion and contraction of the piezoelectric actuator. In the second configuration of Non-Patent Document 1, a piezoelectric actuator is disposed between a nut of a ball screw device and a moving table, and the positions of the base and the moving table are changed by expansion and contraction of the piezoelectric actuator. With such a configuration, high-precision fine positioning at the nanometer level is performed within a long stroke range.

Further, as in the technique described in Non-Patent Document 2, a backlash between a screw shaft and a nut of a ball screw device is eliminated by a coil spring, and a piezoelectric actuator disposed between one end of the screw shaft and a base is provided. There is also known one that performs expansion and contraction and fine positioning in the axial direction of a moving table fixed to a nut.
The piezoelectric actuator used in such a case is generally a laminated piezoelectric actuator. The laminated piezoelectric actuator has sufficient strength and rigidity for a load in the compression direction, but a load in the tensile direction. On the other hand, the mechanical properties of the material of the piezoelectric actuator and the strength due to the adhesive strength between the laminates are extremely weak, and even a small tensile load may be damaged.

FIG. 7 is a diagram for explaining a conventional piezoelectric actuator mounting structure.
In order to solve this problem, a piezoelectric actuator manufacturer (for example, Physik Instrument, Germany) presses the output shaft 101 of the piezoelectric actuator 100 with a spring 102 as shown in FIG. It is recommended that the piezoelectric actuator 100 has a structure in which a compressive load acts even when acting on the piezoelectric actuator 100.

Jiro Otsuka et al., “Precision positioning mechanism”, 2nd edition, Industrial Research Co., Ltd., August 15, 2001, p. 118-201 Jiro Otsuka and two others, “Development of a small displacement sensor with 1 nm resolution and a compact ultra-precision positioning device”, Journal of Precision Engineering, Japan Society for Precision Engineering, October 5, 2003, Vol. 69, No. 10, p. . 1431

However, in the coarse / fine movement positioning device described in Non-Patent Documents 1 and 2, since both ends of the piezoelectric actuator are directly attached to the nut or the moving base, if the coarse / fine movement positioning device is moved to the left and right, the load is applied in the horizontal direction. Acts, and there is a problem that the piezoelectric actuator may be damaged by a tensile load acting on the piezoelectric actuator.
When the mounting structure shown in FIG. 7 is applied to the coarse / fine movement positioning device described in Non-Patent Documents 1 and 2, the tensile load acting on the piezoelectric actuator is low in a range smaller than the compression load by the spring disposed on the output shaft. Although it is possible to perform a predetermined positioning for movement at a high speed response, the spring supporting the tension direction is a relatively soft spring for high-speed response, so that the rigidity of the fine movement mechanism is reduced and its inherent If the frequency decreases and an attempt is made to perform fine movement at high speed, there is a problem that oscillation may occur and high-speed response may not be possible. This is because the coarse / fine movement positioning device has a two-axis overlapping structure that moves in a two-dimensional direction (XY direction), or even if it has only one axis, parts such as a mounting jig are attached to the moving table. As a result, it is particularly important when the mass of the movable table becomes large.

In order to solve this problem, for example, a method of arranging a plurality of piezoelectric actuators in parallel with respect to the expansion / contraction direction is conceivable.However, if the characteristics of each piezoelectric actuator are different and variations occur, the displacement of each piezoelectric actuator is changed. There may be a problem in that it cannot be accurately transmitted to the moving table or the fine movement table, and the fine movement operation cannot be performed accurately.
Therefore, the present invention has been made paying attention to such an unsolved problem of the conventional technique, and can perform fine movement operation with high accuracy and high response and prevent damage to the piezoelectric actuator. An object of the present invention is to provide an axial fine movement mechanism with a rotation mechanism and a coarse / fine movement positioning device.

  In order to achieve the above object, an axial fine movement mechanism with a rotation mechanism according to claim 1 of the present invention comprises two rolling bearing devices that are arranged opposite to each other and applied with a preload, and respective inner rings of the rolling bearing device. A shaft to be fitted and a plurality of piezoelectric actuators arranged in parallel to the expansion and contraction direction, the inner ring is fixed to the shaft in the axial direction, and one of the outer rings of the rolling bearing device is restrained in the axial direction. A spacer is provided between the plurality of piezoelectric actuators and the other of the outer rings to average the variation of the displacements of the plurality of piezoelectric actuators and transmit a combined displacement thereof. The distance is changed by expansion and contraction of the plurality of piezoelectric actuators.

  With such a configuration, when a voltage is applied to each piezoelectric actuator and each piezoelectric actuator expands and contracts, the axial distance between the outer rings changes. At this time, since one of the outer rings is constrained in the axial direction, elastic deformation occurs between the outer ring and the inner ring due to the displacement between the outer rings, and each inner ring is displaced. Then, the shaft moves with the displacement of the inner ring. Further, when the piezoelectric actuator is extended, a preload reaction force acts on the piezoelectric actuator, so that a fine movement operation is performed while applying a compressive load.

  In addition, since the fine movement operation is performed by the plurality of piezoelectric actuators arranged in parallel with the expansion / contraction direction, the rigidity of the axial direction fine movement mechanism with the rotation mechanism is increased. Furthermore, since the variation of the displacement of the plurality of piezoelectric actuators is averaged and the combined displacement is transmitted to the other outer ring via the spacer, the influence of the variation of the displacement can be reduced.

On the other hand, in order to achieve the above object, the coarse / fine motion positioning device according to claim 2 according to the present invention is screwed to the screw shaft and rotatably supported by a base, and is fixed to the moving table. A coarse movement mechanism that moves the moving table in the axial direction with respect to the base by rotation of the screw shaft, two rolling bearing devices that are arranged opposite to each other and applied with a preload, A housing fixed to a base and fitted with each outer ring of the rolling bearing device; and a plurality of piezoelectric actuators arranged in parallel with respect to the expansion and contraction direction. The inner ring is fixed to the screw shaft in the axial direction, one of the outer rings is constrained in the axial direction, and the plurality of piezoelectric actuators and the other of the outer rings are between Displacement of piezoelectric actuator An axial fine movement mechanism with a rotation mechanism provided with a spacer that can average the variation and transmit the combined displacement, and change the axial distance between the outer rings by expansion and contraction of the plurality of piezoelectric actuators. Prepare.
With such a configuration, in the coarse motion mechanism, when the screw shaft rotates, the nut fixed to the moving table moves in the axial direction, and the moving table moves accordingly.

In the axial fine movement mechanism with a rotation mechanism, when a voltage is applied to each piezoelectric actuator and each piezoelectric actuator expands and contracts, the axial distance between the outer rings changes. At this time, since one of the outer rings is constrained in the axial direction, elastic deformation occurs between the outer ring and the inner ring due to the displacement between the outer rings, and each inner ring is displaced. Then, the moving table moves with the displacement of the inner ring. Further, when the piezoelectric actuator is extended, a preload reaction force acts on the piezoelectric actuator, so that a fine movement operation is performed while applying a compressive load.
In addition, since the fine movement operation is performed by the plurality of piezoelectric actuators arranged in parallel with the expansion / contraction direction, the rigidity of the axial direction fine movement mechanism with the rotation mechanism is increased. Furthermore, since the variation of the displacement of the plurality of piezoelectric actuators is averaged and the combined displacement is transmitted to the other outer ring via the spacer, the influence of the variation of the displacement can be reduced.

Furthermore, the coarse / fine motion positioning device according to claim 3 according to the present invention is the coarse / fine motion positioning device according to claim 2, wherein a piston is provided between the other outer ring and the spacer, The cross-sectional shape in the axial direction in contact with the piston is arcuate.
With such a configuration, the axial cross-sectional shape that abuts the piston is an arc shape, so that the spacer remains on the piston even when there is a variation in the displacement as compared to a flat cross-sectional shape. The contact position is not easily biased. Therefore, the variation of the displacement is averaged, and those combined displacements are transmitted to the other outer ring through the spacer.

  As described above, according to the axial fine movement mechanism with a rotating mechanism according to the first aspect of the present invention or the coarse / fine movement positioning apparatus according to the second aspect, the opposingly arranged rolling bearing device is used as a spring member having high rigidity. By functioning and combining the high rigidity of the piezoelectric actuator in the compression direction and the highly rigid spring member, the rigidity of the axial fine movement mechanism with rotating mechanism can be maintained high, so that a fine movement operation with high responsiveness can be realized. The effect of being able to be obtained. Further, when the piezoelectric actuator is extended, a preload reaction force acts on the piezoelectric actuator, and a fine movement operation can be performed while applying a compressive load. Therefore, it is possible to prevent the piezoelectric actuator from being damaged due to a tensile load. Is obtained. Further, since the fine movement operation is performed by the plurality of piezoelectric actuators arranged in parallel with respect to the expansion / contraction direction, it is possible to obtain an effect that a fine movement operation with higher responsiveness can be realized. Furthermore, since the influence of the variation in the displacement can be reduced by transmitting the displacement of the piezoelectric actuator through the spacer, an effect that a highly accurate fine movement operation can be realized is obtained.

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 are views showing an embodiment of an axial fine movement mechanism and a coarse / fine movement positioning device with a rotation mechanism according to the present invention.
First, the moving mechanism of the coarse / fine movement positioning device 1 will be described.
FIG. 1 is a cross-sectional view of an axial fine movement mechanism 41 with a rotation mechanism.
FIG. 2 is a plan view of the coarse / fine movement positioning device 1.
FIG. 3 is a side view of the coarse / fine movement positioning device 1.

  Reference numeral 2 denotes a linear guide mechanism, which is a linear guide device including a bowl-shaped slider 4 assembled to the rail 3 via a rolling element, and the rail 3 is installed on the base 5 of the coarse / fine motion positioning device 1. The moving table 6 of the coarse / fine movement positioning device 1 is mounted on the moving table mounting surface 4a of the slider 4 with a bolt or the like. The linear guide mechanism 2 includes two rails 3 installed on both sides of the screw shaft 11 in parallel to the longitudinal direction (referred to as the axial direction) of the screw shaft 11 of the coarse motion mechanism 10, and 2 assembled to each rail 3. In total, there are four sliders 4.

  The coarse movement mechanism 10 includes a plurality of illustrated shaft raceway grooves 11 a formed on the outer peripheral surface of the screw shaft 11 and nut raceway grooves (not shown) facing the shaft raceway groove 11 a formed on the inner peripheral surface of the nut 12. A ball screw device 13 as a feed screw device screwed through a non-ball, a drive motor 14 disposed at one end of the screw shaft 11 and capable of rotating in the forward and reverse directions such as a stepping motor installed on the base 5, The coupling 15 includes a coupling 15 that couples the drive motor 14 and the screw shaft 11, and a support bearing 16 such as a deep groove ball bearing that is disposed in the front stage of the coupling 15 and installed on the base 5.

The nut 12 is fixed to the movable table 6 and is screwed to the screw shaft 11 with no play in the axial direction by preloading with an oversized ball or the like. Further, the support bearing 16 supports the screw shaft 11 rotatably and supports the screw shaft 11 so as to be movable by play in the axial direction.
Reference numeral 17 denotes a position sensor which is fixed to the movable table 6 and detects fine irregularities formed at equal intervals on a scale 18 installed on the base 5 in parallel with the screw shaft 11 and controls the detection signal to be described later. A function of outputting to the device 45 is provided. The control device 45 measures the relative movement amount between the moving base 6 and the base 5 using the detection signal of the position sensor 17.

In FIG. 1, 20a and 20b are angular contact ball bearings as rolling bearing devices, and are formed on the outer ring raceways 22a and 22b formed on the inner peripheral surfaces of the outer rings 21a and 21b and on the outer peripheral surfaces of the inner rings 23a and 23b. It has a plurality of balls 25a and 25b as rolling elements disposed between the inner ring raceways 24a and 24b.
Angular contact ball bearings 20a and 20b are opposed to each other as a front combination, and the inner peripheral surfaces of the inner rings 23a and 23b are fitted to the outer peripheral surface of a fitting shaft 26 formed on the drive motor 14 side of the screw shaft 11. The outer peripheral surfaces of 22a and 22b are fitted to the inner peripheral surface of the housing 27 fixed to the base 5 with bolts or the like, and support the screw shaft 11 together with the support bearing 16 so as to be rotatable.

Reference numeral 29 denotes an inner ring locking portion, which is a large diameter portion having a diameter substantially equal to the outer diameter of the inner rings 23a and 23b formed between the shaft raceway groove 11a of the screw shaft 11 and the fitting shaft 26, One side surface of the inner ring 23a is locked.
Reference numeral 30 denotes an inner ring spacer, which is a cylindrical member having an outer diameter and an inner diameter substantially equal to those of the inner rings 23a and 23b. The inner circumferential surface of the inner ring is fitted to the outer circumferential surface of the fitting shaft 26 and the inner rings 23a and 23b. It is arranged between.
Reference numeral 32 denotes a lock nut, which is screwed into a screw portion 33 provided on the drive motor 14 side of the fitting shaft 26 and tightens the inner ring 23a, the inner ring spacer 30 and the inner ring 23b with the inner ring engaging portion 29, The movement of the inner rings 23a and 23b on the screw shaft 11 is fixed.

  Reference numeral 50 denotes a piezoelectric actuator, which is a standardized laminated piezoelectric actuator, which is formed by laminating one or a plurality of piezoelectric elements in a columnar shape, and expands and contracts in the axial direction according to an applied voltage. The piezoelectric actuator 50 is a solid actuator in which piezoelectric elements are stacked in a prismatic shape (for example, a resin exterior actuator, model number AE0505D08, manufactured by NEC Tokin Corporation). In FIG. 1, two piezoelectric actuators 50 are arranged in parallel with respect to the expansion / contraction direction.

Reference numeral 38 denotes an outer ring locking portion, which is a step portion having a diameter substantially equal to the inner diameter of the outer rings 21a and 21b formed at a position facing the inner ring locking portion 29 on the inner peripheral surface of the housing 27, and the outer ring 21a. Lock one side of the.
Reference numeral 51 denotes a piston, which is a columnar member fitted to the inner peripheral surface of the housing 27, and a clearance hole 53 for avoiding interference with the lock nut 32 is formed on the end surface on the lock nut 32 side. The nut 32 is enclosed in the escape hole 53 and the outer peripheral side of the end surface is brought into contact with the outer ring 21b.

Reference numeral 55 denotes a spacer, which is a cylindrical member fitted to the inner peripheral surface of the housing 27. One end surface abuts on the end surface of the piston 51 opposite to the lock nut 32, and the axial direction of the end surface is axial. The cross-sectional shape is an arc shape. In addition, two storage holes 52 for storing the piezoelectric actuator 50 are formed on the opposite end face at equal intervals with the shaft core of the spacer 55 interposed therebetween.
Reference numeral 39 denotes a cover, which is a hollow disk member having an outer diameter substantially equal to that of the housing 27, and two concave holes 54 corresponding to the respective storage holes 52 are formed on the end face on the spacer 55 side. It is formed at equal intervals across the core.

  The inner diameters of the storage hole 52 and the recessed hole 54 are formed such that the four corners of the prismatic piezoelectric actuator 50 are inscribed. Therefore, the piezoelectric actuator 50 is sandwiched between the bottom surfaces of the storage hole 52 and the recessed hole 54. As a result, the two piezoelectric actuators 50 are arranged in parallel with the expansion / contraction direction coinciding with the axial direction. Further, the piezoelectric actuator 50 is inserted into the storage hole 52 and the recessed hole 54 in a non-energized state.

The cover 39 is fastened to the housing 27 with bolts or the like using screw holes 27a formed on the end surface of the housing 27, and between the outer ring locking portions 38, the outer rings 21a and 21b, the piston 51, the spacer 55 and The piezoelectric actuator 50 is pressed.
As a result, the outer ring 21a is restrained from being moved in the axial direction by the outer ring locking portion 38 and the outer ring 21b on the side that is not restrained is pressed via the piston 51, the spacer 55 and the piezoelectric actuator 50, and the angular ball bearing 20a, A predetermined preload is applied to 20b, and a gap 40 is formed as an axial distance between the outer rings 21a and 21b.

The axial fine movement mechanism 41 with a rotation mechanism includes angular ball bearings 20a and 20b, a fitting shaft 26, an inner ring locking portion 29, an inner ring spacer 30, a lock nut 32, a housing 27, an outer ring locking portion 38, a piston 51, As shown in FIG. 1, the seat 55, the piezoelectric actuator 50, the cover 39, and the like are disposed at the end opposite to the end of the screw shaft 11 to which the drive motor 14 is connected via the coupling 15. Consists of. The housing 27 is fixed to the base 5 with bolts or the like.
The coarse / fine movement positioning device 1 includes an axial fine movement mechanism 41 with a rotation mechanism and a coarse movement mechanism 10.

Next, the configuration of the control system of the coarse / fine movement positioning device 1 will be described.
FIG. 4 is a block diagram illustrating a configuration of the control device 45.
As shown in FIG. 4, the coarse / fine movement positioning device 1 is equipped with a control device 45 that performs coarse / fine movement positioning.
The control device 45 includes a control unit 46 that executes coarse / fine movement positioning processing, a storage unit 47 that stores programs executed by the control unit 46, various data used for the control unit 46, processing results of the control unit 46, and the like, and the drive motor 14. A motor driving unit 48 for driving the actuator, an actuator driving unit 49 for driving the piezoelectric actuator 50, and an amplifier (not shown) that amplifies the control voltage from the actuator driving unit 49 and outputs the amplified control voltage to the piezoelectric actuator 50. Has been.
The storage unit 47 stores a coarse / fine motion control program for performing coarse / fine motion control, and a movement destination instruction table storing a target position and a stop time for stopping the moving platform 6.

Next, processing executed by the control device 45 will be described.
The control unit 46 activates the coarse / fine motion control program stored in the storage unit 47, and executes the coarse / fine motion positioning process shown in the flowchart of FIG. 5 in accordance with the coarse / fine motion control program.
FIG. 5 is a flowchart showing the coarse / fine movement positioning process.
When the coarse / fine movement positioning process is executed by the control unit 46, as shown in FIG. 5, first, the process proceeds to step S100.
In step S100, an initial setting command for instructing about half of the effective stroke of the piezoelectric actuator 50 is output to the actuator drive unit 49, the process proceeds to step S102, and the target position and stop time are read from the movement destination instruction table, The process proceeds to step S104.

In step S104, the deviation between the target position and the current position is calculated, the number of rotations of the screw shaft 11 required when the nut 12 moves the length corresponding to the calculated deviation is calculated, and the calculated number of rotations is roughly calculated. A coarse motion control process to be output to the motor drive unit 48 as a motion command is executed, and the process proceeds to step S106.
In step S106, a detection signal is input from the position sensor 17, and the process proceeds to step S108, where it is determined whether the drive motor 14 has stopped based on the input detection signal, and it is determined that the drive motor 14 has stopped. (Yes) shifts to Step S110.

In step S110, a detection signal is input from the position sensor 17, the process proceeds to step S112, a deviation between the target position and the current position is calculated based on the input detection signal, and the process proceeds to step S114.
In step S114, a fine movement command is generated by PID control so as to eliminate the calculated deviation, a fine movement control process for outputting the generated fine movement instruction to the actuator drive unit 49 is executed, and the process proceeds to step S116.

In step S116, it is determined whether or not the calculated deviation is equal to or smaller than a predetermined value. When it is determined that the deviation is equal to or smaller than the predetermined value (Yes), the process proceeds to step S118, and the movable platform 6 is set to the target position. The operation is stopped for the stop time, and the process proceeds to step S120.
In step S120, it is determined whether or not the next target position and stop time are registered in the movement destination instruction table. When it is determined that the next target position and stop time are not registered (No), End the process and return to the original process.

On the other hand, when it is determined in step S120 that the next target position and stop time are registered (Yes), the process proceeds to step S100.
On the other hand, when it is determined in step S116 that the deviation is larger than the predetermined value (No), the process proceeds to step S110.
On the other hand, when it determines with the drive motor 14 not stopping by step S108 (No), it transfers to step S106.

Next, the operation of the present embodiment will be described.
When the coarse / fine movement positioning device 1 starts operation, the control unit 46 activates the coarse / fine movement control program.
When the coarse / fine movement control program is activated, the control unit 46 outputs an initial setting command to the actuator driving unit 49. The actuator driving unit 49 converts the initial setting command into the initial setting voltage Vo, and supplies this to the piezoelectric actuator 50 to hold it. The initial setting voltage Vo is a voltage that gives an extension of about half of the effective stroke of the piezoelectric actuator 50, and the position of the moving base 6 in a state where the initial setting voltage Vo is applied to the piezoelectric actuator 50 is the original position.

Next, the control unit 46 confirms that the moving platform 6 has stopped at the original position, and reads the first target position and stop time stored in the destination instruction table.
The control unit 46 that has read the target position and the like calculates the deviation between the target position and the current position (original position), and the rotation of the screw shaft 11 required when the nut 12 moves the length corresponding to the calculated deviation. The number is calculated and output to the motor drive unit 48 as a coarse motion command. The motor drive unit 48 converts the coarse motion command into a drive signal for the drive motor 14, and supplies this to the drive motor 14.

Since the drive motor 14 is a stepping motor, the drive signal is a pulse signal corresponding to the number of angular steps of the stepping motor necessary for rotating the calculated rotation speed of the screw shaft 11.
When the drive signal is supplied, the drive motor 14 rotates by the number of rotations corresponding to the drive signal, and the screw shaft 11 rotates to move the nut 12 in the axial direction.
At this time, the control unit 46 inputs a pulse-shaped detection signal indicating the unevenness of the scale 18 output from the position sensor 17 as the moving table 6 moves, and counts the number to recognize the position of the moving table 6. While waiting for the moving table 6 to stop (stop of rotation of the drive motor 14), the position recognized when the moving table 6 stops is recognized as the current position.

As described above, the coarse movement mechanism 10 that rotates the screw shaft 11 and moves the movable table 6 together with the nut 12 relative to the base 5 in the axial direction performs the coarse movement operation of the movable table 6.
In this case, the piezoelectric actuator 50 is only applied with the initial setting voltage Vo and is not subjected to feedback control by the position sensor 17. In addition, the piezoelectric actuator 50 is in a state in which a compressive load is applied due to the preload reaction force of the angular ball bearings 20a and 20b.

The control unit 46 that has finished the coarse movement operation inputs a detection signal from the position sensor 17, calculates a deviation between the target position and the current position, generates a fine movement command by PID control so as to eliminate the calculated deviation, and generates The fine movement command is output to the actuator driver 49. The actuator driver 49 converts the fine movement command into a voltage and applies this control voltage to the piezoelectric actuator 50.
In the axial fine movement mechanism 41 with the rotation mechanism, the relative displacement amount between the outer ring 21a and the inner ring 23a, which is half the displacement of the piezoelectric actuator 50, becomes the fine movement displacement amount of the moving base 6. A voltage obtained by adding a control voltage that gives a displacement twice as much as the deviation and the initial setting voltage Vo is applied.

FIG. 6 is a view for explaining the fine movement operation of the axial fine movement mechanism 41 with the rotation mechanism.
For example, when the piezoelectric actuator 50 is extended by 2X, the pressing force generated by the extension presses the outer ring 21b in addition to the preload before fine movement control as shown in FIG. (Left in FIG. 1; hereinafter referred to as the left in the axial direction), the gap 40 is further narrowed by 2X to absorb the elongation of the piezoelectric actuator 50. The displacement of the gap 40 is in addition to the preload before performing fine movement control on the contact surface between the ball 25b and the outer ring raceway 22b and the inner ring raceway 24b and the contact surface between the ball 25a and the outer ring raceway 22a and the inner ring raceway 24a. They are pressed and elastic deformation occurs between them, and the inner rings 23a and 23b are each displaced by X to the left in the axial direction. It should be noted that the amount of displacement of the inner rings 23a, 23b relative to the amount of displacement of the outer ring 21b can be appropriately set according to the magnitude of the preload, the rigidity of the angular ball bearings 20a, 20b, and other conditions.

On the other hand, when the piezoelectric actuator 50 contracts by 2X, the pressing force decreases, the outer ring 21b is moved in the axial direction (right in FIG. 1, hereinafter referred to as the right in the axial direction), and the gap 40 becomes wider by 2X. The shrinkage of the piezoelectric actuator 50 is absorbed. Due to the displacement of the gap 40, elastic deformation occurs, and the inner rings 23a and 23b are each displaced X to the right in the axial direction.
As described above, since the inner ring 23a, 23b absorbs the displacement 2X of the gap 40 in units of X, the inner rings 23a, 23b are moved to the screw shaft 11 when the force of the angular ball bearings 20a, 20b pressing each other is balanced. At the same time, X moves in the axial direction. The movement of the screw shaft 11 in this case is absorbed by the axial play of the support bearing 16 and the contraction of the coupling 15.

Thereby, the nut 12 moves X in the axial direction, and the moving base 6 moves X in the axial direction left relative to the base 5. That is, the relative displacement amount of the outer ring 21 a and the inner ring 23 a that is X displacement that is half the 2X displacement (expansion / contraction amount) of the piezoelectric actuator 50 becomes the fine movement displacement amount of the movable platform 6.
Further, in the axial fine movement mechanism 41 with the rotation mechanism, the displacement of the piezoelectric actuator 50 is transmitted to the outer ring 21 b via the spacer 55. At this time, the spacer 55 has an arcuate cross-sectional shape in contact with the piston 51, so that the spacer 55 can be used even when the variation in displacement occurs as compared with the flat cross-sectional shape. The position in contact with the piston 51 is not biased. Therefore, the variation in the displacement is averaged and the resultant displacement is transmitted to the outer ring 21b via the spacer, so that the influence of the variation in the displacement can be reduced.

Thus, the fine movement operation is performed, and the control unit 46 stops the movable platform 6 at the target position while performing feedback control so as to eliminate the deviation between the current position and the target position. The moving platform 6 is stopped at the target position for the stop time.
Then, when the next target position or the like is stored in the movement destination instruction table, the control unit 46 releases the control voltage held by the actuator drive unit 49 for the fine movement operation, and the next target position or the like. , And the movement amount of the moving table 6 resulting from the result is counted by the detection signal of the position sensor 17 in the same manner as described above to recognize the new current position, and the same coarse motion control and fine motion control as described above are performed.

  In addition, since the gap 40 between the outer rings 21a and 21b is changed by the expansion and contraction of the piezoelectric actuator 50 to perform the fine movement operation, the preload is changed as a result. However, the elongation accompanying the fine movement operation of the piezoelectric actuator 50 is the maximum. Since the change in the preload caused by this is about 10 μm, usually about several μm, there is no indentation or the like on the outer ring raceways 22a and 22b, the inner ring raceways 24a and 24b, and the balls 25a and 25b.

  Further, the axial fine movement mechanism 41 with the rotation mechanism does not have a spring having low rigidity, and the angular ball bearings 20a and 20b function as spring members having extremely high rigidity, and are extremely high with respect to a load in the compression direction. By the combination of the rigid piezoelectric actuator 50 and the highly rigid spring member, the axial fine movement mechanism 41 with a rotating mechanism has substantially the same rigidity as a bearing unit that does not incorporate the piezoelectric actuator 50 both statically and dynamically. Since it can be maintained, a responsive and stable fine movement operation can be realized.

Further, the preload reaction force applied to the angular ball bearings 20a and 20b acts on the piezoelectric actuator 50, and the fine movement operation is always performed while applying a compressive load. There is no need to use a spring.
Further, by using the housing 27 that is longer than the piezoelectric actuator 50, the bearing unit can be assembled by the same method as that for assembling the piezoelectric actuator 50, and the shaft with the rotation mechanism can be easily assembled without paying special attention to the assembly of the piezoelectric actuator 50. The direction fine movement mechanism 41 can be assembled.

Further, if the piezoelectric actuator 50 is incorporated in the spacer 55 with the receiving hole 52 and the recessed hole 54 as guides, the piezoelectric actuator 50 is automatically arranged on the same axis, so that a radial load or moment load acts on the piezoelectric actuator 50 and breaks early. The possibility of doing so can be reduced.
Furthermore, since the piezoelectric actuator 50 can be arranged coaxially with the screw shaft 11, the displacement of the piezoelectric actuator 50 can be a pure axial displacement, and a highly accurate fine movement operation can be performed.

  In this way, in the present embodiment, one outer ring 21a of the angular ball bearings 20a, 20b provided with a plurality of piezoelectric actuators 50 arranged in parallel with the expansion and contraction direction and provided with preload is disposed in the housing 27. A piston 51 that presses the outer ring 21b and a spacer 55 that has an arc-shaped cross section in the axial direction that contacts the piston 51 are provided between the piezoelectric actuator 50 and the outer ring 21b. The distance between 21a and 21b is changed by expansion and contraction of the plurality of piezoelectric actuators 50.

  As a result, the angular ball bearings 20a, 20b arranged opposite to each other function as a spring member having a very high rigidity, and a combination of the high rigidity in the compression direction of the piezoelectric actuator 50 and the high rigidity spring member allows the axial fine movement with a rotation mechanism. Since the rigidity of the mechanism 41 can be maintained high, it is possible to realize a stable fine movement operation with high responsiveness. In addition, since the reaction force of the preload acts on the piezoelectric actuator 50 and the fine movement operation can be performed while always applying a compressive load, the piezoelectric actuator 50 can be prevented from being damaged due to the tensile load. Furthermore, since the fine movement operation is performed by the plurality of piezoelectric actuators 50 arranged in parallel with the expansion / contraction direction, it is possible to realize a fine movement operation with higher responsiveness. Further, since the displacement of the piezoelectric actuator 50 is transmitted via the spacer 55, the influence of the variation in the displacement can be reduced, so that a highly accurate fine movement operation can be realized.

Furthermore, in the present embodiment, the piezoelectric actuator 50 is a standardized stacked piezoelectric actuator.
As a result, it is possible to manufacture at a relatively low cost, and it is possible to realize a highly accurate fine movement operation by reducing variation in characteristics. In addition, the piezoelectric actuator 50 can be easily manufactured.
Further, in the present embodiment, preload is applied in advance in a state where the piezoelectric actuator 50 is not energized.
Thereby, even when the displacement amount of the piezoelectric actuator 50 is close to zero, the piezoelectric actuator 50 can be downsized and the cost can be reduced without preload loss. Further, it is only necessary to energize the piezoelectric actuator 50 only when performing the positioning operation, and the energization time is shortened, so that the durability of the piezoelectric actuator 50 can be improved.

Furthermore, in the present embodiment, the fine movement control is performed by feeding back the deviation between the current position recognized by the detection signal indicating the relative movement amount between the base 5 and the moving base 6 from the position sensor 17 and the target position.
Thereby, even when there is a lead error of the screw shaft 11, hysteresis of the piezoelectric actuator 50, etc., highly accurate fine positioning can be performed.

Furthermore, in the present embodiment, the piezoelectric actuator 50 is solidly fitted into the storage hole 52 and the concave hole 54, and is sandwiched between the bottom surfaces and arranged coaxially with the screw shaft 11.
As a result, it is possible to assemble the bearing unit by the same method as the method of assembling the bearing unit only by using the housing 27 that is as long as the piezoelectric actuator 50, and the assembly of the axial fine movement mechanism 41 with the rotation mechanism can be easily performed. In general, it is possible to reduce the cost of the positioning device by reducing the price of the piezoelectric actuator that becomes more expensive as the volume increases.

  Furthermore, in the present embodiment, the inner peripheral surfaces of the inner rings 23a and 23b are fitted to the outer peripheral surface of the screw shaft 11, and the axial movement of the inner rings 23a and 23b is sandwiched between the inner ring engaging portion 29 and the lock nut 32. And the axial movement of the outer ring 21a is restricted to the housing 27 by the outer ring engaging portion 38, and the outer ring 21b is moved in the axial direction by the piezoelectric actuator 50 via the piston 51 and the spacer 55. I did it.

As a result, half of the displacement of the piezoelectric actuator 50 can be made the displacement of the screw shaft 11, and the displacement error of the piezoelectric actuator 50 can be halved to realize a highly accurate fine movement operation.
Further, in the present embodiment, the piezoelectric actuator 50 is disposed so as to press the outer ring 21a which is the non-rotating side of the angular ball bearings 20a and 20b.
Thereby, wiring to the piezoelectric actuator 50 can be performed easily.

In the above embodiment, the piezoelectric actuators 50 are arranged in parallel. However, the present invention is not limited to this, and the piezoelectric actuators 50 may be arranged in series and in parallel.
Specifically, two piezoelectric actuators 50 are inserted into the storage hole 52 and the recessed hole 54, respectively. Each set of piezoelectric actuators 50 is arranged in series with respect to the expansion and contraction direction, and is joined by an adhesive or the like. In addition, you may fix not only with an adhesive agent but with a jig | tool. As a result, two piezoelectric actuators 50 arranged in series are used as a set, and the two sets of piezoelectric actuators 50 are arranged in parallel with the expansion / contraction direction coincided with the axial direction. It is preferable to use the piezoelectric actuator 50 having the same shape and characteristics.

With such a configuration, the stroke length is increased, and the rigidity of the axial fine movement mechanism 41 with the rotation mechanism is increased, so that a fine movement operation with a long stroke and high responsiveness can be realized.
In this case, two piezoelectric actuators 50 are arranged in series and two are arranged in parallel. However, the present invention is not limited to this, and in order to realize a fine movement operation with a long stroke and high response, a larger number of piezoelectric actuators 50 are provided. It can also be arranged in series and more in parallel. The number of piezoelectric actuators 50 may be determined by the required stroke length and rigidity.

  In the above embodiment, the control voltage from the actuator drive unit 49 is amplified by one amplifier and output to each piezoelectric actuator 50. However, the present invention is not limited to this, and the piezoelectric actuator 50 is compatible with each piezoelectric actuator 50. It is also possible to provide the same number of amplifiers as the number of piezoelectric actuators 50 so that the control voltage from the actuator driving unit 49 is amplified by each amplifier and output to the corresponding piezoelectric actuator 50. In this case, by adjusting the gain of each amplifier so that the relationship between the control voltage and the displacement amount of the piezoelectric actuator 50 becomes equal, the characteristics of each piezoelectric actuator 50 can be electrically adjusted. This is the same when the piezoelectric actuators 50 are arranged in series and in parallel.

  In the above embodiment, the inner ring spacer 30 is provided between the opposed inner rings 23a and 23b so as to apply the preload. However, the present invention is not limited to this, and the surfaces on the opposite side of the inner rings 23a and 23b are provided. It is also possible to extend the length corresponding to half the width of the inner ring spacer 30 so that the inner rings 23a and 23b are brought into direct contact with each other.

  In the above-described embodiment, the preload is applied to the angular ball bearings 20a and 20b arranged opposite to each other in advance through the non-energized piezoelectric actuator 50. However, the present invention is not limited thereto, and the piezoelectric actuator 50 is not energized. In some cases, the piezoelectric actuator 50 and the outer rings 21a, 21b or the inner rings 23a, 23b are opposed to each other through a gap so that no preload is generated, and a predetermined voltage is applied to the piezoelectric actuator 50 when the coarse / fine movement positioning device 1 is started. Then, a predetermined preload may be generated in the angular ball bearings 20a and 20b arranged opposite to each other. In this way, in order to give a predetermined preload to the angular ball bearings 20a, 20b, for example, a so-called preload is performed in which the axial length of the piston 51 or the spacer 55 is precisely adjusted according to the amount of preload. Adjustment becomes unnecessary, and precise preload adjustment can be easily performed only by applying a predetermined voltage.

Moreover, in the said embodiment, although comprised so that two rolling bearing apparatuses which consist of one angular ball bearing may be opposingly arranged, it is not restricted to this, One set of several angular ball bearings arrange | positioned in parallel combination Two rolling bearing devices may be arranged opposite to each other.
In the above embodiment, the angular ball bearings 20a and 20b are used as bearings for supporting the screw shaft 11. However, the present invention is not limited to this, and rotation and axial direction that rotate and finely move the support portion of the rotation at high speed. Needless to say, it can be used for the combined movement mechanism of fine movement.

Moreover, in the said embodiment, although the feed screw apparatus was comprised as the ball screw apparatus 13 which screws the screw shaft 11 and the nut 12 through a ball | bowl, it is not restricted to this, The screw shaft 11 and the nut 12 are comprised. It can also be configured as a sliding screw device that is directly screwed.
In the above embodiment, the feedback control is configured to be performed at the time of fine motion control. However, the present invention is not limited to this, and at the time of coarse motion control, feedback control is performed using the deviation between the target position and the current position. Alternatively, the coarse movement operation may be stopped when the deviation becomes a predetermined value or less. In this way, the lead accuracy of the screw shaft 11 can be corrected, the correction amount due to the fine movement operation of the piezoelectric actuator 50 can be reduced, and it is necessary to use the piezoelectric actuator 50 having a larger expansion / contraction amount than necessary. Disappears.

It is sectional drawing of the axial direction fine movement mechanism 41 with a rotation mechanism. 2 is a plan view of the coarse / fine movement positioning device 1. FIG. It is a side view of the coarse / fine movement positioning device. 3 is a block diagram showing a configuration of a control device 45. FIG. It is a flowchart which shows a coarse / fine movement positioning process. It is a figure for demonstrating the fine movement operation | movement of the axial direction fine movement mechanism 41 with a rotation mechanism. It is a figure for demonstrating the attachment structure of the conventional piezoelectric actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coarse / fine movement positioning device 2 Linear guide mechanism 3 Rail 4 Slider 4a Moving base mounting surface 5 Base 6 Moving base 10 Coarse moving mechanism 11 Screw shaft 11a Shaft track groove 12 Nut 13 Ball screw device 14 Drive motor 16 Support bearing 17 Position sensor 18 Scale 20a, 20b Angular contact ball bearings 21a, 21b Outer ring 22a, 22b Outer ring raceway 23a, 23b Inner ring 24a, 24b Inner ring raceway 25a, 25b Ball 26 Fitting shaft 27 Housing 27a Screw hole 29 Inner ring locking part 30 Inner ring spacer 32 Lock Nuts 33 Threaded portion 50 Piezoelectric actuator 38 Outer ring locking portion 51 Piston 39 Cover 40 Clearance 52 Storage hole 53 Relief hole 54 Recess hole 55 Spacer 41 Axial fine movement mechanism 45 with rotation mechanism Controller 46 Control unit 47 Storage unit 48 Motor drive 49 Actuator drive

Claims (3)

Two rolling bearing devices arranged opposite to each other and applied with a preload; a shaft into which each inner ring of the rolling bearing device is fitted; and a plurality of piezoelectric actuators arranged in parallel with respect to the expansion and contraction direction;
The inner ring is fixed to the shaft in the axial direction, one of the outer rings of the rolling bearing device is constrained in the axial direction, and the displacement of the plurality of piezoelectric actuators is between the plurality of piezoelectric actuators and the other of the outer rings. A rotation mechanism is provided, wherein a spacer is provided that can transmit the composite displacement by averaging the variations of the outer ring, and the axial distance between the outer rings is changed by expansion and contraction of the plurality of piezoelectric actuators. Axial fine movement mechanism. A screw shaft rotatably supported by a base; and a nut that is screwed to the screw shaft and is fixed to the moving base. The rotating base is pivoted with respect to the base by the rotation of the screw shaft. Coarse movement mechanism to move in the direction,
Two rolling bearing devices arranged to face each other and applied with a preload, a housing fixed to the base and fitted with respective outer rings of the rolling bearing device, and a plurality of piezoelectric actuators arranged in parallel with respect to the expansion and contraction direction Each inner ring of the rolling bearing device is fitted to the screw shaft, the inner ring is fixed to the screw shaft in the axial direction, one of the outer rings is restrained in the axial direction, A spacer is provided between the piezoelectric actuator and the other outer ring to average the variation of the displacements of the plurality of piezoelectric actuators and transmit their combined displacement, and the distance between the outer rings in the axial direction is provided. A coarse / fine movement positioning device comprising: an axial fine movement mechanism with a rotation mechanism that is changed by expansion and contraction of a plurality of piezoelectric actuators. In claim 2,
A piston is provided between the other outer ring and the spacer,
The coarse / fine movement positioning device characterized in that the spacer has an arcuate cross-sectional shape in contact with the piston.

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