JP2004197864A - Frictional driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frictional driving device capable of being applied to an optical disc exposing device and the like realizing the feeding of high accuracy. <P>SOLUTION: A moving body is movable by a driving shaft 10, and the driving shaft 10 is driven by a plurality of rollers 13 coaxially mounted at equal angles in the circumferential direction with respect to a center axis of the driving shaft 10. The rollers 13 are respectively held by driven shafts 16, and one end part of each driven shaft 16 is fixed to a housing 11 through a first piezoelectric element 17 expanding and contracting in the direction to press an outer periphery of the driving shaft 10, and a second piezoelectric element 18 expanding and contracting in the direction to press the roller 13 in the outer peripheral tangent direction of the driving shaft 10. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a friction drive device for moving a moving body forward and backward by rotating a drive shaft, and more particularly to a movement in an optical disc master exposing apparatus having a slide table which is a moving body for accurately exposing a track pitch to an optical disc master. The present invention relates to a friction drive device applied to a body drive unit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a slide table device for exposing an optical disc master, there have been many inventions for realizing high-precision feeding (Patent Documents 1 to 3).
[0003]
As a slide table device for exposing an optical disc master, an air slide type slide table device provided with a slide table that can be moved forward and backward via a static pressure bearing is used. For driving the slide table, a voice coil type linear motor is generally used, and a closed loop control system using an interference laser length measuring device or a linear scale as a position detector is employed. In the case of a semiconductor inspection device or the like that requires a stationary state, a ball screw or the like is used to drive the slide table because rigidity in the feed direction is required.
[0004]
With the recent increase in the density of optical discs, an exposure method using an electron beam or the like from a conventional laser beam has emerged in order to achieve higher-resolution exposure. Accurate feeding is required.
[0005]
The twist roller method of the friction drive mechanism can realize a small lead that cannot be obtained with other mechanisms by minimizing the intersection angle between the drive shaft and the driven shaft, and high positioning resolution is expected For this reason, various mechanisms have been proposed in patent documents and non-patent documents as next-generation feed mechanisms.
[0006]
For example, the invention described in Patent Literature 4 includes a shaft body, and an advancing / retreating component through which the shaft body is relatively rotatably and advancing / retreating, and a barrel-shaped revolving / retracting component that is rotatably connected to the shaft body in the advancing / retreating component body. A plurality of rollers are arranged in the circumferential direction, and these rollers are rotatably supported between the advance / retreat component body and the preloading plate via balls at both end surfaces. At least one, and at least one of the preloading plate and the roller end face, is configured to support the ball with a conical ball supporting recess into which the ball is rotatably fitted. In addition, by providing an elastic body that urges the preload plate to the roller side and also urges it in the circumferential direction, it has high resistance to disturbances, has no speed irregularity, can perform stable feeding, and can stop when the drive source is stopped. The device is capable of improving performance.
[0007]
The invention described in Patent Literature 5 provides a friction advance / retreat drive device that statically supports a slide body serving as a table with respect to a base with a static pressure linear bearing and slidably drives the slide body with respect to the base. The friction advance / retreat driving device includes a main shaft that is driven to rotate, and a plurality of rollers provided around the main shaft and in contact with each other at an inclined angle, and a preload means that applies a preload to the main shaft to the roller is provided. Therefore, a slide table device for an optical disk mastering device which can perform stable feeding without speed unevenness, is resistant to disturbances, improves resolution, and thereby enables high-density writing.
[0008]
The invention described in Patent Document 6 includes a main shaft, a roller that comes into rolling contact with the outer periphery of the main shaft at an inclined angle, and a slide body that moves together with the roller as the main shaft rotates. The transmission is transmitted to the main shaft after being decelerated by the motor, and the reduction gear is configured to be decelerated by transmitting the rotation from the first and second drive shafts to the friction wheel, thereby reducing the influence of the rotational unevenness of the rotary drive source and In addition, the phase shift in the rotation transmission system is reduced, and precise positioning is enabled.
[0009]
The invention described in Patent Document 7 is an input drive shaft, a roller that is a plurality of driven shafts each having an axis that is in rolling contact with the outer periphery of the drive shaft and that is inclined at a small cross angle with respect to the drive shaft axis, A housing adapted to circumscribe the roller with respect to the drive shaft and to move in the axial direction by an axial component of a friction force generated by the roller due to rotation of the drive shaft. The roller is held by the housing via the radial and thrust hydrostatic bearings, and the thrust hydrostatic bearing surface facing the roller end face of the housing is lined with respect to a line passing through the drive shaft and each axis of the roller. It is divided into two symmetrical semicircles, and the static pressure supplied separately to each semicircle is adjusted to stably maintain the crossing angle.
[0010]
[Patent Document 1]
JP-A-2002-25128
[Patent Document 2]
JP-A-2002-92973
[Patent Document 3]
JP 2002-279700 A
[Patent Document 4]
JP-A-8-184360
[Patent Document 5]
JP-A-11-195247
[Patent Document 6]
JP-A-11-195248
[Patent Document 7]
Japanese Patent Publication No. Hei 6-23598
[0011]
[Problems to be solved by the invention]
By the way, in the case of the invention described in Patent Document 4, since the rollers are arranged equiangularly (120 degrees) with respect to the drive axis, they are formed on the fixed plate and the opposing plate that support the roller end faces, respectively. Due to the mechanical position error of the conical ball supporting recess, the angle between each roller axis and the drive shaft tends to vary.
[0012]
This does not pose a problem when the angle between the roller shaft and the drive shaft is large, in other words, when the lead (the distance traveled in the axial direction) is relatively large (for example, several mm). When the angle between the shaft and the shaft is small, in other words, when the lead is small (for example, several hundred μm), if there is a variation in the angle between each roller shaft and the drive shaft, the gap between the drive shaft and the roller of the driven shaft is reduced. In this case, a slip due to a read error occurs, which is a disturbance in closed-loop control, which is not preferable in terms of control, and when applied to exposure of a master optical disc, the track pitch accuracy and the like deteriorate, resulting in a problem in that the exposure quality is unfavorable.
[0013]
Further, in a conventional twist roller type friction drive device, since the driven shaft rotates, there is a problem in supporting the same. The existence of a gap is indispensable for support by sliding contact, and it is impossible to make the rolling element a perfect circle with support by rolling contact. Therefore, there is a problem that the crossing angle of the rollers cannot always be stably maintained. In the invention described in Patent Document 7, the problem is solved by supporting the roller by static pressure, but the components are expensive.
[0014]
Further, in the invention described in Patent Document 4, an elastic body that urges the preload plate toward the roller and also urges the roller in the circumferential direction is provided. An elastic body is formed by providing an elastic body in the communicating hole as a position where the hole having the threaded part provided in the hole and the hole provided in the preload plate are connected, and tightening the set screw of the threaded part provided in the body of the advance / retreat component. Utilizing the compressive deformation force of In such a configuration, it is not possible to quantitatively confirm the current preload amount of the roller shaft, so trial and error is required to obtain an appropriate preload amount, and aging due to wear of the roller or the shaft. This makes it difficult to readjust the preload, and there is a problem that the preload amount is not reproducible at the time of component replacement and the assemblability is poor.
[0015]
In the invention described in Patent Literature 5, the roller is provided with a preload means for applying a preload to the main shaft. However, a straight line is provided between the fixing portion of the hydrostatic linear motion bearing fixed to the base and the main shaft of the friction advance / retreat drive device. It may be assembled in a state where there is an error in the performance. In this case, when the slide body moves in the feed direction, the straightness error is absorbed between the roller having the lowest rigidity and the main shaft only by being pre-pressed and fixed. Is changed with the moving position.
[0016]
The driving force acting between the drive shaft and one roller in the drive shaft direction is F = μN where μ is the dynamic friction coefficient between the outer periphery of the drive shaft and the roller, and N is the preload. Therefore, the driving force generated around each roller and the outer periphery of the driving shaft also varies, thereby causing the driving force to vary. Therefore, the variation in the angle between the axis of each roller and the driving shaft is synergistic. Then, a slip occurs between the rollers of the drive shaft and the driven shaft, which is a disturbance in closed-loop control, which is not preferable in control.When applied to an optical disk master exposure or the like, track pitch accuracy and the like deteriorate, It is not preferable in terms of exposure quality.
[0017]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a friction drive device which can be applied to an optical disk master exposure apparatus or the like which can realize high-accuracy feeding without the above-mentioned conventional problems.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 includes a plurality of driven shafts having an axis line which comes into rolling contact with a drive shaft and its outer periphery and which is inclined at a small crossing angle with respect to the axis of the drive shaft. And a housing that externally supports the roller with respect to the drive shaft and that is axially moved by an axial component of a frictional force generated by the roller due to rotation of the drive shaft. A moving body that moves with the housing, a guide mechanism that guides the moving body in the axial direction of the drive shaft, and a position detection unit that detects a feed position of the moving body. A first piezoelectric element that supports one end of the driven shaft by the housing and expands and contracts the other end in a direction in which the roller presses the outer periphery of the drive shaft and a tangential direction on the outer periphery of the drive shaft. First output means for controlling the voltage applied to the first piezoelectric element, supported by the housing via a second piezoelectric element that expands and contracts in the direction in which the piezoelectric element is pressed; Angle calculating means for calculating the tilt angle of the shaft, second output means for applying an output voltage corresponding to the calculated calculated angle to the second piezoelectric element, and rotation of a feed drive motor for rotating the drive shaft A current lead amount calculating means for calculating a current lead amount based on an origin detection signal per rotation in a rotary encoder for detecting an angle and a position detection signal of the position detecting means; An angle adjusting means including a voltage correcting means for increasing / decreasing a voltage applied to the second piezoelectric element is provided. With this configuration, processing and assembly errors are reduced. To compensate for the variation in the intersection angle between each driven shaft and the drive shaft caused by the mechanical position error caused by the above, so that the angle between the axis of each roller and the drive shaft can be precisely adjusted. As a result, slippage due to a read error does not occur between the rollers of the drive shaft and the driven shafts, stable feed control can be realized, and feed accuracy can be improved.
[0019]
According to a second aspect of the present invention, in the friction drive device according to the first aspect, the driven shaft is made of a composite material of an elastic body and a rigid body. Installation can be performed easily and reliably.
[0020]
According to a third aspect of the present invention, in the friction drive device according to the first or second aspect, a radial magnetic bearing in which a roller is formed by a repulsive force of a magnet magnetized in a radial direction of the roller, and an axis of the roller Characterized in that it is held on the driven shaft via a thrust magnetic bearing constituted by a repulsive force of a magnet magnetized in the direction, and with this configuration, the roller is driven by the driven shaft via a radial magnetic bearing and a thrust magnetic bearing. Because it is held in a non-contact manner, vibrations generated by rolling elements used in conventional angular bearings and the like are eliminated, stable leads can be performed, stable feed control is possible, and feed accuracy is further improved. Can be.
[0021]
According to a fourth aspect of the present invention, in the friction drive device according to the third aspect, a rare-earth permanent magnet is used as a magnet constituting the radial magnetic bearing and the thrust magnetic bearing. Therefore, a large repulsive force can be obtained, so that the apparatus can be made compact and inexpensive.
[0022]
According to a fifth aspect of the present invention, in the friction drive device according to the first, third or fourth aspect, the driven shaft, the roller, the drive shaft, and the housing are made of a non-magnetic material. In addition, since the magnet can be prevented from attracting to other parts, disturbance to the pressing control and the angle control of the driven shaft can be eliminated, and the feeding accuracy can be further improved.
[0023]
According to a sixth aspect of the present invention, in the friction drive device according to the first aspect, the first output means is turned on / off by a constant voltage circuit, an output signal of the constant voltage circuit being input, and an external signal. A change-over switch, a deformation amount measuring means provided on the first piezoelectric element, and a comparison between a pressing expansion / contraction setting signal which is an output signal of the change-over switch and a current pressing expansion / contraction amount which is an output signal of the deformation amount measuring means. The servo control means performs servo control.This configuration reproduces the pressing (preload) operation of the roller to the outer periphery of the drive shaft and the angle correction operation of correcting the intersection angle between each driven shaft and the drive shaft. Since it can be performed efficiently, stable feed control can be realized and feed accuracy can be improved.
[0024]
According to a seventh aspect of the present invention, in the friction drive device according to the first aspect, a first adjustment plate is provided on the housing so as to be able to press the first piezoelectric element, and the first adjustment plate and the first piezoelectric element are provided. A first adjusting screw via the element enables adjustment of a position of the driven shaft pressed in the outer peripheral direction of the drive shaft, and further, a second adjustment plate is provided on the housing so as to be able to press a second piezoelectric element; The position of the driven shaft in the direction of pressing tangentially on the outer periphery of the drive shaft can be adjusted by a second adjustment screw via the second adjustment plate and the second piezoelectric element. With this configuration, an angle correction operation can be performed even at a large intersection angle, so that stable feed control can be realized in a wide range of read conditions, and versatility as a feed component can be increased. That.
[0025]
According to an eighth aspect of the present invention, in the friction drive device according to the first aspect, the first output means is turned on / off by a variable voltage circuit, an output signal of the variable voltage circuit being input, and an external signal. A changeover switch, and a deformation amount measuring means for detecting a deformation amount in a pressing direction of the driven shaft provided on an outer peripheral portion of the elastic body of the driven shaft; a pressing setting signal which is an output signal of the changeover switch; It is characterized by comprising servo control means for performing servo control by comparing the current pressing amount, which is an output signal, with the preload servo by means of a signal in which the pressing amount of the roller against the drive shaft is replaced by the deformation amount of the driven shaft. In this way, it is possible to instantly set the appropriate pressing conditions, it is easy to readjust the pressing due to aging due to the wear of the rollers or drive shaft, and the reproducibility of the pressing amount when replacing parts Can be like become good, improvement of the assembling property is reduced.
[0026]
According to a ninth aspect of the present invention, in the friction drive device according to the first aspect, the first output unit includes one digital / analog converter, a deformation measuring unit, and an output signal of the digital / analog converter. It is characterized by comprising a servo control means for performing servo control by comparing the pressing setting signal which is the current pressing amount which is the output signal of the deformation amount measuring means, by this configuration, the pressing amount to the drive shaft of the roller Since the pressing servo is performed with the signal replaced with the amount of deformation of the driven shaft, it is possible to instantly set appropriate pressing conditions, and it is easy to readjust the pressing due to aging due to wear of the roller or drive shaft, and parts It is possible to improve the assemblability, for example, the reproducibility of the pressing amount at the time of replacement is improved.
[0027]
According to a tenth aspect of the present invention, in the friction drive device according to the first aspect, a plurality of digital / analog converters each independently providing a first output unit with a pressure setting signal to the first piezoelectric element, An amount measuring unit, and a servo control unit that performs servo control by comparing a pressing setting signal that is an output signal of the plurality of digital / analog converters with a current pressing amount that is an output signal of the deformation amount measuring unit. According to this configuration, the pressing servo is performed with a signal obtained by replacing the pressing amount of the roller against the driving shaft with the deformation amount of the driven shaft, and the pressing set value to each pressing unit is independently given. There is no variation in the driving force generated on the outer circumference of each roller and the drive shaft, and stable feed operation can be realized even with long stroke drive, and feed control accuracy and assemblability can be improved. .
[0028]
According to an eleventh aspect of the present invention, in the friction drive device according to the first aspect, the second output means is a digital / analog converter, a deformation measuring means provided on a second piezoelectric element, and the digital / analog converter. It is characterized by comprising servo control means for performing a servo operation by comparing a pressing / contracting setting signal which is an output signal of an analog converter and a current pressing / contracting amount which is an output signal of the deformation amount measuring means. , The roller presses (preloads) the outer circumference of the drive shaft, and the angle correction operation that corrects the intersection angle between each driven shaft and the drive shaft can be performed with good reproducibility, thus achieving stable feed control and improving feed accuracy. Can be achieved.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0030]
FIG. 1 is a plan view of a friction drive device for explaining Embodiment 1 of the present invention, FIG. 2 is a right side view of the friction drive device of Embodiment 1, and FIG. 3 is a part of the friction drive device of Embodiment 1. FIG. 4 is a sectional view taken along line AA in FIG. 3 of the first embodiment.
[0031]
As shown in FIG. 2, a base 1 provided on an anti-vibration mechanism (not shown) including a pneumatic servo mounter is fixed at a lower end to the base 1 while being separated in a direction perpendicular to a feeding direction. A plurality of columns 2 are erected, and a moving body 4 is fixed to an upper end of each column 2 via a rolling bearing (for example, a sphere, a cylindrical roller, etc.) 3 arranged in the feed direction. Below the left end of the moving body 4, there is provided a position detecting means 7 comprising an optical linear encoder or the like whose output is composed of A-phase and B-phase pulses of an arbitrary resolution.
[0032]
In this example, the position detecting means 7 comprises a light receiving section 5 and a scale 6 for measuring the position in the feed direction, and the scale 6 is fixed to the moving body 4 via a mounting plate 8. 5 is fixed to the base 1 via the mounting plate 9. In addition, as a mounting structure of the light receiving unit 5 and the scale 6, a structure in which the light receiving unit 5 is fixed to the moving body 4 and the scale 6 is fixed to the base 1 may be adopted.
[0033]
As shown in FIGS. 3 and 4, a housing 11 having a hole 11 a through which the drive shaft 10 is inserted is provided below the protrusion 4 a extending in the feed direction of the moving body 4 via a fixing plate 12. Is fixed. As shown in FIG. 4, a plurality of rollers 13 (three rollers are illustrated in this example) that are in rolling contact with the outer periphery of the drive shaft 10 via opposed rolling bearings (eg, angular bearings) 14. Are arranged concentrically and equiangularly in the circumferential direction with respect to the center axis of the drive shaft 10. As shown in FIGS. 3 and 5, each roller 13 is held on a driven shaft 16 made of a composite material of an elastic body (for example, a phosphor bronze rod or the like) 15a and a rigid body 15b.
[0034]
As shown in FIG. 4, one end (the right end in FIG. 3) of the driven shaft 16 extends and contracts in the housing 11 in the direction in which the roller 13 presses the outer periphery of the drive shaft 10 (three in this example). And a plurality of (three in this example) second piezoelectric elements that expand and contract in a direction to press the roller 13 in a direction tangential to the outer periphery of the drive shaft 10. It is fixed to the housing 11 via the element 18.
[0035]
As shown in FIG. 3, the right end of the drive shaft 10 is stepped, and the outer periphery of the first stage 10 a is fitted to the inner periphery of the rolling bearing 20. That is, the outer periphery of the first step 10a is fixed to the base 1 and has a pair of rolling bearings (for example, a pair of rolling bearings) whose outer rings are fixed concentrically to the through holes 19a in the bearing housing 19 having the stepped through holes 19a at the top. 20). An inner peripheral portion of the rolling bearing 20 and a screw portion provided on the drive shaft 10 are fixed by a bearing stopper 21.
[0036]
Further, the second stage 10b of the drive shaft 10 is fixed to the right cylindrical hole of the bearing housing 19, and is provided with a rotary encoder (for example, the output of which is A-phase and B-phase pulses obtained by dividing the circumference by several thousands and one rotation per rotation). A coupling (for example, Oldham type) 24 is connected to a drive shaft of a feed drive motor 23 having a Z-phase pulse 22 generated repeatedly.
[0037]
On the other hand, the outer periphery of the stepped portion 10c at the left end of the drive shaft 10 is fitted concentrically with a rolling bearing (for example, a deep groove ball) fixed to a through hole 25a provided at the top of a bearing housing 25 fixed to the base 1. The outer ring of the rolling bearing 26 is configured to be movable in the axial direction.
[0038]
In the first embodiment of the above configuration, an appropriate energizing voltage is applied to the second piezoelectric element 18 and the first piezoelectric element from terminal leads (not shown) of the first piezoelectric element 17 and the second piezoelectric element 18. When the voltage is applied in the order of 17, the outer periphery of the roller 13 and the outer periphery of the drive shaft 10 come into rolling contact with each other at a certain angle θ, as shown by the dotted line in FIG. In this state, when power is supplied from a terminal (not shown) of the feed drive motor 23, the contact point between the outer periphery of the roller 13 and the outer periphery of the drive shaft 10 moves spirally, and the moving body 4 is movable in the feed direction. Become. At this time, the driven shaft 16 itself does not rotate, and the outer ring of the rolling bearing 14 rotates.
[0039]
Further, the moving amount L (the amount of lead) by which the drive shaft 10 moves the moving body 4 per rotation can be expressed by the following equation (Equation 1), where D is the outer dimension of the drive shaft 10.
[0040]
(Equation 1)
L = π · D · sin θ ≒ π · D · θ
θ = sin ^-1 {L / (π · D)}
For example, the relationship between the intersection angle and the lead amount L when D = 30 mm is linear as shown in the log-log graph of FIG.
[0041]
Next, a control system for adjusting the angle of the driven shaft 16 according to the first embodiment will be described with reference to the block diagram of FIG.
[0042]
A CPU (central processing unit) 30 to which a Z-phase pulse signal 28 generated once in one round of the rotary encoder 22 and an A-phase pulse signal 29 of the position detecting means 7 for detecting a feed position are input as interrupt signals. A ROM (read only memory) 31 in which an operation program is written, a RAM (random access memory) 32 for storing data, and an A-phase of the position detecting means 7 using a rising edge of the Z-phase pulse signal 28 as a trigger signal. A counter (for example, a synchronous counter) 33 for counting the number of pulses of the pulse signal 29 is connected.
[0043]
Further, the CPU 30 outputs a drive signal of a switch 35 for turning on / off an output signal of a constant voltage circuit 34 for outputting a fixed constant voltage, and is connected to each of the first piezoelectric elements 17 via the switch 35. The signal is output to the drive amplifier 36. The constant voltage circuit 34, the switch 35 and the drive amplifier 36 constitute a first output means 37. Further, the CPU 30 is connected to a data input unit 38 for inputting the read amount data L and the set allowable error data ε.
[0044]
The output signal of the CPU 30 is output to a drive amplifier 40 connected to each second piezoelectric element 18 via a digital / analog (D / A) converter 39 for converting digital data into an analog signal. Here, the D / A converter 39 and the drive amplifier 40 constitute a second output unit 41.
[0045]
In the first embodiment, the angle adjusting means 42 is constituted by the entire structure shown in FIG.
[0046]
An operation flow based on the control of the CPU 30 in the first embodiment of the configuration will be described with reference to flowcharts shown in FIGS.
[0047]
The CPU 30 reads the previously input read amount data L and the set permissible error data ε (S1), waits for a command signal 45a from the host computer (not shown) of the entire apparatus (S2), and starts the rotation of the feed drive motor 23. When the command signal 45a is received from the host computer later, the angle calculating means 46, which is a function provided in the CPU 30, calculates the intersection angle θ based on the equation (1) (S3). Thereafter, the drive signal of the switch 35 is turned off, the signal to each first piezoelectric element 17 is turned off, and the pressing on the drive shaft 10 is released (S4).
[0048]
9, digital data corresponding to the intersection angle θ (see FIG. 5) calculated by the angle calculation means 46 is output to the D / A converter 39 (S 5). Then, a displacement voltage corresponding to the calculated intersection angle θ is applied to the second piezoelectric element 18 to press the driven shaft 16 in a tangential direction on the outer periphery of the drive shaft 10, and then further to the drive signal to the switch 35. Is turned on, an output signal of the constant voltage circuit 34 set to an appropriate voltage is output to the first piezoelectric element 17 via the drive amplifier 36, and presses the driven shaft 16 toward the drive shaft 10 ( S6).
[0049]
In the above state, the CPU 30 sets the number of pulses Ni of the A-phase pulse signal 29 (i = a, b, c: the number of drive amplifiers 36 and the number of D / A converters 39) with the rising of the Z-phase pulse signal 28 as a trigger signal. The present read amount calculation means 47 is a function provided in the CPU 30 for calculating the movement amount by multiplying the count output data of the counter 33 which counts the number of times (S7) and multiplying by the data relating to the output pulse resolution of the position detection means 7. Then, the current lead amount Li is obtained (S8), and the difference data ΔLi from the set lead L is calculated (S9).
[0050]
If the difference data ΔLi is equal to or smaller than the preset allowable error data ε (Yes in S10), the angle data θi is stored in the RAM 32 (S11). On the other hand, when the difference data ΔLi is larger than 0 when the difference is larger (No in S10), the calculated angle data is sequentially increased by a minute amount Δθh set to, for example, the minimum resolution of the D / A converter 39 ( S12) If ΔLi is smaller than 0, the calculated angle data is sequentially reduced by a small amount Δθh (S13). This operation is repeatedly performed by the voltage correction means 48 provided in the CPU 30 until ε ≧ ΔLi.
[0051]
The operation flow is a subroutine. In FIG. 7, the operation is sequentially performed for each drive amplifier 36 and each D / A converter 39. When all the operations are completed, the drive signal of the switch 35 is turned off, and the first operation is performed. The signal to the piezoelectric element 17 is turned OFF and released (S14). Digital data corresponding to each stored angle data θ is output to the D / A converter 39 (S15), and thereafter, the drive signal of the switch 35 is turned on and the signal to the first piezoelectric element 17 is turned on. Then, the driven shaft 16 is pressed (S16).
[0052]
Here, the CPU 30 takes in the count output data of the counter 33 which has counted the number of pulses Nk of the A-phase pulse signal 29 again with the rising of the Z-phase pulse signal 28 as a trigger signal (S17), and outputs the output pulse resolution of the position detecting means 7. Is multiplied to obtain the current movement amount Lk (S18), the difference data ΔLk from the setting lead L is calculated (S19), and it is confirmed that the difference data ΔLk is equal to or smaller than the preset allowable error data ε. (Yes in S20), the setting completion signal 45b is turned on and transmitted to the host computer (not shown), and the operation is completed (S21).
[0053]
According to the configuration of the first embodiment, even if the intersection angle formed between the driven shafts 16 and the drive shafts 10 varies due to mechanical position errors due to machining, assembly errors, and the like, each driven shaft 16 Can be corrected.
[0054]
FIG. 10 is a cross-sectional view illustrating a configuration of a bearing portion of a driven shaft according to Embodiment 2 of the present invention. In the following description, members corresponding to those already described are denoted by the same reference numerals, and detailed description is omitted.
[0055]
In FIG. 10, the center outer periphery of a rigid body 15b constituting a driven shaft 16 and the inner periphery of a roller 13 fitted to the rigid body 15b are coaxially magnetized in the radial direction, and the same poles are opposed to each other. The magnets 50a and 50b are provided so as to form a radial magnetic bearing 51 having a small clearance. Further, a fixing plate 52 screwed to one end of the rigid body 15b and the other end of the rigid body 15b, and both ends of the roller 13 opposed thereto are magnetized coaxially in the axial direction of the roller 13, and The magnets 53a and 53b are provided so that the same poles are opposed to each other, thereby forming a thrust magnetic bearing 54 having a small clearance.
[0056]
In the bearing structure, since the roller 13 is held in non-contact with the driven shaft 16 in the radial direction and the thrust direction by the repulsive force of the magnet, the roller 13 is held in non-contact, such as an angular bearing. There is no vibration or the like generated in the rolling elements used in the above, and stable lead driving can be realized at low cost.
[0057]
If the magnet in the second embodiment is formed of a rare-earth permanent magnet, the rare-earth permanent magnet is a small-sized magnet that can provide a large repulsion force, and thus the device can be made small.
[0058]
In the second embodiment, the components of the driven shaft 16, the rollers 13, the drive shaft 10, and the housing 11, which are components other than the magnet constituting the friction drive unit, are made of a non-magnetic material. It is possible to prevent the attraction force to the parts, and to eliminate disturbance to the pressing control and the angle control of the driven shaft 16.
[0059]
FIG. 11 is a cross-sectional view showing a cross-sectional state similar to FIG. 4 for explaining a supporting portion of a drive shaft and a driven shaft in Embodiment 3 of the present invention.
[0060]
The relationship between the applied voltage and the amount of displacement of the first piezoelectric element 17, which is a component of the first embodiment, generally has a hysteresis characteristic as shown in FIG. Therefore, when the voltage applied to the first piezoelectric element 17 is relatively small, there is no problem because the amount of residual displacement Dp at the time of pressing and releasing is very small, but when the applied voltage is relatively large, in other words, If the amount of pressing on the drive shaft 10 (generally referred to as preload) is increased, the residual displacement Dp is increased, so that it may not be possible to release the drive completely.
[0061]
Therefore, in the third embodiment, as shown in FIG. 11, deformation amount measuring means 55 such as a strain gauge for detecting the deformation amount by, for example, a change in resistance value is provided on the side surface of each first piezoelectric element 17 in the expansion and contraction direction. The servo control is performed by comparing the output signal of the deformation amount measuring means 55 with the set voltage of the constant voltage circuit 34.
[0062]
FIG. 13 is a block diagram showing a configuration of a control system for controlling the amount of deformation of each first piezoelectric element 17 according to the third embodiment. The output signal of the constant voltage circuit 34 is such that a drive signal is output from the CPU 30 and ON. The output signal of the constant voltage circuit 34 is input at the time, and is output to the differential amplifier 57 via the switch 56 connected to GND (0 V) at the time of OFF. The output signal of each deformation amount measuring means 55 is input to a bridge circuit 58 for detecting a change in resistance value, the output signal is input to an amplifier 59 for amplifying a small signal, and the output signal is input to a differential amplifier 57, In the differential amplifier 57, the output signal of the constant voltage circuit 34 connected to the switch 56 is multiplied by the 0 V volt (GND) signal of the circuit.
[0063]
Further, the output signal of the differential amplifier 57 is input to the drive amplifier 36 via the compensation circuit 60 and the gain adjuster 61, and the first servo control means 62 is configured by the circuit configuration from the switch 56 to the drive amplifier 36. The output signal is output to the first piezoelectric element 17.
[0064]
The frequency characteristic of the displacement amount in each first piezoelectric element 17 with respect to the input signal to each drive amplifier 36 is a secondary system as shown in FIG. A phase margin of 40 degrees or more and a gain margin of 15 dB or more, which are system stability index values, are set.
[0065]
According to the configuration of the third embodiment, even if the voltage applied to the first piezoelectric element 17 is relatively large, in other words, even if the pressing amount of the roller 13 against the drive shaft 10 is large, the first servo control unit 62 Since the output signal of the constant voltage circuit 34 serving as the target value, the 0V (GND) signal of the circuit, and the output signal from the deformation amount measuring means 55 are compared to converge on the target value, the residual signal described in FIG. The displacement Dp does not occur.
[0066]
For the same reason, the second piezoelectric element 18 also has a hysteresis characteristic. Therefore, when a large read amount is set, the correction operation by the voltage correction unit 48 described in the first embodiment takes time.
[0067]
Therefore, similarly to the first piezoelectric element 17, the amount of deformation of the second piezoelectric element 18 is detected on the side of the second piezoelectric element 18 in the expansion and contraction direction by changing the resistance value, as shown in FIG. A second deformation amount measuring means 65 such as a strain gauge is provided, and as shown in FIG. 15, a configuration similar to the configuration described with reference to FIG. 13 using the output signal of the D / A converter 39 as a target value is adopted. Second servo control means 67 is provided. Description of the configuration is the same as that shown in FIG.
[0068]
In the configuration shown in FIG. 15, similarly to the configuration shown in FIG. 13, the output signal of the D / A converter 39 to be the target value and the output signal from the second deformation amount measuring unit 65 are compared and converged to the target value. Therefore, the residual displacement Dp described with reference to FIG. 12 does not occur.
[0069]
In each of the above embodiments, the pressing adjustment range and the intersection angle adjustment range of the driven shaft 16 and the driving shaft 10 are limited to within the maximum expansion and contraction amount of the first piezoelectric element 17 and the second piezoelectric element 18, and therefore, for example, are large. In the case of the read setting condition, it cannot be handled.
[0070]
Therefore, the fourth embodiment of the present invention can cope with a large read setting condition. Embodiment 4 will be described with reference to FIG.
[0071]
As shown in FIG. 16, near the first piezoelectric elements 17 in the housing 11, a first guide portion 70 is provided in a direction in which the driven shaft 16 is pressed by the concave portion of the housing 11, and the first guide portion 70 is provided on the first guide portion 70. A first adjusting plate 71 having a substantially crank shape is fitted, one end of the first adjusting plate 71 is connected to the first piezoelectric element 17, and the other end of the first adjusting plate 71 is connected to the housing 11. The first adjustment screw 72 provided can be pressed, and with this configuration, the first adjustment screw 72 screwed in the direction of pressing the driven shaft 16 allows the roller 13 to press the drive shaft 10 in the direction of pressing. Position adjustment is made possible.
[0072]
Similarly, in the vicinity of each second piezoelectric element 18, a second guide portion 73 is provided in a concave portion of the housing 11 in a direction to press the drive shaft 10 in a tangential direction on the outer periphery thereof, and the second guide portion 73 is provided with a second guide portion 73. Of the second adjustment plate 74 is connected to the second piezoelectric element 18, and the other end of the second adjustment plate 74 is provided in the housing 11. With this configuration, the pressing position can be adjusted by the screw 75 in the tangential direction of the outer periphery of the drive shaft 10 with the roller 13 by the second adjusting screw 75 screwed in the direction of the tangential direction of the outer periphery of the drive shaft 10. To make it possible.
[0073]
According to the configuration of the fourth embodiment, before performing the angle correction operation described in the first embodiment with respect to a large lead condition to be set, the first adjustment plate 71 and the second adjustment plate 74 are manually moved. The first adjustment screw 72 and the second adjustment screw 75 adjust the position near the setting lead so as to fall within the maximum expansion and contraction amount of each of the first piezoelectric elements 17 and each of the second piezoelectric elements 18. An angle correction operation can be performed later.
[0074]
The first to fourth embodiments have a configuration in which the amount of expansion and contraction of the first piezoelectric element 17 is set according to the command value without directly controlling the pressing force (hereinafter referred to as preload) of the roller 13 on the drive shaft 10. However, the current preload amount of the roller 13 with respect to the drive shaft 10 cannot be quantitatively confirmed. Therefore, in the following embodiment, a configuration in which control is performed based on a preload of the drive shaft 10 of the roller 13 will be described.
[0075]
First, a fifth embodiment will be described with reference to FIGS.
[0076]
The first output means 37 includes a variable voltage circuit 78 and a changeover switch 56 whose one terminal is connected to 0V and the other terminal receives an output signal of the variable voltage circuit 78 and is turned on / off by an external signal. Further, as shown in FIG. 17, the elastic member 15a constituting the driven shaft 16 is provided on the outer peripheral portion between the rotation support point portion and the support portion of the roller 13 to detect the amount of deformation of the driven shaft 16 in the pressing direction. (E.g., a strain gauge for detecting the amount of deformation based on a change in resistance value) 79, a pressing setting signal that is an output signal of the changeover switch 56, and a current pressing signal that is an output signal of the deformation measuring means 79. A servo control unit 80 for performing servo control by comparing the amount is provided. The basic configuration of the servo control means 80 is the same as the configuration described with reference to FIG.
[0077]
In the fifth embodiment, the amount of preload of the roller 13 provided on each driven shaft 16 to the drive shaft 10 is detected as the amount of deformation of the driven shaft 16 in the pressing direction. In this case, the pressing is performed within the elastic deformation of the elastic body 15 a of the driven shaft 16, and it goes without saying that the relationship between the voltage applied to the first piezoelectric element 17 and the amount of preload is linear.
[0078]
Further, as a sixth embodiment, as shown in FIG. 19, the CPU 30 (see FIG. 7) replaces the first output means 37 with the variable voltage circuit 78 and the changeover switch 56 in the fifth embodiment shown in FIG. The configuration is such that the connected D / A converter 81 is connected to the servo control means 80, and the pressing setting signal which is the output signal of the D / A converter 81 and the current signal which is the output signal of the deformation measuring means 79. The servo control is performed by comparing the amount of pressing.
[0079]
The sixth embodiment is configured to output digital data such that the output of the D / A converter 81 becomes 0 V when the pressure is released when the angle is adjusted. For example, appropriate preload setting condition data is stored in the ROM 31 (see FIG. 7). If the preload is described as a constant in the program to be executed, an appropriate preload can be set instantaneously, and there is no need to perform readjustment work of the preload due to aging due to wear of the roller 13 or the drive shaft 10.
[0080]
In the configuration of the sixth embodiment, since only one pressing setting signal to each first piezoelectric element 17 is given, the deformation amount at the time of pressing varies due to, for example, processing variation of the driven shaft 16 or a bridge circuit. Alternatively, if there is a variation in the strain gauge used for the deformation amount measuring means 79, the same preload amount may not be obtained.
[0081]
Embodiment 7 will be described as a configuration for avoiding this. The basic configuration of the seventh embodiment shown in FIG. 20 is the same as the configuration of the sixth embodiment shown in FIG. 19, and the first output means 37 gives the pressure setting signal to each first piezoelectric element 17 independently. Servo control for comparing a plurality of D / A converters 83 and performing a servo control by comparing a pressing setting signal which is an output signal of each D / A converter 83 with a current pressing amount which is an output signal of each deformation amount measuring means 79. And means 80.
[0082]
In the seventh embodiment, for example, the relationship between the amount of pressing and the amount of deformation of the driven shaft 16 is previously acquired and grasped, and different pressing setting signals can be output from the plurality of D / A converters 83.
[0083]
【The invention's effect】
As described above, according to the friction drive device of the present invention, it is possible to correct the variation of the intersection angle between each driven shaft and the drive shaft caused by a mechanical position error due to a machining or assembly error. Because the angle between the axis of each roller and the drive shaft is precisely set, there is no slippage between the rollers of the drive shaft and each driven shaft due to lead error, and stable feed control is achieved. And the feed accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a plan view of a friction drive device for describing Embodiment 1 of the present invention.
FIG. 2 is a right side view of the friction drive device according to the first embodiment.
FIG. 3 is a vertical cross-sectional view showing a part of the friction drive device according to the first embodiment;
FIG. 4 is a sectional view taken along line AA in FIG. 3 of the first embodiment.
FIG. 5 is an explanatory diagram of a relationship between a roller and a drive shaft in the embodiment.
FIG. 6 is an explanatory diagram of a relationship between an intersection angle and a lead amount on a drive shaft according to the embodiment.
FIG. 7 is a block diagram illustrating a configuration of a control system for performing angle adjustment according to the first embodiment.
FIG. 8 is a flowchart illustrating an operation flow based on control of a CPU according to the first embodiment.
FIG. 9 is a flowchart of a subroutine in the operation flow of FIG. 8;
FIG. 10 is a cross-sectional view illustrating a configuration of a bearing portion of a driven shaft according to a second embodiment of the present invention.
FIG. 11 is a cross-sectional view illustrating a support portion of a drive shaft and a driven shaft according to a third embodiment of the present invention.
FIG. 12 is a diagram showing a relationship between an applied voltage and a displacement amount of the piezoelectric element according to the embodiment.
FIG. 13 is a block diagram showing a configuration of a control system related to deformation amount control of a first piezoelectric element in a third embodiment.
FIG. 14 is a diagram showing a frequency characteristic of a displacement amount in the piezoelectric element with respect to an input signal to the drive amplifier according to the embodiment;
FIG. 15 is a block diagram showing a configuration of a control system for controlling the amount of deformation of a second piezoelectric element according to a third embodiment.
FIG. 16 is a right side view of a friction drive device according to a fourth embodiment of the present invention.
FIG. 17 is a vertical cross-sectional view showing a part of a friction drive device according to a fifth embodiment of the present invention;
FIG. 18 is a block diagram illustrating a configuration of a control system for performing angle adjustment according to a fifth embodiment.
FIG. 19 is a block diagram showing a configuration of a control system for performing angle adjustment in a sixth embodiment.
FIG. 20 is a block diagram illustrating a configuration of a control system for performing angle adjustment according to a seventh embodiment.
[Explanation of symbols]
4 Moving body
7 Position detection means
10 Drive shaft
11 Housing
12 Fixing plate
13 rollers
15a elastic body
15b rigid body
16 driven shaft
17 First piezoelectric element
18 Second piezoelectric element
22 Rotary encoder
23 Feed drive motor
30 CPU
37. First Output Means
41 Second output means
42 Angle adjusting means
46 Angle calculation means
47 Current lead amount calculation means
48 Voltage correction means
51 Radial magnetic bearing
54 Thrust Magnetic Bearing
55, 65, 79 Deformation amount measuring means
70 First Guide
71 First adjustment plate
72 First adjustment screw
73 Second Guide
74 Second adjustment plate
75 Second adjustment screw

Claims (11)

A roller provided on a plurality of driven shafts having rolling axes that are in rolling contact with the drive shaft and the outer periphery thereof and having a small crossing angle with respect to the drive shaft, and the roller with respect to the drive shaft. A housing that is circumscribed and that is axially moved by an axial component of frictional force generated by the roller due to the rotation of the drive shaft, a moving body that moves with the housing, A friction drive device comprising: a guide mechanism that guides in the axial direction of a drive shaft; and a position detection unit that detects a feed position of the moving body.
One end of the driven shaft is supported by the housing, and the other end is a first piezoelectric element that expands and contracts in a direction in which the roller presses the outer periphery of the drive shaft, and a direction in which the other end presses in a tangential direction on the outer periphery of the drive shaft. First output means for supporting the housing via a second piezoelectric element which expands and contracts, and further controlling a voltage applied to the first piezoelectric element; and inclination of the driven shaft with respect to a set lead amount for feeding. Angle calculating means for calculating an angle, second output means for applying an output voltage corresponding to the calculated calculated angle to the second piezoelectric element, and detecting a rotation angle of a feed drive motor for rotating the drive shaft. Current lead amount calculating means for calculating a current lead amount based on an origin detection signal per rotation of the rotary encoder and a position detection signal of the position detecting means; Friction drive, characterized in that by comparing the set read amount with the angle adjusting means comprises a voltage correction means for increasing or decreasing the voltage applied to the second piezoelectric element. 2. The friction drive device according to claim 1, wherein the driven shaft is made of a composite material of an elastic body and a rigid body. The roller is formed by a radial magnetic bearing constituted by a repulsive force of a magnet magnetized in a radial direction of the roller and a thrust magnetic bearing constituted by a repulsive force of a magnet magnetized in an axial direction of the roller. The friction drive device according to claim 1, wherein the friction drive device is held by the driven shaft. 4. The friction drive device according to claim 3, wherein a rare earth permanent magnet is used as a magnet constituting the radial magnetic bearing and the thrust magnetic bearing. 5. The friction drive device according to claim 1, wherein the driven shaft, the roller, the drive shaft, and the housing are made of a non-magnetic material. The first output means includes a constant voltage circuit, a changeover switch to which an output signal of the constant voltage circuit is input and which is turned on / off by an external signal, and a deformation amount measurement means provided on the first piezoelectric element. And servo control means for performing servo control by comparing a pressing / contracting setting signal which is an output signal of the changeover switch with a current pressing / contracting amount which is an output signal of the deformation amount measuring means. A friction drive as described. A first adjusting plate is provided on the housing so as to press the first piezoelectric element, and the drive shaft on the driven shaft is rotated by a first adjusting screw via the first adjusting plate and the first piezoelectric element. The second adjustment plate is provided on the housing so as to be able to press the second piezoelectric element, and the second adjustment plate and the second piezoelectric element are provided in the housing. The friction drive device according to claim 1, wherein a position on the driven shaft in a direction of pressing in a tangential direction on an outer periphery of the drive shaft can be adjusted by a second adjusting screw via the second adjustment screw. The first output means includes a variable voltage circuit, a changeover switch to which an output signal of the variable voltage circuit is input and which is turned on / off by an external signal, and an outer peripheral portion of an elastic body of the driven shaft. Servo control means for providing a deformation amount measuring means for detecting a deformation amount in a pressing direction, and performing servo control by comparing a pressing setting signal which is an output signal of the changeover switch with a current pressing amount which is an output signal of the deformation amount measuring means; The friction drive device according to claim 1, wherein the friction drive device comprises: The first output means includes a digital / analog converter, a deformation measuring means, a pressing setting signal which is an output signal of the digital / analog converter, and a current pressing which is an output signal of the deformation measuring means. 2. The friction drive device according to claim 1, wherein the friction drive device comprises a servo control unit that performs servo control by comparing the amount. The first output means includes a plurality of digital / analog converters for independently applying a pressure setting signal to the first piezoelectric element, a deformation amount measuring means, and an output signal of the plurality of digital / analog converters. 2. The friction drive device according to claim 1, further comprising servo control means for performing servo control by comparing a certain pressing setting signal with a current pressing amount which is an output signal of the deformation amount measuring means. A digital / analog converter, a deformation measuring unit provided on the second piezoelectric element, a pressing / expanding setting signal which is an output signal of the digital / analog converter, and the deformation measuring. 2. The friction drive device according to claim 1, further comprising servo control means for performing a servo operation by comparing an output signal of the means with a current amount of pressing and expanding.

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