JPH0295181A - Method of driving piezoelectric motor, piezoelectric motor and head driver for disk storage device - Google Patents

Abstract

PURPOSE:To conduct stable fine displacement even by the use of very small voltage, and to improve the accuracy of final positioning by applying DC voltage having mutually reversed polarity to a pair of piezoelectric elements. CONSTITUTION:When AC voltage having phase difference is applied to a pair of piezoelectric elements 2, 3 of a piezoelectric driving unit 1, a driver 6 conducts an elliptic periphery motion, and a body to be driven 7 can be displaced and driven. When DC voltage having mutually reversed polarity is applied to a pair of the piezoelectric elements 2, 3, on the other hand, fine drive is enabled. Accordingly, the body to be driven 7 is displaced and driven largely by AC drive at the time of normalcy, and AC drive is changed over to DC drive at the time of final positioning, thus improving the accuracy of positioning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a piezoelectric motor that drives a driven object using vibration of a piezoelectric element.

[Conventional technology]

A piezoelectric motor applies an alternating current voltage to a piezoelectric element or an electrostrictive element, and uses vibrations generated thereby to drive a driven body. It has been attracting attention in recent years because it utilizes the high energy density of piezoelectric elements and the like.

The driving method can be broadly divided into vibrating piece type and traveling wave type based on the principle. Among the former vibrating piece type, especially
It is described in JP-A-60-200776 and JP-A-61-168025 as being capable of driving in the forward and reverse directions and having high output characteristics. this is,
The basic element of the motor is a piezoelectric drive unit composed of a pair of laminated piezoelectric elements. That is, a piezoelectric drive unit is formed by attaching a pair of laminated piezoelectric elements to a drive body via a displacement combining section made of an elastic body and with the displacement directions of these piezoelectric elements crossing each other.

This is a piezoelectric motor known as a piezoelectric element diagonal arrangement method, and when an alternating current (high frequency) voltage having a phase difference is applied to the pair of piezoelectric elements, the driving body moves along a plane including the intersecting displacement directions. It moves around in an elliptical trajectory. Therefore, when a driven body is pressed against the driving body, the driven body is displaced in one direction due to the friction between them.

Note that if the phase difference of the high frequency voltage is reversed, driving in the opposite direction can be achieved.

Further, since the frequency of the high-frequency voltage is usually set to the mechanical resonance frequency, the driving speed can be varied by keeping this constant and changing the amplitude of the voltage. That is, since the lengths of the long and short axes of the elliptical orbit change, the amount of displacement per vibration changes, while the vibration frequency is constant, so the driving speed changes.

[Problem to be solved by the invention]

By the way, according to the conventional piezoelectric motor described above, the principle is to drive the driven body by the frictional force caused by pressing, so if the driving force is to be increased, the pressing force must be increased.

However, since the above-mentioned frictional force is affected by the surface roughness of the contact surface between the driving body and the driven body, the driven body will not be driven when the applied high-frequency voltage is low, and will only be driven when the voltage exceeds a certain level. There is a phenomenon that it is started. In other words, in order to obtain a predetermined speed, an applied voltage of a certain value or more is required (this is called the minimum starting voltage). This minimum starting voltage becomes unstable due to the surface condition of the contact portion. Furthermore, hysteresis exists between starting and stopping due to the difference between static friction and dynamic friction, and the stopping voltage is lower than the minimum starting voltage.

Therefore, when controlling the speed of a piezoelectric motor, it is difficult to control the speed, especially at low speeds, using only the conventional voltage control by applying an alternating current voltage.

That is, when positioning control is configured using a displacement feedback system according to the prior art, the control of minute displacement drive during final positioning where the deviation voltage becomes small becomes unstable, and there is a problem that positioning accuracy cannot be sufficiently increased.

Further, in the above-mentioned conventional technology, a mechanical spring is used as a means for pressing the driven body against the driving body. Therefore, the pressing force remains approximately constant at all times and cannot be changed during operation.

By the way, this pressing force is correlated with driving force and driving speed, and is an important element for driving performance. for example,
If a large driving force is required, the pressing force may be increased, while if a large speed is required, the pressing force may be decreased.

However, in the conventional technology, since the pressing force cannot be changed, it is difficult to appropriately change the driving force according to the load, and there is a problem that it is difficult to fully demonstrate the performance of the piezoelectric motor. Also, a function that allows the driven object to move freely when the power is cut off (also called an idling function in the case of rotary motors)
This is inconvenient for applications that require

Note that providing an external mechanism that can change the pressing force of a conventional piezoelectric motor, or providing an external clutch or the like that allows the driven body to move freely when the power is cut off, will complicate the mechanism. This is not desirable because it also leads to an increase in size.

In addition, in the conventional technology, the driving direction is only in one direction, that is, only in the direction parallel to the contact surface between the driven body and the driving body (hereinafter referred to as the driving surface), and it is not possible to drive in the direction perpendicular to this. Furthermore, there is a problem in that vertical positioning is also not possible.

The objectives of the present invention are, firstly, to enable micro-drive to improve final positioning accuracy, secondly to enable adjustment of the pressing force, and thirdly to enable the driven body to move freely when the power is cut off. Fourthly, it is an object of the present invention to provide a piezoelectric motor driving method and a piezoelectric motor that can be driven in a direction perpendicular to a driving surface, thereby improving drive performance and control performance.

[Means to solve the problem]

In order to achieve the above-mentioned objects 1 to 4, the first aspect of the present invention is to attach a pair of piezoelectric elements to a driving body through an elastic body and with the displacement directions of the piezoelectric elements crossing each other. a first piezoelectric drive unit having the same configuration as the first piezoelectric drive unit, the drive body being disposed opposite to the drive body of the first piezoelectric drive unit and sandwiching a driven body; a second piezoelectric drive unit, an alternating current voltage generating means for outputting an alternating current voltage having a phase difference to be applied to the pair of piezoelectric elements of each of the piezoelectric drive units; DC voltage generation means for outputting DC voltages of opposite polarity to each other; switching means for switching the output voltages of the AC voltage generation means and the DC voltage generation means to apply them to each of the piezoelectric elements; The piezoelectric motor includes a DC bias supply means for superimposing a DC bias voltage on the applied voltage.

Furthermore, in order to achieve the first, second, and third objects above, the second invention of the present invention provides a second piezoelectric quick-acting unit according to the first invention in the direction of the driven object. The structure is such that the spring is energized.

In addition, in order to achieve both the first and fourth objectives above,
A third aspect of the present invention provides a fixedly supported rotating body in place of the second piezoelectric drive unit according to the first aspect.
The drive body of the piezoelectric drive unit is arranged opposite to the drive body of the piezoelectric drive unit.

In addition, in order to achieve both the first and fourth objectives above, 9
A fourth invention of the present invention is such that the rotating body according to the third invention is elastically biased toward the driven body.

[Effect]

With this configuration, the object of the present invention is achieved by the following effects.

Basically, when an alternating current voltage with a phase difference is applied to a pair of piezoelectric elements of a piezoelectric drive unit, the drive body moves in an elliptical orbit. Therefore, by pressing the driven body against the egg moving body, the driven body can be displaced.

On the other hand, when a DC voltage of opposite polarity is applied to a pair of piezoelectric elements, one of the laminated piezoelectric elements expands in the axial direction, and the other piezoelectric element shortens. These movements are influenced by the action of an elastic body interposed between the drive body and the reaction force of the pressing force acting on the drive body, and cause the drive body to be displaced in the main driving direction. The movement of the driving body at this time is not an elliptical movement, unlike when using an alternating current voltage. Therefore, since the surface condition of the contact portion with the driven body is stable, displacement drive is performed in correlation with the DC voltage. This enables minute drive, so the first objective of improving positioning accuracy can be achieved by driving large displacements using AC drive during normal times and switching to DC drive during final positioning.

Next, when a DC bias voltage is applied to the pair of piezoelectric elements, the stacked piezoelectric elements expand, for example, in the axial direction (the direction in which they are stacked) in accordance with the voltage.

This stretching force is combined via the elastic body and displaces the driving body in the direction of the driven body. On the other hand, when a voltage of opposite polarity is applied, the piezoelectric element shortens.

Therefore, the pressing force can be adjusted by placing piezoelectric drive units or rotating bodies of the same configuration facing each other on opposite sides of the driven body and changing the DC bias voltage, and the second objective described above is achieved. Ru. Further, if the DC bias voltage is made zero, the pressing force becomes zero, so that the driven body can be moved freely when the power is cut off, and the third objective described above is achieved.

In addition, in the case of a configuration in which another piezoelectric drive unit or a rotary body disposed opposite to the piezoelectric drive unit marked - is elastically biased by an elastic body such as a spring, the DC bias of the piezoelectric drive unit marked - Even if the force is changed, the resulting displacement of the driving body is absorbed by the elastic body, so the pressing force does not change.

However, according to this configuration, as described below, the fourth objective of driving displacement in a direction perpendicular to the driving surface is achieved.

That is, by applying a DC voltage, the driving body is displaced in the direction of the driven body, so if the driving body of the piezoelectric drive unit of the same configuration is placed opposite to this driving body with the driven body in between, The driven body can be displaced in a direction perpendicular to the driving surface depending on the balance of displacements of the opposing driving bodies.

In this case, the DC voltages applied to the two pairs of piezoelectric drive units facing each other may have opposite polarities, or may have a difference between them. In the latter case, the amount of displacement can be adjusted according to the difference, and the remaining voltage portion will act as the aforementioned bias voltage. Note that even in the case where piezoelectric drive units or rotating bodies arranged opposite to each other are elastically biased and supported, displacement in a direction perpendicular to the drive surface is possible by the same effect.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows a schematic configuration diagram of an embodiment of the present invention, and FIG. 2 shows details of a piezoelectric drive unit partially in section.

This embodiment is an example of a piezoelectric motor in which two sets of piezoelectric drive units having diagonal piezoelectric elements are arranged facing each other. Each piezoelectric drive unit 1 (in FIG. 1, suffixes a and b are added to identify two opposing sets) includes a pair of laminated piezoelectric elements 2 and 3, and these piezoelectric elements 2, 3 has a driving body 6 attached to the distal end thereof via a displacement composite body 5 as an elastic body. The drive body 6 has a flat drive surface with which the driven body 7 comes into pressure contact.

The pair of piezoelectric elements 2 and 3 are mounted on a mount 4 such that their displacement direction (arrow 8 in the figure) obliquely intersects the drive surface.
Fixed on top. The displacements of the piezoelectric elements 2 and 3 are combined by a displacement combiner 5. This displacement composite body 5 has a structure in which a pair of parallel links using elastic hinges or leaf springs as joints are orthogonally arranged as shown in the figure. The displacement composite body 5 may basically be an elastic body, but considering the opening efficiency, it may be an elastic body formed to be elastically deformable along a plane including the displacement direction of the pair of piezoelectric elements 2 and 3. Preferably the body. One end of each of the parallel links and the piezoelectric elements 2, 3 are connected to the mount 4.
It is fixed by a fixing means such as gluing or tightening with bolts 9 as shown in the figure. In addition, the driving body 6
is made of a wear-resistant material and is replaceably fixed to the displacement composite 5 by fixing means such as screws 10. Furthermore, the mount 4 is fixed to the base 12 by fixing means such as bolts 11.

The piezoelectric drive unit la configured in this way.

1b are arranged to face each other with the driven body 7 in between, as shown in FIG. Note that the driving body 6a.

6b is assembled so as to contact the driven body 7 with zero pressing force.

On the other hand, the piezoelectric elements 2a, 2b, 3a, and 3b are driven by voltages supplied from an AC voltage generator 21, a DC voltage generator 22, and a DC bias generator 23, respectively. The AC voltage generator 21 includes an oscillator 24 that generates a predetermined high frequency voltage, and this high frequency voltage as input,
It is formed to include a phase converter 25 that outputs two high frequency voltages having a phase difference. The DC voltage generators 22 are formed to generate DC voltages of opposite polarity. The outputs of these AC generator 21 and DC generator 22 are switched by switch means 26 using analog switches, and adders 27 and 28 and adders 29 and 3
o is input. A DC bias voltage from a DC bias generator 23 is inputted to each of these adders. The outputs of these adders 27 to 30 are sent to an amplifier 32a.
, 32b, 33a, and each piezoelectric element 2a via 33b.

2b, 3a, and 3b.

The operation of the embodiment configured as described above will be explained with reference to FIGS. 3 and 4. Note that FIGS. 3 and 4 schematically represent the displacement composite body and the driving body of the piezoelectric drive unit 1.

First, the operation of adjusting the pressing force Fh using a DC bias voltage will be described. When the voltage applied to the piezoelectric element 2.degree. 3 is zero (when the power is turned off), the pressing force is zero, so the driven body 7 is free to move without being subjected to any restraining force.

When driving, first, an appropriate DC bias voltage is applied in the direction in which the piezoelectric elements 2 and 3 extend. The displacement of each piezoelectric element at this time is defined as y as shown in FIG. Since the displacement composite body 5 has a parallel link structure as shown in the figure, each minute displacement is transmitted to the tip without interference, and as a result, the driving body 6 approaches the normal direction of the driving surface by Jy. Therefore,
When the mechanical rigidity between the drive unit 1 including the base 12 and the driven body 7 is K, the pressing force Fh is expressed by the following equation.

F h = k −, /'N y By the way, since the displacement y is proportional to the DC bias voltage Vx applied to the piezoelectric elements 2 and 3, the pressing force Fh can be arbitrarily adjusted by the DC bias voltage.

Figure 7 shows the effect of being able to adjust this pressing force.
This will be explained using the experimental example shown in FIG.

These figures are examples of the relationship between the pressing force Fh and high frequency voltage V exerted between the driving body 6 and the driven body 7, and the driving force Fd and driving speed V. From these figures, it can be seen that the driving force Fd that can be generated basically has a relationship of Fd≦μFh (μ: coefficient of friction), but when the pressing force Fh becomes excessive, the driving force Fd starts to decrease. In addition, the driving speed V is the pressing force Fh
necessarily decreases as .

Therefore, according to this embodiment, the pressing force Fh can be changed as necessary, and drive performance and control performance can be fully exhibited.

Next, the operation of driving the driven body 7 by minute displacement by applying a DC voltage will be described. With the DC bias voltage applied as described above, a certain appropriate DC voltage is further applied to the piezoelectric elements 2a, 2b, and a voltage of opposite polarity to the DC voltage is applied to the piezoelectric elements 3a, 3b. For example, as shown in FIG. 4, when a negative DC voltage is applied to the piezoelectric element 2 and a positive voltage is applied to the piezoelectric element 3, the piezoelectric element 2 contracts and the piezoelectric element 3 expands. Each displacement of piezoelectric elements 2 and 3 at this time is
shall be. Since the displacement composite body 5 has a parallel link structure as shown in the figure, each minute displacement is transmitted to the tip without interference, and as a result, the driving body 6 moves -J'i in the direction of the driven surface.
: It will be displaced by x.

Therefore, the driven body 7 is driven to the left in the figure by J'Zx. Since the displacement X of the piezoelectric elements 2 and 3 is proportional to the DC voltage applied to the piezoelectric elements 2 and 3, the displacement of the driven body 7 can be arbitrarily adjusted by the DC voltage value. FIG. 5 is a graph showing the DC voltage values applied to the piezoelectric elements 2 and 3 and the experimental results of the displacement of the driven body at this time. As is clear from this graph, for example, with an applied voltage of ±15 V, it is possible to achieve minute positioning within a range of ±0.5 μm and a resolution on the order of nanometers.

As described above, when driving the driven body 7, a DC bias voltage is first applied to ensure a pressing force.

During long stroke driving, the high frequency voltage of the resonant frequency from the oscillator 24 is passed through the phase converter 25 to +90
° (when driving in the positive direction) or -90° (when driving in the negative direction)
are converted into high-frequency voltages with a phase difference of
By superimposing the DC bias voltage Vx through 7.28°29.30, the power amplifiers 32a, 32b, 33a, 33
The voltage is applied to the piezoelectric elements 2a, 2b, 3a, and 3b via b. Therefore, a voltage as shown in FIG. 6 is applied to the piezoelectric element. At this time, the driving body 6a.

6b vibrates while drawing a circular locus or an elliptical locus (generally a circular locus), and frictionally drives the driven body 7 that comes into contact with it in one direction.

As described above, this high-frequency voltage drive makes it difficult or unstable to perform minute displacement drives required during final positioning. This will be explained in more detail using FIG. 9. This figure shows the case where a constant pressing force is applied by a spring or the like, and the horizontal axis of the graph is the AC applied voltage V at the resonance frequency, and the vertical axis is the speed n when no load is applied. As can be seen from the figure, a minimum starting voltage v, , is required to obtain a predetermined speed. Furthermore, due to the difference between dynamic friction and static friction, hysteresis exists in the characteristics in the range below the voltage v2, making minute displacement drive unstable. Therefore,
In this embodiment, the final positioning is performed using DC drive.

That is, after long stroke driving by applying a high frequency voltage, at the time of final positioning, the switch means 26 is switched, and a positive DC voltage corresponding to the deviation between the target position and the current position is generated from the DC voltage generator 23 according to a command given from the controller 34. and negative DC voltage, respectively, to an adder 27.2.
Output on 8, 29.30. Then, a DC bias voltage is superimposed and applied to the piezoelectric elements 2a, 2b, 3a, 3b via amplifiers 32a, 32b, 33a, 33b. As a result, the driving bodies 6a and 6b are moved by a small displacement in the driving surface direction, and the driven body 7 is driven by a small displacement. By switching the drive voltage during final positioning in this manner, final positioning accuracy can be improved.

Furthermore, even if the load changes during operation, it is possible to adjust the pressing force by changing the DC bias voltage and generate an appropriate driving force. Furthermore, even if the drive body 6 is worn out, the amount of wear can be compensated to a certain extent by pushing out the drive body 6 using a DC bias voltage.

Note that instead of the phase converter 25, a high frequency voltage signal is applied to the piezoelectric elements 2a, 2b, or the piezoelectric elements 3a, 3
A signal switching circuit having a function of switching whether to add the signal to b depending on whether the signal is applied to the positive direction or the negative direction may be used. In this case, the drive efficiency is lower than when a phase converter is used, but it is possible to drive the driven body 7 in the forward and reverse directions.

Further, in the above embodiment, when the power is cut off, the driven body 7
The initial position of the piezoelectric drive units 1a, lb is determined so that the pressing force is zero when the applied voltage is zero, in order to have a function that allows the piezoelectric drive units 1a, lb to move freely (idling function in the case of a rotary motor). However, if this function is not required, it is also possible to assemble the piezoelectric drive units la, lb in advance at a position to apply a predetermined pressing force, and then change the pressing force by the DC bias voltage from this state.

In addition, in this embodiment, since the pressure 11 driving units la and lb are arranged facing each other on both sides of the driven body 7, the driven body It becomes possible to drive the body 7 by a minute displacement in the direction perpendicular to the driving surface. That is, as shown in FIG.
FIGS. 1 and 12 show the relationship between the applied voltage and the driving state. As can be seen from these, according to this example,
Long stroke drive in the X direction by applying an AC voltage, minute displacement drive in the X direction by applying a DC voltage, adjustment of pressing force by a DC bias voltage, and minute displacement drive in the Y direction can be realized. In addition, in FIGS. 11 and 12, A,
B, C, and ΔC are voltage levels, and ω is a high frequency angular velocity.

In the embodiment shown in FIG. 1 (first embodiment), the piezoelectric drive units la and lb are arranged facing each other on both sides of the driven body 7, but as a second embodiment, as shown in FIG. Even when one side is a freely rotating roller 13, the pressing force can be adjusted by the DC bias voltage. However, in this case, although it is possible to realize the driving state shown in FIG. 14, it is not possible to drive the driven body by a minute displacement in the Y direction as in the first embodiment.

Further, as a modification of the first and second embodiments, a third embodiment,
A fourth embodiment is shown in FIGS. 15 and 16.

The third embodiment differs from the first embodiment in that the piezoelectric drive unit 16 on one side is not fixed to the mount 12b, but is fixed by a spring mechanism 14 or the like that acts only in the pressing direction to apply pressing force. be. Further, in the fourth embodiment, the roller 13 of the second embodiment is not fixed to the mount 12b, but is fixed by a spring mechanism 15 or the like that acts only in the direction of the pressing force to apply the pressing force. According to the third and fourth embodiments, although the pressing force cannot be adjusted by the DC bias voltage, it is possible to drive the driven body 7 by a minute displacement in the Y direction.

Next, FIG. 17 shows a specific embodiment of the drive circuit portion of the embodiment in FIG. 1. In the figure, only a portion corresponding to the piezoelectric drive unit 1a on one side is shown, and the other piezoelectric drive unit 1b is omitted because it is the same. Components with the same reference numerals as in FIG. 1 have the same functions and configurations.

The phase converter 25 has a phase delay device 25a and a changeover switch 25b using an analog switch. By switching this changeover switch 25b, the polarity of the phase difference (for example, ±90°) between the high-frequency voltages applied to the pair of piezoelectric elements 2a and 3a can be reversed to switch between positive and negative drive directions. .

The controller 34 includes a controller body 35, a positive/negative determination circuit 36, a minute deviation determination circuit 37, an amplifier 38,
It is formed to include a changeover switch 39 using an analog switch and an integrator 40. Positive/negative judgment circuit 37
is the device deviation signal E composed of the controller main body 35.
The positive/negative drive direction is determined based on the polarity of , and a switching command is output to the changeover switch 25b in accordance with this.

The fine 7JX deviation judgment circuit 27 receives the input position deviation signal E.
is compared with a predetermined standard deviation amount ε, and E≧
When ε, a command to switch the switch means 26 to the AC voltage generator 23 side is output.

On the other hand, the position error signal E is amplified by the amplifier 38, and is inputted to the multipliers 41a and 42a through the changeover switch 39, and further through the integrator 40 or directly. This circuit controls the amplitude of the drive voltage according to the deviation, and when the deviation is small, the selector switch 39 is switched to the integrator 40 side by the judgment signal of the minute deviation judgment circuit 37.
Integral control is performed. Positive/negative judgment circuit 27
゜Minute deviation judgment circuit 28. The integrator 31 is an operational amplifier,
It can be easily configured using resistors, capacitors, etc.

Note that two types of DC voltages, positive and negative, are input from the DC voltage generator 22 to the multipliers 41a and 42a via the switch means 26. Further, the DC bias voltage generator 23 outputs a DC bias voltage according to the signal from the controller main body 35 to adders 28 and 29, and multipliers 41a and 42a
It is designed to be applied to the drive voltage output from the

Because of this configuration, the controller main body 35
The DC bias voltage generator 23 outputs a DC bias voltage that adjusts the pressing force and the displacement in the Y direction. On the other hand, when the deviation signal E is larger than E, the selector switch 25b is switched according to the drive direction determined by the positive/negative determination circuit 36, and thereby the drive direction of the long stroke drive is switched in a direction that reduces the deviation.

That is, when the deviation E is larger than the standard deviation amount ε, the output of the switch means 26 becomes the high frequency voltage from the selector switch 25b, and the difference between this output and the deviation E from the amplifier 38 is
The voltage obtained by multiplying by the multipliers 41a and 42a is superimposed with the DC bias voltage whose voltage value is adjusted by the signal from the controller by the adder 28.29, and is used as a driving voltage to drive the piezoelectric element via the amplifiers 32a and 33a. 2a, 3
applied to a. Then, when the deviation E becomes smaller than the reference deviation amount ε, the output of the switch means 26 becomes the DC voltage from the DC voltage generator 22. In this case, since the displacement of the piezoelectric motor is proportional to the applied DC voltage, an integrator 40 is placed in the feedback loop to configure a position feedback system that makes the steady position error zero. , the DC voltage is multiplied by a value obtained by integrating the deviation signal E from the amplifier 38 by multipliers 41a and 42a, and a DC bias voltage is superimposed thereon by adders 28 and 29 to obtain a drive voltage.

Note that, generally, in order to perform power-saving driving, piezoelectric elements 2,
A coil L is connected in parallel to the piezoelectric element 3, whereby a resonant circuit is formed by the capacitance of the piezoelectric element itself and the coil L. In this case, if a DC voltage is applied as is, the coil will become short-circuited. In such a case, a capacitor C may be inserted in series with the coil L in order to make the DC drive or bias of the present invention effective.

The first to third embodiments described above are examples in which the driven body 7 is linearly driven. It goes without saying that the present invention can also be applied to devices that rotate quickly.

Next, a description will be given of an embodiment in which the function of making it possible to drive a drive surface by a minute displacement in the vertical direction (Y direction) is applied to a drive device for a read/write head of a magnetic disk or an optical disk.

FIG. 18 shows a simplified configuration diagram of a disk head drive device using the fourth embodiment.

As shown in the figure, a slider 51 including a read/write head is mounted on a head support arm 52 as a driven body.
It is attached to one end of a magnetic or optical disk (hereinafter referred to as a disk) and is provided close to the recording surface of the disk. The arm 52 is sandwiched between rollers 54 and 55 A
B, which is sandwiched between the point and the roller 13 and the piezoelectric drive unit 1
It is spatially supported at two points. In addition, arm 5
The lateral guide No. 2 is not shown.

The embodiment shown in FIG. 19 is a specific configuration diagram of the disk head drive device shown in FIG. 18 viewed from the horizontal direction. roller 5
4 is resiliently biased toward the roller 55 by a spring mechanism 56. Further, the piezoelectric motor section including the piezoelectric drive unit 1 and the rollers 13 is covered by a casing 57.

Although not shown, inside the casing 57, there is provided a mechanism for discharging dust generated due to wear of the sliding portion of the drive body 6 and the like. Further, by maintaining the inside of the casing 57 at negative pressure, the above-mentioned dust can be prevented from leaking to the outside.

With this configuration, the piezoelectric drive unit 1 can move the arc 52 in the radial direction of the disk 53 to control the position of the slider 51. Also,
By slightly displacing the position of point B vertically (in the Y direction), the gap between the slider 51 and the disk 53 can be adjusted.

That is, when seeking to move a long stroke to a target track, a long stroke drive is performed by applying an AC voltage, and when following the target track, a minute displacement drive is performed by applying a DC voltage. X direction) positioning can be performed.

In addition, the arm 52 can be driven by a small displacement in the direction perpendicular to the drive surface (Y direction in the figure) using the DC bias voltage. ) can be positioned. That is, when it is desired to move the head vertically upward, the DC bias voltage applied to the piezoelectric element is reduced, the arm 52 at point B is moved downward, and the head is moved vertically upward. When it is desired to move the head vertically downward, the applied DC bias voltage may be increased, contrary to the above.

Therefore, with the above function, firstly, when the disk is at rest, it is possible to prevent the slider and the disk from coming into close contact with each other due to moisture or the like by forcing the head to float.

Second, the slider flying height can be actively controlled.

Third, it is possible to prevent the head from hitting the disk during seek.

FIG. 20 shows a horizontal view of the disk head drive device constructed using the first embodiment. Since the piezoelectric drive units la and lb are arranged to face each other, the piezoelectric drive unit l
It is also possible to adjust the pressing force between a, lb and the arm 52.

FIG. 21 is a modification of the embodiment shown in FIG. 18, in which two identical piezoelectric motors are used instead of the rollers 54 and 55 that support point
It is set up as a set. According to this, the vertical positioning of the head can be performed while preventing the arm 52 from swinging in the Y direction, ie, pitching.

FIG. 22 is a modification of the embodiment shown in FIG. 20, and the same effect as the embodiment shown in FIG. 21 can be obtained.

〔Effect of the invention〕

As explained above, since the present invention includes a configuration in which DC voltages of opposite polarity are applied to a pair of piezoelectric elements, stable minute displacement can be performed even with a minute voltage, and final positioning is possible. It is possible to improve accuracy.

In addition, since it includes a configuration that applies a DC bias voltage to a pair of piezoelectric elements, it is possible to displace the driving body in a direction perpendicular to its driving surface, and piezoelectric drive units or rotating bodies with the same configuration can be arranged facing each other. According to the invention, by adjusting the DC bias voltage, the pressing force can be varied, and the immediate action performance and control performance can be improved.

Furthermore, since the pressing force becomes zero when the power is cut off, the driven body can be moved freely.

In addition, according to a piezoelectric drive unit having the same configuration arranged opposite to a piezoelectric drive unit indicated by -, or a piezoelectric drive unit having the same configuration or a rotating body elastically biased, there is a direct current bias. By adjusting the voltage balance, it is possible to drive small displacements in the direction perpendicular to the drive surface, such as the one required for driving read/write heads of magnetic or optical disks.
It can be equipped with a dimensional positioning function.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the first embodiment of the present invention, FIG. 2 is a partial detailed diagram of the first embodiment, FIG. 3 is a schematic diagram showing the displacement of the tip of the piezoelectric drive unit when a DC bias voltage is applied, and FIG. Fig. 4 is a schematic diagram showing the displacement of the tip of the piezoelectric drive unit when DC voltage is applied, Fig. 5 is a graph showing the displacement of the driven body of the piezoelectric motor when DC voltage is applied, and Fig. 6 is a graph showing the displacement of the driven body of the piezoelectric motor when DC voltage is applied. A diagram showing a high frequency voltage waveform with a bias voltage superimposed,
Figures 7, 8, and 9 are graphs showing drive characteristics during normal AC drive, Figures 10, 11, and 12, respectively.
The figure is a diagram explaining the voltage applied to each piezoelectric element of the first embodiment and the driving state at that time, FIG. 13 is a configuration diagram of the main parts of the second embodiment, and FIG. A diagram explaining the voltage applied to the piezoelectric element and the driving state at that time, FIG. 15 is a configuration diagram of the main parts of the third embodiment, FIG. 16 is a diagram of the main parts of the fourth embodiment, and FIG. 18 and 19 are diagrams showing a specific embodiment of a drive circuit according to one embodiment, and FIGS. 20 and 21 are main part configuration diagrams of an embodiment using a disk head drive device of the present invention. , and FIG. 22 are block diagrams of main parts of other embodiments using a disk head drive device according to the present invention. =36 1... Piezoelectric drive unit, 2, 3... Piezoelectric element, 4
... Mount, 5... Displacement composite body, 6... Drive body, 7... Driven body, 13... Roller, 21... AC voltage generator, 22... DC voltage generation Vessel, 23...
DC bias voltage generator, 26... switch means, 2
7-30... Adder, 32a, b... Amplifier, 33a
, b...Amplifier, 51...Slider, 52...Head support arm, 53...Disk, 57...Casing.

Claims (7)

[Claims] 1. A piezoelectric motor is driven by a piezoelectric drive unit, which has a pair of piezoelectric elements attached to a drive body through an elastic body and with the displacement directions of the piezoelectric elements crossing each other, to drive the displacement of a driven body that is pressed against the drive body. In the method,
The pressing force of the driving body is adjusted by superimposing a DC bias voltage on the driving voltage applied to the piezoelectric element, and during long stroke driving, the driving voltage is an AC voltage having a phase difference between the pair of piezoelectric elements, A method for driving a piezoelectric motor, characterized in that during minute displacement driving, DC voltages having different polarities are switched as the driving voltage. 2. a first piezoelectric drive unit configured by attaching a pair of piezoelectric elements to a drive body through elastic bodies and with the displacement directions of the piezoelectric elements crossing each other, and having the same configuration as the first piezoelectric drive unit; A second piezoelectric drive unit in which a driving body is disposed opposite to the driving body of the first piezoelectric drive unit and sandwiching a driven body.
a piezoelectric drive unit; an alternating current voltage generating means for outputting alternating current voltages having a phase difference between each other and applied to a pair of piezoelectric elements in each of the piezoelectric drive units; DC voltage generation means for outputting a DC voltage of polarity; switching means for switching the output voltages of the AC voltage generation means and the DC voltage generation means to be applied to each of the piezoelectric elements; A piezoelectric motor comprising a DC bias supply means for superimposing a DC bias voltage on the voltage. 3. a first piezoelectric drive unit configured by attaching a pair of piezoelectric elements to a drive body through elastic bodies and with the displacement directions of the piezoelectric elements crossing each other, and having the same configuration as the first piezoelectric drive unit; a second piezoelectric drive unit in which a drive body is disposed opposite to the drive body of the first piezoelectric drive unit, sandwiching a driven body, and elastically biased toward the driven body; AC voltage generation means that outputs AC voltages having a phase difference between each other, which are applied to a pair of piezoelectric elements of the drive unit; and DC voltages that output DC voltages of mutually opposite polarity that are applied to a pair of piezoelectric elements of each piezoelectric drive unit. generating means; switching means for switching the output voltages of the alternating current voltage generating means and the direct current voltage generating means and applying the same to each of the piezoelectric elements; and a direct current generating means for superimposing a direct current bias voltage on the voltage applied to each of the piezoelectric elements. A piezoelectric motor comprising bias supply means. 4. A piezoelectric drive unit includes a pair of piezoelectric elements attached to a driving body through elastic bodies and with the displacement directions of the piezoelectric elements crossing each other, and a driven body is sandwiched between the piezoelectric drive unit and the driving body of the piezoelectric drive unit. a rotating body that is fixedly supported; an AC voltage generating means that outputs an AC voltage having a phase difference between the piezoelectric elements to be applied to the pair of piezoelectric elements of each of the piezoelectric drive units; DC voltage generation means for outputting DC voltages of opposite polarity to each other; switching means for switching the output voltages of the AC voltage generation means and the DC voltage generation means and applying the same to each of the piezoelectric elements; DC bias supply means for superimposing a DC bias voltage on the applied voltage. 5. A piezoelectric drive unit includes a pair of piezoelectric elements attached to a drive body through elastic bodies and with the displacement directions of the piezoelectric elements crossing each other, and a driven body is sandwiched between the piezoelectric drive unit and the drive body of the piezoelectric drive unit. a rotating body that is arranged and elastically biased in the direction of the driven body; an AC voltage generating means that outputs an AC voltage having a phase difference to be applied to a pair of piezoelectric elements of each of the piezoelectric drive units; DC voltage generation means for outputting DC voltages of opposite polarity to be applied to a pair of piezoelectric elements of the piezoelectric drive unit; and DC voltage generation means for switching the output voltages of the AC voltage generation means and the DC voltage generation means and applying them to each of the piezoelectric elements. A piezoelectric motor comprising: a switching means for applying a DC bias voltage to a voltage applied to each piezoelectric element; and a DC bias supply means for superimposing a DC bias voltage on a voltage applied to each piezoelectric element. 6. A head support arm having a slider including a read/write head attached to its tip; and arm holding means for holding the head support arm so that the slider is close to the recording surface of a magnetic or optical disk and can move freely in the radial direction. and the head support arm is a driven body.
, 3, 4, or 5, a head drive device for a disk storage device, wherein the head support arm is provided with a moving direction parallel to a plane including an intersecting axis of the piezoelectric drive unit. . 7. 7. The piezoelectric motor according to claim 2, wherein at least a contact portion between the driving body and the driven body of the piezoelectric drive unit is housed in a container maintained at negative pressure.