JP2003211090A - Drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive device which realizes the speed control of a coupling member with which the dead zone from the halt state up to the start of operation of the coupling member can be controlled small and the power consumption can be suppressed. <P>SOLUTION: A 1st drive circuit 151 generates a 1st drive signal of a predetermined frequency; a 2nd drive circuit 152 generates a 2nd drive signal of a predetermined frequency different from the 1st drive signal; a control part 22 fixes either the 1st drive signal or the 2nd drive signal; and the drive speed of the coupling member 30 is controlled by varying the other driving signal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device,
In particular, the present invention relates to a driving device suitable for driving an XY moving stage, a photographing lens of a camera, a projection lens of an overhead projector, a lens of binoculars, and the like.

[0002]

2. Description of the Related Art Conventionally, an engaging member to which a photographing lens or the like is attached is coupled to a rod-shaped driving member so as to have a predetermined frictional force, and a piezoelectric element is fixed to one end of the driving member. A drive device including an impact type piezoelectric actuator is known. For example, FIG. 17 is a diagram showing a schematic configuration of a driving device for adjusting the photographing lens position of the camera.

The drive device 100 shown in FIG. 17 includes a piezoelectric element 101, which is an electromechanical conversion element, and a piezoelectric element 10.
A rod-shaped driving member 102 driven by 1, an engaging member 103 coupled to the driving member 102 with a predetermined frictional force,
A drive circuit 104 for applying a drive voltage to the piezoelectric element 101 is provided.

The piezoelectric element 101 expands and contracts according to the drive voltage applied from the drive circuit 104, and one end in the expansion and contraction direction is fixed to the support member 105 and the other end is the drive member 102. It is fixed to one end in the axial direction. The engaging member 103 has a photographing lens L, which is an object to be driven, fixed to a predetermined position, and is movable on the driving member 102 along the axial direction.

The drive circuit 104, as shown in FIG.
It is composed of a waveform generator 107 and a power amplifier 108. The waveform generator 107 generates a drive voltage composed of a rectangular wave of 0 to 5 V and inputs the drive voltage to the power amplifier 108,
The power amplifier 108 amplifies the drive voltage supplied from the waveform generator 107 into a drive voltage having a rectangular wave of 0 to 10 V, and applies it to the piezoelectric element 101.

In the driving device 100 having such a configuration, the duty ratio D (D =
A drive voltage having a rectangular waveform as shown in FIG. 19A, in which B / A) is 0.25, is applied to the piezoelectric element 101. The driving method using this driving voltage utilizes the amplitude transmission characteristic and the phase transmission characteristic due to the mechanical resonance characteristic of the driving member 102 coupled to the piezoelectric element 101 that constitutes the impact type piezoelectric actuator.

FIG. 20 (a) is a diagram showing the amplitude transfer characteristic, in which the vertical axis represents the amplitude of the driving member 102 and the horizontal axis represents the driving frequency fd with respect to the mechanical resonance frequency fr of the driving member 102.
Represents the ratio (fd / fr) of 20B is a diagram showing a phase transfer characteristic, in which the vertical axis represents the phase and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 102. The frequency fd1 (see FIG. 19B) of the fundamental wave signal included in the drive voltage before and after the lowest mechanical resonance frequency fr1 of the plurality of resonances and the frequency fd2 of the second harmonic (see FIG. 19C). And fd1 <f
By setting r1 <fd2, the mechanical response of the driving member 102 with respect to the harmonic signal component of the frequency fd3 of the third harmonic or higher is reduced. Then, by utilizing the unimodal characteristic representing the distribution having only one mode of mechanical resonance, an appropriate mechanical displacement response to the fundamental wave signal and the second harmonic wave signal is obtained, and the fundamental wave and the second harmonic wave are further obtained. By changing the phase relationship between the drive voltage and the drive shaft, the drive shaft amplitude, duty ratio D, drive frequency fd, amplitude transfer characteristic, and amplitude are set so that the mechanical displacement of the drive shaft finally becomes a sawtooth waveform as shown in FIG. The desired mechanical load speed of the impact type piezoelectric actuator is obtained by setting the phase transfer characteristics.

Further, as the operation of the driving device 100, when the driving voltage is repeatedly applied to the piezoelectric element 101, the engagement member 103 is in the feeding direction (the direction away from the piezoelectric element 101) due to the expansion and contraction of the piezoelectric element 101. It moves together with the drive member 102 in the direction of arrow a (see FIG. 17). That is, at the rising portion C where the mechanical displacement is slow as shown in FIG. 19D, the driving member 102 is gradually expanded, so that the friction coefficient between the engaging member 103 and the driving member 102 is increased, and the engaging member is increased. While 103 moves in the feeding direction together with the driving member 102, the driving member 102 abruptly contracts at the steep falling portion D, so that the engaging member 1
03 and the driving member 102 have a small friction coefficient, and even if the driving member 102 moves in the return direction (the direction opposite to the arrow a), the engaging member 103 slips on the driving member 102 and stays at substantially the same position. It will be. Therefore, when a driving voltage having a waveform as shown in FIG. 19A is repeatedly applied to the piezoelectric element 101, the engaging member 103 moves intermittently in the direction of arrow a.

Further, when the engaging member 103 is moved in the return direction, the duty ratio D of the drive voltage is changed so that the rising portion C shown in FIG. Part D should have a slow fall. As a result, at the rising portion C where the mechanical displacement is steep, the driving member 102 expands rapidly in the feeding direction, so that the friction coefficient between the engaging member 103 and the driving member 102 becomes small, and the engaging member 103 is driven. Member 1
On the other hand, the driving member 102 is gradually contracted at the gradual falling portion D while slipping on 02 and staying at substantially the same position, so that the friction coefficient between the engaging member 103 and the driving member 102 becomes large, and The coupling member 103 is the driving member 102.
At the same time, it moves in the return direction (the direction opposite to the arrow a). Therefore, the engaging member 103 intermittently moves in the direction opposite to the arrow a.

[0010]

However, in the above-described conventional driving device, the amplitude transfer characteristic and the phase transfer characteristic are the characteristics achieved by the mechanical design of the impact type piezoelectric actuator, so that the cost and size are reduced. It is not something that can be freely designed due to the constraints. Further, as the drive signal, its amplitude and duty ratio D can be manipulated, and the composite ratio of the amplitude of the fundamental wave and the second harmonic can be changed, but even if the duty ratio D is changed, the phase remains the same. It is difficult to manipulate the phase relationship because it does not change. Therefore, it is necessary to set the phase relationship in the mechanical design of the impact type piezoelectric actuator, but in this case as well, it is not possible to freely design due to constraints such as cost reduction and size reduction.

In order to solve such a problem, the applicant drives the impact-type piezoelectric actuator by adding different drive signals to a plurality of electrodes of the piezoelectric element 101 constituting the impact-type piezoelectric actuator by adding them respectively. We propose a method to do this (Japanese Patent Application No. 2001-357660). In this case, as a method for controlling the driving speed of the engagement member 103, a phase difference speed control method for changing the mutual phase relationship of a plurality of driving signals applied to the piezoelectric element 101, and a method for applying the same to the piezoelectric element 101 are used. This is performed by any of the voltage speed control methods in which a plurality of drive voltages are simultaneously changed.

In the former phase difference speed control method, the dead band from the stopped state of the engagement member 103 to the start of the operation is small, but since the drive signal whose voltage is always constant is applied to the piezoelectric element 101, There is a problem that the power consumption is constant and increases regardless of the driving speed of 101.

In the latter voltage speed control method, the piezoelectric element 1
The average power consumption is smaller than that of the phase difference speed control method because the drive voltage applied to 01 is increased or decreased.
There is a problem that the dead zone becomes large from the stop state of 03 to the start of operation.

The present invention has been made to solve the above problems, and the speed of the engaging member is such that the dead zone from the stopped state to the start of operation of the engaging member is small and the power consumption can be suppressed. It is an object of the present invention to provide a drive device that can realize a control method.

[0015]

According to a first aspect of the present invention, there is provided an electromechanical conversion element that expands and contracts when a drive signal is applied, and a support fixed to one end of the electromechanical conversion element in the expansion and contraction direction. A member, a drive member fixed to the other end of the electromechanical conversion element in the expansion / contraction direction, an engagement member engaged with the drive member with a predetermined frictional force, and a drive circuit for driving the electromechanical conversion element In a drive device that relatively moves the support member and the engagement member by expanding and contracting the electromechanical conversion element at different speeds, a first drive signal having a predetermined frequency is generated. Drive means, second drive means for generating a second drive signal having a predetermined frequency different from the first drive signal, and one of the first drive signal and the second drive signal. Drive signal Constant, and characterized by comprising a speed control means for controlling the driving speed of the engaging member by varying the other of the drive signals.

According to the present invention, the first drive signal and the second drive signal
By fixing one of the drive signals of the drive signal and making the other drive signal null, the electromechanical conversion element repeats simple vibration at a predetermined drive speed, and the frictional force between the drive member and the engaging member is reduced. The engaging member is lowered and its position is fixed by dynamic friction. Then, the driving speed of the engaging member is controlled by changing the other driving signal, and since the position of the engaging member is fixed by the dynamic friction, it is possible to immediately respond to the change of the other driving signal. The dead zone from the stopped state of the engaging member to the start of the operation can be reduced.

When the drive signals of the first drive means and the second drive means are always constant, the power consumption becomes high, but one of the first drive signal and the second drive signal is used. Since the drive signal of is fixed and the other drive signal is changed, the power consumption can be suppressed low.

According to a second aspect of the present invention, the one drive signal is one of the first drive means and the second drive means when the drive speed of the engagement member is set to the maximum. It is characterized in that it is generated by the one with lower power consumption.

According to the present invention, normally, if the drive signal is always fixed, the power consumption increases, but when the drive speed of the engaging member is set to the maximum, the first drive means and the second drive means are operated. It is possible to fix the drive signal generated by the one with lower power consumption to suppress the power consumption.

According to a third aspect of the present invention, the first drive signal and the second drive signal are rectangular wave signals,
The speed control means changes a voltage level of one of the first drive means and the second drive means,
Alternatively, the other drive signal is changed by thinning out the number of pulses.

According to the present invention, the first drive signal and the second drive signal are rectangular wave signals, and the speed control means is
Changing the voltage level of one of the first drive means and the second drive means, or the first drive means and the second drive means
It is possible to change the drive signal of the other drive by thinning out the pulse number of one of the drive means.

According to a fourth aspect of the present invention, the one drive signal is a rectangular wave having a duty ratio D of 0.5.

According to the present invention, since one drive signal is a rectangular wave having the duty ratio D of 0.5, the electromechanical conversion element makes simple oscillation even when the other drive signal is 0. The engagement member can be stopped by dynamic friction.

According to a fifth aspect of the present invention, the first drive signal and the second drive signal are signals having the same frequency, and the duty ratio D of the other drive signal is 0.
It is characterized by being a rectangular wave other than 5.

According to the present invention, in the drive device in which the first drive signal and the second drive signal are signals having the same frequency, and the duty ratio D of the other drive signal is not 0.5. Can also be applied.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram schematically showing the basic structure of a drive device including an impact type piezoelectric actuator according to an embodiment of the present invention. In FIG. 1, the drive device 10 includes a drive unit 12, a drive circuit 14 that drives the drive unit 12, a member sensor 16 that detects the position of an engagement member 30 attached to the drive unit 12,
A base end sensor 18 provided at the base end of the drive unit 12, a tip end sensor 20 provided at the tip end of the drive unit 12, and a control unit 22 for controlling the overall operation are provided.

FIG. 2 is a perspective view showing a structural example of the drive unit 12. In FIG. 2, the drive unit 12 has a fixed element structure, and includes a support member 24, a piezoelectric element 26 that is an electromechanical conversion element, a drive member 28, and an engagement member 30.
It consists of and.

The supporting member 24 holds the piezoelectric element 26 and the driving member 28, and both ends 2 in the axial direction of the cylindrical body.
It has the 1st accommodation space 244 and the 2nd accommodation space 245 which were formed by hollowing out the inside, leaving 41,242 and the partition wall 243 located in the approximate center. The piezoelectric element 26 is housed in the first housing space 244 in a state where the expansion / contraction direction, which is the polarization direction thereof, matches the axial direction of the support member 24. The drive member 28 and a part of the engaging member 30 are housed in the second housing space 245.

The piezoelectric element 26 is, for example, constituted by laminating a plurality of piezoelectric substrates having a predetermined thickness with electrodes interposed between the respective piezoelectric substrates, and its expansion / contraction direction (laminating direction). One end face in the longitudinal direction is fixed to the end face on the one end portion 241 side of the first accommodation space 244. A circular hole is formed at the center of the other end 242 of the support member 24 and the partition wall 243, and a rod-shaped drive member 28 having a circular cross-section is formed in the second accommodation space 245 through the circular holes.
It is housed so as to be movable along the axial direction.

The end portion of the drive member 28 protruding into the first storage space 244 is fixed to the other end surface of the piezoelectric element 26, and the end portion of the drive member 28 protruding outside the second storage space 245 is a leaf spring. 32 urges the piezoelectric element 26 side with a predetermined spring pressure. The urging of the plate spring 32 to the drive member 28 causes the drive member 2 to move based on the expansion and contraction of the piezoelectric element 26.
This is for stabilizing the axial displacement of No. 8.

The engaging member 30 includes a base portion 302 having mounting portions 301 on both sides in the axial direction of the driving member 28, and both mounting portions 3.
01, and the base 302 is loosely fitted to the drive member 28, and the sandwiching member 303 is pressed downward by the leaf springs 304 attached to the both mounting portions 301. The engaging member 30 is coupled to the driving member 28 with a predetermined frictional force by being brought into contact with the driving member 28, and when the driving force larger than the frictional force acts on the engaging member 30, the driving member 28 It is possible to move along the axial direction of. The engaging member 30 is attached with the taking lens L (FIG. 1) which is an object to be driven.

FIG. 3 is a diagram showing a configuration example of the drive circuit 14. The drive circuit 14 shown in FIG. 3 is composed of a bridge circuit, and is composed of a first drive circuit 151 which is a first drive means and a second drive circuit 152 which is a second drive means. The first drive circuit 151 is an enhancement type MOS (Metal Oxide Semiconductor) type FET (Fie
ld Effect Transistor) switch element Tr1
, A second switch circuit 142 including a switch element Tr2 which is also an enhancement type MOS FET, a DC power supply voltage V1 from a drive power supply (not shown), and a waveform generator 145. The second drive circuit 152 is a third switch circuit 143 including a switch element Tr3 which is an enhancement type MOS FET, and an enhancement type MOS FE.
A fourth switch circuit 144 including a switch element Tr4 that is T, a DC power supply voltage V2 from a drive power supply (not shown), and a waveform generator 146.

In the first drive circuit 151, the DC power supply voltage V1 from a drive power supply (not shown) is supplied to the sort electrode of the switch element Tr1 and is grounded to the connection point a and the first switch circuit 141 and the first switch circuit 141. The series circuit of the two-switch circuit 142 is connected. In the second drive circuit 152, the DC power supply voltage V2 from a drive power supply (not shown) is supplied to the sort electrode of the switch element Tr3, and the third switch circuit 143 and the fourth switch circuit are connected to the grounded connection point a. 144 series circuits are connected.

The switch element Tr1 that constitutes the first switch circuit 141 and the switch element Tr3 that constitutes the third switch circuit 143 are P-channel FETs, and the switch element Tr2 and the fourth switch circuit 144 that constitute the second switch circuit 142. The switch element Tr4 configuring the above is an N-channel FET. The switch elements Tr1 and Tr3 which are P-channel FETs are turned on when the drive control signal is low level, and the switch elements Tr2 and Tr4 which are N-channel FETs are turned on when the drive control signal is high level. The piezoelectric element 26 is connected between the connection point c of the first switch circuit 141 and the second switch circuit 142 and the connection point d of the third switch circuit 143 and the fourth switch circuit 144 to form a bridge circuit. It

The first drive signal S from the waveform generator 145
d1 is applied to the gate electrodes of the switch elements Tr1 and Tr2, and the second drive signal Sd2 from the waveform generator 146 is applied to the switch elements Tr3 and T.
It is applied to the gate electrode of r4. First drive signal Sd1
The second drive signal Sd2 is a drive signal whose frequency ratio is an integer ratio, and in the present embodiment, this integer ratio is 1: 2. The first drive signal Sd1 has a rectangular waveform with an amplitude of V3 and a duty ratio D1 (D1 = B1 / A1) of 0.5, and the second drive signal Sd2 has an amplitude of V4 and a duty ratio D2 (D2 = B2 / A2) is a rectangular waveform of 0.5.
The duty ratio D1 of the first drive signal Sd1 and the second duty ratio D1
The duty ratio D2 of the driving signal Sd2 is D1 + D2
= 1.

The DC power supply voltages V1 and V2 are determined by the piezoelectric element 2
6 is a value that determines the magnitude of the rectangular wave drive voltage applied to the DC drive circuit 6. The DC power supply voltage V1 is the first drive voltage Vd1 corresponding to the first drive signal Sd1, and the DC power supply voltage V2 is the second drive signal Sd2. The second drive voltage Vd2 corresponding to
The first drive voltage Vd1 and the second drive voltage Vd2 are the first
Of the drive signal Sd1 and the second drive signal Sd2, the first drive voltage Vd1 is from the electrode A side of the piezoelectric element 26, and the second drive voltage Vd2 is from the electrode B side of the piezoelectric element 26. Applied respectively.

The DC power supply voltages V1 and V2 are V1 =
The power supply system may be unified as V2. In this case, the circuit configuration is simplified, and the cost and size of the drive circuit can be further reduced.

Returning to FIG. 1, the member sensor 16 is provided within the movable range of the engaging member 30, and is the MRE.
(Magneto Resistive Effect) element and PSD (Position
Sensitive Device) elements and other appropriate sensors. In addition, the base sensor 18 and the tip sensor 20
Is composed of an appropriate sensor such as a photo interrupter. As a result, the position of the engaging member 30 is detected by the member sensor 16, so that the movement of the engaging member 30 to the predetermined position can be controlled, while the position of the engaging member 30 is changed to the proximal end sensor 18 and the distal end sensor. Further movement of the engagement member 30 is prohibited by being detected by 20.

Further, the control unit 22 is a CP for performing arithmetic processing.
U (Central Processing Unit), ROM (Read Only Memory) in which processing programs and data are stored, and RAM (Random Access) in which data is temporarily stored
Memory) and the like, and drive-controls the drive circuit 14 based on signals input from the member sensor 16, the base end sensor 18, and the front end sensor 20. That is, the control unit 22 controls the first drive circuit 151 to generate the first drive circuit 151.
Drive signal Sd1 and DC power supply voltage V1 from the drive power supply
And the second drive signal Sd2 generated in the second drive circuit 152 and the DC power supply voltage V2 from the drive power supply.

Next, the phase difference speed control method using the drive circuit 14 will be described with reference to FIGS. FIG. 4 is a diagram showing a pulse waveform and the like of the drive voltage for explaining the principle operation of the drive circuit 14. FIG. 4A is a rectangular wave representing the first drive signal Sd1 output from the waveform generator 145, the amplitude of the rectangular wave is V3, and the duty ratio D
1 is 0.5. FIG. 4B is a rectangular wave representing the first drive voltage Vd1 applied to the piezoelectric element 26. Figure 4
(C) is the first drive frequency f applied to the piezoelectric element 26
It is a waveform showing the sine wave voltage Vd1c of d1. Figure 4
(D) is a rectangular wave representing the second drive signal Sd2 output from the waveform generator 146, the amplitude of the rectangular wave is V4, and the duty ratio D2 is 0.5. The frequency ratio between the first drive signal Sd1 and the second drive signal Sd2 is 1: 2, and the duty ratio D1 and the duty ratio D2 are
The relationship with is D1 + D2 = 1. FIG. 4E is a rectangular wave representing the second drive voltage Vd2 applied to the piezoelectric element 26. FIG. 4F shows the second voltage applied to the piezoelectric element 26.
Is a waveform representing the sine wave voltage Vd2c of the driving frequency fd2. FIG. 4G is a diagram showing the drive voltage Vd corresponding to the difference between the first drive voltage Vd1 and the second drive voltage Vd2. The first drive voltage Vd1 is applied from the electrode A which is one electrode of the piezoelectric element 26, and the second drive voltage Vd2 is applied from the electrode B which is the other electrode (see FIG. 3).

FIG. 5 is a characteristic diagram showing the mechanical resonance characteristics of the drive member 28 constituting the drive device 10. FIG. 5A is a diagram showing amplitude transfer characteristics, in which the vertical axis represents the amplitude of the drive member 28, and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28. . Figure 5
(B) is a diagram showing a phase transfer characteristic, in which the vertical axis represents the phase and the horizontal axis represents the ratio (fd / fr) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28. The value of Q, which is an amount representing the sharpness of the resonance characteristic, is 10 as the effective Q value in the state where the mechanical load is mounted on the driving member.

By setting the drive frequency fd1 and the drive frequency fd2 near the mechanical resonance frequency fr1 of the lowest mechanical resonance frequency fr of the drive member 28, the amplitude transfer characteristic of the resonance characteristic is utilized to utilize the first drive voltage. Vd
The mechanical displacement response to the harmonic components of the first and second drive voltages Vd2 (there are odd harmonics because the duty ratios D1 and D2 are 0.5) is eliminated, and a response corresponding to the fundamental component is obtained. That is, the first sine wave voltage V
The d1c and the second sinusoidal voltage Vd2c are applied to the piezoelectric element 26. Therefore, the drive frequencies fd1 and fd2 are set in the following three types with fr1 as a reference.

Fd1 <fd2 <fr1 ... Fd1 <fr1 <fd2 ... fr1 <fd1 <fd2 ... These settings are the amplitude transfer characteristics of the piezoelectric element 26 in the conventional duty rectangular wave drive. For compatibility with the phase transfer characteristic, only fd1 <fr1 <fd2 () can be set. However, since the frequencies of the first drive signal Sd1 and the second drive signal Sd2 are set based on the lowest mechanical resonance frequency fr1 of the piezoelectric element 26 that is the electromechanical conversion element, for example, the first drive signal Driving frequency fd1 of Sd1 and driving frequency fd of the second driving signal Sd2
2 and fd1 <fr1 <fd2 (), frl <fd1 <fd2 (), or fd1 <fd2 <fr1 (). It is possible, and the degree of freedom of setting is increased.

The mechanical resonance frequency fr of the piezoelectric element 26 with the support member 24 and the drive member 28 fixed to each other.
Is obtained by the following equation (1).

[0045]

[Equation 1]

In the above equation (1), “fro” is the piezoelectric element 2
6 free resonance frequency between both electrodes (piezoelectric element 26
(Mechanical resonance frequency in the direction between the electrodes of itself), mp represents the mass of the piezoelectric element 26, and mf represents the mass of the driving member 28. Although the mass of the support member 24 is related to the mechanical resonance frequency fr of the piezoelectric element 26 in the resonance system, the mass of the support member 24 is the mass of the piezoelectric element 26 and the driving member 2.
It has a sufficiently large value compared to the sum of the masses mp and mf of 8 and has a small influence on the mechanical resonance frequency fr, so it is not necessary to consider it as a calculation parameter.
Further, since the engagement member 30 does not need to be considered as an element of the resonance system because the engagement member 30 slides with respect to the drive member 28 when the piezoelectric element 26 resonates, it is included as the calculation parameter of the above formula (1). It is not.

FIG. 6A shows the fd of FIGS. 5A and 5B.
1 is a characteristic diagram showing an amplitude transfer characteristic in the case of 1 <fr1 <fd2 (), in which the vertical axis represents the amplitude of the drive member 28 and the horizontal axis represents the ratio (fd) of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28. / Fr). Figure 6 (b)
Is fd1 <fr1 <fd2 in FIGS.
FIG. 9 is a characteristic diagram showing phase transfer characteristics in the case of (), in which the vertical axis represents the phase and the horizontal axis represents the ratio of the drive frequency fd to the mechanical resonance frequency fr of the drive member 28 (fd / fr).
Represents Further, FIG. 7 is a diagram for explaining a specific operation of the drive circuit 14 applied to the drive device 10 according to the present invention.

For example, the resonance frequency fr of the drive member 28 is 0.75 times the lowest mechanical resonance frequency fr1 (fd1 =
0.75 × fr1). For convenience of explanation, the DC power supply voltages V1 and V2 are set to V1 = V2. That is, the first drive voltage Vd1 and the second drive voltage Vd2 are Vd1 = Vd2. In this case, the first drive voltage Vd1 becomes a rectangular wave as shown in FIG.
The second drive voltage Vd2 has a rectangular wave as shown in FIG. A drive voltage Vd (Vd = Vd1-Vd2) corresponding to the difference between the first drive voltage Vd1 and the second drive voltage Vd2 is applied to both electrodes A and B of the piezoelectric element 26. Due to the amplitude transfer characteristic, the harmonic components of the displacement with respect to the first drive voltage Vd1 and the second drive voltage Vd2 are removed, and the remaining fundamental wave components of the displacement undergo changes in amplitude and phase, respectively. The amplitude change due to the amplitude transfer characteristic is r1: r2 = 2.25: 0.794 as shown in FIG.
Further, the change in the phase due to the phase transfer characteristic is θ1: θ2 = −9.7 °: −173.2 ° as shown in FIG. 6B. The mechanical displacement x of the drive member 28 is the mechanical displacement x1 due to the first sine wave voltage Vd1c and the second sine wave voltage Vd2.
The mechanical displacement x2 due to c is combined (x = x1 + x2) (FIG. 7 (d)). The driving speed v of the driving member 28 is a combination of a speed v1 obtained by differentiating the mechanical displacement x1 and a speed v2 obtained by differentiating the mechanical displacement x2 (v = v1 + v
2) is obtained (FIG. 7 (e)).

Here, looking at the waveform of the combined displacement x shown in FIG. 7D, a large bulge is generated at the rising portion E, and the sawtooth waveform is not formed, and the desired driving member 28 is formed. Cannot obtain the mechanical displacement x of. Further, when the speeds v1 and v2 of the driving member 28 are substantially in phase, the waveform of the driving speed v has a substantially trapezoidal shape, but the waveform of the driving speed v shown in FIG. 7E has a substantially trapezoidal shape. Therefore, the desired speed of the drive member 28 cannot be obtained. Therefore, in order to obtain a desired saw-tooth mechanical displacement of the drive member 28, the first sine wave voltage Vd1c and the second sine wave voltage Vd2c are obtained.
It is necessary to manipulate the amplitude and phase relationship of. Since it is difficult to change the characteristics of the mechanical resonance frequency fr1 in this operation, the DC power supply voltage V1 or V2 is changed for the amplitude operation, and the first drive signal Sd for the phase operation.
This is performed by changing the phase relationship between the first and second drive signals Sd2.

Therefore, the DC power supply voltages V1 and V2 are set to, for example, V1: V2 = 1: 0.7, and the second drive signal Sd is set.
The phase of 2 is advanced by, for example, 65 ° with respect to the phase of the first drive signal Sd1. As a result, the second drive voltage Vd2 ″ as shown in FIG. 7 (f) is obtained. The mechanical displacement x2 ″ due to the second sinusoidal voltage Vd2 ″ at this time is shown in FIG.
The waveform is as shown in. The mechanical displacement x ″ obtained by combining the mechanical displacement x1 and the mechanical displacement x2 ″ has a sawtooth waveform as shown in FIG. 7 (g), and a desired mechanical displacement of the drive member 28 can be obtained. The mechanical speed v2 ″ at this time has a waveform shown in FIG. The driving speed v ″ obtained by combining the mechanical speed v1 and the mechanical speed v2 ″ has a substantially trapezoidal waveform as shown in FIG. 7 (g), and a desired driving speed can be obtained.

FIG. 8 is a diagram showing the relationship between the driving speed and the phase of the engaging member in the phase difference speed control method, where the vertical axis represents the driving speed and the horizontal axis represents the phase. When the driving speed is positive, the engaging member 30 moves in the direction of arrow a in FIG. 1 (forward), and when the driving speed is negative, the engaging member 30 moves in the direction opposite to arrow a in FIG. 1 ( Recession). In the phase difference speed control method, a constant drive signal is always applied to the piezoelectric element 26,
In addition, the first drive signal Sd1 and the second drive signal Sd2 are set so that the mechanical displacement x of the drive member 28 has a desired sawtooth waveform.
By adjusting the relationship between the amplitude and the phase of the desired engaging member 3
A drive speed of 0 can be obtained. As described above, in the phase difference speed control method, the mechanical displacement x collapses from the sawtooth waveform as the phase is changed from the phase θ _{m +} adjusted so that the maximum drive speed is obtained. ₀
(= 0), and the phase θ _m− is further inverted and adjusted so that the maximum driving speed is obtained in the opposite direction.

As a method for controlling the driving speed of the engaging member 30 other than the phase difference speed control method, the first driving voltage Vd1 and the second driving voltage Vd2 applied to the piezoelectric element 26 are simultaneously changed. There is a voltage-speed control method that allows this.

FIG. 9 is a diagram showing the relationship between the drive speed and the drive voltage of the engagement member in the voltage speed control method. The vertical axis represents the drive speed and the horizontal axis represents the drive voltage. Note that FIG.
When the value of the drive voltage is 0, the right side is the state where the phase is adjusted so that the maximum drive speed is obtained in the direction of arrow a (see FIG. 1), and the left side is the maximum drive speed in the return direction. The phase is adjusted so that As shown in FIG. 9, in the voltage speed control method, the dead band in which the drive speed of the engagement member 30 remains 0 becomes large when the value of the input drive voltage is small. It is considered that this is because the engaging member 30 is fixed to the driving member 28 by static friction, so that the engaging member 30 remains fixed unless a driving voltage above a certain level is applied. To be On the other hand, in the phase difference speed control method, since a sufficiently large drive voltage is applied even when the driving speed of the engaging member 30 is 0, the driving member 28 is constantly vibrating and the engaging member 30 is stationary. It is fixed by floating friction rather than friction. Therefore, in the phase difference speed control method, the engagement member 30 can respond sensitively to the change of the phase, and the dead zone from the stopped state to the start of the operation is reduced.

However, in the above-mentioned phase difference speed control method, the dead band from the stopped state of the engagement member 30 to the start of the operation becomes small, but the drive signal whose voltage is always constant is applied to the piezoelectric element 26. Therefore, there arises a problem that power consumption is constant and increases regardless of the driving speed of the engagement member 30. Further, in the above voltage-speed control method, since the drive voltage applied to the piezoelectric element 26 is increased or decreased, the average power consumption can be suppressed, but the dead zone from the stopped state of the engagement member 30 to the start of the operation is large. The problem arises.

In order to solve these problems, the drive device according to the present invention has a small dead zone from the stopped state of the engagement member 30 to the start of the operation, and the power consumption is kept low to drive the engagement member. It realizes the method of controlling. Specifically, one driving voltage of the first driving means and the second driving means is fixed and the other driving voltage is changed.

FIG. 10 is a diagram showing how the drive member 28 vibrates when the DC power supply voltage V2 in the drive circuit is varied. FIG. 10A shows the first drive voltage Vd1 and FIG. b) represents the second drive voltage Vd2 ″. In addition,
In FIGS. 10C to 10J, the DC power supply voltage V1 is 1.0. 10C and 10D are DC power supply voltage V
Mechanical displacement x and drive speed v of the drive member 28 when 2 = 0
Represents and. As shown in FIGS. 10C and 10D, when the DC power supply voltage V2 is 0, the second drive voltage Vd2 ″ also becomes 0, and the drive member 28 drives at the drive speed v = v1 and the mechanical displacement x = x.
Then, the engaging member 30 becomes stationary due to dynamic friction. Then, with the increase of the DC power supply voltage V2, the driving member 28 shifts from simple vibration to saw-tooth vibration, and the engaging member 30 begins to move and gradually increases in speed. 10E and 10F show DC power supply voltage V2 =
Mechanical displacement x and drive speed v of the drive member 28 in the case of 0.2
10 (g) and 10 (h) show the DC power supply voltage V2.
Represents the mechanical displacement x and the drive speed v of the drive member 28 when = 0.4, and FIGS. 10 (i) and 10 (j) show the DC power supply voltage V
The mechanical displacement x and the drive speed v of the drive member 28 when 2 = 0.7 are shown. As shown in FIGS. 10 (i) and 10 (j), when the DC power supply voltage V2 = 0.7, the mechanical displacement x of the drive member 28 has a sawtooth waveform, and the drive speed v reaches the maximum speed.

The method of reversing the forward / backward movement of the engaging member 30 may be, for example, inverting the phase of the second drive signal Sd2. In addition, the phase of the first drive signal Sd1 is 90 °
You may shift.

FIG. 11 shows the driving member 2 when the phase of the second driving signal Sd2 is inverted to move the engaging member 30 backward.
It is a figure which shows the mechanical displacement x of 8 and the drive speed v. Figure 11
As shown in (a), by inverting the phase of the second drive signal Sd2, the phase of the mechanical displacement x2 shown in FIG. 10 (i) is also inverted, and as a result, the mechanical displacement x1 and the mechanical displacement x2 are combined. In the mechanical displacement x, the steep rising portion and the slow falling portion are repeated, and the engaging member 30 moves backward. Further, as shown in FIG. 11B, by inverting the phase of the second drive signal Sd2, the phase of the drive speed v2 shown in FIG. 10J is also inverted, and the drive speed v1 and the drive speed v2 are changed. The driving speed v obtained by synthesizing is also inverted.

FIG. 12 is a diagram showing the characteristics of the driving speed of the engaging member 30 with respect to the variable DC power supply voltage V2. In FIG. 12, the phase is adjusted so that the maximum driving speed is obtained in the direction of arrow a (see FIG. 1) on the right side of the value of the DC power supply voltage V2 being 0, and the left side is in the return direction. The phase is adjusted so that the maximum drive speed is obtained. The second drive signal S to obtain the maximum drive speed
When the phase of d2 is adjusted, the DC power supply voltage V2 is 0
As the driving speed of the engaging member 30 increases, the driving speed of the engaging member 30 becomes positive, and the engaging member 30 advances. When the phase of the second drive signal Sd2 is inverted, as the DC power supply voltage V2 increases from 0, the drive speed of the engaging member 30 becomes negative and the engaging member 30 moves backward.

As described above, even when the engaging member 30 is stopped, the driving member 28 is simply vibrating and its position is fixed by the dynamic friction. Therefore, the engaging member 30 is slightly increased in DC power source voltage V2. 30 can begin operation. Therefore, the dead zone from the stopped state of the engagement member 30 to the start of the operation becomes small.

The power consumption of the drive circuit can be expressed by the following equation (2).

Pa = Pv1 + Pv2 (2) Note that Pa represents the total power consumption, and Pv1 and Pv2 represent the power consumed by the DC power supply voltages V1 and V2.

Total power consumption Pa1 in the phase difference speed control method
Can be expressed by the following expression (3) from the expression (2).

[0064]

[Equation 2]

Note that Pa1 represents the total power consumption in the phase difference speed control method, V1 and V2 represent the DC power supply voltage, and C
Represents the capacitance of the piezoelectric element, and fd1 represents the basic drive frequency.

Total power consumption Pa in the control method according to the present invention
2 can be represented by the following formula (4).

[0067]

[Equation 3]

Note that Pa2 represents the total power consumption in the control method according to the present invention, V1 represents the DC power supply voltage, and V2 ²
_AVE represents the root mean square value of the speed control voltage V2 during the speed control period.

In the case of the phase difference speed control method, the DC power supply voltages V1 and V2 are set constant at V1: V2 = 1: 0.7, so that the total power consumption is always constant and high regardless of the control speed. Will be things. On the other hand, in the case of the control method according to the present invention, the root mean square value of V2 during the speed control period is
0.49 (V2 ² = 0.
It is smaller than 7 ² ). Therefore, the total power consumption is Pa
1> Pa2, and it can be seen that the control method according to the present invention consumes less total power than the phase difference speed control method.

In this embodiment, the second drive voltage Vd2 applied to the piezoelectric element 26 is changed by changing the DC power supply voltage V2 to control the drive speed of the engaging member 30. The present invention is not particularly limited to this, and by fixing the drive signal of one of the first drive means and the second drive means and thinning the pulse number of the other drive signal, the engagement member 30 can be formed. The driving speed may be controlled. Specifically, the drive speed is controlled by keeping the value of the DC power supply voltage V2 constant and appropriately thinning out the pulse number of a rectangular wave which is a drive signal within a constant cycle. For example, when a speed instruction is given for each constant cycle such as sampling control by digital control, the ratio of the number of rectangular wave pulses and the upper limit number of the rectangular wave existing in the constant cycle is roughly proportional to the instructed speed. Match the average speed within a fixed cycle to the commanded speed.

FIG. 13 is a diagram showing a second drive signal Sd2 in another embodiment of the present invention. The second drive signal Sd2 shown in FIG. 13 has a sampling cycle (cycle of instruction speed) of 2 KHz and a first drive frequency fd1 of 6 kHz.
The second drive frequency fd2 at 0 KHz is 2 × 6
It is set to 0 KHz. The number of square wave pulses is k, and the driving speed of the engaging member 30 at that time is v _k . When the pulse number k of the rectangular wave is 5, the average driving speed of the driving member 28 is v ₅
When the pulse number k of the rectangular wave is 8, the driving member 28
The average driving speed of V is v ₈ . FIG. 14 is a diagram showing characteristics of the pulse number of the rectangular wave of the second drive signal Sd2 and the instructed speed. The vertical axis represents the pulse number k of the rectangular wave, and the horizontal axis represents the instructed speed v _k . In addition, in FIG. 14, the value of the instruction speed v _k is 0.
At the boundary, the phase is adjusted so that the maximum drive speed is obtained in the direction of arrow a (see FIG. 1) on the right side, and the phase is adjusted so that the maximum drive speed is obtained in the return direction on the left side. It is in a state of being. In the drive device by this control method,
When the phase of the second drive signal Sd2 is adjusted so that the maximum drive speed is obtained within the upper limit number 60 (k = 2 × 60 ÷ 2) of the rectangular wave, the instruction speed v _{+ 60} and the second speed drive signal to each correspond to the maximum instruction speed v _-60 phase obtained by inverting the Sd2, for example, the number of pulses of the optimum square wave from the characteristics of instruction speed v _k and the rectangular wave pulse number k of determined experimentally such as k
Is designated to control the driving speed of the engaging member 30.

As described above, the control of the drive speed by thinning out the number of pulses of the drive signal is performed by controlling the first drive signal Sd1 and the second drive signal Sd2. Therefore, when the drive voltage is varied. Compared with this, the voltage control circuit becomes unnecessary, and the circuit configuration can be simplified.

In this embodiment, the DC power supply voltage V2 having a high driving frequency is used as the speed control voltage, but the present invention is not particularly limited to this, and the DC power supply voltage V1 having a low driving frequency is used as the speed control voltage. Good. Further, in consideration of reduction of power consumption, in a state in which the phase relationship is set to a desired maximum speed, the speed control is performed on the larger one of the power consumption at the DC power supply voltage V1 and the power consumption at the DC power supply voltage V2. It is better to use voltage.

As another method of reducing power consumption, a drive circuit that can apply a sine wave voltage to the first drive voltage Vd1 and the second drive voltage Vd2 may be used.

FIG. 15 is a diagram showing another configuration example of the drive circuit 14. In this figure, the drive circuit 14 'is composed of a bridge circuit, and is composed of a first drive circuit 151' and a second drive circuit 152 '. First drive circuit 15
1'is an enhancement type MOS (Metal Oxide S
semiconductor type FET (Field Effect Transisto)
r), the first switch circuit 141 composed of the switch element Tr1, which is also an enhancement type MOS FET
Switch circuit 1 including switch element Tr2 that is
42, a DC power source voltage V1 from a drive power source (not shown), a waveform generator 145 ′, a capacitor C1, an input resistor R1 and a feedback resistor R2. The second drive circuit 152 ′ includes a third switch circuit 143 composed of a switch element Tr3 which is an enhancement type MOS FET, and a switch element Tr which is also an enhancement type MOS FET.
4, a fourth switch circuit 144, a DC power supply voltage V2 from a drive power supply (not shown), a waveform generator 146 ′, a capacitor C2, an input resistor R3, and a feedback resistor R4.
In this way, by disposing the input resistor R1 and the feedback resistor R2 in the first drive circuit 151 ′, an amplifier circuit in which the gain G1 is G1 = R2 / R1 is obtained, and similarly, the second drive circuit 151 ′ is also provided.
By arranging the input resistor R3 and the feedback resistor R4 in the driving circuit 152 ′ of the above, the gain G2 becomes G2 = R4 / R3.
It becomes an amplifier circuit. However, it is assumed that the gains G1 and G2 are sufficiently large.

In the first drive circuit 151 ', the DC power supply voltage V1 from a drive power supply (not shown) is supplied to the sort electrode of the switch element Tr1 and the first switch circuit 141 and the connection point a grounded. The series circuit of the second switch circuit 142 is connected. In the second drive circuit 152 ′, the DC power supply voltage V2 from a drive power supply (not shown) is supplied to the sort electrode of the switch element Tr3, and the third switch circuit 143 and the fourth switch are connected to the grounded connection point a. The series circuit of the circuit 144 is connected.

The switch element Tr1 forming the first switch circuit 141 and the switch element Tr3 forming the third switch circuit 143 are P-channel FETs, and the switch element Tr2 forming the second switch circuit 142 and the fourth switch circuit 144. The switch element Tr4 configuring the above is an N-channel FET. The switch elements Tr1 and Tr3 which are P-channel FETs are turned on when the drive control signal is low level, and the switch elements Tr2 and Tr4 which are N-channel FETs are turned on when the drive control signal is high level. The piezoelectric element 26 is connected between the connection point c of the first switch circuit 141 and the second switch circuit 142 and the connection point d of the third switch circuit 143 and the fourth switch circuit 144 to form a bridge circuit. It

The first drive signal Sd1 'is applied to the input resistor R1 through the DC blocking capacitor C1, and the first drive voltage Vd1' is obtained by applying the gain G1 to the first drive signal Sd1 '.
The voltage will be doubled. Similarly, the second drive signal Sd2 ′ is applied to the input resistor R3 through the DC blocking capacitor C2, and the second drive voltage Vd2 ′ is applied to the second drive signal Sd.
It is a voltage obtained by multiplying 2 ′ by the gain G2.

FIG. 16 is a diagram showing a pulse waveform of a drive voltage and the like for explaining the principle operation of the drive circuit 14 '. FIG. 16A is a sine wave representing the first drive signal Sd1 ′ output from the waveform generator 145 ′, and the amplitude of the sine wave is V3. FIG. 16D shows the waveform generator 14
6'is a sine wave representing the second drive signal Sd2 ', and the amplitude of the sine wave is V4. The frequency ratio between the first drive signal Sd1 'and the second drive signal Sd2' is an integer ratio, and in the present embodiment, this integer ratio is 1 :.
It is 2.

FIG. 16B is a sine wave voltage representing the first drive voltage Vd1 ′ applied to the piezoelectric element 26, and FIG. 16E is the second drive voltage applied to the piezoelectric element 26. It is a sine wave voltage representing the voltage Vd2 ′. FIG. 16C is a waveform showing the sine wave voltage Vd1c ′ of the drive frequency fd1 ′ applied to the piezoelectric element 26, and FIG. 16F is the sine wave voltage of the drive frequency fd2 ′ applied to the piezoelectric element 26. V
It is a waveform showing d2c '. FIG. 16G is a diagram showing the drive voltage Vd ′ corresponding to the difference between the first drive voltage Vd1 ′ and the second drive voltage Vd2 ′. The drive voltage Vd ′ is applied from the electrode A that is one electrode of the piezoelectric element 26 and the electrode B that is the other electrode.

As described above, by making the first drive signal Sd1 'and the second drive signal Sd2' sinusoidal, there is an advantage that it is not necessary to pay attention to the harmonic removal due to the amplitude transfer characteristic.

In order to simplify the circuit configuration, the first
The sine wave voltage may be applied to either one of the drive voltage Vd1 and the second drive voltage Vd2 of
In this case, it is better to use it for the drive voltage on the side that is constantly applied.

Further, in the present embodiment, if the duty ratio D1 of the first drive signal Sd1 for keeping the drive state constant and the duty ratio D2 of the second drive signal Sd2 for which the drive state is changed are both set to 0.5. However, the present invention is not particularly limited to this, and may be a rectangular wave in which the duty ratio D2 of the variable second drive signal Sd2 is not 0.5.

Further, in the present embodiment, the driving device relating to the photographing lens of the camera has been described, but the present invention is not particularly limited to this, and is suitable for driving an XY moving stage, a projection lens of an overhead projector, a lens of binoculars and the like. It is also applicable to the drive device.

[0085]

According to the invention described in claim 1, since the position of the engaging member is fixed by the dynamic friction, either one of the first drive signal and the second drive signal is applied. By fixing and changing the other drive signal, it is possible to immediately respond to the change in the drive speed, and it is possible to reduce the dead zone from the stopped state of the engagement member to the start of the operation. In addition, since one of the first drive signal and the second drive signal is fixed and the other drive signal is changed, power consumption is higher than when both are always fixed and the drive speed is controlled. Can be kept low.

According to the second aspect of the invention, normally, if the drive signal is always fixed, the power consumption increases, but when the drive speed of the engagement member is set to the maximum, the first drive means and the first drive means are set. It is possible to fix the drive signal generated by the one of the two driving means that consumes less power to suppress the power consumption.

According to the third aspect of the invention, the first drive signal and the second drive signal are rectangular wave signals, and the speed control means is one of the first drive means and the second drive means. It is possible to change the other drive signal by changing the voltage level of one of them or by thinning out the pulse number of one of the first drive means and the second drive means.

According to the invention described in claim 4, since one drive signal is a rectangular wave having a duty ratio D of 0.5, even if the other drive signal is 0, the electromechanical conversion element is subjected to simple vibration. The engagement member can be stopped by dynamic friction.

According to the fifth aspect of the present invention, the first drive signal and the second drive signal are signals having the same frequency, and the duty ratio D of the other drive signal is not a rectangular wave. Can also be applied to the drive device.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a basic configuration of a drive device including an impact type piezoelectric actuator according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration example of a drive unit.

FIG. 3 is a diagram showing a configuration example of a drive circuit.

FIG. 4 is a diagram showing a pulse waveform or the like of a drive voltage for explaining the principle operation of the drive circuit.

FIG. 5 is a characteristic diagram showing a mechanical resonance characteristic of a piezoelectric element in a state where a supporting member and a driving member which constitute a driving device are fixed.

FIG. 6 is a characteristic diagram showing an amplitude transfer characteristic and a phase transfer characteristic of the drive device according to the present invention.

FIG. 7 is a diagram for explaining a specific operation of the drive circuit applied to the drive device according to the present invention.

FIG. 8 is a diagram showing a relationship between a driving speed of a piezoelectric element and a phase in a phase difference speed control method.

FIG. 9 is a diagram showing a relationship between a drive speed and a drive voltage of a voltage element in the voltage speed control method.

FIG. 10 is a diagram showing how the driving member vibrates when the DC power supply voltage V2 in the driving circuit is varied.

FIG. 11 is a diagram showing mechanical displacement and drive speed of the drive member when the phase of the second drive signal is inverted to move the engagement member backward.

FIG. 12 is a diagram showing a characteristic of a driving speed of an engaging member with respect to a DC power supply voltage V2.

FIG. 13 is a diagram showing a second drive signal Sd2 in another embodiment of the present invention.

FIG. 14 is a diagram showing characteristics of a pulse number of a rectangular wave of a second drive signal and an instruction speed.

FIG. 15 is a diagram showing another configuration example of the drive circuit.

FIG. 16 is a diagram showing a pulse waveform or the like of a drive voltage for explaining a principle operation of a drive circuit as another configuration example.

FIG. 17 is a diagram showing a schematic configuration of a drive device of a conventional example.

18 is a block diagram showing a configuration example of a drive circuit of the drive device shown in FIG.

FIG. 19 is a diagram showing output waveforms of the drive circuit shown in FIG. 11.

FIG. 20 is a characteristic diagram showing an amplitude transfer characteristic and a phase transfer characteristic of a conventional driving device.

[Explanation of symbols]

10 Drive 14 Drive circuit 22 Control unit (speed control means) 26 Piezoelectric element (electromechanical conversion element) 28 Drive member 30 Engagement member 141 First switching circuit 142 Second switching circuit 143 Third switching circuit 144 Fourth switching circuit 145 First Waveform Oscillator 146 Second Waveform Oscillator 151 First Driving Circuit (First Driving Means) 152 Second drive circuit (second drive means) Tr1 first switch element Tr2 Second switch element Tr3 Third switch element Tr4 Fourth switch element

Claims (5)

[Claims] 1. An electromechanical conversion element that expands and contracts when a drive signal is applied, a support member fixed to one end of the electromechanical conversion element in the expansion and contraction direction, and the other in the expansion and contraction direction of the electromechanical conversion element. A drive member fixed to an end, an engagement member engaged with the drive member with a predetermined frictional force, and a drive circuit for driving the electromechanical conversion element, the electromechanical conversion element having different speeds. In a drive device that relatively moves the support member and the engagement member by expanding and contracting with each other, the first drive means for generating a first drive signal having a predetermined frequency is different from the first drive signal. Second drive means for generating a second drive signal having a predetermined frequency, and fixing one of the first drive signal and the second drive signal and changing the other drive signal. thing Thus driving apparatus characterized by comprising a speed control means for controlling the driving speed of said engaging member. 2. The one drive signal is generated by one of the first drive means and the second drive means that consumes less power when the drive speed of the engagement member is set to the maximum. The drive device according to claim 1, wherein the drive device is provided. 3. The first drive signal and the second drive signal are rectangular wave signals, and the speed control means is one of the first drive means and the second drive means. 3. The drive device according to claim 1, wherein the other drive signal is changed by changing the voltage level or thinning the number of pulses. 4. The duty ratio D is applied to the one drive signal.
Is a rectangular wave of 0.5.
The drive device according to any one of 1. 5. The first drive signal and the second drive signal are signals having the same frequency, and are rectangular waves in which the duty ratio D of the other drive signal is not 0.5. The drive device according to any one of claims 1 to 4.