JP2004056951A - Drive circuit, drive method and imaging device of piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the percussive noise of an impact-type piezoelectric actuator generated when starting and stopping the actuator. <P>SOLUTION: A drive shaft 103 fixedly coupled to a piezoelectric element 101 is capable of generating stretching variable vibrations different in speeds based on a drive signal and moving a lens hold frame 122 frictionally coupled to the drive shaft 103. In starting, the drive signal that does not drive the lens hold frame 122 even if the drive signal is applied to the piezoelectric element 101 is rapidly applied, and then the drive signal is varied so that the speed of the lens hold frame 122 is increased. In stopping, after varying the drive signal so that the speed of the lens hold frame 122 is decreased, the drive signal is continued to be applied until reaching a state that the lens hold frame 122 is not driven even if the drive signal is applied to the piezoelectric element 101. Thereafter, the lens hold frame 122 is brought into a static state by a static friction force. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a driving circuit and a driving method of a driving device using a piezoelectric actuator for moving a mechanical component constituting a camera or other precision machine or the like. Further, the present invention relates to an imaging device using the driving circuit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a driving device including an impact-type piezoelectric actuator has been known as a driving device for a mechanical component included in a camera, a precision machine, or another precision machine. Impact type piezoelectric actuators are actuators that can be reduced in size, increased in accuracy, and increased in speed with a simple configuration. FIG. 15 is a diagram showing a basic configuration of a driving device including an impact type piezoelectric actuator. A piezoelectric element 101, a support member 102 to which the piezoelectric element is fixed, a driving member 103 fixed to the piezoelectric element and displaced together with the piezoelectric element, a driven member 104 frictionally coupled to the driving member, and a voltage applied to the piezoelectric element. And a drive circuit 105. The driven member 104 is pressed against the driving member 103 by a spring 106.
[0003]
When a drive signal having a waveform consisting of a gentle rising portion and a rapid falling portion following the gentle rising portion is applied to the piezoelectric element 101, the piezoelectric element 101 gradually expands in the thickness direction at the gentle rising portion of the driving signal. , A rapid contraction displacement occurs at a rapid falling portion. When the above drive signal is applied to the piezoelectric element 101, the drive member 103 and the driven member 104 frictionally coupled to the drive member 103 extend in the extending direction (in the direction away from the support member 102) with the gentle expansion of the piezoelectric element 101 at the gentle rising portion. Go to). In the rapid falling portion, the piezoelectric element 101 contracts rapidly, and the driving member 103 also moves in the return direction, but the inertia force of the driven member 104 overcomes the frictional force and stays there. As a result, the non-driving member 104 moves intermittently with the application of the driving signal.
[0004]
In the above-described linear drive mechanism using the piezoelectric element, the vibration sound generated when the piezoelectric element is driven by the drive signal gives a discomfort to humans, but the frequency of the drive signal exceeds the audible frequency of 20 kHz. When driven by the (ultrasonic) drive signal, the vibration sound cannot be heard. However, in an impact-type piezoelectric actuator having excellent responsiveness, when the drive signal is controlled to be ON / OFF at the time of starting / stopping, the moving member suddenly moves or stops, causing a remarkable speed change. There was an inconvenience that sound was generated.
[0005]
A technique for reducing the impact noise at the time of starting or stopping is described in JP-A-9-191676. In Japanese Patent Application Laid-Open No. 9-191676, a charge applied to a piezoelectric element is controlled by controlling a drive signal for a piezoelectric element (electromechanical transducer) to gradually increase or decrease an application time or an applied voltage. Thus, the driving speed is controlled so as to gradually increase or decrease. As a result, not only the sound at the time of driving but also the acceleration at the time of starting or stopping is reduced, and the impact sound is reduced.
[0006]
[Problems to be solved by the invention]
However, in the prior art disclosed in Japanese Patent Application Laid-Open No. 9-191676, when the impact sound generated at the time of starting or stopping needs to be set to a level that cannot be heard by human ears, it takes a period from the stationary state until the target speed is reached. It is necessary to increase the start control time or the stop control time required to stop from the driving state. For this reason, when the driven member is repeatedly driven, stopped, and reversed, there is a problem that the average driving speed is reduced due to a long start control time or stop control time, and a sufficient response speed cannot be obtained.
[0007]
The present invention has been made in view of the above circumstances, and has a silent and high-response drive circuit and a drive method for a high-impact piezoelectric actuator capable of reducing a noise generated at the time of start or stop and reducing a start control time or a stop control time. I will provide a. Further, an imaging device having the above driving circuit is provided.
[0008]
[Means for Solving the Problems]
To achieve the above object, according to the first aspect of the present invention, a piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, A piezoelectric element comprising a driving member fixed to the other end and a driven member engaged with the driving member with a predetermined frictional force. The piezoelectric element moves the driven member relative to the supporting member by expanding and contracting the piezoelectric element at different speeds. In a drive circuit of an actuator, voltage control circuit means for supplying a voltage to be applied to a piezoelectric element as a drive signal, pulse generation means for generating a drive pulse so that the drive signal has a desired frequency and a duty ratio, and a voltage control circuit Control means for outputting a control signal to at least one of the means and the pulse generating means, wherein the control means applies a control signal to the piezoelectric element when the driven member is started. A start-up control signal that changes the drive signal so that the absolute value of the acceleration of the driven member increases from a state in which the drive signal is not driven even when the driven member is driven, and is applied to the piezoelectric element when the driven member stops. At least one of the stop-time control signals for applying the drive signal such that the absolute value of the acceleration of the driven member decreases until the drive signal in which the driven member is not driven is applied is output. It is characterized by the following.
[0009]
According to the second aspect of the present invention, a piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, and a drive element fixed to the other end of the piezoelectric element in the expansion and contraction direction A driving circuit for driving the piezoelectric actuator, which comprises a member and a driven member engaged with the driving member with a predetermined frictional force, and expands and contracts the piezoelectric element at different speeds to move the driven member relative to the supporting member. Voltage control circuit means for supplying a voltage to be applied to the piezoelectric element as a signal, pulse generation means for generating a drive pulse so that the drive signal has a desired frequency and duty ratio, and at least voltage control circuit means and pulse generation means On the other hand, there is a control means for outputting a control signal, and the control means makes the driven member generate a static friction force with respect to the driving member when the driven member starts. A driving method in which the driven member is not driven even when it is applied to the piezoelectric element from a stationary state, and then the driving signal is changed relatively slowly so that the speed of the driven member increases after a driving signal is applied relatively quickly. The control signal is changed relatively slowly so that the speed of the driven member is reduced until the driving signal is applied, and the driven signal does not drive the driven member even when applied to the piezoelectric element when the driven member stops. Outputting at least one of the stop-time control signals for applying the drive signal relatively quickly so that the driven member comes to a stationary state by the static frictional force with respect to the drive member after the drive signal is applied. It is characterized by.
[0010]
According to the third aspect of the present invention, in the drive circuit, the control unit controls at least one of a control signal that changes a voltage to be applied to the piezoelectric element as a drive signal and a control signal that changes a duty ratio of a drive pulse. Is output.
[0011]
According to the fourth aspect of the present invention, the piezoelectric element which expands and contracts when a drive signal is applied, the supporting member fixed to one end of the piezoelectric element in the expansion and contraction direction, and the driving element fixed to the other end of the piezoelectric element in the expansion and contraction direction A driving method for a piezoelectric actuator, comprising a member and a driven member engaged with a driving member with a predetermined frictional force, wherein the piezoelectric element expands and contracts at different speeds to move the driven member relative to the supporting member. Drive control for changing the drive signal so that the absolute value of the acceleration of the driven member increases from the state in which the drive signal is applied to the piezoelectric element when the drive member is started and the driven member is not driven, and the driven member The driving signal is applied such that the absolute value of the acceleration of the driven member is reduced until the driving signal in which the driven member is not driven even when applied to the piezoelectric element at the time of stop is applied. Of the drive control, and performing at least one of the drive control.
[0012]
According to the fifth aspect of the present invention, a piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, and a drive element fixed to the other end of the piezoelectric element in the expansion and contraction direction A driving method for a piezoelectric actuator, comprising a member and a driven member engaged with a driving member with a predetermined frictional force, wherein the piezoelectric element expands and contracts at different speeds to move the driven member relative to the supporting member. When the driven member is started, the driven member is not driven even if it is applied to the piezoelectric element from a state where the driven member is stationary with the static frictional force with respect to the driven member. A drive control that applies a drive signal that is changed relatively slowly so as to increase the speed of the member, and a drive signal that does not drive the driven member even when applied to the piezoelectric element when the driven member is stopped. After applying a drive signal that is changed relatively slowly so that the speed of the driven member decreases until the driven state is reached, the drive signal that causes the driven member to stop by the static friction force against the drive member relatively quickly It is characterized in that at least one of the applied drive controls is performed.
[0013]
According to a sixth aspect of the present invention, in the driving method, at least one of a voltage and a duty ratio of the driving signal is changed.
[0014]
The invention according to claim 7 is characterized in that the driven member is stationary with respect to the driving member by a static friction force when the driven member is stopped in the driving method.
[0015]
According to the first to seventh aspects of the present invention, the impact noise generated when the driven member starts and stops is reduced to a level inaudible to human ears, and quiet driving is enabled. Since the drive can be performed with a shorter start control time or a shorter stop control time, high-response drive is possible.
[0016]
An eighth aspect of the present invention is an imaging apparatus having the drive circuit according to any one of the first to third aspects. According to the present invention, downsizing, high precision, and high speed can be achieved with a simple configuration, and a quieter actuator can be used for driving a lens and the like, and a smaller and higher quality imaging device can be realized.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the conventional example shown in FIG. 15 and the embodiments described below, the same portions or corresponding portions are denoted by the same reference numerals, and redundant description is appropriately omitted.
[0018]
FIG. 11 is a block diagram illustrating a configuration of a digital camera according to the first embodiment of the present invention. As shown in FIG. 11, the digital camera includes a camera body 200 and an imaging unit 300.
[0019]
The zoom lens 301 of the imaging unit 300 is a lens composed of three groups, and performs zooming by moving the first and second groups and focuses by moving the third group.
[0020]
The CCD 303 converts the light of the subject formed by the zoom lens 301 into image signals of R (red), G (green), and B (blue) color components (a signal train of pixel signals received by each pixel). Signal) and output.
[0021]
The timing generator 314 generates a drive control signal for the CCD 303 based on the reference clock transmitted from the timing control circuit 202 of the camera body 200. The timing generator 314 generates clock signals such as integration start / end (exposure start / end) timing signals and light-receiving signal readout control signals (horizontal synchronization signal, vertical synchronization signal, transfer signal, etc.) for each pixel. , To the CCD 303.
[0022]
The signal processing circuit 313 performs predetermined analog signal processing on an image signal (analog signal) output from the CCD 303. The signal processing circuit 313 has a CDS (correlated double sampling) circuit and an AGC (auto gain control) circuit. The CDS circuit reduces the noise of the image signal, and the AGC circuit adjusts the gain to adjust the image signal. Adjust the level of.
[0023]
In the imaging unit 300, the zoom actuator 320, the focus actuator 321, the aperture motor 330, and the camera shake correction actuator 322 are provided with a zoom actuator drive circuit 215, a focus actuator drive circuit 214, an aperture motor drive circuit 216 provided in the camera body 200. Each is driven by a camera shake correction actuator drive circuit 217.
[0024]
Next, the blocks of the camera body 200 will be described. In the camera body 200, the A / D converter 205 converts (A / D converts) a signal of each pixel of an image into, for example, a 12-bit digital signal. The A / D converter 205 converts each pixel signal (analog signal) into a digital signal based on an A / D conversion reference clock input from the timing control circuit 202.
[0025]
The timing control circuit 202 is configured to generate a reference clock for the timing generator 314 and the A / D converter 205. The timing control circuit 202 is controlled by the overall control unit 270.
[0026]
The digital signal converted by the A / D converter 205 is input to the image processing unit 240 and the overall control unit 270, respectively. The digital signal input to the image processing unit 240 is subjected to various image processing in the image processing unit 240, and is stored in the memory card 91 as a captured image. Also, the image is displayed on the LCD 80 as a live view display image. On the other hand, the digital signal input to the overall control unit 270 is used by the overall control unit 270 to calculate the luminance, color balance, contrast, and the like of the incident light from the subject.
[0027]
The image memory 209 is a memory that stores image data output from the image processing unit 240. The image memory 209 has a storage capacity for one frame. That is, when the CCD 303 has n rows and m columns of pixels, the image memory 209 has a storage capacity for data of n × m pixels, and the data of each pixel is stored at a corresponding address.
[0028]
The VRAM (video RAM) 210 is a buffer memory for images reproduced and displayed on the LCD 80. The VRAM 210 has a storage capacity capable of storing image data corresponding to the number of pixels of the LCD 80.
[0029]
The flash control circuit 217 is a circuit that controls light emission of the built-in flash 150, and makes the built-in flash 150 emit light for a predetermined time based on a light emission start signal from the overall control unit 270.
[0030]
The camera shake detection unit 160 is a camera shake detection device that detects a camera shake by detecting a value of a speed element (translation speed, angular velocity, or the like) applied to the digital camera, and is a gyro. The value of the velocity element in the two axial directions is detected and output to the overall control unit 270. Note that the camera shake detection unit 160 may be an acceleration sensor that detects the value of an acceleration element (such as translational acceleration or angular acceleration).
[0031]
The card interface 212 is an interface for writing and reading an image to and from the memory card 91 via the card slot 280.
[0032]
The operation unit 250 includes various switches and buttons, and information input and operated by a user is transmitted to the overall control unit 270 via the operation unit 250.
[0033]
The overall control unit 270 is composed of a microcomputer, and centrally controls the photographing function and the reproduction function. The overall control unit 270 includes a CPU 271 serving as a main body thereof, a ROM 273 in which a program for organically controlling driving of each member in the imaging unit 300 and the camera main body 200 described above is stored, and an arithmetic operation is performed. A RAM 272 is provided as a work area for performing the operation. A program recorded on a recording medium such as the memory card 91 can be read out via the card interface 212 and stored in the ROM 273.
[0034]
In the present embodiment, the zoom actuator 320 and the zoom actuator drive circuit 215 will be described in detail.
[0035]
FIG. 1 is a diagram showing a lens driving mechanism including a zoom actuator 320 and a basic configuration of a zoom actuator driving circuit 215. The zoom actuator 320 moves the first and second groups of the zoom lens 301.
[0036]
First, a lens driving mechanism including the zoom actuator 320 will be described. In FIG. 1, a drive shaft 103 is supported by a support arm 124 extending from a lens barrel (not shown) so as to be movable in parallel with the optical axis direction. The piezoelectric element 101 is adhesively fixed to an extension 102 of a lens barrel (not shown), and the other end is adhesively fixed to one end of a drive shaft 103.
[0037]
A lens holding frame 122 supports the lens L1. A slider block 122a is formed in an upper extension of the lens holding frame 122, and the drive shaft 103 passes therethrough.
[0038]
A notch 122b is formed in the upper center of the slider block 122a, and the upper half of the drive shaft 103 is exposed in the notch 122b. Further, a pad 126 that is in contact with the upper half of the drive shaft 103 is fitted into the notch 122b, and the pad 126 is provided with a downward biasing force F that is in contact with the drive shaft 103 by a coil spring 127. With this configuration, the slider block 122a including the pad 126 and the drive shaft 103 are pressed against each other by the urging force F of the coil spring 127 and are frictionally engaged.
[0039]
Next, the zoom actuator drive circuit 215 will be described. The control unit 110 exists in the overall control unit 270, outputs a pulse control signal for pulse generation to the pulse generation unit 112, and controls the voltage control circuit unit 113 to change the drive voltage. A signal is output, and a driving signal applied to the piezoelectric element 101 is controlled.
[0040]
The pulse generation unit 112 outputs a drive pulse having a desired frequency and a desired duty ratio to the drive circuit unit 111.
[0041]
The voltage control circuit unit 113 generates and outputs a desired drive voltage in response to the voltage control signal. FIG. 2 is a diagram illustrating a configuration example of the voltage control circuit unit 113. The voltage control signal from the control unit 110 is converted into an analog signal by the D / A converter 131 and amplified by the amplifier 132. The amplified signal is input to the base of the power transistor 133. When a signal is input to the base of the power transistor 133, a voltage obtained by subtracting the base-emitter voltage from the input signal voltage is output to the drive circuit unit 111 as a drive voltage. By using the transistor 133, a sufficient current capacity is secured in the drive circuit portion 111. For this reason, the electric charge can be instantaneously charged in the piezoelectric element, and the displacement can be instantaneously caused.
[0042]
The power supply 114 supplies a voltage for driving each circuit to the control unit 110, the drive circuit unit 111, the pulse generation unit 112, and the voltage control circuit unit 113, and also supplies the voltage control circuit unit 113 with the drive circuit unit 111 To supply a drive voltage for output to the Although not shown, a drive voltage is also supplied to other circuits.
[0043]
In the present embodiment, a rectangular wave is used for the drive signal. As described in Japanese Patent Application Laid-Open No. 2001-268951, a drive frequency having a predetermined relationship for expanding and contracting the piezoelectric element at different speeds with respect to the resonance frequency of the piezoelectric element in a state where the support member and the drive shaft are fixed. The driven member is driven by applying a rectangular wave having the same as a drive signal. By using a rectangular wave for the drive signal, the cost and size of the circuit can be reduced. FIG. 14 is a diagram showing the waveform of the drive signal. As shown in FIG. 14, the duty ratio is defined as B / A. In the waveform shown in FIG. 14, the duty ratio is 33%.
[0044]
FIG. 3 is a diagram illustrating a configuration example of the drive circuit unit 111. In the present embodiment, an H-bridge connection circuit is used. The switches 141, 142, 143, and 144 are enhancement-type MOS-FETs. The switches 141 and 143 are P-channel FETs, and the switches 142 and 144 are N-channel FETs. Two systems of signals, drive pulse 1 and drive pulse 2, are output from the pulse generator 112 to the drive circuit 111.
[0045]
The operation principle will be briefly described. The pulse generator 112 outputs a pulse signal having a phase opposite to that of the driving pulse 1 and the driving pulse 2. When the signal of the driving pulse 1 is H (high), the switch 141 is turned off and the switch 142 is turned on. At that time, the driving pulse 2 is L (low), the switch 143 is turned on, and the switch 144 is turned off. As a result, a voltage of (+) is applied to the output terminal A side in FIG. 4, and the A side of the piezoelectric element 101 is charged. The piezoelectric element 101 is distorted by being charged with electric charge, and expands. (In this case, the piezoelectric element 101 expands when a voltage of (+) is applied to the output terminal A).
[0046]
On the other hand, when the signal of the driving pulse 1 is L (low), the switch 141 is turned on and the switch 142 is turned off. At that time, the driving pulse 2 is H (high), the switch 143 is turned off, and the switch 144 is turned on. As a result, a voltage of (+) is applied to the output terminal B side in FIG. 3, and the piezoelectric element 101 contracts. In the H-bridge circuit shown in FIG. 3, it is possible to extract expansion and contraction of a voltage application twice as large as the drive voltage.
[0047]
The amplitude of the drive signal output from drive circuit section 111 is the value of the drive voltage output from voltage control circuit section 113, and the frequency and duty ratio of the drive signal are the frequency and the duty of the drive pulse output from pulse generation section 112. Same as the duty ratio.
[0048]
In the present embodiment, the drive speed of the lens holding frame 122 is controlled by changing the voltage of the drive signal (drive voltage). FIG. 4 is a diagram illustrating a relationship between a drive voltage and a drive speed at a certain frequency (ultrasonic range) when the duty ratio is constant (about 30%). As the driving voltage increases, the driving speed increases. This is because the amount of expansion and contraction of the piezoelectric element 101 is proportional to the applied voltage. The driving speed is 0 below a certain voltage. Impact type piezoelectric actuators have a dead zone in which the driven member does not move even when a voltage is applied to the piezoelectric element. Below a certain voltage, the inertial force of the driven member cannot overcome the frictional force and the driven member Does not move relative to the drive shaft.
[0049]
FIG. 5 is a diagram for explaining the driving method according to the present embodiment, and is a diagram illustrating changes in the driving voltage and the driving speed at the time of starting and stopping. (A) is a diagram showing a change in drive voltage at start and stop, and (b) is a diagram showing a change in drive speed at start and stop. The drive voltage in the stopped state is a value at which the lens holding frame 122 is completely stopped by the static friction force alone with respect to the drive shaft 103 regardless of the posture in any posture. In this embodiment, the voltage is set to 0V.
[0050]
When a start command is issued, a pulse control signal (pulse generation command) is issued from control section 110 to pulse generation section 112. On the other hand, a voltage control signal is output to the voltage control circuit 113 so as to output the maximum voltage (the maximum voltage in the dead band voltage range) in a range where the lens holding frame 122 does not move. In the present embodiment, the frequency and the duty ratio of the drive pulse are constant. The voltage control circuit unit 113 outputs the maximum voltage in the dead band voltage range to the drive circuit unit 111 based on the voltage control signal from the control unit 110. The drive circuit unit 111 outputs a drive signal to the piezoelectric actuator based on the drive pulse and the drive voltage.
[0051]
Along with the start command, the maximum voltage in the dead band voltage range is applied to the piezoelectric element 101 relatively quickly. Then, the control unit 110 changes the voltage control signal to the voltage control circuit unit 113 relatively slowly so as to change (step up) the drive voltage so that the speed of the lens holding frame 122 increases smoothly. In particular, immediately after the start, the drive voltage is changed so that the absolute value of the acceleration of the lens holding frame 122 increases from a value close to 0. The driving speed of the lens holding frame 122 is gradually increased by continuous transition of the driving voltage, and reaches the target speed.
[0052]
At the time of stop, the drive voltage is changed (stepped down) relatively slowly so that the speed of the lens holding frame 122 decreases smoothly to the maximum voltage in the dead band voltage range. In particular, immediately before the stop, the absolute value of the acceleration of the lens holding frame 122 is changed so as to decrease, and the acceleration near the stop is set to a value close to zero. Thereafter, the pressure is reduced relatively quickly to 0 V, and the lens holding frame 122 is completely stopped by the static friction force.
[0053]
FIG. 6 is a comparison experiment result of an impact sound generated at the time of starting between the conventional driving method (the method disclosed in Japanese Patent Application Laid-Open No. 9-191676) and the driving method of the present embodiment. (A) is a diagram illustrating a change in drive voltage and a generated sound according to a conventional method, (b) is a diagram illustrating a change in drive voltage and a generated sound according to the present embodiment, and (c) is a diagram illustrating a dead band voltage range. It is a figure showing the sound generated when the maximum voltage is applied. In both cases (a) and (b), the time (T1 in FIG. 6) from the start command until reaching the target speed is common.
[0054]
In the conventional driving method, the impact sound is reduced as compared with the simple driving method in which a driving signal is applied at the time of starting, but a sound of a level audible to human ears is generated. Almost no occurrence occurs in the driving method according to this embodiment. No sound is generated even when a voltage is applied within the dead band voltage range.
[0055]
In the conventional driving method, there is a time lag between the start of voltage application and the start of actual start of the lens holding frame 122 due to the presence of a dead zone (T2 in FIG. 6). Accordingly, the time from the stop to the time when the target drive speed is reached is substantially (T2−T1), and the speed changes more rapidly. Further, even if the driving voltage is changed smoothly so that the driving speed changes smoothly at the time of starting, the lens holding frame 122 is rapidly accelerated at the moment of starting to move. The change of the drive voltage (the slope of the tangent line of the drive voltage curve) at the maximum voltage in the dead band voltage range has a large value, and the speed of the lens holding frame 122 rapidly increases upon startup. Therefore, an impulsive sound is generated at the time of starting.
[0056]
On the other hand, in the driving method according to the present embodiment, the voltage is increased at a stroke to the maximum voltage in the dead band voltage range, and then the voltage is gradually increased. As a result, the time for raising the voltage to the maximum voltage in the dead band voltage range is shortened, and no reaction delay occurs. Further, since the change in the drive voltage (tangent slope) at the start of the start of the lens holding frame 122 can be reduced, the acceleration at the start is very close to zero and almost no impact sound is generated. In the conventional driving method, in order to reduce the acceleration at the time of starting, it is necessary to take a very long time to reach the target speed (rise time).
[0057]
Although a rectangular wave is used as the drive signal in the present embodiment, the drive method and the configuration of the drive circuit described in the present embodiment can be applied regardless of the waveform of the drive signal (for example, a sawtooth wave).
[0058]
Next, a second embodiment will be described. The configuration of the digital camera according to the second embodiment is the same as the configuration shown in the first embodiment (FIG. 11). In the present embodiment, the focus actuator 321 and the focus actuator drive circuit 214 will be described in detail.
[0059]
FIG. 7 is a diagram illustrating a basic configuration of a lens drive mechanism including a focus actuator 321 and a focus actuator drive circuit 214 according to the second embodiment. The focus actuator 321 moves three groups of the zoom lens 301. The lens driving device has the same configuration as the driving device described in the first embodiment.
[0060]
In the present embodiment, the drive signal of the lens holding frame 122 is changed by using a rectangular wave as the drive signal and the duty ratio of the drive signal (drive pulse) is changed, thereby reducing the noise.
[0061]
Control section 110 outputs a pulse control signal for pulse generation and duty ratio change to pulse generation section 112.
[0062]
The pulse generation unit 112 outputs a drive pulse having a desired frequency and a desired duty ratio to the drive circuit unit 111. The frequency of the drive pulse is constant, and the drive speed is changed by outputting a signal with a changed duty ratio.
[0063]
The voltage control circuit unit 113 boosts or drops the voltage from the power supply 114 so as to output an appropriate drive voltage to the drive circuit unit 111. It is sufficient that a constant voltage is supplied to the drive circuit unit 111, and the function of changing the voltage by the control signal may be omitted.
[0064]
The drive circuit section 111 outputs a drive signal to the piezoelectric actuator 321. The amplitude of the drive signal is constant, and its value is the drive voltage. The frequency and the duty ratio of the drive signal are the same as the frequency and the duty ratio of the drive pulse, and the duty ratio changes according to the drive speed.
[0065]
FIG. 8 is a diagram illustrating the relationship between the duty ratio of the drive signal and the drive speed under a certain frequency (ultrasonic range). When the duty ratio is gradually increased from 0%, the lens holding frame 22 is stationary for a while, but starts moving when a certain duty ratio (about 15%) is reached. The speed increases as the duty ratio changes, and reaches the maximum speed at about 30%. Thereafter, the speed decreases as the duty ratio increases, and stops again at around the duty ratio of 45%. When the duty ratio is further changed, the lens holding frame 22 starts moving again when the duty ratio is about 55%, but the moving direction is reversed. The speed increases as the duty ratio increases and reaches the maximum speed at about 70%. Thereafter, the speed is reduced and the motor stops at the duty ratio of about 85%. When the duty ratio is 15% or less, 45 to 55%, or 85% or more, there is a duty ratio range of a dead zone where the lens holding frame 122 does not move even when a drive signal is given. In the present embodiment, the direction in which the lens holding frame 122 moves at a duty ratio of 50% or less is defined as a positive direction.
[0066]
FIG. 9 is a diagram for explaining the driving method according to the present embodiment, and is a diagram illustrating changes in the duty ratio of the driving signal and the driving speed at the time of starting and stopping. (A) is a diagram showing a change in duty ratio at the time of starting and stopping, and (b) is a diagram showing a change of a driving speed at the time of starting and stopping. The duty ratio in the stopped state is a value in which the lens holding frame is completely stopped by only the static frictional force with respect to the drive shaft regardless of the posture in any posture. In the present embodiment, it is 0% or 100%.
[0067]
When the start command is issued, the control unit 110 outputs a pulse control signal for pulse generation to the pulse generation unit 112. The pulse generator 112 outputs a drive pulse to the drive circuit 111. The drive circuit unit 111 outputs a drive signal to the actuator based on the pulse.
[0068]
When a drive command in the forward direction is issued, the duty ratio is increased relatively quickly from 0% to a value (15%) immediately before the lens holding frame 122 moves. After that, the control unit 110 outputs a pulse control signal (duty ratio change command) to the pulse generation unit 112, and continuously increases the duty ratio relatively slowly so that the speed change of the lens holding frame 122 becomes smooth. Let it. Particularly, immediately after starting, the duty ratio is changed so that the absolute value of the acceleration of the lens holding frame 122 increases from a value close to 0. The drive speed of the lens holding frame 122 is gradually increased by continuous transition of the duty ratio, and reaches the target speed.
[0069]
At the time of stop, the duty ratio of the drive signal is continuously changed relatively slowly so that the speed of the lens holding frame 122 decreases smoothly up to the maximum duty ratio (15%) in the duty ratio range of the dead zone. In particular, immediately before the stop, the absolute value of the acceleration of the lens holding frame 122 is changed so as to decrease, and the acceleration near the stop is set to a value close to zero. Thereafter, the duty ratio is reduced relatively quickly to 0%, and the lens holding frame is completely stopped by the static friction force.
[0070]
Subsequently, when a driving command in the negative direction is issued, the control unit 100 changes the duty ratio to 100%, and then relatively quickly to the value (85%) immediately before the lens holding frame 122 moves. Subsequently, the control unit 110 outputs a pulse control signal (duty ratio change command) to the pulse generation unit 112, and continuously reduces the duty ratio relatively slowly so that the speed change of the lens holding frame 122 becomes smooth. Let it. The drive speed of the lens holding frame 122 is gradually increased by continuous transition of the duty ratio, and reaches the target speed.
[0071]
By performing such control, the speed change (inclination of the tangent line of the driving speed curve) at the moment of starting or stopping becomes substantially zero, and extremely quiet driving without generating an impact sound is possible.
[0072]
Although a rectangular wave is used as a drive signal in this embodiment, the configuration of the drive method and the drive circuit described in this embodiment can be applied regardless of the waveform of the drive signal.
[0073]
Next, a third embodiment of the present invention will be described. The configuration of the digital camera according to the third embodiment is the same as the configuration described in the first embodiment (FIG. 11). In this embodiment, the camera shake correction actuator 322 and the camera shake correction actuator drive circuit 217 will be described in detail.
[0074]
In the present embodiment, a rectangular wave is used as the drive signal, the drive speed is controlled by changing the duty ratio of the drive signal (drive pulse), and the start and stop control is performed by changing the voltage of the drive signal (drive voltage).
[0075]
FIG. 12 is a diagram showing a basic configuration of the camera shake correction device 10 including the camera shake correction actuator 322 and the camera shake correction actuator drive circuit 217. Although the drive circuit of the Y-direction actuator is omitted in FIG. 12, a drive circuit similar to the drive circuit connected to the X-direction actuator is actually connected. Note that the voltage control circuit unit 113 in the present embodiment performs ON / OFF control. In the example of the voltage control circuit shown in FIG. 2, the D / A converter 131 may not be used.
[0076]
Control section 110 outputs a voltage control signal to voltage control circuit section 113 and outputs a pulse control signal for pulse generation and duty ratio change to pulse generation section 112.
[0077]
The pulse generation unit 112 receives a pulse control signal from the control unit 110 and outputs a drive pulse having a desired frequency and a duty ratio to the drive circuit unit 111.
[0078]
The voltage control circuit unit 113 receives a voltage control signal from the control unit 110, creates a desired drive voltage, and outputs the drive voltage to the drive circuit unit 111.
[0079]
FIG. 13 is an exploded perspective view of the camera shake correction apparatus 10. The camera shake correction apparatus 10 includes a base plate 12 serving as a base, a first slider 14 that moves in a horizontal direction (hereinafter, referred to as an X-axis direction) with respect to the base plate 12, and a moving direction of the first slider. A second slider 13 that moves in the vertical direction (hereinafter referred to as the Y-axis direction) with respect to the second slider 13 and a CCD 16 that is fixed to the second slider.
[0080]
The base plate 12 is composed of an annular metal frame 19 that is orthogonal to the direction of the optical path (hereinafter, described as the Z-axis direction) and has a large hole 20 at the center.
[0081]
From the base plate 12, various arms (press spring hooks 21, substrate holding arms 22, lifting prevention locking claws 24, positioning arms 31, rod support arms 36) described later extend in the optical axis direction (Z-axis direction). . An X-direction actuator 28 having a configuration in which a piezoelectric element 32 is sandwiched between a vibration transmission rod 34 and a weight 30 is fixed to the metal frame 19 in the X-axis direction.
[0082]
The X-direction actuator 28 has the tip and the end (the piezoelectric element 32 side) of the vibration transmission rod 34 fitted to two rod supporting arms provided on the base plate, and attaches the weight 30 to the positioning arm 31 of the base plate 12. In the contact state, the two fitting portions with the rod support arm 36 and the weight 30 are bonded to the base plate 12. Adhesion between the rod support arm 36 and the vibration transmission rod 34 is made of an adhesive such as a silicone adhesive which remains elastic even after being hardened. Adhesion between the positioning arm 31 and the weight 30 is made of a soft rubber or silicone. A contained adhesive is preferably used.
[0083]
The two rod support arms 36 of the base plate 12 are provided with protrusions 38 extending on the upper surface thereof in the Z-axis direction. The protrusion 38 is fitted into the movement restriction hole 79 of the first slider 14 during assembly, as described later.
[0084]
The first slider 14 is located on the image plane side with respect to the base plate 12 in the optical axis direction (Z-axis direction), and is made of aluminum having an opening 68 for accommodating the second slider 13 in substantially the same plane. Is formed by an annular frame 66. The first slider 14 has a first rod contact portion 74 that contacts the vibration transmission rod 34 of the X-direction actuator 28 fixed to the base plate 12 and a vibration of a Y-direction actuator 56 fixed to a second slider described later. A second rod contact portion abutting on the transmission rod 60, a pressing spring hook 72 for locking the pressing spring 70 between the pressing spring hook 21 of the base plate 12, and a movement restriction hole 79.
[0085]
The first slider 14 is urged toward the base plate 12 by a pressing spring 70 provided on a pressing spring hook 72 provided on the base plate 12 and the first slider 14 at the time of assembling. The rotation of the fourteenth vibration transmission rods 34 around them is prevented.
[0086]
The first rod contact portion 74 is provided with a groove having a V-shaped cross section, and the cap 40 is used to transmit the vibration transmission rod 34 with the groove in contact with the vibration transmission rod 34 of the X-direction actuator 28. , The first slider 14 is slidably and frictionally coupled along the vibration transmission rod 34. The holding spring 42 is used to fix the first rod contact portion 74 to the cap 40. As described above, the X-direction actuator 28 has a configuration in which the piezoelectric element 32 is sandwiched between the vibration transmission rod 34 and the weight 30, and is fitted to the rod support arm 36 of the base plate 12 and the positioning arm 31.
[0087]
The first slider 14 is disposed on the vibration transmission rod 34 of the X-direction actuator 28 as described above. The first slider 14 frictionally couples the vibration transmission rod 34 between the first rod contact portion 74 and the cap 40. The holding spring 42 is used to fix the first rod contact portion 74 to the cap 40. One end of the cap 40 is locked to the first rod contact portion 74, the center portion contacts the vibration transmission rod 34, and the other end is pulled by the holding spring 42. The contact pressure between the cap 40 and the vibration transmission rod 34 is about twice as large as the holding spring 42 used. The holding spring 42 has an oval shape, and both ends come to the center of one linear portion. The sandwiching spring 42 fixes the both ends so as to bridge the end portion and the center of the straight portion between the hook of the cap 40 and the spring hook of the first rod contact portion 74 of the first slider.
[0088]
The movement restricting hole 79 is loosely fitted with the protrusion 38 provided on the upper surface of the rod support arm 36 of the base plate 12 described above. The movement restricting hole 79 is a long hole extending in the moving direction of the first slider 14 by the movable width of the first slider 14, that is, in the extending direction (X-axis direction) of the vibration transmission rod 34. The first slider 14 is fitted to the protrusion 38 on the upper surface of the support arm 36 to restrict the first slider 14 from moving (falling) in the short side direction (Y-axis direction) of the movement restriction hole.
[0089]
The second slider 13 is a resin box having an opening 48 in the bottom wall 44, and holds the CCD 16, the radiator plate 18, the low-pass filter 17, and the Y-direction actuator 56. The heat radiating plate 18 is in contact with the back side of the CCD 16 on which the imaging surface is not provided, and covers the space defined by the peripheral wall 46 of the second slider, and the second radiating plate 18 is screwed by the screw 62 penetrating the screw hole 64. Fixed to the slider.
[0090]
The low-pass filter 17 is attached in close contact with the CCD 16 so as to cover the effective imaging surface, and is fitted into the opening 48 of the second slider. At this time, the CCD 16 is pressed by a contact spring disposed around the opening 48 so that the back surface of the CCD 16 is in close contact with the heat radiating plate 18.
[0091]
The Y-direction actuator 56 held by the second slider 13 is adhesively held by a rod support arm 50 provided on the side of the peripheral wall. The tip and the end (the piezoelectric element 59 side) of the vibration transmission rod 60 were fitted to the two rod supporting arms of the second slider 13, respectively, and the weight 58 was also brought into contact with the positioning surface 57 of the second slider. In this state, the two fitting portions and the weight 58 are bonded to the second slider 13. Similar to the bonding of the X-direction actuator described above, the bonding of the vibration transmitting rod 60 is performed by using an adhesive such as a silicon adhesive that remains elastic after being cured, and the contact of the weight 58 is performed using a soft rubber or silicon-containing material. Is preferably used.
[0092]
The second rod contact portion 76 is provided with a groove having a V-shaped cross section, and the Y-direction actuator 56 of the second slider operates by the second rod contact portion 76 of the first slider 13 and the cap 75. The first slider 14 is frictionally coupled to the second slider 13 while being sandwiched. A holding spring 78 is used to fix the second rod contact portion 76 and the cap. One end of the cap is locked to the second rod contact portion 76, the center portion contacts the vibration transmission rod 60, and the other end is pulled by the holding spring 78. The contact pressure between the cap and the vibration transmission rod 60 is about twice as large as the holding spring 78 used. The holding spring 78 has an elliptical shape like the one used in the X-direction actuator, and both ends come to the center of one linear portion. The sandwiching spring 78 fixes both ends of the straight portion between the hook of the cap and the spring hook of the second rod contact portion 76 of the first slider so as to span the center between the ends.
[0093]
The direction reference plate 54 attached to the opposing peripheral wall 44 of the Y-direction actuator of the second slider has a concave hard ball receiver 52 for holding the hard ball 15 on the front and back thereof, and the hard ball 15 is loosely fitted in the hard ball receiver 52. In this state, the first slider 14 and the base plate 12 are fixed so as to be sandwiched by the rigid balls 15 therebetween. As described above, the pressing spring 70 is hung between the first slider 14 and the base plate 12, so that the second slider 13 is prevented from rotating about the vibration transmission rod 60 of the Y-direction actuator.
[0094]
When the base plate 12 and the first slider 14 are assembled, the first slider 14 is arranged so as to fit within a region surrounded by the four substrate holding arms 22 provided on the base plate 12, and in order to prevent floating, The upper end is locked by the lifting prevention locking claw 24. On the other hand, the second slider 13 is incorporated into the first slider 14 so that the box portion thereof fits into the opening 68 of the first slider 14. The second slider 13 is integrally formed so as to hang from the first slider 14. As described above, the first slider 14 is slidable in the X-axis direction along the X-direction actuator. At this time, the second slider 13 moves integrally with the movement of the first slider 14, and The CCD 16 fixed to the slider 13 also moves in the X-axis direction. On the other hand, the second slider 13 is independently movable in the Y-axis direction with respect to the first slider 14, and the first slider is fixed to the base plate 12. , Y-axis direction. Therefore, the CCD 16 fixed to the second slider 13 also moves in the Y-axis direction.
[0095]
When the camera shake detecting unit 160 detects the value of the speed element applied to the digital camera, the overall control unit 270 calculates the moving amount and moving speed of the image due to the shake on the CCD (on the image plane) from the focal length information of the optical system. I do. Commands are issued to the two actuators based on the calculated moving speed and the position of the second slider 13 (CCD 16). In other words, the overall control unit 270 calculates the position where the second slider 13 (CCD 16) is currently calculated based on the signal input from the position detection element (not shown) of the second slider 13 (CCD 16), and Based on the signal input from the camera shake detection unit 160, the CCD 16 calculates the position where it should be, compares the difference with the current position, and performs feedback control to move the slider so that the CCD 16 returns to the position where it should be. .
[0096]
In the description of the present embodiment, only the driving method of the X-direction actuator will be described for simplicity. The description of the Y-direction actuator is omitted, but the driving method is the same as that of the X-direction actuator.
[0097]
FIG. 10 is a diagram for explaining the driving method according to the present embodiment, and is a diagram illustrating changes in the driving voltage, the duty ratio, and the driving speed at the time of starting and stopping. (A) is a diagram showing a change in drive voltage at start and stop, (b) is a diagram showing a change in duty ratio at start and stop, and (c) is a diagram showing a drive speed at start and stop. It is a figure showing a change. The drive voltage in the stopped state is a value at which the first slider 14 is completely stopped by only the static friction force without depending on the posture in any posture. In this embodiment, the voltage is set to 0V. The duty ratio in the stop state may be any value, and is 50% in the present embodiment. Note that the relationship between the duty ratio of the drive signal and the drive speed is the same as the relationship of FIG. 8 shown in the description of the second embodiment.
[0098]
The operation for correcting camera shake will be described with reference to FIGS.
[0099]
When the camera shake detector 160 detects camera shake, the overall controller 270 issues a start command to the actuator to correct the camera shake. When the start command is issued, the control unit 110 issues a drive pulse generation command to the pulse generation unit 112. The duty ratio of the drive pulse output from the pulse generator 112 is relatively quickly reduced to the duty ratio (about 45%) just before the first slider 14 moves. In this state, the first slider 14 is stopped on the vibration transmission rod 34 by the static friction force. Subsequently, the control unit 110 outputs a voltage control signal to the voltage control circuit unit 113, and the drive voltage is turned on. In the case of the present embodiment, the voltage control signal is a binary value of 1 (ON) or 0 (OFF). Therefore, the drive voltage is also a desired voltage (ON) or 0 V (OFF). In this state, the first slider 14 is stopped on the vibration transmission rod 34, but is in a floating state. That is, the vibration transmitting rod 34 vibrates due to the expansion and contraction of the piezoelectric element 32, but the inertia force of the first slider 14 overcomes the static friction force, and the first slider 14 stops on the vibration transmitting rod 34. Thereafter, the control unit 110 issues a pulse control signal (duty ratio change command) to the pulse generation unit 112, and continuously reduces the duty ratio relatively slowly so that the speed change of the first slider 14 becomes smooth. . Particularly, immediately after starting, the duty ratio is changed so that the absolute value of the acceleration of the first slider 14 increases from a value close to zero. The first slider 14 increases the speed by the continuous change of the duty ratio and reaches the target speed.
[0100]
When stopped, the control unit 110 controls the pulse generation unit 112 to change the duty ratio of the drive pulse to a duty ratio (about 45%) just before the first slider 14 stops moving, so that the speed change is relatively smooth. Issue a command to increase slowly and continuously. In particular, immediately before the stop, the absolute value of the acceleration of the first slider 14 is changed so as to decrease, and the acceleration near the stop is set to a value close to zero. Thereafter, the duty ratio is relatively quickly set to 50%, and a command is issued to the voltage control circuit unit 113 to turn off the drive voltage (0 V).
[0101]
By performing such control, the speed change at the moment of starting or at the time of stopping becomes almost zero, and extremely quiet driving without the generation of impact noise is possible.
[0102]
Although a rectangular wave is used as a drive signal in this embodiment, the configuration of the drive method and the drive circuit described in this embodiment can be applied regardless of the waveform of the drive signal.
[0103]
In the present embodiment, the movable / stop control is performed by the ON / OFF control of the drive voltage, but may be performed by the ON / OFF control of the drive pulse.
[0104]
In the present embodiment, the drive speed is controlled by changing the duty ratio of the drive signal (drive pulse). However, the speed control may be performed by changing the duty ratio and the drive voltage. Although the start / stop control is performed by changing the drive voltage, the control may be performed by changing the drive voltage and the duty ratio of the drive signal (drive pulse). By changing both the drive voltage and the duty ratio of the drive signal (drive pulse) for drive speed control or start / stop control, smoother start / stop is possible.
[0105]
In the present embodiment, camera shake correction is performed by moving the CCD. In the driving mechanism driven by the driving circuit of the impact-type piezoelectric actuator of the present invention, by moving the CCD by half the pixel pitch and moving the CCD, an image between the pixels of the CCD that cannot be obtained before the movement is obtained. It can also be used for the purpose of collecting information and obtaining a higher definition image (so-called pixel shifting method).
[0106]
In the driving method described in the first embodiment, zoom lens driving is performed, in the driving method described in the second embodiment, focus lens driving is performed, and in the driving method described in the third embodiment, camera shake correction is performed. There is no relation between the driving method and the driven member, and any driving method may be used for each driven member.
[0107]
In each of the first embodiment, the second embodiment, and the third embodiment, the driving method of the present invention is applied at the time of starting and at the time of stopping. The effect of the present invention can be obtained even when applied only to the above.
[0108]
Although a digital camera is used as an embodiment of the present invention, the present invention may be applied to an image pickup apparatus such as a video movie, a micro camera for a portable device (for example, a camera for a mobile phone), and a camera using a silver halide film. Further, it may be used for a drive unit of a pickup lens of an optical disc and an XY stage. That is, the drive circuit and the drive method described in the first, second, and third embodiments can be applied to the drive circuit and the drive method of the drive mechanism using the impact type actuator.
[0109]
【The invention's effect】
As described above, according to the first to seventh aspects of the present invention, since the impact sound generated when the driven member starts and stops is reduced to a level inaudible to human ears, quiet driving is possible. is there. Further, the start control time or the stop control time until the driven member reaches the target drive speed can be shortened, and a highly responsive actuator can be realized. Further, this drive method and drive circuit configuration can be applied without depending on the drive waveform.
[0110]
According to an eighth aspect of the present invention, since the imaging apparatus has the driving circuit according to any one of the first to third aspects, it is possible to mount an actuator realizing miniaturization, high accuracy, high speed, and low noise. Thus, a compact and high-quality imaging device can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a lens driving mechanism including a zoom actuator 320 and a basic configuration of a zoom actuator driving circuit 215.
FIG. 2 is a diagram illustrating a configuration example of a voltage control circuit unit 113.
FIG. 3 is a diagram illustrating a configuration example of a drive circuit unit 111.
FIG. 4 is a diagram illustrating a relationship between a driving voltage and a driving speed when a duty ratio is constant.
FIG. 5 is a diagram for describing a driving method according to the first embodiment, and is a diagram illustrating changes in a driving voltage and a driving speed at the time of starting and stopping. (A) is a diagram showing a change in drive voltage at start and stop, and (b) is a diagram showing a change in drive speed at start and stop.
FIG. 6 is a comparison experiment result of an impact sound generated at the time of starting between the conventional driving method and the driving method of the present invention. (A) is a diagram showing a change in drive voltage and a generated sound according to a conventional method, (b) is a diagram showing a change in drive voltage and a generated sound according to the present embodiment, and (c) is the maximum dead band voltage. It is a figure which shows the sound generated when a voltage is applied.
FIG. 7 is a view showing a basic configuration of a lens drive mechanism including a focus actuator 321 and a focus actuator drive circuit 214 according to a second embodiment.
FIG. 8 is a diagram illustrating a relationship between a duty ratio of a drive signal and a drive speed when the drive voltage is constant.
FIG. 9 is a diagram for explaining a driving method according to the second embodiment, and is a diagram illustrating a change in a duty ratio of a driving signal and a driving speed at the time of starting and stopping. (A) is a diagram showing a change in duty ratio at the time of starting and stopping, and (b) is a diagram showing a change of a driving speed at the time of starting and stopping.
FIG. 10 is a diagram for explaining a driving method according to a third embodiment, and is a diagram illustrating changes in a driving voltage, a duty ratio, and a driving speed at the time of starting and stopping. (A) is a diagram showing a change in drive voltage at start and stop, (b) is a diagram showing a change in duty ratio at start and stop, and (c) is a diagram showing a drive speed at start and stop. It is a figure showing a change.
FIG. 11 is a block diagram showing a common configuration of digital cameras according to the first, second, and third embodiments of the present invention.
FIG. 12 is a diagram showing a basic configuration of a camera shake correction device 10 including a camera shake correction actuator 322 and a camera shake correction actuator drive circuit 217.
FIG. 13A is an exploded perspective view of the camera shake correction apparatus according to the present invention.
(B) is a detailed view of the X-direction actuator portion of (a).
FIG. 14 is a diagram showing a waveform of a drive signal.
FIG. 15 is a diagram showing a basic configuration of a driving device including an impact type piezoelectric actuator.
[Explanation of symbols]
10 Camera shake correction device
12 Base plate
13 Second slider
14 First slider
15 Hard ball
16,303 CCD
17 Low-pass filter
18 Heat sink
19 frames
20 large holes
21,72 Pressing spring
22 Board holding arm
24 Floating prevention locking claw
28 X direction actuator
30 weights
32,101 Piezoelectric element
34,103 drive shaft
36 Rod support arm
38 Projection
40 cap
42,78 Holding spring
44 Bottom plate
46 Perimeter wall
48 opening
50 Rod support arm
52 direction reference plate
54 Hard Ball Receiver
56 Y direction actuator
57 Positioning surface
58 weights
60 drive shaft
62 screws
64 through hole
66 frames
68 opening
70 Press spring
74 1st rod contact part
76 Second rod contact part
79 Movement restriction hole
80 LCD
91 Memory Card
102 Supporting member
104 driven member
105 drive circuit
106 spring
110 control unit
111 Drive circuit section
112 pulse generator
113 Voltage control circuit
114 Power
122 Lens support frame
122a Slider block
122b Notch
124 support arm
126 pads
127 Coil spring
132 amplifier
133 power transistor
141, 142, 143, 144 switch
150 Built-in flash
200 Camera body
300 imaging unit

Claims (8)

A piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, a driving member fixed to the other end of the piezoelectric element in the expansion and contraction direction, In the drive circuit of the piezoelectric actuator, which comprises a driven member engaged by a frictional force, and expands and contracts the piezoelectric element at different speeds to move the driven member relative to the support member,
Voltage control circuit means for supplying a voltage to be applied to the piezoelectric element as a drive signal; pulse generation means for generating a drive pulse so that the drive signal has a desired frequency and a duty ratio;
Having control means for outputting a control signal to at least one of the voltage control circuit means and the pulse generation means,
The control means changes the drive signal such that the absolute value of the acceleration of the driven member increases from the state in which the drive signal is not driven even when applied to the piezoelectric element when the driven member is started. A drive signal is applied such that the absolute value of the acceleration of the driven member is reduced until a control signal and a drive signal that does not drive the driven member even when applied to the piezoelectric element when the driven member is stopped are applied. A drive circuit for outputting at least one of a stop control signal. A piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, a driving member fixed to the other end of the piezoelectric element in the expansion and contraction direction, In the drive circuit of the piezoelectric actuator, which comprises a driven member engaged by a frictional force, and expands and contracts the piezoelectric element at different speeds to move the driven member relative to the support member,
Voltage control circuit means for supplying a voltage to be applied to the piezoelectric element as a drive signal; pulse generation means for generating a drive pulse so that the drive signal has a desired frequency and a duty ratio;
Having control means for outputting a control signal to at least one of the voltage control circuit means and the pulse generation means,
The control means applies a driving signal relatively rapidly when the driven member is not driven even when applied to the piezoelectric element from a state in which the driven member is stationary with respect to the driving member due to static frictional force when the driven member is started. A start-up control signal that changes the drive signal relatively slowly so that the speed of the post-driven member increases, and a drive signal that does not drive the driven member even when applied to the piezoelectric element when the driven member is stopped are applied. After applying a drive signal that is changed relatively slowly so that the speed of the driven member decreases until the driven member is brought into the state of being driven, the driven member is relatively quickly stopped by the static frictional force with respect to the drive member. A drive circuit for outputting at least one of a stop-time control signal for applying a drive signal. The control means outputs at least one of a control signal for changing a voltage to be applied to the piezoelectric element as a drive signal and a control signal for changing a duty ratio of the drive pulse. The driving circuit according to claim 1 or claim 2. A piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, a driving member fixed to the other end of the piezoelectric element in the expansion and contraction direction, A method of driving a piezoelectric actuator comprising a driven member engaged by a frictional force and moving a driven member relative to a supporting member by expanding and contracting a piezoelectric element at different speeds,
Drive control for changing the drive signal so that the absolute value of the acceleration of the driven member increases from the state in which the drive signal is not driven even when applied to the piezoelectric element when the driven member is started, and the driven At least one of the drive controls for applying the drive signal so that the absolute value of the acceleration of the driven member is reduced until the drive signal in which the driven member is not driven even when applied to the piezoelectric element when the member is stopped is applied. A driving method characterized by performing one driving control. A piezoelectric element that expands and contracts when a drive signal is applied, a support member fixed to one end of the piezoelectric element in the expansion and contraction direction, a driving member fixed to the other end of the piezoelectric element in the expansion and contraction direction, A method of driving a piezoelectric actuator comprising a driven member engaged by a frictional force and moving a driven member relative to a supporting member by expanding and contracting a piezoelectric element at different speeds,
When the driven member is started, the driven member is not driven even if it is applied to the piezoelectric element from a state where the driven member is stationary with the static friction force with respect to the driving member. A drive control that applies a drive signal that is changed relatively slowly so that the speed of the drive member increases, and a drive signal that does not drive the driven member even when applied to the piezoelectric element when the driven member is stopped is applied. After applying a drive signal that is changed relatively slowly so that the speed of the driven member decreases until it reaches the state of being driven, a drive signal that the driven member stops at the driven member by the static friction force is applied relatively quickly. A driving method, wherein at least one of the driving controls is performed. The driving method according to claim 4, wherein at least one of a voltage and a duty ratio of the driving signal is changed. The driving method according to any one of claims 4 to 6, wherein the driven member is stationary with respect to the driving member by a static friction force when the driven member is stopped. An imaging device having the drive circuit according to claim 1.

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