JP2015159659A - Driving device and imaging apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device which can reduce sound at the time of activation and stop while achieving high-speed movement and accurate positioning, and an imaging apparatus using the same.SOLUTION: A driving device AD comprises: an electromechanical conversion element 12; a driving member 13 which is connected to one end of the electromechanical conversion element 12; a movement member 14 which is frictionally engaged with the driving member 13; a hall element 22, a magnet 23 and a position conversion part 54 as a position detection part for detecting the position of the movement member 14; and a position control part 51 which moves the movement member 14 to a target position. The position control part 51 repeatedly acquires the detection position of the movement member 14 detected by the position detection part, moves the movement member 14 so as to be at the target movement speed in accordance with the difference between the detection position and the target position for each detection position of the movement member 14 repeatedly acquired by the position detection part, and changes the movement speed of the movement member 14 so that the change amount per unit time in the movement speed is equal to or less than a prescribed limit value when changing the movement speed.

Description

  The present invention relates to a drive device using an electromechanical transducer that converts electrical energy into mechanical energy, and an imaging device using the drive device.

  In a mechanical device including a movable part, an actuator is usually incorporated to drive the movable part. This actuator is a device that converts input energy into mechanical motion, one of which is referred to as SIDM (Smooth Impact Drive Mechanism, “SIDM” is a registered trademark), for example, an electromechanical conversion such as a piezoelectric element. A driving device using an element is known.

  This SIDM drive device is typically an electromechanical conversion element that converts electrical energy into mechanical energy, a drive member that is fixed to one end of the electromechanical conversion element and that transmits the mechanical energy, and the drive member. A moving member and the like engaged with a predetermined friction force are provided. The electromechanical transducer is, for example, a piezoelectric element in which a plurality of piezoelectric layers made of a piezoelectric material are stacked via internal electrodes between each piezoelectric layer. A pair of external electrodes for supplying the electric energy is respectively formed on a pair of side surfaces facing each other along the stacking direction of the piezoelectric elements, and the pair of external electrodes is connected to the plurality of internal electrodes. They are connected alternately one after another. In such a SIDM drive device, when a sawtooth or pulsed drive voltage is applied from an external drive circuit via the pair of external electrodes, the piezoelectric element expands and contracts in the stacking direction. The drive member reciprocates in the longitudinal direction according to the expansion and contraction of the piezoelectric element. Here, when the electromechanical conversion element (here, the piezoelectric element) is repeatedly expanded and contracted so that the moving speed of the driving member is asymmetric between the forward path and the backward path, the moving member is moved by the asymmetric reciprocating motion of the driving member. Moving along the longitudinal direction, electrical energy is converted into movement of the moving member.

  Such a driving device is disclosed in, for example, Patent Document 1 and Patent Document 2. The drive mechanism disclosed in Patent Document 1 includes an electro-mechanical conversion element, a drive member fixedly coupled to the electro-mechanical conversion element, a driven member frictionally coupled to the drive member, and the electro-mechanical element. Drive pulse generating means for imparting expansion / contraction displacement to the conversion element, the drive pulse generation means generates expansion / contraction displacements having different expansion and contraction speeds in the electro-mechanical conversion element, and is a driven member frictionally coupled to the drive member A drive mechanism using an electro-mechanical conversion element that generates a movement in the drive pulse, wherein the drive pulse generation means includes means for controlling the time for applying the drive pulse to the electro-mechanical conversion element, and controls the application time. Thus, the driving speed is controlled by controlling the charge applied to the electromechanical conversion element. The drive pulse generator is applied to the electro-mechanical conversion element by gradually increasing the time for applying the drive pulse to the electro-mechanical conversion element at the start of driving of the drive mechanism, and gradually increasing the application time. The electric charge is controlled so as to gradually increase the driving speed. On the other hand, the drive pulse generating means is applied to the electro-mechanical conversion element by gradually decreasing the time for applying the drive pulse to the electro-mechanical conversion element when the drive mechanism is stopped and gradually decreasing the application time. The electric charge is controlled so that the driving speed gradually decreases. According to Patent Document 1, in a driving mechanism using a conventional piezoelectric element (prior art in Patent Document 1), when driving / stopping / reversing, a driving pulse is controlled to be ON / OFF for the piezoelectric element. The driving member and the moving member are suddenly moved / stopped / reversed to cause a significant speed change, and an impact sound is generated. However, since the drive mechanism configured as described above controls to gradually increase / decrease the charge of the drive pulse applied to the piezoelectric element, the drive member and the moving member are smoothly moved / stopped / reversed, and a significant speed is achieved. Since no change occurs, it is possible to prevent impact sound, resonance sound, and the like.

  The driving device disclosed in Patent Document 2 includes an electromechanical conversion element that expands and contracts when a drive voltage is applied, a drive member that is driven by the electromechanical conversion element, and a predetermined friction applied to the drive member. An engagement member engaged by force, a drive circuit for driving the electromechanical conversion element with a drive voltage composed of a rectangular wave, and drive control means for controlling the operation of the drive circuit, the electromechanical conversion element A drive device for moving the drive member and the engagement member relative to each other by causing the extension and reduction of the drive to be performed at different speeds, and further comprising a member sensor for detecting the position of the engagement member. The means outputs a drive pulse having a predetermined duty ratio based on a signal from the member sensor, and the drive circuit generates the rectangular wave in response to the drive pulse, whereby the electromechanical conversion is performed. It is obtained so as to drive the child.

JP-A-9-191676 JP 2010-260054 A

  By the way, in recent years, image sensors using solid-state image sensors such as CCD (Charged Coupled Device) type image sensors and CMOS (Complementary Metal Oxide Semiconductor) type image sensors have been improved and miniaturized. Digital devices such as mobile phones and personal digital assistants equipped with such image pickup devices using image pickup devices are becoming widespread. Further, there is a demand for enhancement of the functions of an image pickup apparatus mounted on the digital device, and an AF (Auto Focus) function, a scaling (zoom) function, and the like are also mounted. In order to realize the AF function, the scaling function, and the like, the SIDM driving device is used.

  For example, the driving device disclosed in Patent Document 2 can detect the position of the engaging member, drive the engaging member at high speed and accurately position it, and can realize the AF function and the scaling function. However, since the speed of the engaging member is high, the acceleration of the engaging member becomes large when the drive device is started or stopped (the movement start or stop of the engagement member), and as a result, a relatively loud sound is generated. Will occur. In other words, since the driving member and the engaging member are frictionally engaged, when the actuator is started or stopped, the engaging member swings back and forth along the driving direction due to the inertial mass of the engaging member. Repetitively colliding with the drive member, a relatively loud noise is generated. The image pickup apparatus mounted on the digital device is required to reduce the noise substantially the same as that of a compact digital camera or the like with respect to the sound. In the driving apparatus disclosed in Patent Document 2, the noise is reduced. It is difficult to realize

  On the other hand, it is conceivable to use the drive mechanism disclosed in Patent Document 1 for noise reduction. However, since the drive mechanism disclosed in Patent Document 1 controls to gradually increase or decrease the electric charge of the drive pulse applied to the piezoelectric element, the speed of AF and zooming becomes slow. May end up.

  The present invention is an invention made in view of the above-described circumstances, and an object of the present invention is to provide a drive device capable of reducing sound generated at the time of starting and stopping while realizing high-speed movement and accurate positioning, and a driving device thereof. It is to provide an imaging apparatus used.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, a drive device according to one aspect of the present invention is connected to an electromechanical conversion element that converts electrical energy into mechanical energy that expands and contracts, and one end in the expansion and contraction direction of the electromechanical conversion element, and the mechanical energy is transmitted. A driving member that engages the driving member with a predetermined frictional force, a position detection unit that detects the position of the moving member, and a position control unit that moves the moving member to a predetermined target position The position control unit repeatedly acquires the position of the moving member detected by the position detection unit from the position detection unit, and for each position of the moving member repeatedly acquired from the position detection unit, When the moving member is moved to change the moving speed of the moving member so that the moving speed becomes a target moving speed according to the difference between the position acquired from the position detection unit and a predetermined target position. , The amount of change per unit in the movement speed time and changes to be equal to or less than a predetermined limit value.

  In such a drive device, the position of the moving member is detected by the position detection unit, and the moving member is moved so as to achieve the target moving speed. Therefore, high-speed movement and accurate positioning of the moving member can be realized. And when the said drive device changes the moving speed of the said moving member, since it changes so that the variation | change_quantity per unit time in a moving speed may become below a predetermined limit value, in the moving speed of the said moving member Since the amount of change per unit time, that is, the acceleration is limited to the limit value or less, it is possible to reduce the sound generated when the drive device is started or stopped (movement start or movement stop of the moving member). Therefore, the drive device can reduce noise generated at the time of starting and stopping while realizing high-speed movement and accurate positioning.

  According to another aspect, in the above-described driving device, the position control unit changes the limit value according to a moving speed of the moving member.

  Since such a drive device changes the limit value according to the moving speed, the moving speed can be changed with a suitable limit value according to the moving speed.

  According to another aspect, in the above drive device, the limit value increases as the moving speed of the moving member increases.

  The noise in the so-called SIDM drive device tends to increase as the jerk increases, so that the noise increases relatively during starting and stopping when the jerk is relatively large. On the other hand, once the moving member starts moving, the jerk is reduced, so that the noise reduction can be maintained even if the limit value is increased. Therefore, since the limit value increases as the moving speed of the moving member increases, the driving device can reach the target position in a shorter time while being quiet.

  According to another aspect, in the above-described driving device, the position control unit may perform the target movement when a difference between the position acquired from the position detection unit and a predetermined target position is equal to or less than a predetermined threshold value. The speed is zero.

  In such a drive device, when the current position of the moving member approaches the target position, the target moving speed becomes zero. Therefore, even when the detection result of the position detecting unit varies due to the influence of noise or the like, the moving member is moved to the target position. So-called overshoot can be suppressed.

  According to another aspect, in the above-described driving device, the position control unit changes a moving speed of the moving member by changing a voltage value of electric energy supplied to the electromechanical transducer, The second change amount of the voltage value when the moving speed of the moving member is zero changes the moving speed of the moving member when there is a difference between the position acquired from the position detection unit and a predetermined target position. In this case, the voltage value is larger than the first change amount.

  In the drive device, since the drive member and the moving member are frictionally engaged, when the moving member starts to move, there is a dead zone that does not start moving below a predetermined voltage value. When the moving speed of the moving member is zero, that is, when the moving member is stopped, the driving device changes the voltage value by a second change amount larger than the first change amount. The dead zone can be exceeded and the movement can be started in a short time.

  An imaging apparatus according to another embodiment of the present invention includes any one of the above-described driving apparatuses, an imaging element that converts an optical image into an electrical signal, and one or more optical elements. An imaging optical system that forms an optical image of an object on a light receiving surface of the imaging element, and an optical element that moves along an optical axis direction among the one or more optical elements in the imaging optical system is It is attached to the moving member of the drive device.

  Since such an imaging apparatus includes any one of the above-described driving apparatuses, it is possible to reduce noise generated at the time of starting and stopping while realizing high-speed movement and accurate positioning. In particular, when the imaging device is a model capable of shooting a moving image, recording of noise of the driving device is reduced, and such an imaging device can capture (capture) a more preferable moving image.

  The drive device and the imaging device according to the present invention can reduce the sound generated at the time of starting and stopping while realizing high-speed movement and accurate positioning.

It is a figure which shows the external appearance structure of the mobile telephone carrying the imaging device using the drive device of embodiment. It is a block diagram which shows the electrical structure of the said imaging device. It is a typical section side view showing the structural composition of the imaging device. It is sectional drawing equivalent to the AA line of FIG. 3 in the said imaging device. FIG. 4 is a cross-sectional view corresponding to the line BB in FIG. 3 in the imaging apparatus. It is a typical cross-sectional side view which shows the structural structure of the said drive device. It is a figure which shows the sawtooth-shaped drive pulse supplied to the said drive device. It is a figure which shows the displacement of the rectangular-wave-shaped drive pulse supplied to the said drive device, and a piezoelectric element. It is a block diagram which shows the electric constitution of the said drive device. In the said drive device, it is a figure which shows the relationship of the 1st aspect of a position difference and target moving speed. In the said drive device, it is a figure which shows the relationship of the 1st aspect of the present moving speed and the amount of speed changes. It is a figure which shows the one experimental result which investigated the relationship between the amount of speed changes in the said drive device, and a loudness. It is a flowchart which shows the drive method of the 1st aspect in the said drive device. It is a flowchart which shows the drive method of the 2nd aspect in the said drive device. In the said drive device, it is a figure which shows the relationship of the 2nd aspect of a position difference and target moving speed. In the said drive device, it is a figure which shows the relationship of the 2nd aspect of the present moving speed and speed variation.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. In this specification, when referring generically, it shows with the reference symbol which abbreviate | omitted the suffix, and when referring to an individual structure, it shows with the reference symbol which attached the suffix.

  The driving device in the embodiment is usually incorporated in various devices including the movable part in order to drive the movable part. Here, as an example, the driving apparatus is an imaging device mounted on a mobile phone called a smartphone. The drive device used will be described.

  FIG. 1 is a diagram illustrating an external configuration of a mobile phone equipped with an imaging device using the driving device of the embodiment. 1A shows the front surface, and FIG. 1B shows the back surface. FIG. 2 is a block diagram illustrating an electrical configuration of the imaging apparatus. FIG. 3 is a schematic cross-sectional side view showing a structural configuration of the imaging apparatus. 4 is a cross-sectional view corresponding to the line AA of FIG. 3 in the imaging apparatus. 5 is a cross-sectional view corresponding to the line BB of FIG. 3 in the imaging apparatus. FIG. 6 is a schematic cross-sectional side view showing a structural configuration of the driving device. FIG. 6A is an overall configuration diagram, and FIG. 6B is an exploded perspective view of a lens holding frame. FIG. 7 is a diagram showing sawtooth drive pulses supplied to the drive device. The horizontal axis in FIG. 7 is time, and the vertical axis is voltage. FIG. 8 is a diagram illustrating a rectangular wave-shaped driving pulse supplied to the driving device and displacement of the piezoelectric element. FIG. 8A shows a drive pulse when the lens holding frame (moving member) is moved in one direction of travel, and FIG. 8B is a piezoelectric element (electric machine) in the case of FIG. The displacement of the conversion element) is shown. The horizontal axis in FIG. 8A represents time, the vertical axis represents drive voltage, the horizontal axis in FIG. 8B represents time, and the vertical axis represents displacement of the piezoelectric element. FIG. 8C shows a driving pulse in the case where the lens holding frame (moving member) is moved in the other direction which is opposite to the one direction of the traveling direction, and FIG. 8D shows the driving pulse shown in FIG. The displacement of the piezoelectric element (electromechanical conversion element) in the case of is shown. The horizontal axis in FIG. 8C represents time, the vertical axis represents drive voltage, the horizontal axis in FIG. 8D represents time, and the vertical axis represents displacement of the piezoelectric element. FIG. 9 is a block diagram showing an electrical configuration of the driving device. FIG. 10 is a diagram illustrating a first aspect relationship between a position difference and a target moving speed in the driving device. In FIG. 10, the horizontal axis represents the position difference, and the vertical axis represents the target moving speed Vt. FIG. 11 is a diagram illustrating a first mode relationship between the current moving speed and the speed change amount in the driving device. In FIG. 11, the horizontal axis represents the current moving speed, and the vertical axis represents the speed change amount Δv. FIG. 12 is a diagram showing a result of an experiment in which the relationship between the speed change amount and the sound volume in the driving device is examined. FIG. 12A shows a drive pulse, the horizontal axis is time, and the vertical axis is drive voltage (pulse height of the drive pulse). FIG. 12B shows the amount of change in speed in the moving member, the horizontal axis is time, and the vertical axis is the moving body speed. FIG. 12C shows the magnitude of noise generated in the drive unit (drive device), the horizontal axis is time, and the vertical axis is drive sound (noise) expressed in dB. These graphs shown in FIGS. 12A, 12B, and 12C are synchronized in time with each other.

  For example, as shown in FIG. 1, the mobile phone SP performs a telephone function by communicating with a display unit OT that displays predetermined information, an input operation unit IN that receives an input of a predetermined instruction, and a mobile phone network. The communication unit MC (not shown) that realizes the above, each unit OS, IS, IG, IB, IP, AD, CT, ME, IF shown in FIG. 2 and these units OT, IN, MC, OS, IS, IG, IB , IP, AD, CT, ME, and IF, and a thin plate-like housing HS that houses the IF. A rectangular display surface of the display unit OT faces one main surface (front surface) of the housing HS, and an input operation unit IN is disposed on one end side (lower side) of the display surface. The display surface of the display unit OT is provided with a touch panel that accepts input by touching the display surface with a fingertip or a pen, and an instruction input that cannot be input by the input operation unit IN is displayed on the touch panel and the display unit OT. It is realized by combining with information to be processed. For example, on the display unit OT, an image shooting mode start button, an image shooting button for switching between still image shooting and moving image shooting, a shutter button, and the like are displayed, and the display surface of the displayed button position is touched. The instruction indicated by the button is input to the mobile phone SP. The touch panel may be of a known type such as a so-called capacitance type. An imaging unit (imaging device) ID faces the other main surface (back surface) of the housing HS that faces the one main surface.

  First, the electrical configuration of the imaging unit ID will be described. For example, as shown in FIG. 2, the imaging unit (imaging device) ID includes an imaging optical system OS, an imaging element IS, an image generation unit IG, an image data buffer IB, an image processing unit IP, and a driving unit for the imaging function. AD, control part CT, memory | storage part ME, and interface part (I / F part) IF are provided.

  The imaging optical system OS includes one or a plurality of optical elements such as lenses and optical filters, and forms an optical image of an object (subject) on the light receiving surface of the imaging element IS. A lens LZ attached to a moving member 14 of a lens holding frame to be described later is an optical element that moves along the optical axis C among the one or more optical elements in the imaging optical system OS. The lens LZ may be a single lens or a lens group including a plurality of lenses. The lens LZ may be, for example, an AF lens that moves along the optical axis C to perform focusing (focusing). For example, the lens LZ moves along the optical axis C to perform zooming (magnification). It may be a variable power lens. An optical image of the object is guided along the optical axis C to the light receiving surface of the imaging element IS by the imaging optical system OS including such a lens LZ, and the optical image of the object is captured by the imaging element IS. The imaging element IS is an element that converts the optical image into an electrical signal. More specifically, as described above, the imaging element IS converts the optical image of the subject formed by the imaging optical system OS into electrical signals (image signals) of R, G, and B color components, and R , G, and B are output as image signals to the image generation unit IG. In the imaging element IS, the imaging operation such as imaging of either a still image or a moving image or reading of output signals of each pixel (horizontal synchronization, vertical synchronization, transfer) in the imaging element IS is controlled by the control unit CT. . The imaging element IS is, for example, a CCD type image sensor, a CMOS type image sensor, or the like.

  The image generation unit IG performs amplification processing, digital conversion processing, etc. on the analog output signal from the image sensor IS, and determines an appropriate black level, γ correction, and white balance adjustment (WB adjustment) for the entire image. Then, known image processing such as contour correction and color unevenness correction is performed to generate image data from the image signal. The image data generated by the image generation unit IG is output to the image data buffer IB. The image data buffer IB is a memory that temporarily stores image data and is used as a work area for performing later-described processing on the image data by the image processing unit IP. For example, the image data buffer IB is a volatile storage element. A RAM (Random Access Memory) or the like is used. The image processing unit IP is a circuit that performs predetermined image processing such as resolution conversion on the image data in the image data buffer IB. Further, the image processing unit IP may include a known distortion correction process, a known peripheral illuminance drop correction process, and the like as necessary. The drive unit (drive device) AD operates as described later based on a control signal output from the control unit CT, and thereby, for example, an optical element for realizing an AF function or a zooming function along the optical axis direction. To move. The control unit CT includes, for example, a microprocessor and its peripheral circuits, and includes an imaging element IS, an image generation unit IG, an image data buffer IB, an image processing unit IP, a drive unit (drive device) AD, a storage unit ME, and The operation of each unit of the I / F unit IF is controlled according to its function. That is, the imaging unit ID is controlled by the control unit CT so as to execute at least one of the still image shooting and the moving image shooting of the subject. The storage unit ME is a storage circuit that stores image data generated by still image shooting or moving image shooting of a subject. For example, a ROM (Read Only Memory) that is a nonvolatile storage element or a rewritable nonvolatile memory It comprises an EEPROM (Electrically Erasable Programmable Read Only Memory) that is a storage element, a RAM, and the like. That is, the storage unit ME has a function as a memory for still images and moving images. The I / F unit IF is an interface that transmits / receives image data to / from an external device. For example, the I / F unit IF is an interface that conforms to a standard such as USB (Universal Serial Bus) or IEEE1394.

  In such an imaging operation, in such a cellular phone SP, when the start button of the image capturing mode is operated, a control signal indicating the operation content is output to the control unit CT, and the control unit CT has a function of image capturing. When the image shooting button is operated, a control signal indicating the operation content is output to the control unit CT. The control unit CT starts and executes the still image shooting mode and starts the moving image shooting mode. The operation according to the operation content such as execution is executed. When the shutter button is operated, a control signal indicating the operation content is output to the control unit CT, and the control unit CT executes an operation corresponding to the operation content such as still image shooting or moving image shooting. .

  More specifically, when taking a still image, the control unit CT controls the imaging element IS to take a still image, and also uses the AF optics of the imaging optical system OS via the drive unit AD. Focusing is performed by operating the element. As a result, a focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor IS, converted into image signals of R, G, and B color components, and then output to the image generation unit IG. . The image signal is temporarily stored in the image data buffer IB, and after image processing is performed by the image processing unit IP, an image based on the image signal is displayed on the display unit OT. The photographer can adjust the main subject so as to be within a desired position in the screen by referring to the display unit OT. By operating a so-called shutter button (not shown) in this state, image data is stored in the storage unit ME as a still image memory, and a still image is obtained.

  In addition, when performing moving image shooting, the control unit CT controls the imaging element IS to perform moving image shooting. Thereafter, in the same manner as in the case of still image shooting, the photographer refers to the display unit OT and adjusts so that the image of the subject obtained through the image sensor IS falls within a desired position on the screen. be able to. Movie shooting is started by operating a shutter button (not shown). At the time of moving image shooting, the control unit CT controls the imaging element IS to take a moving image and operates the AF optical element of the imaging optical system OS via the drive unit AD to perform focusing. As a result, a focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor IS, converted into image signals of R, G, and B color components, and then output to the image generator IG. . The image signal is temporarily stored in the image data buffer IB, and after image processing is performed by the image processing unit IP, an image based on the image signal is displayed on the display unit OT. Then, by operating the shutter button (not shown) once again, moving image shooting is completed. The captured moving image is guided and stored in the storage unit ME as a memory for moving images.

  On the other hand, when zooming is instructed, a control signal representing the instruction content is output to the control unit CT, and the control unit CT operates the zooming lens of the imaging optical system OS via the drive unit AD to change the zoom. Do it twice. As a result, the scaled optical image is formed on the light receiving surface of the image sensor IS.

  Next, the structural configuration of the imaging unit (imaging device) ID and the drive unit (drive device) AD will be described. In this description, the xyz rectangular coordinate system is set as follows. In each figure, the z direction means the vertical direction (the direction of the optical axis C) in a side view, the origin side is the image side, and the side facing this origin side is the object side. The x and y directions mean the vertical and horizontal directions orthogonal to the z direction and orthogonal to each other in plan view.

  A substantially rectangular fixed base 3 in which the imaging element IS for converting an optical image of a subject into an electrical signal is fixed at the center is arranged, and the front of the optical axis C (+ z direction) with respect to the fixed base 3 ) Is provided with a substantially rectangular movable table 4.

  The movable table 4 is supported by the fixed table 3 via a suspension wire 5 so as to be swingable in a direction orthogonal to the optical axis C. The movable table 4 includes an upper frame portion 4a and four arm portions 4b extending from the four sides of the upper frame portion 4a in the direction of the fixed table 3.

  More specifically, one end of each of the four suspension wires 5 facing the z direction (the direction of the optical axis C) is fixed to the four corners of the fixed base 3, and the other end of each suspension wire 5 is movable. The four corners of the upper frame portion 4a of the table 4 are joined and fixed with an adhesive. The suspension wire 5 is bent in the x direction and the y direction, so that the movable table 4 is translated in the direction perpendicular to the optical axis C with respect to the fixed table 3.

  As shown in FIG. 5, elliptical coils 8 are fixed to the four sides of the upper surface of the fixed base 3, and magnets 9 facing the coils 8 are attached to the lower surfaces of the arm parts 4 b of the movable base 4. It has been. The coil 8 and the magnet 9 constitute an electromagnetic actuator 7 of an optical camera shake correction mechanism.

  A base (weight member) 11 of an AF drive unit (drive device) AD (11 to 17) is fixed to one corner of the lower surface of the upper frame portion 4a of the movable table 4.

  The drive unit (drive device) AD includes a base body 11, an electromechanical conversion element 12, a drive member 13, a moving member 14, and a drive circuit EC. More specifically, as shown in FIG. 3, in the direction of the optical axis C, in order from the top, the base 11, the piezoelectric element 12 as an example of the electromechanical conversion element 12, and the drive shaft 13 as an example of a drive member; And the drive shaft 13 extends in the direction of the fixed base 3. The drive shaft 13 is in a cantilever support state. A lens holding frame 14 as an example of the moving member 14 is frictionally engaged with the drive shaft 13. Note that a reinforcing member 30 may be fitted into the adhesive fixing portion between the piezoelectric element 12 and the drive shaft 13 as shown by a broken line in FIG. 6A, and may be bonded and fixed with an epoxy adhesive or the like.

The electromechanical transducer 12 is an element that converts input electrical energy into mechanical energy that expands and contracts, that is, mechanical motion. For example, a piezoelectric that converts input electrical energy into mechanical elastic motion by the piezoelectric effect. Elements and the like. Such a piezoelectric element includes, for example, a laminated body and a pair of external electrodes. The laminated body is formed by alternately laminating a plurality of thin film (layered) piezoelectric layers made of a piezoelectric material and a conductive thin film (layered) internal electrode layer. Each of the plurality of internal electrode layers is configured to face the outside with a pair of outer peripheral side surfaces facing each other. The pair of external electrodes are formed along the stacking direction on the pair of outer peripheral side surfaces in the stacked body, and supply the electric energy to the stacked body, and are sequentially and alternately connected to the plurality of internal electrodes. . Examples of the piezoelectric material include so-called PZT, crystal, lithium niobate (LiNbO ₃ ), potassium niobate tantalate (K (Ta, Nb) O ₃ ), barium titanate (BaTiO ₃ ), lithium tantalate (LiTaO ₃ ). And inorganic piezoelectric materials such as strontium titanate (SrTiO ₃ ).

  The drive member 13 is fixedly connected to an end surface of one end in the expansion / contraction direction of the electromechanical conversion element (piezoelectric element in the present embodiment) 12, and mechanical energy converted from electric energy is transmitted by the electromechanical conversion element 12. It is a member. More specifically, in this embodiment, the driving member 13 is a columnar (shaft-shaped) driving shaft 13 that is bonded and fixed to an end surface of one end of the laminate in the piezoelectric element by an adhesive. As the material of the driving member 13, for example, any material such as metal, resin, and carbon can be used. The cross section perpendicular to the longitudinal direction of the drive member 13 may be any shape such as a rectangle, a polygon, an ellipse, and a circle, but in this embodiment, the moving member 14 is easy along the longitudinal direction of the drive member 13. This cross section is circular so that it can be relatively moved. In addition, when this cross section is a rectangle or a polygon, it is preferable that it is chamfered from the said viewpoint.

  The base 11 is a member that is fixedly connected to the end surface of the other end in the expansion / contraction direction of the electromechanical conversion element (piezoelectric element) 12 and supported by the lower surface of the upper frame portion 4a. The base 11 has an inertial mass larger than that of the drive member (drive shaft) 13. More specifically, the base 11 has a cylindrical shape having a diameter that matches the outer shape of the electromechanical conversion element 12, and is bonded and fixed to the electromechanical conversion element 12 by an adhesive at one end face thereof. Thus, the electromechanical conversion element 12 is supported. Since such a base body 11 has an inertial mass larger than the inertial mass of the drive member 13, it is stationary with respect to the expansion and contraction motion of the electromechanical transducer 12 by being fixed to the upper frame portion 4a. The expansion and contraction motion of the electromechanical transducer 12 is mainly transmitted to the drive member 13. The base body 11 is a member for increasing the output of the drive unit AD as described above, and is not always necessary. In this case, the electromechanical conversion element 12 is fixed to the lower surface of the upper frame unit 4a. become.

  The moving member 14 is a member engaged with the driving member 13 with a predetermined frictional force, and slides with respect to the driving member 13 below the upper frame portion 4a of the movable base 4. In the present embodiment, the moving member 14 is a lens holding frame that supports and holds an AF lens LZ for realizing an AF function, which is an example of an optical element. As shown in FIG. 6B, a slider block 14a is formed on the moving member 14 of the lens holding frame by extending a part of the outer periphery. A through opening is formed in the slider block 14a along the direction of the optical axis AX, and the drive shaft 13 is inserted through the through opening. The direction of the optical axis C and the axial direction of the drive shaft 13 are parallel. A notch 14b is formed at the center of the slider block 14a, and the radial half of the drive shaft 13 is exposed at the notch 14b. A pad 15 that is in contact with the half of the drive shaft 13 in the radial direction is fitted into the notch portion 14b. The pad 15 is pressed by a spring 16 screwed to the slider block 14a with screws 17 and 17. An urging force in a direction toward the drive shaft 13 is applied. With such a structure, the lens holding frame 14 including the pad 15 and the drive shaft 13 are pressed against each other by the urging force of the pressing spring 16 and are frictionally engaged by a predetermined friction force. The structure for frictionally engaging the lens holding frame (moving member) 14 and the drive shaft 13 is not limited to such a structure. The slider block 14a is integrally formed with the lens holding frame 14, but may be connected as a separate body from the lens holding frame 14 with a separate part.

  The drive circuit EC is a circuit that generates a predetermined drive pulse supplied to the electromechanical transducer 12 in order to drive the electromechanical transducer 12. The drive circuit EC will be described in more detail later. For example, a known oscillation circuit that oscillates a sawtooth drive pulse shown in FIG. 7 can be used as the drive circuit EC. When a sawtooth pulse as shown in FIG. 7 is applied from the drive circuit EC to the piezoelectric element 12, the piezoelectric element 12 gently extends (reverses) in the thickness direction at a gently rising portion of the sawtooth pulse, The drive shaft 13 is also gently displaced in the same direction. At this time, the slider block 14 a of the lens holding frame 14 frictionally coupled to the drive shaft 13 moves in the reverse direction together with the drive shaft 13. Next, at the rapidly falling portion of the sawtooth pulse, the piezoelectric element 12 is rapidly contracted (moved forward) in the thickness direction, and the drive shaft 13 is also rapidly displaced in the same direction. At this time, the slider block 14a frictionally coupled to the drive shaft 13 overcomes the frictional coupling force by the inertial force and stays at that position, and does not substantially move in the forward direction. In this way, by continuously applying the sawtooth pulse to the piezoelectric element 12, the lens holding frame 14 can be gradually moved in the reverse direction together with the slider block 14a. Conversely, in order to gradually move the lens holding frame 14 together with the slider block 14a in the forward direction, the direction of the waveform of the sawtooth pulse applied to the piezoelectric element 12 may be changed. Further, for example, the drive circuit EC has a rectangular shape having a predetermined duty ratio (for example, 3: 7 or 7: 3) as shown in FIG. 8A or 8C in order to reduce the manufacturing cost. A known H-bridge circuit using four switching elements that oscillate using a wavy pulse as a driving pulse, or a half-bridge circuit using two switching elements can be used. When a rectangular wave pulse with a duty ratio as shown in FIG. 8A or FIG. 8C is applied from the drive circuit EC to the piezoelectric element 12, as in the case described above, FIG. 8B or FIG. As shown in D), the lens holding frame 14 can be gradually moved together with the slider block 14a.

  Here, the suspension wire 5 can serve as a transmission path for a sawtooth pulse applied to the piezoelectric element 12. That is, the sawtooth pulse (or rectangular wave pulse) generated by the drive circuit EC is transmitted through the conductive suspension wire 5 (see arrow a in FIG. 3), and then to the piezoelectric element 12 via the lead wire 20a. Can be supplied. What is necessary is just to connect the earth | ground side of the piezoelectric element 12 to the earth | ground part of the drive circuit EC via the other suspension wire 5 from the earth wire 20b (refer arrow b of FIG. 3).

  The lead wire 20a is arranged on the movable table 4 side so as to be away from the imaging device IS on the fixed table 3 side. This lead wire 20a is formed by insert-molding a conductive metal foil in a movable base 4 made of an insulating synthetic resin, one end is connected to the suspension wire 5 inside the movable base 4, and the other end is movable base 4 It is also possible to pull out from the piezoelectric element 12 and connect it to the piezoelectric element 12. In this way, it is possible to further reduce the noise of the image sensor IS due to the sawtooth pulse.

  In this way, the lens L14 for AF is automatically focused by driving the lens holding frame 14 forward or backward by the drive unit AD. Although not specifically shown, a rotation prevention mechanism is provided to prevent rotation of the lens holding frame 14 that is cantilevered by the drive shaft 13. As shown in FIGS. 3 and 4, the position detection magnet 23 is attached to the lens holding frame 14, and the Hall element 22 is attached to the movable base 4, thereby detecting the forward / backward (focus) position of the lens holding frame 14. I am doing so. Further, by holding the zoom lens LZ with the lens holding frame 14 instead of the AF lens LZ, similarly, the forward / backward (magnification) position of the lens holding frame 14 can be detected and zoomed.

  Simultaneously with this autofocus, the electromagnetic actuator 7 of the optical camera shake correction mechanism is driven, and the movable base 4 is translated in the direction orthogonal to the optical axis C, whereby camera shake correction is performed. Here, the behavior of the lens holding frame 14 during the camera shake correction drive will be described. Note that the lens holding frame 14 exhibits the same behavior in the x direction and the y direction. The magnet 9 is assumed to be magnetized with an N pole on the upper surface and an S pole on the lower surface. When no current is flowing through the coil 8, no electromagnetic force is generated between the magnet 9 and the coil 8, so that the four suspension wires 5 remain in a state parallel to the z direction. On the other hand, when a current is passed through the coil 8 in the direction of the arrow in FIG. 5, an electromagnetic force is generated between the magnet 9 and the coil 8, so that the magnet 9 is mounted and supported by the four suspension wires 5. The table 4 is moved in the −x direction. At the time of actual camera shake correction driving, the direction and magnitude of the current flowing through the coil 8 change according to a predetermined control signal, and accordingly, the movable base 4 is ensured to be parallel to the image sensor 2 in the x direction. Shift driven in the state. The posture of the movable table 4 supported by the four suspension wires 5 as in the present embodiment is secured by a support mechanism having no spring property, such as the drive shaft 13 of the drive unit AD. Therefore, the image pickup device 2 is driven to shift in a state in which the parallelism in the x and y directions is ensured.

  Next, the electrical configuration of the drive unit (drive device) AD, that is, the drive circuit EC will be described more specifically. As shown in FIG. 9, for example, the drive circuit EC includes a position control unit 51, a drive unit 52, a control target position setting unit 53, and a position conversion unit 54.

  The control target position setting unit 53 sets a target position Pt of the moving member (lens holding frame) 14 and outputs the set target position Pt to the position control unit 51. For example, when the AF lens LZ is held on the lens holding frame 14, the control target position setting unit 53 sets the focus position Pf as the target position Pt by known conventional means such as a so-called hill climbing method. For example, when the zoom lens LZ is held by the lens holding frame 14, the control target position setting unit 53 sets the position Pz corresponding to the magnification input by the user's operation as the target position Pt.

  The position conversion unit 54 constitutes a position detection unit that detects the position P of the moving member 14 with the Hall element 22 and the magnet 23 described above. The position conversion unit 54 receives the output of the Hall element 22, amplifies the output of the Hall element 22, performs analog-digital conversion, converts the converted position information into position information of the moving member 14, and converts the converted position information to the current position of the moving member 14. The position Pc is output to the position controller 51. The output of the Hall element 22 is substantially proportional to the amount of movement of the magnet 23, that is, the amount of movement of the moving member 14. Therefore, for example, the correspondence relationship between the output of the Hall element 22 and the position P of the moving member 14 is checked in advance, and this correspondence relationship is held in the position conversion unit 54 in, for example, a lookup table format, for example, in a functional equation format. The position conversion unit 54 can convert the output of the Hall element 22 into position information of the moving member 14 using this correspondence.

  The position control unit 51 is a circuit that generates a control signal so as to move the moving member 14 to the target position Pt input from the control target position setting unit 53 and outputs the generated control signal to the drive unit 52. . More specifically, the position control unit 51 repeatedly acquires the position P (t) of the moving member 14 detected by the magnet 23, the Hall element 22 and the position conversion unit 54 from the position conversion unit 54, and this position conversion unit 54. For each position P (t) of the moving member 14 that is repeatedly acquired from the moving member 14, the moving member 14 is set so as to have a target moving speed Vt according to the difference between the position Pc acquired from the position converting unit 54 and the target position Pt. When the moving speed V of the moving member 14 is changed, the change amount ΔV per unit time in the moving speed V is changed to be equal to or less than a predetermined limit value ΔVth. Such a position control unit 51 includes, for example, a target speed calculation unit 511, a current speed calculation unit 512, a movement speed calculation unit 513, and a movement speed change amount limiting unit 514.

  The target speed calculation unit 511 repeatedly acquires the current position Pc of the moving member 14 detected by the position conversion unit 54 included in the position detection unit from the position conversion unit 54 and is repeatedly acquired from the position conversion unit 54. For each position P (t), the difference between the current position Pc input from the position conversion unit 54 and the target position Pt input from the control target position setting unit 53 (position difference Psub = Pt−Pc). A corresponding target moving speed Vt is calculated, and the calculated target moving speed Vt is output to the moving speed calculating unit 513. For example, as shown in FIG. 10, the relationship between the position difference Psub and the target moving speed Vt is given in advance, and is held in the target speed calculation unit 511 in, for example, a look-up table format or a function format, for example. . The target speed calculation unit 511 calculates the target moving speed Vt according to the position difference Psub using this relationship. In the example shown in FIG. 10, the target movement speed Vt increases proportionally as the position difference Psub increases until reaching the maximum target movement speed Vmax from 0, and when the maximum target movement speed Vmax is reached, The target moving speed Vt is constant regardless of the size of the position difference Psub. That is, in the example shown in FIG. 10, when the distance from the current position Pc to the target position Pt is relatively long, the target moving speed Vt is set faster, and when the distance is relatively short, The moving speed Vt is set slower.

  The current speed calculation unit 512 acquires the current position Pc of the moving member 14 detected by the position conversion unit 54 included in the position detection unit from the repeated position conversion unit 54 substantially in synchronization with the target speed calculation unit 511, For each position P (t) of the moving member 14 repeatedly acquired from the conversion unit 54, the current movement speed Vc is calculated from the past position Pp a predetermined time ago and the current position Pc input from the position conversion unit 54, The calculated current moving speed Vc is output to the moving speed calculating unit 513. The predetermined time is, for example, a time measured from the timing (time) at which the current moving speed Vc was previously calculated by the current speed calculating unit 512.

  The movement speed change amount limiting unit 514 sets a limit value ΔVmax of the change amount ΔV per unit time in the movement speed V, and outputs the set limit value (upper limit value) ΔVmax to the movement speed calculation unit 513. Is. For example, as shown in FIG. 11, the limit value ΔVmax is set to a constant value regardless of the current moving speed, and is held in the moving speed change amount limiting unit 514.

  The movement speed calculation unit 513 calculates a difference (speed difference) Vsub (= Vt−Vc) between the target movement speed Vt calculated by the target speed calculation unit 511 and the current movement speed Vc calculated by the current speed calculation unit 512. Accordingly, the moving speed V is set. When the moving speed V of the moving member 14 is changed, the change amount ΔV of the moving speed V is set to be equal to or less than the limit value ΔVmax (change in moving speed). The moving speed V is changed and set so that the amount ΔV does not exceed the limit value ΔVmax. Then, the movement speed calculation unit 513 generates a control signal so that the set movement speed V is obtained, and outputs the generated control signal to the drive unit 52.

  The drive unit 52 generates the above-described sawtooth drive pulse or rectangular-wave drive pulse in accordance with the control signal input from the movement speed calculation unit 513, and generates the generated drive pulse as a drive unit (drive device). An AD electromechanical transducer (piezoelectric element) 12 is supplied.

  The position control unit 51, the drive unit 52, the control target position setting unit 53, and the position conversion unit 54 may be configured by individual circuits, and one or more of these units 51 to 54 may include a CPU and a memory. You may comprise by the microcomputer comprised including an element etc. In the case of being configured by a microcomputer, one or more of these units 51 to 54 are functionally configured by executing a predetermined program. When the position control unit 51 is configured by a microcomputer, the target speed calculation unit 511, the current speed calculation unit 512, the movement speed calculation unit 513, and the movement speed change amount restriction unit 514 are also functionally configured.

Moreover, in this embodiment, the electromechanical conversion element 12 is a piezoelectric element 12 as an example, and this piezoelectric element 12 expands and contracts by an expansion / contraction amount according to the magnitude of the applied voltage. For this reason, in this embodiment, the maximum target moving speed Vmax is defined by a voltage value that can be applied to the piezoelectric element 12, and is set to, for example, 2.8V. The limit value ΔVmax is also defined by the voltage value E. The noise of the drive unit (drive device) AD is generated by vibration of the moving member 14 and the like due to a sudden start and stop of the moving member 14. The relationship between the amount of change in speed and the magnitude of noise in the driving unit AD of the SIDM is the weight of the moving member 14 and the center of gravity of the moving member 14 (including the lens when holding the lens LZ) from the axis of the driving member 13. The relationship can be obtained by experiment, depending on the distance to the distance, the length of the frictionally engaged portion of the driving member 13 and the moving member 14, and the like. FIG. 12 shows an experimental result of the relationship in the drive unit AD used in this embodiment. Assuming that the allowable noise level set in advance is 20 dB, the drive unit AD used in the present embodiment has, as a result of various experiments, the voltage value E of the drive pulse as shown in FIG. Is changed at 0.4 V / msec, the change amount ΔV of the moving speed V in the moving member 14 is 1 m / sec ² as shown in FIG. 12B, and as a result, the magnitude of the noise is as shown in FIG. As shown in FIG. 12 (C), it becomes 20 dB or less. From such experimental results, in the present embodiment, for example, the limit value ΔVmax is defined by the voltage value E, and is set to ΔEmax = | 0.4 | V / msec. The limit value ΔVmax (ΔEmax in voltage value) is appropriately changed according to the allowable noise level.

  Next, as described above, an operation related to noise reduction in the drive unit (drive device) AD used for the imaging device ID mounted on the mobile phone SP will be described. FIG. 13 is a flowchart showing a driving method of the first aspect in the driving device.

  For example, when the target position Pt is input from the control target position setting unit 53 to the position control unit 51 in the AF operation, the zooming operation, or the like, the position control unit 51 moves the moving member 14 to the target position Pt. It works as follows.

  In FIG. 13, first, the target speed calculation unit 511 of the position control unit 51 acquires the current position Pc of the moving member 14 detected by the position conversion unit 54 from the position conversion unit 54, and is input from the position conversion unit 54. A difference between the current position Pc and the target position Pt input from the control target position setting unit 53 (position difference Psub = Pt−Pc) is calculated, and from the relationship between the position difference Psub and the target moving speed Vt, A target moving speed Vt corresponding to the position difference Psub is calculated, and the calculated target moving speed Vt is output to the moving speed calculating unit 513 (S11).

  The current speed calculation unit 512 of the position control unit 51 substantially synchronizes with the above-described processing S11 of the target speed calculation unit 511, and the past position Pp a predetermined time ago and the current position Pc input from the position conversion unit 54. The current travel speed Vc is calculated from the current travel speed Vc, and the calculated current travel speed Vc is output to the travel speed calculation unit 513 (S12). As will be described later, the processes S11 to S17 shown in FIG. 13 are repeatedly executed until the moving member 14 reaches the target position Pt. For example, the past position Pp is converted into the previous position in this repetition process. The predetermined position may be the current position Pc input from the unit 54. In this case, the predetermined time is, for example, the time from the execution of the previous process S12 to the execution of the current process S12 in this repetitive process (one servo cycle). It becomes.

  Next, the movement speed calculation unit 513 of the position control unit 51 includes the target movement speed Vt calculated by the target speed calculation unit 511 in process S11 and the current movement speed Vc calculated by the current speed calculation unit 512 in process S12. (Speed difference) Vsub is calculated, and it is determined whether the calculated speed difference Vsub is positive, 0, or negative (S13). As a result of this determination, when the speed difference Vsub is 0, that is, when the target moving speed Vt is equal to the current moving speed Vc (“=”), the moving speed calculating unit 513 ends the current process. As a result of the determination, when the speed difference Vsub is positive, that is, when the current movement speed Vc has not reached the target movement speed Vt (“Yes”), the movement speed calculation unit 513 executes the process S14. As a result of the determination, if the speed difference Vsub is negative, that is, if the current movement speed Vc exceeds the target movement speed Vt (“No”), the movement speed calculation unit 513 executes step S15.

  In process S14, the moving speed calculation unit 513 sets the voltage value currently instructed to the drive unit 52 to be increased by 0.4 V per millisecond. Next, the moving speed calculation unit 513 determines whether or not the voltage value increased by 0.4 V exceeds the maximum voltage value 2.8 V of the piezoelectric element 12 (S16). As a result of this determination, when the voltage value increased by 0.4 V exceeds the maximum voltage value 2.8 V of the piezoelectric element 12 (“Yes”), the moving speed calculation unit 513 instructs the drive unit 52. The voltage value is set to 2.8V (S17), and the current process is terminated. As a result of the determination, when the voltage value increased by 0.4 V does not exceed the maximum voltage value of 2.8 V of the piezoelectric element 12, that is, the voltage value increased by 0.4 V is 2.8 V of the maximum voltage value of the piezoelectric element 12. In the case of the following (“No”), the moving speed calculation unit 513 ends the current process.

  On the other hand, in process S15, the moving speed calculation unit 513 sets the voltage value currently instructed to the drive unit 52 to be lowered by 0.4 V per millisecond, and ends the current process.

  Thus, when the voltage value instructed to the drive unit 52 is set, the moving speed calculation unit 513 generates a control signal representing this voltage value and outputs this control signal to the drive unit 52. The drive unit 52 drives the drive unit (drive device) AD so that the voltage value represented by this control signal is obtained. In this case, the change in the voltage value applied to the piezoelectric element 12 is limited to 0.4 V / ms, as can be seen from the processes S14 and S15, so that the moving speed V of the moving member 14 is also the limit value. ΔVmax or less.

  When each of the current processing S11 to S17 (one servo processing) is completed, the position difference Psub becomes 0 and the target moving speed Vt becomes 0, that is, the moving member 14 Until it is determined that has reached the target position Pt, the process is returned to the process S11 so as to execute each of the following processes S11 to S17.

  As described above, the imaging device ID and the drive unit (drive device) AD in the present embodiment detect the position P of the moving member 14 by the Hall element 22, the magnet 23, and the position conversion unit 54 as the position detection unit, and the target moving speed. Since the moving member 14 is moved to Vt, high-speed movement and accurate positioning of the moving member 14 can be realized. When the moving device 14 changes the moving speed V of the imaging device ID and the driving unit (driving device) AD, the change amount ΔV per unit time in the moving speed V is equal to or less than a predetermined limit value ΔVmax. Therefore, since the change amount ΔV per unit time in the moving speed V of the moving member 14, that is, the acceleration is limited to a limit value ΔVmax or less, the drive unit (drive device) AD is started or It is possible to reduce the sound generated when stopping (movement start or movement stop of the moving member 14). Therefore, the imaging device ID and the drive unit (drive device) AD can reduce the sound generated at the time of starting and stopping while realizing high-speed movement and accurate positioning.

  In addition, since the driving member 13 and the moving member 14 are frictionally engaged with each other, the driving unit (driving device) AD does not start moving below a predetermined voltage value when the moving member 14 starts moving. There is a dead zone. In consideration of this, the piezoelectric element 12 is used as the electromechanical transducer, and the moving speed V of the moving member 14 is changed by changing the voltage value of the electric energy supplied to the piezoelectric element 12. The control unit 51 determines that the second change amount of the voltage value when the moving speed V of the moving member 14 is zero is the position acquired from the position converting unit 54 included in the position detecting unit and a predetermined target position. You may operate | move so that it may become larger than the 1st change amount of the said voltage value in the case of changing the moving speed of the moving member 14, when there exists a difference. That is, the imaging device ID and the drive unit (drive device) AD may operate as shown in FIG. 14 instead of the operation shown in FIG.

  FIG. 14 is a flowchart showing a driving method of the second aspect in the driving device. In FIG. 14, first, the position control unit 51 determines whether or not the current voltage value instructed to the drive unit 52 is in an OFF state, that is, whether or not the voltage value is 0V. If the result of this determination is that it is not in the off state, the position control unit 51 executes the next process S21. If the result of the determination is that it is in the off state, the position control unit 51 A control signal for instructing the drive unit 52 to set a voltage value Eoffset that is preset as a start-up voltage value as a default is generated, and this control signal is output to the drive unit 52. The drive unit 52 drives the drive unit AD so that the voltage value Eoffset represented by this control signal is obtained. For example, in the present embodiment, the voltage value Eoffset is set to 1.5 V, for example.

  Next, the position control unit 51 performs the same processes S21 and S22 as the above-described processes S11 and S12, respectively.

  Next, the movement speed calculation unit 513 of the position control unit 51 determines whether or not the current movement speed Vc is 0 (S31). As a result of this determination, if the current moving speed Vc is not 0 (“No”), the moving speed calculating unit 513 executes the process S23, and if the current moving speed Vc is 0 as a result of the determination ( In “Yes”), the moving speed calculation unit 513 executes the process S32.

  In process S32, the movement speed calculation unit 513 sets the voltage value currently instructed to the drive unit 52 to be increased by 2 V per millisecond. That is, when there is a difference between the current position Pc acquired from the position conversion unit 54 and the target position Pt, the first change amount of the process S24 and the process S25 for changing the moving speed of the moving member 14 (the limit value in this embodiment). The voltage value is changed at 2 V / msec (an example of the second change amount) larger than ΔVmax; ΔEmax = 0.4 V / msec). Note that 2 V / msec is only an example of the second change amount, and the second change amount is appropriately determined in consideration of, for example, the allowable noise level, the first change amount, the individual variation of the drive unit AD, and the like. Is set. Next, the moving speed calculation unit 513 determines whether or not the voltage value increased by 2V exceeds the maximum voltage value 2.8V of the piezoelectric element 12 (S33). As a result of this determination, when the voltage value increased by 2 V exceeds the maximum voltage value 2.8 V of the piezoelectric element 12 (“Yes”), the moving speed calculation unit 513 performs predetermined error processing set in advance. Is executed (S34), and the current process is terminated. As a result of the determination, when the voltage value increased by 2V does not exceed the maximum voltage value 2.8V of the piezoelectric element 12, that is, when the voltage value increased by 2V is equal to or less than the maximum voltage value 2.8V of the piezoelectric element 12. For (“No”), the moving speed calculation unit 513 returns the process to the process 31.

  On the other hand, in the process S23, the moving speed calculation unit 513 performs the same process as the above-described process S13, and thereafter executes the same processes S24, S25 to S27 as the above-described processes S14, S15 to S17, respectively.

  When the processes S24, S25 to S27 are completed, the position difference Psub becomes 0 and the target moving speed Vt becomes 0, that is, the moving member 14 moves to the target position Pt. The process returns to the process S21 in order to execute the processes S24, S25 to S27 and S31 to S34 until it is determined that the process has been reached.

  Such an imaging device ID and driving unit (driving device) AD is a second larger than the first change amount when the moving speed of the moving member 14 is zero, that is, when the moving member 14 is stopped. Since the voltage value is changed by the change amount, the dead zone can be exceeded and the movement can be started in a shorter time.

  FIG. 15 is a diagram showing a relationship of the second mode between the position difference Psub and the target moving speed Vt in the driving device AD. In FIG. 15, the horizontal axis represents the position difference Psub, and the vertical axis represents the target moving speed Vt.

  In the above-described embodiment (in the case of the flowchart shown in FIG. 12 and in the case of the flowchart shown in FIG. 14), the relationship between the position difference Psub and the target moving speed Vt is that the position difference Psub is zero. The target moving speed Vt is also 0, and as the position difference Psub increases from 0, the target moving speed Vt increases substantially from 0, but the difference between the position difference Psub and the target moving speed Vt increases. As shown in FIG. 15, when the position difference Psub is equal to or smaller than a predetermined threshold Sth, the target movement speed Vt is set to zero, and the target movement increases as the position difference Psub increases from the threshold Sth. The speed Vt may be a relationship that increases from 0 in a substantially proportional manner. In such a case, the position control unit 51 includes the current position Pc acquired from the position detection unit (the magnet 23, the hall element 22, and the position conversion unit 54) and the predetermined target input from the control target position setting unit 53. When the difference (position difference) Psub from the position Pt is equal to or less than the predetermined threshold value Sth, the target moving speed Vt is set to zero. In such a driving unit (driving device) AD, when the current position Pc of the moving member 14 approaches the target position Pt, the target moving speed Vt becomes zero. Therefore, for example, the detection result of the position detecting unit varies due to the influence of noise or the like. Even in this case, the so-called overshoot in which the moving member 14 exceeds the target position Pt can be suppressed.

  FIG. 16 is a diagram illustrating a relationship of a second mode between the current moving speed and the speed change amount in the driving device. In FIG. 16, the horizontal axis represents the current moving speed, and the vertical axis represents the speed change amount Δv.

  In the embodiment described above (in the case of the flowchart shown in FIG. 12 and in the case of the flowchart shown in FIG. 14), the limit value ΔVmax is a constant value regardless of the current moving speed, but the moving member (lens holding frame). 14 may be changed according to the moving speed V. For example, the limit value ΔVmax is changed so as to increase as the moving speed V of the moving member 14 increases, as shown in FIG. In such a case, the position control unit 51 operates to change the limit value ΔVmax according to the moving speed V of the moving member 14. In the above-described case, the movement speed change amount limiting unit 514 of the position control unit 51 sets the limit value ΔVmax so as to increase as the moving speed V of the moving member 14 increases. In such a case, the limit value ΔVmax is given in advance as shown in FIG. 16, for example, and is held in the moving speed change amount limiting unit 514 in, for example, a lookup table format or a function format, for example.

  Since such a drive unit (drive device) AD changes the limit value ΔVmax according to the moving speed V, the moving speed V can be changed with a suitable limit value ΔVmax according to the moving speed V.

  In addition, the noise in the so-called SIDM drive device AD tends to increase as the jerk increases, so that the noise is relatively large during start-up and stop when the jerk is relatively large. Become. On the other hand, once the moving member 14 starts to move, the jerk decreases, so that the noise reduction can be maintained even if the limit value ΔVmax is increased. Therefore, since the limit value ΔVmax increases as the moving speed V of the moving member 14 increases, the driving device AD can reach the target position Pt in a shorter time while being quiet.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

SP mobile phone ID imaging unit (imaging device)
AD drive unit (drive device)
EC drive circuit ΔVmax limit value 11 base 12 electromechanical transducer 13 drive member 14 moving member 51 position control unit 511 target speed calculation unit 512 current speed calculation unit 513 movement speed calculation unit 514 movement speed change amount limiting unit

Claims (6)

An electromechanical transducer that converts electrical energy into elastic mechanical energy;
A driving member connected to one end of the electromechanical conversion element in the direction of expansion and contraction, to which the mechanical energy is transmitted;
A moving member engaged with the driving member with a predetermined frictional force;
A position detector for detecting the position of the moving member;
A position controller that moves the moving member to a predetermined target position,
The position control unit repeatedly acquires the position of the moving member detected by the position detection unit from the position detection unit, and for each position of the moving member repeatedly acquired from the position detection unit, the position detection unit When moving the moving member to change the moving speed of the moving member to a target moving speed corresponding to the difference between the position acquired from the predetermined target position and the moving speed of the moving member per unit time The drive device is characterized in that the change amount is changed to be equal to or less than a predetermined limit value. The drive device according to claim 1, wherein the position control unit changes the limit value according to a moving speed of the moving member. The drive device according to claim 2, wherein the limit value increases as the moving speed of the moving member increases. The position control unit sets the target moving speed to zero when the difference between the position acquired from the position detection unit and a predetermined target position is a predetermined threshold value or less. Item 4. The driving device according to any one of Items 3 to 3. The position control unit changes a moving speed of the moving member by changing a voltage value of electric energy supplied to the electromechanical transducer, and the voltage value in the case where the moving speed of the moving member is zero. The second change amount is larger than the first change amount of the voltage value when the moving speed of the moving member is changed when there is a difference between the position acquired from the position detection unit and a predetermined target position. The drive device according to any one of claims 1 to 4, wherein the drive device is characterized. A driving device according to any one of claims 1 to 5,
An image sensor that converts an optical image into an electrical signal;
An imaging optical system that includes one or a plurality of optical elements, and that forms an optical image of an object on a light receiving surface of the imaging element;
An imaging device, wherein an optical element that moves along an optical axis direction among the one or more optical elements in the imaging optical system is attached to the moving member of the driving device.

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