JP2007043843A - Drive device and drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive technology that achieves sufficient low-speed drive and the smooth change of drive speed. <P>SOLUTION: This drive device can drive a drive unit engaged to a drive shaft that reciprocates, in conjunction with the expansion and contraction operation of a piezoelectric element by a friction force. In the dive device, a voltage applied to the piezoelectric element is repeatedly changed into a maximum value (+Vp), into an intermediate value 1 (0 V), into a minimum value (-Vp), and into an intermediate value 2 (0 V). At that time, voltage application timings of the maximum value and the minimum value are shifted from each other, by complementarily increasing and decreasing the time (second period tc) when the voltage of the intermediate value 1 is applied, and the time (fourth period td), when the voltage of the intermediate value 2 is applied; and the drive speed of the drive unit is changed by complementarily changing times (first period tb and third period ta), when the voltages of the maximum value and the minimum value are applied. Accordingly, the satisfactory low-speed drive of the drive unit and the smooth change of the drive speed are achieved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a driving technique having an electromechanical transducer that expands and contracts in response to application of a voltage.

  Various types of driving devices using electromechanical transducers such as piezoelectric elements have been proposed.

  For example, in the element-fixing type driving device schematically shown in FIGS. 14A to 14C, one end of the piezoelectric element 92 that is an electromechanical conversion element is fixed to the fixing member 91 and driven to the other end. A friction member 94 is fixed. The drive friction member 94 moves in the steering direction and the return direction as the piezoelectric element 92 expands and contracts. A moving body 93 is engaged with the driving friction member 94 by a frictional force.

  A voltage is applied to the piezoelectric element 92, and the moving body 93 is driven by expanding and contracting the piezoelectric element 92 at different speeds during expansion and contraction. FIGS. 14A to 14C show the respective states in Pa, Pb, and Pc when the operation waveform voltage shown in FIG. 15 is applied.

  When the voltage waveform rises gently in the section Pa-Pb in FIG. 15, the piezoelectric element 92 relatively slowly expands and changes from the state of FIG. 14A to the state of FIG. 14B. At this time, the moving body 93 substantially moves integrally with the driving friction member 94 without slipping or hardly slipping with respect to the driving friction member 94.

  Next, when the voltage waveform suddenly drops in the section Pb-Pc, the piezoelectric element 92 contracts relatively suddenly, and the driving friction member 94 suddenly returns to the initial position. At this time, slip occurs between the driving friction member 94 and the moving body 93, the moving body 93 does not substantially move, and only the driving friction member 94 returns to the initial position. As a result, as shown in FIG. 14C, the moving body 93 moves in the operation direction with respect to the initial position in FIG.

  By repeating this cycle, the moving body 93 moves along the driving friction member 94.

  If a voltage having a return waveform composed of a sudden rise and a gentle fall is applied to the piezoelectric element, the moving body 93 moves in the return direction.

  There are the following two methods for applying a sawtooth waveform voltage to the piezoelectric element 92.

  FIG. 16 shows the first method. As shown in FIG. 16 (a), the digital / analog converter of the waveform generator 95 generates a sawtooth waveform of, for example, 8 bits and 0-5V, which is input to the power amplifier 96 and amplified to, for example, 0-10V. A sawtooth waveform for driving is applied to the piezoelectric element Pv. By adjusting the waveform generator 95, it is possible to generate a feed-out waveform shown in FIG. 16 (b) and a return sawtooth waveform shown in FIG. 16 (c).

  17 and 18 show the second method. As shown in FIG. 17, in order to apply the voltage of the power source 97 to the piezoelectric element Pv, a circuit including constant current circuits 98a and 98b and switch circuits 99a and 99b is used, and the constant current circuits 98a and 98b and switch circuit 99a are used. , 99b are alternately operated to generate a feeding waveform and a return waveform.

  Specifically, for example, the digital circuit shown in FIG. 18A is configured, and a control signal as shown in FIG. 18B is input to the terminals Ra to Rd, thereby generating a feeding waveform and a return waveform.

  That is, the Hi signal is input to the terminal Ra, the voltage applied to the piezoelectric element Pv is gradually increased through the constant current circuit 98a, the Hi signal is input to the terminal Rb, and the piezoelectric element is input through the switch circuit 99b. Pv is grounded, and the voltage applied to the piezoelectric element Pv is suddenly lowered to generate a feeding waveform Ha.

  Further, by inputting a Hi signal to the terminal Rc and applying the voltage of the power source 97 to the piezoelectric element Pv through the switch circuit 99a, the Hi signal is input to the terminal Rd and grounded through the constant current circuit 98b. A return waveform Hb is generated.

  However, in the first method, the waveform generator 95 and the power amplifier 96 are necessary, and in the second method, the constant voltage circuits 98a and 98b and the switch circuits 99a and 99b are necessary. Also gets higher.

  Therefore, a driving device having a simple circuit configuration has been proposed (see Patent Document 1). In this drive device, drive control is performed using three voltage values (maximum value, minimum value, and intermediate value) as voltages applied to the piezoelectric elements.

JP 2004-80964 A

  However, in the drive device of the above-mentioned Patent Document 1, although a certain low speed drive is possible using the maximum value, the minimum value, and the intermediate value, it is required for further low speed drive required when performing servo control or the like. It is difficult to respond. Also, it is difficult to smoothly change the driving speed from the feeding direction (forward direction) to the returning direction (reverse direction).

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a driving technique capable of sufficiently driving at a low speed and smoothly changing the driving speed.

  In order to solve the above-mentioned problems, the invention of claim 1 is a drive device, comprising: (a) an electromechanical conversion element that expands and contracts in response to application of a voltage; A predetermined member that reciprocally moves in conjunction, and (c) engages the predetermined member with frictional force, and can move relative to the predetermined member by the expansion and contraction of the electromechanical transducer. (D) an output cycle for selectively outputting a voltage value of 1 from a first voltage value, a second voltage value lower than the first voltage value, and a third voltage value lower than the second voltage value; And a voltage applying means for applying a voltage to the electromechanical conversion element. The output cycle first outputs the first voltage value in a first period, and the second voltage in the next second period. Output the third voltage value in a third period after outputting the value, The second voltage value is output in a later fourth period, and the voltage applying means (d-1) changes the length of the first period to the fourth period, In addition to speed changing means for changing the moving speed of the movable part relative to a predetermined member, the speed changing means shortens the third period and the fourth period when the second period is increased. When the first period is lengthened and the second period is shortened, the third period and the fourth period are lengthened and the first period is shortened.

  According to a second aspect of the present invention, in the drive device according to the first aspect of the invention, the first period and the third period have a complementary increase / decrease relationship, and the second period The fourth period has a complementary increase / decrease relationship.

  According to a third aspect of the present invention, there is provided a drive system having the drive device according to the first or second aspect of the present invention, wherein a predetermined drive mechanism in a camera is driven by the drive device.

  According to a fourth aspect of the invention, in the drive system according to the third aspect of the invention, the predetermined drive mechanism is a camera shake correction mechanism.

  According to the first to fourth aspects of the invention, a voltage value of 1 is selectively output from the first voltage value, the second voltage value lower than the first voltage value, and the third voltage value lower than the second voltage value. First, the first voltage value is output in the first period, the second voltage value is output in the next second period, the third voltage value is output in the third period, and the last fourth period. The output cycle for outputting the second voltage value is repeated, and a voltage is applied to the electromechanical transducer. Here, when the second period is lengthened, the third period and the fourth period are shortened and the first period is lengthened, and when the second period is shortened, the third period and the fourth period are lengthened. In addition, the first period is shortened. As a result, it is possible to sufficiently drive at a low speed and smoothly change the driving speed.

  In particular, in the invention of claim 2, the first period and the third period have a complementary increase / decrease relationship, and the second period and the fourth period have a complementary increase / decrease relationship. Therefore, it is possible to drive at a sufficiently low speed and change the driving speed more smoothly.

  In the invention of claim 3, since the predetermined driving mechanism in the camera is driven by the driving device, the size of the camera can be reduced.

  In the invention of claim 4, since the predetermined drive mechanism is a camera shake correction mechanism, the camera shake correction mechanism can be downsized.

<Configuration of drive device>
FIG. 1 is a diagram showing a main configuration of a drive device 1 according to an embodiment of the present invention. Here, FIG. 1A is an exploded perspective view relating to the drive device 1, and FIG. 1B is an assembly perspective view relating to the drive device 1.

  The drive device 1 includes a fixed member 10 attached to a fixed portion of an apparatus, for example, a base (not shown) of an XY drive table, a laminated piezoelectric element 11, and a drive shaft that is slidably supported by the fixed member 10. 12 and a drive unit 13 coupled to a driven part, for example, a stage (not shown) of an XY drive table.

  One end face of the piezoelectric element 11 in the expansion / contraction direction is fixedly coupled to the fixing member 10, and one end face of the drive shaft 12 functioning as a drive friction member (predetermined member) is connected to the other end face of the expansion / contraction direction. It is firmly connected.

  A drive unit (movable part) 13 including a slider 13a, a friction member 13b, and a leaf spring 13c is engaged with the drive shaft 12 by a frictional force.

  In the drive device 1, the drive unit 13 is moved relative to the drive shaft 12 by reciprocating the drive shaft 12 in the axial direction in conjunction with the expansion / contraction operation of the piezoelectric element 11 that expands and contracts in response to voltage application by the drive circuit 2. Movement is possible.

  FIG. 2 is a diagram illustrating a circuit configuration of the drive circuit 2.

  The drive circuit 2 includes a control circuit 20 and four switch elements Q <b> 1 to Q <b> 4 and applies a voltage between the terminals of the piezoelectric element 11.

  The switch elements Q1 to Q4 are configured as MOS FETs, and each gate is connected to each of the terminals Sc1 to Sc4 of the control circuit 20 and receives a Hi signal or a Lo signal.

  The switch elements Q1 and Q3 are configured as P-channel FETs. When a Lo signal is input to the gate, the source and drain are turned on (conductive state), and when a Hi signal is input to the gate, the source and drain are turned on. It is off (interrupted state). The switch elements Q2 and Q4 are configured as N-channel FETs. When a Hi signal is input to the gate, the source and drain are turned on (conductive state), and when the Lo signal is input, the source and drain are turned on. It is off (interrupted state).

  The source of the switch element Q1 and the source of the switch element Q3 are connected to the power supply voltage Vp via the connection point 21, respectively. The drain of the switch element Q1 is connected to the drain of the switch element Q2 through the connection point 22, and the drain of the switch element Q3 is connected to the drain of the switch element Q4 through the connection point 23. The source of the switch element Q2 and the source of the switch element Q4 are grounded via the connection point 24, respectively. Furthermore, each terminal of the piezoelectric element 11 is connected to the connection points 22 and 23, respectively.

<Operation of Drive Device 1>
The operation of the driving device 1 having the above configuration will be described below. Regarding the control of the driving speed, (i) speed control by adjusting the time width in the driving waveform, (ii) speed control by thinning the driving signal, (iii) The speed control combining these will be described in order.

(i) Speed Control by Time Width Adjustment with Drive Waveform First, the driving principle by time width adjustment with a drive waveform will be described with reference to FIG. Here, FIG. 3A shows the voltages of the terminals Sc1 and Sc2 of the control circuit 20 (that is, the gate voltages of the switch element Q1 and the switch element Q2). FIG. 3B shows the voltages at the terminals Sc3 and Sc4 of the control circuit 20 (that is, the gate voltages of the switch element Q3 and the switch element Q4). FIG. 3C shows the drive voltage Vload applied between the terminals of the piezoelectric element 11. In this drive voltage Vload, the direction indicated by the arrow Dc in FIG. 2 is positive.

  In the driving device 1, the drive unit 13 can be driven in the operation direction or the return direction by repeating a cycle of a period Te including a first period to a fourth period described later, and the length of the first period to the fourth period is set. By changing it, the moving speed of the drive unit 13 relative to the drive shaft 12 can be changed. In addition, about the signal shown by Fig.3 (a)-(c), it is an example at the time of driving the drive unit 13 to a pay-out direction.

  First, in the first period tb, the terminal Sc1 and the terminal Sc2 become Lo as in the signal Ja shown in FIG. 3A, and the terminal Sc3 and the terminal Sc4 continue to be in the Hi state as shown in FIG. 3B. . With such a signal state in the first period tb, in the drive circuit 2, the switch element Q1 and the switch element Q4 are turned on and the switch element Q2 and the switch element Q3 are turned off. As a result, the connection point 23 is grounded via the switch element Q4, and the connection point 22 is connected to the power supply voltage Vp via the switch element Q1, so that the drive voltage Vload across the piezoelectric element 11 is as shown in FIG. It becomes + Vp (maximum value) corresponding to the power supply voltage like a signal Ka shown in c).

  In the next second period tc, the terminal Sc1 and the terminal Sc2 become Hi as shown in FIG. 3A, and the terminal Sc3 and the terminal Sc4 continue to be in the Hi state as shown in FIG. 3B. Due to such a signal state in the second period tc, in the drive circuit 2, the switch element Q1 and the switch element Q3 are turned off and the switch element Q2 and the switch element Q4 are turned on. As a result, the connection point 22 is connected to the connection point 23 via the switch element Q2 and the switch element Q4, and the terminals of the piezoelectric element 11 are short-circuited, so that the drive voltage Vload across the piezoelectric element 11 is as shown in FIG. It becomes 0 volt (intermediate value 1) like the signal Kb shown in c).

  In the third period ta, the terminal Sc1 and the terminal Sc2 are continuously in the Hi state as shown in FIG. 3A, but the terminal Sc3 and the terminal Sc4 are Lo and the signal Jb shown in FIG. Become. By such a signal state in the third period ta, the switch element Q1 and the switch element Q4 are turned off and the switch element Q2 and the switch element Q3 are turned on. As a result, the connection point 22 is grounded via the switch element Q2, and the connection point 23 is connected to the power supply voltage Vp via the switch element Q3. Therefore, the drive voltage Vload is the signal Kc shown in FIG. -Vp (minimum value).

  In the final fourth period td (td = Te−ta−tb−tc), the terminal Sc1 and the terminal Sc2 are continuously in the Hi state as shown in FIG. 3A, but as shown in FIG. The terminal Sc3 and the terminal Sc4 are Hi. By such a signal state in the fourth period td, the switch element Q1 and the switch element Q3 are turned off and the switch element Q2 and the switch element Q4 are turned on. As a result, the connection point 22 is connected to the connection point 23 via the switch element Q2 and the switch element Q4, and the terminals of the piezoelectric element 11 are short-circuited, so that the drive voltage Vload is the signal Kd shown in FIG. Thus, 0 volt (intermediate value 2) is obtained.

  As described above, in the drive circuit 2, the maximum value (first voltage value) + Vp corresponding to the power supply voltage Vp, the intermediate value (second voltage value) 0V lower than the maximum value, and the minimum value (third voltage value) lower than the intermediate value. ) The output cycle for selectively outputting a voltage value of 1 from −Vp is repeated, and a voltage is applied to the piezoelectric element 11. Thus, as shown in FIG. 3, the drive unit 13 is sent together with the drive shaft 12 in the extending direction by two rising signals Ku and Kv whose timings are relatively separated in one cycle period Te of the drive voltage Vload. On the other hand, the drive shaft 12 is displaced relatively steeply in the return direction by two falling signals Ks and Kt whose timings are relatively close in one cycle period Te of the drive voltage Vload. At this time, the drive unit 13 tries to move in the return direction, but the movement amount (return amount) is smaller than the movement amount sent in the feeding direction. By repeating such an operation, the drive unit 13 can be driven along the drive shaft 12 in the steering direction.

  Here, the total time (ta + tb) of the first period and the third period is constant without changing the one cycle period Te, and the total time (tc + td) of the second period tc and the fourth period td is constant. When the second period tc is increased, the first period tb is also increased at the same time. That is, when the second period tc is lengthened, the third period ta and the fourth period td are shortened and the first period tb is lengthened, and when the second period tc is shortened, the third period ta and the second period tc are shortened. The four periods td are lengthened and the first period tb is shortened. When the lengths of the first period tb and the third period ta are equal, the lengths of the second period tc and the fourth period td are made equal. As a result, the drive waveform in the feeding direction with respect to the drive unit 13 can be continuously changed to the drive waveform in the return direction through a neutral state in which the drive unit 13 does not move in either the feeding direction or the return direction. The drive speed of the drive unit 13 can be changed smoothly. The speed control method by adjusting the time width with the drive waveform will be described in detail.

  4 (a) to (i) and FIGS. 5 (a) to (l) are diagrams for explaining the speed control by adjusting the time width in the drive waveform, and the speed and drive direction of the drive unit 12 are stepped. The drive waveform in the case of changing it continuously is shown.

  4A to 4C show drive waveforms when the second period tc = 0 is set in FIG. In this drive waveform, as shown in FIG. 4C, the fall signal Ma of the drive voltage Vload is the steepest, so that the drive unit 12 maintains the current position with almost no movement in the return direction. Therefore, in such a case, the moving speed V0 of the drive unit 13 is maximum in the feeding direction.

  Next, as shown in FIGS. 4D to 4F, the time intervals of the rising signals Md and Me at the driving voltage Vload are shortened, and the time intervals of the falling signals Mb and Mc are extended by the shortened amount, thereby driving. The feed amount in the feeding direction due to the rise of the voltage Vload is decreased, and the feed amount in the return direction due to the fall of the drive voltage Vload is increased. As a result, the drive speed of the drive unit 13 can be made relatively slower than in the case of the drive waveform shown in FIG.

  Similarly, as shown in FIGS. 4G to 4I, the time interval between the rising signals Mh and Mi in the driving voltage Vload is shortened to extend the time interval between the falling signals Mf and Mg, thereby driving the driving unit in the feeding direction. The drive speed of 13 can be reduced.

  Furthermore, when the time interval of the rising signal in the drive voltage Vload is shortened and the time interval of the falling signal is extended, these time intervals become equal (FIGS. 5A to 5C). At this time, in the drive voltage Vload, the period of the signal Mj that outputs + Vp (first period) tb3 and the period of the signal Mm that outputs −Vp (third period) ta3 are equal to each other. The time between the period tb and the third period ta is adjusted smoothly, and the waveform of the signals Sc1 and Sc2 shown in FIG. 5A and the waveform of the signals Sc3 and Sc4 shown in FIG. To be.

  As a result, the amount of drive unit 13 that is driven by the rising signals Mn and Mo of the drive voltage Vload is equal to the amount of return of the drive unit 13 that is generated by the falling signals Mk and Ml of the drive voltage Vload. V3 becomes almost 0 and shifts to a stationary state.

  From this stationary state, by further shortening the time interval of the rising signal and extending the time interval of the rising signal at the driving voltage Vload, the waveforms of the driving signals shown in FIGS. 5D to 5F and FIG. The waveform of the drive signal shown in (i) is generated. Due to these drive waveforms, in the drive unit 13, unlike the drive state in the feed direction shown in FIG. 4, the return amount by the falling signal becomes larger than the feed amount by the rising signal. ) Driving speed V3 based on the driving waveform and driving speed V4 (V4> V3) based on the driving waveforms shown in FIGS.

  Then, when the rising signal time interval is further shortened to set the fourth period td = 0, the driving waveforms shown in FIGS. 5J to 5L are generated in which the rising signal Mp of the driving voltage Vload is the steepest. . Here, the signal waveforms of FIG. 5 (j) and FIG. 5 (k) replace the signal waveforms of Sc1 and Sc2 shown in FIG. 4 (a) with the signal waveforms of Sc3 and Sc4 shown in FIG. 4 (b). It corresponds to a thing. The drive speed of the drive unit 13 driven by such a drive waveform is the maximum speed V6 in the return direction that is substantially equal in magnitude to the maximum speed V0 in the feed direction.

  As described above, the output time of the intermediate value 1 at the drive voltage Vload (second period) and the output time of the intermediate value 2 (fourth period) are increased or decreased complementarily, and at the same time, the maximum value at the drive voltage Vload is output. By increasing or decreasing the time (first period) and the minimum output time (third period) in a complementary manner, the speed of the drive unit 13 can be continuously changed from the feeding direction to the returning direction.

  FIG. 6 shows a graph showing measured values of the driving speed when the time width of the driving waveform is changed by the speed control method described above.

  In FIG. 6, the horizontal axis indicates the control parameter number, and the vertical axis indicates the drive speed of the drive unit 13. The control parameter numbers are the numbers “1” assigned to the control parameters that maximize the driving speed in the feeding direction, as shown in FIGS. 4 (a) to 4 (c). As shown in FIG. 5, each time zone (first time) for outputting the maximum value, the intermediate value 1, the intermediate value 2, and the minimum value up to the number “32” given to the control parameter that maximizes the drive speed in the return direction. To the fourth time), the control parameters at each time when the time is gradually changed are numbered. The control parameter number “16” corresponds to the stationary control of the drive unit 13 shown in FIGS.

  As shown in the graph of FIG. 6, the drive speed of the drive unit 13 is changed substantially linearly and continuously from the feeding direction to the return direction by changing control parameters having different time widths in the first period to the fourth period. It can be changed.

(ii) Speed control by thinning out drive signals In the drive device 1, it is possible to reduce the drive speed of the drive unit 13 while reducing power consumption by performing a thinning process on the drive signals in the control circuit 20. Yes. This will be described in detail below.

  FIG. 7 is a diagram for explaining speed control by thinning out drive signals.

  The drive signal shown in FIG. 7 (a) represents the drive waveform of the period Te shown in FIG. 3 (c) for about a dozen cycles, and is in a state where no thinning process has been performed (state without thinning). Yes.

  On the other hand, the drive signal shown in FIG. 7B is a signal of applied voltages + Vp and −Vp sequentially given to the piezoelectric element 11 and is 1 every cycle (hereinafter also referred to as “thinning cycle”) Tf (= 4 × Te). Thinned out at the rate of times. Here, the amount of movement of the drive unit 13 during one cycle Te by the drive signal shown in FIG. 3C is the amount of feed (feed amount) by the rising signal of the drive waveform and the return amount by the fall signal. It is determined. That is, in the driving signal shown in FIG. 7A, driving for four cycles is performed during the thinning cycle Tf, so that the drive unit 13 moves four times. On the other hand, in the drive signal shown in FIG. 7B, there is a period of one period in which the current position is held without being driven after driving for three periods in the thinning-out period Tf. For this reason, the moving speed of the driving unit 13 is about 3/4 of the driving speed as compared with the case of no thinning shown in FIG.

  The drive signal shown in FIG. 7C is obtained by further thinning the drive signal with respect to FIG. 7B. With this drive signal, driving for two cycles is not performed in the thinning cycle Tf, so that the moving speed of the drive unit 13 is about ½ that of the case without thinning shown in FIG. Note that the drive signal for performing signal thinning twice during the thinning cycle Tf is not limited to the drive signal shown in FIG. 7C, but a half cycle of the thinning cycle Tf as shown in FIG. 7E. Alternatively, it may be configured as a drive signal for performing signal thinning once.

  Further, the drive signal shown in FIG. 7D is obtained by further thinning the drive signal with respect to FIG. 7C. Since this drive signal does not drive for three cycles in the thinning cycle Tf, the moving speed of the drive unit 13 is about ¼ that of the case without thinning shown in FIG.

  In the piezoelectric element 11 used as an actuator, when an applied voltage changes, an energizing current flows and power is consumed. Therefore, by reducing the number of times the applied voltage changes, the power consumption is approximately proportional to the number of reductions. Reductions can be made.

  Therefore, the ratio of the consumption currents when the drive voltages shown in FIGS. 7A to 7D are applied to the piezoelectric element 11 is approximately 1: 3/4: 1/2: 1/4, and the drive unit 13 When driving the at a low speed, the current consumption can be appropriately reduced.

  When thinning processing is performed on the drive signal, by setting the thinning frequency Ff = 1 / Tf to 20 kHz or more which is the upper limit of the audible frequency, generation of unpleasant driving sound can be suppressed and the speed can be reduced. That is, if the thinning frequency Ft is set to 20 kHz or more, even when the thinning timing is different as in the driving signal in FIG. 7C or the driving signal in FIG. 7E, driving without generating driving sound is possible. .

  FIG. 8 shows a graph showing measured values of the drive speed when the speed control is performed by thinning the drive signal described above.

  In FIG. 8, the horizontal axis indicates the thinning rate, and the vertical axis indicates the drive speed of the drive unit 13. With respect to this thinning rate, each case in which the thinning rate related to the drive signal in FIG. 4C at which the driving speed in the feeding direction is maximum is increased by 1/4 from “no thinning” to “3/4 thinning”, and Each case is shown in which the decimation rate for the drive signal in FIG. 5 (l) where the drive speed in the return direction is maximum is decreased by 1/4 from “3/4 decimation” to “no decimation”.

  As shown in the graph of FIG. 8, in the drive device 1, the speed control of the drive unit 13 according to the thinning rate is possible in the feeding direction or the return direction. On the other hand, for the consumption current (average current during driving) of the piezoelectric element at each thinning rate, for example, the measurement result shown in FIG. 9 is obtained, but as described above, the current value corresponds to the thinning rate of the drive signal. Yes. That is, the drive speed and current consumption of the drive unit 13 change approximately in proportion to the thinning rate of the drive signal.

(iii) Speed control combining the speed control of (i) and (ii) The speed control by the time width adjustment with the drive waveform described in (i) above is applied to the drive signal described in (ii) above. Speed control (hereinafter referred to as “hybrid control”) to which speed control by thinning is added will be described below.

  FIG. 10 is a diagram for explaining the hybrid control. The control parameter numbers shown on the horizontal axis in FIG. 10 are obtained by assigning numbers 1 to 17 to the control parameters at each time when the control parameters are changed as in the time width control with the drive waveform shown in FIG. . Then, in the drive signal whose time width is determined by each control parameter, the measured value of each drive speed when the decimation rate is changed by 1/4 from “no decimation” to “3/4 decimation” is plotted in FIG. is doing.

  As shown in the graph of FIG. 10, in the case where the drive speed is controlled by adjusting only the time width of the drive waveform without thinning out, when the speed control by thinning the drive signal is added (hybrid control) Since the speed can be reduced according to the thinning rate, the driving speed can be finely controlled.

  An example of speed control using such hybrid control to gradually decrease the drive speed from the maximum speed in the feeding direction and change it to the maximum speed in the return direction will be described with reference to FIG.

  First, the drive unit 13 is driven at the highest speed in the feeding direction by applying the drive waveform shown in FIG. 4C to the piezoelectric element 13 without thinning out. Next, when the drive speed of the drive unit 13 is gradually reduced, control according to the following procedures (1) to (14) is performed.

  (1) By the speed control by adjusting the time width of the drive waveform, the drive waveform shown in FIG. 4 (f) is changed to the drive waveform shown in FIG. 4 (i). As a result, the driving speed decreases as indicated by an arrow D1 in FIG.

  (2) When the speed decreases to about the driving speed (maximum speed in 1/4 thinning) when 1/4 thinning is performed with the driving waveform shown in FIG. 4C, it is indicated by an arrow D2 in FIG. As described above, the drive waveform is returned to the drive waveform having the time width shown in FIG.

  (3) By the speed control by adjusting the time width of the drive waveform while the drive signal is ¼ thinned out, the drive waveform shown in FIG. 4F is changed to the drive waveform shown in FIG. As a result, the driving speed decreases as indicated by an arrow D3 in FIG.

  (4) When the driving speed shown in FIG. 4C is reduced to the driving speed when 1/2 thinning is performed, the driving waveform shown in FIG. Returning to the drive waveform having the time width shown in FIG.

  (5) The speed is controlled by adjusting the time width of the drive waveform while the drive signal is 1/2 thinned out, and the drive waveform shown in FIG. 4F is changed to the drive waveform shown in FIG. As a result, the driving speed decreases as indicated by an arrow D5 in FIG.

  (6) When the driving speed shown in FIG. 4C decreases to about the driving speed when 3/4 decimation is performed, as shown by an arrow D6 in FIG. Returning to the drive waveform having the time width shown in FIG.

  (7) By controlling the speed by adjusting the time width of the drive waveform while the drive signal is 3/4 thinned out, the drive waveform of FIG. 4 (f) and the drive waveform of FIG. Change to drive waveform. As a result, the drive speed gradually decreases as indicated by an arrow D7 in FIG. 11, and the drive unit 13 is shifted to a stationary state.

  (8) When the drive unit 13 reaches the stationary state, the drive waveform shown in FIG. 5C is changed from the drive waveform shown in FIG. ) And the drive waveform shown in FIG. 5I are changed to the drive waveform shown in FIG. As a result, the drive direction changes to the return direction as indicated by an arrow D8 in FIG. 11, and the speed gradually increases.

  (9) When the time width control is performed up to the drive waveform of FIG. 5 (l), the drive waveform is returned to the drive waveform of the time width shown in FIG. 5 (f) as shown by arrow D9 in FIG. Perform 1/2 decimation.

  (10) The speed is controlled by adjusting the time width of the drive waveform while the drive signal is 1/2 thinned out, and the drive waveform shown in FIG. 5I is changed to the drive waveform shown in FIG. As a result, the drive speed increases in the return direction as indicated by an arrow D10 in FIG.

  (11) When the time width control is performed up to the drive waveform of FIG. 5 (l), the drive waveform is returned to the drive waveform of the time width shown in FIG. 5 (f) as shown by arrow D11 in FIG. Perform 1/4 thinning.

  (12) By the speed control by adjusting the time width of the drive waveform while the drive signal is ¼ thinned out, the drive waveform shown in FIG. 5I is changed to the drive waveform shown in FIG. As a result, the drive speed increases in the return direction as indicated by an arrow D12 in FIG.

  (13) When the time width control is performed up to the drive waveform of FIG. 5 (l), as shown by the arrow D13 in FIG. 11, the drive waveform is returned to the drive waveform of the time width shown in FIG. Control.

  (14) The speed is controlled by adjusting the time width of the drive waveform while the drive signal is not thinned out, and the drive waveform shown in FIG. 5I is changed to the drive waveform shown in FIG. As a result, the drive speed gradually increases as shown by the arrow D14 in FIG. 11, and reaches the maximum speed of the drive unit 13 in the return direction.

  FIG. 12 shows a graph representing measured values of drive speed when such hybrid control is performed.

  In FIG. 12, the horizontal axis indicates the control parameter number, and the vertical axis indicates the drive speed of the drive unit 13. The control parameter numbers are obtained by adding numbers 1 to 31 to the control parameters at each time point when the speed control is performed along arrows D1 to D14 shown in FIG.

  As shown in the graph of FIG. 12, compared with driving speed control only by adjusting the time width of the driving waveform (see FIG. 6), hybrid control has a wider speed range (especially the speed range in the low speed range) and better speed resolution control. That is, fine speed control of the drive unit 13 is possible, and power consumption can be reduced by thinning the drive signal.

  When the voltage applied to the piezoelectric element 11 is repeated as follows: maximum value (+ Vp) → intermediate value 1 (0 V) → minimum value (−Vp) → intermediate value 2 (0 V), The voltage application timing of the maximum value and the minimum value is increased by complementarily increasing / decreasing the time for applying the voltage of value 1 (second period tc) and the time for applying the voltage of intermediate value 2 (fourth period td). In order to change the drive speed of the drive unit 13 by changing the time (first period tb and third period ta) to which the voltage of the maximum value / minimum value is applied in a complementary manner, the drive speed of the drive unit 13 is sufficiently low. The speed can be changed smoothly.

  The driving device 1 described above may be used in a camera shake correction mechanism of a camera (imaging device). The mechanism of such a camera will be specifically described below.

  FIG. 13 is a block diagram illustrating a main configuration of the camera 3 capable of correcting camera shake.

  The camera 3 is configured as a digital camera, for example, and includes a camera shake correction unit 30 that functions as a camera shake correction mechanism, and a camera control unit 34 that is connected to the camera shake correction unit 30 so as to be able to transmit. The camera control unit 34 performs overall control of the operation of the camera 3 except for camera shake correction, and transmits a signal to the camera shake correction unit 30 according to the necessity of camera shake correction to instruct the start and end of camera shake correction.

  The camera shake correction unit 30 includes a drive unit 31, a camera shake correction control unit 32, and a shake detection unit 33 corresponding to the drive device 1.

  The blur detection unit 33 includes, for example, an angular velocity sensor, detects a shake of the camera 3, and outputs a signal corresponding to a change in the shooting direction.

  The camera shake correction control unit 32 obtains a camera shake correction amount based on the signal output from the shake detection unit 33, and outputs a drive signal corresponding to the camera shake correction amount to the drive unit 31. Then, by performing drive control (speed control) of the drive unit 13 based on this drive signal by the drive unit 31, appropriate camera shake correction is performed.

  As described above, by using the driving device 1 including the piezoelectric element in the camera shake correction mechanism of the camera 3, the camera can be reduced in size. Note that the camera can be downsized not only by the camera shake correction mechanism but also by using the driving device 1 in another driving mechanism, for example, a lens driving mechanism of the camera.

<Modification>
In the driving device 1 in the above embodiment, not only the piezoelectric element but also electricity that converts electrical energy such as voltage, current, electric field, magnetic field, and static electricity into mechanical energy such as stretching, bending, twisting, and distortion. Mechanical conversion elements such as electrostrictive elements, magnetostrictive elements, electrostatic actuators and the like may be used.

It is a figure which shows the principal part structure of the drive device 1 which concerns on embodiment of this invention. 2 is a diagram illustrating a circuit configuration of a drive circuit 2. FIG. 4 is a diagram for explaining the operation of a control circuit 20. FIG. It is a figure for demonstrating speed control by time width adjustment with a drive waveform. It is a figure for demonstrating speed control by time width adjustment with a drive waveform. It is a figure showing the measured value of the drive speed at the time of performing speed control by time width adjustment with a drive waveform. It is a figure for demonstrating speed control by thinning-out of a drive signal. It is a figure showing the measured value of the drive speed at the time of performing speed control by thinning-out of a drive signal. It is a figure for demonstrating the relationship between the thinning-out rate of a drive signal, and the consumption current of a piezoelectric element. It is a figure for demonstrating hybrid control. It is a figure which shows an example of hybrid control. It is a figure showing the measured value of the drive speed at the time of performing hybrid control. It is a block diagram which shows the principal part structure of the camera 3 in which camera shake correction is possible. It is a figure for demonstrating the drive device based on the prior art of this invention. It is a figure for demonstrating the drive device based on the prior art of this invention. It is a figure for demonstrating the drive device based on the prior art of this invention. It is a figure for demonstrating the drive device based on the prior art of this invention. It is a figure for demonstrating the drive device based on the prior art of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive apparatus 2 Drive circuit 3 Camera 11, 92, Pv Piezoelectric element 12 Drive shaft 13 Drive unit 20 Control circuit 30 Camera shake correction unit 31 Drive part 32 Camera shake correction control part 33 Shake detection part Q1-Q4 Switch element Sc1-Sc4 Control circuit Terminal

Claims (4)

A driving device comprising:
(a) an electromechanical transducer that expands and contracts in response to application of voltage;
(b) a predetermined member that reciprocates in conjunction with the expansion and contraction of the electromechanical transducer,
(c) a movable portion that engages with the predetermined member with a frictional force, and is movable relative to the predetermined member by an expansion / contraction operation of the electromechanical conversion element;
(d) repeating an output cycle for selectively outputting one voltage value from the first voltage value, the second voltage value lower than the first voltage value, and the third voltage value lower than the second voltage value; Voltage applying means for applying a voltage to the mechanical conversion element;
With
The output cycle first outputs the first voltage value in a first period, outputs the second voltage value in the next second period, and then outputs the third voltage value in a third period. And a cycle for outputting the second voltage value in the last fourth period,
The voltage applying means includes
(d-1) Speed changing means for changing the moving speed of the movable part relative to the predetermined member by changing the length of the first period to the fourth period,
And having
In the speed changing means, when the second period is lengthened, the third period and the fourth period are shortened, the first period is lengthened, and when the second period is shortened, the first period is shortened. 3. A driving device characterized in that the three periods and the fourth period are lengthened and the first period is shortened. The drive device according to claim 1,
The first period and the third period have a complementary increase / decrease relationship,
The driving apparatus according to claim 1, wherein the second period and the fourth period have a complementary increase / decrease relationship. A drive system comprising the drive device according to claim 1 or 2,
A drive system, wherein a predetermined drive mechanism in a camera is driven by the drive device. The drive system according to claim 3, wherein
The drive system according to claim 1, wherein the predetermined drive mechanism is a camera shake correction mechanism.

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