JP2008167573A - Moving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moving device that has reduced time lag, starting from a start of driving a piezoelectric oscillator, when moving a driven body. <P>SOLUTION: The moving device includes the piezoelectric oscillator. The moving device further includes a circuit part that applies a first AC voltage to excite an expansion/contraction mode oscillation and a second AC voltage that excites bending mode oscillations, relative to the piezoelectric oscillator. In order to move the driven body by an elliptical motion, based on the expansion/contraction mode oscillation and the bending mode oscillation of the piezoelectric oscillator, the circuit part starts applying the second AC voltage, until the point t3 when the amplitude of the first AC voltage becomes constant, after a time point t1 when the first AC voltage is applied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a moving device, and more particularly, to a moving device that efficiently moves a driven body.

There has been proposed a moving device that moves a driven body in an arbitrary one-dimensional direction using a piezoelectric vibrator. Patent Document 1 discloses a moving device that starts driving the other actuator when vibration of one actuator reaches a steady state.
JP 08-237970 A

  However, since the device of Patent Document 1 starts driving the other actuator after the vibration of one actuator reaches a steady state, the movement of the driven body starts after the driving of one actuator starts. It takes time to be done.

  Accordingly, an object of the present invention is to provide a moving device that reduces a time lag from the start of driving of a piezoelectric vibrator when moving a driven body.

  A moving device according to the present invention includes a piezoelectric vibrator, and a circuit unit that applies a first AC voltage that excites a stretching mode vibration and a second AC voltage that excites a bending mode vibration to the piezoelectric vibrator. The circuit unit is configured to apply the first AC voltage after applying the first AC voltage in order to move the driven body by the elliptical motion based on the expansion mode vibration and the bending mode vibration of the piezoelectric vibrator. The application of the second AC voltage is started before the amplitude reaches a steady state.

  Preferably, the circuit unit includes a detection unit that detects the amplitude of the first AC voltage, and an application control unit that starts application of the second AC voltage when the amplitude is equal to or greater than a predetermined value.

  More preferably, the application control unit starts applying the second AC voltage when the amplitude of the first AC voltage becomes half of the amplitude in the steady state.

  Preferably, the piezoelectric vibrator is energized by the driven body, and the application start timing of the second AC voltage is an expansion / contraction mode excited by application of the first AC voltage from the start of application of the first AC voltage. This corresponds to the time until the force at which the piezoelectric vibrator presses the driven body by the vibration exceeds the force to be biased.

  As described above, according to the present invention, it is possible to provide a moving device that reduces the time lag from the start of driving of the piezoelectric vibrator when moving the driven body.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The moving device includes a movable unit having the horizontal moving unit 10 and a fixed unit having the piezoelectric vibrator 30, the fixed base 50, and the circuit unit 70. In order to describe the direction, in the moving device, the moving direction of the horizontal moving unit 10 is the first direction x, the urging direction of the piezoelectric vibrator 30 orthogonal to the first direction x is the second direction y, and the first A direction orthogonal to the direction x and the second direction y will be described as a third direction z.

  The horizontal movement unit (driven body) 10 includes first and second friction members 11 and 12 and a horizontal movement frame 19. The horizontal movement unit 10 is movable in the first direction x. Therefore, by fixing a member to be moved to the horizontal movement unit 10, the member can be moved in the first direction x.

  The first and second friction members 11 and 12 have a rectangular parallelepiped shape, and one of the planes perpendicular to the second direction y is in contact with the piezoelectric vibrator 30, and the horizontal moving frame 19 is caused by the vibration of the piezoelectric vibrator 30. At the same time, it is movable in the first direction x, and the other is attached inside the horizontal movement frame 19.

  The horizontal movement frame 19 is a flat frame having a rectangular hole on the inner side and perpendicular to the third direction z, and the first and second friction members 11 and 12 are attached to the inner rectangular hole, and a piezoelectric body. A vibrator 30 is arranged.

  The piezoelectric vibrator 30 includes first and second piezoelectric elements (piezoelectric ceramic rings) 31 and 32 having a hollow cylindrical shape, and a shim 34 formed of a thin metal elastic plate. The first and second piezoelectric elements 31 and 32 are fixed to the outer wall portion and the upper and lower surfaces perpendicular to the third direction z (see FIG. 2).

  Electrodes are provided on the surfaces of the first and second piezoelectric elements 31 and 32 viewed from the third direction z. The electrodes are divided into three when viewed from the third direction z, and the first, second, and third electrodes 31a, 31b, and 31c of the first piezoelectric element 31 and the fourth, fifth, and sixth electrodes of the second piezoelectric element 32 are divided. 32a, 32b, and 32c are attached. The electrode and the piezoelectric element may be attached to only one of the upper surface and the lower surface of the shim 34, but the form attached to both surfaces as in this embodiment is stronger. A driving force can be obtained.

  The first to third electrodes 31a to 31c are arranged side by side in the first direction x. The second electrode 31b used for applying the first AC voltage VE1 for exciting the expansion / contraction mode vibration is disposed at the center on the shim body 34a (first piezoelectric element 31). The first and third electrodes 31a and 31c used for applying the second AC voltage VE2 for exciting the bending mode vibration are end portions in the first direction x on the shim main body 34a (first piezoelectric element 31). It is arrange | positioned at the outer peripheral part containing. The first and third electrodes 31 a and 31 c are arranged in a positional relationship facing the center on the xy plane of the piezoelectric vibrator 30 on the xy plane.

  The second electrode 31b and the fifth electrode 32b are arranged to face each other in the third direction z, and the first AC voltage VE1 having the same waveform is applied from the expansion / contraction mode vibration input unit 74 of the circuit unit 70. The first electrode 31 a and the fourth electrode 32 a are arranged to face each other in the third direction z, and the second AC voltage VE <b> 2 having the same waveform is applied from the bending mode vibration input unit 73 of the circuit unit 70. The third electrode 31c and the sixth electrode 32c are arranged to face each other in the third direction z, and the second AC voltage VE2 having the same waveform is applied from the bending mode vibration input unit 73 of the circuit unit 70.

  The first to third electrodes 31 a to 31 c are arranged, and the first piezoelectric element 31 is configured with an electrode group having a perfect circular ring shape (donut shape). The fourth to sixth electrodes 32 a to 32 c are arranged, and the second piezoelectric element 32 constitutes an electrode group having a perfect circular ring shape (donut shape).

  By applying the first AC voltage VE1 to the second and fifth electrodes 31b and 32b, the piezoelectric vibrator 30 expands and contracts in the radial direction (radiation direction from the center of the upper surface and the lower surface of the shim body 34a to the outer wall). Stretch mode vibration is excited. By applying the second AC voltage VE2 to the first, third, fourth, and sixth electrodes 31a, 31c, 32a, and 32c, the bending mode vibration in which the piezoelectric vibrator 30 bends in the first direction x is excited. The

  The application of the second AC voltage VE2 to the first, third, fourth, and sixth electrodes 31a, 31c, 32a, and 32c for exciting the bending mode vibration is the second for exciting the stretching mode vibration. After the start of application of the first AC voltage VE1 to the five electrodes, the expansion mode vibration is started until the steady state is reached. The voltage application start timing control will be described later.

  The shim 34 includes a hollow cylindrical shim main body 34a in which the first and second piezoelectric elements 31 and 32 are fixed to both surfaces, and first, second, third, and fourth support portions 35a supported by the fixing base 50. 35b, 35c, and 35d (see FIGS. 2 and 3). The shim body 34 a is a cylindrical outer wall and is urged in the second direction y by the urging force of the first friction member 11 and the reaction force of the second friction member 12 against the urging force of the first friction member 11. .

  The first, second, third, and fourth support portions 35a, 35b, 35c, and 35d have an angle of 45 degrees (or 135 degrees) with the first direction x in which the driven body is moved from the shim body 34a. ) In a direction protruding in a direction having a), and the fixing member 53 is inserted into a hole included in each of the portions and attached to the fixing base 50. Accordingly, the piezoelectric vibrator 30 including the shim 34 is fixed to the fixed base 50 and does not move. On the other hand, the horizontal movement unit 10 can move in the first direction x by the vibration of the piezoelectric vibrator 30.

  In a state where no voltage is applied to each electrode, the first and second piezoelectric elements 31 and 32 are stationary without causing deformation. When the first AC voltage VE1 is applied to the second and fifth electrodes 31b and 32b, the piezoelectric vibrator 30 moves in the radial direction (the shim main body 34a as the first and second piezoelectric elements 31 and 32 are deformed). Stretching mode vibration (longitudinal vibration such that the center hole 34h of the shim 34 repeats expansion and contraction) that expands and contracts in the radial direction from the center of the upper and lower surfaces to the outer wall is excited. When the second AC voltage VE2 is applied to the first, third, fourth, and sixth electrodes 31a, 31c, 32a, and 32c, the piezoelectric vibrator accompanies the deformation of the first and second piezoelectric elements 31 and 32. 30 is excited in a bending mode vibration that bends and vibrates in the first direction x (a lateral vibration in a driving direction in which the central hole 34h of the shim 34 reciprocates in the first direction x).

  When voltage application to the second and fifth electrodes 31b and 32b is started, the amplitude of the first AC voltage VE1 gradually increases, and the first AC voltage VE1 is taken over a certain time (period from t1 to t3). It becomes a steady state where the amplitude of is constant. Accordingly, when voltage application of the first AC voltage VE1 is started, the amplitude of the expansion / contraction mode vibration of the piezoelectric vibrator 30 gradually increases, and the piezoelectric body takes a certain time (period from t1 to t3). A steady state is obtained in which the amplitude of the expansion / contraction mode vibration of the vibrator 30 is constant (see the upper part of FIG. 5).

  When voltage application to the first, third, fourth, and sixth electrodes 31a, 31c, 32a, and 32c is started, the amplitude of the second AC voltage VE2 gradually increases, and a certain time (from t2 to t4) Over a period of time), a steady state is reached in which the amplitude of the second AC voltage VE2 is constant. Along with this, when voltage application of the second AC voltage VE2 is started, the amplitude of the bending mode vibration of the piezoelectric vibrator 30 gradually increases, and the piezoelectric body takes a certain time (period from t2 to t4). A steady state is obtained in which the amplitude of the bending mode vibration of the vibrator 30 is constant (see the lower part of FIG. 5).

  The portions of the outer wall of the shim body 34a that are in contact with the first and second friction members 11 and 12 due to the bending mode vibration and the expansion and contraction mode vibration (the shim body 34a of the first and second friction members 11 and 12 are The portion that urges the outer wall portion in the second direction y) performs an elliptical motion.

  Due to this elliptical motion, the first and second friction members 11 and 12 that contact the outer wall portion of the shim body 34 a in a state in which the outer wall portion is biased in the second direction y are The horizontal movement unit 10 is moved in the first direction x along with the movement in the first direction x.

  The fixed base 50 includes a fixed base main body 50 a, an engagement member (not shown) that supports the horizontal movement unit 10 slidably in the first direction x, and a fixing member 53 that fixes the piezoelectric vibrator 30. .

  The circuit unit 70 includes a parameter generation unit 71, a comparator 72, a bending mode vibration input unit 73, an expansion / contraction mode vibration input unit 74, and a current monitor 75 (see FIG. 4).

  The parameter generation unit 71 starts excitation of the bending mode vibration (first and third) with respect to the timing of starting the extension mode vibration (starting application of the first AC voltage VE1 to the second and fifth electrodes 31b and 32b). The timing at which the application of the second AC voltage VE2 to the fourth and sixth electrodes 31a, 31c, 32a, and 32c is delayed is output to the comparator 72 using the parameter (first ratio tr1). The first ratio tr1 is the ratio of the amplitude of the first AC voltage VE1 at the bending mode vibration excitation start time (the application start time t2 of the second AC voltage VE1) to the amplitude of the first AC voltage VE1 in the steady state (0 < tr1 <1, length of t1 to t2 / length of t1 to t3).

  At the time point t2, the excitation of the expansion / contraction mode vibration is started from the time point t1, and then the piezoelectric body vibrator 30 urges the shim body 34a in the second direction y by the expansion / contraction mode vibration. The force that pushes back the members 11 and 12 in the second direction y becomes sufficient (the force by which the piezoelectric vibrator 30 pushes the horizontal movement unit 10 in the second direction y is increased by the first and second friction members 11 and 12. It is set at the time when the amplitude of the expansion / contraction mode vibration of the piezoelectric vibrator 30 becomes large enough to exceed the force biased in the two directions y. Therefore, the value of the first ratio tr1 is calculated based on the optimum value of the time point t2 (the length of t1 to t2) obtained through experiments or the like. Generally, tr1 = 0.5 so that a control signal for starting the voltage application of the second AC voltage VE2 is output when the amplitude of the applied first AC voltage VE1 reaches half of the amplitude in the steady state. It is desirable to set to.

  The comparator 72 outputs a value of the second ratio tr2 indicating the ratio between the detected current value output from the current monitor 75 and the current value corresponding to the amplitude in the steady state of the first AC voltage VE1, and the parameter generator 71 outputs the value. The second ratio tr1 is compared with the first ratio tr1 and the second ratio tr2 is equal to or greater than the first ratio tr1 to excite the bending mode vibration to the bending mode vibration input unit 73. A control signal for starting the voltage application of the AC voltage VE2 is output.

  The bending mode vibration input unit 73 is connected to the first, third, fourth, and sixth electrodes 31a, 31c, 32a, and 32c, receives a control signal from the comparator 72, and applies bending mode vibration to these electrodes. The second alternating voltage VE2 to be excited is applied.

  The expansion / contraction mode vibration input unit 74 is connected to the second and fifth electrodes 31b and 32b and applies a first AC voltage VE1 that excites the expansion mode vibration to these electrodes.

  The current monitor 75 detects the amplitude of the first AC voltage VE1 applied from the expansion / contraction mode vibration input unit 74 to the second and fifth electrodes 31b and 32b by replacing it with a current, and the amplitude of the first AC voltage VE1 in a steady state. Is output to the comparator 72 as a second ratio tr2.

  With the configuration of the circuit unit 70 of the present embodiment, after the application of the first AC voltage VE1 that excites the expansion / contraction mode vibration is started, the time is delayed by a time corresponding to the first ratio tr1 (period between the time point t1 and the time point t2). Then, application of the second AC voltage VE2 for exciting the bending mode vibration is started.

  In order to move the driven body (horizontal movement unit 10) in the first direction x, the piezoelectric vibrator 30 is excited with expansion mode vibration and bending mode vibration. After a time point t1 when the stretching mode vibration is excited and before a time point t3 when the stretching mode vibration becomes a steady state (for example, a period from t1 to t2, about 200 ms), the piezoelectric body vibration is caused by the stretching mode vibration. The child 30 does not have enough force to push back the first and second friction members 11 and 12 urging the shim body 34a in the second direction y in the second direction y (the piezoelectric vibrator 30 moves in the horizontal direction). The force pushing the portion 10 in the second direction y is less than the force biased in the second direction y by the first and second friction members 11 and 12).

  Therefore, when the bending mode vibration is excited at the same timing as the stretching mode vibration (see the dotted line in FIG. 5), after the stretching mode vibration is excited (see time t1, FIG. 5), the stretching mode vibration is in a steady state. During a certain period before the time point t3 (e.g., the period from t1 to t2), the first and second friction members 11 and 12 and the shim main body 34a are merely driven to drive in the first direction x. I can't. Therefore, not only power for exciting the bending mode vibration is wasted, but the first and second friction members 11 and 12 and the shim body 34a are worn.

  When the bending mode vibration is started from the time point t3 when the expansion / contraction mode vibration is in a steady state (see the two-dot chain line in FIG. 5), the amplitude of the bending mode vibration causes the horizontal movement unit 10 to move in the first direction x. Is delayed as much as possible (between bending mode vibration start time t3 and time t5 when the steady state is reached). Therefore, the start of movement in the first direction x is delayed, and power for exciting the expansion / contraction mode vibrations up to that point is wasted.

  In the present embodiment, the excitation of the bending mode vibration is started from any time t2 between the time t1 when the stretching mode vibration is excited and the time t3 when the stretching mode vibration is in a steady state. The voltage application timing control is performed. This makes it possible to perform movement control without impairing drive response and without wasting power.

  In addition, the form which moves a to-be-driven body (horizontal direction moving part 10) to the 1st direction x is not restricted to this embodiment, Excitation mode vibration and bending mode vibration are excited to the piezoelectric vibrator 30, and elliptical motion is carried out. Any other form may be used as long as it is performed.

It is a perspective view which shows the structure of the horizontal direction movement part in this embodiment, and a piezoelectric material vibrator. It is a block diagram of a piezoelectric vibrator. It is a block diagram of the cross section in the AA line of FIG. It is a block diagram of a circuit part and an electrode. It is a figure which shows the timing of the alternating voltage application for exciting an expansion-contraction vibration mode, and the alternating voltage application for exciting a bending mode vibration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Horizontal direction moving part 11, 12 1st, 2nd friction member 19 Horizontal direction moving frame 30 Piezoelectric vibrator 31, 32 1st, 2nd piezoelectric element 31a, 31b, 31c 1st, 2nd, 3rd electrode 32a , 32b, 32c 4th, 5th, 6th electrode 34 shim 34a shim body 35a, 35b, 35c, 35d 1st, 2nd, 3rd, 4th support 50 fixed base 50a fixed base main body 53 fixing member 70 Circuit Unit 71 Parameter Generation Unit 72 Comparator 73 Bending Mode Vibration Input Unit 74 Telescopic Mode Vibration Input Unit 75 Current Monitor

Claims (4)

A piezoelectric vibrator;
A circuit unit for applying a first AC voltage for exciting expansion mode vibration and a second AC voltage for exciting bending mode vibration to the piezoelectric vibrator;
The circuit unit is configured to apply the first AC voltage to move the driven body by an elliptical motion based on the expansion mode vibration and the bending mode vibration of the piezoelectric vibrator. The moving apparatus is characterized in that the application of the second AC voltage is started before the AC voltage amplitude reaches a steady state.   The circuit unit includes a detection unit that detects an amplitude of the first AC voltage, and an application control unit that starts application of the second AC voltage when the amplitude is equal to or greater than a predetermined value. The moving device according to claim 1.   The mobile device according to claim 2, wherein the application control unit starts applying the second AC voltage when the amplitude of the first AC voltage becomes half of the amplitude in a steady state. The piezoelectric vibrator is biased by the driven body,
The application start timing of the second AC voltage is such that the piezoelectric vibrator pushes the driven body by the expansion / contraction mode vibration excited by the application of the first AC voltage from the start of application of the first AC voltage. The moving device according to claim 1, wherein a force corresponds to a time until a time when the force exceeds the biased force.

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