JP2006246660A - Ultrasonic motor and ultrasonic motor system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relatively move a driven element to an ultrasonic vibrator with high accuracy, while a pressurizing mechanism is simplified and downsized. <P>SOLUTION: An ultrasonic motor 1 includes the ultrasonic vibrator 2 which generates two different oscillation modes simultaneously and generates nearly elliptical oscillation at an output end by supplying a driving voltage, a contact member 10 fixed to the output end of the ultrasonic vibrator 2, the driven element 3 composed of a magnetic material which is pressed by the contact member 10, a magnetic field generating means which is provided at the contact member 10, and generates a magnetic field M which attracts magnetically the driven element 3 toward a side of the contact member 10 to closely contact them, and a magnetic sensor 4 which is fixed to the driven element 3, and detects intensity of the magnetic field M generated by the magnetic field generating means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic motor and an ultrasonic motor system.

In recent years, ultrasonic motors have attracted attention as new motors that replace electromagnetic motors. This ultrasonic motor has the following advantages over conventional electromagnetic motors.
(1) High torque can be obtained without gears.
(2) There is holding power when electricity is OFF.
(3) High resolution.
(4) Rich in silence.

  As a conventional ultrasonic motor, there is one having a structure disclosed in Patent Document 1. In the ultrasonic motor disclosed in Patent Document 1, a magnet is fixed in the vicinity of a piezoelectric vibrator that is in contact with a driven body made of a magnetic material, and piezoelectric is generated by a magnetic attraction generated between the magnet and the driven body. The vibrator is pressed against the driven body, and the pressure mechanism for the driven body of the piezoelectric vibrator is simplified.

On the other hand, since the ultrasonic motor is driven by friction by pressing the ultrasonic vibrator against the driven body, the positional accuracy is greatly influenced by the surface condition of the contact surface between the ultrasonic vibrator and the driven body. The In order to avoid this, it is indispensable to accurately detect the relative position between the ultrasonic transducer and the driven body and to drive and control the ultrasonic transducer. As a method for detecting the relative position between the relative moving stator and the movable element, for example, as shown in Patent Document 2, a magnetic sensor is arranged on either the stator or the movable element and a magnetic scale is arranged on the other The method of doing is mentioned.
JP-A-8-66061 JP-A-11-289743

  However, as disclosed in Patent Document 1, even if the pressure mechanism is simplified and the ultrasonic motor is miniaturized, there is a disadvantage that the driven body cannot be driven accurately unless position detection is performed. Further, when a magnetic scale type relative position detection device as shown in Patent Document 2 is adopted, a magnetic scale having a length longer than the relative movement distance between the ultrasonic transducer and the driven body is moved along the relative movement direction. Therefore, there is a problem that it is difficult to downsize the entire ultrasonic motor system including the ultrasonic motor.

  The present invention has been made in view of the above-described circumstances, and is capable of simplifying and downsizing a pressurizing mechanism and capable of relatively moving a driven body with respect to an ultrasonic transducer with high accuracy. It is an object to provide a motor and an ultrasonic motor system.

In order to achieve the above object, the present invention provides the following means.
According to the present invention, an ultrasonic vibrator that generates two elliptical vibrations at the output end by supplying a driving voltage at the same time to generate a substantially elliptic vibration at the output end, and the ultrasonic vibrator fixed to the output end of the ultrasonic vibrator. A contact member, a driven body made of a magnetic material pressed by the contact member, and a magnetic field that is provided on the contact member and generates a magnetic field that magnetically attracts the driven body to the contact member side to bring them into close contact with each other There is provided an ultrasonic motor comprising a generating means and a magnetic sensor fixed to the driven body and detecting the strength of the magnetic field generated by the magnetic field generating means.

  According to the present invention, by supplying a driving voltage to the ultrasonic transducer, a substantially elliptical motion is generated at the output end, and the driven member is pressed by the contact member fixed to the output end, thereby The ultrasonic transducer and the driven body can be relatively moved by utilizing the change in the frictional force generated in the above. In this case, since the driven member made of a magnetic material is magnetically attracted to the contact member side by the operation of the magnetic field generating means provided on the contact member, the contact member and the driven member of the ultrasonic vibrator are brought into close contact with each other. A large-scale pressurizing mechanism is unnecessary, and downsizing can be achieved.

  Further, since the driven body is provided with a magnetic sensor, when the ultrasonic transducer is displaced relative to the driven body, the magnetic sensor is generated by the magnetic field generating means provided in the contact member. The strength of the magnetic field detected by the above changes according to the relative position between the two. As a result, the relative position of the ultrasonic transducer with respect to the driven body can be accurately detected by the magnetic sensor, and the ultrasonic transducer can be controlled with high accuracy. In this case, since the magnetic field from the magnetic field generating means used for bringing the contact member into close contact with the driven body is used for detecting the relative position, a magnetic scale arranged over the entire length of the moving range becomes unnecessary. The system including the ultrasonic motor can be downsized, the configuration can be simplified, and the cost can be reduced.

In the said invention, it is preferable that the said magnetic field generation | occurrence | production means is comprised by making the said contact member into a magnet.
By comprising in this way, it is not necessary to arrange | position a separate magnet around a contact member, and can achieve further size reduction and weight reduction.

  In addition, the present invention includes any one of the ultrasonic motors described above and a control unit that drives and controls the ultrasonic motor, and the control unit controls the intensity of the magnetic field detected by the magnetic sensor of the ultrasonic motor. There is provided an ultrasonic motor system that calculates a relative position between an ultrasonic transducer and a driven body and adjusts a drive voltage supplied to the ultrasonic transducer based on the calculated relative position.

  According to the present invention, when the relative position between the ultrasonic transducer and the driven body changes due to the operation of the ultrasonic motor, the distance between the magnetic field generating means provided in the ultrasonic motor and the magnetic sensor changes. The magnetic field detected by the magnetic sensor changes. The control unit calculates the relative position between the ultrasonic transducer and the driven body based on the change in the magnetic field detected by the magnetic sensor, and adjusts the driving voltage. Therefore, the relative position between the ultrasonic transducer and the driven body can be controlled with high accuracy. In this case, a magnetic scale that is arranged over the entire length of the moving range becomes unnecessary, and the ultrasonic motor system can be downsized and the cost can be reduced.

  According to the present invention, the pressure mechanism and the position detection mechanism can be simplified and miniaturized, and the driven body can be moved relative to the ultrasonic transducer with high accuracy.

Hereinafter, an ultrasonic motor and an ultrasonic motor system according to a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the ultrasonic motor 1 according to the present embodiment includes an ultrasonic vibrator 2, a driven body 3 driven by the ultrasonic vibrator 2, and the driven body 3 and ultrasonic waves. And a magnetic sensor 4 for detecting a relative position with respect to the vibrator 2. Further, the ultrasonic motor system 5 according to the present embodiment includes a control unit 6 that controls the ultrasonic motor 1 based on the ultrasonic motor 1 and an output voltage or output current from the magnetic sensor 4 of the ultrasonic motor 1. And.

  As shown in FIGS. 2 to 4, for example, the ultrasonic transducer 2 is a rectangular parallelepiped formed by laminating a plurality of sheet-shaped internal electrodes 8 provided on one side of a rectangular plate-shaped piezoelectric ceramic sheet 7. And two frictional contacts (contact members) 10 bonded to two output ends formed on one side surface in the width direction of the piezoelectric laminate 9. .

  The piezoelectric ceramic sheet 7 shown in FIG. 4A includes an internal electrode 8 on almost the entire surface. Two internal electrodes 8 are arranged at a predetermined insulation distance in the length direction of the piezoelectric ceramic sheet 7. Each internal electrode 8 is disposed with a predetermined gap from the periphery of the piezoelectric ceramic sheet 7, and a part thereof extends to the periphery of the piezoelectric ceramic sheet 7.

  The piezoelectric ceramic sheet 7 shown in FIG. 4B includes an internal electrode 8 in substantially half of the width direction. Two internal electrodes 8 are arranged at a predetermined insulation distance in the length direction of the piezoelectric ceramic sheet 7. Each internal electrode 8 is disposed with a predetermined gap from the periphery of the piezoelectric ceramic sheet 7, and a part thereof extends to the periphery of the piezoelectric ceramic sheet 7.

  The piezoelectric ceramic sheet 7 provided with these internal electrodes 8 is formed by laminating a plurality of sheets having a large internal electrode 8 shown in FIG. 4A and a small one having a small internal electrode 8 shown in FIG. As a result, a rectangular parallelepiped piezoelectric laminate 9 is formed.

  A total of four external electrodes 11 are provided, two at each end face in the length direction of the piezoelectric laminate 9. All the internal electrodes 8 arranged at the same position of the same kind of piezoelectric ceramic sheet 7 are connected to each external electrode 11. Thereby, the internal electrodes 8 arranged at the same position of the same kind of piezoelectric ceramic sheet 7 are set to the same potential. Note that a wiring (not shown) is connected to the external electrode 11. The wiring may be any wiring as long as it is flexible, such as a lead wire or a flexible substrate.

Next, the operation of the piezoelectric laminate 9 will be described.
Two external electrodes 11 formed at one end in the longitudinal direction of the piezoelectric laminate 9 are A phase (A +, A−), and two external electrodes 11 formed at the other end are B phase (B +, B−). To do. When an alternating voltage having the same phase and corresponding to the resonance frequency is applied to the A phase and the B phase, the primary longitudinal vibration as shown in FIG. 5 is excited. Further, when an alternating voltage corresponding to the resonance frequency is applied to the A phase and the B phase in opposite phases, a secondary bending vibration as shown in FIG. 6 is excited. 5 and 6 are diagrams showing computer analysis results by the finite element method.

  When primary longitudinal vibration is generated in the piezoelectric laminate 9, the friction vibrator 10 is displaced in the length direction of the piezoelectric laminate 9 (X direction shown in FIG. 5). On the other hand, when secondary bending vibration is generated in the piezoelectric laminate 9, the frictional contact 10 is displaced in the width direction of the piezoelectric laminate 9 (Z direction shown in FIG. 5).

  Therefore, by applying an alternating voltage corresponding to the resonance frequency whose phase is shifted by 90 ° to the A phase and the B phase of the ultrasonic vibrator, the primary longitudinal vibration and the secondary bending vibration are generated simultaneously. As shown by an arrow C in FIG. 2, a substantially elliptic vibration in a clockwise direction or a counterclockwise direction is generated at the position of the friction contact 10.

In the ultrasonic motor 1 according to the present embodiment, the frictional contact 10 bonded to the piezoelectric laminate 9 is constituted by a permanent magnet (magnetic field generating means).
The driven body 3 includes a flat plate-like fixing member 12 and a flat plate-like driving surface member 13 made of a magnetic material fixed to the surface of the fixing member 12.

  The magnetic sensor 4 is fixed to the fixing member 12 and is arranged on the side of the friction contact 10 with a gap. Thereby, the magnetic sensor 4 can detect the strength of the magnetic field M formed by the frictional contact 10 made of a permanent magnet.

  The control unit 6 receives an output signal indicating the strength of the magnetic field M output from the magnetic sensor 4 and calculates a relative position between the driven body 3 and the friction contact 10; A drive control unit 15 that adjusts the drive voltage supplied to the ultrasonic transducer 2 based on the relative position calculated by the position calculation unit 14 is provided.

The operation of the ultrasonic motor 1 and the ultrasonic motor system 5 according to this embodiment configured as described above will be described below.
According to the ultrasonic motor 1 according to the present embodiment, the friction contact 10 bonded to the piezoelectric laminate 9 constituting the ultrasonic vibrator 2 is formed of a permanent magnet, and the fixing member 12 serving as the driven body 3. Since the drive surface member 13 made of a magnetic material is provided on the surface of the ultrasonic transducer 2, the drive surface member 13 is driven by the magnetic contact force of the friction contact 10 in a state where the drive voltage is not supplied. It arrange | positions in the state closely_contact | adhered to.

  In this initial state, the magnetic sensor 4 detects a magnetic field M having a strength corresponding to the positional relationship with the friction contact 10 made of a permanent magnet. Therefore, the position calculation unit 14 calculates and stores the initial relative position between the magnetic sensor 4 and the friction contact 10 based on the output voltage or output current output from the magnetic sensor 4.

  When the target position is set by the control unit 6 in this state, the control unit 6 supplies the ultrasonic vibrator 2 with a driving voltage for moving the ultrasonic vibrator 2 to the target position. When a drive voltage is supplied from the control unit 6, the two frictional contacts 10 bonded to the output end of the piezoelectric laminate 9 are caused to move approximately elliptically. Since the friction contact 10 and the drive surface member 13 are pressed in close contact with each other by the magnetic attraction force of the friction contact 10 made of a permanent magnet, friction generated between the friction contact 10 and the drive surface member 13 is caused when the friction contact 10 is substantially elliptically moved. Due to the force, the driving surface member 13 is pressed by the friction contact 10 in the tangential direction of the substantially elliptical motion.

  By alternately repeating the pressing operation by friction by the two friction contacts 10, the close contact and separation between the friction contact 10 and the drive surface member 13 are intermittently repeated, and the driven body 3 is repeatedly operated. The ultrasonic transducer 2 is moved relatively. In the present embodiment, since the driven body 3 is fixed, the ultrasonic transducer 2 self-travels in one direction with respect to the driven body 3. According to the present embodiment, the friction contact 10 is formed of a permanent magnet, so that it is not necessary to separately provide a pressurizing mechanism for pressing the friction contact 10 against the drive surface member 13, and the number of parts is reduced. Can be simplified, and downsizing and cost reduction can be achieved.

  When the ultrasonic transducer 2 is moved relative to the driven body 3, the relative position of the friction contact 10 with respect to the magnetic sensor 4 is also changed, so that the magnetic field M formed by the friction contact 10 is applied to the magnetic sensor 4. The strength of the magnetic field M detected by the magnetic sensor 4 changes relative to the relative movement. Accordingly, the relationship between the relative positional relationship between the frictional contact 10 and the magnetic sensor 4 and the strength of the detected magnetic field M is measured in advance and stored in the position calculation unit 14 to be detected by the magnetic sensor 4. Based on the strength of the magnetic field M, the relative position of the ultrasonic transducer 2 with respect to the driven body 3 can be calculated with high accuracy.

  According to the present embodiment, the magnetic field M indicating the relative position between the ultrasonic transducer 2 and the driven body 3 is detected by the magnetic sensor 4 using the magnetic field M for bringing the frictional contact 10 into close contact with the driving surface member 13. The strength can be detected with high accuracy, and the relative position can be calculated with high accuracy by the position calculation unit 14. Therefore, it is not necessary to install a magnetic scale having a length equal to or longer than the moving distance, and a small and highly accurate ultrasonic motor 1 and ultrasonic motor system 5 can be realized.

  In the ultrasonic motor 1 according to the present embodiment, the self-propelled ultrasonic motor 1 in which the ultrasonic transducer 2 moves with respect to the fixed driven body 3 is illustrated, but instead, A passive ultrasonic motor 1 that fixes the ultrasonic vibrator 2 and moves the driven body 3 may be employed. In this case, since the magnetic sensor 4 is fixed to the driven body 3, the magnetic sensor 4 is moved together with the driven body 3.

  Next, an ultrasonic motor 20 and an ultrasonic motor system 21 according to a second embodiment of the present invention will be described below with reference to FIGS. In the description of the present embodiment, portions having the same configuration as those of the ultrasonic motor 1 and the ultrasonic motor system 5 according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  The ultrasonic motor 20 according to this embodiment is the same as that of the first embodiment in that a plurality of magnetic sensors 22 and 23 are provided at intervals in the relative movement direction of the ultrasonic transducer 2 and the driven body 3. This is different from the ultrasonic motor 1.

  According to the ultrasonic motor 20 according to the present embodiment, as shown in FIG. 7, when two magnetic sensors 22 and 23 are arranged with respect to the frictional contact 10 of the ultrasonic motor 20, ultrasonic vibration When the child 2 is operated and moved relative to the driven body 3 in one direction, the magnetic field detected by the second magnetic sensor 23 approaching the ultrasonic transducer 2 as shown in FIG. The intensity of M increases with time, but the intensity of the magnetic field M detected by the first magnetic sensor 22 to which the ultrasonic transducer 2 moves away decreases with time.

Therefore, when the relative position between the ultrasonic transducer 2 and the driven body 3 is calculated by the position calculation unit 14, the output voltage value or current value from the two adjacent magnetic sensors 22 and 23 tends to change. By determining, it is possible to prevent the relative positional relationship from being wrong.
In addition, although this embodiment demonstrated the case where it had two magnetic sensors 22 and 23, it may replace with this and three or more magnetic sensors may be arrange | positioned at intervals.

  Further, a hard layer made of a hard material such as zirconia ceramics may be adhered to the surface of the friction contact 10, or zirconia ceramics or the like may be adhered to the surface of the friction contact 10 by a thermal spraying method. .

1 is an overall configuration diagram illustrating an ultrasonic motor and an ultrasonic motor system according to a first embodiment of the present invention. It is a perspective view which shows the ultrasonic transducer | vibrator of the ultrasonic motor of FIG. It is a perspective view which shows the piezoelectric laminated body which comprises the ultrasonic transducer | vibrator of FIG. It is a perspective view which shows the piezoelectric ceramic sheet which comprises the piezoelectric laminated body of FIG. It is a figure which shows a mode that the piezoelectric laminated body of FIG. 2 vibrates in the primary longitudinal vibration mode by computer analysis. It is a figure which shows a mode that the piezoelectric laminated body of FIG. 2 vibrates in a secondary bending vibration mode by computer analysis. 1 is an overall configuration diagram illustrating an ultrasonic motor and an ultrasonic motor system according to a first embodiment of the present invention. It is a graph which shows the relationship between the intensity | strength of the magnetic field detected by two magnetic sensors of the ultrasonic motor of FIG. 7, and the position of an ultrasonic transducer | vibrator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,20 Ultrasonic motor 2 Ultrasonic vibrator 3 Driven body 4,22,23 Magnetic sensor 5,21 Ultrasonic motor system 6 Control part 10 Friction contact (Contact member: Magnetic field generation means)
12 Fixing member (driven body)
13 Driving surface member (driven body)
M magnetic field

Claims (3)

An ultrasonic vibrator that generates a substantially elliptic vibration at the output end by simultaneously generating two different vibration modes by being supplied with a driving voltage;
A contact member fixed to the output end of the ultrasonic transducer;
A driven body made of a magnetic material pressed by the contact member;
A magnetic field generating means for generating a magnetic field that is provided on the contact member and magnetically attracts the driven body toward the contact member to bring them into close contact;
An ultrasonic motor comprising: a magnetic sensor that is fixed to the driven body and detects the strength of a magnetic field generated by the magnetic field generating means.   The ultrasonic motor according to claim 1, wherein the magnetic field generation unit is configured by using the contact member as a magnet. The ultrasonic motor according to claim 1 or 2,
A control unit for driving and controlling the ultrasonic motor,
The control unit calculates a relative position between the ultrasonic transducer and the driven body based on the strength of the magnetic field detected by the magnetic sensor of the ultrasonic motor, and the ultrasonic wave based on the calculated relative position. An ultrasonic motor system that adjusts the drive voltage supplied to the transducer.

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