JPS6277072A - Linear actuator - Google Patents

Abstract

PURPOSE:To feed at high speed and at ultrafine distance with a simple unit by pressure contacting a magnet with which a coil is contacted on a vibrator in which an electrode is provided on one side surface of a cylindrical piezoelectric element and a plurality of electrodes are provided on the other to generate an elastic wave. CONSTITUTION:An electrode 11 is formed on the outer periphery of a cylindrical piezoelectric element 10, and a plurality of electrodes 121-124 are formed on the inner periphery to be polarized from the inside to the outside as designated by an arrow C. When voltage which are phase-shifted at 90 deg. are applied to the electrodes 121-124 to generate radial vibrations having phases displaced at 90 deg. in a portion interposed by the electrodes, the vibration travels along the circumferential direction. A magnet 3 is pressure contacted movably in directions of arrows (a), (b) along a guide shaft 6 supported to both end bearings 4, 5 of the magnet 3 with a vibrator 2. A coil 9 is approached to the magnet 3, and the magnet 3 is stopped or slid in the directions (a), (b) by controlling an exciting current. Thus, a small-sized linear actuator which can be fed at high speed and at ultrafine distance can be simply manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a linear actuator that obtains driving force by vibration of a piezoelectric element and electromagnetic force.

[Summary of the invention]

The present invention provides at least one electrode on one of the inner circumferential surface and outer circumferential surface of a cylindrical piezoelectric element, and a plurality of electrodes on the other surface, and the plurality of electrodes has a plurality of phases. By applying an alternating current voltage to generate an elastic wave traveling in the circumferential direction, a magnet is pressed against a part of the outer peripheral surface of the vibrating part, and a coil is placed close to the magnet. , a linear actuator in which the vibrating section and the magnet move relative to each other. According to this actuator, high-speed feeding, fine feeding, and fixed position control can be easily performed.

[Conventional technology]

By the applicant, Japanese Patent Application No. 58-21206, Japanese Patent Application No. 1983
No. 8-150072, etc., propose an elastic wave motor that uses the vibration of a piezoelectric element to obtain rotational force. This elastic wave motor has a plurality of piezoelectric elements arranged on one surface perpendicular to the axial direction of a ring-shaped elastic body, and
A ring-shaped or disk-shaped rotating body is pressed against the opposite surface, and the plurality of piezoelectric elements are divided into 2Mi, and a driving voltage having a phase difference of 90° is applied to each set of piezoelectric elements. , the ring-shaped elastic body generates elastic waves that travel along the circumferential direction, and the rotating body is rotationally driven by the elastic waves.

In such an elastic wave motor, a linear actuator can be realized by forming the ring-shaped elastic body into an elliptical shape having a straight portion and pressing the moving body against the straight portion. Additionally, Japanese Patent Application No. 162275/1983 has been proposed as an elastic wave motor related to the present invention.

Furthermore, linear actuators such as plunger solenoids that utilize electromagnetic force have been widely used. As linear actuators using this electromagnetic force, there are known ones that obtain linear force directly from electromagnetic force and those that obtain linear force through an indirect drive mechanism.

[Problem that the invention seeks to solve]

The actuator using the above-mentioned elastic wave motor is suitable for fine feeding at low speed, but there is a physical limit to high speed feeding. Furthermore, since the sliding transmission is caused by pressure contact force, noise is generated and the service life is shortened.

In the case where the ring-shaped elastic body is formed into an elliptical shape, the curvature changes widely between the straight part and the semicircular part of the elliptical elastic body, so the form of waves generated in both parts is different. Wave scattering and reflection occur, making it impossible to obtain uniform traveling waves.

Those that obtain linear force directly from the electromagnetic force described above are capable of high-speed feeding and have the advantage of having fewer contact parts, but they require a closed-loop control circuit when performing fixed position control, and when performing fixed position control, It is necessary to always turn on electricity. In addition, it is necessary to provide a stopper for stopping, and there is also the drawback that the resistance against external disturbances is low.

The electromagnetic actuator having the above-mentioned indirect drive mechanism has a complicated and large mechanism, which causes problems such as generation of mechanical noise and accuracy, and also has drawbacks such as difficulty in high-speed feeding.

[Means for solving problems]

In the present invention, at least one electrode is provided on one of the inner peripheral surface and the outer peripheral surface of the cylindrical piezoelectric element, and a plurality of electrodes are provided on the other surface. a vibrating section to which an alternating current voltage having a phase difference is applied; a magnet in contact with a part of the outer peripheral surface of the vibrating section; means for bringing the vibrating section and the magnet into pressure contact; A coil is provided.

[Effect]

The pressure contact between the vibrating part and the magnet enables fine feeding, and the electromagnetic force generated by the magnet and the coil allows high-speed feeding.

〔Example〕

In FIG. 1, a cylindrical vibrating section 2 having the structure shown in FIG. 2 is supported by a support member 1 with its lower end fixed. A magnet 3 is provided so as to be movable in the directions of arrows a and b in contact with a part of the outer circumferential surface of the vibrating section 2. This magnet 3 is made of, for example, plate-shaped plasti, kumaganenoto, etc., and its both ends are connected to bearing portions 4.5.
Supported by By inserting the guide shaft 6 into this bearing portion 4.5, the magnets 3 are
The magnet 7 is configured to be movable in the direction, and the magnet 3 and the vibrating section 2 are in pressure contact with each other. Incidentally, instead of the shaft 6, a guide roller or the like may be used to obtain the pressing force.

This magnet 3 has an N pole and an S pole magnetized in the moving direction. Also, the magnet 3 has an abbreviated arm 7.
is fixed, and a magnetic head 8 or the like is attached to the tip of the arm 7, for example.

A coil 9 is disposed close to the surface of the magnet 3 opposite to the surface that contacts the vibrating section 2 .

This coil 9 is arranged at a position where an electromagnetic force in the a direction or the b direction acts on the magnet 3 due to the interlinkage between the current supplied from a current-carrying circuit (not shown) and the magnetic flux of the magnet 3. has been done.

As shown in FIG. 2, the vibrating section 2 includes one electrode 11 provided on the outer peripheral surface of a piezoelectric element 10 having a cylindrical shape having a length a, and four electrodes 121 to 124 provided on the inner peripheral surface. It is made up of:

The cylindrical piezoelectric element 10 is polarized from the inside to the outside as shown by arrow C. The electrodes 12+ to 124 are arranged so as to divide the entire circumference of the piezoelectric element 10 into four equal parts.

FIG. 3 shows an embodiment of a drive circuit for the vibrating section 2. In FIG.

In the figure, a driving voltage obtained from an AC driving power source 13 is applied to an electrode 121 through an amplifier 14, and
After being shifted by 90° by the 0° phase shifter 15, the amplifier 16
is applied to the electrode 12° through. The driving voltage is further phase-shifted by 180" by a 180° phase shifter 17, and then applied to the electrode 123 through an amplifier 18.
After being phase-shifted by 270° by the 0° phase shifter 19, the amplifier 2
0 to the electrode 124. Further, the electrode 11 is grounded. According to the above, each electrode 12° to 124°
Voltages with a phase shift of 90° are sequentially applied to the .

That is, if the voltage applied to the electrode 121 is CO3ωt, then the voltage applied to the electrodes 12□, 121, ]24 is sin ωt, respectively.
, -CO3ωt, -5in ωt voltages will be applied.

As a result, each electrode 12 . In the portion 10° to 104 of length λ/4 sandwiched between ~124 and the electrode 11, radial vibrations with a phase shift of 90° are generated sequentially, and this vibration is caused along the circumferential direction. Proceed in one direction.

That is, a traveling wave of wavelength λ is generated along the circumferential direction of the piezoelectric element 10. In FIG. 1, the vibration of the traveling wave is transmitted to the magnet 3, so that the magneto 1-3 moves in the a direction or the b direction together with the arm 7 and the magnetic head 8.

Furthermore, by passing a current through the coil 9, the magnet 3 can be moved in the direction a or the direction b.

In this case, the magnet 3 can be finely fed by the driving force of the vibrating section 2, and the magnet 3 can be fed at high speed by the electromagnetic force. The moving direction of the magnet 3 is determined by each electrode 12 . ~12
．． It is determined by selecting the phase of the current applied to the coil 9, and also by the direction of the current flowing through the coil 9.

Further, the moving speed is determined by the frequency of the voltage applied to the vibrating section 2.

When stopping the magnet 3, it is stopped by cutting off the electricity to the vibrating part 2 and the coil 9. At this time, since the vibrating part 2 is in pressure contact with the magnet 3, it can be stopped without generating almost any inertia. I can do it. Further, in this stopped state, the position of the magnet 3 is maintained by friction with the vibrating part 2.

Therefore, there is no need for a fixed position control circuit or a mechanical stopper, and there is no need to energize the coil 9.

Also, each electrode 12 of the vibrating section 2. 124, no traveling wave is generated in the vibrating section 2, and at this time the vibrating section 2 simply vibrates, and therefore the magnet 3 does not move. In this state, when the coil 9 is energized, the magnet 3 moves due to its electromagnetic force, but since the vibrating section 2 is vibrating at this time, the coefficient of friction with respect to the magnet 3 is small. Therefore, the magnet 3 can be easily moved by electromagnetic force.

FIG. 4 shows a second embodiment of the present invention, and parts corresponding to those in FIG. 3 are given the same reference numerals.

In this embodiment, the polarization direction of the piezoelectric element 10 is from the inside to the outside in the portion 101.102, as shown by arrows d and e in the figure, and the polarization direction of the piezoelectric element 10 is from the inside to the outside in the portion 103.1.
04, the direction is from the outside to the inside. At the same time, the drive voltage of the drive power supply 13 is changed to the amplifier 14.18.
In addition to electrodes 12+ and 123 as cos ωt through
The voltage obtained by shifting the phase of the above drive voltage by 90° using a 90° phase shifter 15 is applied to the electrode 1 as sin ωt through an amplifier 16.20.
2□, I am trying to add it to 124.

FIG. 5 shows a Y-th embodiment of the present invention.
grounding electrodes 111 and two driving electrodes 12, . 12□
and one grounding electrode 11□ and 2 inside.
It has a configuration in which drive electrodes 123 and 124 are provided.

In the case of this vibrating section 2, the drive voltages applied to each of the drive electrodes 121-124 are the drive electrodes 121.12, . 12□
, 124 respectively cos ωt, -5inωt, ,c
A voltage of osωt, −5inωt is applied.

In addition to the first to third embodiments described above, there are some differences in the decentralized direction of the piezoelectric element 10 and the electrode 12 . The phase of the voltage applied to 124 can be variously selected. Further, the number of electrodes 12t to 124 is not limited to four, and a minimum of two to 2×n may be used. Further, the driving voltage requires at least two phases.

In addition to the radial vibration that contributes to the movement of the magnet 3, the piezoelectric element 10 also generates axial vibration (in the direction of length l in FIG. 2). This axial vibration causes magnet 3
In order to prevent the vibration from affecting the movement of the radial direction, the frequency of the vibration in the radial direction may be lower than the resonance frequency of the vibration in the axial direction. For this purpose, the length β of the vibrating part 2 is
may be selected so as to have a relationship of approximately β<λ/4 with respect to one wavelength λ of vibration in the radial direction.

Further, position control can also be performed by magnetizing the magnet 3 with a magnetic scale obtained by subdividing the N-3 magnetic poles and reducing the size of the coil 9 to the extent that the magnetic scale can be detected.

FIG. 6 shows a fourth embodiment, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In this embodiment, the movable body 21 is connected to the guide shaft 22.
．． The vibrating section 2 and the coil 9 are fixed to an example part of the movable body 21, and are provided movably in the directions of arrows a and b along the arrow 23. At the same time, a magnet 3 is fixedly arranged adjacent to the negative side of the movable body 21, the outer peripheral surface of the vibrating section 2 is pressed against the magnet 3, and the coil 9 is adjacent to the magnet 3.

According to the above configuration, the movable body 21 can be moved together with the vibrating section 2 and the coil 9 in the a direction or the b direction based on the same principle as shown in FIG. Incidentally, in FIG. 6, it goes without saying that the movable body 21, the vibrating section 2, and the coil 9 may be fixed, and the magnet 3 may be provided movably.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

(1) There is no need to energize during fixed position control.

(2) Since the position is maintained by the vibrating portion 2 when stopped (when no current is applied), there is no need to provide a mechanical stopper.

(3) High-speed feeding can be performed by the coil 9, and no mechanical noise is generated in this case.

(4) Fine feeding can be performed by the vibrating section 2 using an open loop control circuit.

(5) By using the coil 9 and the vibrating part 2 properly, the life of the driving part is extended.

(6), since the pressure contact force by the vibrating part 2 becomes a viscous load,
Increased resistance to external disturbances.

(7) As the vibrating part 2 has a cylindrical shape as shown in Fig. 3 and is configured to generate waves on its outer circumferential surface, the curvature is constant and scattering or reflection of the waves does not occur. do not have. Therefore, uniform traveling waves can be generated.

(8) The structure of the motor can be made compact and economical.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a first embodiment of the present invention, Fig. 2 is a perspective view of a vibrating section, Fig. 3 is a drive circuit diagram, and Fig. 4 is a circuit showing a second embodiment of the invention. FIG. 5 is a side view of essential parts showing a third embodiment of the invention, and FIG. 6 is a perspective view showing a fourth embodiment of the invention. In addition, in the symbols used in the drawings, 2-1-----...----1--Vibration part 3--
−−−−−−−−−−−−−Magnet 9−−−−−−
--- Coil 10----------------- Cylindrical piezoelectric element 11----------------- electrodes 121-12.
-It is an electrode.

Claims (1)

[Claims] At least one electrode is provided on one of the inner peripheral surface and the outer peripheral surface of the cylindrical piezoelectric element, and a plurality of electrodes are provided on the other surface, and the plurality of electrodes are provided with at least one electrode on the other surface. A vibrating part that generates elastic waves traveling in a circumferential direction by applying an alternating current voltage having a predetermined phase difference; a magnet that contacts a part of the outer peripheral surface of the vibrating part; the vibrating part and the magnet; A linear actuator comprising: a means for bringing the vibrator into pressure contact with the magnet; and a coil disposed close to the magnet so that the vibrating part and the magnet move relative to each other.