JPH0646870B2 - Linear actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a linear actuator adapted to obtain a driving force by vibration of a piezoelectric element and electromagnetic force.

[Outline of Invention]

According to the present invention, at least one electrode is provided on one of the inner peripheral surface and the outer peripheral surface of a cylindrical piezoelectric element, and a plurality of electrodes are provided on the other surface, and a plurality of electrodes are provided on the plurality of electrodes. By applying an AC voltage to the magnet, the magnet is pressed against a part of the outer peripheral surface of the vibrating part that is configured to generate an elastic wave traveling in the circumferential direction, and the coil is placed close to the magnet. Is a linear actuator in which the vibrating portion and the magnet are relatively moved. According to this actuator, high speed feed, fine feed and fixed position control can be easily performed.

[Conventional technology]

By the applicant, Japanese Patent Application Nos. 58-21206 and 5
No. 8-150072 and the like propose an elastic wave motor in which a vibration force of a piezoelectric element is utilized to obtain a rotational force. This acoustic wave motor has a plurality of piezoelectric elements arranged on one surface perpendicular to the axial direction of the ring-shaped elastic body,
A ring-shaped or disk-shaped rotating body is pressed against the opposite surface, the plurality of piezoelectric elements are divided into two groups, and a driving voltage having a phase difference of 90 ° is applied to each group of piezoelectric elements. Thus, an elastic wave traveling in the circumferential direction is generated in the ring-shaped elastic body, and the elastic body is driven to rotate by the elastic wave.

In such an elastic wave motor, a linear actuator is realized by forming the ring-shaped elastic body into an elliptical shape having a straight line portion and pressing the moving body against the straight line portion. Japanese Patent Application No. 60-162275 has been proposed as an elastic wave motor relating to the present invention.

Further, conventionally, a linear actuator such as a plunger solenoid utilizing electromagnetic force has been widely used. Known linear actuators that use this electromagnetic force are those that directly obtain a linear force from the electromagnetic force and those that obtain a linear force through an indirect drive mechanism.

[Problems to be solved by the invention]

The actuator using the elastic wave motor is suitable for performing fine feed at low speed, but high-speed feed is physically limited. Further, there is a drawback that noise is generated and the life is shortened due to the sliding transmission by the pressure contact force.

In the case where the ring-shaped elastic body is formed in an elliptical shape, the curvature greatly changes between the straight line portion and the semicircular portion of the elliptical elastic body, and therefore the shape of the wave generated in both portions is different. Waves are scattered and reflected, and a uniform traveling wave cannot be obtained.

A device that directly obtains a straight driving force from the electromagnetic force has the advantages of being capable of high-speed feed and having a small number of contact parts, but it requires a closed-loop control circuit when performing fixed position control, and during fixed position control. It is necessary to always energize. Further, it is necessary to provide a stopper at the time of stopping, and there is a drawback that the proof stress against disturbance is further low.

The electromagnetic actuator having the above-mentioned indirect drive mechanism has a plurality of mechanisms and becomes large in size, which causes problems such as generation of mechanical noise and accuracy, and difficulty in high-speed feed.

[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 of the cylindrical piezoelectric element. A vibrating section adapted to apply an AC voltage having a phase difference, a magnet that comes into contact with a part of an outer peripheral surface of the vibrating section, a means for press-contacting the vibrating section and the magnet, and a magnet arranged in proximity to the magnet. And a coil.

[Action]

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

〔Example〕

In FIG. 1, a supporting member 1 supports a cylindrical vibrating portion 2 having the structure shown in FIG. 2 with its lower end fixed. A magnet 3 is provided movably in the directions of arrows a and b by contacting a part of the outer peripheral surface of the vibrating portion 2. As the magnet 3, for example, a plate-shaped plastic magnet or the like is used, and both ends thereof are supported by the shaft portions 4 and 5. The guide shaft 6 is attached to the bearings 4 and 5.
When the magnet 3 is inserted, the magnet 3 is movable in the a and b directions, and the magnet 3 and the vibrating portion 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 pressure contact force. This magnet 3 moves N in the above moving direction.
The pole and the S pole are magnetized. Also, the magnet 3 has a substantially L
A shaped arm 7 is fixed, and a magnetic head 8 or the like is attached to the tip of the arm 7.

The coil 9 is arranged close to the surface of the magnet 3 opposite to the surface in contact with the vibrating portion 2. This coil 9
Is linked to the magnetic flux of the magnet 3 by the current supplied from the current-carrying circuit (not shown).
Is arranged at a position where an electromagnetic force in the a direction or the b direction acts on.

As shown in FIG. 2, the vibrating portion 2 has one electrode 11 provided on the outer peripheral surface of a cylindrical piezoelectric element 10 having a length l and four electrodes 12 ₁ to 12 _{1 on} the inner peripheral surface. 12 ₄ in which is made provided.

The cylindrical piezoelectric element 10 used is polarized in a direction from the inner side to the outer side as shown by an arrow c. The electrodes 12 _{1 to} 12 ₄ have a total circumferential length of ₄ of the piezoelectric element 10.
It is arranged to divide equally.

FIG. 3 shows an embodiment of the vibrating circuit of the vibrating section 2.

In the figure, the drive voltage obtained from the AC drive power supply 13 is applied to the electrode 12 ₁ through the amplifier 14, and
After being phase shifted by 90 ° by the 0 ° phase shifter 15, the amplifier 16
It applied to the electrodes 12 ₂ through. After being 180 ° phase shifted by the driving voltage further 180 ° phase shifter 17, together with the applied to the electrodes 12 ₃ via the amplifier 18, 27
After the phase is shifted by 270 ° by the 0 ° phase shifter 19, the amplifier 2
0 is applied to the electrode 12 ₄ through. The electrode 11 is grounded. According to the above, voltages having a phase shift of 90 ° are sequentially applied to the electrodes 12 _{1 to} 12 ₄ . That is, if the voltage applied to the electrode 12 ₁ is cosωt,
The electrodes 12 ₂ , 12 ₃ , and 12 ₄ have sin ωt and −cos ω, respectively.
A voltage of t, −sinωt will be applied.

As a result, the portions 10 ₁ to 10 ₄ of the length λ / 4, which are sandwiched between the electrodes 12 _{1 to} 12 ₄ and the electrode 11, of the piezoelectric element 10 are sequentially shifted by 90 ° in the radial direction. Vibration is generated, and this vibration advances in one direction along the circumferential direction.
That is, a traveling wave of wavelength λ is generated along the circumferential direction of the piezoelectric element 10. In FIG. 1, when the vibration of the traveling wave is transmitted to the magnet 3, the magnet 3 moves together with the arm 7 and the magnetic head 8 in the a direction or the b direction.

Further, by supplying an electric current to the coil 9, the magnet 3 can be moved in the a direction or the b direction.

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 the electrodes 12 _{1 to} 12 of the vibrating section 2.
_{It is} determined by selecting the phase of the current applied to the coil ₄ and the direction of the current flowing through the coil 9.
The moving speed is determined by the frequency of the voltage applied to the vibrating section 2.

When the magnet 3 is stopped, it is stopped by cutting off the power supply to the vibrating portion 2 and the coil 9. At this time, since the vibrating portion 2 is in pressure contact with the magnet 3, it should be stopped with almost no inertia. You can Further, in this stopped state, the position of the magnet 3 is held by friction with the vibrating portion 2. Therefore, there is no need for a fixed position control circuit or mechanical stopper, and there is no need to energize the coil 9.

Moreover, if a voltage of the same phase is applied to each of the electrodes 12 _{1 to} 12 ₄ of the vibrating portion 2, no traveling wave is generated in the vibrating portion 2, and at this time, the vibrating portion 2 simply vibrates, Therefore, the magnet 3 does not move. In this state, when the coil 9 is energized, the magnet 3 is moved by the electromagnetic force, but the vibrating portion 2 is vibrating at this time, so that the friction coefficient for the magnet 3 is small. Therefore, the magnet 3 can be easily moved by the electromagnetic force.

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

In the present embodiment, the polarization direction of the piezoelectric element 10 is the direction from the inside to the outside of the portions 10 ₁ and 10 ₂ as shown by arrows d and e in the figure, and the portions 10 ₃ and 1 are
At 0 ₄ , the direction is from the outside to the inside. At the same time, the drive voltage of the drive power supply 13 is supplied to the amplifiers 14 and 18
In addition to the electrodes ₁₂ 1, 12 ₃ as the through Conomegati, electrodes ₁₂ 2 a voltage of the driving voltage is 90 ° phase-shifted by 90 ° phase shifter 15 as sinωt through amplifiers 16, 20, 1
So that added to the 2 _4.

FIG. 5 shows a third embodiment of the present invention.
Ground electrodes 11 ₁ and two drive electrodes 12 ₁ , 12 ₂
Preparative provided with, and one of the ground electrode 11 ₂ inside 2
The drive electrodes 12 ₃ and 12 ₄ are provided.

In the case of the vibrating section 2, the drive voltage applied to the drive electrodes 12 _{1 to} 12 ₄ is the drive electrodes 12 ₃ , 12 ₁ , 1
2 ₂ and 12 ₄ are conωt, −sinωt, conωt, and −s, respectively.
A voltage of inωt is applied.

In addition to the first to third embodiments described above, the polarization direction of the piezoelectric element 10 and the phase of the voltage applied to the electrodes 12 _{1 to} 12 ₄ can be variously selected. Further, the number of electrodes 12 _{1 to} 12 ₄ is not limited to four, and a minimum of 2 to 2 × n can be used. The drive voltage requires at least two phases.

The piezoelectric element 10 also vibrates in the axial direction (direction of length l in FIG. 2) in addition to the radial direction that contributes to the movement of the magnet 3. In order to prevent the axial vibration from affecting the movement of the magnet 3, the radial vibration frequency may be set lower than the resonance frequency of the axial vibration. For this purpose, the length 1 of the vibrating portion 2 may be selected so as to have a relationship of approximately 1 <λ / 4 with respect to one wavelength λ of the radial vibration.

Position control can also be performed by magnetizing the magnet 3 with a magnetic scale in which N / S magnetic poles are subdivided and by miniaturizing the coil 9 to such a degree that the magnetic scale can be detected.

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

In this embodiment, the moving body 21 is connected to the guide shaft 2
It is provided so as to be movable in the directions of arrows a and b along the lines 2 and 23, and the vibrating portion 2 and the coil 9 are fixedly provided on one side of the moving body 21. At the same time, the magnet 3 is fixedly arranged near the one side of the moving body 21, the outer peripheral surface of the vibrating portion 2 is pressed against the magnet 3, and the coil 9 is close to the magnet 3.

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

〔The invention's effect〕

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

(1) It is not necessary to energize during fixed position control.

(2) Since the position is held by the vibrating portion 2 when stopped (when no power is supplied), it is not necessary to provide a mechanical stopper.

(3) High-speed feed can be performed by the coil 9, in which case mechanical noise is not generated.

(4) The fine feeding can be performed by the vibrating unit 2 using the open loop control circuit.

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

(6) Since the pressure contact force of the vibrating section 2 becomes a viscous load,
Increased resistance to disturbance.

(7) Since the vibrating portion 2 has a cylindrical shape as shown in FIG. 3 and is configured to generate a wave on its outer peripheral surface, the curvature is constant, and scattering or reflection of the wave may occur. Absent. Therefore, a uniform traveling wave can be generated.

(8) The motor structure can be made small and simple.

[Brief description of drawings]

1 is a perspective view showing a first embodiment of the present invention, FIG. 2 is a perspective view of a vibrating portion, FIG. 3 is a drive circuit diagram, and FIG. 4 is a circuit showing a second embodiment of the present invention. FIG. 5 is a side view of the main part showing a third embodiment of the present invention, and FIG. 6 is a perspective view showing the fourth embodiment of the present invention. In the reference numerals used in the drawings, 2 ... Vibrating section 3 ... Magnet 9 ... Coil 10 ... Cylindrical piezoelectric element 11 ... Electrodes 12 _{1 to} 12 ₄ ... Electrodes.

Claims (1)

[Claims] 1. A cylindrical piezoelectric element is provided with at least one electrode on one surface of an inner peripheral surface and an outer peripheral surface and a plurality of electrodes on the other surface, and the plurality of electrodes are provided with predetermined electrodes. A vibrating part that generates an elastic wave traveling in the circumferential direction by applying an AC voltage having a phase difference of, a magnet that contacts a part of the outer peripheral surface of the vibrating part, the vibrating part and the magnet. And a coil arranged in proximity to the magnet, wherein the vibrating portion and the magnet are moved relative to each other.