JPH06261559A - Rotary actuator - Google Patents

Abstract

PURPOSE:To obtain an actuator wherein its size is small and its transmission efficiency is good without being subjected to a restriction on an electricity-feeding means by a method wherein a driving electric signal whose waveform has a gentle rise part and a quick fall part is supplied to an electromechanical conversion element. CONSTITUTION:In an actuator, a piezoelectric element 15 is arranged, bonded and fixed between a face 1b on a receiver part 1a for a fixation member 1 and a face 5b on a cutout part 5a. When sawtooth waves are applied to electrodes for the piezoelectric element 15, the thickness of the piezoelectric element 15 is expanded by a voltage which is increased gently. Then, a movable member 5 is turned by a definite angle with reference to the fixation member 1. Also a rotor 7 is turned by a definite angle together with the movable member, and a gear part at the outer circumference turns and drives a motive-power transmission mechanism. When the sawtooth waves reach the peal of their rise part, a voltage which is reduced suddenly is applied to the electrodes for the piezoelectric element 15, and the thickness of the piezoelectric element 15 is shrunk rapidly. As a result, the movable member 5 is returned. However, since its movement is larger than the frictional coupling between the rotor 7 and the movable member 5, the rotor 7 remains at its position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary actuator using a piezoelectric element, a magnetostrictive element or the like.

[0002]

2. Description of the Related Art In cameras and copying machines, many motors are used to drive various internal mechanisms. For example, in a camera, a motor is incorporated in each of a film winding mechanism, a focus adjusting mechanism of a photographing lens, and the like, and the motor is driven according to a predetermined control command. Motors that drive such various mechanisms are often used at a reduced rotational speed by using a gear reduction mechanism or the like in order to obtain a desired torque or a desired driving speed. The drive mechanism has the advantage of being simple in structure, but on the other hand, it has the drawback of not only making the device bulky, but also of poor transmission efficiency.

Therefore, a power source using a piezoelectric element or the like has been proposed. That is, by utilizing the phenomenon that distortion in the length direction occurs when a voltage is applied to the piezoelectric element, an impact voltage is applied to the piezoelectric element fixed to the inertial body to apply an impact force to the inertial body,
The motion of the inertial body due to the impact force is used to drive the driven body (Japanese Patent Laid-Open No. 63-1107).
4 and JP-A-63-299785).

[0004]

The power source using the above-mentioned piezoelectric element is small in size and improved in transmission efficiency as compared with the conventional drive mechanism using the motor and the gear reduction mechanism, but it is still movable. There has been a demand for the development of a better configuration that can easily control the amount, rotation angle, moving direction, and the like, and is not restricted by the means for feeding the piezoelectric element due to the movement of the inertial body. The present invention is intended to solve the above problems.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and a fixing member having a rotating shaft, a rotating member rotatably disposed on the rotating shaft, and the fixing member. An electro-mechanical conversion element arranged between a fixed member and a rotating member so as to displace the rotating member in a rotation direction, and a drive element rotatably arranged on the rotating shaft and frictionally coupled to the rotating member. The drive element is driven by supplying a drive electric signal having a waveform having a gentle rising portion and a rapid falling portion to the electro-mechanical conversion element.

[0006]

When a drive signal having a gentle rising portion is supplied to an electro-mechanical conversion element such as a piezoelectric element or a magnetostrictive element, extensional displacement occurs and the rotary member is displaced in the rotational direction with respect to the fixed member. As a result, the drive element frictionally coupled to the rotary member is rotated and driven together with the rotary member. When a return signal having a rapid falling portion is supplied to the electro-mechanical conversion element, a rapid contraction displacement is caused, and the rotating member is rapidly displaced in the opposite direction to the fixed member. The drive element which is frictionally coupled remains in its position. The drive element can be driven at a desired speed by adjusting the waveform of the drive electric signal supplied to the electro-mechanical conversion element.

[0007]

Embodiments of the present invention will be described below.
FIG. 1 is a perspective view showing the outer appearance of a rotary actuator embodying the present invention, FIG. 2 is a cross-sectional view with a part of its side cut away, and FIG. 3 is a plan view taken along the line AA of FIG. is there.

First, the overall structure will be described. 1 and 2, reference numeral 1 is a fixing member, and 2 is a shaft provided on the fixing member 1. On the shaft 2, a first thrust bearing 4, a movable member 5, a friction disk 6, a rotor 7, which is a drive element for extracting a driving force, a second thrust bearing 8, and a spring 9 are sequentially arranged from the fixed member 1 side. ing. The rotor 7 is a gear having a tooth profile formed on the outer circumference thereof, and is configured to be coupled to a power transmission mechanism (not shown) or the like to take out a driving force.

A threaded portion 11 is formed at the end of the shaft 2, and a nut 10 is screwed into the threaded portion 11.
By tightening the nut 10, the compression force of the spring 9 can be adjusted to adjust the frictional coupling force between the movable member 5, the friction disk 6, and the rotor 7.

The arrangement of the piezoelectric elements will be described. As can be seen with reference to FIGS. 1 to 3, and in particular to FIG.
Is provided with a receiving portion 1a protruding in a direction parallel to the axis 2 and having a surface 1b in a substantially normal direction, and the movable member 5 is provided in a portion corresponding to the receiving portion 1a in a substantially normal direction. Surface 5b
Is provided with a notch portion 5a. Then, the surface 1b of the receiving portion 1a and the surface 5 of the cutout portion 5a.
The piezoelectric element 15 is disposed between the piezoelectric element 15 and the element b, and the upper and lower end portions of the piezoelectric element 15 are fixed to the surface 5b and the surface 1b, respectively, by adhesion.

As the piezoelectric element 15, a piezoelectric element which is displaced in the thickness direction when a voltage is applied to the electrodes at both ends thereof is used.

Next, the operation will be described. A sawtooth wave (see FIG. 5) having a desired frequency and amplitude is supplied to the piezoelectric element 15 from a sawtooth wave oscillator (not shown).

First, in a state where the sawtooth wave is not applied to the electrodes of the piezoelectric element 15, the fixed member 1 and the movable member 5 are assumed to be in the positions shown in FIG.

When a sawtooth wave is applied to the electrodes of the piezoelectric element 15, first, the thickness of the piezoelectric element 15 is extended by the gently increasing voltage shown at the rising portion of the sawtooth wave. Then, the gap between the surface 1b of the receiving portion 1a of the fixed member 1 and the surface 5b of the cutout portion 5a of the movable member 5 is opened, and the movable member 5 rotates with respect to the fixed member 1 by a certain angle. The rotor 7, which is in pressure contact with the movable member 5 via the friction disk 6, also rotates with the movable member 5 by a certain angle, and the gear portion on the outer periphery thereof rotationally drives the power transmission mechanism (not shown). 4 is a cutaway plan view of the same portion as FIG. 3, but shows the positions of the fixed member 1 and the movable member 5 in a state where the thickness of the piezoelectric element 15 is expanded.

When the waveform of the sawtooth wave reaches the peak of the rising portion, a sharply decreasing voltage indicated by the falling portion of the sawtooth wave is applied to the electrodes of the piezoelectric element 15, and the piezoelectric element 15 rapidly changes its voltage. The thickness shrinks. As a result, the movable member 5 returns to the position shown in FIG. 3, but at this time, the movement of the movable member 5 in the opposite direction due to the rapid contraction of the piezoelectric element 15 causes frictional coupling between the rotor 7 and the movable member 5. Since it is larger than the above, the rotor 7 stays in that position in spite of the reverse movement of the movable member 5.

The above operation is performed by the rotor 7 and the movable member 5.
Since it depends on the frictional coupling force between and, the compression force of the spring 9 by the nut 10 on the shaft 2 is adjusted in advance so that an appropriate frictional coupling force can be obtained.

When the sawtooth wave is continuously applied to the electrodes of the piezoelectric element 15, the movable member 5 and the rotor 7 repeat the above operation, and the movable member 5 repeats reciprocating rotation within a certain angle range, but the rotor 7 does not rotate. It is rotationally driven intermittently in a fixed direction.

Further, by appropriately setting the mass of the rotor 7, the torque of the power transmission mechanism, or the friction coupling force, it is possible to continuously drive by utilizing the inertia.

FIG. 5 shows the relationship between the waveform V of the sawtooth wave applied to the electrodes of the piezoelectric element 15 and the displacement amount δ of the piezoelectric element 15 generated. The waveform of the sawtooth wave is a waveform of rapidly falling after reaching the peak of the rising portion, whereas the displacement amount of the piezoelectric element 15 is gradually extended after gradually expanding.
It shows the displacement in the shrinking direction with a time delay from the falling waveform of the sawtooth wave. This is due to the characteristics of the piezoelectric element.

By changing the frequency of the sawtooth wave applied to the electrodes of the piezoelectric element 15, the number of times the rotor 7 is driven per unit time, that is, the number of rotations can be changed. Further, by changing the amplitude of the sawtooth wave,
It is possible to change the drive amount per pulse, and thus it is possible to change the rotational speed and the accuracy of the rotation stop position.

The rotating direction of the rotor 7 can be reversed by changing the polarity of the sawtooth wave applied to the electrodes of the piezoelectric element 15.

The piezoelectric element 15 is attached to the fixed member 1 and the movable member 5 which reciprocally rotates within a fixed angle range, and does not rotate about the shaft 2 many times. The wiring can be done very easily.

In the above embodiment, the drive source electricity is
Although the piezoelectric element is used as the mechanical conversion element, other electro-mechanical conversion elements, such as a magnetostrictive element, are also used.
It can be configured in exactly the same way.

[0024]

As described above, according to the present invention, the amount of movement, the rotation angle, the rotation direction, etc. can be adjusted by simply adjusting the frequency, amplitude and polarity of the electric signal supplied to the electromechanical conversion element of the drive source. It is possible to provide a small-sized actuator with high transmission efficiency without being restricted by the power supply means for the electro-mechanical conversion element.

[Brief description of drawings]

FIG. 1 is a perspective view showing the outer appearance of a rotary actuator of the present invention.

FIG. 2 is a side sectional view of the rotary actuator.

FIG. 3 is a rotary actuator AA shown in FIG.
FIG.

FIG. 4 is an operation explanatory view showing a position where a movable member of the rotary actuator is operated.

FIG. 5 is a diagram showing a relationship between a sawtooth wave waveform applied to a piezoelectric element and a piezoelectric element displacement amount.

[Explanation of symbols]

 1 Fixed member 2 Shaft 4 1st thrust bearing 5 Movable member 6 Friction disk 7 Rotor 8 2nd thrust bearing 9 Spring 10 Nut 15 Piezoelectric element

Claims (3)

[Claims] 1. A fixing member having a rotating shaft, a rotating member rotatably disposed on the rotating shaft, and a fixing member rotating so as to displace the rotating member in a rotation direction with respect to the fixing member. The electro-mechanical conversion element is disposed between the electro-mechanical conversion element and the member, and a drive element that is rotatably arranged on the rotation shaft and frictionally coupled to the rotation member. A rotary actuator characterized in that it drives a drive element by supplying a drive electric signal having a waveform having a rising portion and a rapid falling portion. 2. The rotary actuator according to claim 1, wherein the electro-mechanical conversion element is a piezoelectric element. 3. The rotary actuator according to claim 1, wherein the electromechanical conversion element is a magnetostrictive element.