JP2002101675A - Actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drive efficiency in an actuator wherein a drive member is elliptically moved as a displacement element such as a piezoelectric element is made a drive source, pressurized and brought into contact on the driven member, which is driven by friction. SOLUTION: Two chip members (drive member) 20A, 20B provided on each intersection point of two sets of piezoelectric elements (displacement element) 10A and 10B, 10C and 10D are driven so that the phase of elliptical movement is inverted respectively, and each chip member 20A and 20B are alternately in contact on a rotor (driven member) 40 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for driving a driven member by using a plurality of driving members in an actuator using a displacement element such as a piezoelectric element, thereby improving driving efficiency.

[0002]

2. Description of the Related Art Conventionally, as an actuator using a displacement element such as a piezoelectric element, a displacement element is disposed at one end of a rod-shaped vibrating body, and a tip member disposed at the other end is subjected to simple vibration, and the tip member is attached to a rotor. 2. Description of the Related Art A wedge-shaped actuator is known in which a tip member is brought into contact with pressure obliquely to convert a movement of a tip member into an elliptical motion to rotate a rotor. Alternatively, an annular ultrasonic motor that transmits a driving force by disposing a displacement element on the surface of a thin annular vibrator to generate a traveling wave and pressurize and contact the rotor with a rotor is also known.

Further, two displacement elements such as piezoelectric elements are arranged so that their displacement directions form a predetermined angle (for example, 90 degrees), and a chip member provided at the intersection of each displacement element has an elliptical or circular orbit. A truss-type actuator has been proposed in which each displacement element is driven by an AC voltage signal having a predetermined phase difference so that the tip member contacts the rotor and the rotor rotates in a predetermined direction.

[0004]

In the case of a wedge-shaped actuator, since the tip member reciprocates linearly, the tip member and the rotor are kept in contact with the rotor even during the deceleration period (period when the tip member is about to return) regardless of the magnitude of the pressing force. Contact and low drive efficiency. Further, since the angle at which the tip member contacts the rotor is large, vibration and noise are generated. Furthermore, the wear of the tip member and the rotor shortens the life of the actuator.

On the other hand, in the case of an annular ultrasonic motor, the number of contact points between the displacement element and the rotor is equal to the number of traveling waves.
Even when the pressing force is increased, there is little possibility that the displacement element and the rotor come into contact in the deceleration area (the area where the deformation of the displacement element is about to return to the original state). However, since the displacement direction of the displacement element coincides with the direction of the pressing force, when the pressing force is increased, the displacement itself of the displacement element is suppressed, and the output decreases. In addition, an annular vibrator is required to feed back the traveling wave, which greatly restricts the structure.

In the case of a truss-type actuator, since the driving force is transmitted by friction between the tip member and the rotor, it is necessary to increase the pressing force to increase the driving force. However, in the conventional truss-type actuator, since the tip member is single, when the pressing force is increased, the contact portion between the tip member and the rotor is elastically deformed, and the contact time between the two increases. When the contact time between the tip member and the rotor is shortened, both contact only in the acceleration region,
Although the transmission efficiency of the driving force increases, the driving force itself decreases. Conversely, if the contact time between the tip member and the rotor is increased, the two contact each other even in the deceleration region, and the driving force itself increases, but the transmission efficiency of the driving force decreases.

The present invention has been made to solve the above-mentioned problems of the conventional example, and has as its object to provide an actuator having high driving efficiency.

[0008]

In order to achieve the above object, an actuator according to the present invention includes a plurality of displacement elements for generating a predetermined displacement, and each of the plurality of displacement elements is coupled to each of the displacement elements. A plurality of driven members to be driven, a driven member driven by the contact of the driving member, a pressing member for pressing the driving member against the driven member, and different timings of the driving member And a drive circuit for applying a drive signal to each of the displacement elements so as to contact the driven member.

In the above configuration, it is preferable that each of the driving members is provided at an intersection of a plurality of displacement elements disposed so as to form a predetermined angle with each other.

It is preferable that each of the driving members is arranged in parallel with the driven member in a predetermined direction.

Further, the driven member is a rotating body,
It is preferable that each of the driving members is arranged parallel to a rotation axis of the driven member.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described by taking a truss type actuator as an example. FIG. 1 is a diagram illustrating a configuration of a truss-type actuator according to the present embodiment.

As shown in FIG. 1, a plurality of (two in this embodiment) drive units 1A and 1B are arranged in parallel in a direction parallel to a rotation axis L of a rotor 40 as a driven member. It should be noted that the two drive units 1A and 1B are slightly shifted for easy understanding. The one drawn in the upper part of the figure is the first drive unit 1A, and the one drawn in the lower part is the second drive unit 1B.

The first drive unit 1A includes two laminated first and second piezoelectric elements 10A and 10B arranged at a predetermined angle (eg, 90 degrees) to each other.
A first chip member (driving member) joined to an intersecting end of the piezoelectric element 10A and the second piezoelectric element 10B by an adhesive or the like.
20A, the first piezoelectric element 10A and the second piezoelectric element 10B
Of the first piezoelectric element 1 is fixed by an adhesive or the like.
0A and a first base member 30A that holds the second piezoelectric element 10B, and a first pressing member (such as a coil spring or a leaf spring) that generates a pressing force for bringing the first chip member 20A into contact with the surface of the rotor 40. (Elastic body) 45A and a first pressing force adjusting mechanism 46A for adjusting the pressing force by the first pressing member 45A.

The second drive unit 1B has substantially the same configuration as the first drive unit 1A.
Two stacked third and fourth piezoelectric elements 10C and 10D arranged at a predetermined angle to each other, and a second bonded to the cross-side end of the third and fourth piezoelectric elements 10C and 10D. A chip member (drive member) 20B, a second base member 30B to which the base ends of the third piezoelectric element 10A and the fourth piezoelectric element 10B are fixed, and which hold the third piezoelectric element 10C and the fourth piezoelectric element 10D; A second pressing member 45B for generating a pressing force for bringing the two-chip member 20B into contact with the surface of the rotor 40, a second pressing force adjusting mechanism 46B for adjusting the pressing force by the second pressing member 45B, and the like. It is composed of

First to fourth piezoelectric elements 10A, 10B, 10C
2 and 10D are shown in FIG. Each piezoelectric element 10A-1
OD indicates a plurality of ceramic thin plates 11 and electrodes 12 each exhibiting piezoelectric characteristics such as PZT (lead zirconate titanate).
13 are alternately laminated, and each ceramic thin plate 1
1 and the electrodes 12 and 13 are fixed by an adhesive or the like. The alternate electrode groups 12 and 13 arranged alternately are connected to a driving power supply 16 via signal lines 14 and 15, respectively. When a predetermined voltage is applied between the signal lines 14 and 15, each ceramic thin plate 11 sandwiched between the electrodes 12 and 13 is applied.
, An electric field is generated in the stacking direction, and every other electric field is in the same direction. Therefore, each ceramic thin plate 11
Are stacked so that the polarization direction is the same for every other (the polarization directions of two adjacent ceramic thin plates 11 are opposite). Note that protective layers 17 are provided on both ends of each of the piezoelectric elements 10A to 10D.

When a DC drive voltage is applied between the electrodes 12 and 13 by the drive power supply 16, all the ceramic thin plates 11 expand or contract in the same direction, and the piezoelectric elements 10A to 10A
D expands and contracts as a whole. In a region where the electric field is small and the displacement history is negligible, the electric field generated between the electrodes 12 and 13 and the displacement of each of the piezoelectric elements 10A to 10D can be regarded as a substantially linear relationship.

On the other hand, when an AC drive voltage (AC signal) is applied between the electrodes 12 and 13 by the drive power supply 16, the ceramic thin plates 11 repeatedly expand and contract in the same direction according to the electric field, and the piezoelectric elements 10A 10D repeats expansion and contraction as a whole. Each of the piezoelectric elements 10A to 10D has a unique resonance frequency determined by its structure and electrical characteristics. When the frequency of the AC drive voltage is equal to each of the piezoelectric elements 10A-1A
When the resonance frequency matches the resonance frequency of 0D, the impedance decreases and the displacement of each of the piezoelectric elements 10A to 10D increases. Since each of the piezoelectric elements 10A to 10D has a small displacement with respect to its external dimensions, it is desirable to utilize this resonance phenomenon in order to drive at a low voltage.

As a material of each of the tip members 20A and 20B, tungsten or the like which can stably obtain a high friction coefficient and is excellent in wear resistance is preferable. Each base member 30A
And 30B are preferably stainless steel or the like which is easy to manufacture and has excellent strength. Further, as the adhesive, an epoxy resin or the like having excellent adhesive strength and strength is preferable.

First piezoelectric element 10A and second piezoelectric element 10
By driving B or the third piezoelectric element 10C and the fourth piezoelectric element 10D with AC signals having a phase difference,
The first tip member 20A or the second tip member 20B can be driven to draw an elliptical orbit. These tip members 20A and 20B are connected to a predetermined axis L, for example.
When pressed against the cylindrical surface of the rotor 40 rotatable around the rotor, the elliptical or circular motion of the tip members 20A and 20B can be converted into the rotational motion of the rotor 40.
Alternatively, the elliptical motion or the circular motion of the tip members 20A and 20B can be converted into the linear motion of the bar members by pressing the tip members 20A and 20B against, for example, a flat portion of a bar member (not shown). . Rotor 4
As a material of No. 0, a lightweight metal such as aluminum is preferable, and it is preferable to apply a treatment such as alumite to the surface in order to prevent abrasion due to friction with the chip members 20A and 20B.

Next, FIG. 3 shows a block configuration of a drive circuit according to the present embodiment. The oscillator 50 generates (oscillates) a first sine wave signal (basic signal) at a resonance frequency that matches in the in-phase mode and the anti-phase mode, as described later as an example. The first phase control unit 51A controls the first delay circuit 52A according to the rotation speed, drive torque, rotation direction, and the like of the rotor 40, which is a driven member, and the phase is shifted from the first sine wave signal. Generate a second sine wave signal. The first amplitude control unit 53A includes a first amplifier 54A and a second amplifier 54A.
B is controlled to amplify the amplitudes of the first sine wave signal and the second sine wave signal that are out of phase with each other. The first sine wave signal and the second sine wave signal (drive signal) amplified by the first amplifier 54A and the second amplifier 54B are respectively connected to the first piezoelectric element 10A and the second piezoelectric element 10B constituting the first drive unit 1A. Is applied to

The second phase control section 51B includes a second delay circuit 5
2B and the third delay circuit 52C are controlled to generate a third sine wave signal out of phase with respect to the first sine wave signal and a fourth sine wave signal further out of phase with respect to the third sine wave signal. I do. The second amplitude control unit 53B controls the third amplifier 54C and the fourth amplifier 54D, and controls the third and
The amplitudes of the sine wave signal and the fourth sine wave signal are amplified. Third
The third sine wave signal and the fourth sine wave signal (drive signal) amplified by the amplifier 54C and the fourth amplifier 54D are applied to the third piezoelectric element 10C and the fourth piezoelectric element 10D, respectively.

First piezoelectric element 10A and second piezoelectric element 10
When drive signals having different phases are respectively applied to B or the third piezoelectric element 10C and the fourth piezoelectric element 10D, the first piezoelectric element 10A and the second piezoelectric element 10B or the third piezoelectric element 10C and the fourth piezoelectric element Element 10D is displaced sinusoidally. First piezoelectric element 10A and second piezoelectric element 1
0B or two independent orthogonal motions by the third piezoelectric element 10C and the fourth piezoelectric element 10D are combined,
The intersection points draw an ellipse (including a circle) trajectory according to the elliptical vibration equation (Lissajous equation).

First piezoelectric element 10A and second piezoelectric element 10
If the frequency of the drive signal applied to B or the third piezoelectric element 10C and the fourth piezoelectric element 10D is sufficiently small, the first chip member 20A or the second chip member 20B draws an elliptical locus according to the equation of elliptical vibration. However, the first piezoelectric element 10
In order to enlarge the displacement of the first and second piezoelectric elements 10B or 10C and the fourth piezoelectric element 10D, the frequency of the drive signal is increased to approach the resonance frequency. The trajectory of the member 20B is shifted from the desired shape.

An actual drive unit (for example, a first drive unit 1A) is actually manufactured, and the first piezoelectric element 10A and the second piezoelectric element 10B are moved near their resonance frequencies so that the chip member 20A draws a circular locus. When driven by a drive signal having a frequency of
A phenomenon occurred in which the locus of 0A was deformed into an elliptical shape greatly inclined from the central axis. In the course of the experiment, it was found that this phenomenon occurs when the vibrations of the piezoelectric elements 10A and 10B mutually affect via the chip member 20A and the base member 30A. One piezoelectric element (for example, 10
The vibration of A) has a phase delay of about 90 ° and the other piezoelectric element 10
B, the displacement of the piezoelectric element 10B that is displaced later overlaps with the drive signal and expands, and the displacement of the piezoelectric element 10A that displaces first is reduced. As a result, the tip member 20A
Is an elliptical shape extending in the displacement direction of the piezoelectric element 10B that is displaced later.

In order to solve this phenomenon, transmission of vibration of one piezoelectric element to the other piezoelectric element is suppressed as much as possible.
It is necessary to realize a system in which the two piezoelectric elements 10A and 10B can be independently displaced. By realizing such a system, the trajectory of the chip member 20A or 20B can be made to have a desired elliptical shape (including a circular shape) in all frequency bands including the resonance frequency. Also, by changing the amplitude and phase difference of the drive signal as needed,
The shape of the trajectory of the tip member 20A can be arbitrarily changed, and the speed of the driven member such as the rotor 40 can be controlled.

The present inventors have stated that "the natural frequencies of the elongational vibration in the in-phase mode and the elongational vibration in the opposite-phase mode are the same" for the two piezoelectric elements 10A and 10B or 1
It has been found that 0C and 10D are conditions for realizing a system that can be independently displaced (for details, see Japanese Patent Application No. 11-166919 by the present applicant).
In order to make the natural frequencies of the elongation vibration in the in-phase mode and the elongation vibration in the anti-phase mode coincide, for example, the mass of the tip members 20A and 20B may be adjusted. here,
The in-phase mode is a mode in which the phases of the displacements of the two piezoelectric elements 10A and 10B or 10C and 10D match, and the anti-phase mode is a mode in which the phases of the displacements of the two piezoelectric elements 10A and 10B or 10C and 10D are reversed. Is defined.

First piezoelectric element 10A and second piezoelectric element 10
FIG. 4 shows the eigenmode of the actuator when B or the third piezoelectric element 10C and the fourth piezoelectric element 10D undergo elongation vibration. In FIG. 4, (a) shows the case of the in-phase mode,
(B) shows the case of the anti-phase mode.

In the case of the in-phase mode, the tip member 20A or 20B vibrates in the direction of the axis of symmetry (the direction of arrow X) of each drive unit 1A or 1B. In the case of the reverse phase mode, the chip member 20A or 20B is connected to each drive unit 1A.
Or it vibrates in the direction (arrow Y direction) orthogonal to the symmetric axis direction of 1B. In the in-phase mode and the anti-phase mode, when the frequency of the drive signal is close to the natural frequency, it approximates the vibration mode as shown in FIG. 4 regardless of the amplitude and phase of the drive signal.

On the other hand, the tip member 20 is actively used to transmit the vibration of the one piezoelectric element to the other piezoelectric element.
The trajectories of A and 20B can be formed in a desired shape. For example, by setting the ratio between the natural frequency in the in-phase mode and the natural frequency in the anti-phase mode to a predetermined value, the trajectories of the chip members 20A and 20B are made elliptical just by driving one of the piezoelectric elements. (For details, refer to Japanese Patent Application No. 2000-150180 filed by the present applicant.)
No.). This is because a predetermined phase difference occurs between the vibrations of the in-phase mode and the anti-phase mode excited by the vibration of the piezoelectric element. In this case, the ratio of the natural frequencies can also be adjusted by adjusting the mass of the tip members 20A and 20B.

As described above, the trajectories of the chip members 20A and 20B can be set by matching the natural frequencies of the plurality of drive units constituting the actuator in the in-phase mode and the anti-phase mode or by setting them at a predetermined ratio. The desired shape can be obtained. The piezoelectric element 1
When 0A to 10D are used in a non-resonant state, a high drive voltage is required, but such adjustment of the natural frequency is not necessary. The actuator of the present invention can be applied in any of a resonance state and a non-resonance state.

Next, the pressing force that can maximize the output of the actuator of the present embodiment will be discussed. When the rotor 40 is rotationally driven by one drive unit 1A or 1B,
According to experiments by the present inventors, with an increase in pressure,
The contact ratio between the tip member 20A or 20B and the rotor 40 (the time during which the tip member 20A or 20B is in contact with the rotor 40 during one rotation of the elliptical motion) increases, and the two members intermittently contact each other ( (Disconnected state) to a state of constant contact (constant contact state). The output of the actuator becomes maximum near the transition from the detached state to the normal state (the pressing force at this time is assumed to be N ₀ ). Assuming that the electrical input to the actuator is constant, the condition for obtaining the maximum output of the actuator matches the condition for maximizing the driving efficiency (for details, refer to the specification of Japanese Patent Application No. 11-321965 by the present inventors). .

However, under the condition that the maximum output of the actuator can be obtained, the rotor 40 receives both the acceleration force and the deceleration force from the tip member 20A or 20B, and thus is not necessarily an ideal condition. When the rotor 40 contacts the tip member 20A or 20B during deceleration, the rotor 40
And the tip member 20A or 20B are moved in the opposite direction, the output of the actuator is reduced, and damage due to wear of the rotor 40 and the tip member 20A or 20B is increased.

In the above experiment, the output is larger in the normal state than in the separated state. The reason is that the increase in the frictional force due to the increase in the pressing force is greater than the decrease in the output due to the contact between the rotor 40 and the tip member 20A or 20B during deceleration. If the pressure is further increased than N ₀ in the normal state, the increase in the frictional force is canceled between acceleration and deceleration, and the output of the actuator does not further increase. Rather, the output of the actuator gradually decreases due to an increase in frictional resistance of the bearing portion due to an increase in the pressing force.

With respect to such a phenomenon, in the actuator of the present embodiment, a plurality of drive units (for example, two sets) are provided.
The two tip members 20A and 20B are driven so as to contact the rotor 40 at different timings.

The first tip member 20A in the present embodiment
And the displacement of the second tip member 20B and these and the rotor 40
FIG. 5 shows the relationship between the contact states. In the lower graph of FIG. 5, the solid line represents the displacement of the first tip member 20A in the first drive unit 1A, and the broken line represents the displacement of the second tip member 20B in the second drive unit 1B.

In the present embodiment, the first tip member 20A and the second tip member 20B are driven so that the phases of the trajectories are reversed, and alternately contact (contact) with the rotor 40. As described above, when the two tip members 20A and 20B are brought into contact with the rotor 40 alternately, when one tip member (for example, 20A) is in the deceleration region, the other tip member 20B is in the acceleration region. The same applies to the reverse case. Therefore, the pressing force of the pressing members 45A and 45B is N
_In the case of ₀ , even if one tip member (for example, 20A) is in a decelerating state, the other tip member 20B is in an accelerating state, and this tip member 20A does not contact the rotor 40,
No deceleration force acts on the rotor 40.

It is assumed that the magnitude of the pressing force in the actuator of the present embodiment is equal to the optimum condition for obtaining the maximum output of the actuator. Since the acceleration force of the first drive unit 1A and the second drive unit 1B are the same, the acceleration force of the actuator of the present embodiment is one by the amount of driving the rotor 40 using the two chip members 20A and 20B. It is larger than the actuator shown in the above-mentioned prior application in which the rotor is driven by the drive unit. Furthermore, assuming that the power consumption is constant, it is not necessary to consider the decrease in output due to the friction between the tip member 20A or 20B in the decelerating state and the rotor 40 as described above, so that the driving efficiency is increased by that amount. Become. Further, since the rotor 40 and the tip member 20A or 20B come into contact only in an acceleration region where the relative speed difference is small, wear of the tip members 20A and 20B and the rotor 40 is reduced, noise of the actuator is reduced, and The life of the actuator is extended.

In the above embodiment, the tip member 20
A, two piezoelectric elements 10A and 1B for driving 20B.
Although 0B or 10C and 10D are arranged so as to be orthogonal to each other, the present invention is not limited to this, and other angles such as 45 ° and 135 ° may be used. Further, the number of displacement elements in one drive unit 1A and 1B is not limited to two, and three or four displacement elements are used to drive three or more displacement elements. Is also good. Further, as the driving source of the displacement element, not only the piezoelectric element but also another electric or mechanical displacement element such as a magnetostrictive element may be used.

Further, the present invention is not limited to the truss-type actuator, and the contact portion is driven so as to draw an elliptical locus using a displacement element like a wedge-shaped actuator or an annular ultrasonic motor. Any structure may be used as long as the elliptical motion is frictionally transmitted to the driven member by pressurization.

[0041]

As described above, according to the actuator of the present invention, a plurality of displacement elements for generating a predetermined displacement and each of the displacement elements are respectively driven and driven by the displacement of each of the displacement elements. A plurality of driving members, a driven member driven by the contact of the driving member, a pressing member for pressing the driving member against the driven member, and the driving member being driven at different timings. A drive circuit for applying a drive signal to each of the displacement elements so as to contact the drive member is provided.

That is, for example, by bringing the two driving members into contact with the driven members such that the trajectories of the respective driving members have opposite phases, for example, at different timings,
Even when one of the driving members is in the deceleration region, the other driving member is in the acceleration region. Therefore, the driving member and the driven member in the deceleration region do not come into contact with each other, and no deceleration force acts between them.
As a result, the drive efficiency does not decrease due to the deceleration force, and the drive efficiency of the actuator can be increased.

Further, a truss-type actuator can be constructed by providing each of the driving members at the intersection of a plurality of displacement elements arranged so as to form a predetermined angle with each other.

Further, by arranging the driving members in parallel to the driven member in a predetermined direction, the movement of the driven members can be made smooth.

Further, the driven member, which is a rotating member, is arranged in parallel with the rotation axis of the driven member, whereby the driven member, which is a rotating member, can be rotated efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a truss-type actuator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a piezoelectric element used as a displacement element in the embodiment.

FIG. 3 is a diagram showing a block configuration of a drive circuit in the embodiment.

FIG. 4A is a diagram showing a natural mode of an actuator when two piezoelectric elements constituting a drive unit are stretched and vibrated, and FIG.
(B) shows the case of the anti-phase mode.

FIG. 5 shows a first tip member 20A in the embodiment.
And the displacement of the second tip member 20B and these and the rotor 40
It is a figure showing the relation of the contact state with.

[Explanation of symbols]

 1A: 1st drive unit 1B: 2nd drive unit 10A: 1st piezoelectric element (displacement element) 10B: 2nd piezoelectric element (displacement element) 10C: 3rd piezoelectric element (displacement element) 10D: 4th piezoelectric element (displacement) Element) 20A: First chip member (drive member) 20B: Second chip member (drive member) 30A: First base member 30B: Second base member 40: Rotor (driven member) 45A: First pressing member 45B : Second pressing member 46A: first pressing force adjusting mechanism 46B: second pressing force adjusting mechanism 50: oscillator 51A: first phase control section 51B: second phase control section 52A: first delay circuit 52B: second delay Circuit 52C: Third Delay Circuit 53A: First Amplitude Controller 53B: Second Amplitude Controller 54A: First Amplifier 54B: Second Amplifier 54C: Third Amplifier 54D: Fourth Amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H680 AA06 BB01 BB13 BB15 BB20 CC02 DD01 DD02 DD23 DD27 DD30 DD37 DD55 DD73 DD74 DD95 FF08 FF17 FF26 FF33 GG02 GG20 GG25

Claims (4)

[Claims] A plurality of displacement elements for generating a predetermined displacement, a plurality of drive members respectively coupled to the respective displacement elements and driven by the displacement of the respective displacement elements, and the drive member abutting on the plurality of displacement elements; A driven member to be driven;
A pressure member for pressing the driving member against the driven member, and a driving circuit for applying a driving signal to each of the displacement elements such that the driving member comes into contact with the driven member at different timings. An actuator characterized in that: 2. The actuator according to claim 1, wherein each of said driving members is provided at an intersection of a plurality of displacement elements arranged so as to form a predetermined angle with each other. 3. The actuator according to claim 1, wherein each of the driving members is arranged in parallel to the driven member in a predetermined direction. 4. The actuator according to claim 3, wherein the driven members are rotating bodies, and each of the driving members is arranged in parallel to a rotation axis of the driven members.