JP2001190080A - Vibration actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frictional material suitable for a vibration actuator using a vibrator having a high resonance frequency. SOLUTION: The vibration actuator comprises a vibrator having an electro- mechanical converter excited in response to a driving frequency to be inputted, and the frictional material provided between the vibrator and a relatively moving member and operating together with the vibration of the vibrator. In this case, the relatively moving member is relatively moved to the vibrator by the frictional force of the material and the moving member. The driving frequency inputted to the converter is 100 kHz or more. The flexual modulus of the frictional material of a resin is 13 GPa or more. This resin is provided on its at least surface contacted with the moving member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator that excites a predetermined vibration to a vibrator, transmits the vibration energy to a relative moving member, and relatively moves the relative moving member and the vibrator.

[0002]

2. Description of the Related Art Conventionally, this type of vibration actuator has
Donut plate-shaped vibration that simultaneously generates a radially symmetric elongation vibration mode extending (expanding and contracting in the radial direction) from the center to the outer peripheral direction and a non-axisymmetric in-plane vibration mode bending non-axisymmetrically in the same plane There is a structure using a child. This vibration actuator is, for example, “(R, 1) − ((1,
1)) Improvement of characteristics of ultrasonic linear motor using mode piezoelectric ring (Takano, Tomikawa; Proceedings of the 12th Ferroelectric Application Conference, pp. 79-80) "," New Edition Ultrasonic Motor (Ueba, Tomikawa) Trikes, P. 22-23, P. 67;
−68) ”and Japanese Patent Publication No. 6-26994, which is suitable for a thin structure and has features such as high speed and high thrust.

One example is shown in FIG. FIG. 4 is a schematic front view of a conventional vibration actuator. And FIG.
FIG. 8 is a diagram when the state in which the vibration actuator is in contact with the relative moving member 73 is viewed in a direction perpendicular to the vibration direction. In this vibration actuator, a vibrator 71 includes a piezoelectric element and an electrode for applying a voltage to the piezoelectric element. The vibrator 71 has a donut plate shape as shown in FIG. 4, and relative moving members 73 a and 73 b moving relatively to the vibrator 71 are pressed against the periphery thereof by a spring 74. In addition, the vibrator 71 is the
A friction material 72 is provided in a portion that is in pressure contact with 3a and 73b.

An electrode 71 provided on the vibrator 71
By applying an alternating voltage having a different phase between the electrodes 2a and 712b and an electrode (not shown) on the back side to generate a vibration having an elliptical motion in a portion of the vibrator 71 where the friction material 72 is provided, the relative voltage is increased. The moving member 73 moves relatively to the vibrator 71. On the other hand, in recent years, with the miniaturization of camcorders and optical disk players, miniaturization of actuators used in tape drive units of camcorders and optical read head drive units of optical disk players has been required.

[0005]

As described above, in order to reduce the size of the vibration actuator, one method of reducing the size of the vibrator is considered. However, when the size of the vibrator is reduced, the resonance frequency in the vibration of the vibrator increases, and the driving frequency of the AC voltage applied to the piezoelectric element provided on the vibrator necessarily increases.

When the size of the vibrator is reduced and the driving frequency is increased, the vibration amplitude of the vibrator tends to be reduced. On the other hand, in the contact portion of the vibrator with the relative moving member,
A friction material is provided to secure a frictional force with the relative moving member. From the viewpoint of the whole vibration actuator, the friction material used includes resin, ceramics, and metal. When a resin material that is easily deformed is used for the friction material, displacement due to small vibration generated in the vibrator is spent for deformation of the sliding material,
It was not transmitted to the relative moving member, and the desired driving force and driving speed could not be obtained.

Accordingly, an object of the present invention is to provide a friction material suitable for a vibration actuator using a vibrator having a high resonance frequency.

[0008]

According to the present invention, there is provided a vibrator having an electro-mechanical transducer for exciting according to an input drive frequency, a vibrator of the vibrator and a relative moving member. And a friction material provided in a portion located between the vibration member and the relative movement member can be relatively moved with respect to the vibrator by a frictional force between the friction material and the relative movement member, A drive frequency input to the electro-mechanical conversion element is 100 kHz or more, and a resin having a flexural modulus of friction of 13 GPa or more is provided on at least a surface in contact with the relative moving member.

As the friction material used in the vibration actuator having a driving frequency of 100 kHz, it is preferable to use a resin which does not easily damage the relative moving member. Furthermore, by selecting the flexural modulus of the friction material to be 13 GPa or more, the friction material is less likely to be deformed, so that the thrust generated by the vibration actuator can be efficiently transmitted to the relative moving member.

In the present invention, the electro-mechanical transducer has a hollow cylindrical shape, one of the electro-mechanical transducers has a plurality of electrodes on a hollow disk surface, and the other has a plurality of electrodes. The hollow disk surface has a single electrode, and the friction material is
Provided on the cylindrical side surface of the mechanical transducer, the vibrator simultaneously generates a radially symmetric elongation vibration mode that expands and contracts in the radial direction and a non-axisymmetric in-plane vibration mode that bends non-axisymmetrically in the same plane. By using the above-described friction material for the vibration actuator, it is possible to obtain a thin and small vibration actuator having good driving efficiency.

The above-mentioned friction material is preferably applied to a vibration actuator using a vibrator having a driving frequency of 180 kHz or more when vibrating the vibrator. Further, since the friction material has a thickness of 0.3 mm or less in a direction between the vibrator and the relative moving member, deformation of the friction material is further reduced. Can be obtained.

Further, as the above-mentioned friction material, a material whose main material is made of at least one of polyphenylene sulfide and polyether ether ketone, and which has carbon fibers or whiskers in the main material,
The material has good slidability with respect to the relative moving member and good drive transmission. Next, embodiments of the present invention will be described, and the present invention will be described in more detail. However, the present invention is not limited thereto.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vibration actuator according to an embodiment of the present invention will be described with reference to FIG. In the vibration actuator according to the present embodiment, the vibrator 1 is fixed by fixing the center axis of the vibrator 1 to the movable block 42 and biasing the movable block 42 by the spring 46 in the direction in which the relative moving member 3 is disposed. It has a configuration in which the relative movement member 3 is urged via the friction material 2. And
AC voltages having different phases are applied between the electrodes 12a and 12b of the vibrator 1 and electrodes (not shown) on the surface opposite to the surface shown in FIG. 1 to excite the vibrator 1. Thereby, the relative moving member 3 and the vibrator 1 can be relatively moved.

The vibrator 1 has the configuration shown in FIG. FIG. 2 is a diagram showing the vibrator 1 of the vibration actuator using the radially symmetric elongation vibration mode and the non-axisymmetric in-plane vibration mode. The vibrator 1 includes a piezoelectric element 11 which is an electro-mechanical conversion element, an electrode 12 for applying a voltage to the piezoelectric element 11, and a friction material 2. The piezoelectric element 11 is formed by forming a piezoelectric material such as PZT into a substantially donut shape and polarizing the entire surface in the thickness direction.

The shape of the vibrator 1 includes a radially symmetric elongation vibration mode (R, 1) and a non-axisymmetric in-plane vibration mode ((1,
It is designed and manufactured so that the resonance frequencies of 1) and 2) are almost equal. The piezoelectric element 11 has a surface as shown in FIG.
As shown in FIG. 2, fan-shaped first and second electrodes 12a and 12b are formed, and on the back surface, a third electrode 12c is formed on almost the entire surface as shown in FIG. 2B.

The vibrator 1 is driven by a driving voltage generating circuit including an oscillator (not shown), a phase shifter, an amplifier, and the like.
A first AC voltage is applied to the electrode 12a. In addition, a second AC voltage having a phase that is electrically different from the first AC voltage by (π / 2) is applied to the second electrode 12b. The third electrode 12c on the back surface is connected to the GND potential.

The vibrator 1 has a frequency of 2 V by bringing the frequency of the AC voltage close to the resonance frequencies of the two vibration modes.
Resonating in two modes, radially symmetric elongational vibration and non-axisymmetric in-plane vibration occur simultaneously. The radially symmetric elongation vibration (R, 1) is a stretching vibration symmetrical in the radial direction (radial direction) with the point A as a node, as shown in FIG. The shape is shown by a dotted line. C1, C2
At the point, a displacement of the radial component Ur appears.

Also, non-axisymmetric in-plane vibration ((1, 1))
As shown in FIG. 2 (D), as shown by a broken line, the points of B1 and B2 are used as nodes to generate a distortion such that the points B1 and B2 are collapsed in the same plane, and the bending vibration is repeated right and left. Yes, the points C1 and C2 on the circumference have a displacement component Uθ in the direction of the arrow. Then, the vibrator 1 generates an elliptical motion as shown in FIG. 2A as a displacement obtained by combining the two vibrations at the positions of the C1 and C2 points (driving force extracting portions). Using the displacement component of Uθ in the elliptical motion, the friction material 2
The relative moving member 3 can be relatively moved with respect to the vibrator 1 via.

For fixing the vibrator 1, as shown in FIG. 1, the vibrator 1 is supported by screws (not shown) on a column (not shown). This support is a movable block 4
It is fixed to 2. The movable block 42 is movable in the direction of the arrow shown in FIG. 1 while sliding on the side surface of the guide 45.

The spring 46 has one end fixed to the guide 45 and the other end pressed against the movable block 42.
The vibrator 1 fixed to the movable block 42 is urged to the relative moving member 3 by the urging force of a spring 46. Therefore, the friction material 2 provided on the vibrator 1 and the relative moving member 3
Are brought into contact with each other while being applied with an urging force, so that the kinetic energy generated by exciting the vibrator 1 can be efficiently transmitted to the relative moving member 3.

Incidentally, the relative moving member 3 is
The vibrator 1 is movably supported on the upper surface of the base 44 along the direction of the driving force of the vibrator 1 by a linear guide 7 having a shape protruding from the base. The oscillator 1 fixed in this way and the relative moving member 3 movably supported by the oscillator 1
When the first and second AC voltages having different phases are applied to the first and second electrodes 12a and 12b provided in the vibrator 1, the elliptical motion occurs at the position where the friction material 2 of the vibrator 1 is provided. . At this time, since the relative moving member 3 is in pressure contact with the friction material 2, there is a gap between the sliding surface of the friction material 2 and the relative moving member 3.
A frictional force is generated in the moving direction of the relative moving member 3, and a linear driving force of the relative moving member 3 is obtained.

The electrodes 12a provided on the vibrator 1
The phase difference between the first and second AC voltages applied to
By changing from // 2 to -π / 2, the straight traveling direction can be reversed. Further, by moving the driving frequency closer to or farther from the resonance frequency of the vibrator, it is possible to increase or decrease the speed of the straight running operation. This increase or decrease in speed
It is also possible by increasing or decreasing the voltage of the AC voltage.

By the way, in order to reduce the size of the vibration actuator according to the embodiment of the present invention, the outer shape of the vibrator 1 was 10 mm, the inner diameter of the center hole was 3 mm, and the thickness was 1 mm. Then, the aforementioned radially symmetric elongation vibration (R, 1),
As a result of making the resonance frequency with the non-axisymmetric in-plane vibration ((1, 1)) substantially the same, the resonance frequency was about 180 kHz. Therefore, the driving frequency of the applied AC voltage is set to 1
It was decided to drive at 80 kHz.

When driven in such a situation, the amplitude of each vibration mode near the provision of the friction material 2 is about 0.2 μm for radially symmetric elongation vibration (R, 1). For non-axisymmetric in-plane vibrations ((1,1)), about 0.
It was 3 μm. Therefore, as a friction material for a vibration actuator, Vespel SP-21, a trade name generally used
1 (main material: polyimide, filler: graphite), the relative moving member 3 could not be moved. However, the friction material 2 has a trade name of Valpound CU3030 (main material: PPS (polyphenylene sulfide), filler: CF (carbon fiber), 9AlO
With ₃ · 2B ₂ O ₃ (whiskers)), it was possible to move the relative movement member 3.

The present inventors have conducted intensive studies on this and found the following. Generally, a small vibration actuator is made smaller by making its vibrator smaller.
It has a driving frequency of 100 kHz or more, which is at least one digit different from the driving frequency up to now. However, when the resonance frequency of the vibrator becomes 100 kHz or more, which is at least one digit different from the drive frequency up to now, the vibration amplitude generated in the vibrator 1 is small.
If a material having a low flexural modulus is used for the friction material 2, displacement due to vibration is spent only on deformation of the friction material 2. This is because, when the flexural modulus is low, the compressive modulus and the lateral modulus become small, so that the compressive deformation and the shear deformation are easily performed. The “compression deformation” mentioned here means
This shows a modification as shown in FIG. The dotted line shows the shape of the friction material 2 when the vibration stops, and the solid line shows the shape of the friction material 2 during the radially symmetric elongation vibration. The “shear deformation” indicates a deformation as shown in FIG.
Also in this figure, the dotted line shows the shape of the friction material 2 when the vibration is stopped, and the solid line shows the shape of the friction material 2 during the non-axisymmetric plane vibration.

Further, the friction material 2 needs to be one that does not easily damage the relative moving member 3 that transmits the driving force due to vibration. Therefore, the present inventor uses a substance having a high flexural modulus as the friction material 2 to obtain a 100 kHz
It has been found that it is preferable to use the friction material 2 made of a resin having a bending elastic modulus of 13 GPa or more for the vibration actuator having the above high driving frequency.

In order to find out this, the following verification was performed. A plurality of vibration actuators having the same configuration as the above-described vibration actuator and having dimensions changed so as to have different resonance frequencies were prepared, and friction members 2 having different bending elastic moduli were provided on the respective vibrators 1.
Then, a voltage having a drive frequency corresponding to the resonance frequency of each vibrator was applied to verify whether or not the relative moving member 3 moved.

Table 1 shows the results. Table 1 shows whether or not the vibration actuator could move the relative moving member when the bending elastic modulus or the thickness was changed with respect to the driving frequency of the vibration actuator. Incidentally, the crosses could not be moved, the circles could be moved, and the horizontal bars were not measured.

[0029]

[Table 1]

According to this table, several tens of kiloh
With respect to a vibration actuator driven at a drive frequency of z or less, it was possible to move the relative moving member even with a friction material having a small bending elastic modulus, but at least 10
It can be seen that for a vibration actuator driven at a driving frequency of 0 kHz or more, the relative moving member cannot be moved unless the bending elastic modulus is 13 GPa or more.

Therefore, in order to reduce the size of the vibrator, a vibrating actuator in which the vibrator itself is miniaturized is mainly 100 k.
Since it has a resonance frequency of not less than Hz, it is understood that a preferable friction material 2 used for such a vibration actuator preferably has a flexural modulus of 13 GPa or more. Also, looking at Table 1, there is a case where the relative moving member does not move even if the flexural modulus is simply 13 GPa or more. In such a case, it has been found by the present inventors that the friction material can be moved by making the thickness of the friction material 0.3 mm or less. It is considered that by setting the thickness of the friction material to 0.3 mm or less, the lateral elasticity and the compressive elasticity are increased. Therefore, the friction material that easily transmits the driving force more efficiently to the relative moving member is preferably 0.3 mm or less.

It is understood that when the friction material is made thinner in this manner, the lateral elasticity and the compressive elasticity are increased. However, from the knowledge of the present inventor, the frictional material of a small vibration actuator having a driving frequency of 100 kHz or more is known. It has been found that a sufficient effect cannot be obtained simply by reducing the thickness, and a sufficient effect cannot be exerted unless the flexural modulus is 13 GPa or more.

The material of the friction material used for the vibration actuator having a driving frequency of 100 kHz or more is as follows.
In addition to the product name Valpound CU3030 mentioned above,
Sumiploy KCK3420 (main material: PEEK (polyetheretherketone), filler: carbon fiber,
PTFE (polytetrafluoroethylene) can also be used. The friction material that can be used is not limited to the above-mentioned trade names, but may be made of at least one of PPS and PEEK, as long as the main material contains carbon fiber or whisker. It goes without saying that the elastic modulus has 13 GPa or more.

The present invention is not limited to the vibration actuator having the above-mentioned shape, but can be applied to any other vibration actuator having a driving frequency of 100 kHz or more. For example, in the embodiment of the present invention, an actuator having a combined vibration mode in in-plane vibration has been described. However, an L1-B4 type vibration mode in which a bending force and a longitudinal vibration are combined to obtain a driving force is also described. May be used.

Also, not all the friction material is made of resin, but the side of the friction material fixed to the vibrator 1 may be made of ceramic and the surface in contact with the relative moving member may be made of resin. . However, when the friction material is formed of a different material, and when there is difficulty in manufacturing, it is preferable that the friction material is formed only of the resin. Also, as for the electro-mechanical conversion element, a vibration actuator using something other than the piezoelectric element may be used.

It is to be noted that such a small vibration actuator is preferably used as a linear drive element for moving an optical pickup mechanism such as a portable compact disk or mini disk. As described above, the vibration actuator according to the present invention is small in size and has a high ability to transmit the driving force to the relative moving member, and converts the rotational motion of the rack and pinion into a linear motion even in the case of linear driving. Since a mechanism is not required, it is suitable as a driving element used for a small device.

[0037]

As described above, according to the present invention, the vibrator is made smaller in order to reduce the size.
By providing the vibration actuator having a frequency of 13 Hz or more with a friction material having a bending elastic modulus of 13 GPa or more, the displacement generated in the vibrator can be efficiently transmitted to the relative moving member, and the performance of the vibration actuator is improved. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a vibration actuator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a vibration mode of the vibration actuator according to the embodiment of the present invention.

FIG. 3 is a diagram showing a state of deformation of a friction material provided in the vibration actuator according to the embodiment of the present invention.

FIG. 4 is a schematic diagram of a conventional vibration actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vibrator 11 ... Piezoelectric element 12a, b ... Electrode 2 ... Friction material 3 ... Relative moving member 42 ... Movable block 45 ... Guide 46 ... Spring 7. ··Linear guide

Claims (5)

[Claims] 1. A vibrator having an electro-mechanical transducer for exciting according to an input drive frequency, and a friction member provided at a portion of the vibrator located between the vibrator and a relative moving member. And a vibration actuator in which the relative moving member relatively moves with respect to the vibrator due to a frictional force between the friction material and the relative moving member, wherein the driving frequency input to the electro-mechanical conversion element is A vibration actuator, wherein a resin having a bending elastic modulus of 13 GPa or more is provided at least in a portion in contact with the relative moving member at least at 100 kHz or more. 2. The electro-mechanical conversion element has a hollow cylindrical shape, one of the electro-mechanical conversion elements has a plurality of electrodes on a hollow disk surface, and the other has a hollow shape. The disk surface has a single electrode, the friction material is provided on a cylindrical side surface of the electro-mechanical conversion element, the vibrator is radially symmetric elongation vibration mode that expands and contracts in a radial direction, 2. The vibration actuator according to claim 1, wherein a non-axisymmetric in-plane vibration mode which bends non-axisymmetrically in the same plane is simultaneously generated. 3. The vibration actuator according to claim 1, wherein the driving frequency is 180 kHz or more. 4. The vibration actuator according to claim 1, wherein the friction material has a thickness of 0.3 mm or less. 5. The friction material according to claim 1, wherein the main material is made of at least one of polyphenylene sulfide and polyether ether ketone, and the main material has carbon fibers or whiskers. The vibration actuator according to any one of claims 4 to 4.