JPH09308274A - Vibrating motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vibrating motor which has a wide driving frequency range and is very efficient by serially connecting an inductance element with an electrode which applies a frequency signal to an elastic body and setting the value of the inductance element to a specified one. SOLUTION: Frequency signals are applied to energy converting elements 2a, 2b which are provided in an elastic body 1 to produce first vibration and second vibration which cross the first one and these two kinds of vibrations are synthesized to obtain driving force. At that point, inductance elements 9, 10 are serially connected to electrodes 4a-4d which apply frequency signals to the elastic body 1. The values of the inductance elements 9, 10 are so set that dθ(f)=θ1 (f)-θ2 (f) may satisfy -π/2<dθ(f)<π/2 or dθ(f)<π/2, where a phase of the current for the driving voltage of the first vibration is θ1 (f) and that of the second one is θ2 (f) and a difference between the two phases is dθ(f).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standing wave type vibration motor which obtains a driving force by a standing wave, and more particularly to a drive circuit thereof.

[0002]

2. Description of the Related Art Recently, a traveling wave type vibration motor, which has been attracting attention, has a feature that it can be easily driven at a low speed and a high torque can be obtained. Has been done.

In this vibration motor, since it is generally necessary to apply a voltage of several tens to several hundreds of volts to the piezoelectric vibrating body, the applied voltage is boosted using an inductance element such as a coil, and this is used as a drive voltage. There is.

This method is used exclusively in a traveling wave type vibration motor, and even if it is used in a standing wave type vibration motor, it will serve the purpose of boosting the applied voltage. However, as a result of the study by the applicant, it was found that a new effect can be obtained depending on the method of selecting the inductance element such as the coil.

Therefore, the effect will be described below with reference to a conventional example of a standing wave vibration motor.

Conventionally, as a vibration motor utilizing standing wave vibration, a standing wave type vibration motor using a standing wave generated in an elastic body is known. This is to apply a voltage of a specific frequency to a vibrating element provided integrally with the elastic body to excite flexural vibration and longitudinal vibration in the elastic body, and through the elastic body or the motion extractor provided in the vibrating element. To obtain driving force.

The driving principle of the standing wave type vibration motor will be briefly described with reference to FIG. In FIG. 7, 71 is an elastic body made of an elastic member, 72a and 72b are piezoelectric vibrating bodies as electric-mechanical energy conversion elements for exciting the elastic body 71 to longitudinal vibration and bending vibration, and arrows indicate polarization directions. There is. 73a and 73b are motion extractors integrally provided on the elastic body 71, 74a, 74b, 74c and 74d are electrodes for applying a voltage of a specific frequency to the piezoelectric vibrating bodies 72a and 72b, and 75 is a moving body. . Further, 76 is a pressing spring for pressing the moving body 75 against the motion extracting bodies 73a, 73b with a predetermined pressing force, and 77 is a frictional force between the pressing spring 76 and the moving body 75 generated by the pressing force of the pressing spring 76. This is a bearing to reduce the amount.

In the above-described structure, when voltages of specific frequencies having 90 ° different phases (described as sin and cos in the figure) are applied to the electrodes 74a and 74d at 74b and 74c, the piezoelectric vibrating body 72a. , 72b repeats expansion and contraction at the drive frequency. This piezoelectric vibrating body 72a, 7
By the expansion and contraction of 2b, longitudinal vibration and bending vibration are excited in the elastic body 71, and further, by the combined vibration of these, the motion extractors 73a and 73b perform elliptic motions rotating in the same direction. Therefore, when the moving body 75 is pressed against the motion extracting bodies 73a and 73b by the pressing spring 76, the moving body 75 moves in the arrow direction, for example.

Although the bending vibration is shown as a fourth mode and the longitudinal vibration is shown as a first mode in the figure, it is not limited to this as long as a driving force can be obtained.

[0010]

As described above, the standing wave type vibration motor has two vibration modes (bending vibration and longitudinal vibration in the conventional example, but is not limited thereto) at a certain driving frequency. In order to resonate at the same time, it is necessary to have a shape such that the resonance frequencies of the two vibration modes substantially match.

However, even if the shape itself can be machined with high accuracy, the anisotropy of the material, the variation in the thickness of the adhesive when the elastic body and the piezoelectric vibrating element are integrated, and the hardening of the adhesive. It is very difficult to make the resonance frequencies of the two vibration modes substantially coincide with each other as shown in FIG. 9 due to variations in hardness after curing depending on the conditions. Note that FIG. 9 shows the absolute value | Y | of the admittance characteristic by replacing the standing wave vibration motor shown in FIG. 7 with an equivalent circuit shown in FIG. In FIG. 9, reference numeral 91 represents the absolute value | Y ₁ | of flexural vibration admittance, and 92 represents the absolute value | Y ₂ | of longitudinal vibration admittance. The absolute value of the admittance of bending vibration | Y ₁ | has a maximum value at the frequency f ₁ , and the absolute value of the admittance of longitudinal vibration | Y ₂ |
Takes a maximum at frequency f ₂ .

FIG. 10 shows the phase characteristic of current with respect to voltage in the equivalent circuit shown in FIG. In FIG. 10, 93 represents the phase characteristic θ ₁ (f) of bending vibration, and 94 represents the phase characteristic θ ₂ (f) of longitudinal vibration. Then, the standing wave type vibration motor having such a resonance characteristic is derived from the current phases θ ₁ (f) 93 and θ ₂ (f) 94 with respect to the voltage in each of the two vibration modes, as shown in FIG. Current difference between longitudinal vibration and bending vibration dθ (f) 95 (θ ₁
(F) -θ ₂ (f)) is 180 between the two resonance frequencies.
exceeds deg. Note that, in FIG. 11, in comparison with the phase characteristics in the equivalent circuit of FIG.
FIG. 11 shows an actual characteristic obtained by shifting the phase by 90 deg from the characteristic of FIG. 10 in consideration of the point having a phase difference of 0 deg. As a result, the direction of rotation of the elliptic motion generated in the oscillator is different between the two resonance frequencies and the frequencies before and after the resonance frequency, and the drivable frequency range in which the thrust (velocity) is obtained as shown in FIG. There was a problem that it became narrower and the efficiency became worse.

Therefore, an object of the present invention is to provide a standing wave type vibration motor having a wide driving frequency range and high efficiency.

[0014]

The structure for achieving the object of the invention according to the present application is such that an elastic body is integrally provided with a vibrating body, and a voltage of a specific frequency is applied to the vibrating body to apply the voltage to the elastic body. Exciting the first vibration and the second vibration orthogonal to this,
In a standing wave type vibration motor that obtains these synthetic vibrations as a driving force through an elastic body or a motion extractor provided in the vibrating body, an inductance element is connected in series to a driving electrode that applies a voltage of a specific frequency to the vibrating body. , And the phase difference dθ (f) derived from the current phases θ ₁ (f) and θ ₂ (f) with respect to the voltage in each of the two vibration modes in the equivalent circuit of the ultrasonic motor at that time falls within a predetermined range. By setting the inductance element as described above, the driving frequency range is widened as compared with the conventional standing wave type vibration motor, and a highly efficient standing wave type vibration motor can be realized.

According to the present invention of claim 1, the elastic body is electrically
A mechanical energy conversion element section is arranged, a frequency signal is applied to the conversion element section, and the elastic body is excited with a first vibration and a second vibration orthogonal to the first vibration, and a combined vibration of these vibrations. In the vibration motor that obtains the driving force by, the inductance element is connected in series to the electrode that applies the frequency signal to the elastic body, and the value of the inductance element is used in the equivalent circuit of the vibration motor. Phase difference dθ (f) = θ ₁ (f) −θ ₂ (f) between the phases θ ₁ (f) and θ ₂ (f) of the current with respect to the driving voltage of each of the first vibration and the second vibration. Is -π / 2 <d
The vibration motor set to a value satisfying θ (f) <π / 2 or dθ (f) <π / 2 is provided to achieve the above object.

According to the second aspect of the present invention, the electromechanical energy conversion element section is arranged on the elastic body, and a frequency signal is applied to the conversion element section, and the elastic body undergoes the first vibration and the first vibration. In a vibration motor, a second vibration that is orthogonal to the vibration is excited and a driving force is obtained by these combined vibrations. In a vibration motor, an inductance element is connected in series to an electrode that applies the frequency signal to the elastic body. Together with the value of the inductance element, when considering the phase difference between the first vibration and the second vibration of the vibration motor, of the current for each drive voltage of the first vibration and the second vibration Phase θ
Phase difference between ₁ (f) and θ ₂ (f) dθ (f) = θ ₁
(F) −θ ₂ (f) is −a−π / 2 <dθ (f) <π /
A vibration motor having a value satisfying 2 + a or dθ (f) <π / 2 + a (a is a phase difference between the first vibration and the second vibration) is provided to achieve the above-mentioned object in the same manner as in claim 1. Is.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A vibration motor according to the present invention will be described below. FIG. 1 is a circuit diagram of a motor according to the present invention. In FIG. 1, 1 is an elastic body made of an elastic member, 2
Reference numerals a and 2b are piezoelectric or electrostrictive vibrating bodies as electro-mechanical energy conversion elements for exciting the elastic body 1 for longitudinal vibration and bending vibration, and the polarization is subjected to the polarization treatment shown in FIG. Reference numerals 4a, 4b, 4c, and 4d are electrodes for applying a voltage of a specific frequency to the piezoelectric or electrostrictive vibrating bodies 2a and 2b. The elastic body 1 and the piezoelectric or electrostrictive vibrating body 2a,
2b is in a bonded state with an adhesive or the like, and forms the vibrator 3. Further, 5 is an oscillator for generating a voltage of a specific frequency, 6 is a 90 deg phase shifter, and 7 and 8 are amplifiers. Further, as shown in FIG. 1, this motor is a two-phase drive, and the phase of the alternating voltage applied to each phase is 90 deg.
There is no difference between the first phases 4a and 4d and the second phases 4b and 4c except that the phase shifter shifts ± 90 deg.

FIG. 2 shows an equivalent circuit of the vibration motor shown in FIG. The equivalent circuit of the super vibration motor is an RLC series circuit (equivalent resistance 11 of resistance value R ₁ ,
Equivalent coil 12 with self-inductance L ₁ and capacitance C
₁ equivalent capacitor 13) and a capacitor 14 having the intrinsic capacitance C _d of the vibrator 1 connected in parallel. Further, 15 is an inductance element L _e such as a coil connected in series to the equivalent circuit of the vibration motor.
In addition, R of the mechanical resonance portion of the vibration motor in the equivalent circuit
The LC series circuit portions R ₁ , L ₁ and C ₁ have different values for bending vibration and longitudinal vibration.

FIG. 3 shows the absolute value | Y | of the admittance characteristic of the equivalent circuit of the vibration motor shown in FIG. In FIG. 3, 16 represents the absolute value | Y ₁ | of bending vibration admittance, and 17 represents the absolute value | Y ₂ | of longitudinal admittance. The absolute value | Y ₁ | of flexural vibration admittance has a maximum value at the frequency f ′ ₁ and the absolute value | Y ₂ | of longitudinal admittance has a maximum value at the frequency f ′ ₂ . All of these have frequencies lower than the initial mechanical resonance frequency shown in the figure due to the influence of the inductance L _e connected in series to the vibration motor.

FIG. 4 shows the phase characteristics of current with respect to voltage in the equivalent circuit shown in FIG. In the figure,
Reference numeral 18 represents a phase characteristic θ ₁ (f) of bending vibration, and 19 represents a phase characteristic θ ₂ (f) of longitudinal vibration.

Similar to FIG. 11, FIG. 5 shows the phase characteristic θ ₁ (f) of the bending vibration and the phase of the longitudinal vibration in consideration of the fact that the bending vibration has a phase difference of 90 deg with respect to the longitudinal vibration in the actual motor. From the characteristic θ ₂ (f), the phase difference between each vibration dθ
It is what (f) was shown. In the figure, 20 represents the phase difference dθ (f). As can be seen from FIG. 5, there is no frequency band where the phase difference dθ (f) exceeds 180 deg near the resonance point of each vibration. Generally, the velocity of the moving body is proportional to the instantaneous values of the bending vibration and the longitudinal vibration of the elastic body, and the instantaneous value of the amplitude of the bending vibration and the longitudinal vibration is proportional to the current flowing in the piezoelectric body that constitutes the vibrator. It is shown that the rotation direction of the elliptic motion generated in the oscillator does not change near the resonance point of the vibration.

Next, FIG. 6 shows thrust (speed) characteristics in this case. Due to the influence of the inductance L _e connected in series to the vibration motor, the driving voltage is constant and the current is significantly larger than in the conventional case without the inductance L _e , so the thrust is also greatly increased. Moreover, since the rotation direction of the elliptical motion generated in the oscillator does not change near the resonance point, the operation suddenly becomes unstable at a driving frequency lower than the resonance point as in the conventional ultrasonic motor, or suddenly in the worst case. Phenomena such as stopping the operation are alleviated.

In this way, the value of the inductance L _e is the phase difference dθ (f) between the phase difference characteristic of bending vibration and the phase difference characteristic of longitudinal vibration in the equivalent circuit of the above-mentioned motor, −π / 2 <dθ
By setting (f) <π / 2 or dθ (f) <π / 2, it is possible to prevent the rotation direction from being changed near the resonance point. The above phase difference is represented by the phase difference in the equivalent circuit. However, since the phase difference between bending vibration and longitudinal vibration is 90 deg in an actual motor, the above phase difference dθ (f) is the actual motor difference. Then, in consideration of the phase difference between the bending vibration and the longitudinal vibration, -π <dθ (f) <π or dθ (f)
<Π will be set.

Further, the phase difference between bending vibration and longitudinal vibration is 90d.
The reason why it becomes eg is that signals having a phase difference of 90 deg are applied to the electromechanical energy conversion element, and when a phase difference signal other than 90 deg is applied to the conversion element, bending vibration is generated. The phase difference of longitudinal vibration is 90
In this case, the phase difference dθ
(F) is -a-π / 2 <dθ (f) <π / 2 + a or d
It may be set to θ (f) <π / 2 + a (a is the phase difference between bending and longitudinal vibration).

In this embodiment, the vibration modes generated in the elastic body are the bending vibration and the longitudinal vibration, but it is not limited to this as long as the driving force can be obtained.

[0026]

As described above, according to the invention of claim 1, it can be driven without changing the rotation direction even near the resonance frequency, the driving frequency range is widened, and the vibration motor can be provided with high efficiency. . According to the second aspect of the present invention, it is possible to provide a vibration motor with high efficiency as in the first aspect.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a drive circuit of a standing wave type vibration motor according to the present invention.

FIG. 2 is an equivalent circuit diagram showing one vibration mode of the standing wave type vibration motor according to the present invention.

FIG. 3 is a diagram showing admittance characteristics of the standing wave type vibration motor shown in FIG.

FIG. 4 is a diagram showing phase characteristics of the standing wave type vibration motor shown in FIG.

5 is a diagram showing a phase difference characteristic of the standing wave type vibration motor shown in FIG.

6 is a diagram showing thrust characteristics of the standing wave type vibration motor shown in FIG.

FIG. 7 is a diagram illustrating components of a standing wave type vibration motor.

FIG. 8 is an equivalent circuit diagram showing one vibration mode of a conventional standing wave vibration motor.

9 is a diagram showing admittance characteristics of the standing wave type vibration motor shown in FIG.

10 is a diagram showing phase characteristics of the standing wave type vibration motor shown in FIG.

11 is a diagram showing a phase difference characteristic of the standing wave type vibration motor shown in FIG.

12 is a diagram showing thrust characteristics of the standing wave type vibration motor shown in FIG.

[Explanation of symbols]

 1 elastic body 2a, 2b piezoelectric vibrating body 3 vibrator 4a, 4b, 4c, 4d electrode 5 oscillator 6 90 ° phase shifter 7, 8 amplifier 9, 10 inductance element

Claims (5)

[Claims] 1. An electromechanical energy conversion element part is arranged on an elastic body, and a frequency signal is applied to the conversion element part.
A vibration motor that excites a first vibration and a second vibration orthogonal to the first vibration in an elastic body to obtain a driving force by a combined vibration of these vibrations. The frequency signal is applied to the elastic body. An inductance element is connected in series to the electrode to be used, and as the value of the inductance element, the current phase θ ₁ (for each drive voltage of the first vibration and the second vibration in the equivalent circuit of the vibration motor is f) and θ ₂ (f)
And the phase difference dθ (f) = θ ₁ (f) −θ ₂ (f) is −π
A vibration motor having a value satisfying / 2 <dθ (f) <π / 2 or dθ (f) <π / 2. 2. An electromechanical energy conversion element part is arranged on an elastic body, and a frequency signal is applied to the conversion element part,
A vibration motor that excites a first vibration and a second vibration orthogonal to the first vibration in an elastic body to obtain a driving force by a combined vibration of these vibrations. The frequency signal is applied to the elastic body. While connecting the inductance element in series to the electrode to be, as the value of the inductance element, when considering the phase difference between the first vibration and the second vibration of the vibration motor, the first vibration and Phase difference dθ between the current phases θ ₁ (f) and θ ₂ (f) of the second vibration with respect to each drive voltage.
(F) = θ ₁ (f) −θ ₂ (f) is −a−π / 2 <dθ
A vibration motor characterized by being set to a value satisfying (f) <π / 2 + a or dθ (f) <π / 2 + a (a is the phase difference between the first vibration and the second vibration). 3. The vibration motor according to claim 1, wherein the first vibration is bending vibration and the second vibration is longitudinal vibration. 4. The first and second electric wires on one surface of the elastic body.
The mechanical energy conversion element part is arranged, and the third and fourth electro-mechanical energy conversion element parts are arranged on the other surface, the first and third element parts are opposed to each other, and the second and fourth element parts are opposed to each other. The first frequency signal is applied to the first and fourth element parts, and the frequency signal having a phase different from that of the first frequency signal is applied to the second and third element parts. The vibration motor according to Item 3. 5. A phase difference a between the first vibration and the second vibration.
The vibration motor according to claim 2, wherein is 90 degrees.