JPH0519392B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a drive circuit for a vibration wave motor that frictionally drives a moving body using progressive vibration waves, and particularly to a drive circuit suitable for vibrating the vibration waves into a stable resonance state. The first is a schematic diagram of an embodiment of a vibration wave motor driven by progressive vibration waves, which has recently been put into practical use.
It is shown in the figure. In the figure, 1a and 1b are electrostrictive elements as electro-mechanical energy conversion elements, for example.
PZT (lead zirconate titanate), 2 is a vibrating body made of an elastic material, and electrostrictive elements 1a and 1b are bonded together. The vibrating body 2 is held on the stator (not shown) side together with the electrostrictive elements 1a and 1b. Reference numeral 3 denotes a moving body which is pressed into contact with the vibrating body 2 and forms a rotor. A plurality of electrostrictive elements 1a and 1b are each glued together, and one group of electrostrictive elements 1a and another group of electrostrictive elements 1b are shifted in pitch by 1/4 wavelength of the wavelength λ of the vibration wave. Placed. The electrostrictive elements 1a, 1a, 1a, . . . in the group are arranged at a pitch of 1/2 wavelength, and adjacent ones have opposite polarities. Electrostrictive elements 1b, 1b, 1b...
Similarly, with a pitch of 1/2 wavelength, adjacent ones have opposite polarities. Also, the electrostrictive elements 1a, 1b
Although not shown, electrode films are provided on each of the front and back surfaces of the electrostrictive elements 1a and 1b, so that an alternating current voltage can be applied to each of the electrostrictive elements 1a and 1b. With the vibration wave motor having such a configuration, an AC voltage of VoSinωT is applied to one group of electrostrictive elements 1a, and an AC voltage of VoCosωT is applied to the other group of electrostrictive elements 1b. Therefore, each electrostrictive element undergoes stretching and contraction vibrations by applying alternating current voltages in which the polarities of adjacent elements are opposite to each other and the two groups are out of phase by 90 degrees. This vibration is transmitted to the vibrating body 2, which bends and vibrates in accordance with the arrangement pitch of the electrostrictive elements 1a and 1b. When the vibrating body 2 protrudes at the position of every other electrostrictive element, the position of every other electrostrictive element retracts. On the other hand, as mentioned above, the electrostrictive element 1a is 1/4 of the electrostrictive element 1b.
Bending vibration progresses because the wavelength is shifted.
While the alternating current voltage is applied, vibrations are excited one after another and propagate through the vibrating body 2 as progressive bending vibration waves. The progress state of the waves at this time is shown in Figure 2 a, b, c,
It is shown in d. Now, the progressive bending vibration wave is the arrow.
Suppose it moves in the X ₁ direction. If O is the central plane of the vibrating body in a stationary state, then in the vibrating state it will be in the state shown by the chain line, and the stress due to bending is concentrated on this neutral plane 6. Looking at the cross section 7 ₁ perpendicular to the neutral plane 6, no stress is applied to the intersection line 5 ₁ of these two surfaces, and the cross section only vibrates vertically. At the same time, the cross section 7 ₁ is pendulum vibrating left and right about the intersection line 5 ₁ .
Similarly, the cross section 7 ₂ or 7 ₃ also vibrates in a pendulum manner to the left or right around the intersection line 5 ₂ or 5 ₃ . In the state shown in FIG. 5A, a point _P1 on the intersection line between the cross section ₇₁ and the surface of the vibrating body 2 on the movable body 3 side is the right dead center of left-right vibration, and is only moving upward. In this pendulum vibration, when the intersection line 5 ₁ , 5 ₂ or 5 ₃ is on the positive side of the wave (when it is above the center plane O), stress is applied to the left (in the opposite direction to the wave traveling direction X ₁ ), and the wave On the negative side (also on the lower side) stress is applied in the right direction. That is, in the figure a, when the intersection line 5 ₂ and the cross section 7 ₂ are in the former state, stress is applied to the point P ₂ in the direction of the arrow. When the intersection line 5 ₃ and cross section 7 ₃ are the latter, the point
At P ₃ , stress is applied in the direction of the arrow. As the wave progresses, b
As shown in , when the intersection line 5 ₁ comes to the positive side of the wave, point P ₁ moves to the left and at the same time moves upward. At c, point _P1 moves only to the left at the top dead center of vertical vibration. At point d, point _P1 moves leftward and downward. The wave further advances, moving rightward and downward, moving rightward and upward, and then returning to state a. When this series of motions is combined, point P ₁ moves in a spheroidal motion. On the other hand, the movable body 3 is in pressure contact with the movable body 2, and as shown in FIG.
The spheroidal motion of point P ₁ on the vibrating body 2 moves the moving body 3
X Frictionally driven in _two directions. Points P ₂ , P ₃ and all other points on the vibrating body 2 are the same as the point P ₁ on the moving body 3.
is friction driven. In the vibration wave motor driven in this way,
It is efficiently driven when the vibration is in a resonant state. The resonance frequency is determined by the dimensions and temperature of the electrostrictive element/vibrating body, the contact pressure of the moving body, etc. Therefore, in the past, for example, the vibration frequency of the vibrating body was detected by a sensor and fed to the oscillation circuit of the drive voltage.
The drive voltage frequency is controlled to the resonance frequency. However, with this indirect control method that involves sensors, etc., there is a delay in response speed and it takes time for the resonant frequency to oscillate, during which time different frequencies may be superimposed and cause "beating". , control tends to be inaccurate. As a result, not only is the noise generated, but the drive efficiency is also poor. Furthermore, the sensor and its signal processing circuit complicate the component structure and drive circuit structure of the motor, which becomes an obstacle to lowering production costs. The present invention was made in view of the above situation, and it is an object of the present invention to provide a drive circuit suitable for a vibration wave motor that is noiseless, has good drive efficiency, and can be produced at low cost. be. The present invention to achieve this objective includes the following: control circuit 1a, R ₁ , R ₂ , R ₃ , OP ₁ ; Z ₁₂ , Z ₁₃ ,
A vibration wave motor drive device having Z ₁₄ , Z ₁₅ , Z ₁₆ , and OP ₁ , in which the vibration wave motor includes a vibrating body 2 and vibrators serving as electro-mechanical energy conversion elements 1a and 1b that excite the vibrating body 2. 2 and an object 3 that moves relative to the vibrator, the control circuit 1a, R ₁ , R ₂ , R ₃ , OP ₁ ; Z ₁₂ , Z ₁₃ ,
Z ₁₄ , Z ₁₅ , Z ₁₆ , OP ₁ is the oscillator 1a, R ₁ , R ₂ , R ₃ ,
OP ₁ ; Z ₁₂ , Z ₁₃ , Z ₁₄ , Z ₁₅ , Z ₁₆ , OP ₁ , and the electro-mechanical energy conversion elements 1a, 1 with oscillation output
Oscillator 1a, R ₁ , R ₂ , R ₃ , OP ₁ ; Z ₁₂ , Z ₁₃ ,
Z ₁₄ , Z ₁₅ , Z ₁₆ , OP ₁ has the electro-mechanical energy conversion element 1a connected to one piece, and the impedance circuit R ₁ , R ₂ , R ₃ ; Z ₁₂ , Z ₁₃ , Z ₁₄ , Z Bridge circuit 1a connecting ₁₅ , R ₁ , R ₂ , R ₃ ,; Z ₁₂ , Z ₁₃ ,
Z ₁₄ , Z ₁₅ and bridge circuit 1a, R ₁ , R ₂ , R ₃ ,;
It has an amplification circuit OP ₁ that applies the outputs of Z ₁₂ , Z ₁₃ , Z ₁₄ , and Z ₁₅ between the input terminals, and the output of the amplification circuit OP ₁ is connected to the bridge circuit 1a, R ₁ , R ₂ , R ₃ , ;Z ₁₂ , Z ₁₃ , Z ₁₄ ,
_Z15 , and the output of the amplification circuit _OP1 is given to the electro-mechanical energy conversion elements 1a and 1b.
It is an object of the present invention to provide a driving device for a vibration wave motor that excites a vibrating body 2. The embodiments shown in the drawings will be described in detail below to clarify the structure of the present invention. FIG. 3 shows a drive circuit to which the present invention is applied. In the figure, 10 is a voltage power source, 11 is an oscillation section (oscillator), and 12 is a 90° phase section. OP
1, OP2 is an operational amplifier, R1 to R4 are resistors, C
1 is a capacitor, 1a and 1b are the electrostrictive elements described above, and the resistors _R1 to _R3 and the electrostrictive element 1a constitute a bridge circuit. In the oscillator 11, the +input terminal voltage V+ of the operational amplifier OP1 is connected to the operational amplifier OP1 by resistors R2 and R3.
The value obtained by dividing the output voltage Vout of OP1 is V+={R3/(R2+R3)}・Vout...(1). Similarly, the -input terminal voltage V- of the operational amplifier OP1 is divided by the resistor R1 and the impedance z of the electrostrictive element 1a: V-={z/(z+R1)}・Vout...(2) . The impedance z of the electrostrictive element is the vibration frequency f
The characteristics are shown in FIG. fr is the resonant frequency and fa is the anti-resonant frequency.
Now, if we differentiate the above equation (2) with respect to the frequency f, we get dv-/df=dz-/df・R1/(z+R1) ² ...(3) Therefore, the potential difference between the input terminal voltages Vin=(V+)-
(V-) increases or decreases as shown in the table below as the frequency f changes.

[Table] As can be seen from this table, the input potential difference Vin reaches its maximum value when the resonance frequency fr of the electrostrictive element is reached. Therefore, resistors R1 to R3 that satisfy the above relationship are determined. Note that the Q at that time becomes A ₀ ·Q ₀ , where Q ₀ is the Q of the electrostrictive element (A ₀ is the amplification degree of the operational amplifier OP1). In the 90° phase shifter 12, the operational amplifier OP2 and the resistor R
Integrating circuit with 4 and capacitor C, operational amplifier
The phase of the output frequency voltage of OP1 is delayed by 90° and applied to the electrostrictive element 1b. FIG. 5 is a block diagram showing a circuit of another embodiment. In the figure, only the oscillation section is shown, and the phase shift section is omitted to see if it can be constructed in the same manner as in the previous example. In this embodiment, various modifications can be made by forming blocks z13 to z16 into various impedance circuits. Each modification example is listed below. Example 1 Block z14 is an electrostrictive element to be resonated, blocks z12, z13, and z15 are resistors, and block z16 is shot. Example 2 Block z12 is an electrostrictive element to be resonated, and block z13 is a series inductance L1 and capacitor C2 shown in FIG. 6a. At this time, 2πfr=1/L1·C2. block z1
4.z15 is a resistor, and block z16 is also a parallel inductance L1 and capacitor C2 shown in Figure 6a.
Make it. At this time, the apparent amplification degree of the operational amplifier OP1 becomes A ₀ at the resonance frequency fr. As the impedance of the block z16 increases as it moves away from the resonant frequency fr, the feedback voltage at the input terminal of the operational amplifier OP1 decreases, so that the degree of amplification decreases. This suppresses oscillation at resonance points far from the vicinity of the preset resonance frequency fr. Since the impedance of block z13 also decreases near the resonance frequency fr, the voltage applied to block 12, which is an electrostrictive element, is
It can be raised until it corresponds to the maximum output of OP1. Example 3 Block z12 is connected in parallel with inductor L3, capacitor C4 and electrostrictive element 1a as shown in Figure 6a.
Make it. At this time, 2πfr=1/L3·C4.
Resist blocks z13 to z15, block z16
to shoot. At resonance frequency fr, block z1
The impedance at point 2 is maximum and decreases as the distance increases. As a result, voltage is applied only near the resonance frequency fr. As explained above, since the drive circuit to which the present invention is applied oscillates at the resonant frequency of the electrostrictive element, the vibration wave motor driven by this circuit can prevent noise and improve drive efficiency. Moreover, since it does not require sensors or the like, it can be produced at low cost.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the main parts of a vibration wave motor, Figure 2
Figure 3 is a diagram explaining the driving principle of a vibration wave motor.
The figure is a drive circuit diagram of an embodiment to which the present invention is applied.
The figure is a characteristic diagram thereof, and FIGS. 5 and 6 are circuit diagrams of other embodiments. 1a, 1b...electrostrictive element (electricity-energy conversion element), _R1 , _R2 , _R3 ...resistance, OP1...amplifier circuit, ₂ ...vibrator, _Z12 , _Z13 , _Z14 , Z ₁₅ , Z ₁₆ ...
Impedance circuit, 11... oscillation section (oscillator).

Claims (1)

[Claims] 1. Control circuit 1a, R ₁ , R ₂ , R ₃ , OP ₁ ; Z ₁₂ ,
This is a vibration wave motor drive device having Z ₁₃ , Z ₁₄ , Z ₁₅ , Z ₁₆ , and OP ₁ , and the vibration wave motor includes a vibrating body 2 and electro-mechanical energy conversion elements 1a and 1b that excite it. A control circuit 1a, _R 1 , R ₂ , R ₃ , OP ₁ ; Z ₁₂ , Z ₁₃ ,
Z ₁₄ , Z ₁₅ , Z ₁₆ , OP ₁ is the oscillator 1a, R ₁ , R ₂ , R ₃ ,
OP ₁ ; Z ₁₂ , Z ₁₃ , Z ₁₄ , Z ₁₅ , Z ₁₆ , OP ₁ , and the electro-mechanical energy conversion elements 1a, 1 with oscillation output
Oscillator 1a, R ₁ , R ₂ , R ₃ , OP ₁ ; Z ₁₂ , Z ₁₃ ,
Z ₁₄ , Z ₁₅ , Z ₁₆ , OP ₁ has the electro-mechanical energy conversion element 1a connected to one piece, and the impedance circuit R ₁ , R ₂ , R ₃ ; Z ₁₂ , Z ₁₃ , Z ₁₄ , Z Bridge circuit 1a connecting ₁₅ , R ₁ , R ₂ , R ₃ ,; Z ₁₂ , Z ₁₃ ,
Z ₁₄ , Z ₁₅ and bridge circuit 1a, R ₁ , R ₂ , R ₃ ,;
It has an amplification circuit OP ₁ that applies the outputs of Z ₁₂ , Z ₁₃ , Z ₁₄ , and Z ₁₅ between the input terminals, and the output of the amplification circuit OP ₁ is connected to the bridge circuit 1a, R ₁ , R ₂ , R ₃ , ;Z ₁₂ , Z ₁₃ , Z ₁₄ ,
_Z15 , and the output of the amplification circuit _OP1 is given to the electro-mechanical energy conversion elements 1a and 1b.
A vibration wave motor drive device that excites the vibrating body 2.