JPS60182368A - Piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To permit the sufficient vibration of a vibration element by making the wave shape of the voltage applied into the vibration element into trapezoidal or triangular pulse wave form in which each of the starting-up part and the starting-down part has a constant gradient. CONSTITUTION:A piezoelectric vibrator is used for the pressing part of a liquid, gas or powder pump. The vibration element of the piezoelectric vibrator is constituted of a unimorph piezoelectric vibration element 1. The applied-voltage control circuit for the vibration element 1 receives a certain amount of electric current from a transistor Tr1 through a full-wave rectifying circuit 3 and a constant-current power-source circuit 4 from an a.c. power source 2. A square wave is obtained from the first arithmetic amplifier CI1. The integration wave of the square wave is outputted from the second arithmetic amplifier CI2. The integration wave is set according to starting-up time T2 and the starting-down time T1 according to the capacity value of a condenser C3 and controls a transistor Tr2. The vibration element 1 is driven-controlled by the operation of the transistor Tr2.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a piezoelectric vibrator that directly converts electricity into mechanical vibration, and which uses a piezoelectric vibrator made of a piezoelectric material and an electrode bonded together. This invention relates to a piezoelectric vibrating device that can be used in pressurizing parts of liquid, gas, and powder pumps and other vibrating parts.

<Prior art> Conventionally, pumps for liquid fuel use electric motors or solenoids to operate impellers, pistons, or plungers, and their rotational or reciprocating motion applies centrifugal force to the liquid fuel and discharges it, or pumps the liquid into a cylinder. It had a structure that discharged water by expanding and contracting the internal volume. However, in this conventional pump, the impeller, piston, plunger, etc. that directly act on the liquid fuel move by themselves even when an electric signal is applied.
The impeller and piston receive the rotational motion of the electric motor through a transmission shaft, and the plunger performs its action using the magnetic field (electromagnetic force) generated by the current flowing through the solenoid. This led to an increase in the size of the pump itself and a complicated internal structure.

<Prior Art> In view of the above points, the applicant of the present application has simplified the structure by using a unimorph vibrator that directly converts electrical energy into vibration, which is a reciprocating motion, in the pressurizing part of the pump. A patent application for a pump that can be made smaller has already been filed in 1987-753.
It was proposed in issue 81.

According to the above-mentioned prior art, the following effects can be expected.

(a) By using a unimorph resonator, the function and structure are simplified, and miniaturization becomes possible.

(b) The number of functional parts is reduced, and the cumulative influence of shape accuracy of each part is reduced, so high quality can be expected.

(c) The conventional intermediate transmission mechanism can be omitted, and loss in this mechanism can be eliminated, resulting in high efficiency.

(d) It is inexpensive in terms of cost.

(e) Since there is no reciprocating movement, there are no quality problems due to wear and tear.

(f) The discharge amount is controlled linearly depending on the voltage level.

However, the applied voltage control circuit for a vibrator in the prior art has a phenomenon in which only a loud noise is generated and the ejection ability is almost lost. This is because the vibrator is like a capacitor, and its oscillating current is proportional to the voltage differential value.If the applied voltage is a square pulse, the vibrator has enough current to vibrate (distort) it. This is thought to be due to the fact that it does not enter.

<Purpose> Therefore, the present invention aims to provide a piezoelectric vibrator that can increase the amount of distortion by feeding a sufficient current into a piezoelectric vibrator and reduce its operating noise.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2. The present invention uses a piezoelectric ceramic thin plate as a piezoelectric material and a metal as an electrode in order to directly convert electricity into mechanical vibration. In a piezoelectric vibrating device having a unimorph piezoelectric vibrator 1 made of a thin plate made of unimorph, the voltage waveform applied to the vibrator 1 is shaped into a trapezoidal pulse waveform whose rising and falling parts have a constant slope. An applied voltage control circuit is provided to control the voltage.

That is, in one embodiment of the applied voltage control circuit interposed between the vibrator 1 and the AC power supply 2 shown in FIG. 1, 3 is a full-wave rectifier circuit, 4 is a constant current source circuit, and a smoothing capacitor C1, bias resistor R1, and Zener diode D1
and a first transistor Tr1, and since a constant voltage is input to the base of the transistor Trl, a constant current flows between the collector and emitter of the transistor Trl.

IC] is the first operational amplifier (hereinafter referred to as the first operational amplifier) for generating the square wave shown in Fig. 2(a) as an output signal, and R2, R3, R4, and R7 are bias resistors for operating the operational amplifier ICI. , C2 is a capacitor for determining the pulse width of the square wave, R5 and R6 are also resistors, T')2. D3
are also diodes, and in the circuit configured with these, the voltage appearing across the capacitor C2 is:
It increases with time with time constant R5・C2, and time constant R
6.C2, the pulse width W of the output voltage waveform of the operational amplifier 2C1 in FIG. 2(a) is controlled by R5.C2, and the pulse separation S is controlled by R6.C2.

Next, IC2 is the second operational amplifier that generates the integral wave of the square wave as an output signal, R8 is its input resistance, C3 is the capacitor for feedback impedance, R1 ( ) is also a resistor, and R9 is the operational amplifier C2. This is a resistor for offset compensation, and the circuit made up of these integrates the rectangular pulse shown in Figure 2 (a) and outputs it at point B on the output side as shown in Figure 2 (G). A pulse is obtained which is an integral waveform with a time constant C3·R10.

Next, R,1,1 is an input coupling resistor for the second transistor Tr2, and C4 is also a capacitor. When the input base current of the transistor Tr2 is zero, the transistor Tr2 is Off"'F, and the transistor Tr2 is Off"'F.
The collector-emitter is open, but when the input base current enters, the transistor Tr2 is turned on and the current is shunted.

Assuming that a constant voltage is now applied between resistors R12 and R13, the same input voltage is applied to the oscillator when transistor Tr2 is OFF, and the input base current of transistor Tr2 has the waveform shown in Fig. 2(b). As the voltage increases, the amplified current shunted to the transistor Tr2 increases, and the voltage at the 0 point on the collector side gradually decreases.
As the input base current of transistor Tr2 decreases according to the waveform voltage, the amplification current shunted to transistor Tr2 decreases, and the voltage at point C on the collector side gradually decreases.
Garu.

Therefore, when the voltage waveform at point B is as shown in FIG. 2(1), the voltage waveform at point C is like the trapezoidal pulse shown in FIG. 2(c).

In addition, in Section 2, the rise time T2 and fall time T1 of the trapezoidal pulse, which is the voltage waveform applied to the vibrator 1, can be set by the capacitance value of the capacitor C3, and the frequency of the trapezoidal pulse can be changed by changing the variable resistor R6. By doing so, you can change it to the desired value.

Since the resonator 1 is like a capacitor, the resonator 1 has a falling time T1 of the trapezoidal pulse shown in FIG. 2(c).
A current corresponding to T2 and its slope flows, and then a current corresponding to T2 and its slope flows. Can these both be regarded as constant currents? The current continues to flow for a certain period of time T1, T2, and this phenomenon is relatively gentle, so the piezoelectric ceramic thin plate of the vibrator 1 also responds sufficiently and vibrates, making little noise.

Incidentally, the opening T2 at the rising edge of the trapezoidal pulse and the opening T1 at the falling edge of the trapezoidal pulse are set to 0.8 m5ec or more, respectively, in order to send sufficient current to the vibrator 1.

In this example, the piezoelectric ceramic thin plate is lead porcelain based on fluorophore titanate, and its thickness is 0.6IllIl+.
The diameter of the disk is 28 + 11111, the thin metal plate is made of stainless steel, the thickness is (1.4 mtn), and the diameter of the disk is 33 nun.

Further, in the second embodiment, the case where the voltage waveform is a trapezoidal pulse is explained, but it is not necessary to make the absolute values of the slopes of the rising and falling parts the same.

In the present invention, it is of course possible to obtain the same effect with a triangular pulse whose rising and falling portions have constant slopes and whose duration is 0.8 m5 ec or more.

<Effects> As is clear from the above description, the present invention provides a piezoelectric vibrator having a piezoelectric vibrator that directly converts electricity into mechanical vibration, in which the voltage waveform applied to the vibrator has a rising part and a falling part. An applied voltage control circuit is provided to create a trapezoidal or triangular pulse waveform with a constant slope.

Therefore, according to the present invention, there is an excellent effect that a sufficient current can be sent to the piezoelectric vibrator, which is like a capacitor, to increase the amount of distortion thereof and to reduce the noise of its operation.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, and FIG. 2 (a
), (1)), and (c) are A and B in Figure 1, respectively.
, is a diagram showing the voltage waveform at point C. 1: Vibrator, 2: AC power supply, ICI, IC2: Operational amplifier, R1-R13: Resistor, C1-C4: Capacitor, D
l-D3: diode, Trl, Tr2:) transistor. Application filed Sharp Corporation Agent Tsunehisa Nakamura-8=

Claims (1)

[Claims] In a piezoelectric vibrator having a piezoelectric vibrator that directly converts electricity into mechanical vibration, the voltage waveform applied to the vibrator is
1. A piezoelectric vibrating device comprising an applied voltage control circuit for forming a trapezoidal pulse waveform or a triangular pulse waveform in which a rising portion and a falling portion have a constant slope.