JPH0561873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drive circuit that switches the polarity of a power supply voltage higher than a logic control voltage to largely displace an electrostrictive vibration device in both directions with low power.

[Prior art]

Piezoelectric materials such as lead zirconate titanate (PZT), which change shape when voltage is applied, can be made into thin plates, attached with electrodes, and then driven by applying voltage to several sheets. It can be used as a component (actuator).

FIGS. 1a to 1c are schematic diagrams showing the conventional structure of a bimorph type electrostrictive vibrator made of two pieces laminated together. 1st
Figure a shows a pair of electrostrictive plates 1 and 2 with electrodes on both sides.
includes a bimorph type electrostrictive vibrator 30 with a same-polarization structure and its drive circuit 50, which are connected via a central electrode 4 so that the polarization directions A are the same, and FIGS. 1b and 1c show the polarization directions. It includes a bimorph type electrostrictive vibrator 31 having a polarization opposing structure in which B and C are joined so as to face each other, and a driving circuit thereof. In the same figure,
3 and 5 are electrodes, 4 is a center electrode, 6 is an electrostrictive vibrator support section, and E is a power source. 60, 61, and 62 are circuits that focus the electrodes so as to provide a two-terminal input for applying voltage to each electrostrictive plate of the electrostrictive vibrator;
It is called a drive input circuit. In addition, the electrostrictive vibrator 30, 3
1 and a drive input circuit 0, 61 or 62 is called an electrostrictive vibration device 100, 101 or 102.

First, the operation shown in FIG. 1a will be explained. When a voltage is applied to the electrodes 3, 5 and the center electrode 4 by the power source E, an electric field is applied from the electrode 3 to the center electrode 4, and from the electrode 5 to the center electrode 4.
is generated from the central electrode 4. Therefore, electrostrictive plate 1
Then, an electric field is applied in the same direction as the polarization direction A, and a stress that tends to contract as shown by arrow D is generated inside the electrostrictive plate 1. On the other hand, in the electrostrictive plate 2, the electric field is in the polarization direction A.
Since the stress is applied in the opposite direction, a stress that tends to expand as shown by arrow E is generated inside the electrostrictive plate 2. Due to the respective stresses generated inside the electrostrictive plates 1 and 2, the tip of the electrostrictive vibrator 30 is displaced upward in the direction of arrow F using the support portion 6 as a fulcrum. next,
If the switch SW is reversely turned on and the circuit is shorted, the charge will be discharged and 30 will be restored.

The operation of FIG. 1b is similarly explained. That is, when a voltage is applied as shown in the figure, the electrostrictive plate 1 contracts and the electrostrictive plate 2' expands, so that the tip of the electrostrictive vibrator 31 is displaced upward as indicated by arrow G.

Both Figures 1a and 1b can be said to be efficient circuits in that a single power supply applies an electric field to each of a pair of electrostrictive plates to generate stress, but the voltage is increased to increase the amount of operating displacement. There is a big drawback in this case. That is, when a voltage is applied to the electrostrictive plates 1, 2, and 2' in the same direction as the polarization direction, the polarization characteristics will deteriorate unless dielectric breakdown occurs even if the voltage is increased.
However, if a voltage is applied in the opposite direction to the polarization direction, the polarization characteristics deteriorate and depolarize at a predetermined voltage lower than the dielectric breakdown voltage (this voltage is called the polarization deterioration voltage). . Furthermore, when the voltage is increased, the polarization is destroyed and the electrostrictive effect is lost. Therefore, since the upper limit of the voltage v of the power source E is limited under the condition that the polarization characteristics of the reverse biased electrostrictive plate do not change, it is difficult to increase the amount of displacement in the configurations shown in Fig. 1 a and b. Ta.

FIG. 1c shows a circuit configuration improved so that a high voltage can be applied. In this circuit, the anodes of a pair of diodes D1 and D2 are coupled together, this coupling point is connected to the central electrode 4, and each cathode is connected to the electrodes 3 and 5, respectively. Explain the operation. The charging current flows as indicated by the arrow I1, and the electrostrictive plate 1 is charged as shown in the figure. The direction of the electric field generated by this charging is the same as the polarization direction H. On the other hand, since no current flows through the electrostrictive plate 2', the electrostrictive plate 2' is not charged and therefore no electric field is applied to it.
Therefore, this electrostrictive vibration device 102 has an electrostrictive plate 1
high voltage can be applied within a range that does not cause dielectric breakdown,
Therefore, a large amount of displacement can be obtained. However, in this configuration, the electrostrictive plate 2' not only does not contribute to displacement at all, but also has the drawback that the displacing force of the electrostrictive plate 1 can be prevented due to its spring property.

Next, since electrostrictive vibrators generally have hysteresis characteristics, when a voltage is applied in only one direction as in the conventional example shown in Figure 1 a to c, the charge is discharged upon recovery. However, the displacement may not return completely, which has the disadvantage that the actual amount of displacement decreases. In order to solve this problem and obtain a large displacement by displacing it in the opposite direction, a polarity switching switch 70 is provided between the power supply circuit and the electrostrictive vibration device 100 as shown in FIG. 2, and the power supply voltage is switched. is considered.

When the voltage is high, conventional circuit components for switching polarity include electromagnetic relays and transistors, but these are all controlled by current and increase power consumption, so they are difficult to drive electrostrictive vibration devices. It had some drawbacks that made it unsuitable. That is,
Although the electrostrictive vibrator itself operates with extremely low power, conventional switching circuits consume a large amount of power to maintain the state, making it difficult to drive with low power.

Furthermore, the circuit shown in FIG. 2 has the disadvantage that it wastes power because it is necessary to cancel the stored charge using a power source when switching the polarity. That is, in FIG.
If the capacitance at 0 is C and the voltage at the time of displacement is V, the energy stored in the electrostrictive vibration device 100 is 1/2CV ² . When changing the polarity switch 70 from this state to reverse displacement, the power source E
Since it is necessary to supply an opposite electric charge to the electrostrictive vibration device 100 so as to cancel out the electric charge charged thereon, and to further charge the electrostrictive vibration device 100 in the opposite direction, the required energy is ^CV2 . Therefore, in repetitive operation, 2CV ² per cycle
energy is required. In this way, in conventional drive circuits, it is necessary to cancel the charged charges with the charges from the power source E, which increases power consumption.
In addition, since discharging and charging are performed from the power source each time the device is operated, the time constant becomes long, resulting in slow operation.

FIG. 3 is a schematic configuration diagram of a laminated electrostrictive vibrator 103 that uses a laminated electrostrictive vibrator 32 in which several tens to hundreds of electrostrictive plates 8a are joined so that their polarization directions are alternate. be. When a positive voltage is applied to the drive terminal 81 and a negative voltage is applied to the drive terminal 82, a voltage is applied to each electrostrictive plate 80 in the polarization direction and expands in the thickness direction. Although the increase in the thickness of a single electrostrictive plate is small, by making it a laminated plate, a displacement of about several tens to 100 μm can be obtained.

In the laminated type, voltage is applied to each electrostrictive plate 80 in the same direction, so a high voltage is often applied in the same direction as the polarization direction (direction of arrow I) to increase displacement. However, when a high voltage is applied, the effect of hysteresis increases as in the case of the bimorph type.

FIG. 4 is a diagram showing an example of applied voltage displacement characteristics. When voltage is applied in only one direction, the amount of displacement decreases due to hysteresis. In order to prevent this, the polarity of the power source may be changed and the polarity may be reversed as shown by the thick solid line in FIG. However, if the high voltage is switched as is, the high voltage will be applied to each electrode plate in the opposite direction to the polarization direction, and the polarization will be destroyed. Therefore, when switching the voltage in the opposite direction, it is necessary to lower the power supply voltage below the polarization deterioration voltage, but such a circuit has not been known so far.

To summarize the above, until now, an efficient drive input circuit that can apply the high voltage necessary to significantly change the electrostrictive vibrator has not been realized.

A capacitive load voltage switching circuit that can switch high voltage with low power, change the voltage depending on polarity as necessary, and maintain the switched state with low power has not been realized.

There were problems such as. For this reason, the conventional electrostrictive vibrator has a drawback that the amount of displacement per unit length is small, and if an attempt is made to compensate for this, the shape becomes large. In addition, the larger the size, the slower the operation, the higher the cost, and the more easily broken. Although electrostrictive vibrators are expected to be small, low-power actuators, their widespread use has been hindered by the drawbacks mentioned above. In particular, it has been considered difficult to put it into practical use in money handling devices, relays, optical switches, etc. because the amount of displacement is not sufficient.

[Summary of the invention]

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide an electrostrictive vibrator drive circuit that can largely displace an electrostrictive vibrator with low power.

In order to achieve such an object, the present invention provides an electrostrictive vibrator comprising an electrostrictive vibrator formed by stacking two or more ferroelectric electrostrictive plates each having electrodes on both sides, and a drive input circuit having two drive terminals. The electrostrictive vibrator is returned to its previous state by applying a voltage to the strain vibrating device by switching the polarity from the power supply circuit, discharging the electric charge stored in the electrostrictive vibrating device, and then recharging the electrostrictive vibrating device. In a drive circuit that displaces the switch in the opposite direction, a power supply voltage higher than the logic control voltage can be turned on and off in order to switch the polarity, and the ON state of the switch can be turned on or off by pulsing the control current or applying the control voltage, consuming almost no power. Connect four semiconductor switches of PNPN element structure or FET element structure that can be held without moving in a bridge shape, and connect two parallel switches in the bridge.
By inverting the drive logic of the two parallel and diagonal switches and driving them, when one of the parallel or diagonal switch circuits is on, the other is controlled to be off.

The present invention will be described in detail below along with examples.

〔Example〕

FIG. 5 is a circuit diagram showing the basic idea of the present invention, including a polarity changeover switch circuit using a PNPN switch (thyristor) photocoupler. In the same figure, PN1 to PN4 are PNPN switches,
A bridge circuit 71 is formed. That is, the common connection terminal K1 of a set of PNPN switches PN1 and PN3, whose anodes are commonly connected, is the anode of the DC power supply circuit, and the common connection terminal K1 of a set of PNPN switches PN2, PN4, whose cathodes are commonly connected, is connected to the anode of the DC power supply circuit. Connect terminal K2 to the cathode of the DC power supply circuit,
Connect the cathode of PNPN switch PN1 and the anode of PNPN switch PN4, and
Connect PNPN switch PN3 to one drive terminal of 00.
The cathode of the PNPN switch PN2 is connected to the anode of the PNPN switch PN2, and is connected to the other drive terminal of the electrostrictive vibration device. ZD5 is a constant voltage diode, which has the characteristic of operating at a voltage slightly higher than the voltage v of the DC power supply E. CRD1 and CRD2 are constant current diodes, C ₁ and _CA are capacitors, and R ₁₁ and R ₁₂ are resistors. Further, although the electrostrictive vibrating device 100 is the same as that shown in FIG. 1a, other electrostrictive vibrating devices such as those shown in FIG. good.

LED1 to LED4 are each PNPN switch
Light emitting diodes for irradiating and igniting PN1 to PN4, SW12 and SW34 are FETs, respectively.
A switch that does not require control power and has an element structure such as MOS or CMOS, INV is an inverter that inverts the logic input level, R _H is a high resistance, SW5 is a changeover control switch, and PUL is as shown in the waveform diagram in Figure 6. , turn on and off the voltage of the logic control voltage Eg,
This is a pulse oscillation circuit that repeatedly generates intermittent pulse voltages, and by these, the logic control circuit 7
2 are configured.

Next, the operation will be explained. When the power switch SW is turned on, a constant current is supplied to the capacitor C1 via the constant current diode CRD1, and the capacitor C1 is charged.
Further, the pulse oscillation circuit PUL starts oscillating.
When the changeover control switch SW5 is as shown in the figure, the switch SW12 is in the on state, while the switch SW34 is in the on state.
is in the off state, and the light emitting diodes LED1 and
Only the LED 2 is driven by the intermittent pulse voltage generated by the pulse oscillation circuit PUL to emit light.
Since the PNPN switches PN1 and PN2 are turned on when receiving the first pulsed light, the electrostrictive vibrator 10
0, a constant current flows through the constant current diode CRD2. When the current begins to flow, the switches PN1 and PN2 having the PNPN element structure continue to be energized until the electrostrictive vibrator 100 is charged even after the pulsed light for the self-holding function has left. When the electrostrictive vibration device 100 is charged and current stops flowing, the PNPN switches PN1 and PN2 are restored.
In this way, the electrostrictive vibrator 1 is originally
Although it is possible to drive 00, continuous pulse driving is preferable for the following reasons. That is, since the electrostrictive vibrator has hysteresis characteristics, the capacitance may change during operation. For this reason, sufficient charge may not be supplied to the pulse electrostrictive vibration device 100 at one time, and a displacement commensurate with the power supply voltage may not be obtained. In addition, there is a slight leak at the electrode end of the electrostrictive vibrator, so even if it is fully charged,
Over a long period of time, discharge may occur and the displacement may return. In particular, in vibrators whose electrode ends are not sufficiently insulated at the time of manufacture, this effect increases as humidity increases. In order to solve this problem, in this embodiment, the pulse oscillation circuit PUL continuously supplies a pulse current.

Regarding the pulse interval τ ₂ , it is preferable to make it longer in order to reduce the control power, but if it becomes too long, a slight return of displacement will occur for the reason mentioned above, so it is necessary to synchronize with the pulse interval on the displaced side. A slight vibration occurs. 100ms to prevent this
The following are desirable.

On the other hand, if the pulse width is shortened, there will be no minute vibrations and it is suitable for high-speed repetitive operation, but if the pulse width is shorter than the charging time constant, switching switch SW5 at high speed will cause the PNPN switch connected in parallel to
While PN1 and PN2 are held on by the charging current, the diagonally connected PNPN switches PN3 and PN4 may be driven, so that the bridge circuit may be short-circuited. To prevent this, 0.5ms or more is desirable. In this way, the pulse width is preferably 0.5 ms to 100 ms.

The pulse width is determined by the sensitivity of the PNPN switch, but several tens of microseconds is sufficient. Therefore, the duty is 1/50 to 1/10000, and the control power for holding the electrostrictive vibrator can be extremely small.

Next, the smoothing circuit surrounded by the dashed line will be explained. As mentioned above, when the pulse width is increased, the vibrator is slightly displaced on the displacement side, and in order to prevent this, it is necessary to shorten the pulse width to a permissible value or less. As a means, a method of providing a smoothing circuit between the electrostrictive vibration device 100 and the bridge circuit 71 can be considered. The smoothing circuit can be composed of a capacitor C _A and a resistor R _A or a capacitor C _A and a bidirectional constant current diode CRD-A. This principle is that when charging the electrostrictive vibrator 100, the capacitor C _A is also charged at the same time, and the electrostrictive vibrator 100 is charged.
This is to supply charge from the capacitor C _A to compensate for the charging voltage that has decreased due to changes in the capacitance of the capacitor, leakage, etc.

Next, the action of constant current diodes CRD1 and CRD2 will be described. Constant current diode CRD1
is a constant current circuit used in the charging circuit of the capacitor C1, and the constant current diode CRD2 is used in the charging circuit of the electrostrictive vibration device. Both of these can be replaced with resistors R3 and R4, but we will discuss their advantages over resistors. Figure 7 a to f
is a diagram explaining this. When charging is performed through a resistor as shown in FIG. 7a, a large current initially flows (FIG. 7b) and the voltage rises quickly (FIG. 7c). Therefore, the vibrator operates quickly, but as it charges, the current value rapidly decreases exponentially, so the voltage rise also slows down, and the vibrator has the disadvantage that it operates slowly at the most important points where the displacement is large. .

On the other hand, as shown in Figure 7d, the constant current diode
When charging using a CRD, almost the same current as at the beginning continues to flow through the electrostrictive oscillator indicated by the capacity C even as charging progresses (e in the same figure), and the voltage rises at almost the same slope as at the beginning. (F in the same figure), the vibrator is characterized by small and fast speed changes during operation.

The charging and holding operations have been described above, but next we will discuss the switching operations of the switch and the constant voltage diode ZD5.
The effect of this will be explained. When switch SW5 is switched to ground level (GND), switch SW34
is turned on and the switch SW12 is turned off, so that the light emitting diodes LED1 and LED2 stop emitting light, and the photodiodes LED3 and LED4 emit light by the next pulse current supplied from the pulse oscillation circuit PUL. For this reason, PNPN switch PN
3. PN4 fires. In addition, PNPN switch N
1. PN2 is when the pulse period of the pulse oscillation circuit PUL is longer than the charging time constant of the electrostrictive vibration device 100,
As mentioned above, when the PNPN switches PN3 and PN4 are turned on, they are in the off state.
When PNPN switches PN3 and PN4 are turned on,
The electric charge charged in the electrostrictive vibration device 100 is
PNPN switch PN4, constant voltage diode ZD5
(forward direction), the charging current is discharged through the path of the PNPN switch PN3, and then the charging current is transferred from the capacitor _C1 and the power source E to the constant current diode CRD2, the PNPN switch PN3, the electrostrictive vibrator 100, and the PNPN switch.
The current electrostrictive vibration device is charged through the path of PN4.
In this manner, by using the forward characteristics of the constant voltage diode ZD5 to cancel out the charge that has been charged in the electrostrictive oscillation device at the time of switching, unnecessary power consumption can be reduced. FIG. 8 illustrates the current flowing from the power supply circuit of FIG. 5 in order to show this in detail. For simplicity, the smoothing circuit indicated by the dashed line is omitted here. The case where the constant voltage diode ZD5 is not provided is shown in FIGS. 8a and 8b, and the case where the constant voltage diode ZD5 is provided is shown in FIGS. 8c and d. In this way, when the constant voltage diode ZD5 is provided, no electric current is required due to the discharge shown by the diagonal lines in FIG. 8b, so that unnecessary power is omitted. Also, by adding the constant voltage diode ZD5, the charging time is shortened from _T1 to _T2 , which has the advantage of speeding up the operation.

In the above description, the constant voltage diode ZD5 only needs to have forward characteristics. Therefore, a diode may be used instead. Note that the reason for using a constant voltage diode here is that it has the advantage of being able to absorb surge voltage exceeding the power supply voltage when it enters.

In addition, in FIG. 5, by connecting the same circuit as the bridge circuit 71 in parallel to the K1 and K2 terminals, it is possible to operate a plurality of electrostrictive vibration devices using one power source.

FIG. 9 is a circuit diagram showing an embodiment of a 2×2 matrix drive circuit using a photocoupler PNPN switch bridge circuit 71. Note that the minute vibration prevention circuit is omitted in the figure on the premise that the duty of the pulse oscillation circuit PUL is set within a range in which the electrostrictive vibrator does not vibrate minutely. A case in which the intersection point 11 is operated will be briefly explained as an example.

When a logic control voltage is applied to input terminal IN11,
Since a pulse current flows through either the light emitting diodes LED1 and LED2 or the light emitting diodes LED3 and LED4, the corresponding PNPN switch is fired,
The electrostrictive vibration device 100A operates. The same applies to other intersection points.

Next, examples of the present invention will be described. In FIG. 5, a method of separating the gate of the PNPN switch and the logic control circuit using a photocoupler has been explained, but the separation can also be performed using a PN reverse junction.
Figure 10 uses a current-driven PNPN switch to connect the gate circuit and logic control circuit to transistors.
FIG. 2 is a circuit diagram showing an example of separation using a PN reverse junction. In the same figure, PN1' and PN3' are N gate PNPN switches (thyristors), PN2, PN
4 is P gate PNPN switch (thyristor),
R _GA and R _GK are gate/anode resistance and gate/cathode resistance, respectively. Also, Tr12, Tr
34 is an NPN transistor. This embodiment has the same basic configuration as the embodiment shown in FIG. 5, so the explanation will focus on the differences.

The PNPN switch PN1' is fired by applying a gate current I _G1 to the N gate. This gate current is controlled by a logic control circuit 73 that operates with a logic control voltage Eg.
Since the voltage v of the power supply E is applied to the anode and gate of 1', the gate circuit is connected to the logic control circuit 7.
It is necessary to separate it from 3 so that only the gate current can flow. In this embodiment, they are separated by a PN reverse junction of an NPN transistor. The same applies to the PNPN switch PN3'.

Explain the operation. When switch SW5 becomes the state shown in the figure and switch SW12 is turned on, the transistor
Tr12 receives the base current from the pulse oscillation circuit PUL.
Since I _B1 flows, an amplified current I _G1 flows through collector c. This current is connected to the PNPN switch PN
Since the current flows through the N gate of PN1', the PNPN switch PN1' is turned on. Note that the resistor R8 is a resistor that controls the power source I _G1 to an appropriate value. Also, PNPN
The P gate of switch PN2 has a pulse oscillation circuit.
Since the gate current I _G2 flows directly from PUL as shown in the figure, the PNPN switch PN2 is also fired. on the other hand,
Since the switch SW34 is in the off state, no base current flows through the transistor Tr34, and therefore the voltage v of the power supply E is blocked by the PN reverse junction of the transistor Tr34. Furthermore, since no current flows through the P gate of the PNPN switch PN4, the voltage v of the power source E is blocked by the PN reverse junction (gate junction) of the PNPN switch PN4. When the switch SW5 is switched, the PNPN switches PN1' and PN2 are turned off, and the PNPN switches PN3' and PN4 are turned on. The subsequent operation is the same as the embodiment shown in FIG.

Next, prevention of malfunction of the switch will be explained. The PNPN switch has a voltage that rises quickly,
When a voltage is applied between the anode and cathode, a surge current flows through the gate junction via the junction capacitance, resulting in false firing (this is called the dv/dt characteristic). A voltage with a fast rise is applied mainly during polarity switching, and if this causes false ignition, the bridge circuit 74 will be short-circuited, causing a problem. In order to prevent this, the gate resistance R _GK or R _GA may be lowered, but if it is lowered too much, the gate sensitivity will decrease and the driving power will increase, which is contrary to power saving. Therefore, here, a method of inserting a small capacitance in parallel with the gate resistor is shown in FIGS. 11a and 11b. For example, if a capacitor of about 200PF is used, the impedance will be about 800Ω for a frequency component with a rise of about 1MHz. If the gate resistances R _GX and R _GA are approximately 5 to 50KΩ, the impedance will be less than 1/10.
DV/DT resistance is improved. Furthermore, when operating with a pulse width of approximately 50 μs, 200PF corresponds to an impedance of 8KΩ, so there is little effect on gate sensitivity characteristics. Capacitors C _GK and C _GA are determined based on the gate characteristics of the PNPN switch, but approximately 50 to 500 PF is suitable. Furthermore, as another method for slowing the rise of the power supply voltage, a capacitor C _AK with a small capacitance may be inserted between the anode and the gate. In addition, a circuit for bypassing transient current may be provided at the element structure level to increase the dv/dt tolerance.

It should be noted that among the circuit components of this embodiment, the PNPN switch, transistor, diode, and constant current diode can be fabricated by a bipolar manufacturing process, so they can be integrated into an IC. In addition, the pulse oscillation circuit PUL, inverter INV, and switches SW12 and SW34 are
It can be made into an IC using the CMOS process. Therefore, this embodiment can be configured with two ICs.

FIG. 12 is a circuit diagram showing another embodiment.
The bridge circuit is composed of N-channel FETs, and the gate circuit 75 and logic control circuit 76 are separated by an N-channel enhancement type MOSFET. FET is a normally-on type switch, and when no voltage is applied to the gate, a constant current of several mA flows, and when a negative voltage is applied to the gate with respect to the source electrode, the drain current is gradually controlled, and a constant current of several mA flows. The voltage causes a pinch-off state. Since FET has a constant current of several mA when no voltage is applied to the gate, it is suitable for driving actuators.
Although it has not been used much in the past, in the present invention, the electrostrictive vibration device has a small capacitive load, so it
However, it is fully usable.

Explain the operation. In the N-channel FET, the gate and source are short-circuited with a resistance of several 100K to 1MΩ. When switch SW5 is in the state shown in the figure, the N-channel enhancement type MOSFET
Since voltage Eg is applied to the gates of switches 111 and 112, the switches become conductive. As a result, the gates of the N-channel FETs 121 and 122 are at the ground level, that is, a negative level with respect to the drain and source.
The channel FET is in a pinch-off state. on the other hand,
The gates of FET switches 113 and 114 are at ground level and are therefore in an off state. Therefore, N channel
The constant current I of several mA is applied to FET123 and 124.
1 flows as shown in the figure, and the electrostrictive vibration device 100 operates.

When the switch SW5 is turned on in the opposite direction, the FET switches 111 and 112 are turned off, so a constant current flows through the N-channel FEHs 121 and 122. On the other hand, the FET switches 113 and 114 are turned on, so the N-channel FETs 123 and 112 are turned on. 124 is a pinch-off. As a result, a charging current flows in the direction opposite to I1, and the electrostrictive vibration device is displaced in the opposite direction.

Next, control power consumption will be described. As shown in the figure, when charging the electrostrictive vibration device 100, gate currents such as I2 and I3 flow through the gate resistances Rh of the N-channel FETs 121 and 124, but this current value is 500K to 1MΩ. Extremely small due to high resistance. Furthermore, no current flows after the electrostrictive vibration device 100 is charged. Therefore, after the electrostrictive vibration device operates, the control power required to maintain its state is close to zero. N-channel FET121 or 1
24 can also be replaced with an N-channel depletion type MOSFET having similar characteristics. Both can be made into an IC using the FET process.

Figure 13 shows the N-channel FET121 in Figure 12.
or 124, FET switch 111 or 11
This is an example in which 4 is replaced with a P channel FET.
Note that since the operation is similar to that of the embodiment shown in FIG. 12, a description thereof will be omitted.

Similarly, Fig. 14 shows a static induction type transistor.
An example using SIT and FIG. 15 is an example using a high voltage CMOS analog switch. In the figure, SW _{A to D} are CMOS switches, and CO _{A to D} are gate circuits.

Next, an embodiment of an electrostrictive vibration device driven by the drive circuit of the present invention will be described.

In FIG. 16, an electrostrictive vibrator 30 is formed by joining a pair of electrostrictive plates 1 and 2 with electrodes on both sides via a central electrode 4, and a drive input circuit 63 is connected to the electrostrictive vibrator. Among the electrodes formed on the outside of 30, the cathode of the constant current diode ZD1 is connected to the electrode 3 that is in contact with the + polarization, and the anode of the constant voltage diode ZD2 is connected to the electrode 5 that is in contact with the - polarization. The anode of the voltage diode ZD1 and the cathode of the constant voltage diode ZD2 are connected to the drive terminal 91.
FIG. 2 is a schematic configuration diagram of an electrostrictive vibration device 104 configured by using a central electrode as a drive terminal 92. FIG. Explain the operation. When voltage E is applied between drive terminals 91 and 92, charging current I2 flows as shown in the figure, and voltage E is applied to electrostrictive plate 1 in polarization direction K.
However, the electrostrictive plate 2 has a voltage (E-) opposite to the polarization direction L.
V _ZD2 ) is applied. Here, V _ZD2 is the reverse operating voltage of the voltage regulator diode ZD2. For this reason,
The electrostrictive plates 1 and 2 are distorted as indicated by arrows M and N, respectively, and the electrostrictive vibrator 30 is displaced upward as indicated by arrow O. On the other hand, when voltage E is applied with opposite polarity, that is, the drive terminal 92 is positive and the drive terminal 91 is negative, the voltage E is applied to the electrostrictive plate 2 in the polarization direction L.
A voltage (E-) is applied to the electrostrictive plate 1 opposite to the polarization direction K.
V _ZD1 ) is applied. For this reason, the electrostrictive vibrator 30
is displaced in the direction opposite to arrow O, that is, downward.

In this electrostrictive vibration device 104, (E-V _ZD2 )<(polarization deterioration voltage of electrostrictive plate 2)(E-V _ZD1 )<(electrostrictive plate 1
If the conditions of polarization deterioration voltage) are satisfied, the voltage E becomes
A high voltage can be applied within a range that does not cause dielectric breakdown of the electrostrictive plate 1 or 2. For example, if E is doubled as compared to Fig. 1 a, the electrostrictive plate 1 will receive more than twice the compressive stress, and the electrostrictive plate 2 will have an elongation stress equivalent to that in Fig. 1 a. As a result, the electrostrictive plate 30 is displaced about 1.5 times or more compared to the case shown in FIG. 1a. Furthermore, if the voltage E is increased three times, the electrostrictive plate 30 will similarly be displaced about two to three times as compared to FIG. 1A.

Next, a specific example of this electrostrictive vibration device will be described. The operating displacement amount δ when the power supply voltage is switched and applied to the electrostrictive vibration device 104 made of a certain kind of electrostrictive material based on lead zirconate titanate (PZT) is the first
FIG. 17 shows a comparison with the amount of operational displacement of the electrostrictive vibration device 100 shown in FIG. In the same figure, (time A)
is the operating displacement characteristic of the device 104 of this embodiment, (rotation)
are the characteristics of the device 100 shown in FIG. 1a. When both voltages are low, the displacement δ increases monotonically, but
When the voltage reaches about 60V, the polarization of the electrostrictive plate constituting the electrostrictive vibrator is destroyed in the electrostrictive vibrator 100, and the displacement δ is
decreases rapidly. Since deterioration of polarization begins at about 1/2 of the polarization breakdown voltage, the rated voltage that can be applied to the electrostrictive plate in the opposite polarization direction in this electrostrictive vibration device is about 30V. Therefore, the amount of displacement is about 1 mm. However, in the electrostrictive vibrator 104, the rated voltage V _M can be applied in the reverse polarization direction, and a high voltage can be applied in the forward polarization direction within a range that does not cause dielectric breakdown, so it is also possible to use a power supply voltage of 100 V or more. be. In the experiment
A displacement of about 2mm can be obtained at 60V and about 3mm at 100V.
And there was no deterioration. 60V can be switched with the aforementioned CMOS switch, and 100V can be switched with the aforementioned PNPN switch, etc., so they are voltages that are actually easy to use. In this way, the conventional electrostrictive vibration device 100
It was confirmed that a displacement of 2 to 3 times greater than that of the conventional method can be obtained.

When a voltage is applied in the opposite polarization direction, depending on the electrostrictive plate, the polarization may deteriorate little by little even below the polarization deterioration voltage. This deterioration is much smaller than when applying a voltage higher than the polarization deterioration voltage, but
Over a long period of time, it may decrease by several to 10%.
On the other hand, an electrostrictive plate has the property of recovering deteriorated polarization when a high voltage is applied in the polarization direction. By utilizing such characteristics, when the electrostrictive vibration device 104 using the drive input circuit 63 is vibrated using the drive circuit of the present invention, there is an advantage that deterioration of polarization can be prevented as described below. . That is, the 16th
In the figure, if the electrostrictive plate 2 is left for a long time,
Since voltage is applied in the opposite polarization direction, deterioration may occur. However, when the polarity of the applied voltage is reversed, a high voltage is applied to the electrostrictive plate 2 in the polarization direction L, so that the deterioration of polarization is recovered. In this way, deterioration of polarization can be prevented by alternately displacing (vibrating). The same applies to the electrostrictive plate 1.

In addition, in Fig. 16, the constant voltage diode
ZD1 operating voltage V _ZD1 and constant voltage diode ZD2
The operating voltage V _ZD2 may be changed. In this case, since the voltage applied to each electrostrictive plate can be controlled according to the polarity, the amount of displacement can be changed depending on the direction of displacement.

When a high voltage is applied to the electrostrictive vibrator 30 in a high temperature and high humidity environment, the electrostrictive vibrator 30 may be left unattended at the adjacent electrode edges. This may cause slight vibrations on the displaced side as described above. To prevent this, the electrode edge portion or the entire surface of the electrode may be coated with an insulating resin. Suitable coating materials include polyurethane and Teflon. Among these, polyurethane can be applied at room temperature, but Teflon requires heat treatment. However, when heated above the Curie temperature, the polarization of the electrostrictive plate is destroyed. The following method is effective to solve this problem. First, the electrostrictive vibrator 30 is formed, coated with Teflon, and subjected to heat treatment, and then a high voltage is applied to form polarization. In this method, a high voltage for forming polarization is applied after the insulation treatment, so that polarization can be formed by applying a higher voltage than in a normal method, so the yield is good.

Further, a bidirectional constant voltage limiting element VR may be connected between the drive terminals 1 and 2 in order to absorb surges.

FIG. 18 shows another configuration example based on the same principle as the electrostrictive vibrator shown in FIG. 16. In the same figure, center electrodes 4-1 and 4-2 are connected via an insulating plate 14, the anode of a constant voltage diode ZD2 is connected to the center electrode 4-1, and the anode of a constant voltage diode ZD1 is connected to the center electrode 4-2. The anodes are connected to each other, the cathode of the constant voltage diode ZD1 is connected to the electrode 3, the cathode of the constant voltage diode ZD2 is connected to the electrode 5, and the electrodes 3 and 5 are connected to drive terminals 91 and 92, respectively. terminal 91,
When a voltage E is applied to 92, E is applied to the electrostrictive plate 1 in the polarization direction, and to the electrostrictive plate 2 in the reverse polarization direction (E-V _ZD1 ). When the polarity is reversed, electrostrictive plate 2 has E in the polarization direction, and electrostrictive plate 1 has E in the opposite polarization direction (E-
V _ZD2 ) is applied. The basic operation is the same as that in FIG. 16, so it will be omitted.

FIGS. 19 a to 19 c show an embodiment of an electrostrictive vibration device in which the electrostrictive plates 1 and 2 in FIG. 16 are multilayered. The polarization deterioration voltage of the electrostrictive plate is 30V, the power supply voltage is 60V, and the operating voltage of the constant voltage diode is 60V−.
The case where 30V=30V is shown. In addition, power supply voltage - polarization deterioration voltage < operating voltage of voltage regulator diode
In the range that satisfies V _ZD x, the operating voltage V _ZD1 and
V _ZD2 may be different. The advantage of having multiple layers is that a large force can be obtained even when the same voltage is applied.

FIG. 20 is a schematic configuration diagram showing an example of the configuration of an electrostrictive vibrator using an electrostrictive vibrator 31 having a polarization facing structure. That is, the electrostrictive vibration device 105 uses the outer electrodes 3 and 5 as drive terminals 91 and 92, and the electrodes 3 and 5 have constant voltage diodes ZD3 and ZD4, respectively.
Connect the anode of the constant voltage diode ZD
3. The cathode of each diode is connected to the cathode of ZD4, and the anodes of the diodes are connected to the central electrode 4 in common.

Explain the operation. When voltage E is applied between drive terminals 91 and 92, charging current I5 flows, and electrostrictive plate 1 receives V in the polarization direction (E-V _ZD4 ), and electrostrictive plate 2' receives V in the opposite polarization direction. Voltage _ZD4 is applied. As a result, the electrostrictive plate 1 contracts and the electrostrictive plate 2' stretches, so
The tip of the electrostrictive vibrator 31 is displaced upward as in FIG. 16. When the polarity of the applied voltage is reversed, the electrostrictive plate 2'
is applied in the polarization direction P (E-V _ZD3 ), and a voltage V _ZD3 is applied to the electrostrictive plate 1 in the opposite direction to the polarization direction Q.
expands, and the electrostrictive plate 2' contracts, so its tip is displaced downward.

In this drive input circuit 64, V _ZD4 <(polarization deterioration voltage of electrostrictive plate 2') (E-V _ZD4 ) <(dielectric breakdown voltage of electrostrictive plate 1), V _ZD3 <(polarization deterioration of electrostrictive plate 1). Voltage), (E-V _ZD3 )<(Dielectric breakdown voltage of electrostrictive plate 2') As long as the following conditions are satisfied, the voltage of E can be increased, and therefore a large displacement can be obtained. If we give a specific example and compare it with the conventional one, for example, E=
90V, V _ZD3 = V _ZD4 = (polarization deterioration voltage) = 30V, a voltage of 60V is applied to the electrostrictive plate 1 and a voltage of 30V is applied to the electrostrictive plate 2', so the electrostrictive vibrator 31 In FIG. 1b, the displacement is 1.5 times or more compared to when E=60V, that is, the voltage applied to the electrostrictive plates 1 and 2 is 30V.

Note that, as in the electrostrictive vibrator shown in FIG. 16, deterioration of polarization can be prevented by vertically displacing or vibrating the vibrator.

FIG. 21 is an example of a configuration in which the polarization in FIG. 20 is reversed. The operating principle is the same as that in FIG. 20, and therefore will be omitted.

FIG. 22 shows an embodiment of an electrostrictive vibrating device in which the electrostrictive plates 1 and 2' in FIG. 20 are multilayered.

FIG. 23 is a schematic configuration diagram showing an embodiment of an electrostrictive vibrator using an electrostrictive vibrator 32 having a laminated structure. That is, the drive input circuit 65 of the laminated electrostrictive vibration device 106 connects the cathode of a constant voltage diode ZD6 to the electrode 8 that is in contact with + polarization, and uses the anode of the constant voltage diode ZD6 as a drive terminal 91, which is in contact with - polarization. The electrode 9 is configured as a drive terminal 92.

Explain the operation. When voltage E is applied in the direction of ( ), voltage E is applied to each electrostrictive plate 82 in the polarization direction R.
is applied, the tip of the electrostrictive vibrator 32 extends. Next, when the polarity is reversed and a voltage is applied in the direction of (), a voltage (E-V _ZD6 ) is applied to each electrostrictive plate 82 in the opposite polarization direction, so that the displacement occurs as shown by the thick solid line in Figure 4. do. In this electrostrictive vibration device 106,
E<(breakdown voltage of each electrostrictive plate), (E-V _ZD6 )<
As long as the condition (polarization deterioration voltage of each electrostrictive plate) is satisfied,
E voltage can be increased.

The voltage that can be applied to the electrostrictive plate 82 in the reverse polarization direction is
Although it is quite small compared to the polarization direction, as shown in Figure 4, the rate of change in displacement is high at low applied voltages, so even if the voltage applied in the opposite polarization direction is low, below the deterioration voltage, the effect of hysteresis can be sufficiently prevented. Therefore, compared to the electrostrictive vibration device 103 of FIG. 3 in which no voltage is applied,
Even with the same voltage E, the amount of displacement can be increased by about 30%.

Next, a configuration example of an electrostrictive vibrator of an electrostrictive vibrating device driven by the drive circuit of the present invention will be described. The drive circuit of the present invention switches the polarity of a high voltage DC power supply and applies it to the electrostrictive vibration device to cause the device to vibrate greatly. However, when using the force generated at the tip of the device, , it is not enough to simply have a large amount of displacement; it is necessary to consider displacement and force characteristics. FIG. 24 is a configuration diagram for explaining this, in which a voltage is first applied so that the electrostrictive vibrator 30 is in the state, and when the polarity of this voltage is reversed and the state is changed to The displacement/force characteristics are shown in Figure 25. As can be seen from this characteristic, conversely, a large force is generated at the beginning of the displacement, but as the displacement increases, the force weakens and reaches zero. In other words, it is difficult to obtain pressure near the state of . Therefore, when an electrostrictive vibration device is used in a relay, an optical switch, etc., it is necessary to obtain pressure at the cost of displacement to ensure contact reliability during switching.

FIG. 26 is a schematic diagram showing a configuration example for improving the displacement/force characteristics of the electrostrictive vibration device. In the figure, reference numerals 10 indicate magnetic pieces 11 and 12 provided near the tip of the electrostrictive vibrator 30, which are the reaching points that are displaced to both sides when the electrostrictive vibrator 30 vibrates due to an applied voltage whose polarity has been switched. A fixed permanent magnet is provided near the magnetic piece 10 so as to face the magnetic piece 10. The mechanism consisting of the magnetic piece 10 and the fixed permanent magnets 11 and 12 is a flip-flop mechanism in which the mechanical stability point is either where the magnetic piece 10 and the fixed permanent magnet 11 are in contact, or where the magnetic piece 10 and the fixed permanent magnet 12 are in contact. It is. Further, FIG. 27 is a diagram showing the force at the tip of the electrostrictive vibrator 30, assuming that the force from the state to the state is positive. Explain the operation. In this state, a force as indicated by the broken line is acting on the electrostrictive vibrator 30 due to the attractive force between the magnetic piece 10 and the fixed permanent magnet 11. Here, if the characteristics of the applied voltage are reversed, a force as shown by the dashed-dotted line is applied, resulting in a force as shown by the solid line, and the electrostrictive vibrator 30 moves in the direction A. As the electrostrictive vibrator 30 approaches the state of , the force indicated by the dashed dotted line weakens, but the force does not decrease because the attractive force between the magnetic piece 10 and the fixed permanent magnet 12 increases. In this way, it is possible to obtain a mechanically stable acting force even in the state of .

FIG. 28 shows the effect of shortening the displacement time of the vibrator by the flip-flop mechanism. Since the electrostrictive vibrator 30 has polarization hysteresis characteristics as described above, there is a phenomenon in which the operation suddenly slows down near the final displacement point when vibrating. As shown by the broken line in FIG. 28, as the speed decreases, the operating time T until the final displacement point naturally increases.
Here, when a flip-flop mechanism is used, a force is applied to the tip of the electrostrictive vibrator 30 near the final displacement point, so the operation becomes faster as shown by the solid line, and therefore the operation time becomes shorter.

FIG. 29 shows a flip-flop mechanism using a spring instead of a magnet. In the figure, reference numeral 13 denotes a flip-flop spring that is attached to the tip of the electrostrictive vibrator 30 and generates a force in the direction of F1 in the state of , and in the direction of F2 in the state of . FIG. 30 shows the displacement/force characteristics of the tip of the electrostrictive vibrator 30. Regarding the operation, see the 26th
Since it is similar to the electrostrictive vibrator 30 shown in the figure, the explanation will be omitted.

〔Effect of the invention〕

As explained above, the present invention provides an electrostrictive resonator that includes an electrostrictive vibrator formed by stacking two or more ferroelectric electrostrictive plates each having electrodes on both sides, and a drive input circuit having two drive terminals. The electrostrictive vibrator is returned to its previous state by applying a voltage to the vibrating device by switching the polarity from the power supply circuit, discharging the electric charge stored in the electrostrictive vibrating device, and then recharging the electrostrictive vibrating device. In a drive circuit that displaces the switch in the opposite direction, a power supply voltage higher than the logic control voltage can be turned on and off in order to switch the polarity, and the on-state of the switch can be turned on or off by pulsing the control current or applying the control voltage, consuming almost no power. PNPN element structure that can be held without
By connecting four semiconductor switches with FET element structure in a bridge configuration and inverting the drive logic of the two parallel switches and two diagonal switches in the bridge, one of the parallel or diagonal switch circuits is turned on. At this time, the other is controlled to be turned off, so the electrostrictive vibrator can be largely displaced with low power.

In addition, when switching the switch, if the electric charge previously charged in the electrostrictive vibration device is discharged by a discharge promotion circuit, a constant current circuit is used, or the switch is given constant current characteristics, the discharge, Since the charging operation is made faster, the operation of the electrostrictive vibration device can be made faster and the power consumption during driving can be reduced.

Furthermore, by using a drive input circuit that applies a high voltage in the polarization direction of the electrostrictive vibrator and a voltage below the polarization deterioration voltage in the reverse polarization direction when switching the switch, the electrostrictive vibrator can be There are advantages in that the voltage that can be applied can be much higher than in the past, and the amount of displacement can be increased two to three times as compared to the past. In addition, in this drive input circuit, since a voltage higher than the polarization deterioration voltage is always applied in the polarization direction, the polarization degraded by the voltage applied in the opposite polarization direction is redirected in the polarization direction by oscillation. It has the advantage of recovering when a voltage is applied. Therefore, it is highly reliable. In addition, by using a flip-flop mechanism consisting of a magnet or a spring that has a mechanically stable point near the end point that is displaced on both sides during vibration operation, the acting force at the end point of displacement can be increased. It also has the advantage of increasing operating speed.

Because of the above-mentioned effects, the present invention can be applied to all fields in which electrostrictive vibrators are used as actuators, but is particularly applicable to waveguide drive components of optical waveguide switching switches, coin processing devices, and magnetic card transfer devices. Card chuck mechanisms, video head drive parts, relay contact drive parts,
It is extremely effective when applied to punch pin drive parts of card punch mechanisms, ink pump drive mechanisms of ink jet printers, wire drive mechanisms of wire dot printers, etc.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional electrostrictive vibrator drive circuit, Fig. 2 is a schematic diagram of another conventional technology, and Fig. 3 is a schematic diagram of a conventional electrostrictive vibrator drive circuit.
4 is a diagram showing the relationship between the applied voltage and displacement amount, FIG. 5 is a circuit diagram showing an embodiment of the present invention, and FIG. 6 is a schematic diagram of another conventional technology. is a diagram of the output waveform of the pulse oscillation circuit, Figure 7 is a diagram for explaining the action of a constant current diode, Figure 8 is a diagram showing the voltage appearing at the drive terminal and the current flowing from the power supply circuit, and Figure 9 is a diagram showing the voltage appearing at the drive terminal and the current flowing from the power supply circuit. FIG. 10 is a circuit diagram showing another embodiment of the present invention, FIG. 11 is a circuit diagram for preventing malfunction of the switch, and FIG.
Fig. 2 is a circuit diagram showing the third embodiment, Fig. 13 is a circuit diagram showing the fourth embodiment, Fig. 14 is a circuit diagram showing the fifth embodiment, and Fig. 15 is a circuit diagram showing the sixth embodiment. 16 is a schematic configuration diagram showing an example of the configuration of an electrostrictive vibration device, FIG. 17 is a graph showing the relationship between applied voltage and displacement amount, and FIGS. 18 to 23 are each an electrostrictive vibration device A schematic configuration diagram showing another configuration example,
Figure 24 is a schematic configuration diagram showing an example of the configuration of an electrostrictive vibrator, Figure 25 is a graph showing its displacement, force, and characteristics, and Figure 26 is a schematic configuration diagram showing an example of the configuration of the electrostrictive vibrator. Fig. 27 is a graph showing its displacement, force, and characteristics, Fig. 28 is a graph showing the displacement time reduction effect, Fig. 29 is a schematic configuration diagram showing yet another example of the structure of an electrostrictive vibrator, and Fig. 30 is its configuration. It is a graph showing displacement, force, and characteristics. 1, 2, 2'... Electrostrictive plate, 3, 5... Electrode, 4
... Central electrode, 30, 31 ... Electrostrictive vibrator, 50
... Drive circuit, 71 ... Bridge circuit, 72 ...
Logic control circuit, 100 to 106... Electrostrictive vibration device, 121 to 124... N channel FET, PN1
~PN4...PNPN switch, SIT1~SIT4...
...Static induction transistor, SW _A ~ SW _D ... High voltage CMOS analog switch.

Claims (1)

[Claims] 1. In an electrostrictive vibrator drive circuit that alternately supplies positive and reverse voltages to an electrostrictive vibrator formed by stacking a plurality of ferroelectric electrostrictive plates, a high voltage semiconductor switch is configured in a bridge type. connection,
The bridge is equipped with a switch circuit that inverts and drives the drive logic of the parallel switch and diagonal switch so that when either the parallel or diagonal switch circuit is on, the other is off. , each high-voltage semiconductor switch is configured with a switch having a PNPN element structure, and the switch circuit connects the common connection terminal of the first and second PNPN switches, whose anodes are commonly connected, to the anode of the power supply circuit. At the same time, the common connection terminals of a third and fourth set of PNPN switches whose cathodes are commonly connected are connected to the cathode of the power supply circuit, and the anode of the first PNPN switch and the third PNPN switch are connected to the cathode of the power supply circuit.
The cathodes of the PNPN switches are connected in common and then connected to one electrode of the electrostrictive vibration device, and the anode of the second PNPN switch and the fourth
The cathodes of the PNPN switches are commonly connected and then connected to the other electrode of the electrostrictive vibration device, the gates of each PNPN switch and the logic control circuit are separated by a PNPN reverse junction or a photocoupler, and the gate circuit is connected to a pulse voltage. An electrostrictive vibrator drive circuit characterized in that it is driven by. 2. In an electrostrictive vibrator drive circuit that alternately supplies positive and reverse voltages to an electrostrictive vibrator formed by stacking multiple ferroelectric electrostrictive plates, high voltage semiconductor switches are connected in a bridge configuration,
By reversing the drive logic of the parallel switch and diagonal switch in the bridge, the switch circuit is controlled so that when either the parallel or diagonal switch circuit is on, the other is off. Each high-voltage semiconductor switch is configured with a FET switch, and the switch circuit connects a common connection terminal of the first and second FET switches whose input terminals are commonly connected to the anode of the power supply circuit. , the common connection terminals of the third and fourth sets of FET switches whose output terminals are commonly connected are connected to the cathode of the power supply circuit, and the output terminals of the first FET switch and the third FET switch are connected to each other.
The output terminals of the FET switches are connected in common and then connected to one electrode of the electrostrictive vibrator, and the input terminals of the second FET switch and the fourth
The output terminals of the FET switches are connected in common and then connected to the other electrode of the electrostrictive vibration device, and the gates of each FET switch and the logic control circuit are connected.
An electrostrictive vibrator drive circuit characterized by separation by a FET switch.