JPH04355985A - Digital displacement element drive device - Google Patents

Abstract

PURPOSE:To enable a digital displacement element drive device to be lessened in size and cost by a method wherein a reverse voltage generated by a reverse voltage generating means is so set to enable a digital displacement element to become zero in displacement when a reverse voltage is applied to the displacement element concerned after a power supply voltage is applied to the element. CONSTITUTION:When an OFF signal is set at an H level so as to turn an actuator OFF, a second switch is opened, and an element 2 is short-circuited through the intermediary of a diode 7, a resistor 9, a coil 10, and a second switch 12. Therefore, charge stored at the element 2 is made to flow out through the coil 10 to enable the coil 10 to generate an electrical field, whereby a reverse voltage is generated. By this setup, a reverse electric field is applied to the element 2. When an OFF signal is kept at an H level, the element 2, the diode 7, the resistor 9, and the coil 10 are connected in series, and a drive system is set in a damping oscillation. Therefore, a reverse voltage 1/3 or so as high as an ON-state voltage can be set by controlling the resistor 9 connected to the coil 10 in resistance value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a digital displacement element.

0002

2. Description of the Related Art A digital displacement element is a device in which the strain history is rectangular, and the strain exists in two states, on and off depending on the applied voltage. As shown in Figure 8, the voltage applied to the digital displacement element is gradually increased, and when it exceeds about 20 KV/cm, the displacement of the element becomes zero.
It increases rapidly from (A in the same figure). In the figure, the vertical axis is the displacement rate △ when the total length of the digital displacement element is L.
Indicates L/L.

[0003] The displacement is saturated at 30 KV/cm or more. In this state, even if the voltage is lowered to 0 KV/cm, the displacement is still maintained (Figure B). In other words, one-dimensional shape memory exists. For this reason, this digital displacement element is also called a shape memory ceramic element. To reduce the displacement to 0, reverse the electric field of the element to approximately -10
It is preferable to apply a negative electric field of KV/cm. However, if a negative electric field is further applied, the displacement increases again, so it must be controlled so as not to reduce it too much.

That is, in order to drive the digital displacement element 2, it is necessary to invert the electric fields at both ends of the digital displacement element 2. More specifically, the digital displacement element 2 is
To turn the element into N, apply a positive or negative voltage across the element, and to turn the element off, apply approximately 1/1 of the voltage when it is ON.
It is necessary to apply a reverse voltage of 3. For this purpose, as shown in FIG. 9, two positive and negative power supplies 20 and 22 are used, and the negative power supply 22 has a voltage approximately 1/3 that of the positive power supply 20, or as shown in FIG. to one positive power supply 21
A positive power supply 23 of about 1/4 of
, 23 is driven by a second switch 26 that applies voltages of 23 to the element 2. Note that the first switch 24
is turned on in response to the ON signal, and the second switch 26 is turned on in response to the OFF signal.

[0005]

[Problems to be Solved by the Invention] Conventionally, two positive and negative power supplies or two power supplies with different voltages were provided in order to turn on and off elements, resulting in a complicated power supply circuit. Therefore, there were problems in that the weight and volume increased, and the cost also increased. Therefore, an object of the present invention is to solve the above problems.

[0006]

[Means for Solving the Problems] A digital displacement element driving device according to claim 1 includes a power source, a digital displacement element that drives an actuator, and a first switch that applies voltage from the power source to the digital displacement element. , comprising a reverse voltage generating means for generating a reverse voltage using a voltage from a power supply, and a second switch for applying the reverse voltage generated by the reverse voltage generating means to a digital displacement element, The voltage is of such a magnitude that the displacement of the digital displacement element becomes zero when the voltage from the power supply is applied to the digital displacement element and then the reverse voltage is applied to the digital displacement element.

A digital displacement element driving device according to a first aspect of the present invention includes a power source, an actuator, a digital displacement element for driving the actuator, first, second, and third switches, and a reverse voltage generated by the voltage from the power source. and a reverse voltage generating means for generating a voltage, the power supply voltage having a magnitude such that the displacement of the digital displacement element becomes 0 when the power supply voltage is applied after applying the reverse voltage to the digital displacement element. The first and second switches generate a reverse voltage in the reverse voltage generating means, the second switch applies the reverse voltage to the digital displacement element to displace the digital displacement element, and the third switch The element voltage is set to 0 by the switch, the power supply voltage is applied to the digital displacement element by the second and third switches, and the voltage of the digital displacement element is set to 0 by the second switch.

[0008]

[Operation] The operation of the apparatus according to claim 1 will be explained based on the embodiment shown in FIG. When the first switch 5 is turned on, electric charge is supplied from the power supply 1 to the digital displacement element 2,
The displacement of the digital displacement element 2 increases. The digital displacement element 2 is electrically equivalent to a capacitor, and charges are accumulated therein.

When the second switch 12 is turned on, the digital displacement element 2 is short-circuited via the diode 7 and the coil 10. The charge stored in the digital displacement element 2 flows through the coil 10, and energy is stored in the coil 10. Even when the charge is removed, the energy stored in the coil 10 causes the current to continue to flow, generating a reverse voltage. A negative voltage is applied to the digital displacement element 2 due to the reverse voltage. The displacement of the digital displacement element then becomes zero.

Next, the operation of the apparatus according to claim 2 will be explained based on the embodiment shown in FIG. When the first and second switches 61 and 62 are turned on, voltage E0 is applied to the coil 10, and current begins to flow through the coil 10. Next, the first switch 61 is turned off while the second and third switches 62 and 63 are turned on, and the coil 10 and digital displacement element 2 are turned off.
When these are connected in series, a negative voltage of -3E0 is applied to element 2. Thereafter, when the second switch 62 is turned off and the third switch 63 is turned on, the voltage applied to the element 2 becomes zero. Next, when the first switch 61 and the third switch 63 are turned on simultaneously, a voltage of E0 is applied to the element 2, and the displacement of the digital displacement element becomes zero. Next, when the first and third switches are turned off and the second switch 62 is turned on, the electric charge of the element 2 is short-circuited through the coil 10, and the voltage applied to the element becomes zero.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below based on the drawings. FIG. 1 shows a first embodiment of a digital displacement element driving device according to the present invention. In this figure, 2 is a digital displacement element (element) that drives the actuator 3,
Electrically equivalent to a capacitor. Reference numeral 5 denotes a first switch, which turns on in response to the ON signal and applies voltage to the element 2. 7 is a diode, 9 is a resistor, 10 is a coil (reverse voltage generating means), and 12 is an OFF signal in response to an OFF signal.
This is the second switch.

The negative end of the coil 10 is connected to a resistor 9 and a diode 7.
is connected to the digital displacement element 2 via the coil 10
The other end is grounded via the second switch 12. In this figure, when the ON signal is set to H to start driving, the first switch 5 is turned on and an electric field is applied to the element 2. As a result, the element 2 is distorted and the actuator 3 is driven. Since the element 2 is electrically equivalent to a capacitor, the electric charge supplied when the first switch 5 is turned on is accumulated in the element 2.

OFF to turn off the actuator 3
When the F signal is set to H, the second switch 12 is opened, and the element 2 is connected to the diode 7, the resistor 9, the coil 10, and the second switch 12.
is short-circuited via the switch 12. Therefore element 2
The charges accumulated in the coil 10 flow through the coil 10, an electric field is generated in the coil 10, and eventually a reverse voltage is generated. As a result, a reverse electric field is applied to the element 2. When the OFF signal is H, the element 2, diode 7, resistor 9, and coil 10 are connected in series, and the drive system exhibits damped vibration. Therefore, in order to set a reverse voltage that is approximately 1/3 of the ON voltage, the value of the resistor 9 connected in series with the coil 10 may be adjusted. Due to the diode 7, the electric charge flows in one direction through the resistor 9, the coil 10, and the second switch 12, so that the voltage applied to the element 2 is not reversed again.

FIG. 2 is a voltage-current characteristic diagram of the example shown in FIG. 1, where VL is the voltage of the coil 10 and IL is the current of the coil 10. FIG. 3 is a diagram showing a second embodiment of the digital displacement element driving device of the present invention, in which one end of the coil 10 (reverse voltage generating means) is connected to the digital displacement element 2 and the other via a diode 7 and a second switch 12. It is connected to the power supply 1, and the other end of the coil 10 is connected to the resistor 9.
It is connected to the digital displacement element 2 via.

When the ON signal is set to H to start driving, the first switch 5 is turned on, an electric field is applied to the element 2, charge is accumulated, and the actuator 3 is driven. Set the OFF signal to H to turn off the actuator 3.
When the second switch 12 is closed, the element 2 is short-circuited via the diode 7, the second switch 12, the coil 10, and the resistor 9. The charge accumulated in the element 2 flows through the coil 10, an electric field is generated in the coil 10, and a reverse voltage is generated soon. As a result, an electric field is generated in the element 2, and eventually a reverse voltage is generated. As a result, element 2
A reverse electric field is applied to. The magnitude of this reverse electric field is the resistance 9
The electric field is adjusted to approximately 1/3 of the electric field when the first switch 5 is turned on.

FIG. 4 shows a third embodiment of the digital displacement element driving device of the present invention. In the figure, one end of the digital displacement element 2 is connected to a secondary winding T2 of a transformer 4 (reverse voltage generating means), and the other end is grounded. The power source 1 is connected to the center of the primary winding T1 of the transformer 4, and the primary winding T1 is divided into two (T11, T12).

Reference numeral 5 denotes a first transistor, and one primary winding T11 of the transformer 4 is energized in response to an ON signal. 12 is a second transistor, and the other primary winding T12 of the transformer 4 is energized in response to the OFF signal. 7 and 8 are diodes for protecting the transistors.

In the figure, when the ON signal is set to H to start driving, the first transistor 5 is turned on, a voltage is applied to the primary winding T11, and the primary winding T11 becomes energized. To drive the element 2 on the secondary side, the ON signal is pulse-driven, and after several hundred microseconds, the ON signal is set to H. Then, a voltage is generated in the secondary winding T2. The voltage is determined by the turns ratio of the transformer 4, and is T2/T of the power supply 1 voltage.
11 voltage is generated on the secondary winding T2 side. Furthermore, since the impedances of the transformer 4 and the element 2 are large, the reverse voltage applied to the element 2 is in the form of a pulse.

When the ratio of the primary windings T11 and T12 is about 3:1, a reverse voltage of about 1/3 of the ON voltage is applied to the element 2. In this way, the actuator 3 can be turned on and off by setting the ratio between the primary windings T11 and T12 to approximately 3:1, and by changing the winding ratio between the primary winding T11 and the secondary winding T2. Since the power supply voltage of the primary winding can be set to T11/T2 of the driving voltage of the element 2, it is also possible to lower the power supply voltage.

Note that FIG. 5 is a voltage-current characteristic diagram of the example shown in FIG. 4, where VC is the voltage of the transformer 4. In each of the embodiments described so far, a potential continues to be applied to the element 2 for a certain period of time until the displacement returns to 0, but if the voltage continues to be applied and the element is placed in a humid atmosphere, electrode migration causes the element to reliability may be reduced. Furthermore, voltage remains applied to the element 2 and the switches (for example, transistors) connected thereto, which poses a safety problem if there is a possibility of touching them.

FIG. 6 is a circuit diagram showing a fourth embodiment of the digital displacement element driving device of the present invention, and according to this embodiment, the above-mentioned problems are solved. Figure 7 is the 6th
FIG. 3 is a voltage-current characteristic diagram of the embodiment shown in the figure. 1 in 6 figures
is a power source, 2 is a digital displacement element, 3 is an actuator, 10 is a coil as a reverse voltage generating means, 61, 62,
63 are first, second, and third switches, respectively; 64 is a diode coupled in parallel to the second switch 62; 65 is a diode coupled in parallel to the third switch 63;
, S2, and S3 are the first, second, and third switches 6, respectively.
1, 62, and 63 (H or L).

In FIG. 7, VL and IL are the voltage and current applied to the coil 10, respectively, and VC is the voltage applied to the digital displacement element 2. Next, the operation of this embodiment having the above configuration will be explained. In order to generate displacement in the digital displacement element 2, when the S1 and S2 signals are simultaneously set to H in FIG. 6, the first and second switches 61 and 62 are turned on, voltage E0 is applied to the coil 10, and the coil current begins to flow. (t0 in Figure 7) At the time of t1, S
The coil 10 and the digital displacement element 2 are connected in series by setting only one signal to L (the first switch 61 is turned off while the second and third switches 62 and 63 are turned on). Then, the voltage across the coil 10 is reversed, and the voltage across the coil 10 is reversed.
Current continues to flow in the same direction. In other words, Grand → 65
A current flows through → element 2 → coil 10 → second switch 62, and a negative voltage is applied to element 2. From the pulse width of (t1-t0), the voltage across the element 2 becomes -3E0.

[0023] After that, at t2, set S2 to L and S3 to H (
Turn off the second switch 62 and turn off the third switch 63.
(N), the charge of element 2 is short-circuited via coil 10, and the voltage applied to element 2 becomes zero. Voltage of element 2 is 0
However, the displacement remains unchanged. To return the displacement to 0, -1/3 times the voltage is applied. Therefore, S1 at t4
, S3 are set to H at the same time. A voltage of E0 is applied to element 2.

When S1 and S3 are set to L and S2 is set to H at t5, the electric charge of the element 2 is short-circuited through the coil 10, and the voltage applied to the element becomes 0.

[0025]

According to the present invention, the elements can be driven by a single power supply voltage, which simplifies the power supply circuit. Furthermore, the reverse voltage can be easily set.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of a digital displacement element driving device of the present invention.

FIG. 2 is a voltage-current characteristic diagram of the embodiment shown in FIG. 1.

FIG. 3 is a circuit diagram showing a second embodiment of the digital displacement element driving device of the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the digital displacement element driving device of the present invention.

FIG. 5 is a voltage-current characteristic diagram of the embodiment shown in FIG. 4;

FIG. 6 is a circuit diagram showing a third embodiment of the digital displacement element driving device of the present invention.

7 is a voltage-current characteristic diagram of the embodiment shown in FIG. 6. FIG.

FIG. 8 is a voltage-displacement diagram of a digital displacement element.

FIG. 9 is a circuit diagram showing an example of a conventional digital displacement drive device.

FIG. 10 is a circuit diagram showing another example of a conventional digital displacement element driving device.

[Explanation of symbols]

1 Power supply 2 Digital displacement element 3 Actuator 4 Transformer 5 First switch 12 Second switch 7, 8 Diode 9 Resistor 10 Coil (reverse voltage generation means) 61 First switch 62 Second switch 63 Third switch T11 , T12 Primary winding of transformer T2 Secondary winding of transformer

Claims (2)

[Claims] 1. A power source, a digital displacement element that drives an actuator, a first switch that applies a voltage from the power source to the digital displacement element, and a reverse voltage generating means that generates a reverse voltage using the voltage from the power source. , a second switch that applies the reverse voltage generated by the reverse voltage generating means to the digital displacement element, and the reverse voltage generated by the reverse voltage generating means applies the voltage from the power source to the digital displacement element. A digital displacement element driving device characterized in that the displacement of the digital displacement element becomes zero when the reverse voltage is applied after the displacement of the digital displacement element is applied. 2. A power source, an actuator, a digital displacement element for driving the actuator, first, second, and third switches, and reverse voltage generating means for generating a reverse voltage using a voltage from the power source. The power supply voltage has a magnitude such that the displacement of the digital displacement element becomes 0 when the power supply voltage is applied after applying the reverse voltage to the digital displacement element, and A switch generates a reverse voltage in the reverse voltage generating means, a second switch applies the reverse voltage to the digital displacement element to displace the digital displacement element, a third switch sets the element voltage to 0, and the second switch applies the reverse voltage to the digital displacement element to displace the digital displacement element. 1. A digital displacement element driving device, characterized in that a power supply voltage is applied to the digital displacement element by the second and third switches, and the voltage of the digital displacement element is set to zero by the second switch.