JPH08294288A - Drive circuit of impact moving apparatus - Google Patents

Abstract

PURPOSE: To enable output of the optimum drive voltage which is not required to be amplified with introduction of a simplified and low cost circuit configuration. CONSTITUTION: Asymmetrical drive voltage including rapid voltage rise and gradual voltage drop is applied to a piezoelectric element 12 through charging or discharging the piezoelectric element 12 via resistors R1 , R2 by inputting the on, off signals from a terminal 1 to the gates G of transistor Tr1, Tr2 connected in series between the power supply VE and common terminal GND and connecting the terminal 2 provided at the connecting point of the transistors Tr1, Tr2 in order to turn on and off the transistors Tr1, Tr2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of an impact type moving device for moving an object using an electromechanical energy conversion element such as a piezoelectric element.

[0002]

2. Description of the Related Art JP-A-63-299785 and JP-A-4
Japanese Patent Publication No. 207982 and the like propose, for example, an impact type moving device which uses an electromechanical conversion element such as a piezoelectric element and performs a minute movement by an impact force generated by its rapid deformation. FIG. 4 is a front view schematically showing an example of the impact type moving device. As shown in the figure, in the impact type moving device 10, one end of a piezoelectric element 12 as an electromechanical conversion element is attached to a rectangular parallelepiped relative movement member 11, and an inertial body 13 is attached to the other end of the piezoelectric element 12. Is constructed and configured.

The impact type moving device 10 is mounted on a fixed body 14 having a static friction coefficient μ. At this time, only the relative movement member 11 contacts the surface 14a of the fixed body 14, and neither the piezoelectric element 12 nor the inertial body 13 contacts.
The drive voltage device 15 is connected to the piezoelectric element 12, and continuously applies a drive voltage having an asymmetrical waveform as shown in FIG. 5 to the piezoelectric element 12.

That is, in FIG. 5, when a drive voltage having a large voltage increase rate is applied from time t ₀ to time t ₁ , the piezoelectric element 12 expands rapidly according to the voltage value. When the piezoelectric element 12 expands rapidly, an impact force acts on the relative motion member 11 and the inertial body 13, the relative motion member 11 and the fixed body 14 are in a dynamic friction state, and the relative motion member 11 and the inertial body 13 are fixed. The body 14 moves in the opposite direction against the static friction force, that is, the relative motion member 11 moves leftward in the drawing. Then, at time t ₁ , the piezoelectric element 12 is fully extended and no displacement occurs, so that the relative motion member 11 stops moving.

A driving voltage having a small voltage decrease rate is applied from time t ₁ to time t ₂ , and the piezoelectric element 12 contracts gently according to the voltage value. As a result, the relative motion member 11 and the fixed body 14 are brought into a static friction state, and the inertial body 13
Only is slowly pulled back at a constant acceleration. Time t ₂
Then, the inertial body 13 that has been pulled back by the above-mentioned acceleration is suddenly stopped. As a result, the inertial body 13 collides with the relative motion member 11, and the relative motion member 11 further moves leftward in the drawing. Then, the relative motion member 11
Is stopped by the dynamic frictional force of the fixed body 14 and returns to the initial state. Thereafter, the asymmetrical drive signal shown in FIG.
It is applied in a predetermined cycle, and the relative motion member 11 slightly moves.

[0006]

As described above, this impact type moving device requires a voltage having an asymmetric waveform to drive, so that the driving circuit is relatively complicated. Since a general electronic component operates at a power supply voltage of about 5 [V], a circuit that requires many kinds of electronic components is manufactured so as to operate at a power supply voltage of about 5 [V]. However, the impact type moving device has the piezoelectric element 12
A voltage of about 10 to 50 [V] is usually required to drive the. Therefore, the drive circuit 15 uses the power supply voltage 5
It is necessary to manufacture the voltage generating circuit 15a having an asymmetrical waveform that operates at [V], amplify its output to about 30 [V] by the amplifier 15b, and drive the piezoelectric element 12.

As described above, in the conventional impact type moving device, the driving circuit for generating the asymmetric waveform voltage required for driving is complicated. Moreover, since an amplifier operating at a high voltage is required, the driving circuit becomes expensive.

It is an object of the present invention to provide a drive circuit for an impact type moving device capable of outputting an optimum drive voltage that does not need to be amplified, with a simple and inexpensive circuit configuration.

[0009]

In order to solve the above-mentioned problems, the invention of claim 1 is a drive circuit of an impact type moving device for applying a drive signal having an asymmetric waveform to an electromechanical energy conversion element to obtain a drive force. In, a charging circuit that supplies a charging current to the electromechanical energy conversion element, and a discharge that has a discharge time constant different from the charging time constant of the charging circuit, and discharges the electric charge accumulated in the electromechanical energy conversion element. A circuit and a charge / discharge switching circuit that switches the operation of the charging circuit and the discharging circuit by a periodical switching command signal are provided.

According to a second aspect of the present invention, in the drive circuit of the impact type moving device for applying the asymmetrical waveform drive signal to the electromechanical energy conversion element to obtain the drive force, the power source unit (V
_E ) and the first and second transistor elements (Tr1, Tr2) connected in series between the common potential part (GND)
And a first connected to a terminal connected to the power supply section or the common potential section of the first and second transistor elements.
And a second resistance element (R1, R2), an input section (1) for inputting a periodic switching command signal to the control terminals of the first and second transistor elements, and the first and second transistors. An output part (2) provided at a connection point of the element and connected to the electromechanical energy conversion element, and when the first transistor element is activated, By charging the electromechanical energy conversion element and discharging the electromechanical energy conversion element through the second resistance element when the second transistor element is activated, the electromechanical energy conversion element is asymmetrical to the electromechanical energy conversion element. The feature is that a driving voltage having a waveform is applied. According to a third aspect of the invention, in the drive circuit for the impact type moving device according to the second aspect, the first and second resistance elements are internal resistances of the first and second transistor elements. I am trying. Claim 4
In the drive circuit of the impact type moving device according to the second or third aspect, the first invention is characterized in that the first and second transistor elements are complementary types.

[0011]

According to the present invention, the charging circuit supplies the charging current to the electromechanical energy conversion element, and the discharging circuit discharges the electric charge accumulated in the electromechanical energy conversion element. Then, the charging / discharging switching circuit switches the operation of the charging circuit and the discharging circuit by a periodic switching command signal. The drive voltage of the electromechanical energy conversion element is asymmetric because the charge time constant and the discharge time constant are different. For example, if you want to make a sudden change in order to make it into a dynamic friction state, make the time constant smaller and make it in a static friction state.
If you want to change slowly, you can increase the time constant.

[0012]

【Example】

(First Embodiment) The present invention will be described in detail below with reference to the drawings and the like. FIG. 1 is a circuit diagram showing a first embodiment of a drive circuit for an impact type moving device according to the present invention. Since the piezoelectric element 12 has a structure in which a dielectric is sandwiched between two electrodes, its simple equivalent circuit can be considered to have capacitance. Therefore, when the piezoelectric element 12 is driven by using the drive circuit as shown in FIG. 1, it is possible to supply a voltage having an asymmetric waveform to the piezoelectric element 12.

The transistors Tr1 and Tr2 are field effect transistors (FETs), and are connected in series between the power source V _E and the common terminal GND. Since the two transistors Tr1 and Tr2 are of a complementary type, one input causes the O of the transistors Tr1 and Tr2 to change.
It is possible to control N and OFF. Transistor Tr
1 and Tr2 form a CMOS inverter. Although it is necessary to use transistors having high breakdown voltage for the transistors Tr1 and Tr2, the transistors Tr1 and Tr2 are simpler and cheaper than the case where amplifiers having high breakdown voltage are used.

The terminal (input section) 1 is a transistor Tr.
1 and Tr2 are connected to a gate G that serves as a control terminal,
This is a terminal to which an ON / OFF signal as shown in (b) is input. The terminal (output section) 2 has two transistors Tr.
The piezoelectric element 12 is provided at the connection point of 1 and Tr2, and
It is a terminal that outputs a drive signal as shown in (c). The resistor R1 is connected between the source S of the transistor Tr1 and the power supply V _E , and the resistor R2 is connected between the source S of the transistor Tr2 and the common terminal GND.

Next, the operation of the drive circuit of this embodiment will be described. A voltage V1 shown in FIG. 1B is input to the terminal 1 to control ON / OFF of the transistors Tr1 and Tr2 to supply a desired voltage to the piezoelectric element (corresponding to the capacitance C _L ) 12. . In Figure 1, when the transistor Tr1 is ON, the capacitance C _L is a piezoelectric element 12, the resistor R
After being charged through 1, the battery is discharged through the resistor R2. When the power supply voltage is V _E, capacitor C _L at the time of charging (charging time constant C _L · R1) through a capacitor C _L and resistor R1
Voltage Vc, as t the _{time, V C = E × (1} -exp (-t / (C L × R1))) ... (1) Next, discharge (charging time constant via a resistor R2 across C _L / R2)
When becomes _{V C = E × exp (-t} / (C L × R2)).

The transistors Tr1 and Tr2 include
The ON resistance value can be neglected if a small ON resistance is used, so that the rate of change of the voltage applied to the piezoelectric element 12 can be changed by adjusting the values of the resistors R1 and R2. For example, when increasing the applied voltage, it is desired to change the value of the resistor R1 to 0 because it is desired to change it rapidly. Since it is desired to change the applied voltage gently when decreasing the applied voltage, the value of the resistor R2 may be increased.

(Second Embodiment) FIG. 2 is a circuit diagram showing a second embodiment of the drive circuit of the impact type moving device according to the present invention. Compared to the first embodiment, the second embodiment has no resistors R1 and R2. The reason for this is
This is because the ON resistances of the transistors Tr1 and Tr2 serve as the resistances R1 and R2. In the drive circuit of the second embodiment, for example, the applied voltage V2 of the piezoelectric element 12 is
When abruptly increasing and gradually decreasing, a transistor Tr1 having a small ON resistance and a transistor Tr2 having a large ON resistance may be used.

(Third Embodiment) FIG. 3 is a circuit diagram showing a third embodiment of the drive circuit of the impact type moving device according to the present invention. In the third embodiment, the transistors Tr1 and Tr2 are of the bipolar type. Furthermore, the transistors Tr1 and Tr2 are not complementary. Even in such a configuration, the terminals 1-1 and 1
-2, the voltage V as shown in FIGS. 3B and 3C, respectively.
When 1-1 and V1-2 are input, when the voltage V2 applied to the piezoelectric element 12 increases, the voltage is supplied via the transistor Tr1 and when decreasing, the voltage is supplied via the transistor Tr2. And T
By adjusting the ON resistance of r2, a voltage having a desired rate of change can be obtained.

The present invention is not limited to the embodiments described above, and various modifications and changes are possible, which are also included in the present invention. For example, the electromechanical conversion element is not limited to the piezoelectric element,
It may be an electrostrictive element or a magnetostrictive element. The impact type moving device is not limited to the one shown in FIG. 4, but a beam-shaped relative moving member is provided with an impact force in the longitudinal direction by using a piezoelectric element to move a moving body placed on the relative moving member. It may be moved.

[0020]

As described in detail above, the drive circuit of the present invention can generate a voltage suitable for driving an impact type moving device with a simple circuit configuration, and further, a means for amplifying the output. do not need. Therefore, a small and inexpensive drive circuit can be supplied. In addition, the circuit is simple and the number of required parts is small, so that the drive circuit can have high reliability.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a drive circuit for an impact type moving device according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the drive circuit of the impact type moving device according to the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the drive circuit of the impact type moving device according to the present invention.

FIG. 4 is a front view showing a configuration of an impact type moving device.

FIG. 5 is a waveform diagram showing a drive voltage in a conventional impact type moving device.

[Explanation of symbols]

1, 2 terminals 12 Piezoelectric element Tr1, Tr2 transistor V _E power supply GND common terminal R1, R2 resistance

Claims (4)

[Claims] 1. A drive circuit of an impact type moving device for obtaining a driving force by applying a drive signal having an asymmetrical waveform to an electromechanical energy conversion element, a charging circuit for supplying a charging current to the electromechanical energy conversion element, Has a discharge time constant different from the charge time constant of the charging circuit,
A discharge circuit that discharges the electric charge accumulated in the electromechanical energy conversion element; and a charge / discharge switching circuit that switches the operations of the charging circuit and the discharging circuit by a periodic switching command signal. Drive circuit for impact type moving device. 2. A drive circuit of an impact type moving device for obtaining a driving force by applying a drive signal having an asymmetrical waveform to an electromechanical energy conversion element, the first circuit being connected in series between a power supply section and a common potential section. And a second transistor element, first and second resistance elements connected to terminals connected to the power supply section or the common potential section of the first and second transistor elements, and the first and second transistor elements. An input section for inputting a periodic switching command signal to the control terminal of the second transistor element; and an output section provided at the connection point of the first and second transistor elements and connected to the electromechanical energy conversion element. When the first transistor element is activated, the electromechanical energy conversion element is charged via the first resistance element, and the second transistor element is activated. First, by driving the electromechanical energy conversion element through a second resistance element, a drive voltage having an asymmetrical waveform is applied to the electromechanical energy conversion element. circuit. 3. The drive circuit for the impact type moving device according to claim 2, wherein the first and second resistance elements are internal resistances of the first and second transistor elements. Drive circuit for impact type moving device. 4. The drive circuit for the impact type moving device according to claim 2, wherein the first and second transistor elements are complementary types. circuit.