HK1086114B - Piezoelectric actuator driver - Google Patents

Description

Driver of piezoelectric actuator

Technical Field

The present invention relates to a driver of a piezoelectric actuator (piezo electric actuator), and more particularly, to an improvement in a driver of a piezo electric actuator for switching and driving a plurality of piezo electric actuators mechanically moving each of a plurality of mechanism parts mounted directly or indirectly on the driver.

Background

In general, as shown in fig. 7A, the piezoelectric actuator 1 is configured in such a manner that thin piezoelectric sheets (thin piezoelectric sheets) 5 and 7 are attached to opposite surfaces of a rectangular conductive plate 3, and electrodes 5a and 7A are disposed on the opposite surfaces of each of the piezoelectric sheets 5 and 7 which are not in contact with the plate 3, the plate 3 is used as a common electrode, wherein the electrodes 5a and 7A are connected to a positive terminal P1 and a negative terminal P2, the plate 3 is connected to a common terminal P3, and when one end (the left end in the drawing) is supported in the longitudinal direction of the plate 3 in an open-ended shape, the other end (the right end in the drawing) is formed as an open end. Note that the support of the piezoelectric actuator 1 is not shown in fig. 7 (see fig. 8).

In the thus-constituted piezoelectric actuator 1, for example, when a positive potential + is applied to the positive terminal P1 and the common terminal P3 through two terminals that are short-circuited (between the electrode 5a of the piezoelectric sheet 5 and the plate 3), the plate 3 is bent so as to move the open end in the upward direction as shown by the broken line of fig. 7A, in accordance with the polarization directions of the piezoelectric sheets 5 and 7.

Meanwhile, when a negative potential is applied to the common terminal P3 and the negative terminal P2, for example, by short-circuiting both terminals (between the plate 3 and the electrode 7a of the other piezoelectric sheet 7), the open end is moved in the downward direction as indicated by a one-dot chain line in the figure.

Therefore, the piezoelectric actuator 1 is used as various driving sources such as a needle selection driver of a knitting needle of a knitting machine by utilizing a bending motion due to such a piezoelectric phenomenon.

Specifically, as shown in fig. 8, the above-mentioned plurality of piezoelectric actuators 1 are arranged in parallel with each other at a predetermined interval apart from each other on a side wall 9a in a long and narrow insulating box-shaped case 9 (as shown in the figure, divided into 1a, 1b, 1c, 1e, 1f, 1g, and 1h), and one end is supported in an open end shape, and by an action, the other end is inserted as an open end into an operation hole 11 formed on a side wall 9b opposite to the side wall 9a in the case 9. Then, by a certain action, the operation piece 13 as a mechanical component fixed to the other end is projected from the operation hole 11.

All of the plurality of piezoelectric actuators 1a to 1h (including the operation piece 13) supported by the housing 9 are the same actuator, and fig. 9 is a view of the housing 9 viewed from the side wall 9b side of the housing 9, particularly viewed from the tip end side of the operation piece 13.

When a positive/negative direct-current drive voltage is applied from the power supply section 15 to the plurality of piezoelectric actuators 1a to 1h through the controller 17, each of the piezoelectric actuators 1a to 1h is bent and the operation piece 13 protruding from the operation hole 11 of the housing 9 is moved. This facilitates the movement of a selector lever (lever) (mechanical part), not shown, by means of the operating plate 13.

Therefore, when the controller 17 switches and selects the drive voltages applied to the plurality of piezoelectric actuators 1a to 1h, the piezoelectric actuators 1a to 1h can be used as, for example, a needle selection driver of a knitting needle of a knitting machine.

General patent documents according to such a piezoelectric actuator include patent document 1 (japanese patent laid-open No. 5-302251).

In addition, the structure shown in fig. 10 is given as an example of a structure in which the driving voltages applied to the plurality of piezoelectric actuators 1a to 1h are selectively controlled by the controller 17.

Specifically, phototransistors Q1 and Q2, Q3 and Q4, Q5 and Q6, Q7 and Q8, which are connected in series, respectively, are placed corresponding to the plurality of piezoelectric actuators 1a to 1 h. The collector of the transistor Q1 is connected from the positive terminal feed line 19 to the phototransistor Q2 through a resistor R1, and the emitter of another transistor Q2 is connected to the negative terminal feed line 21 through a resistor R2.

The positive terminal P1 in the piezoelectric actuator 1a is connected to the positive terminal feed line 19, the negative terminal P2 is connected to the negative terminal feed line 21, and the junction of the phototransistors Q1 and Q2 is connected to the common terminal P3 of the piezoelectric actuator 1 a.

Similarly, the phototransistors Q3 to Q8 are also connected to the positive and negative terminal feeding lines 19 and 21 through the resistors R3 to R8, and the piezoelectric actuators 1b to 1d are also connected to the junction points of the phototransistors Q3 to Q8 and the positive and negative terminal feeding lines 19 and 21.

In addition, in the vicinity of and corresponding to the serially connected phototransistors Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8, the serially connected light emitting diodes D1 and D2, D3 and D4, D5 and D6, and D7 and D8 are disposed.

The light emitting diodes D1 to D8 are caused to emit light by being selectively energized by the switching control section 23, and thereby form the driver of the above-described piezoelectric actuator.

In fig. 10, the controller 17 is formed by the phototransistors Q1 to Q8, the light emitting diodes D1 to D8, and the switching control section 23.

Note that in fig. 10, the light emitting diodes D1 to D8 are connected by one line from the switching control section 23. However, in practice, the light emitting diodes D1 to D8 are connected by a single wiring corresponding to the light emitting diodes D1 to D8. This wiring is simplified in fig. 8 for easy understanding.

Therefore, for example, when a driver of the piezoelectric actuator is used in, for example, a needle selection driver, and the piezoelectric actuator 1a among the plurality of piezoelectric actuators 1a to 1D is conduction-controlled, the start end is moved in the upward direction by the conduction control of selecting only the light emitting diode D1 by the switching control section 23. At the same time, the tip is moved in a downward direction by selecting the conduction control of only the light emitting diode D2.

Similarly, in the other piezoelectric actuators 1b to 1h, the tip is moved only by the conduction control of any one of the light emitting diodes D3 or D4, D5 or D6, and D7 or D8, and all the piezoelectric actuators 1a to 1h are simultaneously off-controlled after a certain on-control period has elapsed.

In addition, in the driver of the piezoelectric actuator described above, as shown in fig. 7B, the piezoelectric sheets 5 and 7 function as a kind of capacitors C1 and C2. Therefore, even when a driving voltage is applied to the piezoelectric sheets 5 and 7 of each of the piezoelectric actuators 1a to 1h so as to on-control the plurality of piezoelectric actuators 1a to 1h, any large current is prevented from flowing over the on-control period. Therefore, it is considered that power saving of the entire apparatus is easily achieved.

In addition, in the driver of the piezoelectric actuator thus constituted, the resistors R1 to R8 connected between the phototransistors Q1 to Q8 and the positive and negative terminal feeder lines 19 and 21 have a current limiting function to suppress the flow of the drive current through the phototransistors Q1 to Q8, so that the power consumption of the entire driver is not increased by the increased drive current generated when one of the phototransistors is switched to the other of the phototransistors Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8, thereby causing the phototransistors Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8 to be temporarily conductive or to undergo a rapid current change, resulting in a large drive current.

However, in the driver of the piezoelectric actuator described above, a large drive current is inhibited from flowing through the piezoelectric sheets 5 and 7 constituting the plurality of piezoelectric actuators 1a to 1h during the on control period thereof. However, in the piezoelectric sheets 5 and 7, that is, in each of the piezoelectric actuators 1a to 1h, the capacitors C1 and C2 are equivalently formed. In addition, the capacitance of such a capacitor has a large value of about 150 to 600nF, and therefore, a large drive current is liable to flow through the piezoelectric sheets 5 and 7 just after the on control of the piezoelectric actuators 1a to 1 h.

Therefore, when any one of the control piezoelectric actuators 1a to 1b is turned on, when the other one of the control piezoelectric actuators 1a to 1h is turned on in pairs, it frequently occurs that a large drive current flows, so that it is easy to increase the power consumption of the entire driver.

In order to avoid the above situation, it is necessary to cope with the increase in the drive current by processing such as making the wiring of the feeder line thick, resulting in a tendency to increase the cost.

The present inventors have studied the piezoelectric actuators 1a to 1h and their functions and equivalent circuits carefully. Therefore, the present inventors focused on the point that the piezoelectric actuators 1a to 1h have a function equivalent to a capacitor, and in addition, each of the piezoelectric actuators 1a to 1h is electrically connected in parallel, and the piezoelectric sheets 5 and 7 of the piezoelectric actuators 1a to 1h of the discharge cutoff control. Thus, the present invention has been completed.

The present invention is provided to solve the above-described problems, and an object of the present invention is to provide a driver of a piezoelectric actuator capable of suppressing the power consumption of the entire apparatus to be low by greatly reducing a driving current during on/off switching control in driving for driving a plurality of actuators.

Disclosure of Invention

To solve the above-described problems, the present invention provides a driver for a piezoelectric actuator constituted by a plurality of piezoelectric actuators in which first and second piezoelectric sheets are respectively attached to opposite surfaces of a plate interposed between the first and second piezoelectric sheets, the driver comprising: a plurality of piezoelectric actuators mechanically moving a mechanical part directly or indirectly connected to each piezoelectric actuator; positive terminal feed lines connected directly to opposite sides of the first piezoelectric patch in common to the side attached to the board; negative terminal feed lines connected directly to opposite sides of the second piezoelectric sheet to the side attached to the board in common; a controller for selectively conducting and charging the first or second piezoelectric patches by selectively connecting the positive terminal or negative terminal feeder to an opposite side of the first or second piezoelectric patches from a side attached to the board to apply a driving voltage to the first and second piezoelectric patches, wherein the controller has functions of: the drive voltage applied to the first or second piezoelectric patch of each piezoelectric actuator selected to be on-controlled is turned off, and at the same time, the first or second piezoelectric patch of any other piezoelectric actuator to be on-controlled next is on-controlled to apply the drive voltage thereto, and a discharge current is allowed to flow from the first or second piezoelectric patch of any one piezoelectric actuator subjected to off-control, and by this discharge current, the first or second piezoelectric patch of any other piezoelectric actuator subjected to on-control is directly charged through the positive-terminal or negative-terminal feeder.

Drawings

Fig. 1 is a circuit block diagram showing an embodiment relating to a driver of a piezoelectric actuator according to the present invention.

Fig. 2 is a waveform diagram illustrating a switching operation of a driver of a piezoelectric actuator according to the present invention.

Fig. 3 is a schematic equivalent circuit diagram of the piezoelectric actuator of the present invention.

Fig. 4 is a circuit diagram for explaining the operation of the piezoelectric actuator of the present invention.

Fig. 5 is a view for explaining the operation of the piezoelectric actuator of the present invention.

Fig. 6 is a circuit block diagram showing other embodiments related to the driver of the piezoelectric actuator according to the present invention.

Fig. 7 is a sectional view a and an equivalent circuit diagram B showing a general configuration of the piezoelectric actuator.

Fig. 8 is a sectional view showing an example of a structure to which the piezoelectric actuator is applied.

Fig. 9 is a side view of a main portion of fig. 8.

Fig. 10 is a circuit block diagram showing a driver of a conventional piezoelectric actuator.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings of the present invention. Note that the same reference numerals are assigned to the same components as in the conventional example, without further explanation.

Fig. 1 is a block diagram showing an embodiment relating to a driver of a piezoelectric actuator according to the present invention.

In fig. 1, each of the plurality of piezoelectric actuators 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h is composed of a conductive plate 3 and a piezoelectric sheet (first piezoelectric sheet)5 and a piezoelectric sheet (second piezoelectric sheet 7) attached to opposite surfaces of the conductive plate 3, as shown in fig. 7A, in which electrodes 5a and 7A are provided on the opposite surfaces without contacting the plate 3 of each of the piezoelectric sheets 5 and 7, and the plate 3 serves as a common electrode for each of the piezoelectric sheets 5 and 7.

The electrodes 5a and 7a of the piezoelectric sheets 5 and 7 are connected to the positive terminal P1 and the negative terminal P2, and the plate 3 is connected to the common terminal P3 so as to be supported by a box-like casing 9 (not shown in the figure) in an open-ended shape as shown in fig. 8.

Note that in fig. 1, the piezoelectric actuators 1a to 1h are not shown, however, they are formed in the same manner as the piezoelectric actuator 1 of fig. 7.

As shown in fig. 8, the positive terminal feed line 19 and the negative terminal feed line 21 extend from the power supply section 15, and function to supply a positive DC power of about +50V to +100V and a negative DC power of about-50V to-100V. Therefore, common resistors Ra and Rb for current limiting are inserted and connected in series therebetween, respectively.

Corresponding to the piezoelectric actuators 1a to 1h, phototransistors Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8, whose emitters and collectors are connected in series with each other, are disposed.

Each collector of each of the phototransistors Q1, Q3, Q5 and Q7 is directly connected to the positive terminal feeder 19 on the power supply portion side of the common resistor Ra, without passing through the common resistor Ra.

Each emitter of the phototransistors Q2, Q4, Q6, and Q8 is connected to the negative terminal feed line 21 on the power supply portion side of the common resistor Rb.

The junction points of the phototransistors Q1 and Q2, Q3 and Q4, Q5 and Q6, and Q7 and Q8 are connected to the common terminal P3 of the piezoelectric actuators 1a, 1b, 1c to 1 h.

The positive terminals P1 of the piezoelectric actuators 1a, 1b, 1c to 1h are connected to the terminal Sa of the common resistor Ra of the power-supply-section-side positive-terminal feeder 19. Meanwhile, the negative electrode terminals P2 of the piezoelectric actuators 1a, 1b, 1c to 1h are connected to the terminal Sb of the common resistor Rb on the opposite side of the power supply section.

The designation marks Ca1 and Ca2 in fig. 1 correspond to equivalent capacitors (corresponding to C1 and C2 in fig. 7B) formed in the piezoelectric actuator 1 a. The same is true for designation markers Cb1, Cb2, Cc1, Cc2, and Ch1, Ch 2.

In the forward direction, the light emitting diodes D1 and D2, D3 and D4, D5 and D6, and D7 and D8 are connected in series. Thus, the light emitting diode D1 and the phototransistor Q1, the light emitting diode D2 and the phototransistor Q2, the light emitting diode D3 and the phototransistor Q3, the light emitting diode D4 and the phototransistor Q4, the light emitting diode D5 and the phototransistor Q5, the light emitting diode D6 and the phototransistor Q6, the light emitting diode D7 and the phototransistor Q7, and the light emitting diode D8 and the phototransistor Q8 are respectively placed adjacent to each other.

The light emitting diodes D1 and D2, D3 and D4, D5 and D6, and D7 and D8 are connected to the switching control section 25. Therefore, any one of the light emitting diodes D1 to D8 is switched and operated by the switching control section 25 so as to emit light.

The present invention is characterized in that the timings of the plurality of light emitting diodes D1 to D8 are sequentially selectively conductive-controlled by the switching control section 25.

Specifically, as shown in fig. 2, the switching control section 25 controls the plurality of piezoelectric actuators 1a to 1h by switching, in such a manner that the piezoelectric actuator 1a is on-controlled by applying a driving voltage thereto, and after a specific elapsed time period set previously, the piezoelectric actuator 1a (more appropriately, the piezoelectric patches 5 and 7) is off-controlled by turning off the driving voltage applied to the piezoelectric patch subjected to the on-control, at the same time, the next piezoelectric actuator 1b is on-controlled by applying the driving voltage, and then, at the same time, the driving voltage applied to the piezoelectric actuator 1b is off-controlled, and at the same time, the other next piezoelectric actuator 1c is on-controlled by applying the driving voltage, and thereafter, the control of the driving voltage is sequentially repeated.

Designated numeral 27 in fig. 1 denotes a controller 27 constituted by the above-described phototransistors Q1 to Q8, light emitting diodes D1 to D8, and a switching control section 25. In the controller 27, as described above, the switching control section 25 has a function of sequentially selectively switching and controlling the piezoelectric sheets 5 and 7 of each of the piezoelectric actuators 1a to 1h so as to apply the driving voltage from the feeder lines 19 and 21.

Fig. 3 shows the connection structure of the equivalent capacitors Ca1 to Ch2 and the controller 27 of the piezoelectric actuators 1a to 1h described above.

In fig. 1, the light emitting diodes D1 to D8 are connected by one line from the switching control section 25. However, in practice, the light emitting diodes D1 to D8 are connected by a single wiring so as to correspond to the light emitting diodes D1 and D2, D3 and D4, D5 and D6, and D7 and D8. Therefore, in the same manner as in fig. 10, any one of the light emitting diodes D1 to D8 is selected to allow light emission control.

Therefore, specifically, when only the control light emitting diode D1 is selectively turned on by the operation of the switch control section 25, the phototransistor Q1 is turned on by receiving light from the light emitting diode D1, and the piezoelectric sheet 5 (not shown in fig. 1, and similarly not shown hereinafter) of the piezoelectric actuator 1a is short-circuited by the positive drive voltage.

Meanwhile, positive and negative driving voltages are applied to both sides of the piezoelectric sheet 7 of the piezoelectric actuator 1a (not shown in fig. 1, and similarly not shown hereinafter), thereby charging the capacitor Ca2, and moving the open end of the piezoelectric actuator 1a in the upward direction (operation sheet 13).

Then, by switching the control section, the light emitting diode D1 is off-controlled, the operating phototransistor Q1 is turned off, and the piezoelectric sheet 7 of the piezoelectric actuator 1a is discharged, and the start end (the operating sheet 13) thereof is returned to the initial position.

When the light emitting diode D2 is selectively conduction-controlled only, the phototransistor Q2 is turned on by receiving light from the light emitting diode D2, and the piezoelectric sheet 7 of the piezoelectric actuator 1a is short-circuited by a negative driving voltage.

At the same time, positive and negative driving voltages are applied to both sides of the piezoelectric sheet 5 of the piezoelectric actuator 1a, the capacitor Ca1 is charged, and the open end thereof is moved in the downward direction (operation sheet 13).

Then, by the off control of the light emitting diode D2, the photo transistor Q2 is turned off and its open end (the operation piece 13) is returned to the initial position while discharging the piezoelectric sheet 5 of the piezoelectric actuator 1 a.

Next, for example, the operation of the driver of the piezoelectric actuator thus constituted when the piezoelectric actuators 1a to 1h are on-controlled in this order will be described.

When the switch control section 25 selectively conduction-controls only the light emitting diode D1, the phototransistor Q1 is turned on and the positive terminal driving voltage is applied from the feeder line 19 to the piezoelectric actuator 1a through the common resistor Ra, thereby short-circuiting the piezoelectric sheet 5 of the piezoelectric actuator 1a by the positive driving voltage.

At the same time, positive and negative driving voltages are applied to both sides of the piezoelectric sheet 7 of the voltage actuator 1a, thereby charging the capacitor Ca 2.

The switching control part 25 serves to turn off the control light emitting diode D1 after an elapsed time period for driving the piezoelectric actuator 1a and, at the same time, turn on the operating phototransistor Q3 by selectively conducting control of only the light emitting diode D3.

Therefore, in connection with the off control of the piezoelectric actuator 1a, the capacitor Ca2 of the piezoelectric actuator 1a is discharged, and at the same time, the piezoelectric patch 5 of the piezoelectric actuator 1b is short-circuited by the positive drive voltage, and the capacitor Cb2 is charged, thereby applying the positive and negative drive voltages to both sides of the piezoelectric patch 7 of the piezoelectric actuator 1 b.

At this time, as shown in fig. 3, the piezoelectric sheet 7 (capacitor Cb2) is charged, while the discharge current I mainly from the piezoelectric actuator 1a (capacitor Ca2) flows to the piezoelectric sheet 7 (capacitor Cb2) of the piezoelectric actuator 1b through the negative terminal feeder 21. Thereafter, forward, sequentially repeats from the next actuators 1c to 1 h.

Specifically, the control piezoelectric actuator 1a is turned on to charge the capacitor Ca2, and the control piezoelectric actuator 1a is turned off to discharge the capacitor Ca2 to generate the discharge current I. Therefore, the capacitor Cb2 of the piezoelectric actuator 1b of the next conduction control is charged by the discharge current I.

Then, the piezoelectric actuators 1a to 1h to be on-controlled are sequentially charged by a discharge current from the capacitor Ca2 of the piezoelectric actuator 1a that is off-operated just before the on-operation.

For this reason, the currents flowing through the common resistors Ra and Rb are made close to "0" or extremely small during the on/off switching control, so that the on/off switching requires less power from the positive or negative-pole terminal feeder lines 19 and 21.

Thereafter, by using a formula or the like, it is considered that the capacitors Ca1 to Ch2 of any other one of the piezoelectric actuators 1a to 1h are charged by the discharge current from the capacitors Ca1 to Ch2 of any one of the piezoelectric actuators 1a to 1h, which is the reason why the power supply from the positive or negative electrode terminal feeder lines 19 and 21 is less necessary.

To simplify this consideration, as shown in fig. 4, a two-sheet structure that drives only the piezoelectric actuators 1a and 1b in fig. 1 is considered.

Among them, the capacitors Ca1 and Ca2 of the piezoelectric actuator 1a and the phototransistors Q1 and Q2 that selectively turn on/off the control capacitors Ca1 and Ca2 are defined as a channel CH1, and the capacitors Cb1 and Cb2 of the piezoelectric actuator 1b and the phototransistors Q3 and Q4 that selectively turn on/off the control capacitors Cb1 and Cb2 are defined as a channel CH 2.

These channels CH1 and CH2 are provided independently, and either one of the phototransistor Q1 or Q2 or the phototransistor Q3 or Q4 is turned on to operate, and the energy balance in this case is as follows.

Specifically, energy obtained by subtracting "dissipated energy at resistors Ra and Rb" and "dissipated energy due to a shift in the polarity of the held energy" from "input energy" from the power supply E becomes capacitor held energy in the capacitors Ca1 to Cb 2.

In the case of the monolithic structure of the piezoelectric actuator 1a, if the operations of the phototransistors Q1 and Q2 are considered, the current path in fig. 4 is as shown in fig. 5A, where the current i is represented by formula 1.

[ equation 1]

The amount of energy dissipation at the resistors Ra and Rb is expressed by equation 2.

[ formula 2]

Wu+Wd＝2∫i²Rdt＝4CE²

The amount of energy input from the power source E is represented by equation 3.

[ formula 3]

2E∫idt＝4CE²

In addition, in the case of the two-piece structure of the piezoelectric actuators 1a and 1B, when the operation of the phototransistors Q1 and Q3 in which the current i is allowed to flow in the same direction is considered, the current path of fig. 4 is as shown in fig. 5B, and the current i is expressed by equation 4.

[ formula 4]

The amount of energy dissipation at the resistors Ra and Rb is represented by equation 5.

[ formula 5]

Wu+Wd＝2∫2ⁱ2Rdt＝8CE²

The amount of energy input from the power source E is represented by equation 6.

[ formula 6]

2E∫(2i)dt＝8CE²

In addition, in the case of the two-piece structure of the piezoelectric actuators 1a and 1b, when the operation of the phototransistors Q1 to Q4 in which the current i is allowed to flow in the opposite direction is considered, the current path is as shown in fig. 5C, and the current i is expressed by equation 7.

[ formula 7]

i＝δ(t)

The current i does not flow through the resistors Ra and Rb.

Therefore, the amount of energy dissipation at the resistors Ra and Rb is close to "0", and the amount of energy input from the power source E is represented by equation 8.

[ formula 8]

2E∫(2i)dt＝2E·2·2CE＝8CE²

As described above, from the consideration of the use formula, it is found that the energy during the on/off switching control of the piezoelectric actuators 1a and 1b moves directly between the piezoelectric actuators 1a and 1b without passing through the resistors Ra and Rb. The same is true for the piezoelectric actuators 1a to 1 h.

Therefore, energy movement between the piezoelectric actuators 1a and 1b during on/off switching control is increased, thereby improving transient characteristics and on/off switching performance of the entire apparatus, and in addition, the amount of energy dissipation (heat generation amount) at the resistors Ra and Rb is greatly reduced, and the power consumption of the entire apparatus can be reduced.

In this way, the driver of the piezoelectric actuator of the present invention has a plurality of piezoelectric actuators 1a to 1h each composed of a plate 3 and piezoelectric sheets 5, 7 attached to the opposite faces of the plate interposed between the piezoelectric sheets 5 and 7, and also has a controller 27 for selectively conducting and controlling one of them by connecting electrodes 5a and 7a of the opposite faces of the plate 3 of the piezoelectric sheets 5 and 7 of each of the piezoelectric actuators 1a to 1h to positive or negative terminal feeder lines 19 and 21, and in this case, charging the piezoelectric sheets 5 and 7 by applying a driving voltage to the piezoelectric sheets 5 and 7 of any one of the piezoelectric actuators 1a to 1h selected so as to conduct and control, from the positive or negative terminal feeder line 19 or 21 on the side of the plate 3.

In addition, the controller 27 has the following functions: the drive voltage applied to the piezoelectric sheets 5 and 7 of any one of the piezoelectric actuators 1a to 1h selected to be on-controlled is off-controlled, and at the same time, the piezoelectric sheets 5 and 7 of any other one of the piezoelectric actuators 1a to 1h to be on-controlled next are charged by turning on the drive voltage applied thereto.

Therefore, for example, when the piezoelectric actuator 1a is subjected to on control so as to charge the capacitor Ca2, and the piezoelectric actuator 1a is subjected to off control so as to discharge the capacitor Ca2, a discharge current flows, and by this discharge current, the capacitor Cb2 of the next piezoelectric actuator 1b to be on-controlled is charged.

Any one of the piezoelectric actuators 1a to 1h to be on-controlled is sequentially charged by a discharge current from any one of the capacitors Ca1 to Ch2 of any one of the piezoelectric actuators 1a to 1h to be off-controlled immediately before the on-control. Therefore, it is not necessary to supply too much charging current from the positive or negative terminal feeder lines 19 and 21, which tends to increase at the time of on/off switching.

Therefore, in the driver that drives the plurality of piezoelectric actuators 1a to 1h, the drive current during the on/off control of the piezoelectric actuators 1a to 1h can be greatly reduced, and therefore, the power consumption of the entire apparatus can be suppressed to be low.

In addition, the resistors R1 to R8 for current limiting, which are inserted for each of the piezoelectric actuators 1a to 1h, can be reduced to the common resistors Ra and Rb. Further, it is possible to use the resistors R1 to R8 having a small size at low cost and simplify wiring, achieving cost reduction and improving productivity. Note that the number of components can also be reduced by omitting the resistors Ra and Rb for current limiting.

In the present invention, any one of the piezoelectric actuators 1a to 1h is off-controlled to generate a discharge current, and any other one of the piezoelectric actuators 1a to 1h to be driven next is on-controlled by the discharge current from the capacitor. Therefore, it is preferable that the next conduction of any other one of the piezoelectric actuators 1a to 1h subjected to conduction control is scheduled simultaneously with or immediately after the off control of any one of the piezoelectric actuators 1a to 1h subjected to conduction control. In the transition, the piezoelectric actuators 1a to 1h are subjected to conduction control after being charged to a certain program, and this effect is halved.

Preferably, the controller 27 of the present invention has a function of on-controlling the piezoelectric sheets 5 and 7 of any other one of the piezoelectric actuators 1a to 1h to be driven next so that the driving voltage is applied at the timing of off-controlling the driving voltage applied to the piezoelectric sheets 5 and 7 of any one of the piezoelectric actuators 1a to 1 h.

Incidentally, as shown in fig. 6, the driver of the piezoelectric actuator according to the present invention may also be configured by connecting the phototransistors Q1, Q3, Q5 and Q7 to the positive-side feeder line 19 through the terminal Sa of the common resistor Ra on the opposite side of the power supply section, or connecting the phototransistors Q2, Q4, Q6 and Q8 to the negative-side feeder line 21 through the terminal Sb of the common resistor Rb on the opposite side of the power supply section. The other structure is the same as that of fig. 1, and the same effect can be obtained.

As described above, when the phototransistors Q1 to Q8 are connected to the positive and negative terminal feeder lines 19 and 21 through the common resistors Ra and Rb on the power supply portion side, the influence of the fluctuation of the power supply voltage on the phototransistors Q1 to Q8 is reduced during the on/off switching control of the phototransistors Q1 to Q8 (the piezoelectric actuators 1a to 1h), and it is preferable to easily achieve a stable operation.

Each of the above-described piezoelectric actuators 1a to 1h is arbitrarily configured, for example, may be composed of only the piezoelectric plates 3 and 5, or may have a plurality of piezoelectric plates 3 and 5 and the plate 3 may be laminated, and the support body is not limited to the structure of the above-described housing 9 of fig. 8.

The present invention is used to sequentially switch and control the piezoelectric sheets directly connected in common from the positive or negative terminal feeder lines 19 and 21, or sequentially control and switch the structures of the capacitors Ca1, Cb1, Cc1 and Ch1 or the capacitors Ca2, Cb2, Cc2 and Ch 2.

According to the present invention, the switching mechanism of the controller 27 for switching the driving power supply from the feeder line to the plurality of piezoelectric actuators 1a to 1h is not limited to the combination of the light emitting diodes D1 to D8 and the phototransistors Q1 to Q8 described above, but may be formed by a contactless switch for turning on and off the transistors of the power supply, and the switching control section 25 may be formed according to the switching mechanism.

Note that when the light emitting diodes D1 to D8 are combined with the phototransistors Q1 to Q8, it is easy to form an insulating state between the feeder lines 19, 21 and the controller 17 side, and thereby to achieve a stable operation.

The driver of the piezoelectric actuator according to the present invention is not limited to the driver for driving the knitting needle of the knitting machine as described above, but can be used as a driving source that mechanically moves mechanical parts directly or indirectly connected to a plurality of piezoelectric actuators having piezoelectric patches, such as an inkjet driving source and a dot-line driving source in a printer.

Claims (1)

1. A driver for a piezoelectric actuator constituted by a plurality of piezoelectric actuators in which first and second piezoelectric sheets are respectively attached to opposite surfaces of a plate interposed between the first and second piezoelectric sheets, comprising:

a plurality of piezoelectric actuators mechanically moving a mechanical part directly or indirectly connected to each piezoelectric actuator;

positive terminal feed lines connected directly to opposite sides of the first piezoelectric patch in common to the side attached to the board;

negative terminal feed lines connected directly to opposite sides of the second piezoelectric sheet to the side attached to the board in common;

a controller for applying a driving voltage to the first and second piezoelectric patches by selectively connecting the positive terminal or negative terminal feeder to an opposite side of the first or second piezoelectric patches to a side attached to the board, selectively turn on and control and charge the first or second piezoelectric patches,

wherein the controller has the following functions: the drive voltage applied to the first or second piezoelectric patch of each piezoelectric actuator selected to be on-controlled is turned off, and at the same time, the first or second piezoelectric patch of any other piezoelectric actuator to be on-controlled next is on-controlled to apply the drive voltage thereto, and a discharge current is allowed to flow from the first or second piezoelectric patch of any one piezoelectric actuator subjected to off-control, and by this discharge current, the first or second piezoelectric patch of any other piezoelectric actuator subjected to on-control is directly charged through the positive-terminal or negative-terminal feeder.