JPH053231B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrostrictive actuator device.

[Prior art and problems to be solved by the invention]

It is already known that pilot injection is effective in reducing the idle noise of diesel engines (hereinafter referred to as diesel engines).

Various attempts have been made to realize this pilot injection. In this attempt, the present inventors incorporated an electrostrictive element (for example, PZT) as an actuator in the injection path of a fuel injection pump.
Immediately after the start of fuel injection, this electrostrictive element is contracted to temporarily lower the pressure in the injection path to perform pilot injection.

The above-mentioned actuator (hereinafter referred to as an electrostrictive actuator) uses a ceramic material called PZT as an electrostrictive element, and stacks about 50 thin disc-shaped pieces (φ15 mm x t0.5 mm) of this material in a circular shape. It is columnar. When a voltage of about 500V is applied to the disk-shaped electrostrictive element in the thickness direction,
It stretches by about 0.5μm, so if you stack 50 of these and apply 500V in the thickness direction of each element, the overall
An elongation of about 25 μm can be obtained. If this voltage is removed or a slight negative voltage is applied, the material will shrink to the same extent and return to its original length. Furthermore, when an axial compressive load is applied to this electrostrictive actuator, each of the electrostrictive elements generates a voltage proportional to the compressive load as shown in FIG. A voltage of 500V is generated with a load of 500Kg. The properties of these electrostrictive actuators are known.

Conventionally, a high voltage power supply is connected to the electrostrictive actuator, and immediately after the start of fuel injection, the high voltage applied to the electrostrictive actuator is released or a negative voltage is applied to cause the electrostrictive actuator to contract. A pilot injection was performed. However, with this type of control method for electrostrictive actuators, it is necessary to install a DC high voltage generator externally, which poses the problem of complicating the power supply circuit and increasing costs, especially under in-vehicle conditions. Ta.

Next, when the present inventors short-circuited or shot the electrostrictive actuator that was generating voltage by applying a load, the electrostrictive actuator as a whole contracted in the axial direction as shown in FIG. 4.
In other words, when the electrostrictive actuator was shot with a load of 500 kg applied in the axial direction, a contraction of 25 μm occurred.

Therefore, the present inventors devised a drive circuit shown in FIG. 9 that simply shoots an electrostrictive actuator attached to the pump chamber of a fuel injection pump.
A thyristor 151 is connected to this circuit in parallel to the electrostrictive actuator 200 via a current limiting resistor 152 in series.

A diode 153 has its cathode side connected to the high voltage side and its anode side connected to the ground side, that is, in the opposite direction, to protect the electrostrictive actuator 200 from being applied with a reverse voltage. Thyristor 1
When a trigger signal enters the gate terminal 154 of 51,
The thyristor 151 becomes conductive and causes the electrostrictive actuator 200 to shoot and contract.

This state will be explained using the waveform diagram in FIG. 1st
1 shows the pressure in the pump chamber, and when the electrostrictive actuator 200 is in an open state, a voltage proportional to the pressure in the pump chamber is generated in the electrostrictive actuator 200 (FIG. 10, 3). When this generated voltage reaches a predetermined voltage (500V) greater than the valve opening pressure of the fuel injection nozzle, this is detected, a trigger signal is generated, and the thyristor 151 is made conductive. The electrostrictive actuator 200 then shoots, producing a contraction corresponding to the voltage generated at that time (500V).

As described above, this causes the pressure in the pump chamber to decrease and injection to be interrupted, so that pilot injection can be performed as shown in FIG. 10 and 4.

However, this electrostrictive actuator 20
In the method of simply shooting 0, the polarization of the electrostrictive actuator 200 deteriorates due to the load, and the voltage in the open state described above cannot be generated sufficiently, and as a result, the amount of expansion and contraction that realizes the form of pilot injection cannot be obtained. It disappears. Therefore, instead of shooting the electrostrictive actuator 200, an attempt was made to prevent polarization deterioration by having a capacitor absorb the voltage generated in the electrostrictive actuator 200, and then returning the charge stored in the capacitor to the electrostrictive actuator 200. The electrostrictive actuator device shown in FIG. 11 is composed of an electrostrictive actuator and its controller.

In this device, a coil 202 and a first thyristor 201 (anode side), which is a switching element, are connected in series to the high voltage side of an electrostrictive actuator 200, and the cathode side of the thyristor 201 is connected to a capacitor 300. A coil 204 and a second thyristor 203 in the opposite direction to the thyristor 201 are connected in series in parallel thereto. Further, a reverse voltage prevention diode 166 is connected in parallel to the electrostrictive actuator 200, and the first
The gates of the thyristor 201 and the second thyristor 203 are connected to pulse transformers 205 and 20, respectively.
It is connected to the control circuit C via 6.

In the device, the electric charge generated in the electrostrictive actuator 200 during the pressure feeding process of the fuel injection pump is
Control circuit C connects the first
By turning on the thyristor 201, the capacitor 300 is turned on, and the electrostrictive actuator 200
is contracted in the same manner as in the shot state, and a pilot injection is performed. Next, when the pump's pumping process is finished and before the next pumping process is started, the control circuit C turns on the second thyristor 203 via the pulse transformer 206.
The charge stored in the capacitor 300 is returned to the electrostrictive actuator 200 through the coil 204, thereby preventing polarization.

However, such an electrostrictive actuator device requires two thyristors, which are expensive switching elements, and two expensive pulse transformers, which is very disadvantageous in terms of cost.

The present invention is an electrostrictive actuator that can reduce the number of expensive switch elements used in an electrostrictive actuator device that functions as described above, and that can prevent polarization deterioration of the electrostrictive actuator while having a relatively inexpensive configuration. The purpose is to realize an actuator device.

[Means for solving problems]

In the present invention, as a basic form, there is provided an electrostrictive actuator device comprising an electrostrictive actuator that receives repeated loads and a controller that applies voltage to the electrostrictive actuator. A capacitor that can store the electric charge generated by the capacitor, a transformer that can electrically isolate the electrostrictive actuator and the capacitor, one of the terminals of which is grounded and conducts at a predetermined time to transform the capacitor into the capacitor. a switch element capable of charging the electric charge generated by the electrostrictive actuator through a device, and
An electrostrictive actuator device is provided that includes a current limiting element that can return the charge stored in the capacitor to the electrostrictive actuator.

[Effect]

In the electrostrictive actuator device as the basic form of the present invention, an inexpensive current limiting element is used instead of an expensive switch element in the circuit that returns charge from the capacitor to the electrostrictive actuator. Since one of the terminals of the switch element is grounded, there is no need to isolate the drive signal using a pulse transformer or the like, thereby simplifying the drive circuit and reducing costs. I can do it.

Furthermore, the electric charge generated in the electrostrictive actuator is temporarily stored in a capacitor by the action of the transformer and resonance circuit, and is returned to the electrostrictive actuator again when the electrostrictive actuator is not in operation, which prevents polarization deterioration of the electrostrictive actuator. It can also be prevented.

〔Example〕

An electrostrictive actuator device as an example of the basic form of the present invention is shown in FIG.

FIG. 2 shows a structure in which the electrostrictive actuator device shown in FIG. 1 is mounted on a distribution type fuel injection pump. A feature of this configuration is that the injection rate control device 7 is provided directly connected to the pump chamber 602 of the distributed fuel injection pump P.

First, the fuel injection pump P will be explained. A plunger 606, which is slidably supported within a cylinder bore 605 of a casing 604, rotates and reciprocates in synchronization with one-half of the engine speed. That is, the rotation of the engine is transmitted to a drive shaft (not shown) via gears or a timing belt,
The plunger 606 is rotationally driven coaxially by this drive shaft, and reciprocates as the face cam 607 engages with the roller 608. The face cam 607 is always urged to the left in the figure by a spring (not shown) and engages with the roller 608, and the reciprocating motion of the plunger 606 rotates around the axis and changes the shape of the cam surface of the face cam 607. This is done by following. The plunger 606 has one distribution port 609 and the same number of suction ports 610a, 610b as the number of engine cylinders formed on its outer periphery, and a pump chamber 602 is formed between the tip surface of the plunger 606 and the cylinder bore 605. .

The casing 604 is formed with a low pressure chamber 611, an intake passage 612 that communicates the low pressure chamber 611 with the cylinder bore 605, and a distribution passage 614 that allows each external injection valve 813 to communicate with the cylinder bore 605. The same number of distribution passages 614 as the number of engine cylinders are provided, and a delivery valve 615 is provided in each of the distribution passages 614 . Delivery valve 615 can be opened against spring 616, and has a function as a check valve and a suction valve.

However, the plunger 606 moves to the left and enters the pump chamber 6.
When 02 is inflated, either suction port 610
a or 610b is connected to the suction passage 612 and the fuel in the low pressure chamber 611 is sucked into the pump chamber 602. Conversely, when the plunger 606 moves to the right and the pump chamber 602 is pressurized, the distribution port 60
9 is connected to one of the distribution passages 614, and the fuel in the pump chamber 602 is delivered to the outside. Fuel delivery begins when the plunger 606 begins to move to the right, and ends when the plunger 606 moves further to the right and the spill port 617 opens into the low pressure chamber 611 from the right end surface of the spill ring 618.

Here, the spill port 617 refers to the plunger 6
06 is an opening for communicating between the pump chamber 602 and the low pressure chamber 611, and the spill ring 61
8 is a short cylindrical shape, through which the plunger 606 slides. The fixed position of the spill ring 618 can be changed by a lever 619, and the discharge amount of the pump chamber 602 can be changed depending on the position of the spill ring 618. The lever 619 is indirectly linked to the accelerator lever. The above is a description of the known parts.

Next, the injection rate control device will be explained.

The injection rate control device 7 is in the casing 720,
It is constructed by housing an electrostrictive actuator 200, a piston 722, a disc spring 723, and a distance piece 624 from the right in FIG. The casing 720 has a cylindrical shape with a bottom, that is, a bag shape, and is attached and fixed to the injection pump P by a male screw 729 at its open end.

The electrostrictive actuator 200 of this embodiment is formed by laminating about 50 thin disk-shaped (φ15 mm×t0.5 mm) electrostrictive elements to form a columnar shape, as in the conventional example. Therefore, this electrostrictive element is a ceramic material called PZT, whose main component is lead zirconate titanate, and when a voltage of about 500 V is applied in the thickness direction, it expands by about 0.5 μm. If 50 of these are stacked and 500V is applied in the thickness direction of each element, a total elongation of 25 μm can be obtained. If you release this voltage or apply a slight negative voltage, it will become 25μm.
undergoes contraction and returns to its original length.

Furthermore, when an axial compression load is applied to this electrostrictive actuator 200, a voltage as shown in Fig. 3 is generated in each electrostrictive element, that is, 500 kg.
A voltage of 500V is generated with a load of . Further, when the electrostrictive actuator 200 is shot with a load of 500 kg applied to the piston 722, a contraction of 25 μm occurs as shown in FIG. 4, which is the same as in the conventional example.

Operations such as application of voltage to the electrostrictive actuator 200 at a predetermined time, shooting, opening, etc. are controlled by a controller CONT, which is an external control means, via a lead wire 725.

The expansion and contraction action of the electrostrictive actuator 200 is transmitted to the piston 722, expanding the volume of the variable volume chamber 726 formed by the piston 722, the distance piece 624, and the casing 720 as a chamber wall.
to shrink. The disc spring 723 is located in the variable volume chamber 726 and biases the electrostrictive actuator 200 in the direction of contraction.

The distance piece 624 is disc-shaped,
It has a through hole 627 in its center. The diameter of the distance piece 624 is one size larger than the diameter of the piston 722, and when the external thread 729 of the casing 720 is tightened, the casing 720
and the casing 604 to form a seal. The variable volume chamber 726 has a through hole 6
It communicates with the pump chamber 602 via 27.

An O-ring 728 is disposed around the outer periphery of the piston 722 so that the pressure in the variable volume chamber 726 does not leak to the electrostrictive actuator 200 side via the piston 722.

To explain the operation in the above configuration, when no external voltage is applied to the electrostrictive actuator 200 and no shot is made, that is, when the electrostrictive actuator 200 is in an electrically open state, the pressure in the pump chamber 602 is This is the upper curve a in the diagram. The convex portion shown in FIG. 5 is the discharge stroke, that is, when the plunger 606 is moving to the right and the spill port 617 is covered by the spill ring 618. Among these, the portion higher than the valve opening pressure of the injection valve 813 is the portion that contributes to injection. That is, during this period, the injection valve 813 is open;
Its opening lift is proportional to its pressure. Therefore, the injection amount is also roughly proportional to the pressure.

Further, an electric charge proportional to the pressure in the pump chamber 602 is generated in the electrostrictive actuator 200, and a voltage as shown in FIG. 3 is generated. In addition, in order to convert the pressure in the pump chamber to the compression load shown in FIG.
In the case of Fig. 2, the pressure receiving area of the piston 722 is about 4 cm ² and the opening pressure of the injection valve 813 is set to 100 kg/cm ² , so the injection starts. At times, the voltage generated by the electrostrictive actuator 200 is 400V.

In addition, the controller CONT detects that the voltage generated in the electrostrictive actuator 200 has further increased.
When the voltage reaches 500V, that is, at a predetermined time immediately after the injection valve 813 starts injection, the electrostrictive actuator 200 is shot and the generated voltage is
Control the voltage to drop to 0V.

At this time, the electrostrictive actuator 200 contracts by 25 μm as shown in FIG. 4, so the variable volume chamber 726 expands by 4 cm ² ×25 μm=10 mm ³ .
Therefore, the pressure in the pump chamber 602 decreases and the pressure in the injection valve 8 decreases.
The injection pressure from 13 decreases. Alternatively, the pressure in the pump chamber 602 becomes the lower curve b in FIG.
In the case described below, the injection from the injection valve 813 is temporarily interrupted to realize a pilot injection mode.

Here, the larger the amount of contraction of the electrostrictive actuator 200, the more pronounced the drop in pump chamber pressure becomes, so the pilot injection becomes clearer, and the interval between the pilot injection and the main injection can be widened, which reduces noise. The effect on vibration reduction becomes significant. In the device shown in FIG. 1, electric charge is stored in a capacitor (described later) from an electrostrictive actuator 200,
The aim is to increase the amount of contraction of the electrostrictive actuator by reusing that charge, thereby increasing the effectiveness of pilot injection.

In addition, when an electrostrictive element is subjected to repeated loads, its polarization gradually deteriorates, the amount of expansion and contraction decreases, and there is a possibility that it will not be possible to realize the form of pilot injection.
In the device shown in FIG. 2, charge from the electrostrictive actuator 200 is stored in a capacitor, and a portion of the charge is returned to the electrostrictive actuator 200, thereby making it possible to prevent polarization deterioration.

Next, driving of the electrostrictive actuator in the apparatus shown in FIG. 1 will be explained.

Part A of FIG. 1 shows the circuits of the main parts of the electrostrictive actuator and its controller in the electrostrictive actuator device of the present invention. The primary coil 163 of the insulating transformer 162 and the thyristor 16 are connected to the high voltage side of the electrostrictive actuator 200.
1 (on the anode side) are connected in series, and a reverse voltage prevention diode 166 is connected in parallel with the electrostrictive actuator 200. On the other hand, the secondary coil 164 of the isolation transformer 162, the resonance coil 165, the diode 167, and the capacitor 300 constitute a series resonant circuit, and the high voltage side of the capacitor 300 is connected to the electrostrictive actuator via a high resistance resistor 168. 200 is connected to the high voltage side.

When the voltage generated by the electrostrictive actuator 200 reaches a predetermined voltage higher than the valve opening pressure, the thyristor 16
A trigger signal is sent to the gate terminal 171 of No. 1 (FIG. 6, 2). As a result, the thyristor 161 becomes conductive, and the electric charge of the electrostrictive actuator 200 is discharged through the primary coil 163 of the transformer 162. If the turns ratio of the transformer 162 at this time is 1:1, the voltage drop of the electrostrictive actuator 200 (for example, 500 V) is applied to both ends of the secondary coil 164.
is induced. This voltage is applied to the resonant coil 165,
Power is stored in the capacitor 300 through the diode 167. In other words, the electric charge generated in the electrostrictive actuator 200 is transferred to the capacitor 300.
As a result, the electrostrictive actuator 2
00 is deflated. Here, the diode 167 allows the electric charge stored in the capacitor 300 to be transferred to the transformer 16.
It serves to prevent release through 2.

At this time, as described above, the pressure in the pump chamber 602 decreases due to this contraction, resulting in a pilot injection state (FIG. 6, 4). Next, the electric charge stored in the capacitor 300 is gradually returned to the electrostrictive actuator 200 via the resistor 168 during the period between the end of the pumping stroke of the pump chamber and the start of the next pumping stroke. . Then, when the voltage of the capacitor 300 and the voltage of the electrostrictive actuator become equal, an equilibrium state is reached. That is, a charge corresponding to about 250V is returned to the electrostrictive actuator 200. When the next pumping stroke begins, the voltage generated in the electrostrictive actuator 200 becomes the sum of the 250V offset voltage and the voltage generated by the compressive load shown in FIG. 3. Therefore, compared to the conventional circuit that simply shoots, the voltage has increased from 500V to 750V (see Figure 6, 3), so the amount of contraction can be increased by 1.5 times, and as mentioned above, the amount of contraction can be increased by 1.5 times. Not only can the effect be enhanced, but also polarization deterioration can be prevented.

The controller CONT in the apparatus shown in FIG. 1 will be described below. A first comparator 101 has a terminal voltage of the electrostrictive actuator 200 divided by resistors 102 and 103 and is connected to a non-inverting input. A reference voltage (VR1) 104 is connected to the inverting input, and when the terminal voltage of the electrostrictive actuator 200 becomes 750V or more, the output of the first comparator 101 becomes "1" level. The output of the first comparator 101 is connected to a rising trigger input of a retriggerable first one-shot multi 105.

The output pulse width of the first one-shot multiplier 105 is determined by a capacitor 106 and a resistor 107. In the apparatus shown in FIG. 1, this pulse width is set to be slightly longer (approximately 15 msec) than the pump pressure stroke period during idle rotation.

The reason for this is that when the load is high, the pumping period becomes longer and the pumping pressure increases, so even after the first shot for pilot injection, the voltage generated by the electrostrictive actuator exceeds the reference voltage (VR1) mentioned above. This is to prevent the user from doing the shooting operation multiple times.

That is, during the signal generation period of the first one-shot multi 105, unnecessary signals are masked. The Q output of the first one-shot multi 105 is connected to the rising trigger input of the second one-shot multi 108. The output pulse width of the second one-shot multi 108 is the capacitor 10.
9, determined by resistor 110. Since this pulse width is a trigger signal for the thyristor 161, it may be short, and is set to about 30 μs. The output of the second one-shot multi 108 is at the "0" level during this 30 μs.

The voltage generated by the electrostrictive actuator 200 divided by the resistors 102 and 103 is also connected to the non-inverting input of the second comparator 140. A reference voltage (VR2) 141 is connected to the inverting input, and the terminal voltage of the electrostrictive actuator 200 is
When the voltage exceeds 600V, the output of the second comparator 140 becomes "1" level.

The output of the second comparator 140 is connected to a rising trigger input of a retriggerable third one-shot multi 142. The output pulse width of the third one-shot multi 142 is determined by a capacitor 143 and a resistor 144. This pulse width is the pump pumping cycle when the engine speed is 1200 rpm,
In other words, for a 4-cylinder engine, it is set to 25 msec.

The output of the third one-shot multi 142 is connected to the D input of the D flip-flop 145.
It is connected to the D input of the D flip-flop 145, and the output of the second comparator 140 is connected to the clock input C of the D flip-flop 145. The output of the D flip-flop 145 is connected to one input of a two-input OR circuit 152.

500 is a potentiometer that moves in conjunction with an accelerator pedal (not shown) and outputs a voltage signal according to the load. This signal is the third comparator 1
50 non-inverting inputs. A reference voltage (VR3) 151 is connected to the inverting input.
For example, when the accelerator opening is 10% or more, the output of the third comparator 150 becomes "1" level.

The output of the third comparator 150 is connected to the other input of a two-input OR circuit 152. 2
The output of the input OR circuit 152 is connected to the reset input R of the second one-shot multi 108, and when the output of the two-input OR circuit 152 is at the "1" level, the second one-shot multi is reset, so that the trigger is not activated. No signal is generated.

The operation of the controller CONT in the above configuration will be described below. Now, if we consider low rotation and low load, the cam lifts as the pump drive shaft rotates, and the pressure in the pump chamber 602 increases. Accordingly, the electrostrictive actuator 200 is pressurized and a voltage is generated. The initial value of this voltage is because charge was supplied from the capacitor 300 last time.
It will rise from 250V. The voltage generated by the electrostrictive actuator is divided by resistors 102 and 103 and compared with a reference voltage (VR1) by a first comparator 101. When the terminal voltage of the electrostrictive actuator exceeds 700V (Fig. 6, 3), the output of the first comparator 101 becomes "1" level,
Trigger the first one shot multi 105. The second one-shot multi 108 is triggered by the rise of the output of the first one-shot multi 105,
A trigger signal with a negative pulse width of approximately 30 μs is output from the output. This signal is resistor 11
Since the transistor 113 is turned on through the resistor 1,112, a current is supplied to the gate terminal 171 of the thyristor 161 through the resistor 114 for a period of 30 μs.
1 is conductive, and the electric charge of the electrostrictive actuator 200 flows out through the transformer 162 to a series resonant circuit consisting of a coil 165, a capacitor 300, and the like. At this time, if the transformer 162 is an ideal transformer and the turns ratio is 1:1, the charge equivalent to the voltage drop (approximately 500 V) of the electrostrictive actuator 200 will be stored in the capacitor 300, and at the same time, the electrostrictive actuator shrinks to about 25 μm. As a result, as described above, the pressure in the pump chamber 602 drops below the valve opening pressure (FIG. 6, 1), and fuel injection is interrupted (FIG. 6, 4).

At this time, since the cam lift is in the middle of the lift, fuel is further pumped to the pump chamber 60.
The pressure at No. 2 rises again and restarts injection. Before the cam lift reaches top dead center, the spill port 61 mentioned above
7 opens, pump chamber pressure spills and injection ends. At this time, the terminal voltage of the electrostrictive actuator 200 tries to decrease to a negative voltage as shown by the broken line in FIG. This negative voltage, that is, reverse voltage, is shunted out and protected by a diode 166.

When one pressure feeding stroke of the pump chamber is completed, the terminal voltage of the electrostrictive actuator 200 becomes 0V, while the voltage of the capacitor 300 becomes 500V. this
The electric charge equivalent to 500V is slowly returned to the electrostrictive actuator 200 via the resistor 168, and eventually, the electric charge equivalent to about 250V, which is half of the electric charge, is stored in the electrostrictive actuator 200. Here, the value of the resistor 168 is determined by the value of the electrostrictive actuator 200 during the pump pressure stroke as described above.
The value must be large enough that the electric charge generated in the resistor 168 does not easily flow into the capacitor 300 through the resistor 168.

Next, a method of not controlling the electrostrictive actuator 200 according to engine operating conditions will be described. Even if pilot injection is performed at high loads or high speeds, it will have little effect on noise and vibration, and if pilot injection is performed, the injection rate will decrease, and the engine output will actually decrease, so the electrostrictive actuator 200 No control is provided. For example, when the load is high, the output voltage of the potentiometer 500 becomes high, and when the load is higher than the set load, the output of the third comparator 150 becomes "1" level. This signal is passed through a two-input OR circuit 152 to the second one-shot multi 108
Reset. That is, when the load is high, no trigger signal is generated from the second one-shot multi 108, so the electrostrictive actuator 200 is not controlled and remains open. The same applies to the engine rotation speed, and the output of the second comparator 140 becomes "1" level every time the pump pumps the pump, but if this cycle becomes shorter than the output pulse width of the third one-shot multi 142 of 25 ms,
The Q output of the D flip-flop 145 becomes "1" level, and the second one-shot multi 108 is reset through the two-input OR circuit 152. Therefore, no trigger signal is generated, and the electrostrictive actuator 200 is no longer controlled.

In the apparatus shown in FIG. 1, the electrostrictive actuator 200 can be controlled without requiring an external high-voltage power supply, and moreover, compared to a method in which the electric charge generated in the electrostrictive actuator 200 is simply shot, The electric charge is stored in the capacitor 300 by the action of the resonant circuit, and is reused during expansion to increase the amount of contraction. Therefore, the effect of pilot injection can be increased, noise and vibration can be reduced, and repeated loads can be reduced. It is also possible to prevent polarization deterioration of the electrostrictive actuator 200 due to

In carrying out the present invention, embodiments other than those described above may be considered. For example, a second embodiment is shown in FIG. This embodiment is characterized in that a diode 169 is added between the capacitor 300 and the resistor 168 of the previous embodiment. By adding this diode 169, the electrostrictive actuator 20 is connected through the resistor 168 during the pump pressure stroke.
Since it is possible to prevent charges that may flow into the capacitor 300 from zero, it is possible to widen the selection range of the resistance value of the resistor 168.

Furthermore, as shown in FIG. 8 as a third embodiment, a configuration in which a transistor 170 is used instead of the thyristor 161 is also conceivable. or,
It can also be realized by using a relay or the like (not shown) instead of the thyristor 161.

〔Effect of the invention〕

According to the present invention, the number of expensive switch elements used can be reduced, and since one of the terminals of the switch element used is grounded, its drive signal can be isolated by a pulse transformer or the like. Therefore, it is possible to simplify the drive circuit and reduce costs.

Further, according to the present invention, the electric charge generated in the electrostrictive actuator is temporarily stored in the capacitor by the action of the transformer and the resonant circuit, and is returned to the electrostrictive actuator again when the electrostrictive actuator is not in operation. The amount of contraction of the actuator can be increased, and polarization deterioration of the electrostrictive actuator 200 can be prevented.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an electrostrictive actuator device as an embodiment of the basic form of the present invention, and Fig. 2 shows a configuration when the actuator device shown in Fig. 1 is installed in a distribution type fuel injection pump. Figures 3 and 4 are characteristic diagrams showing the relationship between the generated voltage and the amount of contraction during shot with respect to the compressive load in the electrostrictive actuator, and Figure 5 is a waveform diagram illustrating the operation of the electrostrictive actuator. Fig. 6 is a waveform diagram explaining the operation of section A of the electrostrictive actuator device shown in Fig. 1, Fig. 7 is a circuit diagram showing the second embodiment, and Fig. 8 shows the third embodiment. Circuit diagram, No. 9
The figure shows a drive circuit for an electrostrictive actuator in the prior art, FIG. 10 is a waveform diagram explaining the operation of the circuit in FIG. 9, and FIG. 11 shows a control means for an electrostrictive actuator device in another prior art. It is a circuit diagram showing the main parts. 101... Comparator, 105... One shot multi, 108... One shot multi, 140...
Comparator, 142...One shot multi, 1
45...D flip-flop, 150...comparator, 161...thyristor, 162...insulation transformer, 165...coil, 166, 167, 169...
Diode, 168... Current limiting element, 170... Transistor, 200... Electrostrictive actuator, 3
00...capacitor, 500...potentiometer,
602...Pump chamber, 604...Casing, 605
...Cylinder bore, 606...Plunger, 607...
Face cam, 608...roller, 609...distribution port, 610a, 610b...suction port, 611
...Low pressure chamber, 612...Suction passage, 614...Distribution passage, 615...Delivery valve, 616...Spring, 617
... Spill port, 618... Spill ring, 619
... lever, 624 ... distance piece, 7 ... injection rate control device, 720 ... casing, 722 ... piston, 723 ... disc spring, 725 ... lead wire, 7
26...Variable volume chamber, 728...O ring, 729...
Male thread, 813...Injection valve, 814...Distribution passage, P
...Fuel injection pump.

Claims (1)

[Scope of Claims] 1. An electrostrictive actuator device comprising an electrostrictive actuator that receives repeated loads and a controller that applies voltage to the electrostrictive actuator, wherein the controller controls the generation of the electrostrictive actuator. a transformer that can electrically isolate the electrostrictive actuator and the capacitor; one of the terminals is grounded and conducts at a predetermined time to connect the transformer to the capacitor; a switch element capable of charging the electric charge generated by the electrostrictive actuator through the electrostrictive actuator; and a first current limiting element capable of returning the electric charge stored in the capacitor to the electrostrictive actuator. An electrostrictive actuator device featuring: 2. The device according to claim 1, wherein a first rectifying element is interposed between the transformer and the capacitor to prevent charge from flowing into the capacitor. 3 between the transformer and the capacitor.
3. The device according to claim 1 or 2, wherein a current limiting element is provided. 4. The device according to claim 3, wherein the second current limiting element is a coil having an inductance. 5. The device according to claim 1, wherein the switch element is a thyristor. 6. The device according to claim 1, wherein a second rectifying element is inserted into a conductive path including the first current limiting element between the capacitor and the electrostrictive actuator. 7. The device according to claim 1, wherein the switch element is a transistor. 8. The device according to claim 1, wherein the repetitive load is a load caused by hydraulic pressure of a jerk-type hydraulic pump.