JPS6244813A - Electric distortion type actuator device and diesel engine fuel injection device using its device - Google Patents

Abstract

PURPOSE:To prevent the deterioration in polarization with an inexpensive consti tution by forming a capacitor for accumulating electric charge generated by an electric distortion type actuator, a switch for discharging the charge and a current restricting element. CONSTITUTION:A control means (driving circuit) in the electric distortion type actuator 200 connects a serial connection body consisting of a coil 163 and a thyristor 161 to be a switching element to the capacitor 300 and connects a serial connection body consisting of a resistor 164 and a diode 162 in parallel with said serial connection body. When the thyristor 161 is connected, a serial resonance circuit consisting of the actuator 200, the coil 163 and the capacitor 300 is formed and charge generated by the actuator 200 is transferred to the capacitor 300 and cotracted. Then, the charge accumulated in the capacitor 300 is gradually returned to the actuator 200 through the diode 162 and the resistor 164 to impress 200V voltage. Since 200V voltage is previously impressed always when a load is applied to the actuator 200, the deterioration of polarization can be interrupted.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrostrictive actuator device and a fuel injection device for a diesel engine using this device. It is attached to a fuel injection pump and is used to achieve pilot injection, which is effective in reducing idle noise in diesel engines.

[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 installed an electrostrictive element (for example, PZT) as an actuator in the injection path of a fuel injection pump, and contracted the electrostrictive element immediately after the start of fuel injection to temporarily lower the pressure in the injection path. In the past, pilot injection was performed using the following methods.

The above-mentioned actuator (hereinafter referred to as electrostrictive actuator) uses a ceramic material called PZT as an electrostrictive element, and a thin disc-shaped (φ15X t O
, 5) About 50 pieces of n+m pieces are laminated to form a cylindrical shape. The disc-shaped electrostrictive element has a voltage of 500V in the thickness direction.
If a certain voltage is applied, the element will elongate by about 0.5 μm, so if 50 of these are stacked and 500 V is applied in the thickness direction of each element, the overall elongation will be about 25 μm. If this voltage is removed or a slight negative voltage is applied, the same degree of shrinkage will occur and the original length will be restored. 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 500 V is generated with a load of 500 kg. The properties of these electrostrictive actuators are known.

Conventionally, a high voltage power source 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 contract it, and pilot injection is performed. I was letting it happen. However, such a control method for an electrostrictive actuator has a problem in that the cost of an externally installed high voltage generator is high.

Next, the inventors short-circuited the electrostrictive actuator, which generates voltage by applying a load, and as a result, the entire electrostrictive actuator shrank in the axial direction as shown in Figure 4. occured. That is, when the electrostrictive actuator was short-circuited while a load of 500 mm +r was applied in the axial direction, a reduction of 25 μm occurred.

Therefore, the inventors of the present invention devised a drive circuit shown in FIG. 9 in which the electrostrictive actuator attached to the pump chamber of the fuel injection pump is simply short-circuited.

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, ie, in the opposite direction, to protect the electrostrictive actuator 200 from being applied with a reverse voltage. When a trigger signal is input to the gate terminal 154 of the thyristor 151, the thyristor 151 becomes conductive and short-circuits the electrostrictive actuator 200, causing it to contract.

This state will be explained using the waveform diagram in FIG. Figure 10 (2
) indicates the pressure in the pump chamber, and when the electrostrictive actuator 200 is in the open state, a voltage proportional to the pressure in the pump chamber is generated in the electrostrictive actuator (Fig. 10 (
4)). When this generated voltage reaches a predetermined voltage (500V) greater than the nozzle opening pressure, this is detected, a trigger signal is generated, and the thyristor 151 is made conductive. Then, the electrostrictive actuator 200 will be affected by the generated voltage (5
00v).

For this reason, the pressure in the pump chamber decreases and injection is interrupted, so that pilot injection can be performed as shown in FIG. 10 (5), as described above.

However, if the electrostrictive actuator 200 is simply short-circuited, 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 (as a result, the pilot injection pattern Therefore, instead of shorting the electrostrictive actuator 200, the voltage generated in the electrostrictive actuator 200 is absorbed into a capacitor.
The electrostrictive actuator device shown in FIG. 11, which includes an electrostrictive actuator and its control means, attempts to prevent polarization deterioration by returning the charge stored in the capacitor to the electrostrictive actuator 200.

In this device, a coil 163 is provided on the high voltage side of the electrostrictive actuator 200, and a first thyristor 1 which is a switching element is provided.
61 are connected in series and connected to the capacitor 300. Coil 165 and the thyristor 1 are connected in parallel with this.
A second thyristor 168 having a polarity opposite to that of 61 is connected. Further, a reverse voltage prevention diode 166 is connected in parallel to the electrostrictive actuator 200, and a thyristor 1
The gates of thyristor 61 and second thyristor 168 are connected to control circuit C via pulse transformers PTI and PT2, respectively.

In the device, the electric charge generated in the electrostrictive actuator 200 during the pressure feeding process of the fuel injection pump is transferred to the capacitor 300 by the control circuit C turning on the thyristor 161 via the pulse transformer PTI, and the electric charge is transferred to the electrostrictive actuator 200. is contracted in the same manner as in a short-circuit condition, and 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 168 via the pulse transformer PT2, thereby reducing the amount of energy stored in the capacitor 300. Charge is returned to the electrostrictive actuator 200 through the coil 165 to prevent polarization degradation.

However, such an electrostrictive actuator device
The configuration uses two thyristors, which are expensive switching elements, and two expensive pulse transformers, which is very disadvantageous from a cost standpoint.

The present invention provides an electrostrictive actuator device that can reduce the number of expensive elements used in an electrostrictive actuator device that functions as described above, has a relatively inexpensive configuration, and can prevent polarization deterioration of the electrostrictive actuator, and the electrostrictive actuator device. The purpose is to realize a fuel injection device for diesel engines using this device.

[Means for solving problems]

An electrostrictive actuator device according to a basic form of the present invention that achieves the above object is an electrostrictive actuator that is installed in a place that receives repeated loads, generates a voltage in response to compressive loads, and expands and contracts in accordance with the applied voltage. , a control means for applying a voltage to the electrostrictive actuator, and the control means includes a capacitor capable of storing electric charge generated by the electrostrictive actuator; The electrostrictive actuator includes a switch element that can charge the electric charge generated by the electrostrictive actuator, a current limiting element that can return the electric charge stored in the capacitor to the electrostrictive actuator, and a control circuit that makes the switch element conductive at a predetermined time. It is characterized by

Further, a fuel injection device for a diesel engine using the electrostrictive actuator device according to another aspect of the present invention is formed by a cylinder bore of a fuel injection pump and a plunger slidably fitted into the cylinder bore. In a fuel injection device for a diesel engine, which introduces fuel into a pump chamber and changes the volume of the pump chamber to pressurize the fuel and inject it from an injection valve, the pump chamber receives repeated loads and generates a voltage. , a variable volume chamber whose volume can be changed by an electrostrictive actuator that expands and contracts in accordance with an applied voltage is connected to the variable volume chamber, and a control means for applying a voltage to the electrostrictive actuator is connected, and the control means is connected to the electrostrictive actuator. a switching element capable of charging the capacitor with the charge generated by the electrostrictive actuator; and a current limiting element capable of returning the charge stored in the capacitor to the electrostrictive actuator. The present invention is characterized in that it includes a control circuit that turns on the switch element at a predetermined time when the fuel pressure in the pump chamber exceeds a certain pressure.

〔Example〕

Embodiments of the apparatus of the present invention will be described below with reference to the accompanying drawings.

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. This structural feature is that the pump chamber 6 of the distribution type fuel injection pump P
02, an injection rate control device 7 is provided.

First, the fuel injection pump P will be explained. Casing 6
A plunger 606, which is slidably supported within a cylinder bore 605 of the engine 04, 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 the face cam 607 is rotated by the roller 6.
08, it reciprocates. The face cam 607 is always biased to the left in the figure by a spring (not shown) and is engaged with the roller 60B, and the reciprocating motion of the plunger 606 rotates around the axis and causes the cam surface of the face cam 607 to rotate. This is done by following the shape of .

Plunger 606 has one distribution port 60 on its outer circumference.
9 and the same number of intake bows as the number of engine cylinders) 610a.

610b is formed, and a pump chamber 602 is formed between the tip surface of the plunger 606 and the cylinder bore 605.

The casing 604 includes a low pressure chamber 611 and a low pressure chamber 61.
1 and a suction passage 612 communicating with the cylinder bore 605;
A distribution passage 614 is formed 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 61
5 can be opened against a spring 616, and has a function as a check valve and a suction valve.

However, when the plunger 606 moves to the left and the pump chamber 602 expands, one of the suction bows 1-610 is connected to the suction passage 6.
12 and the fuel in the low pressure chamber 611 flows into the pump chamber 602.
On the contrary, when the plunger 606 moves to the right and the pump chamber 602 is pressurized, the distribution port 609 is connected to one of the distribution passages 614, and the fuel in the pump chamber 602 is discharged to the outside. will be sent to. Fuel is delivered by plunger 6
Starts when 06 starts moving to the right, Sara Banko Plunger 6
06 moves to the right, spill port 617 spill ring 61
The process ends when the right end surface of 8 is opened into the low pressure chamber 611.

Here, the spill port 617 is an opening provided in the plunger 60G to communicate between the pump chamber 602 and the low pressure chamber 611, and the spill ring 618 has a short cylindrical shape, and the plunger 606 It is something that slides. The spill ring 618 can change its fixing position with a lever 619.
The discharge amount of the pump chamber 602 can be changed depending on the position of the pump chamber 602. The lever 619 is indirectly linked to the accelerator lever. The following is an explanation of publicly known parts.

Next, the injection rate control device will be explained.

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

The electrostrictive actuator 200 of this embodiment is made into a cylindrical shape by stacking about 50 thin disk-shaped (φ15×tO, 5) mm electrostrictive elements, 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, the
It stretches about m. If 50 of these are stacked and 500 μm is applied in the thickness direction of each element, an elongation of 25 μm can be obtained as a whole. If this voltage is removed or a slight negative voltage is applied, the film will shrink by 25 μm and return to its original length.

Furthermore, when an axial compressive load is applied to this electrostrictive actuator 200, a voltage as shown in Fig. 3 is generated in each electrostrictive element, that is, 500 lb
voltage is generated. Furthermore, 500 kg is added to the piston 722.
The electrostrictive actuator 20 is
As shown in FIG. 4, when 0 is shorted, a reduction of 25 μm occurs, which is the same as in the conventional example.

Operations such as applying voltage to the electrostrictive actuator 200 at a predetermined time, shorting, opening, etc. are performed using the lead wire 725.
It is controlled by a controller C0NT which is an external control means.

The expansion and contraction action of the electrostrictive actuator 200 is performed by the piston 72.
2, the piston 722 and the distance piece 6
24 and the casing 720 as chamber walls, the volume of the variable volume chamber 726 is expanded/reduced. The disc spring 723 is located in the variable volume chamber 726 and is connected to the electrostrictive actuator 2.
00 is biased in the direction of reduction.

The distance piece 624 is disc-shaped and has a through hole 627 at its center. distance piece 6
The diameter of the piston 24 is one rotation larger than the diameter of the piston 722, and when the male screw 729 of the casing 720 is tightened, the piston 720 is sandwiched between the casing 720 and the casing 604 to form a seal. The variable volume chamber 726 communicates with the pump chamber 602 via a through hole 627.

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 short circuit occurs, that is, when it is electrically opened, the pressure in the pump chamber 602 is The upper curve in the figure (al).

The convex part shown in FIG. 5 is the discharge stroke, that is, the plunger 606 moves to the right and the spill boat 617
, is covered by a 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 and 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 the voltage shown in FIG. 3 is generated.

In addition, in order to convert the pressure in the pump chamber 602 into the compression load shown in FIG. 3, it is sufficient to multiply the pressure by the pressure-receiving area of the piston 722. In the case of FIG. 2, the pressure-receiving area of the piston 722 is about 4 cJ. , the opening pressure of the injection valve 813 is 100 kg.
/cJ, the voltage generated by the electrostrictive actuator 200 at the start of injection is 400V.

In addition, the controller C0NT is an electrostrictive actuator 20.
When the voltage generated at 0 further increases and reaches 500V, that is, at a predetermined time immediately after the injection valve 813 starts injection, the electrostrictive actuator 200 is short-circuited to reduce the generated voltage to Ov. to control.

At this time, the electrostrictive actuator 200 shrinks by 25 μm as shown in FIG.
cJX 25 /'m= 1 (This causes expansion of ln3. Therefore, the pressure in the pump chamber 602 decreases and the injection valve 813
The injection pressure from Alternatively, the pressure in the pump chamber 602 becomes (in the lower curve in FIG. 5). In the case described below, the injection from the injection valve 813 is temporarily interrupted to realize a pilot injection mode.

Here, since the electrostrictive actuator is subjected to repeated loads, the polarization deteriorates and the amount of expansion and contraction gradually decreases, and as a result, there is a possibility that the pilot injection mode cannot be realized. However, in the configuration of the present invention, the controller C0NT
Since the electric charge stored in the capacitor included in the device (FIG. 1) is returned to the electrostrictive actuator, the electrostrictive actuator whose polarization has deteriorated can be polarized again and pilot injection can be performed.

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

Part A in FIG. 1 shows the electrostrictive actuator in the electrostrictive actuator device of the present invention and a drive circuit that is the main part of its control means. Electrostrictive actuator 2
A coil 163 and a thyristor 161, which is a switching element, are connected in series to the high voltage side of 00, and are connected to a capacitor 300. In parallel with this is a resistor 164 and a diode 16.
2 connected in series are connected. Further, a reverse voltage prevention diode 166 is connected antiparallel to the electrostrictive actuator 200.

When the voltage generated by the electrostrictive actuator 200 reaches a predetermined voltage higher than the valve opening pressure, a trigger signal is sent to the gate terminal 167 of the thyristor 161 (FIG. 6 (2)). This causes the thyristor 161 to conduct. In this state, the electrostrictive actuator 200, the coil 163, and the capacitor 30
A series resonant circuit consisting of zero is formed, and the electric charge generated in the electrostrictive actuator 200 is transferred to the capacitor 300, so that the electrostrictive actuator 200 becomes like a short circuit and contracts.

At this time, as mentioned above, the pressure in the pump chamber decreases due to this contraction, creating a pilot injection state (
Figure 6 (4)). Next, the electric charge stored in the capacitor 300 is slowly returned to the electrostrictive actuator 200 via the diode 162 and the resistor 164 during the period when the pump's pumping stroke ends and the next pumping stroke starts. Balance occurs when the voltages of the capacitor 300 and the electrostrictive actuator become equal. If the voltage stored in the capacitor was 400V, 200V would be returned to the electrostrictive actuator. After that, the next pumping stroke starts, but at this time, the voltage of the electrostrictive actuator 200 is already 200V, so the voltage increases with pumping, and at the timing when the thyristor 161 should be triggered, 200V + 500V = 700
It will reach V. As described above, whenever a load is applied to the electrostrictive actuator 200, a voltage of 200 V is applied to the electrostrictive actuator in advance, thereby preventing polarization deterioration.

A control circuit for triggering the thyristor 161 of the controller C0NT 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 (VRI) 104 is connected to the inverting input, and when the terminal voltage of the electrostrictive actuator 200 exceeds 700 V, the output of the first comparator 101 becomes "1" level. The output of the first comparator 101 is connected to the rising trigger input of the first one-shot multi 105 of the retrigger pull.

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 m5ec) 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 short circuit for pilot injection, the voltage generated by the electrostrictive actuator exceeds the reference voltage (Vlll) mentioned above. This is to prevent the short-circuit operation from occurring multiple times.

In other words, unnecessary signals are masked during the signal generation period of the first one-shot multi 105.

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 determined by a capacitor 109 and a resistor 110. Since this pulse width is the pulse width of the trigger signal of the thyristor 161, it may be set to be as short as about 30 μs.

The Q output of the second one-shot multi 108 is the resistor 111
．． 112 to the base of the transistor 113, and the Q output of the second one-shot multi 108 is
At 1 level, transistor 113 is turned on. A pulse transformer 114 is connected to the collector of the transistor 113.
is connected, and when the transistor 113 is turned on, current flows through the primary coil of the pulse transformer 114, and a trigger signal is induced in the secondary coil.

This trigger signal is applied to the gate terminal 167 of the thyristor 161.
is connected to trigger the thyristor 161.

The diode 115 is for absorbing bank pulses.

The voltage generated by the electrostrictive actuator divided by the resistor 102:103 is also connected to the non-inverting input of the second comparator 140. Reference voltage (VH2) for inverting input
141 is connected, and the electrostrictive actuator 200
When the terminal voltage of becomes 600■ or more, the second comparator 1
The output of 40 is at the "1" level.

The output of the second comparator 140 is the retriggerable third
It is connected to the rising trigger input of the 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 set to a pump pumping period when the engine speed is 1200 rpm, that is, 25 m5 for a four-cylinder engine.

The Q output of the third one-shot multi 142 is connected to the D input of the D flip-flop 145, and the clock input C of the D flip-flop 145 is connected to the second comparator 1.
40 outputs are connected. D flip-flop 14
The Q output of No. 5 is connected to one input of a two-man 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 connected to the non-inverting input of the third comparator 150. A reference voltage (VH2) 151 is connected to the inverting input, and the output of the third comparator 150 becomes a "1" level when the accelerator opening is 10% or more, for example.

The output of the third comparator 150 is the two-man OR circuit 152
connected to the other input of the 2-person OR circuit 1
The output of 52 is connected to the reset manual R of the second one-shot multi 108, and when the output of the two-man OR circuit 152 is 1 level, the second one-shot multi is reset, so no trigger signal is generated. It looks like this.

The operation of the controller C0NT in the above configuration will be described below. Now, considering 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 20
0 is pressurized and a voltage is generated.

The initial value of this voltage will rise from 200 V because charge was supplied from the capacitor 300 last time.

The voltage generated by the electrostrictive actuator is divided by resistors 102 and 103 and compared with a reference voltage (VRI) by a first comparator 101. When the terminal voltage of the electrostrictive actuator exceeds 700 mm ((3) in FIG. 6), the output of the first comparator 101 becomes "1" level, and the first one-shot multi 105 is triggered.

The second one-shot multi 108 is triggered by the rise of the Q output of the first one-shot multi 105, and the resistor 111
, 112, the transistor 113 becomes conductive. As a result, the thyristor 16
1 is triggered (FIG. 6 f21) and becomes conductive, absorbing the charge of the electrostrictive actuator 200 into the capacitor 300. As a result, the terminal voltage of the electrostrictive actuator 200 decreases to about 200V (FIG. 6(3)), and the electrostrictive actuator 200 contracts by about 25 μm, so the pressure in the pump chamber 602 decreases as described above (FIG. 6(3)). 1)) Injection is interrupted (Fig. 6 (4)). The thyristor 161 is the coil 16
Due to the resonance of 3, it automatically commutates and becomes non-conductive. At this time, the cam lift is in the middle of its lift, so fuel is further fed under pressure, and the pressure in the pump chamber 602 rises again to restart injection.

Before the cam lift reaches top dead center, the aforementioned spill boat opens, the pump chamber pressure spills, and injection ends. At this time, the terminal voltage of the electrostrictive actuator 200 is as shown in FIG.
) as shown by the broken line, but if the value of the negative voltage is large, the polarization of the electrostrictive actuator 200 may be destroyed, so the diode 166 short-circuits the reverse voltage to protect it. There is.

When the pump pressure stroke is completed, the electrostrictive actuator 20
The terminal voltage of 0 becomes OV, resulting in a state where capacitor voltage>electrostrictive actuator voltage. If the capacitor voltage is 400V at this time,
The capacitor voltage is returned to the electrostrictive actuator 200 through the diode 162 and the resistor 164, and is balanced when the capacitor voltage and the electrostrictive actuator voltage become equal, that is, when they become 200 V each.

Next, a method of not controlling the electrostrictive actuator 200 according to engine operating conditions will be described.

At high loads or high speeds, even if pilot injection is performed, it will have little effect on noise and vibration, and pilot injection will reduce the injection rate, which will actually reduce the engine output, so controlling the electrostrictive actuator 200 is difficult. Don't do it. 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 passes through the two-person chaor circuit 152 and the first
Reset the one-shot multi 108.

That is, when the load is high, no trigger signal is generated to the thyristor 161, so the electrostrictive actuator is not controlled and remains open. The same applies to the engine rotation speed, and the output of the second comparator 140 reaches the 11j level every time the pump pumps the pump, but when this cycle becomes shorter than the output pulse width 251IIS of the third one-shot multi 142, the output of the D flip-flop 145 decreases. is “1”
He becomes Rubel and resets the second one-shot multi 108 through the two-person Chaor circuit. For this reason, thyristor 1
61 is not generated and the electrostrictive actuator 2
00 control is no longer performed.

In the device shown in FIG. 1, the electrostrictive actuator 200 can be controlled without requiring an external high voltage power source as in the past, and pilot injection can be realized.
Since the applied voltage of 00V is returned from the capacitor, deterioration of polarization of the electrostrictive actuator 200 can be prevented compared to simply shorting the electrostrictive actuator 200.

In carrying out the present invention, various modified embodiments other than those described above can be considered, and one example of another embodiment is shown in FIG. 7, for example. In the device shown in FIG. 7, the purpose is to increase the amount of contraction of the electrostrictive actuator by extracting the electric charge remaining in the capacitor 300 of the drive circuit B, which is the electrostrictive actuator 200, using a transistor. In the device shown in FIG. 7, a resistor 129 and a transistor 128 connected in series are connected in parallel with the capacitor 300.

Further, a fourth one-shot multi 120 and a fifth one-shot multi 123 are added to generate a control signal for the transistor 128. The Q output of the first one-shot multi 105 is the second one-shot multi 108.
At the same time, it is also input to the rising trigger input of the fourth one-shot multi 120. The output pulse width of the fourth one-shot multi 120 is determined by a capacitor 121 and a resistor 122. This pulse width is used to determine the timing at which the transistor 128 is turned on, and in order to set this timing to be between the end of the pump pumping stroke and the start of the next pumping stroke, the pulse width is approximately 20 mm.
This is m5.

The Q output of the fourth one-shot multi 120 is connected to the falling trigger input of the fifth one-shot multi 123. The output pulse width of the fifth one-shot multi 123 is determined by a capacitor 124 and a resistor 125. This pulse width is set to, for example, 1 ms, which is the time required for the charge in the capacitor 300 to be completely discharged through the resistor 129. The Q output of the fifth one-shot multi 123 is resistor 12
6,127 to the base of the transistor 128, and when the Q output of the fifth one-shot multi 123 is at the "1" level, the transistor 128 is turned on.
The charge on the capacitor 300 is discharged through the resistor 129. Further, the output of the two-man OR circuit 152 is the output of the second one-shot multi 108 [input R
In addition to this, it is also connected to the reset manual R of the fifth one-shot multi 123.

The operation of the FIG. 7 device will be explained. In the device shown in Figure 1,
The charge stored in capacitor 300 is transferred to diode 1
62 and is returned to the electrostrictive actuator via the resistor 164, but ultimately half the charge remains in the capacitor 300. Therefore, when the electric charge of the electrostrictive actuator 200 is absorbed into the capacitor 300 during the next pumping stroke,
The voltage of the electrostrictive actuator 200 decreased only to around 200V (FIG. 6 (3)). The device shown in FIG.
64 (approximately 20 m5 after the electric charge of the electrostrictive actuator 200 is absorbed into the capacitor 300), the transistor 128 is turned on, and the electric charge remaining in the capacitor is transferred to the resistor 129. It works by discharging electricity through the Therefore, when the electric charge of the electrostrictive actuator 200 is absorbed into the capacitor 300 in the next pumping stroke, the voltage of the electrostrictive actuator 200 can be reduced almost to around OV. Therefore, in the device shown in FIG. 7, the voltage drop of the terminal voltage of the electrostrictive actuator 200 when the thyristor of the device shown in FIG. The amount of contraction of the actuator 200 can be made approximately 1.4 times that in the case of the apparatus shown in FIG. 1, and the state of pilot injection can be made more noticeable.

The above operating state is shown in FIG. (1) is the pump chamber 60
2 pressure, (2) is the trigger signal of thyristor 161, (
3) is the control signal of the transistor 128, (4) is the terminal voltage of the actuator 200, and (5) is the capacitor 300.
shows the terminal voltage of

Furthermore, a configuration in which the diode 162 shown in FIGS. 1 and 7 is eliminated is also conceivable. In this case, the resistance value of the resistor 164 is
It is necessary to select a large value in order to prevent as much as possible the electric charge of the electrostrictive actuator 200 from flowing into the capacitor through the resistor 164 during the pumping stroke.

Note that when the second one-shot multi 108 is reset due to engine operating conditions, the fifth one-shot multi 123 is also reset, so the electrostrictive actuator 2
When the control of 00 is not performed, the transistor 128
doesn't work either.

As described above, in this embodiment, the excess charge remaining in the capacitor is discharged to the transistor, so the amount of contraction of the electrostrictive actuator 200 can be expanded, and the form of pilot injection can be made more pronounced. I can do it.

〔Effect of the invention〕

As explained above, the electrostrictive actuator of the present invention,
a capacitor capable of storing electric charge generated by the electrostrictive actuator; a switch element that is conductive at a predetermined time and capable of discharging the electric charge generated by the electrostrictive actuator to the capacitor; and a switch element capable of storing electric charge generated by the electrostrictive actuator; According to a device equipped with a current limiting element that can return the charged electric charge to the electrostrictive actuator, an inexpensive current limiting element can be used instead of using an expensive switching element (thyristor) in the circuit that returns the electric charge from the capacitor to the electrostrictive actuator. Since the element is used, the structure is inexpensive and has the effect of preventing polarization deterioration of the electrostrictive actuator.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an electrostrictive actuator device as an example of the basic form of the present invention, FIG. 2 is a diagram showing a configuration in which the actuator device shown in FIG. 1 is attached to a distribution type fuel injection pump, Figures 3 and 4
The figure is a characteristic diagram showing the relationship between the generated voltage and the short-circuit reduction amount with respect to the compressive load in an electrostrictive actuator. Figure 5 is a waveform diagram explaining the operation of the electrostrictive actuator. Figure 6 is the same as shown in Figure 1. A of electrostrictive actuator device
FIG. 7 is a circuit diagram showing the electrostrictive actuator device of another embodiment. FIG. 8 is a waveform diagram explaining the operation of FIG. 6. FIG. 9 is a waveform diagram explaining the operation of FIG. Figure 10 is a diagram showing the drive circuit of the electrostrictive actuator, Figure 9 is a waveform diagram explaining the operation of the circuit, Figure 11 is a waveform diagram explaining the operation of the circuit.
The figure is a circuit diagram showing a main part of a control means of an electrostrictive actuator device in another prior art. 101... Comparator, 105... One shot multi, 108... One shot multi, 120... One shot multi, 123... One shot multi, 140... Comparator, 142... One shot Multi, 145...D flip-flop, 150...Comparator, 161...Thyristor, 162...Diode, 166...Diode, 200...Electrostrictive actuator, 300...Capacitor, 500 ... Potentiometer, 602 ... Pump chamber, 604 ... Casing, 605 ... Cylinder bore, 606 ... Plunger, 607 ... Face cam, 608 ... Roller, 609 ... Distribution boat, 610a, 610b - Suction boat, 611...Low pressure chamber, 612...Suction passage, 614...Distribution passage, 615...Delivery valve, 616...
Spring, 617... Spill boat, 618...
... Spill ring, 619... Lever, 624...
Distance piece, 7... Injection control device, 720... Casing,
722... Piston, 723... Belleville spring, 7
25...Lead wire, 726...Variable volume chamber,
728...0 ring, 729...male thread, 8
13...Injection valve, 814...Distribution passage, P
...Fuel injection pump. Fig. 2 723... Belleville spring Fig. 4 Compressive load

Claims (1)

[Claims] 1. An electrostrictive actuator that is installed in a place that receives repeated loads, generates a voltage in response to compressive loads, and expands and contracts in accordance with the applied voltage, and a voltage is applied to the electrostrictive actuator. An electrostrictive actuator device comprising a control means, the control means including a capacitor capable of storing electric charge generated by the electrostrictive actuator, and a capacitor capable of charging the electric charge generated by the electrostrictive actuator into the capacitor. An electrostrictive actuator device comprising a switch element, a current limiting element that can return the electric charge stored in the capacitor to the electrostrictive actuator, and a control circuit that makes the switch element conductive at a predetermined time. . 2. The device according to claim 1, wherein a second current limiting element is connected to the switch element. 3. The device according to claim 2, wherein the second current limiting element is a coil having an inductance. 4. The device according to claim 1, wherein the switching element is a thyristor. 5. The device according to claim 1, characterized in that a rectifying element is connected to a circuit that returns charge from the capacitor to the electrostrictive actuator. 6. The device according to claim 1, wherein the repeated load is a load caused by hydraulic pressure of a jerk type hydraulic pump. 7. A transistor is connected in parallel to the capacitor, and after the charge is returned from the capacitor to the electrostrictive actuator, the transistor discharges the charge of the capacitor. equipment. 8. Fuel is introduced into the pump chamber formed by the cylinder bore of the fuel injection pump and the plunger slidably fitted into the cylinder bore, and the volume of the pump chamber is changed to deliver the fuel under pressure to the injection valve. In the fuel injection device for a diesel engine, the pump chamber is connected to a variable volume chamber that generates voltage under repeated loads and whose volume can be changed by an electrostrictive actuator that expands and contracts in accordance with the applied voltage, and A control means for applying a voltage is connected to the electrostrictive actuator, and the control means includes a capacitor capable of storing electric charge generated by the electrostrictive actuator, and charges the electric charge generated by the electrostrictive actuator to the capacitor. a current limiting element that can return the charge stored in the capacitor to the electrostrictive actuator, and a control circuit that makes the switch element conductive at a predetermined time when the fuel pressure in the pump chamber exceeds a certain pressure. A fuel injection device for a diesel engine using an electrostrictive actuator device, comprising: 9. The electrostrictive actuator expands when a voltage is applied and contracts when the voltage is removed, and control of the fuel injection rate by the expansion and contraction is stopped depending on the engine speed or load, and the engine speed changes when the voltage is removed. 9. The device according to claim 8, wherein the detection is based on the voltage generated by the strain actuator.