JPS6217339A - Drive circuit for electrostrictive actuator for fuel injection valve - Google Patents

Abstract

PURPOSE:To reduce the cost of component parts and uniformalize the quantity of injected fuel, by using the coils and switching elements of the charging and discharge portions of a drive circuit for electrostrictive actuators, in common to the cylinders of an engine. CONSTITUTION:A switching element S1 and a coil L1, which are used in common to electrostrictive actuators 1-4, are provided in the actuator charging portion of a drive circuit 41. A switching element S2 and a coil L2, which are used in common to the actuators 1-4, are provided in the actuator discharge portion of the drive circuit 41. All the actuators are simultaneously charged and also simultaneously discharged. Since the drive circuit 41 is thus made of a pair of coil and thyristor for the charging and another pair of coil and thyristor for the discharge, response irregularities do not arise due to the coils in the charging and discharge.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a unit injector type fuel injection valve that opens and closes a fuel injection valve using an electrostrictive actuator, and particularly relates to an electrostrictive type fuel injection valve for a fuel injection valve. The present invention relates to a drive circuit that drives an actuator.

[Conventional technology]

A fuel injection valve of a type that uses an electrostrictive actuator to open and close the fuel injection valve is already known (for example, Japanese Patent Laid-Open No. 1369/1983). In this case, the electrostrictive actuator is formed by laminating a predetermined number of pellet-shaped electrostrictive elements to form a columnar shape, and the electrostrictive element is made of ceramic whose main component is lead zirconate titanate (PZT). Consisting of As is already known, an electrostrictive element has the property of expanding or contracting when a DC voltage is applied in its thickness direction, and this property is used to control the lift amount of the nozzle needle, thereby controlling the nozzle at the tip of the fuel injection valve. It opens or closes to control fuel injection.

The electrostrictive actuator is installed in the fuel injection valve provided for each cylinder, and the drive circuit for driving the electrostrictive actuator includes a charging coil, a switching element (for example, Cyrisk), and a discharging coil. Each cylinder has its own risk.

FIG. 5 shows an example of a conventional electrostrictive actuator drive surface, and this circuit shows one cylinder. For example, if there are four cylinders, four of these circuits are provided in parallel.

The operation of this circuit is basically as follows. That is, when a voltage is applied to PZT as an electrostrictive actuator to charge it and make it expand in the thickness direction, a trigger signal is input from a separate control circuit to the gate G1 of the thyristor SI to turn on the thyristor SI. As a result, the voltage across the capacitor C1, which is being charged by the power source V, is boosted by the coil L and charges the PZT via the thyristor SI. On the other hand, when PZT is discharged to contract in the thickness direction, a trigger signal is input to the gate G of the thyristor S2 to turn on the thyristor S2. As a result, the charge stored in the PZT flows to the capacitor C2 via the coil L2 and the thyristor S2. Due to this discharge, a negative voltage is apparently applied to the upper PZT, and the PZT
contracts. In this way, by controlling the gates of thyristors SL and G2 by G and 02, the thyristor is turned on or turned off, thereby charging or discharging the electrostrictive actuator PZT to obtain a predetermined expansion and contraction.

[Problem that the invention seeks to solve]

In the configuration of the drive circuit described above, the drive circuit described above is provided for each cylinder to control expansion and contraction of the electrostrictive actuator. However, in each drive circuit, the inductance of the coil, the silicate characteristics, etc. vary from component to component or due to changes over time. This caused a lag in the expansion/contraction and drive timing of the engine, resulting in uneven distribution of fuel injection amount, resulting in engine vibrations, deterioration of exhaust gas, etc.

[Means for solving problems]

The present invention is a drive circuit for an electrostrictive actuator for a fuel injection valve in a unit injector system that solves the above-mentioned problems, and is for driving an electrostrictive actuator for each fuel injection valve of a four-cylinder diesel engine, for example. In this case, the coils and switching elements that were conventionally provided for each cylinder.

By making the switching element and coil common to each electrostrictive actuator, the drive circuit characteristics are made uniform and the variation in fuel injection amount characteristics is reduced. In a fuel injection valve that controls fuel injection by expanding and contracting an actuator, the drive circuit 41 has a switching element S+ common to each electrostrictive actuator and a coil connected to the side that charges the electrostrictive actuator, and discharges the coil. There is also a switching element common to each electrostrictive actuator on the side.

G2 and coil L2 respectively, and is characterized in that all the electrostrictive actuators are simultaneously charged during charging, and all the electrostrictive actuators are simultaneously discharged during discharging.

〔Example〕

FIG. 1 is a driving circuit diagram of an embodiment of an electrostrictive actuator according to the present invention. 1°2.3 and 4 in Figure 1
is an electrostrictive actuator consisting of an electrostrictive element provided in the fuel injection valve for each cylinder, S and G2 are switching elements, for example, thyristors, G and G2 are gates of each thyristor, and L and L2 are coils. , C is a capacitor, and ■1 is a DC power supply. In this embodiment, when voltage is applied to the electrostrictive actuator, the electrostrictive actuator is charged and expanded to close the fuel bypass passage, and when discharged, it contracts and opens the fuel bypass passage. As will be described later, when the fuel bypass passage is closed, the pressed fuel is injected from the nozzle, and when the fuel bypass passage is opened, it is not injected.

In this drive circuit, when a trigger signal is input to the gate G1 of the thyristor S from an electronic control unit, which will be described later, the thyristor S1 is turned on. The voltage across the capacitor C, which is being charged by the DC power supply VOC, is coiled through the turned-on thyristor SI, is boosted, and is simultaneously applied to the actuators 1 to 4, so that the actuators 1 to 4 are charged and extended. Next, when a trigger signal is input to the gate G2 of the thyristor S2 from an electronic control unit, which will be described later, the thyristor S2 is turned on.

Actuator 1 is activated by turning on Cyrisk S2.
The electric charges accumulated in the actuators 1 to 4 are simultaneously discharged through the cyrisk S2 and the coil L4, and the actuators 1 to 4 contract.

In this way, this drive circuit requires only one set each of a charging coil and thyristor, and a discharging coil and thyristor, so there is no variation in response due to the discharging coil and charging coil. As a result, it is possible to reduce variations in fuel injection characteristics, and at the same time, because the number of parts is reduced, the failure rate and manufacturing cost can be reduced.

FIG. 2 is a timing chart showing an example of the above-mentioned operation. In the figure, a high level state is a state in which the actuators 1 to 4 are charged by voltage application, and a low level state is a state in which they are discharged.

The upper trigger signal is supplied to the gate G+ of the thyristor S1, and the lower trigger signal is supplied to the gate G2 of the thyristor S2. As described above, in this drive circuit, all the actuators 1 to 4 operate simultaneously in charging and discharging, so all waveforms are the same. However, since fuel injection is performed according to the cycle of the engine, the injection is performed, for example, at the timing shown by diagonal lines.

Figure 3 shows the electrically controlled fuel injection valve (
unit injector). This injector 30
This operation is achieved by mechanically rotating the cam 35, which pushes the shaft 33 of the plunger 36 downward against the spring 37, and supplies the fuel supplied from the fuel supply hole 31 through the main passage 31a to the hydraulic chamber 38. Compress and increase pressure to nozzle 3
Inject from 9. In this case, the electrostrictive actuator 32
(Any one of actuators 1 to 4 shown in Figure 1)
If a voltage is applied to the electrostrictive element, the electrostrictive element expands and closes the bypass passage 31b by the overflow valve 34 provided at its tip, so that fuel overflows through the low pressure side (heat pump side), that is, the main passage 31a. It can be compressed in the hydraulic chamber 38, raised to high pressure, and injected without having to do so. Conversely, if the electrostrictive element is discharged, it contracts and the overflow valve 34 opens, so that the fuel flows back to the main passage 31a side via the bypass passage 31b, and the nozzle 39
It is not sprayed from. As described above, by the expansion and contraction of the electrostrictive actuator 32, when the overflow valve 34 is open, injection is not possible, and when it is closed, injection is possible. Therefore, by controlling the opening/closing timing, the injection start timing and the injection amount can be controlled.

FIG. 4 is a schematic diagram of the diesel engine and its peripheral equipment. In FIG. 4, 40 is an electronic control unit (
ECU), 41 is a drive circuit according to the present invention, 42 is a diesel engine main body, 43-46 are fuel injection valves, 432-
46a is an electrostrictive actuator provided for each fuel injection valve; 47 is a reservoir tank that supplies fuel supplied from the fuel tank 48 via a hydraulic pump to each cylinder; 49
is a DC/DC converter, and 50 is a battery. Further, 2 is an accelerator opening sensor, 4A and 4B are crank angle sensors, and 8 is a water temperature sensor.

In such a configuration, each cylinder in the drive circuit 41 is connected to the accelerator opening sensor 2, which is input to the ECU 40.
Based on the detection signals from the crank angle sensors 4A and 4B, the water temperature sensor 8, etc., a predetermined calculation is performed within the ECU 40, and then it is turned on or turned off by a control signal output.

〔Effect of the invention〕

According to the present invention, since the charging side coil and switching element and the discharging side coil and switching element of the drive circuit of the electrostrictive actuator are commonly used for each cylinder, it is possible to reduce variations in drive characteristics. This makes it possible to reduce component costs and further equalize the fuel injection amount.

[Brief explanation of drawings]

FIG. 1 is a drive circuit diagram of an electrostrictive actuator according to the present invention, FIG. 2 is a charging/discharging timing chart of the actuator using the circuit shown in FIG. 1, FIG. 3 is a cross-sectional view of a unit injector, and FIG. FIG. 1 is a schematic configuration diagram of an engine and its peripheral devices in which the circuit is used, and FIG. 5 is a drive circuit diagram of a conventional electrostrictive actuator. (Explanation of symbols) 1 to 4...Electrostrictive actuator, L+, Lx...Coil, S,, S2...Sirisk, 2...Accelerator angle sensor, 4A, 4B...Crank angle sensor , 8... Water temperature sensor, 40... Electronic control unit, 41... Drive circuit, 42... Engine, 43-46... Fuel injection valve, 43a-46a... Electrostrictive actuator, 47...
-Reservoir tank, 48...Fuel tank, 30...Unit injector.

Claims (1)

[Claims] 1. A unit injector type fuel injection valve that integrates a pump that uses a cam to generate fuel pressure in synchronization with the engine speed, and injects fuel by adjusting the generated fuel pressure by expanding and contracting an electrostrictive actuator using a drive circuit. In the fuel injection valve, the drive circuit includes a switching element and a coil common to each electrostrictive actuator on the side for charging the electrostrictive actuator, and a switching element and coil common to each electrostrictive actuator on the side for discharging the electrostrictive actuator. An electrostrictive actuator for a fuel injection valve, characterized in that it is equipped with a switching element and a coil, and that all the electrostrictive actuators are charged at the same time during charging, and all the electrostrictive actuators are simultaneously discharged during discharging. drive circuit.