JPH0663473B2 - Drive circuit of electrostrictive actuator for fuel injection valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive circuit for driving an electrostrictive actuator used to open and close a fuel injection valve, and particularly to an electrostrictive device provided in each of a plurality of fuel injection valves. Drive circuit for driving a linear actuator.

[Conventional technology]

A fuel injection valve of a type in which an electrostrictive actuator is used to open and close the fuel injection valve is already known (see, for example, Japanese Patent Laid-Open Publication No. Sho.
60-1369 publication). In this case, the electrostrictive actuator is formed by stacking a predetermined number of pellet-shaped electrostrictive elements into a columnar shape, and the electrostrictive elements are ceramics containing lead zirconate titanate (PZT) as a main component. Consists of. As is already known, the electrostrictive element has a property of expanding or contracting in the thickness direction when a DC voltage is applied, and by utilizing this property, the lift amount of the nozzle needle is controlled and thereby the tip of the fuel injection valve is controlled. The fuel injection is controlled by opening or closing the injection port.

The electrostrictive actuator is provided in each fuel injection valve provided for each cylinder, and as a drive circuit for driving the electrostrictive actuator, a charging coil, a switching element (for example, a thyristor), and a discharging coil are provided. Each cylinder has a thyristor.

FIG. 4 shows an example of a conventional electrostrictive actuator drive circuit. This circuit shows one cylinder. For example, in the case of four cylinders, four circuits are provided in parallel.

The operation of this circuit is basically as follows. That is, when a voltage is applied to extend the charge and the thickness direction in PZT as electrostrictive actuator, turn on the thyristor S ₀ by entering from a separate control circuit of the trigger signal to the gate G ₁ of the thyristor S ₀ To do. As a result, the voltage across the capacitor C ₁ charged by the power source Vs is
It is boosted by ₁ and charges PZT through the thyristor S ₀ . On the other hand, turns on the thyristor S ₂ by inputting a trigger signal to the gate G ₂ of the thyristor S ₂ in the case of contracting to discharge PZT in the thickness direction. As a result, the electric charge charged in the PZT flows into the capacitor C ₂ via the coil L ₂ and the thyristor S ₂ . Apparently PZ due to this discharge
Since a negative voltage is applied to T, PZT contracts. By controlling the gates G ₁ and G ₂ of the thyristors S ₀ and S _{2 in} this manner, the thyristors are turned on or off, and thereby the electrostrictive actuator PZT is charged or discharged to obtain a predetermined expansion and contraction.

[Problems to be solved by the invention]

In the configuration of the drive circuit described above, the drive circuit described above is provided for each cylinder to control the expansion and contraction of the electrostrictive actuator. However, in each drive circuit, the inductance of the coil, the thyristor characteristics, etc. vary from component to component or with the passage of time. Therefore, even if the same trigger signal is applied to each thyristor, the same operating characteristics do not result and the electrostrictive actuator The expansion and contraction of the engine and the drive timing are deviated, resulting in uneven distribution of the fuel injection amount, resulting in engine vibration, deterioration of exhaust gas, and the like.

[Means for solving problems]

The present invention is a drive circuit for an electrostrictive actuator for a fuel injection valve that solves the above-mentioned problems. For example, when driving each multi-cylinder engine and the electrostrictive actuator for a fuel injection valve, each conventional cylinder By using the coil and the switching element provided in the same as the switching element and the coil common to each electrostrictive actuator, it is intended to make the drive circuit characteristics uniform and reduce the variation in the fuel injection amount characteristics. Is a drive circuit of an electrostrictive actuator for a fuel injection valve that controls a plurality of fuel injection valves corresponding to each by expanding and contracting a plurality of electrostrictive actuators by a drive circuit. A charging switching element and a charging coil common in series to the electrostrictive actuators arranged in the When the electrostrictive actuator is discharged, a switching element for discharging is connected in series to each of the electrostrictive actuators, and a charging circuit is formed in series for a plurality of electrostrictive actuators. It is characterized in that a coil is connected to form a discharge circuit.

〔Example〕

FIG. 1 is a drive circuit diagram of an embodiment of the electrostrictive actuator according to the present invention. In FIG. 1, 1, 2, 3 and 4 are electrostrictive actuators composed of electrostrictive elements provided in the fuel injection valve of each cylinder, S ₀ is a thyristor which is a switching element for charging, and S _{1 to} S ₄ Is a thyristor that is a switching element for discharging, Go, G _{1 to} G ₄ are gates of each thyristor, L ₁ is a charging coil, L ₂ is a discharging coil, and D
Reference numerals _{1 to} D ₄ are backflow preventing elements, for example, diodes, C is a capacitor, and _VDC is a DC power source. In the present embodiment, the electrostrictive actuator is a drive applied to a system in which it expands when a voltage is applied to close the fuel injection valve to stop the fuel supply, and when it discharges it contracts to open the injection valve. Circuit.

When a trigger signal is input to the gate G ₀ of the thyristor S ₀ from an electronic control unit described later, the thyristor S ₀ turns on. The voltage across the capacitor C, which is charged by the DC power supply V _DC, is boosted by the coil L ₁ via the thyristor S ₀ that is turned on, and is simultaneously applied to the actuators 1 to 4 via the backflow prevention diodes D _{1 to} D _4. The actuators 1 to 4 are charged and extend. As a result, the nozzle needle descends and the fuel injection in each cylinder is all stopped. Then, when the fuel cylinder to be supplied with is the cylinder of the actuator 1 for example, turns on the thyristor S ₁ by sending a trigger signal from the electronic control unit to the gate G ₁ of the thyristor S _1. As a result, the electric charge accumulated in the actuator 1 is discharged through the thyristor S ₁ and the coil L ₂ , the actuator 1 contracts, the injection valve opens, and fuel is supplied. Similarly,
When the actuators 2 to 4 are contracted, the thyristors S _{1 to} S ₄ are automatically turned off when a trigger signal is sequentially input to each of the gates G _{2 to} G ₄ to discharge them while taking timing. Simultaneously charging all the actuator turns on the thyristor S ₀ by entering a trigger signal to the gate G ₀ of the thyristor S ₀ when recharging. When each actuator is controlled by such a circuit configuration, the discharge is always performed through the coil L ₂ , so that there is no variation in response due to the coil during discharge,
Further, since the charging is always performed through the coil L _1, there is no variation in responsiveness. As a result, variations in fuel injection characteristics can be reduced, and at the same time, the number of parts is reduced, so that the failure rate and the manufacturing cost can be reduced.

FIG. 2 is a timing chart showing an example of the above-described operation. In the figure, a high level state is a state in which the actuators 1 to 4 are charged by applying a voltage, and a low level state is a state in which they are discharged. The upper stage of the trigger signal is supplied to the gate G ₀ of the thyristor S ₀ , and the lower stage trigger signal is supplied to the gate of the corresponding thyristor when discharging a predetermined actuator. That is, all the actuators are charged by the trigger at the time t _{1, and when} the trigger at the time t ₂ is supplied to the gate G ₁ of the thyristor S ₁ , the actuator 1 discharges and fuel is injected. Next, the actuator 1 is charged again by the trigger at the time t ₃ . Furthermore the actuator 3 is supplied a trigger gate G ₃ of the thyristor S ₃ at time t ₄ is discharged by the fuel injection, the actuator 3 by a trigger time t ₅ is charged again. Thereafter, the actuators 4 and 2 are discharged and recharged in the same manner.

FIG. 3 is a schematic configuration diagram of a diesel engine and its peripheral devices in which the circuit of FIG. 1 is used. In FIG. 3, 10 is an electronic control unit (ECU), 11 is a drive circuit according to the present invention, 12 is a diesel engine main body, 13 to 16 are fuel injection valves, and 13a to 16a are provided for each fuel injection valve. Electrostrictive actuator, 17 is a reservoir tank, 18 is a fuel tank,
19 is a DC / DC converter, and 20 is a battery. Also, 2
Is an accelerator opening sensor, 4A and 4B are crank angle sensors, 8
Is a crystal sensor.

In such a configuration, each thyristor in the drive circuit 11 determines a predetermined thyristor in the ECU 10 based on detection signals from the accelerator opening sensor 2, the crank angle sensors 4A and 4B, the water temperature sensor 8 and the like which are input to the ECU 10. It is turned on or off according to a control signal output after the calculation is performed.

〔The invention's effect〕

According to the present invention, the charging side coil, the switching element, and the discharging side coil of the drive circuit of the electrostrictive actuator are used in common for each cylinder, so that it is possible to reduce variations in drive characteristics. The cost can be reduced and the fuel injection amount can be made uniform.

[Brief description of drawings]

FIG. 1 is a drive circuit diagram of an electrostrictive actuator according to the present invention, FIG. 2 is a charge / discharge timing chart of the actuator according to the circuit of FIG. 1, and FIG. 3 is an engine in which the circuit of FIG. 1 is used. FIG. 4 is a schematic configuration diagram of the peripheral device, and FIG. 4 is a drive circuit diagram of a conventional electrostrictive actuator. (Reference Numerals) 1 to 4 ...... electrostrictive actuator, _{L 1, L 2} ...... coil, _S 0 to S ₄ ...... thyristor, _D 1 to D ₄ ...... diodes, 2 ...... accelerator angle sensor, 4A , 4B ... Crank angle sensor, 8 ... Water temperature sensor, 10 ... Electronic control unit, 11 ... Drive circuit, 12 ... Engine, 13-16 ... Fuel injection valve, 13a-16a ... Electrostrictive actuator , 17 …… Reservoir tank, 18 …… Fuel tank.

Claims (1)

[Claims] 1. A drive circuit for an electrostrictive actuator for a fuel injection valve, wherein a drive circuit expands and contracts a plurality of electrostrictive actuators to control injection of a plurality of fuel injection valves corresponding to the electrostrictive actuators. All of the series connection bodies of the respective type actuators and the backflow prevention element are connected in parallel, and one commonly used switching element for charging and the charging coil are connected in series to the parallel connection body for charging. And a series connection body of an individual discharge switching element and one discharge coil commonly used is connected in parallel to each of the plurality of electrostrictive actuators to form an individual A drive circuit for an electrostrictive actuator for a fuel injection valve, characterized by forming a discharge circuit.