JPS61237861A - Control device of fuel injection valve - Google Patents

Abstract

PURPOSE:To spread a dynamic range for an injection valve, by enabling an extension and contraction stroke in an electrostrictive actuator to be freely controlled even with the power supply voltage in a fixed level, in the case of the fuel injection valve injecting a predetermined amount of fuel in accordance with extension and contraction of the electrostrictive actuator. CONSTITUTION:In a driving circuit 47 for an electrostrictive actuator 2, if a driving signal rises up generating the first trigger signal from a trigger generating circuit 43, the first thyristor 471, being conducted, supplies an electric charge from a capacitor 476 to the electrostrictive actuator 2. Then the actuator 2, being extended, causes a fuel injection valve to inject fuel. And if the second thyristor 472 is conducted by the second trigger signal in a predetermined time, the actuator 2, whose electric charge is transferred to a capacitor 477, is contracted. Here the capacitor 477, whose initial voltage conducts a transistor 482 through a resistor 483, variably controls an extension and contraction stroke of the actuator 2.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a control device for a fuel injection valve of an internal combustion engine that controls the amount of fuel injection by a pump-type fuel injection valve using an electrostrictive actuator. .

[Conventional technology]

FIG. 9 is a side sectional view illustrating the configuration of this type of fuel injection valve. In FIG. 9, the fuel injection valve 1 is operated by expansion and contraction of an electrostrictive actuator 2. In FIG. The electrostrictive actuator 2 is a columnar stack of thin disk-shaped elements having an electrostrictive effect, and each element has five layers in the thickness direction.
When 00v is applied, it expands by about 0.5μm, and conversely -500
When V is applied, it contracts by about 0.5 μm. Therefore, if 100 of these elements are laminated, 100 times the expansion and contraction can be obtained.

The element is a ceramic made by sintering lead zirconate titanate, and silver electrodes are formed on both sides of the element to apply voltage. A lead wire 201 is used to apply voltage, and this lead wire passes through the upper casing 101 of the injection valve 1 through the grommet 121 and is taken out to the outside.
It is connected to a drive circuit 47 which will be described later. The expansion and contraction motion of the electrostrictive actuator 2 is directly transmitted to the piston 120, causing it to reciprocate.

The piston 120 slides inside the cylinder 102 in the casing upper 101 and performs pumping work by expanding and contracting the volume of the pump chamber 103. A disc spring 104 is provided in the pump chamber 103, and the electrostrictive actuator 2 The piston 120 is urged in the direction of contraction.

This is because the contraction force of the electrostrictive actuator 2 is weaker than the expansion force. When the pump chamber 103 expands,
External fuel is sucked in through the check valve 105. The suction passage 106 at this time is provided in the wall constituting the upper casing 101. Also, the check valve 105 is connected to the pump chamber 103.
Distance piece 1 for isolating the injection valve 107 and the injection valve 107
It is installed in 08.

The injection valve 107 is an outward-opening single-hole nozzle consisting of a nozzle body 109 and a needle 110. The needle 110 is biased by a disc spring 111 to close the spout 112. However, when the pump chamber 103 contracts, the fuel pumped through the discharge port 119 of the distance piece 108 pushes out the needle 110 due to its hydraulic pressure and the nozzle 112
It is sprayed outside when opened.

The upper casing 101, the distance piece 108, and the nozzle body 109 have the same diameter, are stacked in that order, and are pressed and fixed in the axial direction by the bag-shaped casing lower 113. The female thread of the casing lower 113 and the male thread of the casing upper 101 are connected by screwing. A hole 114 is provided at the lower end of the casing lower to expose the nozzle 112. The casing lower is further provided with a male screw 115 on its outer periphery, and is fixed to the internal combustion engine 3 by this.

Note that 116 is an O-ring, 117 is a dowel pin, and 118 is a fuel hole provided in the upper casing 101.

The amount of injection per injection from the injection valve 1 is determined by the electrostrictive actuator 2.
The stroke is determined by the applied voltage. Now, increase the applied voltage from -500 to +500
When changing to V, 10mg will be injected, -300
It is assumed that 4 mg is injected when changing from V to +300■. The reason why there is no linear relationship between the applied voltage and the injection amount is because
This is because the injection amount does not depend only on the amount of expansion of the electrostrictive actuator, but also includes ineffective factors such as dead volume and pressure loss in the pump chamber.

FIG. 1θ schematically shows the overall structure of the internal combustion engine including the fuel injection valve. In FIG. Intake valve 304, exhaust valve 305
, an intake pipe 306, an exhaust pipe 307, and the like. A throttle valve 308 is provided inside the intake pipe 306, and a fuel injection valve 1 is provided on the pipe wall 309 thereof. The fuel injection valve 1 may be located upstream or downstream of the throttle valve 308. The intake pipe 306 communicates with the atmosphere via an air cleaner 310, and an air amount sensor 51 is provided downstream of the air cleaner 310.

Many types of air flow sensors 51 have been put into practical use, and any of them may be used, but for example, an air flow meter that uses a hot wire anemometer and outputs a voltage proportional to the wind speed, that is, proportional to the intake air volume, is used. I'll decide. The principle and structure of a hot-wire anemometer are well known and will not be described here. The output of the air amount sensor 51 is input to the control circuit 4.

Fuel is supplied to the fuel injection valve 1 from a fuel tank 9 via a feed pump 7 and a filter 8.

The feed pump 7 is a very common type that stops operating when the discharge pressure exceeds a set value, and a diaphragm or electromagnetic type is usually used.

In either case, the discharge pressure is set to 0.5 kg/cm''.Although not shown, it is effective to provide a reservoir or an accumulator between the feed pump 7 and the fuel injection valve 1. Either eliminate the feed pump 7 and provide a sufficient head difference between the fuel tank 9 and the fuel injection valve 1.
Otherwise, it is also possible to pressurize the fuel tank 9.

A water jacket 311 is installed in the cylinder block 301.
A water temperature sensor 52 is provided to detect the temperature of the cooling water. A signal from the water temperature sensor 52 is input to the control circuit 4. Further, if necessary, the exhaust pipe 307 is provided with, for example, an 02 sensor 53. and the control circuit 4
An output signal from the fuel injection valve 1 is supplied to the fuel injection valve 1, and the electrostrictive actuator 2 is driven.

[Problem that the invention seeks to solve]

By the way, in the case of an internal combustion engine for an automobile, the required control range of the amount of fuel is up to about 50 times the minimum amount. Therefore, when controlling the amount of fuel as described above using a fuel injection valve that measures fuel based on the drive frequency, the maximum frequency of the drive frequency needs to be about 50 times the minimum frequency.

On the other hand, the above minimum frequency needs to be larger than the intake frequency at the maximum rotation speed of the internal combustion engine, for example, 4
The minimum frequency is 50 Hz or more for the maximum rotational speed of the cycle internal combustion engine of 600 rpm. Therefore, assuming that the minimum frequency is 50Hz, the driving frequency of the fuel injector is 5
A control range of 0 Hz to 2500 Hz is required.

However, even though fuel injection valves are fast-responsive,
Due to reasons such as response delay during fuel intake, the maximum stable frequency at which stable operation can be achieved is, for example, up to about 1000 Hz. Therefore, there is a problem that the control range of the amount of injected fuel cannot be made sufficiently wide.

The present invention has been made to solve the above problems,
When discharging the charge supplied to the electrostrictive actuator for each drive cycle of the fuel injector, the amount of discharged charge is controlled by a capacitor that is controlled to a predetermined voltage at the beginning of each drive cycle. Based on the idea of making the expansion and contraction stroke of the electrostrictive actuator variable, the dynamic range of the fuel injection valve can be greatly expanded without particularly increasing the drive frequency range described above.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a control device for a fuel injection valve that injects a predetermined amount of fuel according to the expansion/contraction stroke of an electrostrictive actuator. A first current limiting element (e.g., a first coil) and a first switching element (e.g., a first thyrisk) provided in series between a DC power source and the electrostrictive actuator for charging; A capacitor for removing part of the charge from the electrostrictive actuator,
a second current limiting element (for example, a second coil) provided in series between the electrostrictive actuator and the capacitor;
and a second switching element (e.g., a second thyristor), and a circuit for controlling the voltage of the capacitor, and the expansion/contraction stroke of the electrostrictive actuator is made variable by controlling the voltage of the capacitor. A control device for an injection valve is provided.

[For production]

According to the above configuration, for each drive cycle of the fuel injection valve,
A predetermined amount of charge is supplied from the DC power source to the electrostrictive actuator via the first current limiting element and the first switching element, and then the second current limiting element and the second switching element The electric charge of the electrostrictive actuator is discharged to the capacitor through the capacitor, and the amount of the discharged electric charge is controlled by controlling the initial voltage of the capacitor to a predetermined value for each drive cycle. As a result, the expansion and contraction stroke of the electrostrictive actuator can be freely controlled.

〔Example〕

FIG. 1 shows an embodiment of an electrostrictive actuator drive circuit 47 in a control device according to the present invention. 1st
In the figure, 475 is a high-voltage power supply for charging the electrostrictive actuator 2, and 476 is a large-capacity capacitor connected in parallel to the power supply 475, which is a transient voltage source necessary for driving the electrostrictive actuator 2. Supply large current. Reference numeral 471 denotes a first signal, and a first trigger signal is supplied to its gate input from a trigger generation circuit 43, which will be described later. 473 is a first coil having inductance. The capacitor 476, the first thyristor 4711, the first coil 473, and the electrostrictive actuator 2 are each connected in series. 4
74 is the second coil, 472 is the second cyrisk,
A second trigger signal is supplied from the trigger generation circuit 43 to the gate input. 477 is a capacitor for removing a predetermined amount of charge from the electrostrictive actuator 2, and its capacitance is about three times that of the electrostrictive actuator 2. The electrostrictive actuator 2, the second coil 474, the second thyristor 472, and the capacitor 477 are also connected in series. 482 is a transistor for controlling the voltage of the capacitor 477, and its collector is connected to the high voltage side of the capacitor 477 via a current limiting resistor 483. 480 is an operational amplifier whose output is connected to the base of a transistor 482 via a resistor 481. A resistor 478.479 is connected to the non-inverting input side of the operational amplifier 480.
The voltage of the capacitor 477 divided by the voltage is supplied. The reference voltage V is on the inverting input side of the operational amplifier 480.
is provided through input terminal 484.

Figure 2 shows one embodiment of the trigger signal generation circuit.
A drive signal is input to the trigger generation circuit 43 from an input terminal 431, and the first one-shot multi 432 is triggered at the rising edge of the drive signal, and its output has a noslus width (approx. 30, u
sec) is output. This signal is connected to the base of transistor 437 via resistors 435 and 436. The emitter of the transistor 437 is connected to the power supply, and the collector is connected to the pulse transformer 4.
It is connected to the primary side of 38. When the output of the first one-shot multi 432 is at “0” level, the transistor 4
37 becomes conductive, current flows through the primary side of the pulse transformer 438, and a signal is generated on the secondary side. This signal is connected to diode 43
It is connected to the gate input of the first thyristor 471 via a nine resistor 440. The resistor 441 and capacitor 442 are for noise prevention. Next, the second one-shot multi 443 is triggered in synchronization with the fall of the drive signal, and a second trigger signal is supplied to the gate input of the second thyristor 472 by a similar circuit.

Next, the operation of the drive circuit 47 will be explained.

In FIG. 1, the drive signal is connected by a control circuit to be described later, but here it is assumed to be a pulse with a pulse width of 300 μsec and a frequency f. At the rising edge of the drive signal, the first thyristor 471 is activated by the trigger generation circuit 43 described above. A first trigger signal is generated for triggering. Therefore, the first thyristor 471 becomes conductive, and a series resonant circuit consisting of the capacitor 476, the first thyristor 471, the first coil 473, and the electrostrictive actuator 2 is formed, and the capacitor 476
Electric charge is supplied from the electrostrictive actuator 2 to the electrostrictive actuator 2, and the terminal voltage of the electrostrictive actuator 2 becomes approximately 1.5 times the power supply voltage. Therefore, the electrostrictive actuator 2 expands and the ninth
The area of the piston 120 in the figure x the amount of extension is applied to the nozzle 112.
Spray more. When charging of the electrostrictive actuator 2 is finished, the first thyristor 471 automatically commutates and becomes non-conductive. After a predetermined time (300μ5ec), a second trigger signal is generated from the trigger generation circuit 43 and the second thyristor 472
conduction. Therefore, the electrostrictive actuator 2, the second
Coil 474, second thyristor 472, capacitor 47
A series resonant circuit consisting of 7 is formed. Then, a sinusoidal current flows through the circuit, and the electric charge of the electrostrictive actuator 2 moves to the capacitor 477, so that the terminal voltage of the electrostrictive actuator 2 decreases, and the electrostrictive actuator 2 contracts. Therefore, fuel is replenished into the pump chamber via the check valve 105 in preparation for the next injection.

Here, a feature of the present invention is that the initial voltage of the capacitor 477 is controlled. This operation will be explained in detail below (see Figure 4).
72 conducts, if the voltage of the capacitor 477 is Ov, it will be similar to the conventional electrostrictive actuator drive circuit, and the voltage drop width of the electrostrictive actuator 2 will be the maximum, swinging to a negative voltage, and the voltage of the capacitor 477 will decrease. becomes higher. At this time, the amount of contraction of the electrostrictive actuator 2 is maximum.

If this continues, even if the second thyristor 472 becomes conductive next time, the electrostrictive actuator 2 will not connect to the capacitor 47.
If the charge of the capacitor 477 is removed by turning on the transistor 482 before the 0th time when the amount of contraction decreases because the charge transfer to the capacitor 477 decreases,
Each time, the amount of contraction of the electrostrictive actuator 2 becomes maximum (see the left half of FIG. 4).

Since the process of charging the electrostrictive actuator 2 does not change each time, assuming that the length of the electrostrictive actuator 2 during expansion is the same, it can be considered that the expansion/contraction stroke of the electrostrictive actuator 2 is determined by the amount of contraction. In the previous example, the voltage of the capacitor 477 was set to ov, but as the initial voltage of the capacitor 477 is increased, the charge from the electrostrictive actuator 2 to the capacitor 477 increases when the second thyristor 472 becomes conductive. Since the amount of movement of the electrostrictive actuator 2 decreases, the amount of contraction of the electrostrictive actuator 2 decreases, and therefore the expansion and contraction stroke also decreases (see the right hand part of FIG. 4).

The initial voltage of capacitor 477 is controlled by making transistor 482 conductive through resistor 483.

Further, in FIG. 1, the voltage of the electrostrictive actuator 2 is divided into 1/100, for example, by resistors 478 and 479, and connected to the non-inverting input of an operational amplifier 480. A reference voltage vl is supplied to the inverting input of the operational amplifier 480. When the voltage of the capacitor 477 is higher than the reference voltage 8×100, the output of the operational amplifier 480 becomes high, the transistor 482 is made conductive through the resistor 481, and the charge from the capacitor 477 is discharged through the resistor 483, thereby lowering the voltage. When the voltage of the capacitor 477 becomes lower than V, X100, the output of the operational amplifier 480 becomes low and the transistor 482 becomes non-conductive, so that the voltage of the capacitor 477 does not fall below that level. Therefore, the voltage of capacitor 477 is always V,
The value of the resistor 483 is determined from the capacitance of the capacitor 477 (approximately 1.5 μF) and the maximum frequency (500 Hz) of the drive signal, and the voltage of the capacitor 477 is controlled to be X100 by the next cycle. The time constant is set to be enough to complete the control, and is set to, for example, 200Ω. According to the above operation, by varying Vl, the initial voltage of the capacitor 477 can be changed, and therefore, the amount of contraction of the electrostrictive actuator 2, that is, the expansion and contraction stroke can be controlled.

Note that FIG. 3 shows a modification of the drive circuit 47 shown in FIG. 1, and in this drive circuit 47', the first
A common coil 473' is provided in place of the first coil 473 and second coil 474 shown in the figure to serve as these two coils, but its operation is similar to that of the circuit in FIG. 1.

Furthermore, in each of the drive circuits shown in FIGS. 1 and 3, transistors, FETs, GTOs, etc. are used instead of the first thyristor 471 and second thyristor 472, and FETs, GTOs, etc. are used instead of the transistor 482.
It is clear that the scales use TO and the like.

Next, FIG. 5 shows the characteristics of the injection amount with respect to the reference voltage vR. When ■Y is 0■, the expansion and contraction stroke is maximum, so the injection amount is also maximum, and as ■ increases, the injection amount decreases.Since it is greater than 0, even if the power supply voltage is constant, the injection amount is also maximum. By changing the voltage V, the amount of injection per injection can be varied smoothly and accurately, and the dynamic range of the injector can be dramatically expanded.

Next, FIG. 6 shows an example of specific control. In order to take advantage of the high-speed response of the electrostrictive actuator, it is driven at 50 Hz even at the minimum injection amount at idle, and the maximum frequency is set to 500 Hz due to constraints such as power supply capacity and check valve response.The dynamic range of the driving frequency is Minimum 10cc/a+in engine side requirement that can only be obtained by 10 times
If we assume a dynamic range of 50 times greater than that of up to 500 cc/a+in, this cannot be achieved as is. 5 by changing the reference voltage vR in the drive circuit explained earlier.
If we can secure double the dynamic range, we can meet the total demand of 50 times. Figure 6 shows the maximum injection amount of 5
Drive frequency 500 H at 00 cc/lll1n
z, v.

= OV, the minimum injection amount is 10 cc/a+in, the driving frequency is 50 Hz, and Vm = 4 V, it is shown that a dynamic range of 50 times can be covered. The driving frequency and the reference voltage V are changed between the maximum injection amount and the minimum injection amount so that they are smoothly connected.

FIG. 7 shows the configuration of the arithmetic control circuit 41 that performs the above control. Reference numeral 51 denotes an air amount sensor, which uses a known vane type or a hot wire, and measures the intake air amount of the engine. A water temperature sensor 52 is attached to the engine and measures the coolant temperature.

411 is an input interface which AD converts the outputs of the air amount sensor 51 and water temperature sensor 52 and connects it to the pass line 41.
Send to 5. 412 is a CPU that performs calculation control; 413
4 is a ROM in which programs and various data are stored.
14 is a RAM. An output interface 416 is loaded with a digital value corresponding to the drive frequency calculated by the CPU and creates a signal of the drive frequency. Reference numeral 417 generates a drive signal of a constant pulse width in synchronization with the above signal by a one-sit multi drive. The pulse width is determined by the time constant of the capacitor 418 and resistor 419, and is 300 μsec.

420 is a DA conversion circuit, and the reference voltage calculated by the CPU is
The digital value corresponding to 1 is converted into an analog voltage and output to the drive circuit 47.

The operation of the above configuration will be explained using the flowchart shown in FIG. The fuel injection amount control routine is
It is activated by an interrupt signal of 50H2, which is the lowest driving frequency (step 801). First, read the intake air amount Q from the input interface 411 (step 802).
. From this intake air amount, the basic injection amount q that achieves the predetermined air-fuel ratio
! I^3 ward is calculated (step 803). Next, read the water temperature from the input interface 411 (step 8
04), Calculate the increase coefficient K from the increase map data according to the water temperature stored in the ROM in advance (steer knob 80
5). And the final injection amount QFIN = KX (1mA
sg is calculated (step 806). Once qFIN has been determined, the drive frequency map and reference voltage map stored in the ROM are drawn based on FIG. 6, and the drive frequency r and reference voltage 5 are determined (steps 807 and 808).

Finally, the drive frequency data is output through the interface 41.
6, the reference voltage data is output to the DA conversion circuit 420 and the process returns (steps 809 to 811). Thereafter, a drive signal and a reference voltage (2) are created by the aforementioned hardware to perform a predetermined injection.

〔Effect of the invention〕

As described above, according to the control device according to the present invention, even if the power supply voltage is constant, the expansion and contraction stroke of the electrostrictive actuator can be controlled electrically and with good responsiveness. This has the effect of greatly expanding the

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an electrostrictive actuator drive circuit in a fuel injection valve control device according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of a trigger signal generation circuit in the fuel injection valve control device. 3 is a circuit diagram showing a modification of the drive circuit shown in FIG. 1; FIG. 4 is a timing diagram for explaining the operation of the drive circuit shown in FIG. 1; The figure shows the relationship between the reference voltage and the injection amount of the fuel injection valve when the drive circuit shown in Fig. 1 is used. FIG. 7 is a block diagram showing an embodiment of a circuit that calculates and generates a drive signal and a reference voltage in the fuel injection valve control device. FIG. 8 is a flowchart showing the calculation procedure for the frequency of the drive signal and the reference voltage, and FIG. 9 is a cross-sectional view illustrating the configuration of a fuel injection valve controlled by the present invention. FIG. 10 is a diagram schematically showing the overall configuration of an internal combustion engine including fuel injection valves controlled according to the present invention. (Explanation of symbols) 1: Fuel injection valve, 2: Electrostrictive actuator, 3: Internal combustion engine, 4: Control circuit, 41: Arithmetic control circuit, 43: Trigger signal generation circuit, 47: Actuator drive circuit, 471: No. 1 switching element, 472: second switching element. Fig. 2 43... Signal generation circuit 432.443... One-shot multivibrator tacho reference voltage (V) Fig. 5 Driving frequency 0 seconds) Fig. 6

Claims (6)

[Claims] 1. A control device for a fuel injection valve configured to inject a predetermined amount of fuel in accordance with the expansion and contraction stroke of an electrostrictive actuator, the control device comprising a direct current power source and a direct current power source for charging the electrostrictive actuator. A first current limiting element and a first switching element provided in series between, a capacitor for removing a part of the charge of the electrostrictive actuator, and a capacitor between the electrostrictive actuator and the capacitor. It consists of a second current limiting element and a second switching element provided in series, and a circuit that controls the voltage of the capacitor, and by controlling the voltage of the capacitor, the expansion and contraction stroke of the electrostrictive actuator is variable. A control device for a fuel injection valve, characterized in that: 2. Claim 1, wherein the circuit for controlling the voltage of the capacitor is provided with a transistor element for discharging the charge stored in the capacitor until the voltage of the capacitor drops to a predetermined voltage. control device for fuel injection valves. 3. A fuel injection valve according to claim 1, wherein a reference voltage is inputted from the outside to a circuit for controlling the voltage of the capacitor, and the voltage of the capacitor is lowered to a voltage corresponding to the reference voltage. Control device. 4. The fuel injection valve control device according to claim 3, wherein driving of the electrostrictive actuator is controlled by its driving frequency and the reference voltage input to a circuit that controls the voltage of the capacitor. . 5. The fuel injection system according to claim 4, wherein trigger signals generated at the rise and fall of a drive signal of a predetermined frequency are inputted to the first switching element and the second switching element, respectively. Valve control device. 6. 5. The fuel injection valve control device according to claim 4, wherein the drive frequency and the reference voltage are simultaneously controlled according to the amount of fuel injected.