KR20020017398A - Circuit for protection against excess high-pressure occurrence of common rail in diesel fuel injection system - Google Patents

Abstract

PURPOSE: A circuit for preventing the generation of the excessively high pressure of an electronic common rail diesel fuel injector is provided to prevent the generation of the excessively high pressure of a rail by stopping a regulator valve when the pressure of the rail is over a moderate level. CONSTITUTION: A pressure regulator valve(8) and a free wheel diode(9) are connected to a battery voltage(7). An FET(Field Effect Transistor)(10) for driving a regulator valve by applying a signal by a PWM(Pulse Width Modulation) signal is connected to the opposite to the battery voltage. The collector of a transistor(11) is connected to the gate terminal to which the PWM signal of the FET is applied. The emitter of the transistor is grounded, and the base is connected to a comparator(12). The voltage value outputted from the pressure sensor increases in proportion to the increase of pressure. If the voltage value is high, the FET is restrained from driving even if a PWM signal is applied. Therefore, the regulator valve stops and the pressure of a rail falls.

Description

Circuit for protection against excess high-pressure occurrence of common rail in diesel fuel injection system}

The present invention relates to an electronically controlled common rail diesel fuel injection device, in which a high-pressure fuel is stored in a rail and the output of a pressure sensor is sensed when the fuel is injected into the electronic valve to detect the output of the regulator valve. The present invention relates to a circuit for preventing the occurrence of excessive high pressure of the rail of an electronically controlled common rail diesel fuel injection device that stops driving so that a pressure is lowered to prevent a dangerous situation from occurring.

The common rail system supplies fuel to the rail 2 from the high pressure pump 1 as shown in FIG. 1A, and receives the pressure of the rail from the pressure sensor 4 in the ECU 3 to control the pressure of the rail. In addition, fuel injection signal is sent to inject fuel.

At this time, when the pressure regulator valve is driven, as shown in FIG. 1B, the relationship between the pressure Fp, the spring force Fs, and the magnetic force Fm of the rail is the spring force Fs and the magnetic force Fm of the valve. It is supposed to act opposite to the pressure (Fp).

Increasing the pressure on the rails reduces the amount of fuel flowing out of the rails to the regulator valves, which requires increasing the magnetic force (Fm) and eventually increasing the current through the regulator valves.

At this time, the relationship between the pressure (Fp), the spring force (Fs) and the magnetic force (Fm) is in equilibrium and a constant pressure is as follows.

Fp = Fs + Fm

The higher the average current flowing through the regulator valve, the greater the magnetic force, reducing the high-pressure fuel from the rail to maintain the high pressure. The smaller the average current, the more the fuel in the rail escapes and the lower the pressure in the rail. .

2 shows a drive current waveform in which the pressure of the rail flows through the regulator valve.

By controlling only the duty at a constant frequency, the pressure controls the average current through the regulator valve.

The larger the duty ratio turned on, the larger the average current. The smaller the duty ratio turned on, the smaller the average current.

PWM (PULSE WIDTH MODULATION) shown in FIG. 2 is a signal generated from the ECU.

3 shows the driving circuit of the regulator valve.

When the FET is turned on / off by the PWM signal, current flows to the regulator valve by the battery voltage when it is turned on, and the current gradually increases.

Then, when the PWM signal changes from ON to OFF, the FET is also turned off, and the induced electromotive force flows through the freewheel diode, whereby the current in the regulator valve gradually decreases.

At this time, the current waveform is shown in the upper side of FIG.

As such, the duty of the PWM wave is adjusted to control the pressure of the rail from the pressure sensor to the desired pressure. If the ECU becomes impossible to control or the rail pressure rises too much due to an abnormal signal. You are in a very dangerous situation.

The object of the present invention is to detect the pressure of the rail in order to prevent such a risk and to stop the operation of the regulator valve when the pressure exceeds the appropriate value to drop the pressure of the rail to prevent the occurrence of excess high pressure.

1A and 1B are configuration diagrams of a common rail system,

1a is an overall configuration diagram

Figure 1b shows the pressure, spring force, of the rail when the regulator valve

Relationship with magnetic force

2 is a drive current waveform and a drive PWM signal of the pressure regulator valve of the rail;

3 is a conventional circuit diagram for driving a pressure regulator valve of a rail;

4 is a circuit for preventing excessive high voltage generation in a rail according to the present invention;

<Description of the symbols for the main parts of the drawings>

1: high pressure pump 2: rail

3: ECU 4: Pressure Sensor

5: regulator valve 6: injector

7: battery voltage 8: pressure regulator valve

9: freewheel diode 10: FET

11 transistor 12 comparator

Hereinafter, embodiments of the present invention will be described in detail in the accompanying drawings.

Figure 4 is a circuit diagram of the excess high pressure generation according to the present invention.

In a regulator valve driving circuit in which a pressure regulator valve and a freewheel diode 9 are connected to a battery voltage 7, and a regulator valve driving FET (switching element) 10 for applying a signal to the other side by a PWM signal is provided. The collector of the transistor 11 is connected to the gate terminal to which the PWM signal of the FET 10 is applied, the emitter is grounded, and the comparator 12 is connected to the base.

In the operation of the circuit of the present invention, the output of the pressure sensor comes out as a voltage value, and this voltage value becomes large in proportion to the pressure.

Therefore, this voltage value was compared by the comparator, and when the above standard, the output of the comparator was made high.

In addition, a transistor is attached to the gate terminal of the FET to which the PWM signal driving the pressure regulator is applied. When the output of the comparator is high, this output signal is applied to the base terminal of the transistor so that the PWM signal is transmitted from the transistor collector to ground. To get out.

This prevents the FET from driving even when a PWM signal is applied, causing the regulator valve to stop operating, which in turn reduces the pressure on the rail.

In this case, the reference voltage of the comparator may be equal to the value of the voltage from the pressure sensor at the limit pressure of the rail to be limited.

As described above, the excess high-pressure generation prevention circuit of the rail of the present invention detects the pressure in the rail directly when the control of the ECU is impossible and stops the driving of the regulator valve when the value exceeds the appropriate value, thereby reducing the pressure of the rail to generate the excess high pressure. Prevents a safe effect.

Claims (3)

In the regulator valve driving circuit in which the pressure regulator valve 8 and the freewheel diode 9 are connected to the battery voltage 7, and the regulator valve driving FET 10 for applying a signal to the other side by means of a PWM signal, Electronically controlled common rail diesel, characterized in that the collector of the transistor 11 is connected to the gate terminal to which the PWM signal of the FET 10 is applied, the emitter is grounded, and the comparator 12 is connected to the base. Excess high-pressure generation circuit of the rail of the fuel injection device. 2. The electronically controlled common of claim 1, wherein the output signal of the pressure sensor installed on the rail is input to the non-inverting terminal of the comparator, and a voltage value output at the maximum pressure of the rail to be limited to the inverting terminal is input. Excess high-pressure circuit of the rail of diesel fuel injection system. 3. The electronically controlled common rail diesel fuel injection according to claim 1 or 2, wherein when the comparator output is high, the output is applied to the base of the transistor so that the transistor is turned on to cause the PWM signal to fall to ground. Excess high-voltage circuit in the rail of the device.