JPH062599A - Injector driving circuit - Google Patents

Abstract

PURPOSE:To reduce a difference between a signal of driving an injector and actual time of valve opening. CONSTITUTION:In an injector driving circuit comprising an injector INJ for injecting fuel, drive element for driving the injector, control part 1 for giving a drive signal to the drive element, detecting means for detecting a current flowing in the injector, differentiating means 3 and a comparator means 5, an output of the detecting means is input to the differentiating means, an output of the differentiating means is input to the comparator means, and an output of the comparator means is input to the control part. Thus, a fluctuation of ineffective time cm be corrected.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an injector drive circuit.

[0002]

2. Description of the Related Art In a conventional drive circuit, a power transistor for driving an injector is simply turned on / off by an injection signal as described in Car Electronics issued by Sankaido.

[0003]

When the injector is opened, the power transistor is turned on. Since the injector has an inductance, the current flowing through the injector gradually increases. The injector does not open until this current reaches a predetermined current. Therefore, it is necessary to turn on the power transistor for a longer period of time for waiting for this valve opening with respect to the target valve opening time. This time is called invalid time.

Conventionally, the pulse width for turning on the power transistor has been determined by using this invalid time as a predetermined value. Therefore, there is a drawback that the valve opening time of the injector fluctuates and the error of the control amount increases when the invalid time fluctuates due to the variation of the injector and the fluctuation of the characteristic. An object of the present invention is to reduce this error amount.

[0005]

In order to achieve the above object, the current flowing through the injector is detected, and the invalid time is obtained from the rate of change. The determined dead time is used to determine the pulse width.

[0006]

The current flowing through the injector is detected and the rate of change is obtained. The valve opening of the injector is started when the rate of change becomes larger than a predetermined value. The ineffective time is obtained by the difference between the ON start of the power transistor and the valve opening start time of the injector. The pulse width for turning on the power transistor is the time obtained by adding the obtained invalid time and the injector valve opening time as the control amount.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Injector: INJ (hereinafter abbreviated as INJ),
Power MOSFE with current detection terminal to drive it
T: TR (hereinafter abbreviated as TR), power supply: VB, INJ
In order to absorb the surge voltage generated when the
A diode connected between the gate and drain of R: D and a Zener diode: ZD, a resistor: a control unit for driving TR through R: 1, an amplifier for amplifying a current signal flowing through INJ appearing at a current detection terminal: 2, an amplifier : Differentiator that performs differentiation to obtain the change rate of the output of 2: Differentiator: 3
The power supply for generating a comparison value to be compared with the output of: 4 and the comparator for comparing them: 5. The operation will be described with reference to FIG. Signal for driving TR from control unit: 1: E1
Is output. When HI, TR turns on. The current flowing through INJ gradually increases when TR is turned on. The INJ opens when the current increases to that required to open it. When the valve is opened, the speed of current increase will be faster, and then the power supply: V
The saturation current value is determined by the voltage of B and the resistance value of INJ.
When E1 becomes LO, the current decreases and INJ closes. The time it takes for the current to start flowing and the increasing speed to change,
INJ has not been opened and is inactive.

The current flowing through INJ is provided in TR,
Although it is detected as a voltage at the current detection terminal, it is amplified by the amplifier 2 because it is a minute voltage. The signal after amplification is E
2 shows. E2 is differentiated by the differentiator: 3 to become E3. When the valve of INJ is opened, the increasing speed of the current becomes faster, so E3 becomes larger. In order to detect this increased E3, a predetermined comparison value is generated by the power supply: 4 and comparison is performed by the comparator: 5. The signal becomes E4 after the comparison.
E4 is input to the control unit: 1. The control unit 1 finds the time difference between the rising edge of E1 and the rising edge of E4 and stores it as T1.

The stored T1 is used in the logic shown in FIG. First, is the TR drive pulse first? To judge. If it is the first time, T1 is not stored, so the initial value is provisionally used. The T1 obtained at the previous driving, which is stored as the second time and thereafter, is used. The drive pulse width of TR is obtained as the sum of T1 and the valve opening time obtained as the control amount.

Since the invalid time can be accurately obtained by the above logic, even if the invalid time varies due to INJ variation or characteristic variation, the drive pulse of TR is changed to I
It is possible to exactly match the valve opening time of the NJ with the value obtained as the control amount. Therefore, the error in the INJ valve opening time can be reduced.

The control unit: 1 is a high-speed and highly accurate A /
Needless to say, when the D converter is provided, the amplifier: 2, differentiator: 3, comparator: 5, and power supply: 4 of FIG. 1 can be configured by software.

[0012]

According to the present invention, since the error between the injector drive signal and the actual valve opening time can be reduced, the error in the control amount can be reduced.

[Brief description of drawings]

FIG. 1 is a drive circuit diagram of an embodiment of the present invention.

FIG. 2 is a timing chart explaining the operation.

FIG. 3 is a diagram showing a conventional example.

FIG. 4 is a flowchart of an embodiment of the present invention.

[Explanation of symbols]

INJ ... Injector, TR ... Power MOSFET, 1
... control unit, 2 ... amplifier, 3 ... differentiator, 4 ... power supply, 5 ... comparator.

Claims (4)

[Claims] 1. An injector for injecting fuel, a drive element for driving the injector, a control section for giving a drive signal to the drive element, a detecting means for detecting a current flowing through the injector, a differentiating means, and a comparing means. In the injector drive circuit, the output of the detecting means is input to the differentiating means, the output of the differentiating means is input to the comparing means, and the output of the comparing means is input to the control unit. Injector drive circuit. 2. The injector drive circuit according to claim 1, wherein the output of the comparison means is an output for detecting a timing at which the rate of change of the current flowing through the injector is large. 3. The injector drive circuit according to claim 1, wherein the control unit calculates the valve non-opening time of the injector. 4. The injector drive circuit according to claim 3, wherein the drive signal given to the drive element includes a sum of the non-valve opening time and the valve opening time.