JPH0138534Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting a disconnection in internal wiring of an air flow meter in an intake air amount detection device for detecting the intake air amount of an internal combustion engine.

The intake air amount detection device detects the amount of intake air flowing through the intake passage, and calculates the amount of intake air and
It is provided to set the fuel supply amount in accordance with the separately detected engine speed, and a conventional example of this is shown in FIG. That is, a reference voltage is applied from a power source 3 via a fixed resistor 4 to a resistor 2 of an air flow meter 1 installed in an intake passage (not shown) of the engine. By sliding a slider 5 attached to a flap (not shown) that rotates in accordance with the amount of intake air on this resistor 2, a voltage corresponding to the amount of intake air is applied to the resistor from the terminal of the slider 5. 6 is applied to one terminal of the A/D converter 9 of the control unit 8 via the signal voltage line 7 to which the signal voltage 6 is connected. Also,
The reference voltage is applied to the other terminal of the A/D converter 9 via a reference voltage line 11 having a resistor 10 connected to the side terminal of the resistor 2 .

Then, the voltage applied from the terminal of the slider 5 and the reference voltage are compared by the A/D converter 9, and a digital signal representing the amount of intake air corresponding to these potential differences is output to the microcomputer 12. The amount of fuel supplied is calculated based on the intake air amount, engine speed, and other correction signals, and the signals drive fuel injection valves (not shown).

However, in such a conventional intake air amount detection device, the resistance 2 of the air flow meter 2
It was not possible to detect a break in internal wiring such as the following.

The present invention was devised in view of these conventional problems, and involves connecting the resistor terminal that outputs the reference voltage of the air flow meter and the terminal of the slider with a resistor whose resistance value is sufficiently larger than the resistance of the air flow meter. It is an object of the present invention to provide a disconnection detection device which detects a disconnection by reducing the potential difference between both terminals to zero when the internal wiring of an air flow meter is disconnected.

The present invention will be explained below based on an embodiment shown in FIG. Note that the same elements as in the conventional example will be described with the same numbers as in FIG. 1.

In the figure, the intake passage of an internal combustion engine (not shown)
The air flow meter 1 installed in the airflow meter 1 has a resistor 2 and a fixed resistor 4 connected in series, and a slider 5 attached to a flap (not shown) that rotates in accordance with the amount of intake air and moves in conjunction with the resistor 2. The top is attached so that it can be slidably connected. The slider 5 terminal of this air flow meter 1 is connected to the signal voltage line 7 via a resistor 6.
is connected to one input terminal of the A/D converter 22 of the control unit 21, and applies a voltage to the A/D converter 22 according to the amount of intake air.

Also, the connection point between resistor 2 and fixed resistor 4 is resistor 1
0 to the other input terminal of the A/D converter 22 by a reference voltage line 11, and applies the voltage applied to the resistor 2 to the other input terminal of the A/D converter 22 as a reference voltage. do. A fixed resistor 4 of the air flow meter 1 is connected to a power source 3, and a resistor 2 is grounded. The above configuration is the same as the conventional one. Here, the signal voltage line 7 and the reference voltage line 11 are connected by a resistor 23 according to the present invention. The resistance value of this resistor 23 is set to be sufficiently larger than that of the resistor 2.

Furthermore, the output terminal of the A/D converter 22 is connected to the input terminal of a microcomputer 24, which will be described later, and also serves to determine whether the internal wiring of the air flow meter 1 is disconnected. A digital signal corresponding to the potential difference input from the air flow meter 1 is output from the A/D converter 22 to the microcomputer 24. The microcomputer 24 is an A/D converter 2
In response to the signal No. 2, as described above, the fuel injection amount is calculated according to the detection signal of the intake air amount, etc., and the signal is output to a fuel injection valve (not shown) to drive it. Furthermore, when the potential difference between both input terminals of the A/D converter 22 is zero, it receives the digital signal and detects that the internal wiring of the fixed resistor 4 or resistor 2 of the air flow meter 1 is disconnected. A determination circuit is provided in the microcomputer 24.

To explain the operation of the disconnection detection device having such a configuration, when the air flow meter 1 is normal, the air flow meter 1 sends a voltage and reference voltage corresponding to the amount of intake air to the A/D converter 22 via the signal voltage line 7 and the reference voltage line 11. A voltage is applied, and a digital signal corresponding to the potential difference is output from the A/D converter 22 to the microcomputer 24 to detect the amount of intake air. Since the resistor 23 is set sufficiently large, the current flowing through the resistor 23 can be ignored and does not affect the detection accuracy of the intake air amount.

On the other hand, if, for example, part B of the internal wiring of the air flow meter 1 is disconnected, the signal voltage from the terminal of the slider 5 is transmitted to the A/D via the signal voltage line 7.
Since the same voltage is applied to one input terminal of the converter 22 and the same voltage is applied to the other input terminal of the A/D converter 22 via the resistor 23 and the resistor 10, the potential difference between them becomes zero, As a result, the microcomputer 24 determines that the internal wiring of the air flow meter 1 is disconnected using the determination circuit described above, and disconnection detection is performed.

Furthermore, when the C section is disconnected, the reference voltage is directly applied from the reference voltage line 11 to the other input terminal of the A/D converter 22, and at the same time the resistor 23,
Since the reference voltage is also applied to one input terminal of the A/D converter 22 via the input terminal 6, the potential difference between the two input terminals becomes zero. A break in internal wiring is detected.

Furthermore, when the A part is disconnected, the reference voltage is not applied to the resistor 2 itself, so the A/D converter 22
The potentials of both input terminals are equal to 0, and disconnection is also detected. Note that the resistor 23 is composed of two resistors 6,
10 A/D converters 22 may be connected to each other. In this way, by connecting the signal voltage line 7 and the reference voltage line 11 through the resistor 23, disconnection in any part of the air flow meter 1 can be detected.

Furthermore, since the microcomputer 24 determines and detects a disconnection when the potential difference between the input terminals of the A/D converter 22 is zero, the memory capacity of the microcomputer 24 for determining disconnection is small, and the resistor 23 is provided. Therefore, disconnection detection can be performed at low cost and with high reliability.

It should be noted that, when a disconnection is detected by the microcomputer 24, it will be even better if a means is provided to alert the passenger.

As explained above, the present invention uses an extremely simple configuration in which the slider terminal of the air flow meter and the reference voltage terminal are connected through a resistor, and maintains the intake air amount detection function of the air flow meter while detecting disconnection and disconnection of the internal wiring. can be done at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional intake air amount detection device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1...Air flow meter, 2...Resistance, 7...
...Signal voltage line, 11...Reference voltage line, 2
2...A/D converter, 23...Resistor, 24...Microcomputer.

Claims (1)

[Scope of utility model registration request] An air flow meter comprising a resistor to which a reference voltage is applied and a slider that slides on the resistor is installed in the intake passage of an internal combustion engine, and a voltage is taken out from the terminal of the slider that slides on the resistor according to the amount of intake air. In an intake air amount detection device that detects an intake air amount by comparing the terminal voltage and a reference voltage output from the resistor terminal, a resistor to which the reference voltage is applied between the slider terminal and the resistor terminal; An intake air amount for an internal combustion engine, characterized in that a resistor having a sufficiently larger resistance value is connected, and a means is provided for determining that the internal wiring of the air flow meter is disconnected when the potential difference between the two terminals is zero. Disconnection detection device in detection device.