JPH06117899A - Air flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To variably control an internal combustion engine so as to control the engine with high accuracy by providing such a circuit configuration that can simultaneously output the intake air flow rate and air temperature of the engine. CONSTITUTION:An exothermic resistor 2 and temperature sensitive resistor 5 which respectively detect air flow rates and air temperatures are installed to an air intake passage 6 and the resistor 2 is connected to a constant-current source A and reference resistor 3. The resistor 5 is connected to another constant-current source B4. Since the resistor 2 always receives a constant current from the current source A1 and generates heat, the heat radiating amount of the resistor 2 changes depending upon the amount of intake air 7 and the current value of the resistor 3 changes. Therefore, the output of the resistor 3 is outputted against the amount of the air 7 and a control unit 13 inputs the output as an air flow rate signal. On the other hand, a constant current which does not cause the resistor 5 to generate heat flows to the resistor 5 from the current source B4, the resistance of the resistor 5 changes depending upon the temperature of the air 7. Therefore. the output voltage of the resistor 5 becomes the temperature signal of the air 7 and is inputted to the unit 13. Thus, by driving the resistors 2 and 5 by means of different control circuits, the air flow rate signal and air temperature signal can be separately but simultaneously fetched.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an air flow measuring device for an internal combustion engine which requires an air flow temperature signal.

[0002]

2. Description of the Related Art In a conventional air flow rate measuring device using a thermal resistor, a thermal resistor and a temperature sensitive resistor constitute a bridge circuit as described in JP-A-58-87420.

[0003]

In the above prior art, when the intake air temperature signal is directly taken out from this circuit, the temperature sensitive resistor is
A division circuit was necessary because it was affected by both intake air temperature and air flow rate. Moreover, since the temperature sensitive resistor has a low resistance because it constitutes a bridge circuit, there is a problem that the amount of change with respect to temperature change is small. Therefore, when the intake air temperature is required to control the internal combustion engine, a separate intake air temperature sensor must be installed in the internal combustion engine.

An object of the present invention is to configure a control circuit capable of taking out an air flow rate signal and an intake air temperature signal at the same time by a non-bridge circuit, and by one air flow rate measuring device,
It is an object of the present invention to provide an air flow rate measuring device that provides a variation by controlling an internal combustion engine and performs a highly accurate control.

[0005]

The above object is to detect the amount of intake air supplied to an internal combustion engine by means of a thermal resistor installed in the air passage, and to detect the temperature of the intake air in the air passage. In the air flow rate measuring device that detects with a temperature resistor,
This is achieved by having a circuit configuration capable of simultaneously outputting the intake air amount and the air temperature.

[0006]

The air flow rate signal by the thermal resistor and the intake air temperature detection circuit by the temperature sensitive resistor are formed as separate circuits, and the air flow rate signal and the intake air temperature signal can be used individually by making them non-bridge circuits. Moreover, it is possible to measure with one air flow rate measuring device. Furthermore, since the intake air temperature detection signal from the temperature sensitive resistor is not affected by the air flow rate, the resistance value of the temperature sensitive resistor used in the intake temperature detecting circuit can be freely set.

[0007]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment in which the thermal resistor 2 and the temperature sensitive resistor 5 of the present invention are set separately. In the intake passage 6 of the internal combustion engine, a thermal resistor 2 for detecting the air flow rate and a temperature sensitive resistor 5 for detecting the air temperature are installed, and the thermal resistor 2 exposed to the intake air 7 has a constant current. It is connected to the source A1 and the reference resistor 3. A constant current is constantly supplied from the constant current source A1 to heat the thermal resistor 2. Since the amount of heat radiated from the thermal resistor 2 changes depending on the size of the intake air 7, the value of the current flowing through the reference resistor 3 changes. Therefore, the reference resistance 3
Is output corresponding to the size of the intake air 7. The output voltage of the reference resistor 3 is input to the control unit 13 via the terminal 9 of the connector 12 as an air flow rate signal. On the other hand, the temperature sensitive resistor 5 is connected to the constant current source B4, and a constant current is applied to the temperature sensitive resistor 5 so that the temperature sensitive resistor 5 is not heated. Since the resistance value of the temperature sensitive resistor 5 changes depending on the temperature of the intake air 7, the output voltage of the temperature sensitive resistor 5 becomes a temperature signal of the intake air 7. This temperature signal is input to the control unit 13 via the terminal 10 of the connector 12. In this way, the thermal type resistor 2 and the temperature sensitive resistor 5 installed in the intake passage 6 are driven by different control circuits, respectively, so that the air flow rate signal and the temperature signal can be taken out separately. Power is supplied to each control circuit from the control unit 13 via the terminals 8 and 11 of the connector 12. Furthermore, the individual control circuits are configured as one air flow measuring device.

According to the above embodiment, since the air flow rate signal and the temperature signal can be taken out from one air flow rate measuring device, variations can be provided by controlling the internal combustion engine.
Further, there is an effect that high-precision control becomes possible. Further, among the above-mentioned contents of implementation, there is an effect that the intake temperature of the air flow rate signal can be corrected by the temperature signal by the calculation function in the control unit 13.

The embodiment shown in FIG. 2 differs from the embodiment shown in FIG. 1 in that a temperature correction function is added to the air flow rate detection circuit.
The thermal resistor 2 is configured as a bridge circuit by the temperature variable resistor 15, the reference resistor 3, and the resistors 1 and 14 provided in the control circuit of the air flow rate measuring device, and the operational amplifier 17 detects the balanced state of the bridge circuit. The transistor 16 has a circuit configuration for supplying a constant current to the thermal resistor. During steady operation of the internal combustion engine, the temperature of the intake air 7 flowing through the intake passage 6 and the control circuit of the air flow rate measuring device are almost the same temperature, and the intake air temperature can be corrected by this circuit. During the transition, as shown in the embodiment of FIG. 1, the temperature signal of the temperature sensitive resistor 5 detected by another circuit can be corrected by the arithmetic function in the control unit 13. According to this embodiment, the same effect as that of the embodiment of FIG. 1 can be obtained.

[0011]

According to the present invention, since the air flow rate signal and the temperature signal can be taken out from one air flow rate measuring device, the control of the internal combustion engine can have more variations. Further, there is an effect that high-precision control becomes possible.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of an air flow measuring device showing an embodiment of the present invention.

FIG. 2 is a control circuit diagram of an air flow measuring device showing an application example of the present invention.

[Explanation of symbols]

1 ... Constant current source A, 2 ... Thermal resistor, 3 ... Reference resistance, 4 ...
Constant current source B, 5 ... Thermal resistor, 6 ... Intake passage, 7 ... Intake air, 8-11 ... Terminal, 12 ... Connector, 13 ...
Control unit, 14 ... Resistor 1, 15 ... Temperature variable resistor, 16 ... Transistor, 17 ... Operational amplifier.

Claims (4)

[Claims] 1. Air for detecting the amount of intake air supplied to an internal combustion engine by a thermal resistor installed in an air passage, and further detecting the temperature of the intake air by a temperature sensitive resistor installed in the air passage. The flow rate measuring device has a circuit configuration capable of simultaneously outputting the intake air amount and the air temperature. 2. The air flow measuring device according to claim 1, wherein the thermal resistor and the temperature sensitive resistor each have a constant current source and are driven by the constant current source. 3. The intake air amount and the air temperature detected by the thermal resistor and the temperature sensitive resistor according to claim 1, respectively, are input to a control unit having an arithmetic circuit, and further, by an air temperature signal, the An air flow rate measuring device, which corrects an intake air temperature of a supply current of the constant current source of a thermal resistor. 4. The thermal resistor according to claim 1, wherein the temperature variable resistor of the control circuit in the air flow measuring device, the resistor, and the reference resistor constitute a bridge circuit, and the bridge circuit is in a balanced state. Is detected by an operational amplifier and has a circuit configuration for supplying a constant current to the thermal resistor by a transistor, and the temperature sensitive resistor is a separate circuit from the thermal resistor.
An air flow measuring device characterized by being driven by a constant current source.