JPS60249648A - Engine controller - Google Patents

Abstract

PURPOSE:To improve response performance by varying the feedback control correction value used for the control of the electric conduction of a heating-wire type air amount flow meter (HW sensor) according to the operation state, in the measurement of the intake air amount by the HW sensor. CONSTITUTION:An HW sensor is constituted of a bridge circuit 20 consisting of a heater resistor 15, temperature detecting resistor 17, and balancing resistors 16 and 18 which is installed into an intake manifold, and the voltages VH and VI between the resistors 15 and 16 and between the resistors 17 and 18 are input into the both input terminals of a comparator 19 and an A/D converter 1d in a microcomputer 1. The average conduction current applied into the HW sensor is controlled by the control for the conduction time rate with which transistors 13 and 10 are turned ON and OFF. The control of the conduction time rate is feedback-corrected by using the feedback correction value which is varied according to the output signal of the HW sensor which is inputted into a CPU1a or the operation state of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an engine control device that uses a hot wire mass air flow meter to control the amount of intake air.

[Prior art]

Conventionally, engine control devices, especially those equipped with fuel injection devices, inject the optimal amount of fuel using the computer section of the engine control system based on detected data such as intake air flow rate, throttle opening, engine cooling water temperature, and engine speed. That's what I do. A sensor that detects the intake air flow rate in such an engine control system is used as a very important element, and the hot wire type air mass flow sensor (hereinafter referred to as HW Sen) is disclosed in Japanese Patent Application Laid-Open No. 55-57.
As shown in Publication No. 112, the sensing section and the control circuit for detecting the flow rate are integrated, and in this case, the output signal corresponding to the air flow rate taken out from the sensing section is independent of the air amount. It is a linear analog voltage signal.

Therefore, in order to supply the output signal from such a HW sensor, which requires a wide metering range (50 to 100 times) and high accuracy (within a few percent), to the engine control system, Japanese Patent Application Laid-Open No. 56-1999 is required. High precision A as shown in Japanese Patent No. 24521
It is necessary to convert it into a digital signal using a /D conversion circuit.

However, for the reasons mentioned above, HW sensors that require high accuracy have complicated control circuits and are expensive.

[Purpose of the invention]

In view of the above points, the present invention provides the control circuit function of the HW sensor.
The object of the present invention is to provide an engine control device that processes within a computer section of an engine control system, has a simple circuit configuration, reduces error factors, and improves responsiveness.

[Structure of the invention]

FIG. 6 is an overall schematic configuration diagram for clearly explaining the present invention. That is, means B for converting the output signal from the bridge circuit of the intake air amount sensor A using the hot wire type air mass flow rate detection mechanism into a digital value, and means for controlling the energization time ratio of the power source C applied to the intake air amount sensor A. means E for applying feedback correction to the energization time ratio in accordance with the output signal of the intake air amount sensor A converted into a digital value; and means F for calculating the air mass flow rate taken into the engine from this energization time ratio. and means E for applying feedback correction to the energization time ratio.
The magnitude of the feedback correction value used in the intake air amount sensor A
The device is provided with means for changing the value of the output signal from the engine or depending on the operating state of the engine.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

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

1 is a microcomputer of a fuel injection type engine control system having devices such as CPUIaXROMlb and RAMIc; ld, le, if and 1g are A/D converters provided in the microcomputer 1, respectively;
These are a digital output, a duty output port, and a digital input. 2 is a crank angle signal terminal connected to digital input 1g via input cover sofa 4, 3 is a throttle signal terminal connected to digital input 1g via input bumper 5, and 6 is an analog signal such as a thermistor thermometer. 7 is a terminal for driving a fuel injection valve (not shown) from the digital output 1e via a cover sofa 8, and 9 is a reference voltage source. , transistor 10,
The operational amplifier 1 and the resistor 12 constitute a constant voltage circuit, and the output voltage of the collector of the transistor 10 is equal to the voltage of the reference voltage source 9. The base of the transistor 13 is connected to the duty output port 1f via a resistor 14,
Turning it on and off serves as a switch for the constant voltage circuit described above. That is, when the transistor 13 is turned on, the transistor 10 is turned on and the HW sensor is energized. The HW sensor is a heater resistor 15 installed in the intake manifold.
A bridge circuit 20 is configured by the temperature detection resistor 17 and balance resistors 16 and 18, and the pressures V, . Input to the plus side terminal and minus side terminal of the comparator 19 and the A/D
It is input to converter 1d.

The output of the comparator 19 is connected to the digital input 1g to detect the balance state of the bridge circuit 20 of the HW sensor.

Note that the transistor 13 is turned on and off at a cycle of 4.096 m5ec by the microcomputer 1, and the
The W sensor performs duty control that controls the average energization current by changing the energization time ratio.

Next, the operation of the above configuration will be explained. FIG. 2 is a calculation flowchart showing the processing of the system of this embodiment. 4.096m from microcomputer 1 during engine operation
Every 5ec, the duty signal Do is output from the duty output port 1f as shown in FIG.
The average current applied to the HW sensor is controlled by controlling the current-carrying time ratio that turns the transistor 10 on and off, and at the same time the duty signal Do is output, the voltage VH between the heater resistor 15 and the resistor 16 and the temperature detection resistor are The voltage VI of Y between 17 and resistor 18 is read into A/D converter 1d. Note that this "H+ VI" is actually read into the A/D converter 1d with a slight delay from the duty signal Do.Next, this A/D converted value V
The first correction value ΔDOI is searched from the deviation vH−v between H and the A/D conversion value I using the table shown in FIG.

Note that, as can be seen from the table shown in FIG.
The value differs depending on the magnitude and sign of r. Next, a correction coefficient k of the first correction value ΔDOI corresponding to the previous air mass flow rate Ga1r stored in a predetermined address.
is searched from a table prepared in advance in the microcomputer 1, the first correction value ΔDOI obtained this time is multiplied by the correction coefficient k, and this is set as the true first correction value Δ001 obtained this time, and the duty signal is It is added to Do and correction is made. Also, at the same time as reading the A/D values vH and vI, the signal C from the comparator 19 is input to the digital input 1g.
The direction of the imbalance of the bridge circuit 20 described above is measured using 1°0 of this signal C, and the duty signal Do is corrected using the second correction value ΔDO2, which is a predetermined constant value. The duty signal Do output from the duty output 1f is reset. Then, the air mass flow rate Ga1r is determined from the finally corrected duty signal Do according to the table shown in FIG.
The appropriate engine fuel injection amount and injection timing are calculated from the crank angle signal from the terminal 3, the throttle signal from the terminal 3, the cooling water temperature signal from the terminal 6, etc., and the digital output 1e is used to inject a fuel injection valve (not shown) from the terminal 7. I try to control it.

Thereafter, the air mass flow rate is determined from the duty signal Do, which similarly controls the average current by intermittent current flowing to the HW sensor, and appropriate feedback control of the engine is performed.

In the above-mentioned embodiment, the correction coefficient was determined only by the air mass flow rate Ga ir as a determining factor, but the operating state of the engine (normal, transient) may also be added as a determining factor, that is, 1) 2) The engine is idle depending on whether the engine has warmed up completely according to the cooling water temperature signal, 2) The throttle valve is fully closed according to the throttle signal, and whether the engine speed is below a predetermined value according to the crank angle signal. 3) Air mass flow rate Ga obtained from Hw sensor
When the rate of change of 1r is a positive value and the magnitude is greater than a predetermined value, and when it is a negative value and the magnitude is greater than a predetermined value, the value is within a predetermined range near zero. Depending on the time, it may be detected whether the speed is acceleration, deceleration, or constant speed, and the correction coefficient k may be determined according to each state.

Furthermore, in the above embodiment, the correction coefficient k is searched from a table prepared in advance in the microcomputer 1, but this does not have to be just one table; multiple tables are prepared according to each engine condition. I don't mind if you leave it there.

Further, in the above-described embodiment, the correction coefficient k is determined based on the air mass flow rate Ga1r, but the correction coefficient k may be determined based on the previously determined duty signal Do.

Further, in the above embodiment, the basic first correction value ΔDO
After determining I, it is multiplied by the correction coefficient k, but a plurality of tables of the first correction value ΔDOI corresponding to the air mass flow rate Ga1r and the operating state of the engine are prepared in advance in the microcomputer 1. When searching for the correction value ΔDOI, the duty signal Do
The first correction value ΔDOI may be increased in order to add it to .

Furthermore, in the above embodiment, the correction is performed in two stages using the A/D converter 1d and the comparator 19;
Depending on the accuracy of converter 1d, comparator 19 may be omitted.

Also, voltage VH between heater resistor 15 and resistor 16 (X), and voltage V between temperature detection resistor 17 and resistor 18 (Y).

The difference VH-VI between them may be input to the A/D converter 1d via a differential amplifier.

In addition, the voltage VH between the heater resistor 15 and the resistor 16 and the voltage VH between the temperature detection resistor 17 and the resistor 18 are applied to the A/D with a slight delay from the duty signal Do because they pass through transistors, operational amplifiers, etc. in the circuit. converter 1d
To eliminate this delay, it is also possible to directly read the duty applied to the HW sensor from the constant voltage circuit to improve accuracy.

In addition to the HW sensor, a hot film flow rate needle can also be used as the intake air flow rate sensor.

[Effects of the Invention] As described above, according to the present invention, the control circuit function of the HW sensor is processed by a microcomputer for engine control, so the circuit configuration is simplified, and error factors are eliminated to improve accuracy. Furthermore, since the magnitude of the feedback correction value is changed according to the output signal value of the intake air sensor and the operating state of the engine, there is an excellent effect that responsiveness can also be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
A calculation flowchart showing the processing procedure of the microcomputer, FIG. 3 is a table for searching the first correction value ΔDOI, FIG. 4 is a table for searching the air mass flow rate Ga1r, and FIG. 5 is a time chart of circuit operation. , FIG. 6 is an overall schematic configuration diagram of the present invention. 1...Microcomputer, 1a...CPU, 1
b--ROM, 1 c--RAM, 1 d-A/D converter, 1e...Digital output, 1f...Duty output port, 1g...Digital input, 2...
・Crank angle signal terminal, 3... Throttle signal terminal, 6... Cooling water temperature signal terminal, 15... Heater resistor, 17... Temperature detection resistor, 16.18... Balance resistor , 19... comparator, 20... bridge circuit. Representative Patent Attorney Takashi Okabe Figure 1 n Figure 5 Figure 6 Δ

Claims (4)

[Claims] (1) A means for converting an output signal from a bridge circuit consisting of a heater resistance, a temperature detection resistance, and a plurality of balance resistors of an intake air amount sensor using a hot wire air mass flow rate detection mechanism into a digital value, and the intake air amount sensor. means for controlling an energization time ratio of a power source applied to the engine; means for applying feedback correction to the energization time ratio according to the digital value; and means for calculating an air mass flow rate taken into the engine from the energization time ratio. , means for changing the magnitude of the feedback correction value used for the feedback correction according to the value of the output signal of the intake air amount sensor or the operating state of the engine. . (2) The engine control device according to claim 1, wherein the magnitude of the feedback correction value is a function of the magnitude of the output signal value of the bridge circuit of the intake air amount sensor. (3) The engine control device according to claim 1, wherein the magnitude of the feedback correction value differs depending on the magnitude and sign of the deviation of the output signal value of the bridge circuit of the intake air amount sensor. . (4) The engine control device according to claim 1, wherein the magnitude of the feedback correction value differs depending on the operating state of the engine, that is, a steady state or a transient state.