JPH0650081B2 - Engine controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an engine control device in which an intake air amount is used as control data by a hot-wire air mass flowmeter.

[Prior art]

2. Description of the Related Art Conventionally, an engine control device, particularly one having a fuel injection device, injects an optimum amount of fuel by a computer unit of an engine control system from detection data such as intake air flow rate, throttle opening, engine cooling water temperature and engine speed. I am trying. A sensor for detecting the intake air flow rate of such an engine control system is used as a very important element, and a hot wire type air mass flow rate sensor (hereinafter referred to as HW sensor) is disclosed in JP-A-55-57.
As disclosed in Japanese Patent Laid-Open No. 112, a sensing unit and a control circuit for detecting a flow rate are integrally formed. In this case, an output signal corresponding to the flow rate of air taken out from the sensing unit is non-linear with respect to the air amount. Analog voltage signal.

Therefore, in order to supply an output signal from the HW sensor to the engine control system, which requires a wide adjustment range (50 to 100 times) and high accuracy (within several percent), Japanese Patent Laid-Open No. Sho 56-56 has been proposed.
Highly accurate A / D as shown in Japanese Patent Publication No. 24521
It is necessary to convert into a digital signal with a conversion circuit.

However, for the above-mentioned reason, the HW sensor that requires high accuracy has a complicated control circuit and becomes expensive.

[Object of the Invention]

In view of the above points, the present invention provides a control circuit function of the HW sensor,
It is an object of the present invention to provide an engine control device which is processed in a computer part of an engine control system and has a simple circuit configuration, which is intended to reduce error factors and improve responsiveness.

[Structure of Invention]

FIG. 6 is an overall schematic configuration diagram for clarifying the present invention. That is, the means B for converting the output signal from the bridge circuit of the intake air amount sensor A by the hot wire type air mass flow rate detection mechanism into a digital value and the means for controlling the energization time ratio of the power source C applied to the intake air amount sensor A. D, 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 a means F for calculating the mass air flow rate of air taken into the engine from this energization time ratio. And G for changing the magnitude of the feedback correction value used by the means E for adding the feedback correction to the energization time ratio in accordance with the value of the output signal from the intake air amount sensor A or the operating state of the engine. It is equipped with a microcomputer.

〔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 CPU 1
a, a microcomputer of a fuel injection type engine control system having devices such as a ROM 1b and a RAM 1c
d, 1e, 1f and 1g are an A / D converter provided in the microcomputer 1, a digital output,
Duty output port and digital input. Reference numeral 2 is a crank angle signal terminal connected to the digital input 1g via the input buffer 4, 3 is a throttle signal terminal connected to the digital input 1g via the input buffer 5, and 6 is an analog signal such as a thermistor thermometer. Is measured and is input to the A / D converter 1d for a cooling water temperature signal of the engine, 7 is a terminal for driving a fuel injection valve (not shown) from the digital output 1e via the output buffer 8,
A reference voltage source 9 includes a transistor 10 and an operational amplifier 11.
And the resistor 12 constitute a constant voltage circuit, and the transistor 1
The output voltage, which is the collector of 0, 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 the resistor 14, and the on / off state of the transistor 13 serves as a switch of the constant voltage circuit. That is, when the transistor 13 is turned on, the transistor 10 is turned on and HW
The sensor is energized. The HW sensor includes a heater resistance 15 and a temperature detection resistance 17 installed in the intake manifold.
And the balance resistors 16 and 18 constitute a bridge circuit 20, and the voltages V _H and V _I between the heater resistor 15 and the resistor 16 and between the temperature detecting resistor 17 and the resistor 18 are respectively positive and negative of the comparator 19. It is input to the side terminal and the minus side terminal and is also input to the A / D converter 1d. The output of the comparator 19 is digital input 1
g to detect the balanced state of the bridge circuit 20 of the HW sensor.

The transistor 13 is turned on / off at a cycle of 4.096 msec by the microcomputer 1, and
The W sensor performs duty control in which the energization time ratio is changed to control the average energization current.

Next, the operation of the above configuration will be described. FIG. 2 is a calculation flow chart showing the processing of the system of this embodiment. 4.01m from the microcomputer 1 while the engine is running
The duty signal Do is output from the duty output port 1f every sec, as shown in FIG.
Also, the average energizing current applied to the HW sensor is controlled by controlling the energizing time ratio for turning on / off the transistor 10, and at the same time as the output of the duty signal Do, the voltage V _H between the heater resistor 15 and the resistor 16 and the temperature detection resistor. 17 and the voltage _{V I} of the resistor 18 between Y is loaded into the a / D converter 1d. The reading of V _H and V _I 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
From the deviation _V H -V _I of _H and A / D conversion value _{V I,} the first correction value ΔD01 is retrieved by the table shown in Figure 3. Note that this first correction value ΔD01 is the deviation V _H − of the bridge circuit 20 as can be seen from the table shown in FIG.
It has different values depending on the magnitude and positive / negative of V _I. Next, the correction coefficient k of the first correction value ΔD01 corresponding to the previous air mass flow rate Gair stored in the predetermined address.
Is searched in advance from a table prepared in the microcomputer 1, the first correction value ΔD01 obtained this time is multiplied by a correction coefficient k, and this is set as the true first correction value ΔD01 obtained this time, and the duty signal Correction is made by adding to Do. Simultaneously with the reading of the A / D values V _H and V _I , the signal C from the comparator 19 is read into the digital input 1 g, and the direction of deviation of the balance of the bridge circuit 20 is measured by 1, 0 of this signal C, The duty signal Do is corrected by the second correction value ΔD02 which is a predetermined constant value, and the duty signal Do output from the duty output 1f is reset next time. Finally, the air mass flow rate Gair is obtained from the corrected duty signal Do according to the table of FIG. 4, and is determined from the crank angle signal from the terminal 2, the throttle signal from the terminal 3, the cooling water temperature signal from the terminal 6, etc. Fuel injection amount and injection timing of various engines are calculated, and digital output 1e
The fuel injection valve (not shown) is controlled from the terminal 7. After that, similarly, the air mass flow rate is obtained from the duty signal Do for controlling the average current by intermittently passing the current passed through the HW sensor, and the appropriate feedback control of the engine is performed.

In the above-described embodiment, the correction factor k is determined only by the air mass flow rate Gair, but the operating condition (normal or excessive) of the engine may be added to the determination factor, that is, 1) cooling water temperature Whether the engine has been warmed up by the signal or not, 2) Whether the engine is idle depending on whether the throttle valve is fully closed by the throttle signal and whether the engine speed is a predetermined value or not by the crank angle signal. Otherwise, 3) Obtain the rate of change of the air mass flow rate Gair obtained from the Hw sensor, and if the rate of change is a positive value and its magnitude is a predetermined value or more, it is a negative value and its magnitude is When the value is more than the specified value, it accelerates more than when the value is within the specified range near zero,
It suffices to detect whether the vehicle is decelerating or constant, and determine the correction coefficient k according to each state.

In the above-described embodiment, the correction coefficient k is searched from the table prepared in advance in the microcomputer 1. However, the number is not limited to one, and a plurality of tables corresponding to respective engine states are prepared. I don't mind.

Although the correction coefficient k is determined by the air mass flow rate Gair in the above embodiment, the correction coefficient k may be determined by the duty signal Do obtained last time.

Further, in the above-described embodiment, the basic first correction value ΔD01
Was determined and then multiplied by the correction coefficient k, a plurality of tables of the air mass flow rate Gair and the first correction value ΔD01 corresponding to the operating state of the engine are prepared in advance in the microcomputer 1, and When searching for the correction value ΔD01, the first correction value ΔD01 may be obtained so as to be added to the duty signal Do from a predetermined table corresponding to the previous air mass flow rate Gair and the operating state of the engine.

Further, in the above embodiment, the correction is performed in two steps by the A / D converter 1d and the comparator 19, but the A / D
The comparator 19 may be omitted depending on the accuracy of the converter 1d.

Further, the difference V _H − between the voltage V _H between the heater resistor 15 and the resistor 16 and the voltage V _I between the temperature detecting resistor 17 and the resistor 18 is V _H −.
V _I may be input to the A / D converter 1d via an operational amplifier.

Further, the voltage V _H between the heater resistor 15 and the resistor 16 and the voltage V _I between the temperature detecting resistor 17 and the resistor 18 pass through a transistor or an operational amplifier in the circuit, so that the voltage V A is slightly delayed from the duty signal Do. D converter 1d
In order to eliminate this delay, the duty applied from the constant voltage circuit to the HW sensor can be directly read to improve the accuracy.

Further, as the intake air flow rate sensor, a hot film flow meter can be applied in addition to the HW sensor.

〔The invention's effect〕

As described above, according to the present invention, since the control circuit function of the HW sensor is processed by the microcomputer for controlling the engine, the circuit configuration is simplified, and the error factor can be eliminated to improve the accuracy. 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 the responsiveness can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a calculation flow chart showing the processing procedure of the microcomputer, FIG. 3 is a table for searching the first correction value ΔD01, and FIG.
The figure shows a table for searching the air mass flow rate Gair, the fifth.
FIG. 6 is a time chart of circuit operation, and FIG. 6 is an overall schematic configuration diagram of the present invention. 1 ... Microcomputer, 1a ... CPU, 1b ...
... ROM, 1c ... RAM, 1d ... A / D converter, 1e ... digital output, 1f ... duty output port, 1g ... digital input, 2 ... cranta angle signal terminal, 3 ... throttle signal Terminal, 6 ... Cooling water temperature signal terminal, 15 ... Heater resistance, 17 ... Temperature detection resistance, 16, 18 ... Balance resistance, 19 ... Comparator, 20 ... Bridge circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Masuda, 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Masahiko Miyaki, 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nidec Within the corporation (56) References JP-A-58-95214 (JP, A) JP-A-50-50520 (JP, A)

Claims (4)

[Claims] 1. An intake air amount sensor using a hot wire type air mass flow rate detection mechanism including a bridge circuit composed of a heater resistance, a temperature detection resistance, and a plurality of balance resistances, and an intake air amount is digitally output by an output signal from the sensor. And a means for changing the output signal from the bridge circuit into a digital value, a means for controlling the energization time ratio of the power source applied to the intake air amount sensor, and Means for adding a feedback correction to the energization time ratio according to a digital value; means for calculating an air mass flow rate taken into the engine from the energization time ratio; and a magnitude of the feedback correction value used for the feedback correction. A means for changing the value of the output signal of the intake air amount sensor or the operating state of the engine, The engine control apparatus according to claim and. 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 according to claim 1, wherein the magnitude of the feedback correction value differs depending on the magnitude and the sign of the deviation of the output signal value of the bridge circuit of the intake air amount sensor. Control device. 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, the steady state or the transient state.