JPH07166948A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a control device for an internal combustion engine which avoids repetitive adjustments and automates adjustments. CONSTITUTION:An engine-controlling computer 18 performs arithmetic to calculate the optimum resistance values of variable resistances (14, 16, 20, 48, 50, 52, 54, 64) and a semiconductor switch 6 is turned on and off according to computer outputs (O1-On) to obtain the desired resistance values. Since the optimum values of the resistances constituting a hot-wire type airflow meter are calculated using the computer, repetitive adjustments can be avoided and adjustments can be automated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for adjusting a hot wire air flow meter.

[0002]

2. Description of the Related Art As one of known intake air flow rate measuring devices for internal combustion engines (hereinafter abbreviated as an air flow rate sensor), a heating resistance element having temperature dependency and an air temperature compensating resistance element are provided in an intake air flow. There is a device for detecting the air flow rate by controlling the current flowing through the heating resistance element so as to keep the temperature difference between both resistance elements constant and detecting the amount of electricity corresponding to the current. It is known from Japanese Patent Laid-Open No. 61-137017 that a microprocessor is used to control the current flowing through the heating resistance element. However, the conventional device is completely independent of the microcomputer for controlling the internal combustion engine. I was using it. The microcomputer for controlling the internal combustion engine utilizes ignition speed, fuel injection amount, etc. by utilizing measured quantities such as the rotation speed signal N of the internal combustion engine, the air-fuel ratio signal λ from the O ₂ sensor, and the air amount Qa from the air flow rate sensor. Control, but
A general hot-wire intake air amount sensor is provided with a heating resistance element and an air temperature compensating resistance element in an intake pipe of an internal combustion engine, and converts them into a predetermined analog or digital signal by a signal processing device provided near these resistance elements. , Supplies signals to the microcomputer. The sensor is also provided with a current control device for controlling the current flowing through the heating resistance element so that the difference in electric resistance between the heating resistance element and the air temperature compensation resistance element, that is, the temperature difference becomes a predetermined value. ing.

[0003]

The response adjustment of the hot wire type air flow meter, the temperature setting of the heating resistor, and the adjustment of the output characteristic are performed by the variable resistors (14, 16, 20, 48, 50, shown in FIG. 1).
52, 54, 64) while observing the results, the laser trimming or the like was repeatedly performed at least three times or more. This method has a problem that it takes time because of repeated adjustment.

It is an object of the present invention to provide a control device for an internal combustion engine, which automatically avoids and adjusts the repetitive adjustment.

[0005]

The above object is achieved by adjusting the variable resistance element in a thermal type flow meter by the output of a computer.

[0006]

As the adjustment, the response adjustment, the temperature setting of the heating resistor and the output characteristic are adjusted. Here, the adjustment of the output characteristic (adjustment of the resistors R52, R54, R56 and R64) will be described. The relationship between the input and output of the amplifier 58 is given by equation 12. Since there are four unknowns, R52, R54, R56, and R64, the input / output values V _IN + and V58 of the amplifier 58 are measured at four different air flow rates, and the resistance values R52, R54,
R56 and R64 are calculated and the computer output (O ₁
-O _n ) turns ON / OFF the semiconductor switch to obtain a desired resistance value. By this method, it is possible to avoid the repeated adjustment of the resistance value and realize the automation of the adjustment.

[0007]

1 is a circuit diagram showing an embodiment of the present invention, in which a heating resistor element 2 and an air temperature compensating resistor element 4 placed in an intake air flow to an internal combustion engine are mounted on a ceramic bobbin (not shown). It is a wound platinum wire, and its resistance value changes as the temperature rises. Platinum is a material generally used as a temperature reference, has a linear resistance-temperature characteristic, and is chemically stable. The surface of the platinum thin wire is glass-coated, and the resistance values and temperature characteristics of the resistance elements 2 and 4 are substantially equal. Now, the resistance value at temperature 0 ℃ resistive elements 2 each R _20, R _40, when a temperature coefficient alpha, the resistance value R _2, R ₄ at the temperature T _2, T ₄ of each element by the following equation Represented.

[0008]

## EQU1 ## R ₂ = R ₂₀ (1 + αT ₂ ) (1)

[0009]

[Number 2] _{R 4 = R 40 (1 +} αT 4) ... (2) T 2: temperature T of the heating resistor element 2 _4: Power Temperature resistance element 2 of the temperature compensating resistance element 4 via the collector-emitter circuit of the transistor 6 8 And controlling the base current of the transistor 6, the magnitude of the current flowing through the resistance element 2 is adjusted. Resistance element 2 and resistance element 4
Are grounded through fixed resistors 10 and 12, respectively.

The variable resistance elements 14 and 16 connected in parallel to the resistance element 2 are used to set the temperature of the resistance element 2 and are adjusted by the output of the microcomputer 18 as described later. A variable resistor 20 is further connected in series to the air temperature compensating resistor element 4, and the air temperature compensating resistor element 4 is adjusted by adjusting the value of this resistor.
The sensitivity of is adjusted.

The positive phase input terminal 24 of the amplifier 22 is connected to the connection point between the resistance element 2 and the fixed resistor 10, and the negative phase input terminal 26 is connected to the connection point between the fixed resistor 12 and the resistance element 4. It On the other hand, the positive phase input terminal 30 of the amplifier 28 is connected to the connection between the variable resistance element 34 connected to the output terminal 32 of the amplifier 22 and the variable resistance element 20, and the negative phase input terminal 3 is connected.
6 is connected to the connection point of the variable resistors 14 and 16. Further, the positive phase input terminal 30 of the amplifier 28 is grounded via a variable resistor 38 and a variable capacitor 40 which are connected in series. The variable resistor 38 and the variable capacitance 40 constitute a phase delay compensation circuit 42 that changes the transient characteristic of the air flow rate measuring device, and the transient characteristic (step response) of the hot wire type air flow rate sensor is obtained as shown in FIG. Change to reduce the time to reach the final value. Therefore, there is no change in static characteristics.

The output terminal 44 of the amplifier 28 is a resistor 46.
Is connected to the base of the transistor 6 via the control circuit, and the base current of the transistor 6 is controlled so that the temperature difference between the heating resistance element 2 and the air temperature compensating resistance element 4 becomes constant. adjust. 2 connected in series
The connection point of the two variable resistors 48 and 50 is connected to the negative phase input terminal 26 of the amplifier 22. These resistors 4
8 and 50 are connected to the power source 8, and the response time of the sensor can be adjusted by adjusting the value. Further, variable resistors 52 and 54 connected in series are connected to the power source 8, and the connection point is connected to the negative phase input terminal 60 of the amplifier 58 via the variable resistor 56. The positive phase input terminal 62 of the amplifier 58 is connected to the positive phase input terminal 24 of the amplifier 22,
The negative phase input terminal 60 is further connected to the output terminal 66 via the variable resistor 64. Variable resistors 52, 54, 56,
64 is adjusted by the output O ₁ ~ O _n microcomputer 18 as will be described later, the output characteristic with respect to the air flow rate changes.

An analog signal corresponding to the air flow rate generated at the output terminal of the amplifier 58 is converted into an analog-digital converter 6
After being converted into a digital signal at 8, it is given to the microcomputer 18.

The component 70 shown by the alternate long and short dash line in FIG. 1 is arranged on a single insulating substrate or is integrally integrated on a single semiconductor substrate. Therefore, the transistor 6 is arranged in the vicinity of the heating resistance element 2 and the air temperature compensation resistance element 4 which are grounded in the air intake pipe of the internal combustion engine, or in the vicinity of the component 70. The microcomputer 18 usually includes a heating resistor element 2 and an air temperature compensating resistor element 1 to
Since the distance is 2M, the transistor 6 and the component 70 are connected by an electric wire in the former case, and the resistance elements 2 and 4 are connected in the latter case.
The transistor 6 and the transistor 6 are connected by an electric wire, but in either case, since the amount of electricity is large, there is almost no influence of noise.

The microcomputer 18 constitutes a part of the air flow rate sensor, and also the fuel injection amount signal T in accordance with the air flow rate signal Qa, the rotation speed signal N of the internal combustion engine, the air-fuel ratio signal λ from the O ₂ sensor, and the like. _i , Ignition timing signal T _a is output.

In the above configuration, the variable resistors 14 and 16
The sum of the resistance values of is set to be sufficiently larger than the resistance value of the heating resistance element 2. At this time, the balance condition of the circuit is expressed by the following equation.

[0017]

[Formula 3] R ₁₀ · R ₄ = K · R ₁₂ · R ₂ (3)

[0018]

[Equation 4]

By substituting the relationships of the equations (1) and (2), the following relationship can be obtained for the temperature difference ΔT.

[0020]

[Equation 5]

R ₁₀ : resistance value of the resistor 10 R ₁₂ : resistance value of the resistor 12 R ₁₄ : resistance value of the resistor 14 R ₁₆ : resistance value of the resistor 16 Heat generation amount Q of the heating resistor element 2 and carried away by air flow From the balance of heat quantity, the following equation holds.

[0022]

[Equation 6]

[0023]

[Equation 7]

Here, C ₁ and C ₂ : constants u: flow velocity I: current flowing through the heating resistance element 2 K ′: constant represented by the following equation

[0025]

[Equation 8]

That is, the amount of heat generated is a quadratic function of the square root of the flow velocity when the temperature difference ΔT between the heating resistance element and the ambient temperature is constant. The current I flowing through the heating resistance element 2 is a function including only the flow velocity u, and therefore the flow velocity can be measured only by the terminal voltage of the resistor 10.

Next, the terminal voltages V ₂ of the temperature sensitive resistance elements 2 and 4,
When calculating the ratio of V ₄ ,

[0028]

[Equation 9]

Therefore, even if the resistance elements 2 and 4 having the same specifications are used,

[0030]

[Equation 10]

Therefore, if the resistance value R ₁₂ of the fixed resistor 12 is set sufficiently higher than the resistance value R ₁₀ of the fixed resistor ₁₀ , the voltage applied to the resistor 4 is sufficiently smaller than the voltage applied to the resistance element 2. Therefore, accurate temperature compensation is possible without generating self-heating. Regarding the above measurement principle, Japanese Patent Laid-Open No.
-43447 for more details.

FIG. 2 is an example of a flow chart for adjustment of the air flow rate sensor shown in FIG. 1. By sequentially executing the processes I to IV, the variable resistors 14, 16, 3 of FIG.
The resistance values of 4, 38, 20, 48, 50, 56 and 64 are determined.

I is a response time adjustment process, and the values of the resistors 48 and 50 are determined by the flow chart shown in FIG. Reference numeral II is a temperature setting process for the heating resistor element 2, which is performed by changing the resistors 14 and 16. III is an intake air temperature adjustment process, which changes the value of the resistor 10 to change the sensitivity of the intake air temperature detecting resistance element 4.

IV is an input / output characteristic adjustment process, which is performed when the flow rate is low (1
Adjust the analog output characteristics of the air flow rate sensor with respect to the flow rate so that the voltage at the two points (0 kg / h) and the high flow rate (200 kg / h) will be the specified values. This process changes resistors 52, 54, 56, 64. The resistance value data determined by the series of adjustments is written in the ROM in the microcomputer 18. Now, the resistance values of the resistors ₅₂ , ₅₄ , ₅₆ and ₆₄ are resistors R ₅₂ , R ₅₄ , R ₅₆ and R _{64 respectively} , the power supply voltage is Ve, and the amplifier 5
When the output voltage of 8 is V ₅₈ and the positive phase input terminal voltage of the amplifier 58 is V _IN +,

[0035]

[Equation 11]

Is satisfied. When the above formula is transformed

[0037]

[Equation 12]

[0038] V _IN + is a voltage value indicating the flow rate, and the resistance values R ₅₂ , R ₅₄ , R ₅₆ , and R ₆₄ are adjusted to adjust the input / output characteristics of the hot-wire flow sensor.

FIG. 4A shows a detailed configuration example of the variable resistor shown in FIG. Fixed resistors 84 to 94 connected in series between the output terminals 80 and 82, switching semiconductor switches 96 to 106 connected in series to the fixed resistors, and semiconductors connected in parallel to the fixed resistors 84 to 94. The switches 108 to 118 and the semiconductor switches 120 and 122 are arranged in a circuit that connects the connection points of the resistors in a ladder shape. Microcomputer 1
When the eight output signals O _{1 to} O ₁₄ are given to each semiconductor switch, the semiconductor switch is turned on or off, and the resistance value can be changed. For example, when the voltage of O ₁ is set to HIGH, the switch 108 is turned on and the resistor 84 is short-circuited. In this way, the resistance value of the variable resistor can be adjusted by the digital signal from the microcomputer 18. FIG. 4B shows the configuration of the variable capacitor 40. However, the configuration is only the fixed resistance group of FIG.

FIG. 5 is a block diagram showing another embodiment of the present invention, which is a heating resistor element 150 for measuring the air flow rate.
Then, the current detection resistor 152 is connected in series and is connected to the power supply unit 154. The resistor 156 for measuring the air temperature is
The resistor 158 for current detection is connected in series and is connected to the power supply unit 154. Microcomputer 160
Selects the voltage V ₂ of the resistor 152 and the terminal voltage V ₃ of the resistor 158 by the multiplexer 162, converts it into a digital signal by the analog-digital converter 164, and then takes it in the inside. The microcomputer 160 calculates the temperature T _H and the air temperature T _a of the heating resistor element 150, the difference T _H -
The supply voltage of the heating resistor element 150 is controlled so that T _a becomes constant. The microcomputer 160 calculates the voltage V ₁ that is fed back to the heating resistance element 150, and outputs the voltage V ₁ through the digital-analog converter 166 and the power supply unit 154. The multiplexer 162, the analog-digital converter 164, the microcomputer 160, and the digital-analog converter 166 are arranged on the same insulating substrate or semiconductor substrate. In addition, the microcomputer 160
Determines the ignition timing and the fuel injection amount according to the air flow rate, the rotation speed of the internal combustion engine, and the output of the O ₂ sensor.

Heating resistor 150 and air temperature compensating resistor 15
The relationship between the temperature of 6 and the resistance value is shown by the following equation.

[0042]

[Formula 13] R _H = R _H0 (1 + α · T _H ) (13)

[0043]

[Formula 14] R _K = R _K0 (1 + α · T _a ) ... (14) where, R _H : resistance value of the heating resistance element 150 R _H0 : value of R _H when T _H = 0 R _K : air temperature Resistance value of compensation resistor 156 R _K0 : Value of resistance value R _K when T _a = 0 α: Temperature coefficient of resistance

[0044]

R _H = (V ₁ −V ₂ ) / (V ₂ / R ₁ ) ... (15)

[0045]

## EQU16 ## R _K = (V ₄ −V ₃ ) / (V ₃ / R ₂ ) ... (16) R ₁ : the value of the resistor 152 R ₂ : the value of the resistor 158. )Than

[0046]

[Equation 17]

[0047]

[Equation 18]

It becomes

The output voltage V ₁ is determined by the following PID control. For example, when controlling so that T _H −T _a is 200 ° C.,

[0050]

Equation 19 becomes _{V IN + 1 = V IN +} K 1 (ΔT N -200) + K 2 (ΔT N -ΔT N-1) + K 3 Σ (ΔT N -200) ... (19).

[0051] Here K _1, K _2, K ₃ is a constant, ΔT = T _H -
T _a n + 1 indicates the next time, n indicates the current time, and n−1 indicates the previous time.

The air flow rate can be obtained from King's equation. King's formula shows the relationship between the power of the heating resistor and the amount of heat dissipation,

[0053]

Equation 20] _{^{I 2 = (C 1 + C}} 2 √Qa) (T H -T a) ... represented by (20). Here, Qa: Air flow rate I: Current flowing through heating resistance C ₁ , C ₂ : Function of air temperature

[0054]

[Equation 21]

It becomes T _H −T _a is constant under the control of the microcomputer, and C ₁ and C ₂ use the values previously written in the ROM according to the air temperature T _a . Also, I ²
R _H can be calculated by I ² R _H = V ₂ · (V ₁ −V ₂ ) / R ₁ .
Therefore, the air flow rate Qa can be calculated by the equation (21).

FIG. 6 shows a method of adjusting the air flow rate sensor shown in FIG. F1 is a flow chart for determining the resistance values R _H0 and R _K0 , F2 is for determining the constants C ₁ and C ₂ , and F3 is for determining the response speed to the change in the air flow rate. .

FIG. 7 is a diagram showing another embodiment of the present invention.
The constant current power supplies 169 'and 169 are respectively the heating resistance element 1
70, a current is passed through the resistance element 172 for air temperature compensation. The switch 174 is turned on by the microcomputer 176 at a constant cycle T. When the switch 174 is turned off when the terminal voltage of the heating resistance element 170 exceeds the threshold value, the current flow ratio D (D = current flow time / T) becomes

[0058]

[Expression 22] D = K ₁ + K ₂ √Qa (22), which is a function of the air flow rate Qa.

Here, K ₁ and K ₂ are functions of the air temperature, and the threshold value changes depending on the air temperature and is determined so as to satisfy the following equation.

[0060]

(Equation 23) (Terminal voltage of heating resistance element) = K · (Terminal voltage of resistance element for temperature correction) (23) Here, K is a constant.

Terminal voltages of the heat generating resistance element 170 and the temperature compensating resistance element 172 are selectively taken in by the multiplexer 178, and the analog-digital converter 180 is provided.
Is input to the microcomputer 176 via. The microcomputer 176 also controls the fuel injection amount of the internal combustion engine and controls the ignition timing. These multiplexer 178, analog-digital converter 180,
The microcomputer 176 is arranged on the same insulating substrate or semiconductor substrate as in FIG.

FIG. 8 shows a method of adjusting the air flow rate sensor shown in FIG. The flow charts F1 and F2 are shown in FIG.
It is executed with the ROM writer attached to the microcomputer. F1 is for determining the k of the formula (23) is set so that relationship between the temperature T _H and T _a at threshold is constant. F2 is for setting K ₁ and K ₂ in the equation (22).

FIG. 9 shows a software system of an internal combustion engine control device for an automobile, which includes a start ST, internal combustion engine control interrupts IR _{1 to} IR _n , a start process PST, an internal combustion engine control interrupt process PIR _{1 to} PIR _n , and a task. It has a scheduler TS and control tasks T _{1 to} T _n . Further, an air flow sensor interrupt IR _AON for online processing for measuring the air flow rate, an air flow sensor offline adjustment interrupt IR _AOF , an air flow sensor online interrupt processing PI _RAON , an air flow sensor offline interrupt processing P
I _RAOF , an air flow sensor adjustment task T _OFAIR , and an online process T _ONAIR for measuring the flow rate of the air flow sensor are provided. In the apparatus configured as shown in the figure, at the adjustment stage of the air flow sensor, the interrupt IR for offline adjustment is used.
_AOF , air flow sensor offline interrupt processing P
Adjustment is performed by I _RAOF and the adjustment task T _OFAIR . The adjustment task T _OFAIR is the flow chart shown in FIG. 2 for the air flow sensor shown in FIG. 1, and the flow chart shown in FIG. 6 for the sensor shown in FIG.
The flowchart shown in FIG. 8 corresponds to the sensor shown in FIG.

After the adjustment is completed, when the internal combustion engine is in operation, the air flow sensor interrupt IR _AON for online processing, the online interrupt processing PI _RAON , and the online processing T _ONAIR for flow rate measurement are used.
_ONAIR is the processing such as calculation control for air flow measurement. The offline adjustment interrupt IR _AOF , the offline interrupt processing PI _RAOF , the adjustment task T _OFAIR and the air flow sensor interrupt IR _AON , the online interrupt processing P
I _Raon, online processing T switching of _ONAIR for flow measurement is carried out in such a manual switch, for example.

FIG. 10 shows the relationship between the OS during operation of the internal combustion engine, the air flow sensor interrupt IR _AON for online processing, and the task T _ONAIR . In the figure, AD is analog
Digital conversion, PRO is a process for air flow measurement, D
O is a write to the output and the output register. In the task control shown in the figure, the air flow sensor interrupt IR _AON
When is added in time synchronization or rotation synchronization, a task T _ONAIR consisting of analog-digital conversion AD, processing PRO for air flow rate measurement, and output and writing DO to the output register is executed under the control of the OS.

FIG. 11 shows a method of diagnosing an air flow sensor abnormality. In the air flow sensor shown in FIG. 5, the terminal voltage of the current detecting resistor 152 fluctuates depending on the flow rate and temperature.
The width of change is limited in advance. After the terminal voltage is taken into the microcomputer 166 through the analog-digital converter 164, it is determined whether the voltage exceeds a preset voltage. If it exceeds, it is determined to be abnormal, and the terminal voltage is automatically set so that the vehicle does not lose the necessary minimum traveling function, and the driver is provided with the information. The flowchart is shown in FIG.

Further, in the air flow rate sensor shown in FIG. 7, when the abnormality is diagnosed, the terminal voltage of the heating resistor 170 is checked while the switch 174 is on, and the determination is made. The abnormality diagnosis of the temperature compensation resistor 172 can be performed regardless of whether the switch 174 is on or off.

According to the present invention, there is provided a small-sized and inexpensive intake air amount measuring device which is less likely to malfunction even if noise is mixed in the wiring from the detection resistance element of the flow rate sensor to the microcomputer for controlling the internal combustion engine. Can be provided.

[0069]

According to the present invention, the optimum value of the resistance of the hot-wire type air flow meter is calculated by the computer, so that repeated adjustment can be avoided and the adjustment can be automated.

[Brief description of drawings]

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

FIG. 2 is a view showing a flow chart of adjustment.

FIG. 3 is a diagram showing a flowchart of response time adjustment processing.

FIG. 4 is a diagram showing a variable resistor for adjustment.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing a flowchart of adjustment processing.

FIG. 7 is a diagram showing another embodiment of the present invention.

FIG. 8 is a diagram showing a flowchart of adjustment processing.

FIG. 9 is a diagram showing a software system of a microcomputer.

FIG. 10 is a diagram showing processing by a microcomputer.

FIG. 11 is a diagram illustrating the principle of abnormality diagnosis.

FIG. 12 is a diagram showing a flowchart of abnormality diagnosis.

FIG. 13 is a characteristic diagram for explaining phase delay compensation.

[Explanation of symbols]

2 ... Heating resistance element, 4 ... Air temperature compensation resistance element, 8 ...
Power supply, 18 ... Microcomputer, 68 ... Analog-digital converter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoji Inui 4, 6 Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi, Ltd. (72) Masaji Suda Inventor, Katsuta City, Ibaraki 2520 Takaba, Takaba, Ltd. Hitachi, Ltd. Factory Sawa Factory

Claims (3)

[Claims] 1. An engine control device comprising a thermal air flow meter and a digital computer, wherein a variable electric element in the thermal air flow meter is adjusted by the output of the computer. 2. The calculation process of the computer according to claim 1, comprising an online process for measuring an air flow rate and an offline process for the adjustment, and switching between the online mode and the offline mode is an interrupt process of an external switch signal. An internal-combustion-engine control device, characterized in that: 3. The control device for an internal combustion engine according to claim 1, wherein the adjustment is response adjustment of a hot-wire air flow meter, temperature setting of a heating resistor, and output characteristic adjustment.