JPH0654247B2 - Air flow rate detection device used for control of internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an intake air amount detecting means used as one of means for detecting an operating condition of an internal combustion engine when electronically controlling the internal combustion engine. The present invention relates to an air flow rate detecting device used for controlling an internal combustion engine, which is improved so as to be more appropriately controlled depending on an engine operating state.

BACKGROUND OF THE INVENTION When electronically controlling an internal combustion engine, it is necessary to constantly monitor the operating state of this engine. As a means for monitoring this operating state, engine speed detection means and engine temperature detection means are provided. In addition to the exhaust gas temperature detecting means, the throttle opening detecting means, etc., there are provided intake air flow rate measuring and detecting means.
As this intake air flow rate detecting means, for example, a thermal type air flow rate sensor is known, and this sensor is arranged and set in the intake pipe, and the temperature of the heat sensing element which changes in accordance with the air flow rate. The change state is measured and detected.

That is, a temperature sensitive element having a temperature resistance characteristic is heated and controlled to a constant temperature state by a heating current controlled in an analog manner, and the amount of heat radiated from the temperature sensitive element corresponding to the air flow rate is changed to that of the temperature sensitive element. It is configured to detect and measure by a resistance change. Specifically, the flow rate of air in the intake pipe is measured by changing the value of the current flowing through the temperature sensing element.

However, in such a structure in which the temperature-sensitive element is heated and controlled to a constant temperature by an analogly controlled current, the air flow rate changes 100 times, while the measured current value is It only changes about twice,
Its measurement sensitivity is extremely low. Therefore, in order to use this air flow rate sensor for controlling an internal combustion engine, it is necessary to provide an offset processing means for the detection signal amplification circuit, and the control circuit for that purpose is in a complicated state. .

Further, when the engine control device is configured by using a microcomputer, it is necessary to convert the analog output signal from the sensor into digital data and supply the digital data to the control circuit. The analog-to-digital conversion must be performed with accuracy.
That is, a high-resolution A / D converter and this A / D converter
Extremely high accuracy is required as the reference voltage power supply for the converter.

Further, in addition to such a constant current type resistance wire type, there are those with control means such as a constant temperature type resistance wire type and a constant potential type resistance wire type, but these also have the same problems as described above. It is what

Further, as a temperature-sensitive element control means for solving the above-mentioned problems, it has been considered to control the temperature-sensitive element to a constant temperature by a pulse heating control means. However, even if this pulse heating control means is used, its output value can be made large to some extent, but the accuracy of the pulse cycle for controlling the heating current and the accuracy of control of the heating voltage are also required. Therefore, it is in a state of being restricted by the operating environment. Further, since the pulse control is performed in a cycle unrelated to the internal combustion engine to be controlled,
Problems may occur in engine control signal processing.

[Object of the Invention] The present invention has been made in view of the above points, and has a sufficiently simple structure so that the measurement and detection of the intake air flow rate are performed in a state suitable for the operating state of the engine. In addition, the detection sensitivity of the internal combustion engine should be good, and in particular, the heating control operation of the temperature sensitive element corresponding to the operating state of the engine should be executed to effectively perform signal processing for engine control. The present invention is intended to provide an air flow rate detecting device used in the above.

[Summary of the Invention] That is, an air flow rate detecting device used for controlling an internal combustion engine according to the present invention uses a temperature sensing element of a thermal type air flow rate detecting device by a synchronization signal generated in response to the rotation of the engine. Is controlled in a pulsed manner to generate a measurement detection signal corresponding to the air flow rate, especially when the engine speed changes significantly, for example, when the engine speed becomes a high speed state. , The signal corresponding to the engine speed is divided so that the cycle of the synchronizing signal is set within a stable range to some extent, and the cycle of the pulse signal for setting the heating current synchronization of the temperature sensing element corresponding to this synchronizing signal is set to This is set.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a control device of the engine 11 that executes operation control of the fuel injection amount and the like according to the operation state.
Intake air from the air filter 12 is taken in through an intake pipe 13 and distributed and supplied to each cylinder of the engine 11 through a throttle valve 15 which is driven and controlled by an accelerator pedal 14. Inside the intake pipe 13, a heat-generating temperature sensitive element 17 which constitutes a thermal type air flow rate detecting device 16 is set. As the temperature sensitive element 17, for example, a platinum wire or the like having a temperature characteristic in which heating is controlled by an electric current and a resistance value changes depending on the temperature is used.

The detection signal from the air flow rate detection device 16 is configured by a microcomputer and is supplied to an engine control unit 18 including an engine control processing device. The element 17 is controlled to generate heat.

The engine control unit 18 is also provided with a detection signal from a rotation speed detection device 19 for detecting the rotation state of the engine 11, a cooling water temperature detection signal of the engine 11, an exhaust temperature detection signal, an empty The fuel ratio detection signal or the like is supplied as the operating state detection signal, and in accordance with these detection signals, the fuel injection amount most suitable for the operating state of the engine 11 at that time is calculated, and each cylinder of the engine 11 is calculated. The injectors 20a, 20b, ...
Is supplied as a fuel injection time setting via the registers 21a and 21b. That is, the signal for setting the fuel injection amount in this case is a pulse-shaped signal for which the duty is set, and the injector is valve-opened and the injection fuel amount is set and controlled in the time width. It is a thing.

The rotation speed detection device 19 includes cams 191 and 192 that are rotationally driven coaxially with the engine 11, and a rotary plate 193 that detects a rotation angle provided with a large number of teeth. The cams 191 and 192 and the rotary plate 193 respectively. Against electromagnetic pickup 194
˜196 are set to face each other, and a signal corresponding to a specific rotation angle of the engine 11 and a signal for counting and detecting the rotation angle position are taken out from these pickups 194 to 196.

Fuel pumps are provided for the injectors 20a, 20b, ... Provided for each cylinder of the engine 11, respectively.
The fuel taken out from the fuel tank 23 by 22 is distributed and supplied through the distributor 24. Here, the pressure of the fuel supplied to the distributor 24 is controlled to be constant by the pressure regulator 25, and the fuel injection amount is accurately set and controlled by the valve opening time of the injector calculated above. It is supposed to be done.

The engine control unit 18 also gives a command to the igniter 26, and the ignition coils 28a, 28b provided for each cylinder via the distributor 27,
An ignition signal is distributed and supplied to the engine 11 to execute the operation control of the engine 11 that corresponds to the operation state and that corresponds to the operation state detection signal.

FIG. 2 shows the heat sensing element 17 that constitutes the intake air flow rate detecting device 16 used in the engine control system as described above, and shows the same.
Platinum resistance wire as resistance wire having temperature characteristics for 171
Set 172 winding. On both ends of this bobbin 171,
Shafts 173 and 174, which are made of good conductors, are provided as support shafts, and both ends of the resistance wire 172 are connected to the shafts 173 and 174. And this shaft 17
3 and 174 are supported and set by bins 175 and 176 made of a conductor, respectively, and the resistance wire 17 is connected via these pins 175 and 176.
The heating current is supplied to 2. The resistance wire 172 portion of the heat-sensitive element 17 configured as described above is
The inside of the intake pipe 13 is set to be exposed to the air flow passing through the inside of the intake pipe 13.

FIG. 3 shows another example of the configuration of the heat-sensitive element 17, which is a resistance wire 172 which serves as a heating element having temperature characteristics.
Is formed by a printed wiring or the like on the film 177 made of an insulator, and the film 177 is supported and set by the support substrate 178 made of an insulator. Then, wirings 179a and 179b connected to the resistance line 172 are formed on the surface of the substrate 178 so that the heating current is controlled to be supplied to the resistance line 172.

FIG. 4 shows a circuit configuration according to an embodiment of the air flow rate detection circuit 16 used as described above. Inside the intake pipe 13, as described above, the heating temperature sensing element 17 is provided. Is fixedly set, and an air temperature sensor 30 for measuring the temperature of the circulating air is further fixedly set inside the intake pipe 13. The air temperature sensing element 30 is composed of a resistance wire such as a platinum wire having temperature characteristics similar to the heat sensing element 17, and its resistance value corresponds to the temperature of the air passing through the intake pipe 13. Is to be set. And, both these temperature sensitive elements 17 and 30 and fixed resistance
A bridge circuit is composed of 31 and 32. For this bridge circuit, a constant voltage circuit is used.
The voltage is stabilized via 33 and a heating current for measurement control is supplied. This constant voltage circuit 33 includes a comparator 332 set by the reference power source 331, and this comparator 33.
It is constituted by a transistor 333 controlled by the output of 2.

The output signal from the bridge circuit is detected by the differential amplifier 34.
The output signal from the differential amplifier 34 rises when the temperature of 17 rises to a temperature specified by the air temperature measured by the air temperature sensing element 30. And
The output signal from the differential amplifier 34 resets and controls the flip-flop circuit 35.

The flip-flop circuit 35 is set and controlled by a rotation synchronizing signal corresponding to the rotation operation of the engine not shown in the figure, and this synchronizing signal corresponds to one rotation of the engine 11 from the rotation speed detecting device 19, for example. Generation control is performed on the basis of the signal generated. That is, the flip-flop circuit 35 is set by a synchronizing signal generated for each revolution of the engine 11, and is reset and controlled in response to the temperature rise of the heat-sensitive element 17 up to a specific temperature. The output signal is set and reset so that a set time is set in a time width corresponding to the temperature rising speed of the temperature sensitive element 17, and an output signal which is intermittently controlled in a pulse shape is generated. Then, the output signal from the flip-flop circuit 35 is taken out as an output signal of the air flow rate detecting device 16 via the buffer amplifier 36, and at the same time, the transistor 333 of the constant voltage circuit 33 is controlled to generate heat. A pulsed heating current is supplied to the element 17.

That is, if the rotation synchronizing signal is generated in the state shown in FIG. 5A, the flip-flop circuit 35 is set-controlled as shown in FIG. You will get up. This heating current causes the temperature of the heat-generating temperature sensitive element 17 to rise as shown in (C) of the figure, and the temperature of the temperature sensitive element 17 becomes equal to the air temperature detected by the temperature sensitive element 30. On the other hand, when the voltage rises to a certain value, the output from the differential amplifier 34 rises, the flip-flop circuit 34 is reset, and the heating current is cut off. That is, the heating current for the heat-sensitive element 17 becomes a pulse-shaped signal corresponding to the operating state of the flip-flop circuit 35 as shown in FIG. The period is controlled, and the state corresponding to the temperature rising state of the temperature sensitive element 17 having the pulse width is set.

Here, the temperature rising state due to the heating current of the heating temperature sensitive element 17 is influenced by the heat radiation effect corresponding to the air flow rate flowing through the intake pipe 13, and in the state where the intake flow rate is small,
In contrast to the state shown by the solid line in the diagram (B), when the air flow rate increases, the temperature rising rate becomes slower as shown by the broken line in the figure. Therefore, the set time width of the flip-flop circuit 35 is in a state corresponding to the air flow rate of the intake pipe 13, and the output signal from this circuit 35 is directly used as the air flow rate measurement signal. In this case, by counting the pulse width of the pulsed output signal,
Each air flow rate measurement detection signal can be directly handled as digital data.

In such an air flow rate detection device 16, a heat-sensitive temperature sensor
When the heating pulse current for 17 is applied in synchronization with the rotation cycle of the engine 11, the rotation cycle is, for example, 500 to 10,000 r depending on the operating state of the engine 11.
pm and several tens of times. It is difficult to carry out stable air flow rate detection control for every cycle of a synchronization signal that undergoes such a large cycle change. Further, when the rotation cycle becomes extremely short, the pulse cycle to be measured becomes short, and it becomes difficult to maintain the resolution and measurement accuracy in good states.

FIG. 6 is a diagram for explaining the generation control means of the rotation period signal in consideration of the above points. The rotation speed discrimination circuit 41 of the detection signal of the rotation speed Ne obtained from the engine 11 compares it with the reference value N thereof. , The first state of "Ne>N" and "Ne <
The second state of “N” is determined. In the first state, a command is given to the first pulse generating means 42, for example, a signal synchronized with the rotation of the engine 11 is divided, and the synchronizing signal generating means 43 converts the divided signal into the divided signal. Generate a corresponding rotation synchronization signal. In addition, the above discrimination circuit
When the second determination result is obtained at 42, a command is given to the second pulse generating means 44, and the synchronizing signal generating means 43 generates a signal synchronized with the rotation of the engine 11 as a rotation synchronizing signal. To do so.

That is, when the rotation speed of the engine 11 is lower than the set reference value N, a rotation synchronization signal corresponding to the rotation cycle of the engine 11 is generated, the rotation speed of the engine 11 increases, and the cycle is short. When it becomes, the signal synchronizing with the rotation is divided to be a rotation synchronizing signal for air flow measurement control.

FIG. 7 illustrates the state of the flow of the generation control of the rotation synchronizing signal. First, at step 100, the state of the frequency division flag Xh is discriminated. Then, when the flag Xh is judged to be 0 in step 100, the routine proceeds to step 101, and it is judged in which state the rotational speed Ne of the engine 11 at that time is compared with 4000 rpm. When it is determined that the engine rotation speed Ne is less than 4000 rotations, the frequency division flag Xh remains 0 and is ended. When the rotation speed Ne is equal to or greater than 4000 rotations, the routine proceeds to step 102, where the frequency division flag Xh is converted to 1 and terminated.

When it is determined in step 100 that the flag Xh is 1, the process proceeds to step 103, in which the engine is
The state in which the rotation speed Ne of 11 is 3000 rotations is determined. When it is determined that the rotation speed Ne is less than 3000 rotations, the routine proceeds to step 104, where the frequency division flag Xh is converted to 0 and the processing is terminated. If it is determined in step 103 that the rotation speed Ne is 3000 rotations or more, the routine ends.

That is, the engine speed is 3000 rpm and 4000 rpm
Based on the rotation, the state of the number of rotations is discriminated, the frequency division flag Xh is converted and controlled with the hysteresis characteristic,
The operation of the rotation speed determination circuit 41 is executed.

FIG. 8 illustrates the process of generating a rotation synchronizing signal corresponding to the frequency division flag Xh. In step 200, the state of the frequency division flag Xh is first determined. When the flag Xh is determined to be 0 in step 200, the process proceeds to step 201, and the signal synchronized with the rotation of the engine 11 is taken out as a pulse output as it is, and then the skip flag Xs is set to 1 in step 202. And end. When it is determined in step 200 that the flag Xh is 1, the process proceeds to step 203, in which the state of the skip flag Xs is determined. If the flag Xs is 0, the process directly proceeds to step 201 and the engine 11
The rotation synchronization signal is output in synchronization with the rotation of the. When the flag Xs is 1, the signal synchronized with the rotation from the engine 11 is skipped and the pulse signal is not generated, and the process proceeds to step 204, and the skip flag Xs is set to 0 in this step 204.

That is, the frequency division flag Xh is controlled and set according to the state of the engine speed, and the frequency division flag Xh is set to 1
In this state, the signal corresponding to the rotation of the engine 11 is skipped every other signal, and the signal synchronized with the rotation of the engine 11 is
A rotation synchronizing signal divided by two is generated.

In the above embodiment, the range is set according to the engine rotation speed, and the signal corresponding to the engine rotation is divided in the high speed rotation region. However, the setting relationship between the engine speed and the generation cycle of the rotation cycle signal is set and stored, and the stored rotation synchronization signal cycle corresponding to the engine speed is read out to control the generation of this synchronization signal. May be performed.

As described above, according to the present invention, the intake air flow rate can be measured and detected in the state most suitable for the operating state of the internal combustion engine such as the engine, and its detection sensitivity is also sufficiently good. can do. In particular, since the air flow rate detection operation can be executed in a state corresponding to the engine rotation state, control of the engine operating state such as fuel injection amount control can be executed very effectively. Even in the correspondence relationship, the air flow rate measurement is performed with sufficient resolution and accuracy even when the engine is in a high-speed rotation state, for example, and a great effect is exerted in improving the control accuracy of this type of control device. It is a thing.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a control device for an internal combustion engine related to the present invention, and FIGS. 2 and 3 show a configuration example of a heat-sensitive temperature sensing element of an air flow rate detecting device used in the above embodiment. 4 and 5 are circuit configuration diagrams illustrating an air flow rate detecting device according to an embodiment of the present invention, FIG. 5 is a waveform diagram illustrating an operating state of the upper air flow rate detecting device, and FIG. FIGS. 7 and 8 are flow charts for explaining the rotation synchronizing signal generating means for controlling the heating current in the flow rate detecting device, and FIGS. 11 …… Engine, 13 …… Intake pipe, 15 …… Throttle valve,
16 …… Air flow rate detector, 17 …… Exothermic temperature sensor, 18 ……
Engine control unit, 19 ... Rotation speed detection device, 30 ...
... Air temperature sensor, 33 ... Constant voltage circuit, 34 ... Differential amplifier, 35 ... Flip-flop circuit, 41 ... Rotation speed discrimination circuit, 42, 44 ... First and second pulse generation means, 43 ...
... Rotation synchronization signal generating means.

Claims (3)

[Claims] 1. A temperature-sensitive element having a temperature characteristic in which heat generation is controlled by a heating current arranged and set with respect to an intake system of an internal combustion engine, and a synchronization signal generated in synchronization with rotation of the engine. Rise, means for generating a pulsed signal for setting the heating current for the temperature sensitive element, and the temperature of the temperature sensitive element controlled by the pulsed heating current generated by this means as the intake air temperature. The means for setting the heating pulse width of the pulse-shaped signal in response to the rise of the temperature-sensing element to the specific temperature, and the pulse-shaped signal having the heating pulse width set for the pulse time. It is used for control of an internal combustion engine, characterized by comprising: a means for outputting a signal having a width corresponding to an air flow rate; and a means for variably setting a generation cycle of the synchronization signal in accordance with a rotation speed of the engine. Air flow detecting device. 2. The means for variably setting the generation cycle of the synchronizing signal divides the engine speed into specified engine speeds,
When the engine speed is lower than the boundary frequency set by this partition, a synchronization signal is set in response to the engine speed, and when the engine speed is higher than the boundary frequency, the signal corresponding to the engine speed is divided. The air flow rate detecting device used for controlling the internal combustion engine according to claim 1, wherein the frequency-divided signal is used as a synchronizing signal. 3. The boundary frequency is set to be higher when the engine speed is increased and when it is decreased, and the boundary frequency is set higher when the engine speed is increased than when it is decreased. An air flow rate detection device used for control of an internal combustion engine according to claim 2.