JPS6263159A - Controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To detect the intake air quantity with high precision by obtaining the time interval between a start pulse signal and the start pulse signal generated in precedence and obtaining the intake air quantity per revolution of the engine on the basis of the time interval. CONSTITUTION:When the start pulse signal Tin is generated from an ECU 20, synchronized with the engine speed, an FF circuit 19 is set, and a transistor Tr17 is set-ON, and a temperature sensing element 12 conducts electricity. Then, the temperature of the temperature sensing element 12 rises in inverse proportion to the intake air quantity. When, the temperature rises until the temperature difference specified by the air temperature measured by a temperature measuring element 13 is generated, the FF circuit 19 is reset by the output of a comparator 18, and the Tr17 is turned-OFF. Then, the intake air quantity per revolution of the engine is obtained from the measured air flow rate obtained from the pulse time width of the output signals in pulse form outputted from the FF circuit 19 and the engine speed, and the fuel injection quantity is calculated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention improves a means for measuring intake air flow rate particularly for an engine, so that, for example, the fuel injection amount corresponding to the operating state of the engine can be appropriately controlled. The present invention relates to a control device for an internal combustion engine.

[Background Art] When an internal combustion engine, such as an engine installed in a car, is electronically controlled, the operating state of the engine is monitored and the amount of fuel injection, etc., corresponding to the operating state is controlled using a microcomputer or the like. It is calculated by an electronic control unit and controls the amount of fuel injected.

Here, the fuel injection amount is basically calculated based on the intake air amount, and therefore, a means for measuring the intake air flow rate is important as a means for monitoring the operating state of the above-mentioned Nishijin. Various types of such air flow rate measuring means have been proposed, and for example, a thermal type air flow rate measuring device as disclosed in Japanese Patent Application Laid-Open No. 55-98621 is known.

In such a thermal air flow measuring device, for example, a temperature sensing element whose resistance value is set according to the temperature is installed in the intake pipe, and heating power is supplied to this temperature sensing element. The temperature sensing element is configured to control heat generation. in this case,
Since the temperature sensing element is exposed to the intake air flow, the temperature increase characteristic due to heating power is influenced by the intake air flow rate. Therefore, for example, by observing the amount of heating power required to maintain the temperature of the temperature sensing element at a specified temperature state, intake air flow rate data can be obtained.

However, the air flow measurement signal obtained by such an air flow measurement device is expressed by analog data based on a current value. On the other hand, the control unit of the engine is usually constituted by a digital circuit such as a microcontroller, and the measurement signal is converted into digital data by a high-precision A/D conversion means and then converted into digital data. to be taken into the control unit.

become. That is, a highly accurate signal conversion means is required, and its configuration is necessarily complex and expensive in order to execute highly accurate engine control.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned points. etc. so that it can be effectively incorporated into the control unit using
It is an object of the present invention to provide a control device for an internal combustion engine that allows more accurate fuel injection amount control to be effectively executed.

Another object of the present invention is to perform the above-mentioned air flow rate measurement in synchronization with the rotation of the engine so that fuel injection amount control can be executed more effectively. Even in situations such as this, stable and accurate intake air flow measurements are always performed
An object of the present invention is to provide a control device for an internal combustion engine that allows stable engine control to be performed.

[Means for Solving the Problems] That is, the internal combustion engine control device according to the present invention includes a thermal air flow rate measuring device having a temperature sensing element having temperature/resistance characteristics set in the intake pipe. The temperature sensing element of this 811 constant device is supplied with heating power that rises based on a start pulse signal synchronized with the rotation of the engine.

Then, when the temperature of the thermosensing element rises to a specified temperature state, the heating power is cut off and a measurement output signal representing the supply time width of the heating power is generated. Further, when the start pulse signal is generated, the time interval between that pulse signal and the start pulse signal generated before it is determined, and based on this time interval and the above-mentioned intake air flow rate all constant signal, one revolution of the engine is determined. The per unit intake air amount G/N is determined, and the basic fuel injection amount is calculated based on this G/N.

[Function] In the intake air flow measuring means of the control device as described above, when heating power is set to be supplied to the temperature sensing element,
The heating power supply time width required for the temperature sensing element to rise to a specified temperature state comes to express the measured air amount. However, this heating power supply time width is also influenced by the temperature state of the temperature sensing element at the time of rising of the heating power.

In other words, the above measurement signal is affected by the time interval of the start pulse signal that controls the rise of the heating power, and if there is variation in the interval of the start pulse signal, there will be variation in the time width of each measurement signal. occurs. The time width expressed by this air flow rate measurement signal is influenced by the previous measurement time interval, but here it is the time between the start pulse signal corresponding to that measurement and the previous start pulse signal. Based on this time interval and the time width signal representing the measured air flow rate, the intake air ff1G per engine revolution is calculated.
/N is calculated, and the basic fuel injection amount is calculated based on this G/N. Therefore, even if the start pulse signal interval varies, stable intake air amount data G/N can always be obtained, and calculation control of the amount of fuel injected into the engine can be executed reliably. It is something that becomes.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an air flow rate measuring device for measuring the flow rate of intake air flowing into an intake pipe 11 of an internal combustion engine. It is set in contact with the intake air flow.

Here, the temperature sensing element 12 and the temperature measuring element 13 are
Both are constructed of a resistance element made of, for example, platinum wire, which has a temperature-resistance characteristic in which the resistance value is set to change depending on the temperature.

A fixed resistor 14 is connected in series to the temperature sensing cord 12, and resistors 15 and 16 are connected to the temperature measuring element 13.
A series circuit is connected to the temperature sensing element 12.
, temperature measuring element 13, - and resistors 14 to 1B form a bridge circuit. and,
Heating power that is turned on and off by a transistor 17 is supplied to the connection point between the temperature sensing element 12 and the temperature resistance element 13, which is the input end of this bridge circuit. Further, the output portion at the connection point a1 between the temperature sensing element 12 and the resistor 14 and the connection point A between the resistors 15 and 16 is output from the comparator IB.
This comparator 18 is designed to compare the voltages at points a and b. Specifically, heating power is supplied to the temperature sensing element 12,
The output signal from the comparator 18 is set to rise when the temperature rises to a point where a specified temperature difference with respect to the intake air temperature measured by the temperature measuring element 13 is set. And this comparator 1
The output signal from 8 resets and controls the flip-flop circuit 19.

This flip-flop circuit 19 is set and controlled by a start pulse signal Tin generated from an engine control unit 20. This start pulse signal is a signal synchronized with the rotation of the engine that is supplied to the control unit 20, specifically, the crank angle 180 of the engine.
'Generated in correspondence to the signals generated for each CA.

This flip-flop circuit 19 generates a signal that becomes high level in its set state, and the output signal from this flip-flop circuit is taken out via a buffer 21 and supplied to an output circuit 22. It is supplied to the base of the transistor 17. That is, the transistor 17 is controlled to be turned on when the flip-flop circuit 19 is in the set state, and is set to supply heating power to the bridge circuit including the temperature sensing element 12.

In this case, the voltage of the heating power is compared with the reference voltage set by the reference voltage power supply 24 in the OP amplifier 23,
The base bias of the transistor 17 is controlled by the output signal from the OP amplifier 23, and the voltage value of the heating power supplied to the temperature sensing element 12 is set as a reference.

As described above, the flip-flop circuit 19 outputs a pulse-like signal that is at a high level in its set state, and the pulse time width of this pulse-like signal is the same as that of the temperature-sensitive cord 12. This corresponds to the heating power supply time width for Then, in the output circuit 22, the pulse-like signal is appropriately waveform-shaped to become a signal expressing the pulse time width T out, and the output signal from the output circuit 22 is used as an intake air flow rate measurement signal. It is taken into the engine control unit 20.

Here, the output circuit 22 generates a pair of pulse signals corresponding to the rise and fall of the pulse-like signal from the flip-flop circuit 19, respectively, and the time width T out is determined by the time interval between the pair of pulse signals. In other words, the signal taken into the control unit is the flip-flop circuit 1.
Any expression may be used as long as it expresses the time width T out set in the set state of No. 9.

That is, in the air flow measuring device configured as described above, engine intake air flows through the intake pipe 11, and this intake air comes into contact with the temperature sensing element 12 and the temperature 71111 constant wire 13. It is now possible to do so. The resistance value of the temperature measuring element 13 is set in accordance with this intake air temperature, and the heat generation of the temperature sensing cord 12 is controlled by supplying heating power. The heat dissipation effect of the thermal element 12 is set in accordance with the air flow, and the rate of temperature rise is inversely proportional to the intake air flow rate.

When a start pulse signal Tin as shown in FIG. 2A is generated from the engine control unit 20 in synchronization with the rotation of the engine in this state, the flip-flop circuit 19 is set by this signal and the 17 is turned on, and heating power is set to be supplied to the bridge circuit including the temperature-sensitive cable I2. That is, the temperature sensing element 12 is controlled to generate heat and its temperature is as shown in FIG.
As shown in B), it increases in inverse proportion to the intake air flow rate.

When the temperature of the temperature sensing element 12 rises until a specified temperature difference is set from the air temperature measured by the temperature measuring element 13, the output signal from the comparator 18 rises and the flip-flop circuit 19 is reset. ,
The transistor 17 is turned off and the heating power is controlled to be cut off.

That is, for the temperature sensing element 12, this temperature sensing element 12
Heating power is supplied until the temperature rises to a specified temperature state, and therefore, the heating power supply time width corresponds to the intake air flow rate that sets the heat radiation effect of the temperature sensitive cord 12. .

Therefore, the output signal from the flip-flop circuit 19 that controls the supply state of this heating power, that is, the output signal shown in FIG.
The pulse time width of the pulsed output signal that becomes high level in the set state shown in C) comes to express the measured air flow rate. Then, the output signal from the flip-flop circuit 19 representing the measured air flow rate is taken out as a measured output signal T out via the output circuit 22, and is input to the engine control unit 20.

Here, the output circuit 22 shapes the pulse-like output signal from the flip-flop circuit 19, or generates first and second pulse signals corresponding to the rise and fall of the pulse-like output signal, respectively. , this first
The measurement signal T out is then converted into a signal expressing the above-mentioned time width by the interval of the second pulse signal, and is supplied to the control unit 20.

In the control unit 20, the above /1llJ constant signal T ou
The intake air ff1G/N per engine revolution, which is set based on the relationship between the air flG and the engine rotational speed N expressed by the time width of t, is used to calculate and output the fuel injection amount for the engine. Become so.

Here, since the start pulse signal Tin is generated in synchronization with the rotation of the engine, the output characteristics of the air flow measuring device are as shown in FIG. 3 in response to the engine rotation speed. That is, the intake air ff1G/N per engine revolution is a quadratic function of the time width T Out expressed by the DI constant output signal of the intake air flow rate. G/N, which is the information necessary to determine the fuel injection amount, is determined by the following quadratic function approximation formula of T out using the engine rotation speed as a parameter.

G/N-Tf'lX (Tout-Tol't)
2 +Tf'3 Here, the above TfL Toft, T
f'3 is a constant uniquely determined by the rotation speed N, and is shown, for example, in FIG. 4. However, the information on the rotational speed N that determines these constants differs depending on the engine control system, and if the generation period of the start pulse signal varies, the output time width T out of the air flow rate measurement signal also varies. As a result, the G/N value also started to fluctuate,
It is not possible to perform accurate metering control of the injected fuel.

If a variation occurs in the period of the start pulse signal Tin, this will directly affect the measurement signal T out. That is, as shown in FIG. 2, when the start pulse signal is input, the temperature sensing element 12 is controlled to generate heat, and when the temperature reaches the set temperature state, the heat generation control is stopped, and the temperature sensing element 12 is cooled down. become controlled.

For this reason, for example, if the generation period of the start pulse signal in normal conditions is T, the generation of the next start pulse signal is delayed, and the next signal is generated at an interval of "T + ΔT" as shown in Figure 2 (A). If so, the temperature sensing element 12 is Δ
Cooling is further continued only during T, and heating control is executed from a temperature state lower than the steady state. Therefore, it takes a long time for the comparator 18 to generate heat to a temperature state at which an output is generated, and as a result, the time width of the output signal becomes large as shown by Toutl.

Conversely, the generation time interval of the start pulse signal is "T-Δ
If the length is shortened as shown in "T", heating starts before the temperature-sensitive cord 12 is sufficiently cooled, and it takes a long time for the temperature of the temperature-sensitive cord 12 to reach the set temperature. The required time span becomes smaller. At this time, the output signal time width becomes small as shown by Tout2. Therefore, if the fuel injection amount is calculated and controlled using measurement signals such as T outl and T out2, it is not possible to adjust the amount of fuel appropriately for the operating state of the engine.

However, looking at the state of such a measurement signal, the time width of the measurement signal T Out is set corresponding to the generation cycle of the previous start pulse signal, and therefore it is different from the generation cycle of this start pulse signal. Output signal T Out
The relationship is directly established. That is,
In the case of FIG. 2, the air amount information G/N may be obtained by associating "T+ΔT" with ToutL.

FIG. 5 shows the flow of operations generated in response to the start pulse signal Tin in the engine control unit 20. ``An interrupt is generated in response to the generation of the start pulse signal Tin, and in step 101, an interrupt is generated at that time. The times Tl and tl (see Figure 2) are read and stored in the RAM respectively.Next, in step 102, the generation time T2 of the start pulse signal generated before this start pulse signal is read from the RAM. The time interval TL is calculated by reading out and calculating rTl - T2J.This TL at this time corresponds to the cooling time width of the thermosensor 12.Then, in step +03, it is stored in the RAM. The time TI thus generated is stored again as T2 for the next generated start pulse signal.

FIG. 6 shows an interrupt routine corresponding to the air flow m 1TII+constant signal, and this routine is generated in response to the fall of the measurement signal T out. Then, in step 201, the falling time t2 of this signal T out
and performs the calculation rt2-tLJ with the previously stored t2 in step 202 to determine the airflow fn
? l1lJ constant time width information T out is calculated.

Next, in step 203, the engine rotation speed N is calculated based on the calculated time interval TL between the current start pulse signal and the previous start pulse signal. Here, it is assumed that the start pulse signal is generated every 180'' CA of the engine, and when the unit of TL is (mS), the rotation speed N is calculated as N-(60X1000)/(2XTL).

Then, in the next step 204, based on the rotation speed N, a constant T['l
, Tol't STf'3 are calculated, and G/N is calculated in step 205.

Once the air amount G/N per engine rotation has been calculated in this way, in the next step 20G, this G/N is multiplied by a constant K, and the basic fuel injection: qTP is calculated.
This is what we seek.

In the above explanation, the rotation speed N is determined from the start pulse interval TL, and a constant is determined from a one-dimensional map based on this N. Of course, this also applies to the above constant T l'l as a one-dimensional map of TL. .

Tol't and TI'3 may also be determined.

Furthermore, it is also possible to calculate the air ff1G/N per engine revolution by direct calculation from the start pulse signal interval TL and the air flow rate measurement time width information T out.

[Effects of the Invention] As described above, in the control device for an internal combustion engine according to the present invention, the lp1 constant operation of the intake air flow rate is executed in synchronization with the rotation of the engine, and this measurement signal is based on the intake air flow rate. It comes to be expressed as a time width signal corresponding to . Then, based on this measurement signal of the intake air flow rate, the air amount G/N per engine rotation is determined, and the basic fuel injection amount is calculated based on this G/N, and the time used at this time is The interval TL is determined from the start pulse signal synchronized with the engine rotation corresponding to the measurement and the previous start pulse signal. Therefore, even if the ill constant signal varies due to variations in the start pulse interval, this a
Since there is a predetermined correspondence between the time width of the pJ constant signal and the time interval TL, use the time width of this measurement signal and the time interval TL to find the air ff1G/N per engine revolution. As a result, the influence of the variation in the generation interval of the start pulse signal can be eliminated, a stable air flow rate of ff1G/N per engine revolution can be obtained, and stable and reliable internal combustion engine control can be performed. Become so.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram illustrating the intake air flow rate measurement part of a control device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 shows the air flow ffi 11111 in a constant operating state.
Figure 3 is a diagram explaining the characteristics of the output pulse width of the above-mentioned measuring device, and Figure 4 shows the state of a constant one-dimensional matsub to obtain air ff1G/N per engine revolution. 5 and 6 are flowcharts respectively illustrating a means for calculating air flG/N based on a measurement signal obtained based on the above-mentioned air flow ffi 71$1 constant means. DESCRIPTION OF SYMBOLS 11... Intake pipe, 12... Temperature sensing element, 13... Temperature measuring element, 17... Transistor, 18... Comparator, 19... Flip-flop circuit, 20...
・Engine control unit. Applicant's representative Patent attorney Takehiko Suzue Figure 3 Engine rotation speed (rpm) Figure 4 Figure 6

Claims (1)

[Scope of Claims] A temperature sensing element is provided which is set to be exposed to the air flow flowing through the intake pipe of an internal combustion engine, and whose resistance value is set in accordance with the temperature, and the temperature sensing element is provided with a temperature sensing element that is synchronous with the rotation of the engine. is expressed by a time width Tout corresponding to the heating power supply time width necessary for supplying heating power that rises in response to a start pulse signal generated in a state where the temperature of the temperature sensing element rises to a specified temperature state. an air flow rate measuring device that generates a measured air amount signal G; and a start pulse signal corresponding to the engine rotational speed N at that time and a start pulse signal generated before the start pulse signal corresponding to each of the above start pulse signals. time interval T_
Based on the means for calculating L, the time interval T_L and the output time width Tout obtained by the air flow rate measuring device,
A means for calculating an air flow signal G/N corresponding to one revolution of the engine, and a means for calculating a basic fuel injection amount for the engine based on the air flow signal obtained by this means, A control device for an internal combustion engine, characterized in that a fuel injection amount for the engine is determined based on a calculated basic fuel injection amount.