JP5372664B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control device including an air flow rate measuring device, and more particularly to an air flow rate detection technique for measuring an accurate air flow rate.

  2. Description of the Related Art Conventionally, in an internal combustion engine control device, in order to detect the intake air flow rate of the internal combustion engine, an air flow rate detection device is disposed in the intake pipe of the internal combustion engine, and fuel injection is performed using the intake air flow rate detected by the air flow rate detection device. The amount is controlled.

  In recent years, reducing the exhaust emission of an internal combustion engine has become an important issue, and it has become common to convert the output of each sensor into a digital value and control the fuel injection amount with a digital arithmetic device. Yes. Therefore, increasing the accuracy of the intake air flow rate calculated by the digital arithmetic device using the output signal of the air flow rate detection device is an important technique for reducing the exhaust of the internal combustion engine.

  As an output signal of the air flow rate detection device, a voltage signal that changes a voltage value according to the flow rate, or a frequency signal that changes the cycle of the output pulse according to the flow rate disclosed in Patent Document 1 or Patent Document 2 is used. There are many.

  As a method for measuring the intake air volume with high accuracy at both high and low flow rates, measure the time width of multiple detected pulse trains, calculate the average period of one pulse, and based on the above average period A method for calculating the intake air amount is known (Patent Document 3).

  In addition, when the method described in Patent Document 3 is used, the fuel injection amount calculation cycle is usually performed at a frequency (slow cycle) lower than the output frequency of the air flow rate detection device. An average flow rate can be calculated and used for fuel injection amount calculation.

  If the average flow rate during the fuel injection amount calculation cycle is accurately calculated as described above, the flow rate during the fuel injection amount calculation cycle even when there is a large flow rate change in a short time such as during intake pulsation. Changes can be detected, and accurate intake air metering is possible.

Japanese Patent No. 3808038 JP-A-3-269218 JP-A-2-129522

  As the calculated value of the intake air amount used for the fuel injection control of the internal combustion engine, it is desirable to detect the total flow rate of the air that has passed through the air flow rate detector installation unit within a predetermined time.

  When the time width of a plurality of pulse trains is measured and the average period of one pulse is calculated as in Patent Document 3, the ratio of the time occupied by one pulse to the total time of the pulse train for calculating the average period is the pulse train. It depends on the length of the cycle.

  Therefore, although an average period is calculated with respect to the number of pulse trains, it does not become an average period with respect to the time when pulses are measured.

  The above-mentioned error becomes particularly large when the change in the intake air flow rate is large and the pulse train period changes greatly in a short time.

  Therefore, there is a problem that the intake air amount calculated based on the average period according to the above-described conventional method causes an error with respect to the total flow rate of the air that has passed through the air flow rate detector installation unit within a predetermined time.

  First, calculate the mass of air that has passed through the air flow rate detection device at the output time of each pulse from the period of multiple pulse trains, divide the sum of the air mass by the time when multiple pulses were measured, and measure multiple pulse trains The above-mentioned problem is solved by calculating the average flow rate during the measured time.

  Further, when calculating the average period from the time widths of a plurality of detected pulse trains, the average period with respect to time is calculated instead of the average period with respect to the number, and the average period is converted into a flow rate to calculate the average flow rate. This solves the above problem.

  In addition, the mass of air that has passed through the air flow rate detection device is first calculated from the period of a plurality of pulse trains in the output time of each pulse, and the above-described problem is solved by using the mass of air for the calculation of the fuel injection amount. .

  According to the present invention, in an internal combustion engine control device that employs an air flow rate detection device that outputs a frequency signal, a plurality of air flow rate detection device outputs during a predetermined time regardless of the change rate of the intake air flow rate. It is possible to accurately calculate the average air flow rate during a predetermined time from the output pulse.

  Further, by using the average air flow rate during a predetermined time for the fuel injection calculation, it is possible to perform the fuel injection calculation with high accuracy.

  Furthermore, according to the present invention, in the control device for an internal combustion engine that employs an air flow rate detection device that outputs a frequency signal, while the output signal pulse of the air flow rate detection device is detected, the pulse is output. Since the mass of air passing through the installation portion of the air flow rate detection device can be detected with high accuracy, the fuel injection calculation with high accuracy can be performed by using the mass of air for the fuel injection calculation.

System diagram of the entire engine. Control unit explanatory drawing. Airflow sensor internal structure schematic diagram. Airflow sensor output signal time history waveform. The relationship diagram of an air flow sensor output frequency and a detected flow rate. The relationship diagram of an air flow sensor output period and a detected flow rate. Explanatory drawing of the cause of flow rate measurement error occurrence during intake pulsation. The outline block diagram of fuel injection amount calculation. The general | schematic block diagram of the conventional period and flow volume conversion calculation. Time chart of air flow rate and cycle / flow rate conversion calculation. 1 is a schematic block diagram 1 of a cycle / flow rate conversion calculation according to the present invention. The relationship diagram of an air flow sensor output frequency and the air flow rate per pulse. FIG. 2 is a schematic block diagram 2 of a cycle / flow rate conversion calculation according to the present invention. FIG. 3 is a schematic block diagram 3 of a cycle / flow rate conversion calculation according to the present invention.

  First, an outline of the operation of the internal combustion engine, which is a premise in the implementation of the present invention, will be described.

  FIG. 1 shows a so-called MPI (multi-cylinder fuel injection) type four-cylinder internal combustion engine. Hereinafter, an MPI type four-cylinder internal combustion engine will be described as an example of the present invention. However, the embodiment of the present invention is not necessarily limited to the MPI type four-cylinder internal combustion engine. It includes all internal combustion engines equipped with an air flow meter using

  The intake air flow rate of the internal combustion engine is measured by an air flow sensor 2 provided at the outlet of the air cleaner 1. The intake air passes through the intake pipe 3 connected to the air cleaner 1, the throttle body 5 having the throttle valve 4 for adjusting the intake air flow rate, and enters the collector 6. Thereafter, the air is distributed to the intake branch pipe 7 that forms a part of the intake pipe 3, passes through the intake valve 8, and is sucked into the cylinder 9.

  Further, the fuel is sucked and pressurized from the fuel tank 10 by the fuel pump 11, adjusted to a constant pressure by the pressure regulator 12, and injected from the injector 13 provided in the intake pipe 3 into the intake branch pipe 7. The

  In the cylinder 9, the spark plug 14 ignites a gas in which air and fuel are mixed in the intake branch pipe 7 to burn the fuel. The exhaust gas after burning in the cylinder 9 of each cylinder passes through the exhaust pipe 16, is purified by the catalyst 17, and is then discharged outside the internal combustion engine.

  As shown in FIG. 2, the control unit 18 includes a power supply IC 40, a RESET signal 41, and an LSI 42, and a RESET signal 41 controlled by the power supply IC 40 is connected to a RESET terminal of the LSI 42. .

  In the control unit 18, an output value of each sensor installed in the internal combustion engine and an output value of a sensor for detecting operation information of the driver of the vehicle in which the internal combustion engine is installed are converted into an A / D converter built in the LSI 42. Alternatively, each actuator is controlled by converting it into a digital value by a timer that detects the period of the periodic signal and performing an operation, and outputting the operation result as a control signal.

As signals to be input to the control unit 18, a thermal air flow sensor 2, a crank angle sensor 19, an air-fuel ratio sensor 20 (O ₂ sensor), an opening sensor of the throttle valve 4, an ignition switch 21, and a starter switch 22 are used. Power from the battery 23, a signal from the accelerator opening sensor 45, and the like.

  A control signal output from the control unit 18 is output to the power transistor 24 that is an ignition switch of the injector 13, the fuel pump 11, and the spark plug 14.

  Next, the operation principle of the airflow sensor 2 will be described.

  As shown in FIG. 3, the thermal air flow sensor includes a heating resistor 60, a fixed resistor 61, a buffer circuit 62, and a voltage frequency conversion circuit 60 that are arranged in an air flow to be measured.

  The bridge circuit is configured so that the current flowing through the heating resistor 60 increases when the amount of intake air is large, and conversely, when the amount of intake air is small, the current flowing through the heating resistor 60 decreases.

  The air flow rate voltage signal Vi is extracted from the heating resistance current flowing through the heating resistor 60. The air flow rate voltage signal Vi is supplied to the voltage frequency conversion circuit 62 via the buffer circuit 61.

  The voltage frequency conversion circuit 62 includes an integrating capacitor inside. The integration capacitor is connected to the air flow rate voltage signal Vi via an internal switch. When the potential of the integration capacitor becomes larger than the upper limit threshold, the switch is turned off, and when the potential of the integration capacitor becomes lower than the lower limit threshold, the integration capacitor is turned off. By repeating the operation of turning on the switch, a periodic signal whose period changes according to the air flow rate voltage signal Vi is generated and used as the sensor output.

  Due to the above action, as shown in FIG. 4, the air flow sensor 2 outputs a frequency signal 70 in which the period 71 of the output signal voltage changes according to the intake air flow rate.

  FIG. 5 shows the relationship between the intake air flow rate detected by the airflow sensor 2 and the frequency of the output signal of the airflow sensor 2. When the intake air flow rate is small, the frequency of the output signal is low, and when the intake air flow rate is large, the frequency of the output signal is high. The two are in a non-linear relationship.

  Since the frequency and the cycle have an inverse relationship, the relationship between the intake air flow rate detected by the airflow sensor 2 and the cycle of the signal output from the airflow sensor 2 is as shown in FIG. It becomes the opposite characteristic.

  Further, as described above, since the intake air flow rate and the frequency of the signal output from the air flow sensor 2 are in a non-linear relationship, there are the following problems.

  In the steady state where the flow rate of air sucked into the cylinder is a constant value, in the above-described internal combustion engine, the vibration of the air pressure generated in the cycle of the vertical movement of the piston 35 shown in FIG. Inspiratory pulsation may occur due to the resonance of vibration caused by. When the intake pulsation occurs, the air flow rate detected by the air flow sensor becomes a periodic vibration waveform. At this time, as shown in FIG. 7, after taking the periodic average value of a plurality of pulses due to the non-linear relationship between the output frequency of the air flow rate detection device and the air flow rate, the periodic average is converted into the actual air flow rate. An error occurs with respect to the average value of.

  Therefore, in order to calculate the intake air amount with high accuracy, it is desirable to average the value obtained by converting the cycle into the flow rate, not the average of the cycle.

  Next, an example of the fuel injection amount calculation 58 using the frequency signal 70 that is the output of the airflow sensor 2 inside the LSI 42 will be described with reference to FIG.

  The output frequency signal 70 of the airflow sensor 2 is input to the LSI 42 inside the control unit 18. The timer 110 built in the LSI 42 detects the period of the frequency signal 70 and converts it into a digital value Cyc115.

  Thereafter, in the period / flow rate calculation 51, a flow rate Q52 corresponding to the passage flow rate of the air flow unit is calculated. Further, the phase delay calculation 56 corrects the phase of the flow rate of the air flow sensor installed portion and the flow rate of air sucked into the cylinder, which are generated by the pressure change in the collector 6, and calculates Qc57.

  In the fuel injection pulse width calculation 54, the fuel injection pulse width TP55, which is the time during which fuel is injected by the injector 13 of each cylinder, is obtained by dividing the Qc57 by the engine speed NE53 separately calculated from the signal of the crank angle sensor 19. Calculate.

  Next, a flow rate calculation method in the period / flow rate calculation 51 according to a conventional method will be described with reference to FIGS.

  FIG. 9 is a block diagram showing a calculation method of the period / flow rate calculation 51.

  The timer 110 mounted on the LSI 42 detects the cycle Cyc 115 of the output signal 70 of the air flow sensor.

  The Cyc 115 detected during the predetermined time A is stored by the buffer 112.

  The predetermined time A is a calculation cycle of the fuel injection amount calculation 58.

  In addition, during the predetermined time A, n114 indicating the number of detected pulses is updated every time a pulse is detected. Therefore, at the end timing of the predetermined time A, n114 represents the number of pulses detected during the predetermined time A.

  In the frequency average calculation 120, the average frequency AveCyc 122 is calculated by taking the sum of Cyc 115 during the predetermined time A stored in the buffer 112 at the timing when the predetermined time A ends, and further dividing by n114. Thereafter, the AveCyc 122 is converted into the average flow rate AveQ117 in the flow rate conversion calculation 121.

  FIG. 10 is a time chart showing signals until the air flow rate detected by the air flow sensor is detected by the cycle / flow rate calculation 51 of the control unit 18.

  When the air flow rate shown in the upper part of the drawing changes, the air flow sensor 2 detects the flow rate, and outputs a frequency signal 70 (in the drawing) whose cycle changes according to the detected flow rate.

  The control unit 18 calculates the average flow rate Ave117 after calculating the average cycle AveCyc122 in the time between t1 105 and t2 106, which is the predetermined time A, by the cycle / flow rate calculation 51 shown in FIG.

  As described above, the air flow sensor 2 integrates the air flow rate voltage signal Vi detected using the heating resistor 60 with the integrating capacitor inside the voltage frequency conversion circuit 62 and outputs the frequency signal 70.

  Therefore, the average flow rate during the time when the short pulse a100 shown in the middle part of FIG. 10 is output is high, and the average flow rate during the time when the long pulse b101 is output is low.

  Therefore, in order to calculate the average frequency corresponding to the average flow rate during the predetermined time A, the period of the pulse a100 at a ratio of the time of ta102 to the predetermined time A, and the period of the pulse b101 at the ratio of the time tb103 to the predetermined time A. It is necessary to calculate the average frequency taking the period into account.

  However, in the above-described conventional method, since the average frequency is not calculated by taking into account the proportion of time during which pulses are output, such as ta102 and tb103, when tb103 is very large with respect to ta102, the original pulse b101 The place where the contribution ratio should be increased is the same contribution ratio. That is, since the contribution rate of the pulse b101 indicating that the cycle is long and the flow rate is low is reduced, if the average flow rate is calculated from the average cycle obtained by the conventional method, a higher flow rate than the actual one is calculated, which is a problem.

  One embodiment of the present invention for solving the problems of the conventional method is shown in FIG.

  In the present embodiment, unlike the conventional method described with reference to FIG. 9, n114 indicating the number of detected pulses for a predetermined time A is not calculated, but instead of the plurality of pulses detected within the predetermined time A, first, The end time of the last pulse after detecting the pulse is detected as Δt133.

  As a pulse to be detected within the predetermined time A, a pulse that crosses the start or end timing of the predetermined time A may be detected.

  The period 115 detected by the timer 110 is converted into an air mass Qp132 per pulse by the flow rate conversion calculation 130 every time the period is detected.

  The buffer 112 stores all the air mass Qp132 calculated per predetermined time A per pulse.

  Thereafter, at the timing when the predetermined time A ends, the sum of all Qp132 stored in the buffer 112 in the flow rate average calculation 131 is divided by Δt133 to calculate the average flow rate AveQ117.

The conversion from the period (frequency) according to the flow rate conversion 130 to the air mass per pulse is generally the mass of air obtained by multiplying the air mass per unit time for each period (frequency) by the period. . Figure 12 on, usually shows a period (frequency) and the air mass per unit time relationship employed. On the other hand, the period (frequency) and the air mass per pulse have a relationship in which the flow rate at the low frequency is relatively large with respect to the high frequency, as shown in the lower part of FIG.

  Another embodiment of the present invention is shown in FIG.

  In the present embodiment, unlike the conventional method described with reference to FIG. 8, n114 indicating the number of detected pulses for a predetermined time A is not calculated. Instead, the first of a plurality of pulses detected within the predetermined time A is first calculated. The end time of the last pulse after detecting the pulse is detected as Δt133. As a pulse to be detected within the predetermined time A, a pulse that crosses the start or end timing of the predetermined time A may be detected.

  The period 115 detected by the timer 110 is converted into an air mass Q116 per unit time by the flow rate conversion calculation 111 every time the period is detected.

  Thereafter, in the correction calculation 140, every time the period is detected, Qcorr 142 is calculated by multiplying Q116 by the detection period Cyc115.

  The buffer 112 stores all Qcorr 142 calculated during the predetermined time A. Thereafter, at the timing when the predetermined time A ends, in the flow rate average operation 141, the sum of all Qcorr 142 stored in the buffer 112 is divided by Δt133 to calculate the average flow rate AveQ117.

  Another embodiment of the present invention is shown in FIG.

  In this embodiment, unlike the conventional method described with reference to FIG. 8, n114 representing the number of detected pulses for a predetermined time A is not calculated.

  As in the conventional method, the Cyc 115 detected during the predetermined time A is stored in the buffer 112.

  In the frequency average calculation 150, the average frequency AveCyc 122 is calculated by taking the sum of the squares of the Cyc 115 stored in the buffer 112 and dividing by the sum of the Cyc 115 at the timing when the predetermined time A ends.

  Thereafter, the AveCyc 122 is converted into the average flow rate AveQ117 in the flow rate conversion calculation 121.

  As described above, the problem can be solved by improving the frequency average calculation 150 with respect to the conventional method.

  In an engine employing a thermal airflow sensor that outputs a frequency as an output signal, the present invention is very effective and is likely to be used.

1 Air Cleaner 2 Air Flow Sensor 3 Intake Pipe 4 Throttle Valve (Throttle)
5 throttle body 6 collector 7 intake branch pipe 8 intake valve 9 cylinder 10 fuel tank 11 fuel pump 12 pressure regulator 14 spark plug 16 exhaust pipe 17 catalyst 18 control unit 19 crank angle sensor 20 air-fuel ratio sensor 21 ignition switch 22 starter switch 23 battery 40 Power IC
70 Airflow sensor output frequency signal

Claims (4)

Connected to an air flow measuring device that measures the intake air amount of the internal combustion engine and outputs a periodic signal whose cycle changes according to the measured air amount,
A period measuring function for detecting a period or a frequency of a signal output from the air flow measuring device;
An air flow rate detection function for calculating the air flow rate from the period or frequency of the detected signal;
In an internal combustion engine control device having an average flow rate calculation function for calculating an average flow rate during a predetermined time based on an air flow rate calculated by an air flow rate detection function,
The air flow rate detection function obtains the relationship between the measured flow rate and the output period or output frequency in the air flow rate measuring device in advance,
Based on the relationship and the time of one cycle of the signal output from the air flow measuring device, one cycle of the signal output by the air flow measuring device from the cycle or frequency of the signal detected by the cycle measuring function. Convert to air mass,
The average flow rate calculation function includes a plurality of one-cycle air masses converted by the air flow rate detection function within a predetermined time, and a plurality of cycles detected by the cycle measurement function within the predetermined time. Alternatively, an internal combustion engine control device that calculates an average flow rate during the predetermined time from an elapsed time corresponding to a frequency signal. Connected to an air flow measuring device that measures the intake air amount of the internal combustion engine and outputs a periodic signal whose cycle changes according to the measured air amount,
A period measuring function for detecting a period or a frequency of a signal output from the air flow measuring device;
An air flow rate detection function for calculating the air flow rate from the detected signal cycle or frequency;
In an internal combustion engine control device having an average flow rate calculation function for calculating an average flow rate during a predetermined time based on an air flow rate calculated by an air flow rate detection function,
The air flow rate detection function obtains the relationship between the measured flow rate and the output period or output frequency in the air flow rate measuring device in advance,
Based on the relationship and the time of one cycle of the signal output from the air flow measuring device, one cycle of the signal output by the air flow measuring device from the cycle or frequency of the signal detected by the cycle measuring function. Convert to air mass,
The average flow rate calculation feature of the internal combustion engine and performs correction in accordance with the air flow to the air flow rate per calculated unit time by measuring function, the period or frequency measured in the previous SL period measurement function Control device. Connected to an air flow measuring device that measures the intake air amount of the internal combustion engine and outputs a periodic signal whose cycle changes according to the measured air amount,
A period measuring function for detecting a period or a frequency of a signal output from the air flow measuring device;
An air flow rate detection function for calculating the air flow rate from the period or frequency of the detected signal;
In an internal combustion engine control device having an average flow rate calculation function for calculating an average flow rate during a predetermined time based on an air flow rate calculated by an air flow rate detection function,
The air flow rate detection function obtains the relationship between the measured flow rate and the output period or output frequency in the air flow rate measuring device in advance,
Based on the relationship and the time of one cycle of the signal output from the air flow measuring device, one cycle of the signal output by the air flow measuring device from the cycle or frequency of the signal detected by the cycle measuring function. Convert to air mass,
The average flow rate calculation function corrects the period or frequency detected by the period measurement function at a predetermined time according to the period or frequency, and uses the corrected frequency within the predetermined time. A control apparatus for an internal combustion engine, which calculates an average frequency. Connected to an air flow measuring device that measures the intake air amount of the internal combustion engine and outputs a periodic signal whose cycle changes according to the measured air amount,
A period measurement function for reading a period at a timing when a periodic change in the output signal of the air flow measurement device occurs;
In an internal combustion engine control device comprising an average air flow rate detection function for calculating an air flow rate from an average period (frequency) calculated by an average frequency calculation function,
The average frequency calculation function performs correction according to the period or frequency for the period or frequency detected by the period measurement function at a predetermined time,
A control apparatus for an internal combustion engine, wherein an average period or frequency within the predetermined time is calculated using the period or frequency subjected to the above correction.

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