JP2006250109A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, capable of quickly catching pulsation that is varied depending on the state of the internal combustion engine, and correctly obtaining accumulation distribution of output values of an air flow sensor in pulsation to provide precise intake air flow. <P>SOLUTION: This control device for an internal combustion engine is provided with an intake air flow operation means 70 for operating intake air flow based on the output value of an intake air flow detection device 20. The intake air flow operation means 70 is provided with a sampling means 61 to sample the output value at prescribed timing, an accumulation distribution operation means 72 to operate frequency for each value of sampled output values by the sampling means 61, and operate an accumulation distribution state of frequency for each value, and an intake air flow correction means 63 to correct the sampled output values based on an operated accumulation distribution state. The accumulation distribution operation means 72 renews the accumulation distribution state by inputting sampled output value every time the output value is sampled by the sampling means 61. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine provided with an air flow rate detection device, and more particularly to a control device for an internal combustion engine that can obtain an accurate air flow rate even when pulsation occurs in measured air.

  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 (air flow sensor) is arranged in the intake pipe of the internal combustion engine, and the air detected by this air flow rate detection device. The amount of fuel injected into the internal combustion engine is controlled based on the flow rate.

  In recent years, it has become an important issue to improve the exhaust performance of an internal combustion engine by performing optimal combustion. In order to solve such a problem, the output of each sensor is converted into a digital value. However, this fuel injection amount is generally controlled by a digital arithmetic unit.

  By the way, in an internal combustion engine, a resonance phenomenon called pulsation occurs due to resonance between the air pressure vibration generated by the vertical movement of the piston constituting the internal combustion engine and the vibration due to the natural frequency of the intake pipe. When the opening of the throttle valve installed in the pipe is increased, the amplitude of this pulsation increases. Usually, air flowing from the intake pipe into the cylinder may flow in the reverse direction, and this phenomenon is called backflow. . When a device that detects only one-way flow is used as the device that detects the intake air flow rate, even if a reverse flow occurs, it is detected that the air flow is in the direction from the intake pipe into the cylinder. As a result, there is a problem that an accurate air flow rate cannot be detected.

  In view of this, a flow rate detection device that takes into account the influence of such a reverse flow of intake air has been proposed. This device includes a means for inputting the output of a thermal air flow meter (air flow detection device) to correct response delay, a means for linearizing conversion of the output of the correction means to a value corresponding to the air flow, and this conversion Backflow discriminating means for discriminating the backflow based on the air flow rate (see Patent Document 1). However, in such an air flow rate detection device, the response delay due to the heat capacity of the device and the non-linear correspondence between the air flow rate and the output value of the air flow rate detection device have a nonlinear relationship. It is known that a large error occurs between the average flow rate of the air sucked into the air and the average value of the air flow rate calculated by the digital calculation device.

  In order to solve such a problem, for example, the presence or absence of backflow is determined based on the electrical signal of the flow rate detection means (air flow rate detection device). There has been proposed an intake air amount measurement device that obtains (cumulative) distribution based on an electric signal from a signal waveform and kurtosis in the cumulative distribution and obtains a flow rate during reverse flow based on the kurtosis (see Patent Document 2).

  In addition to this, considering the response delay of the hot-wire air flow meter (air flow detection device) and non-linear output, the feature value is extracted based on the output waveform, and the feature value of this extracted waveform is There has been proposed an intake air flow rate measuring device that uses a reverse flow ratio to obtain an average value of the air flow rate from the reverse flow ratio (see Patent Document 3).

JP-A-9-166464 Japanese Patent Laid-Open No. 2002-221072 JP 2000-265898 A

  By the way, in a device that measures the intake air flow rate, generally, when correcting the output of the air flow meter (air flow rate detection device) using the statistical information as described above, sampling was performed in the past. There are many devices that store the output value (sampling data) of the air flow rate detection device and calculate the cumulative distribution using the stored sampling data. In such a device, in order to increase the calculation accuracy There was a need to save more sampling data. In order to acquire the cumulative distribution with high accuracy and accurately correct the air flow rate during pulsation, it has been necessary to quickly perform arithmetic processing based on a large amount of stored sampling data.

  In addition, since the pulsation cycle of the air sucked into the internal combustion engine changes according to the change in the crank angle (engine speed), the sampling data for accurately capturing the air pulsation is detected by the crank angle sensor. It is desirable to perform this when the crank angle has reached a predetermined crank angle. However, in such sampling, when the engine speed is large, the sampling interval and the interval for calculating the cumulative distribution are shortened. As a result, the sampling data increases, and the calculation processing is performed based on the increased data. As a result, the apparatus load increases, and processing delay may occur.

  Furthermore, in order to obtain a cumulative distribution that quickly captures pulsations that change according to the state of the internal combustion engine, information based on old sampling data must be cleared from the cumulative distribution. For this purpose, not only the value of the sampled data but also the information of the order of sampling must be stored.

  The present invention has been made in view of such problems, and the object of the present invention is to provide pulsation that varies depending on the state of the internal combustion engine even when the capacity for storing sampling data is small. It is intended to propose a control device for an internal combustion engine that can obtain an accurate intake air flow rate by quickly capturing the air flow and obtaining an accurate cumulative distribution of the output value of the air flow sensor during pulsation.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention is a control device for an internal combustion engine provided with intake air flow rate calculation means for calculating an intake air flow rate based on an output value of the intake air flow rate detection device. The intake air flow rate calculating means calculates the frequency for each value of the sampled output value, sampling means for sampling the output value at a predetermined timing, and cumulative distribution of the frequency for each value A cumulative distribution calculating means for calculating a state; and an intake air flow rate correcting means for correcting an intake air flow rate corresponding to the sampled output value based on the cumulative distribution state, wherein the cumulative distribution calculating means includes the sampling means. Each time the output value is sampled, the cumulative distribution state is updated by inputting the sampled output value.

  The control apparatus for an internal combustion engine of the present invention configured as described above is such that the cumulative distribution calculation means inputs the sampled output value every time the sampling means samples the output value, and the frequency of the output value is calculated. Since the cumulative distribution state is updated, it is not necessary to store the sampled output values and the order in which the output values are output. And since the capacity | capacitance which preserve | saves data decreases, the speed of the arithmetic processing of CPU can be improved.

  As a preferred specific aspect of the control apparatus for an internal combustion engine according to the present invention, the cumulative distribution calculation means adds the sampled output value to the frequency data value every time the output value is sampled. Frequency data value addition processing means for performing processing, and frequency data value reduction processing means for performing processing for reducing the value of the frequency data at every predetermined timing, the frequency data value addition processing means and the frequency The cumulative distribution state is updated based on the value of the frequency data obtained by the data reduction processing means.

  The control device for an internal combustion engine of the present invention configured as described above performs an addition process to the frequency data value every time the output value is sampled, while performing a process to decrease the frequency data value. Since the data of the output value just detected by the air flow rate detection device can be reflected in the cumulative distribution state in real time, the change in intake air pulsation can be captured accurately and quickly, and the air flow affected by this pulsation Can be corrected accurately.

  As a preferred specific aspect of the control device for an internal combustion engine according to the present invention, the timing at which the frequency data value reduction processing means decreases the value of the frequency data is such that the crank angle of the internal combustion engine is a predetermined crank angle. It is the timing which becomes.

  The control apparatus for an internal combustion engine of the present invention configured as described above utilizes the fact that the crank angle is synchronized with the period of pulsation, and the intake air flow rate (sampled output value) accurately affected by this pulsation. Can be corrected.

  As a preferred specific aspect of the control device for an internal combustion engine according to the present invention, the timing at which the frequency data value reduction processing means decreases the value of the frequency data is determined by the intake air flow rate correction means by the intake air flow rate correction means. It is the timing to correct.

  Since the control device for an internal combustion engine of the present invention configured as described above reduces the value of the frequency data after correcting the intake air flow rate, each control value obtained based on many sampled output values is reduced. The intake air flow rate (sampled output value) can be accurately corrected by the cumulative distribution.

  As a preferred specific aspect of the control device for an internal combustion engine according to the present invention, the timing at which the frequency data value reduction processing means decreases the value of the frequency data is such that the value of the frequency data of the cumulative distribution is the predetermined data. It is characterized by the timing exceeding the value.

  The control device for an internal combustion engine of the present invention configured as described above can reflect the new output value just sampled in the cumulative distribution by setting the upper limit of the frequency data and reducing the value of the frequency data. Can capture changes in pulsation.

  As a preferred specific aspect of the control device for an internal combustion engine according to the present invention, the frequency data value reduction processing means reduces the value of the frequency data by dividing the value of the frequency data by a predetermined value. It is characterized by performing the process to be performed.

  The control device for an internal combustion engine of the present invention configured as described above can reflect a newly sampled output value in this cumulative distribution while reflecting the cumulative distribution so far by dividing by a predetermined division value. Therefore, even if pulsation occurs, it is possible to quickly grasp the fluctuation of the intake air flow, correct the amount, and obtain a highly accurate intake air flow rate.

  Further, as a preferred specific aspect of the control device for an internal combustion engine according to the present invention, the frequency data value reduction processing means calculates a division value for reducing the value of the frequency data based on the rotational speed of the internal combustion engine. It is characterized by performing the setting process.

  Further, as a preferred specific aspect of the control apparatus for an internal combustion engine according to the present invention, the frequency data value reduction processing means reduces the frequency data based on the opening degree of the throttle valve of the intake air flow rate. It is characterized in that processing for setting is performed.

  The control device for an internal combustion engine of the present invention configured as described above divides the value of the frequency data by the division value set based on the rotational speed of the internal combustion engine or the opening of the throttle valve depending on the change in pulsation. The cumulative distribution that captures the pulsation can be obtained quickly.

  Further, as a preferable specific aspect of the control device for an internal combustion engine according to the present invention, the sampling means may output the output value at a predetermined time interval when the rotational speed of the internal combustion engine is larger than a predetermined rotational speed. When the rotational speed is smaller than the predetermined rotational speed, the output value is sampled every time the crank angle of the internal combustion engine becomes a predetermined angle.

  In the control apparatus for an internal combustion engine of the present invention configured as described above, the pulsation increases when the rotation speed of the internal combustion engine is low. Therefore, by sampling according to the crank angle, an accurate cumulative distribution can be obtained. As a result, when the rotational speed of the internal combustion engine is high, the intake air is stable. For example, by performing sampling at a time interval larger than the time for one revolution of the crankshaft, The load can be reduced.

  In a preferred specific aspect of the control device for an internal combustion engine according to the present invention, the sampled output value used by the cumulative distribution calculating means for calculating the cumulative distribution state is an output converted into an intake air flow rate. It may be a value.

  The control apparatus for an internal combustion engine of the present invention does not store the sampling data of the output value of the sampled intake air flow rate detection device, but stores the information of the cumulative distribution calculated from the sampling data and samples the output value each time. Since the cumulative distribution state is calculated and the cumulative distribution state is updated, the cumulative distribution state of the output value of the air flow rate detecting means can be obtained with high accuracy even when the data storage capacity is small. As a result, the pulsation of the intake air can be quickly captured, the air flow rate can be calculated accurately, and optimal fuel injection control can be performed based on the air flow rate.

  Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of an MPI (multi-cylinder fuel injection) type four-cylinder internal combustion engine having an embodiment of the present invention. In the present embodiment, the MPI type four-cylinder internal combustion engine 1 will be described. However, the internal combustion engine 1 is not necessarily limited to the MPI type four-cylinder internal combustion engine, and includes an air flow sensor (intake air flow rate detection device). If so, it should be applied to all internal combustion engines.

  In FIG. 1, an internal combustion engine (engine) 1 is mainly connected to an intake pipe 3 on the intake side of each cylinder 15 of the internal combustion engine 1, and an air cleaner 2, a throttle body 5, and a collector 7 are arranged in that order from the upstream side. Has been placed. Further, the collector 7 and the cylinder 15 are connected by an intake branch pipe 16. Each intake branch pipe 16 is provided with an injector (fuel injection valve) 13 for supplying fuel to the cylinder 15, and further, an ignition plug 25 for igniting the supplied fuel is provided for the cylinder 15. Has been. An exhaust pipe 23 is connected to the exhaust side of the cylinder 15, and a catalyst 33 is disposed in the exhaust pipe 23.

  Further, signals from the air flow sensor 20, the crank angle sensor 14, the throttle sensor 8, the water temperature sensor 19, and the air-fuel ratio sensor 24 are input to the control unit (control device for the internal combustion engine) 10, and a starter switch 27 and an ignition switch are input. The electric power from the battery 30 is also input via 28. On the other hand, control signals are output from the control unit 10 to the injector 13, the fuel pump 11, the power transistor 26, and the ISC valve 6. The power transistor 26 is used as an ignition switch for the spark plug 25.

  Next, the function of each sensor and actuator will be described. The crank angle sensor 14 built in the distributor 17 that determines the ignition timing outputs a pulse at every predetermined crank angle, and the pulse is input to the control unit 10, and the CPU 43 inside the control unit 10 determines the crank angle. And the engine speed NRPM is calculated.

  The throttle sensor 8 is a sensor for detecting the valve opening degree of the throttle valve 4, and is attached to the throttle valve 4 so that an output signal of the sensor 8 can be input to the control unit 10. Then, the CPU 43 of the control unit 10 calculates the amount of change in the valve opening of the throttle valve 4 based on the sensor signal from the throttle sensor 8.

  The air-fuel ratio sensor 24 is attached to the exhaust pipe 23, detects the oxygen concentration in the exhaust gas, and outputs a signal corresponding to the oxygen concentration to the control unit 10. The output signal of this sensor is used as a signal for calculating the air-fuel ratio in the CPU 43. The CPU 43 treats the calculated air-fuel ratio as a feedback amount, and calculates the final fuel injection pulse width so that the internal combustion engine 1 becomes the target air-fuel ratio.

  Next, the operation of the internal combustion engine 1 will be described. The flow rate of the intake air sucked into the internal combustion engine 1 is measured by a thermal air flow sensor 20 that detects the intake air flow rate (air flow rate) provided at the outlet of the air cleaner 2. The intake air that has passed through the air flow sensor 20 is introduced into the collector 7 through the throttle body 5 in which the throttle valve 4 is disposed and the ISC valve 6 that is provided so as to bypass the throttle body 5. Thereafter, the intake air is distributed to each cylinder 15 via the intake branch pipe 16 and is sucked into the cylinder of each cylinder 15.

  On the other hand, the fuel is sucked and pressurized from the fuel tank 12 by the fuel pump 11, adjusted to a constant pressure by the pressure regulator 9, and then injected from the injector 13 into each intake branch pipe 16. In the intake branch pipe 16, fuel and air are mixed to form an air-fuel mixture, and the air-fuel mixture is introduced into the cylinder.

  In the cylinder, the air-fuel mixture is ignited by the spark plug 25 to burn the fuel. Exhaust gas after combustion in the cylinder of each cylinder 15 passes through the exhaust pipe 23, is purified by the catalyst 33, and is discharged out of the internal combustion engine 1.

  FIG. 2 is a block diagram of the control unit (control device) 10 according to the present embodiment and the sensors and actuators connected thereto. As shown in FIG. 2, the control unit 10 includes a power supply IC 41 and an LSI 40. The RESET terminal of the LSI 40 is connected to the power supply IC 41 so that a RESET signal controlled by the power supply IC 41 can be transmitted. Has been. An output signal of a sensor arranged in each device of the internal combustion engine 1 is output to a control unit (ECU) 10, and the control unit 10 calculates a control signal of each actuator based on the signal, and controls the calculated result. Each actuator is controlled by outputting it as a signal.

  FIG. 3 is an internal calculation block diagram of the CPU 43 provided in the control device 10 of the internal combustion engine 1 according to the present embodiment. FIG. 4 shows a case where the sucked air is a forward flow, and FIG. FIG. 6 is a diagram illustrating the state of a cumulative distribution used for calculating the forward flow and the reverse flow states shown in FIGS. 4 and 5 when the reverse flow occurs in FIG. .

  As shown in FIG. 3, the voltage signal output from the airflow sensor 20 is digitally converted by the A / D converter 42 in the LSI 40.

  The CPU 43 calculates an intake air flow rate calculation means 60 for calculating an intake air flow rate based on the converted output value of the air flow sensor 20 (hereinafter referred to as sensor output value), and an intake air flow rate calculated by the intake air flow rate calculation means 60. The fuel injection pulse width calculating means 80 for calculating the fuel injection pulse width TP to be injected by the injector 13 is provided.

  Further, the intake air flow rate calculation means 60 includes sampling means 61, flow rate conversion means 62, air flow rate correction means 63, and backflow correction amount calculation means 70. The sampling unit 61 samples the sensor output value shown above at a predetermined timing, and outputs the sampled sensor output value to the flow rate conversion unit 62. The flow rate conversion unit 62 converts the sampled sensor output value by the flow rate conversion unit 62 and outputs the sensor output value converted to the flow rate to the backflow correction amount calculation unit 70. In addition, as shown in FIG. 3, the sampled sensor output value may be directly output to a cumulative distribution calculating means 72 described later of the backflow correction amount calculating means 70.

  In the internal combustion engine 1 described above, pulsation may occur due to resonance between the vibration of the air pressure generated in the cycle of the vertical movement of the piston 18 and the vibration due to the natural frequency of the intake pipe 3. When a reverse flow of the air sucked by this pulsation occurs, when a sensor that can detect only the air flow rate in which the airflow sensor 20 flows in one direction is used, correction is necessary from the following viewpoint.

  Specifically, as shown in (1) of FIG. 4, when no backflow occurs (when the flow rate changes in the forward flow region), the CPU 43 calculates the airflow sensor 20 based on the output voltage. The air flow rate (calculated airflow sensor output value) has a waveform as shown in (2) of FIG. 4 due to a response delay of the airflow sensor.

  On the other hand, as shown in (1) of FIG. 5, when the backflow is generated, the airflow sensor 20 detects the backflow as a forward flow, so the air flow rate detected by the airflow sensor 20 (calculated airflow sensor output) (Value) virtually has a waveform as shown in (2) of FIG. Further, the air flow rate calculated by the CPU 43 based on the output voltage of the air flow sensor 20 has a broken line waveform (before correction) as shown in (3) of FIG.

  Thus, by determining the reverse flow as the forward flow, the detected average air flow rate becomes larger than the actual average air flow rate, and the average air flow rate by the sensor output value shown in (3) of FIG. A large error occurs between the actual average air flow rate shown in 5 (1). When the fuel injection pulse width calculating means 80 calculates the fuel injection amount based on the average value of the output of the air flow sensor 20 during the reverse flow, there is a large error compared to the actual air flow rate. Since the control cannot be performed, the air flow rate based on the sensor output value should be corrected so as to obtain a solid line waveform (after correction) as shown in FIG.

  From this point of view, the backflow correction amount calculation means 70 outputs the sensor output value or the flow rate conversion means 62 when the intake air sucked into the internal combustion engine 1 pulsates and a backflow occurs in the air. An amount to be corrected is calculated based on the converted sensor output value.

  Specifically, as shown in FIG. 3, the backflow correction amount calculating means 70 includes a backflow determining means 71, a cumulative distribution calculating means 72, a quantitative waveform feature calculating means 73, and a backflow ratio calculating means 74. Therefore, the backflow discrimination means 71 determines whether a backflow has occurred in the sucked air based on the output data from the flow rate conversion means 62 or the output data from the A / D converter 42. As this determination method, the determination is made using the backflow map from the average value of the data from the flow rate conversion means 62 and the variance of the data. When the backflow determination unit 71 determines that a backflow has occurred in the sucked air, the determination result is output to the cumulative distribution calculation unit 72.

  The cumulative distribution calculation means 72 calculates the frequency for each value of the sensor output value (output value) sampled and converted by the flow rate conversion means 62, or the frequency for each value of the sampled sensor output value, The cumulative distribution (state) of the frequency of each sensor output value as shown in FIG. 6 is obtained. Specifically, the frequency of how many times the sampled specific sensor output value has been output so far is calculated, and the cumulative distribution of the frequency for each calculated sensor output value is obtained. Then, as will be described later, when a certain sensor output value is output, the frequency of the sensor output value is calculated by performing a process of adding the frequency (number of times) of the sensor output value by 1 (number of times). The status of cumulative distribution has been updated.

  The frequency of each sensor output value (each value) calculated by the cumulative distribution calculation means 72 is maximum as shown in (1) of FIG. 6 in the case of a forward flow in which no reverse flow occurs. When a distribution with a shape close to symmetry having a peak at the minimum value and a minimum value (having a maximum value and a minimum value) is obtained and a backflow occurs, as shown in (2) of FIG. Compared to the case where it does not occur, an asymmetrical distribution is obtained.

  The quantitative waveform feature calculating unit 73 determines the state of the cumulative distribution of the frequency for each value from the difference in the shape of the cumulative distribution of the frequency for each value of the sensor output value obtained by the cumulative distribution calculating unit 72. This is regarded as a quantitative waveform, and the characteristics of this waveform are calculated and output to the backflow ratio calculating means 74. Further, the reverse flow ratio calculation means 74 calculates the reverse flow ratio, which is the ratio of the forward flow and the reverse flow, from the characteristic of the quantitative waveform of this frequency, and the amount to be corrected (the error in the average air flow rate when the reverse flow occurs) ) Is output to the air flow rate correction means 63.

  Based on the correction amount during reverse flow obtained in this way, the air flow rate correction means 63 corrects the intake air flow rate (sensor output value converted to the intake air flow rate) output by the flow rate conversion means 62, The corrected intake air flow rate is output to the fuel injection pulse width calculation means 80. As a result, the fuel injection pulse width calculation means 80 can obtain an accurate fuel injection pulse width TP, and the control device 10 controls the injector 13 based on the fuel injection pulse width TP, so that appropriate fuel injection is possible. You can control.

  FIG. 7 is a detailed calculation block diagram of the sampling means 61 and cumulative distribution calculation means 72 shown in FIG. FIG. 8 is a diagram for explaining the calculation processing of the cumulative distribution calculation means 72 shown in FIG. 7. FIG. 8A shows the relationship between the engine speed and the intake air flow rate (air flow rate), and FIG. FIG. 5 is a diagram showing the relationship between the valve opening of the throttle valve 4 and the air flow rate. FIG. 9 is a diagram for explaining the processing timing of the sampling means 61, the cumulative distribution calculating means 72, and the air flow rate correcting means 63 shown in FIG. FIG. 10 is a diagram for explaining a storage data amount to be stored in the control unit 10, (a) is a diagram for explaining a data storage amount according to the present embodiment, and (b) is a comparison. It is a figure for demonstrating the conventional data storage amount as an example.

  By the way, the timing at which the sampling means 61 described above samples the sensor output value of the airflow sensor 20 is an important factor for obtaining an accurate cumulative distribution. In the control of the internal combustion engine, the timing at which the output value of the sensor is sampled is generally a method of sampling every predetermined time and a method of sampling based on a crank angle that changes according to the driving state of the vehicle.

  The condition in which resonance occurs in the device of the internal combustion engine 1 and the amplitude of the pulsation increases is determined by the crank angle information that is the period of the vertical motion of the piston 18 and the natural frequency of the intake pipe 3, and this pulsation. Therefore, it is desirable to perform sampling every time the crank angle detected by the crank angle sensor 14 reaches a predetermined crank angle. However, when such sampling is performed, when the change speed of the crank angle is fast, that is, when the engine speed is large, the sampling interval and the interval for calculating the state of the cumulative distribution are shortened, and the calculation load is reduced. It will increase.

  Therefore, as shown in FIG. 7, the sampling means 61 includes a sampling timing switching processing means 61A and a sampling processing means 61B. The sampling timing switching processing means 61A is based on the engine speed of the internal combustion engine 1. The sampling processing means 61B switches the timing for sampling.

  Specifically, when the engine speed is larger than a predetermined speed (the speed set by the resonance amplitude), the sensor output value is sampled at a predetermined time interval, and the engine speed is set to the predetermined speed. If it is smaller, the sampling timing switching processing means so that the sensor output value is sampled every time the crank angle of the crankshaft of the internal combustion engine 1, which is the output value of the crank angle sensor 14, reaches a predetermined crank angle. 61A outputs a switching signal to the sampling processing means 61B. Based on the switching signal of the sampling means 61, the sampling processing means 61B performs the above-described sampling and outputs the sampled sensor output value to the flow rate conversion means 62 without storing it. Although not shown in FIG. 7, as described above, the sampled sensor output value may be output to the cumulative distribution calculation means 72 without using the flow rate conversion means 62.

  As described above, when the crank angle changing speed (engine speed of the internal combustion engine 1) is lower than the crank angle changing speed (engine speed of the internal combustion engine 1) when this resonance occurs and the pulsation amplitude increases. In this case, sampling is performed according to the output value of the crank angle sensor 14, and at other times, sampling is performed at predetermined time intervals, so that the calculation load of the CPU can be reduced and it depends on the pulsation amplitude. The detection error of the air flow rate can be accurately corrected.

  On the other hand, the cumulative distribution calculating means 72 needs to obtain an accurate cumulative distribution state that quickly corresponds to a change in pulsation due to the state of the internal combustion engine in order to correct the intake air flow rate that fluctuates due to the intake pulsation of the internal combustion engine. .

  Therefore, as shown in FIG. 7, the cumulative distribution calculation means 72 includes frequency data division value setting means 72A, frequency data value division processing means 72B, and frequency data value addition processing means 72C.

  The frequency data division value setting means 72A is a means for setting a division value for dividing the frequency data value of the cumulative distribution by a predetermined value. The division value is based on the engine speed and the opening of the throttle valve 4. Is set.

  Specifically, as shown in (a) and (b) of FIG. 8, a change in the engine speed (amount of change in the engine speed) calculated using the crank angle and a change in the opening of the throttle valve 4. When the (amount of change in opening speed) is large, the average air flow rate and the amplitude of pulsation change, so the cumulative distribution data also changes abruptly. On the other hand, if the change in the engine speed (change in engine speed) calculated using the crank angle or the change in the opening of the throttle valve 4 (change in the opening speed) is small, as much sampling as possible If the cumulative distribution is obtained based on the data, an accurate cumulative distribution can be obtained.

  Therefore, the frequency data division value setting means 72A uses the calculation formula or table based on the engine speed, the opening degree of the throttle valve 4, the intake valve opening / closing timing, etc., when a predetermined condition is satisfied, The value to divide is set.

  Thus, based on the change in the crank angle or the signal calculated using the crank angle (engine speed) and the change rate in the opening of the throttle valve 4, the amount of decrease in the value of the frequency data of the cumulative distribution (specifically In other words, by changing the division value), it is possible to quickly respond to a change in pulsation and obtain accurate cumulative distribution data.

  Then, using the division value set by the frequency data division value setting means 72A, as shown in FIG. 7, the frequency data value division processing means (frequency data value reduction processing means) 72B is used for all the airflow sensors in the cumulative distribution. The frequency data value in the output value area is divided, the value of each frequency data is decreased, and the state of the cumulative distribution is updated. Further, the frequency data value division processing unit 72B outputs the decreased frequency data value to the frequency data value addition processing unit 72C in order to perform processing for adding to the next frequency data value.

  Further, the frequency data value division processing unit 72B reduces the value of the frequency data of the cumulative distribution by dividing the value of the frequency data of the cumulative distribution by a predetermined division value. The cumulative distribution used for this pulsation correction Is preferably a cumulative distribution that quickly responds to pulsations that change depending on the state of the internal combustion engine, and in the calculation process of the cumulative distribution, it is preferable to obtain accurate distribution information using many sampled sensor output values. For this purpose, the contribution rate of the cumulative distribution calculated from the newly sampled sensor output value is increased, and the frequency data is calculated so as not to greatly depend on the past cumulative distribution stored so far, and the cumulative distribution is obtained. Is preferred.

  Therefore, the frequency data value division processing means 72B determines the division timing based on the crank angle detected by the crank angle sensor 14 as the timing for decreasing the value of the cumulative distribution frequency data. When the sampling means 61 performs sampling every time the crank angle sensor 14 reaches a predetermined crank angle, the value of the frequency data of the cumulative distribution increases in accordance with the changing speed of the crank angle sensor 14. In this case, the cumulative distribution is decreased at the timing when the crank angle of the crank angle sensor 14 outputs the predetermined crank angle (that is, every time the crank angle becomes the predetermined crank angle), so that the total value of the frequency values on the cumulative distribution is reduced. Can be kept constant.

  Further, another timing at which the frequency data value division processing unit 72B decreases the value of the frequency data of the cumulative distribution is preferably a timing after the air flow rate correction unit 63 corrects the intake air flow rate. When the value of the frequency data is decreased at such timing, correction can be performed using a cumulative distribution based on the most sampling data at the time of correction.

  As another timing at which the frequency data value division processing unit 72B decreases the value of the frequency data of the cumulative distribution, a timing at which the maximum value of the frequency data of the cumulative distribution becomes equal to or greater than a predetermined value is preferable. When the frequency data value is decreased at such timing, a cumulative distribution with a large amount of sampling data can always be obtained.

  Then, each time the output value is sampled, the frequency data value addition processing unit 72C adds to the data value of the frequency of the cumulative distribution divided by the frequency data value division processing unit 72B based on the sampled sensor output value. To update the state of the cumulative distribution.

  As described above, as shown in FIGS. 9 and 10A, the frequency data value addition processing unit 72C performs the sampling for each value of the sensor output value based on the sampled sensor output value every time sampling is performed. Since the cumulative distribution is obtained by performing addition processing on the data value of the frequency and the state of the distribution is updated, it is only necessary to store only the updated cumulative distribution as shown in FIG. As shown in (b), since it is not necessary to store data relating to the sensor output value of the airflow sensor 20 at every sampling timing, the storage capacity of the apparatus can be reduced.

  Further, every time sampling is performed, only the newly sampled sensor output value is used to calculate the frequency data based on the output value and the cumulative distribution is updated, so that the calculation load of the CPU does not increase. Compared with the case where the data is stored at each sampling timing, the frequency data is calculated once in the correction timing, and the cumulative distribution is obtained, the load balance of the CPU can be stabilized and the calculation load can be reduced. it can.

  The sampled data is converted into the intake air flow rate by the flow rate conversion means 62, and the cumulative distribution calculation means 72 obtains the cumulative distribution using the converted intake air flow rate. Using the sensor output value before conversion into the air flow rate, the cumulative distribution calculating means 72 may calculate the frequency for each value and obtain the cumulative distribution of these frequencies.

  FIG. 11 shows a flowchart performed by the sampling means 61 and the cumulative distribution calculating means 72. First, in step 101, the sampling timing switching processing means 61A compares the engine speed with a predetermined value C3. If the predetermined value C3 is larger than the engine speed, the process proceeds to step 102, where the sampling processing means 61B determines that the air flow sensor is in the airflow sensor when the output value of the crank angle sensor 14 reaches the predetermined output value. 20 sensor output values are sampled. In step 103, the frequency data value addition processing unit 72C performs a process of adding to the frequency value of the sensor output value corresponding to the sensor output value, and updates the state of the cumulative distribution.

  After this addition processing, the routine proceeds to step 104, where the frequency data value division processing means 72B compares the crank angle obtained from the crank angle sensor 14 with the predetermined value C5. When the crank angle is the predetermined value C5, the routine proceeds to step 105, where the frequency data value division processing means 72B sets the frequency data values of all output value areas in the frequency data division value setting means 72A. Divide by the division value, perform subtraction processing, and end the operation. If the crank angle is not equal to the predetermined value C5, the calculation is terminated as it is.

  On the other hand, if the engine speed is larger than the predetermined value C3 in step 101, the process proceeds to step 106, where the sampling processing means 61B samples the sensor output value of the airflow sensor 20 at every predetermined interval C4. , Go to Step 107. In step 107, as in step 103, the frequency data value addition processing means 72C performs processing for adding to the frequency data value of the sensor output value corresponding to this sensor output value, and updates the state of the cumulative distribution. , Go to Step 108. In step 108, the frequency data value division processing means 72B determines whether it is the timing when the air flow rate correction means 63 performs the correction calculation of the intake air flow rate. If it is the timing for performing the correction calculation, the process proceeds to step 105, where the frequency data values in all output value areas are divided by the set division value, the subtraction process is performed, and the state of the cumulative distribution is updated. , The operation is terminated.

  Further, in step 108, if it is not the timing for performing the correction calculation, the frequency data value division processing means 72B further proceeds to step 109, and among the frequency data values in all output regions, the frequency data value ( Specifically, it is determined whether the peak value of the frequency data constituting the cumulative distribution is greater than a predetermined value C6. In step 109, if the peak value of the frequency data value is larger than the predetermined value C6, the process proceeds to step 105, where the frequency data values in all output value areas are set division values. Subtraction processing is performed, the state of the cumulative distribution is updated, and the calculation is terminated. In step 109, if the peak value of the frequency data value is smaller than the predetermined value C6, the calculation is terminated.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention described in the claims. Design changes can be made.

  In the present embodiment, the example in which the cumulative distribution of the output voltage that is the sensor output value of the airflow sensor is used as the data used for the cumulative distribution has been described, but the embodiment of the present invention is not necessarily limited to the output voltage of the airflow sensor. Instead, an output signal from the airflow sensor that is not a voltage signal, or a signal that is converted by the CPU using the output signal from the airflow sensor may be used.

  Also in this embodiment, it is considered that an error occurs between the actual flow rate and the detected flow rate due to the response delay of the air flow sensor and the non-linear relationship between the air flow rate and the output voltage of the air flow sensor. Correction means for reducing such errors may be provided.

  Furthermore, in the present embodiment, the sensor output value sampled by the sampling means is converted into the intake air flow rate. However, for example, the sensor output value may be converted before sampling, or may be converted when the air flow rate is corrected. The timing for converting the sensor output value is not particularly limited as long as the intake air flow rate can be calculated by obtaining the cumulative distribution.

  As an application example of the present invention, it is particularly effective for an air flow sensor that can measure only the flow rate of air flowing in one direction.

1 is an overall configuration diagram of an MPI (multi-cylinder fuel injection) type four-cylinder internal combustion engine according to an embodiment of the present invention. The block diagram of the control unit (control apparatus) shown in FIG. 1, and the sensor and actuator connected to it. FIG. 2 is an internal calculation block diagram of a CPU provided in the control device for the internal combustion engine 1 shown in FIG. 1. It is a figure for demonstrating the calculation of CPU when the inhaled air shown in FIG. 3 is a forward flow, (1) is a waveform figure of the actual air flow rate at the time of a forward flow, (2) is a figure of (1). The output waveform figure of the airflow sensor based on an air flow rate. It is a figure for demonstrating the calculation of CPU when the inhaled air shown in FIG. 3 is a backflow, (1) is a wave form diagram explaining the change of the actual air flow rate at the time of a backflow, (2) is The conceptual diagram of the detection waveform of the air flow rate of (1), (3) is the output waveform diagram of the airflow sensor based on the air flow rate of (1). FIG. 6 is a diagram showing a cumulative distribution used for calculating the forward flow and the reverse flow states shown in FIG. 4 and FIG. 5, (1) is a diagram showing a cumulative distribution when no reverse flow occurs, and (2) is The figure showing cumulative distribution in case backflow has occurred. FIG. 4 is a detailed calculation block diagram of sampling means and cumulative distribution calculation means shown in FIG. 3. FIGS. 8A and 8B are diagrams for explaining a calculation process of the cumulative distribution calculation unit shown in FIG. 7, in which FIG. 7A is a diagram showing a relationship between an engine speed and an intake air flow rate (air flow rate), and FIG. The figure which showed the relationship between the valve opening degree of and the air flow rate. The figure for demonstrating the processing timing of the sampling means shown in FIG. 3, a cumulative distribution calculating means, and an air flow rate correction means. It is a figure explaining the preservation | save data amount which should be preserve | saved at a control unit, (a) is a figure for demonstrating the data preservation amount which concerns on this embodiment, (b) demonstrates the conventional data preservation amount. Figure for. The flowchart which the sampling means and cumulative distribution calculation means shown in FIG. 7 perform.

Explanation of symbols

2 Air cleaner 3 Intake pipe 4 Throttle valve (throttle)
5 Throttle body 6 ISC valve 7 Collector 8 Throttle sensor 9 Pressure regulator 10 Internal combustion engine control device (control unit)
11 Fuel pump 12 Fuel tank 13 Injector (fuel injection valve)
15 cylinder 14 crank angle sensor 18 piston 19 water temperature sensor 20 air flow sensor 24 air-fuel ratio sensor 26 power transistor 27 starter switch 28 ignition switch 30 battery 33 catalyst 60 intake air flow rate calculation means 61 sampling means 61A sampling timing switching processing means 61B sampling processing means 62 Flow rate conversion means 63 Air flow rate correction means 70 Backflow correction amount calculation means 72 Cumulative distribution calculation means 72A Frequency data division value setting means 72B Frequency data value division processing means 72C Frequency data value addition processing means 73 Quantitative waveform feature calculation means 74 Reverse flow ratio calculation means

Claims (10)

A control device for an internal combustion engine comprising intake air flow rate calculation means for calculating an intake air flow rate based on an output value of an intake air flow rate detection device,
The intake air flow rate calculating means calculates the frequency for each value of the sampled output value, sampling means for sampling the output value at a predetermined timing, and calculates the cumulative distribution state of the frequency for each value. A cumulative distribution calculating means for calculating, and an intake air flow rate correcting means for correcting the sampled output value based on the calculated cumulative distribution state;
The control apparatus for an internal combustion engine, wherein the cumulative distribution calculation means updates the cumulative distribution state by inputting the sampled output value every time the sampling means samples the output value. The cumulative distribution calculation means includes frequency data value addition processing means for performing a process of adding the sampled output value to the frequency data value each time the output value is sampled,
Frequency data value reduction processing means for performing processing for reducing the value of the frequency data at each predetermined timing,
2. The control of the internal combustion engine according to claim 1, wherein the cumulative distribution state is updated based on the value of the frequency data obtained by the frequency data value addition processing means and the frequency data reduction processing means. apparatus.   3. The internal combustion engine according to claim 2, wherein the timing at which the frequency data value reduction processing unit decreases the value of the frequency data is a timing at which a crank angle of the internal combustion engine becomes a predetermined crank angle. Control device.   The timing at which the frequency data value reduction processing unit decreases the value of the frequency data is a timing at which the intake air flow rate correction unit corrects the intake air flow rate. Control device for internal combustion engine.   5. The timing at which the frequency data value reduction processing means decreases the frequency data value is a timing at which the frequency data value of the cumulative distribution exceeds a predetermined data value. The control device for an internal combustion engine according to any one of the preceding claims.   6. The frequency data value reduction processing means performs a process of reducing the value of the frequency data by dividing the value of the frequency data by a predetermined value. The internal combustion engine control device described.   7. The control apparatus for an internal combustion engine according to claim 6, wherein the frequency data value reduction processing means performs a process of setting a division value for decreasing the value of the frequency data based on a rotational speed of the internal combustion engine. .   7. The internal combustion engine according to claim 6, wherein the frequency data value reduction processing unit performs a process of setting a division value for reducing the frequency data based on an opening degree of a throttle valve of an intake air flow rate. Control device.   The sampling means samples the output value at a predetermined time interval when the rotational speed of the internal combustion engine is larger than a predetermined rotational speed, and when the rotational speed is smaller than the predetermined rotational speed, The control apparatus for an internal combustion engine according to any one of claims 1 to 8, wherein the output value is sampled every time the crank angle of the internal combustion engine becomes a predetermined angle.   The sampled output value used by the cumulative distribution calculating means for calculating the cumulative distribution state is an output value converted into an intake air flow rate. Control device for internal combustion engine.

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