JP4246676B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with an air flow rate detection device, and in particular, when the power supply voltage supplied to the air flow rate detection device is reduced, it is stable without being affected by the decrease in the power supply voltage. The present invention relates to a control device for an internal combustion engine that can be controlled.

  2. Description of the Related Art Conventionally, a control device for an internal combustion engine has disposed an air flow rate detection device (air flow sensor) in an intake pipe of the internal combustion engine in order to detect an air flow rate taken into the internal combustion engine. The control device controls the fuel injection amount using the intake air amount detected by the air flow rate detection device.

  In recent years, it has become an important issue to improve the emission performance of an internal combustion engine, and the control device converts measured values output from each sensor into digital values and uses the converted digital values. The target fuel injection amount is calculated by a digital arithmetic device. And it is common to control fuel injection quantity by digital control based on the result calculated in this way.

  When the engine of an internal combustion engine that performs the above-described digital control is started, the power supplied from the power supply device such as a battery to the air flow rate detection device may decrease. Due to the decrease, an error occurs in the measurement value output from the air flow rate detection device. Based on the measurement value having such an error, the calculation device converts the measurement value into an intake air amount, and calculates the fuel injection amount based on the intake air amount. Compared with the fuel injection amount calculated when the engine is operating normally, a calculation error corresponding to the magnitude of the detection error occurs, so the control device normally controls the fuel injection amount of the internal combustion engine. I can't.

  Such a problem does not occur only in a sensor such as an air flow rate detection device, but a similar problem occurs in an actuator. For this reason, for example, in a device for controlling the throttle valve of an internal combustion engine, when a large current flows to the starter motor during start cranking, and as a result, the battery voltage becomes lower than the drive guarantee voltage of the drive means for driving the throttle valve, There has been proposed an exhaust emission control device for an engine in which the throttle valve is maintained at a preset intermediate opening degree (see cited document 1).

  In addition to this, as an engine starting device, when the detected battery voltage is lower than the reference voltage, a device that forcibly shuts off the energization circuit to the self-starter and prohibits the starting by the self-starter has been proposed. (See Patent Document 2).

  As for the air flow rate detection device, the fluctuation of the reference voltage signal is output by outputting a corrected detection signal obtained by correcting the detection signal in a circuit built in the air flow rate detection device in accordance with the change of the reference voltage signal. Some have been proposed (see Patent Document 3).

JP 2001-182590 A Japanese Patent Laid-Open No. 5-172021 Japanese Patent Laid-Open No. 9-203651

  However, the air flow rate detection device described in Patent Document 3 is configured to output a correction detection signal in order to improve the output accuracy of the air flow rate detection device in the built-in output circuit. When the supply voltage is lower than the voltage necessary for driving the circuit (the drive guarantee voltage cannot be secured), an error occurs in the measured value of the air flow rate detection device.

  By the way, in general, in an internal combustion engine control device, an engine starter that consumes a large amount of electric power is activated at the time of starting. Therefore, the power supply voltage supplied from the same power supply device as the engine starter is greatly increased at the same time as the starter operation starts. descend.

  At this time, if the power supply voltage supplied to the arithmetic device is lower than the voltage value necessary for the arithmetic device to operate normally, even if a large error occurs in the measurement value of the air flow rate detection device, The arithmetic unit stops the arithmetic operation, and then restarts the arithmetic operation when the power supply voltage becomes equal to or higher than a predetermined value. For this reason, since the error of the measured value in the air flow rate detection device is not reflected in the calculation of the calculation device, there is no particular problem when considering the whole engine control.

  However, when the power supply voltage value supplied to the computing device can operate the computing device normally, but has dropped to a voltage value at which an output error occurs in the air flow rate detection device (a drive guarantee voltage cannot be secured). The air flow rate detection device outputs a voltage value including an output error, and the calculation device calculates the intake air amount or the fuel injection amount based on the measurement value including the output error. The control device controls the internal combustion engine for the time being, but cannot control the desired accuracy.

  In particular, when the drive guarantee voltage of the air flow rate detection device is larger than the drive guarantee voltage of the arithmetic device, when the power of the battery or the like decreases, the air flow rate detection device does not operate properly. Even if the arithmetic device is driven normally, the control device controls the internal combustion engine without obtaining the desired accuracy calculation result because the accuracy of the measurement value of the air flow rate detection device which is the premise of the calculation is low. Result.

  Therefore, the present invention has been made to solve the above-described problem, and the object of the present invention is to reduce the voltage supplied to the air flow rate detection device and prevent the air flow rate detection device from outputting an accurate measurement value. However, the calculation device calculates an effect to reduce the influence of the output error of the air flow rate detection device, and provides an internal combustion engine control device that improves the accuracy of fuel injection amount injection control.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention comprises an intake air amount calculating means for calculating an intake air amount based on an output from an intake air amount measuring means, and a fuel based on the intake air amount. A control device for an internal combustion engine, comprising: a fuel injection amount calculating means for calculating an injection amount, wherein the control device, when the voltage supplied to the intake air amount measuring means is less than or equal to a predetermined voltage, The intake air amount or the fuel injection amount is calculated based on the supply voltage.

  The control device for an internal combustion engine of the present invention configured as described above corrects the measured value of the intake air amount measuring means accurately when the supply voltage supplied to the intake air amount measuring means is not sufficiently secured. be able to. As a result of performing such correction, the amount of fuel injection (such as fuel injection pulse) can be calculated accurately, and the internal combustion engine can be controlled with higher accuracy. Further, in the case of an airflow sensor or the like provided with a digital correction circuit in the intake air amount measuring means, a calculation adapted to digital characteristics can be performed by providing a predetermined voltage as a threshold value. In particular, since the supply voltage is likely to fluctuate when the internal combustion engine is started, an appropriate amount of fuel can be injected without waste even in such a case. Furthermore, by calculating in this way, it becomes possible to use an apparatus for measuring the intake air amount having a high minimum guaranteed voltage, and the applicable range of equipment mounted on the internal combustion engine can be expanded.

  The control apparatus for an internal combustion engine according to the present invention includes a correction equation or table relating to the supply voltage, and the intake air amount or the fuel injection amount is calculated based on the correction equation or the table. The control apparatus for an internal combustion engine of the present invention configured as described above calculates the intake air amount and the fuel injection amount using a correction equation or table corresponding to the supply voltage, and is thus supplied to the intake air amount measuring means. The internal combustion engine can be controlled without being affected by fluctuations in the supply voltage.

  The control apparatus for an internal combustion engine according to the present invention is characterized in that when the supply voltage is equal to or lower than a predetermined voltage, the intake air amount or the fuel injection amount is replaced with a constant value. The control device is characterized in that the constant value is the intake air amount or the fuel injection amount immediately before the supply voltage becomes equal to or lower than the predetermined voltage. The control device for an internal combustion engine of the present invention configured as described above can simply replace the intake air amount or the fuel injection amount with a constant value, thereby reducing the calculation load of the control device. Further, since the intake air amount or the fuel injection amount immediately before the voltage becomes a predetermined voltage or lower is continuously used, the fuel injection amount injected by the internal combustion engine does not fluctuate greatly, and the internal combustion engine is controlled stably. be able to. Preferably, the intake air amount or the fuel injection amount may be replaced based on a control amount at the time of idling operation. In this case as well, stable control of the internal combustion engine can be performed similarly.

  The control apparatus for an internal combustion engine according to the present invention calculates the intake air amount or the fuel injection amount based on the supply voltage and the rotational speed of the internal combustion engine when the supply voltage is equal to or lower than the predetermined voltage. It is characterized by doing. The control apparatus for an internal combustion engine of the present invention configured as described above can correct these control variables with high accuracy particularly at the time of engine start in which the supply voltage supplied to the intake air amount measuring means tends to decrease.

  The control device for an internal combustion engine according to the present invention calculates intake air amount calculation means for calculating an intake air amount based on an output from the intake air amount measurement means, and calculates a fuel injection amount based on the intake air amount. A control device for an internal combustion engine, comprising: a fuel injection amount calculation means, wherein the control device rotates the internal combustion engine when the voltage supplied to the intake air amount measurement means is a predetermined voltage or less. The intake air amount or the fuel injection amount is calculated using a number.

  The control apparatus for an internal combustion engine according to the present invention configured as described above uses the rotational speed of the internal combustion engine to approximate the intake when the supply voltage supplied to the intake air amount measuring means is not sufficiently secured. The measurement value of the air amount measuring means can be corrected. As a result of such correction, the fuel injection amount can also be accurately calculated, and the internal combustion engine can be controlled with higher accuracy. Further, in the case of an airflow sensor or the like provided with a digital correction circuit in the intake air amount measuring means, a calculation adapted to digital characteristics can be performed by providing a predetermined voltage as a threshold value. In particular, since the supply voltage is likely to fluctuate when the internal combustion engine is started, an appropriate amount of fuel can be injected without waste even in such a case. Furthermore, by calculating in this way, it becomes possible to use an apparatus for measuring the intake air amount having a high minimum guaranteed voltage, and the applicable range of equipment mounted on the internal combustion engine can be expanded.

  The control apparatus for an internal combustion engine according to the present invention estimates an intake air amount from when the supply voltage becomes equal to or lower than the predetermined voltage until the supply voltage becomes equal to or higher than the predetermined voltage, based on an intake air amount immediately after the predetermined voltage is exceeded. The fuel injection amount is calculated based on the estimated intake air amount.

  The control apparatus for an internal combustion engine of the present invention configured as described above reexamines the intake air amount that could not be accurately calculated in the past, and calculates the fuel injection amount based on the reconsidered intake air amount. Therefore, fuel can be injected without excess and deficiency, and the internal combustion engine can be controlled more accurately. In particular, when the distance between the intake air amount measuring means arranged at the inlet of the intake pipe and the injector into which fuel is injected is long, the intake air detected by the intake air amount measuring means until the intake air reaches the injector. Therefore, it is necessary to calculate the fuel injection amount in consideration of such a time delay, so it is necessary to review the intake air amount that could not be corrected accurately in the past. It is particularly effective when doing so. When the engine is started, the supply voltage supplied to the intake air amount measuring means is likely to decrease, and the intake air amount can be corrected particularly accurately.

  The control apparatus for an internal combustion engine according to the present invention is based on the intake air amount immediately before the supply voltage becomes equal to or lower than the predetermined voltage and the intake air amount immediately after the supply voltage becomes equal to or higher than the predetermined voltage. It is characterized in that the intake air amount from when the supply voltage becomes equal to or lower than the predetermined voltage to when the supply voltage becomes equal to or higher than the predetermined voltage is estimated, and the fuel injection amount is calculated based on the estimated intake air amount.

  Since the control device for an internal combustion engine of the present invention configured as described above uses the intake air amount before and after the intake air amount that could not be accurately corrected in the past, it is more accurate than the above estimation. The intake air amount so far can be estimated, and the fuel injection amount can also be calculated based on the estimated value.

  The control apparatus for an internal combustion engine according to the present invention is characterized in that the fuel injection amount is limited based on a change amount of the fuel injection amount. The control device for an internal combustion engine of the present invention configured as described above restricts the fuel injection amount based on the change amount of the fuel injection amount, so that it is possible to prevent sudden torque fluctuations and the like. The unnecessary load may not be applied to the internal combustion engine.

  According to the control device for an internal combustion engine of the present invention, even when the voltage supplied to the intake air amount measuring means such as an air flow sensor is reduced and an error occurs in the output of the intake air amount measuring means or the output is lost, It is possible to calculate the air flow rate or the fuel injection amount while reducing the error in the arithmetic unit. As a result, it is possible to stably inject fuel without fluctuations, so that comfortable travel is possible.

  Several embodiments of a control device for an internal combustion engine according to the present invention will be described below 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 a first 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 amount measuring means). If so, it should be applied to all internal combustion engines.

  In FIG. 1, an internal combustion engine (engine) 1 is a so-called MPI type four-cylinder internal combustion engine. A throttle body 5 and a collector 7 are arranged. Further, the collector 7 and each cylinder 15 are connected by an intake branch pipe 16. Each intake branch pipe 16 is provided with an injector 13 for supplying fuel to each cylinder 15, and each cylinder 15 is provided with a spark plug 25 for igniting the supplied fuel. . An exhaust pipe 23 is connected to the exhaust side of each cylinder 15, and a catalyst 33 is disposed in the exhaust pipe 23.

  Further, the control unit 10 inputs signals from the air flow sensor 20, the crank angle sensor 14, the throttle sensor 8, the air / fuel ratio sensor 24, and the water temperature sensor 19, and from the battery 30 via the starter switch 27 and the ignition switch 28. Power is also input. 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 operation of each sensor and actuator described above 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 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.

  Here, 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 an air flow sensor (intake air amount measuring means) 20 provided at the outlet of the air cleaner 2 for detecting the air flow rate. 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 spark plug 25 ignites the air-fuel mixture and burns 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 40 and an LSI 42, and the RESET terminal of the LSI 42 is connected to the power supply IC 40 so that a RESET signal 41 controlled by the power supply IC 40 can be transmitted. It is connected. 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 shows an internal circuit diagram of the airflow sensor 20 according to the present embodiment. The airflow sensor 20 according to the present embodiment includes a bypass passage that allows intake air to pass therethrough, and includes a heating resistor (hot wire) Rh and a temperature-sensitive resistor (cold wire) Rc in the passage. As shown in FIG. 3, the airflow sensor 20 has a feedback circuit 60 by a bridge circuit, and when the battery supply voltage VB is supplied from the battery 30, the feedback circuit 60 uses the voltage corresponding to the intake air flow rate. Is output.

  Specifically, the temperature of the hot wire Rh changes due to the heat transfer phenomenon according to the air flow rate to be measured, and as a result, the resistance value of the heating resistor Rh changes according to the air flow rate. For example, when the air flow rate increases, the amount of heat taken from the hot wire Rh increases, and the equilibrium condition of the bridge circuit is lost. Then, the heating current IH is supplied so as to compensate for the amount of heat taken to satisfy the equilibrium condition, and the hot wire Rh is controlled to have a constant resistance value. The heating current IH is converted into a voltage signal by the resistor R1 and output. Further, the hood back circuit 60 compensates for a change in the amount of heat generated due to a change in the intake air temperature due to the cold wire Rc.

  Further, a digital output correction circuit 61 is provided downstream of the feedback circuit 60 to correct the output voltage of the feedback circuit 60. The digital output correction circuit 61 is also supplied with a voltage obtained from the battery 30. The present embodiment is not particularly limited to the case where the airflow sensor 20 is provided with the digital output correction circuit 61.

  FIG. 4 is an internal calculation block diagram of a CPU (calculation means) 43 provided in the control device 10 of the internal combustion engine 1 according to the present embodiment. As shown in FIG. 4, the voltage signal output from the airflow sensor 20 is digitally converted by the A / D converter 71 in the LSI 42 and output as a sensor output voltage US corresponding to the intake air amount at predetermined time intervals. The This sensor output voltage US is used for control calculation in the CPU 43 which is a calculation means. The voltage VB supplied from the battery 30 to the airflow sensor 20 is also converted into a digital value by the A / D converter 71. Then, the calculating means 43 calculates to correct the sensor output voltage US representing the output voltage of the airflow sensor 20, and further converts this calculated value into a converted intake air amount Q corresponding to the intake air amount. The fuel injection pulse width TP is calculated from the intake air amount Q.

  Specifically, the calculation means 43 includes a voltage comparison means 72, a correction means 73, a VQ conversion means (intake air amount calculation means) 74, and a fuel injection pulse width calculation means (fuel injection amount calculation means) 75. And has.

The voltage comparison means 72 compares the voltage (battery supply voltage) VB (digital value) supplied from the battery 30 to the airflow sensor 20 with predetermined voltages (VB ₁ and VB ₂ described later) set in advance. Yes. Then, the voltage comparison unit 72 outputs a comparison result such as a voltage ratio obtained by the battery supply voltage VB and the comparison unit to the correction unit 73.

  The correcting unit 73 corrects the sensor output voltage US based on the output signal from the voltage comparing unit 72 as described later. The VQ conversion unit 74 converts the corrected sensor output voltage into an intake air amount Q (digital value) by referring to a table stored in advance in the LSI 42. Further, the fuel injection pulse width calculating means 75 uses the intake air amount Q and the engine speed NRPM (digital value), and as a fuel injection amount, a fuel injection pulse width TP (digital value) corresponding to the cylinder filling efficiency. Is calculated.

  That is, the fuel injection pulse width calculation means 75 calculates the intake air flow rate per rotation by dividing the intake air amount Q calculated by the VQ conversion means 74 by the engine speed NRPM. Then, by performing calculation (for example, filtering process) in consideration of the phase difference (time delay) between the change in the air flow rate of the intake pipe 3 detected by the air flow sensor 20 and the change in the air flow rate sucked into the cylinder, The fuel injection pulse width TP (digital value) is calculated.

  The correction means 73 provided in the calculation means 43 is arranged downstream of the A / D converter 71 so as to correct the sensor output voltage US based on the voltage ratio between the battery supply voltage VB and a predetermined voltage set in advance. Although arranged, the correction means 73 may be arranged downstream of the VQ conversion means 74 to correct the intake air amount Q based on the voltage ratio, and fuel injection is performed based on the voltage ratio. It may be provided downstream of the fuel injection pulse calculation means 75 to correct the pulse width TP.

FIG. 5 is a relationship diagram between the sensor output voltage US output from the airflow sensor 20 before correction and the battery supply voltage VB supplied to the airflow sensor 20. As shown in FIG. 5, when the battery supply voltage VB is sufficiently high (VB ₂ or more), the sensor output voltage US of the airflow sensor 20 is stable as US ₂ . Therefore, the airflow sensor 20 can output the sensor output voltage US corresponding to the intake air flow rate of the intake pipe 3.

However, when the battery supply voltage VB decreases and the voltage value becomes a voltage in a predetermined section (VB _{1 to} VB ₂ ), the sensor output voltage US of the airflow sensor 20 decreases with an error. That is, as shown in FIG. 3 described above, the airflow sensor 20 forms a feedback circuit 60 by a bridge circuit and outputs a sensor output voltage US corresponding to the intake air flow rate, so that the battery supply voltage VB is equal to or lower than a predetermined voltage. When this happens, the sensor output voltage UB also decreases accordingly, feedback is not normally performed, and an error corresponding to the decrease in the battery supply voltage VB occurs.

Further, when the battery supply voltage VB decreases and becomes equal to or less than the predetermined voltage VB ₁ , the value of the sensor output voltage US that is the output of the airflow sensor 20 is a completely different value. Specifically, as shown in FIG. 3, in the airflow sensor 20 including the digital output correction circuit 61 for correcting the output voltage, when the battery supply voltage VB becomes equal to or lower than the voltage value at which the LSI 42 operates, the intake air A voltage value that is completely unrelated to the change in quantity is output as the sensor output value US.

  FIG. 6 is a diagram for explaining the calculation contents of the calculation means 43 of the present embodiment. A time calendar waveform (timing chart) when the engine is started using the airflow sensor 20 having the characteristics shown in FIG. ). A solid line waveform 81 is a waveform of the sensor output voltage of the airflow sensor 20 that should be output originally, and a broken line waveform 82 is a waveform of the sensor output voltage when affected by the voltage drop of the battery supply voltage VB.

As shown in FIG. 6, when the starter is operated at the time of starting the engine, the battery supply voltage VB decreases (time T ₁ ). At this time, if the battery supply voltage VB becomes equal to or lower than the predetermined voltage VB ₁ , the output voltage of the airflow sensor 20 is not output as shown by the broken line waveform 82. Thereafter, as the engine speed increases, the battery supply voltage VB increases. Until the battery supply voltage VB becomes equal to or higher than the predetermined voltage VB ₁ (time T ₂ ), the airflow sensor 20 outputs the sensor output voltage US. Will continue to be output normally.

The battery supply voltage VB exceeds the predetermined voltage VB _1, until a predetermined voltage VB _2, the sensor output voltage US of the air flow sensor 20 has an error that depends on the size of the battery supply voltage VB. When the battery supply voltage VB exceeds the predetermined voltage VB _2, air flow sensor 20 outputs a sensor output voltage US which is not at all relevant to the change in the intake air amount.

Thus, the battery supply voltage VB, in the case of the predetermined voltage VB ₂ or less, the output voltage of the air flow sensor 20 becomes such a voltage waveform of the broken line waveform 82. Therefore, the correction means 73, (1) the battery supply voltage VB takes and when taking a voltage _(a value between VB 1 through Vb ₂₎ of a predetermined interval, (2) the battery supply voltage VB is less than the predetermined voltage VB ₁ Sometimes, the sensor output voltage US is corrected.

(1) When the battery supply voltage VB takes a voltage in a predetermined interval (a value between VB _{1 and} VB ₂ ), the magnitude of the error of the sensor output voltage US output from the airflow sensor 20 is the battery supply voltage VB It changes according to the size of. Therefore, this error can be calculated from the battery supply voltage VB and the sensor output voltage US including the error, and the correction means 73 is a correction formula based on the battery voltage VB or a table corresponding thereto. Thus, the sensor output voltage US of the airflow sensor 20 can be corrected.

(2) When the battery supply voltage VB is equal to or lower than the predetermined voltage VB ₁ , even if air is sucked into the intake pipe 3, the power supplied to the airflow sensor 20 is insufficient, so the airflow sensor 20 Does not output (output voltage = 0V) or outputs a completely different voltage value. In such a case, since the sensor output voltage US does not depend on the battery supply voltage VB, the sensor output voltage US cannot be calculated from the change in the battery supply voltage VB. Therefore, when the battery supply voltage VB is equal to or lower than the predetermined voltage VB ₁ , as described later, the sensor output voltage US is estimated, and the sensor output voltage US is corrected based on the estimated value.

FIG. 7 is a timing chart of each parameter when the calculation means 43 performs the correction of the sensor output voltage US and the calculation of the fuel injection pulse width TP, and the waveform 11A corrects the sensor output voltage US. The waveform 11B is a waveform of the fuel injection pulse width TP calculated based on the sensor output voltage US of the waveform 11A. The waveform 12A is a waveform of the estimated output voltage USE estimated by calculation means 43 for calculating a fuel injection pulse width TP at time T _2, waveform 12B is calculated based on waveform 12A, the fuel injection pulse It is a waveform of width TP. Further, the waveform 13B shows an ideal waveform of the fuel injection pulse width TP when there is no error in the output voltage of the airflow sensor 20.

First, as the waveform 11A, correcting means 73, when the battery supply voltage VB is equal to or less than a predetermined voltage VB _1, to correct the sensor output voltage US to a constant value. Since the battery supply voltage VB decreases when the internal combustion engine 1 that operates the starter switch 27 is started, the correction unit 73 corrects the sensor output voltage US immediately before the battery supply voltage VB becomes equal to or lower than the predetermined voltage VB ₁ as a constant value. To do. In this way, by replacing the sensor output voltage US as a constant value and correcting it, the influence on the fuel injection control or other control due to the output error of the airflow sensor 20 can be reduced.

Further, as described above, when the correcting unit 73 is arranged downstream of the VQ converting unit 74 so as to correct the intake air amount Q, immediately before the battery supply voltage VB becomes equal to or lower than the predetermined voltage VB _1. The intake air amount Q may be replaced with a constant air flow rate Q, and when the correcting means 73 is arranged downstream of the fuel injection pulse calculating means 75 to correct the fuel injection pulse width TP, The fuel injection pulse width TP may be replaced with the fuel injection pulse width immediately before the battery supply voltage VB becomes equal to or less than the predetermined voltage VB ₁ as a constant value.

In this manner, when the battery supply voltage VB is a predetermined voltage VB ₁ below, from time _{T 1} to time _{T 2,} the sensor output voltage US of the air flow sensor 20 is replaced with a predetermined value _{US 1A} (waveform 11A). However, this waveform 11A is from time T ₁ to time T _2, is constant US _1A, computing means 43 is to calculate the fuel injection pulse width TP in real time from this value, to actually injected The error becomes larger than the fuel injection pulse width (waveform 13B) (waveform 11B). As a result, at time _{T 3,} the fuel injection pulse width TP is smaller than the value of the ideal waveform 13B, the error ΔTP occurs.

Therefore, in the present embodiment, it is noted that the calculation (for example, filtering process) is performed in consideration of the phase difference (phase delay) of the air flow rate change between the air flow sensor 20 and the cylinder, and the fuel injection pulse width Calculate TP. That is, the value of past sensor output voltage US or the intake air amount Q, since influence the computation result of the subsequent fuel injection pulse width TP, time T _2, the fuel injection pulse width TP immediately after the consideration of the phase delay Then, the calculation is performed using the sensor output voltage US from time T ₁ to time T ₂ . Therefore, in the present embodiment, first, the time T _2, since in order to more accurately calculating the fuel injection pulse width TP, at time T _2,, the sensor output voltage at time T _{1 ~} time T _2, which is a past time US The value is estimated.

Specifically, in order to reduce such an error ΔTP, the output value US _1A of the airflow sensor 20 at time T ₁ (immediately before the battery supply voltage VB becomes equal to or lower than the predetermined voltage VB ₁ ) and time T ₂ (battery supply) the output value _{US 1B} of the air flow sensor 20 immediately after the voltage VB becomes ₁ or more predetermined voltage VB), by linear interpolation using the estimated output voltage uSE of the air flow sensor 20 at time _{T 1} ~ time _{T 2} (waveform 12A ) Then, immediately after the time T _2, based on the estimated output voltage USE, calculates the fuel injection pulse width TP. Here, although the sensor output voltage US is estimated by linear interpolation, the fuel injection pulse width TP may be calculated by obtaining the estimated intake air amount from the intake air amount Q obtained from the sensor output voltage US.

In addition, as a method for estimating the sensor output voltage US when the battery supply voltage VB is equal to or lower than the predetermined voltage VB ₁ or the intake air amount Q, the battery supply voltage VB exceeds the predetermined voltage VB ₁ (VB ≧ The sensor output voltage US or intake air amount Q in the next calculation cycle at the moment (VB ₁ ) is estimated as the sensor output voltage US or intake air amount Q when the battery supply voltage VB is equal to or less than the predetermined voltage VB _1. May be. Similarly to the calculation described above, the fuel injection pulse immediately after the battery supply voltage VB becomes equal to or higher than the predetermined voltage based on the estimated sensor output voltage US (estimated output voltage USE) or the estimated intake air amount Q. The width TP is calculated.

As described above, the calculation for calculating the fuel injection pulse width TP includes a phase difference (phase delay) between a change in the air flow rate in the intake pipe 3 detected by the air flow sensor 20 and a change in the air flow rate in the cylinder of the cylinder 2. Filtering processing that takes into account is included. Therefore, the past sensor output voltage US or the value of the intake air amount Q affects the subsequent calculation result of the fuel injection pulse width TP. Therefore, filtering calculation is performed using the fuel injection pulse width TP in the calculation cycle immediately before the battery supply voltage VB becomes equal to or less than the predetermined voltage VB ₁ and the estimated sensor output voltage US (estimated output voltage USE) or intake air amount Q. The fuel injection pulse width TP of the calculation cycle immediately after the battery supply voltage VB becomes equal to or higher than the predetermined voltage VB ₁ is calculated by more accurately simulating past calculations including As a result, an ideal fuel injection pulse width TP can be obtained before the battery supply voltage VB reaches the predetermined voltage VB ₂ (time T ₃ ), and is not affected by an error in the output of the airflow sensor 20. This makes it possible to perform stable control of the internal combustion engine 1.

Also, when performing the calculation of the fuel injection pulse width TP, operation immediately after the fuel injection pulse width TP and the battery supply voltage VB of the operational cycle just before the battery supply voltage VB exceeds the predetermined voltage VB ₁ exceeds a predetermined voltage VB ₁ It is conceivable that the difference from the cycle fuel injection pulse width TP becomes large. Then, a value is calculated such that the fuel injection pulse width TP calculated from the estimated sensor output voltage US (estimated output voltage USE) or the estimated intake air amount Q becomes an abrupt change amount of the fuel injection pulse width. In such a case, it is desirable to correct so as to limit the calculated fuel injection pulse width TP in order to prevent such a rapid fluctuation.

  Therefore, the change amount of the fuel injection pulse width TP is generally obtained from the change amount of the engine speed NRPM and the change amount of the intake air amount Q. The maximum change amount of the engine speed NRPM and the intake air amount Q is determined by the engine. From the performance of Therefore, since the maximum value of the change in the fuel injection pulse width TP in the predetermined calculation cycle is determined from such a relationship, the calculation means 43 actually provides a limiter based on the maximum value of the fuel injection pulse width TP. It is possible to prevent an abrupt change in the fuel injection pulse width TP.

Thus, as the waveform 11B, estimates the sensor output voltage US of the air flow sensor when the predetermined voltage VB ₁ below, based on the estimated value, the fuel injection pulse upon Immediately after the predetermined voltage VB ₁ or more Since the width TP is calculated, it is possible to reduce the influence of the estimation error when the calculation cannot be performed when the width TP is estimated from the output voltage of the airflow sensor.

  FIG. 8 shows a calculation flowchart when the calculation means 43 of the control device 10 calculates the fuel injection pulse width TP based on the timing chart of FIG. This process is performed after the key is turned on until the key is turned off.

First, at step 110, the battery supply voltage VB and the predetermined voltage VB ₁ are determined to be large or small. When the battery supply voltage VB falls below a predetermined voltage VB _1, the process proceeds to step 111, substitutes the value of the fuel injection pulse width TP just before is smaller than the predetermined voltage VB ₁ to TPtmp. Then, the process proceeds to step 112, and substitutes the output voltage of the air flow sensor 20 just before described later battery supply voltage VB falls below a predetermined voltage VB ₂ (sensor output voltage USC corrected) in UStmp1, the process proceeds to step 113. In step 113, based on TPtmp and UStmp1, the provisional fuel injection pulse width TPC is calculated by simulation calculation including a weighted average process, and the process proceeds to step 114. In step 114, a flag fVBON indicating that the sensor output voltage USC after correction is replaced with an estimated value is set to zero.

On the other hand, if the battery supply voltage VB is equal to or higher than the predetermined voltage VB ₁ in step 110, the process proceeds to step 115. In step 115, it determines the magnitude of the battery supply voltage VB and a given voltage VB _2. If (the battery supply voltage VB is equal to or higher than the predetermined voltage VB ₁ ) and lower than VB ₂ , the process proceeds to step 116, where the sensor output voltage US is multiplied by the battery supply voltage VB and a predetermined value c10 which is a correction coefficient. Then, the corrected sensor output voltage USC is calculated.

Further, when the battery supply voltage VB is higher than the predetermined voltage VB _2, the process proceeds to step 117, the sensor output voltage USC corrected, substituting sensor output voltage US. In step 118, the corrected sensor output voltage USC obtained in this way is substituted into UStmp2, and the process proceeds to step 119.

Step 119, the battery supply voltage VB is a determination step for determining whether it is immediately after exceeding the predetermined voltage VB _2, in step 119, the flag FVBON it is determined whether 1 or 0, FVBON is 1 and If it is determined, the process proceeds to step 120, and the temporary fuel injection pulse width TPC is calculated by simulation calculation including weighted average processing based on the previous value of the temporary fuel injection pulse width TPC and UStmp2 of step 118. In step 123, the flag fVBON is set to 1.

On the other hand, in step 119, if the fVBON is determined to 0, in UStmp1 obtained with UStmp2 step 112 (sensor output voltage immediately after UStmp2 is the battery supply voltage VB becomes a predetermined voltage VB ₂ or more in this case) In step 121, the sensor output voltage US when the past battery supply voltage VB is equal to or lower than the predetermined voltage VB ₁ is estimated by linear interpolation (estimated output voltage USE is calculated), and the process proceeds to step 122. In step 122, based on TPtmp and the estimated output voltage USE estimated in step 121, the current provisional fuel injection pulse width TPC is calculated by simulation calculation including a weighted average process. Proceed to 123, and set fVBON to 0. In step 124, after calculating the provisional fuel injection pulse width TPC, a limiter process is performed on the amount of change from the previous fuel injection pulse width TP to calculate the fuel injection pulse width TP.
As described above, when the intake air amount Q or the fuel injection pulse width TP is corrected, the value immediately before the battery supply voltage VB becomes equal to or less than the predetermined voltage VB ₁ may be corrected as a constant value.

  FIG. 9 is a control flow diagram for explaining the second embodiment. The main difference between the second embodiment and the first embodiment is a method for correcting the sensor output voltage US of the correction means 73. . In the present embodiment, the sensor output voltage US when the battery supply voltage VB decreases is estimated from the engine speed NRPM. It is known that the air pressure in the intake pipe 3 is close to the atmospheric pressure because the intake air amount is small when the engine is started when the battery supply voltage VB decreases. Therefore, assuming that the air pressure in the intake pipe is the same as the atmospheric pressure, the intake air amount is obtained by multiplying a predetermined value obtained from the number of cylinders of the engine and the cylinder volume of each cylinder and the engine speed.

Therefore, as shown in FIG. 9, first, in step 130, the battery supply voltage VB and the predetermined voltage VB ₁ are determined to be large or small. Then, when the battery supply voltage VB is lower than the predetermined voltage VB _1, the process proceeds to step 131, the sensor output voltage US is multiplied by the engine speed NRPM and the predetermined value c 20, the sensor output voltage after correcting the value USC. On the other hand, when the battery supply voltage VB is equal to or higher than the predetermined voltage VB ₁ , the process proceeds to step 132, and the sensor output voltage US is substituted as the corrected sensor output voltage USC (no correction is performed). Therefore, when the engine is started when the battery supply voltage VB is reduced, the amount of intake air is small and the air pressure inside the intake pipe 3 is close to atmospheric pressure. Therefore, the sensor output voltage US can be simply accurately determined based on the engine speed NRPM. You can calculate well.

  As mentioned above, although two embodiment of this invention was explained in full detail, this invention is not limited to the said embodiment, In the range which does not deviate from the mind of this invention described in the claim, it is various. The design can be changed.

In the first embodiment, when the battery supply voltage VB is equal to or lower than the predetermined voltage VB ₁ , correction is performed using the sensor output voltage US immediately before the battery supply voltage VB. However, for example, an internal combustion engine with a small intake air amount that operates a starter switch Since the battery supply voltage VB decreases at the time of starting, when the battery supply voltage VB becomes equal to or lower than the predetermined voltage VB ₁ , the calculation means outputs a sensor output with a value lower than the sensor output voltage detected during idle operation as a constant value. The voltage US may be substituted. Further, the calculation means may replace the intake air amount Q with a constant air flow rate lower than the air flow rate during idling downstream of the VQ conversion means so as to correct the intake air amount Q. The calculation means may replace the fuel injection pulse width TP with a constant fuel injection pulse width lower than the fuel injection pulse width during idling downstream of the fuel injection pulse calculation means to correct the fuel injection pulse width TP. . Further, such a replacement may use a correction formula or a table.

  Further, in the first embodiment, when calculating the fuel injection pulse width corresponding to the fuel injection amount, the calculation is performed using linear interpolation. However, particularly when the internal combustion engine is started, the value calculated in this way is not much. Since it does not fluctuate, the calculation time can be shortened by storing it in a table or the like in advance and reading the value from the table or the like.

Further, in the second embodiment, the threshold value of the predetermined voltage VB ₂ shown in the first embodiment may be provided to correct the intake air amount or the fuel injection amount by a correction formula or the like, and the sensor output voltage such as linear interpolation is estimated. Thus, the fuel injection amount may be calculated.

Further, in the present embodiment, based on the relationship between the supply voltage and the output voltage of the air flow sensor of the battery has been set a predetermined voltage VB ₁ and VB ₂ as the threshold voltage of the battery, these voltages are supplied battery The threshold value and the number of threshold values may be determined from a characteristic diagram showing the relationship between the voltage and the output voltage of the airflow sensor.

  When the minimum guaranteed voltage for the air flow sensor to operate normally is higher than the minimum guaranteed voltage for the control unit (control device) to operate normally, the present invention is very effective and is likely to be used. .

The whole block diagram of the control apparatus of the internal combustion engine which concerns on this embodiment. The block diagram of the control unit of FIG. FIG. 2 is an internal circuit diagram of the air flow sensor of FIG. 1. FIG. 3 is a block diagram of a CPU (calculation means) in FIG. 2. FIG. 6 is a relationship diagram of an output voltage output from before the air flow sensor is corrected and a supply voltage of a battery supplied to the air flow sensor. The timing chart of the sensor output voltage of an airflow sensor at the time of internal combustion engine start-up, and a battery supply voltage. The timing chart of each parameter for demonstrating the calculation content of the calculating means of FIG. The flowchart when the calculating means shown in FIG. 4 calculates a fuel injection pulse width. The flowchart when correct | amending a sensor output voltage from an engine speed.

Explanation of symbols

1 Internal combustion engine 2 Air cleaner 3 Intake pipe 4 Throttle valve
5 Throttle body 6 ISC valve 7 Collector 8 Throttle sensor 9 Pressure regulator 10 Control unit (control device)
11 Fuel pump 12 Fuel tank 13 Injector 14 Crank angle sensor 15 Cylinder 19 Water temperature sensor 20 Thermal air flow sensor 24 O ₂ sensor (air-fuel ratio sensor)
26 power transistor 27 starter switch 28 ignition switch 30 battery 33 catalyst 42 LSI
43 CPU (calculation means)
73 Correction means 74 VQ conversion means (intake air amount calculation means)
75 Fuel injection pulse calculation means (fuel injection amount calculation means)

Claims (8)

An internal combustion engine comprising: an intake air amount calculating unit that calculates an intake air amount based on an output from an intake air amount measuring unit; and a fuel injection amount calculating unit that calculates a fuel injection amount based on the intake air amount. A control device,
When the voltage supplied to the intake air amount measuring means is equal to or lower than a predetermined voltage, the control device corrects the intake air amount or the fuel injection amount to be increased based on the supply voltage. Control device for internal combustion engine. The said control apparatus is provided with the correction formula or table regarding the said supply voltage, The said intake air amount or the said fuel injection amount is carry out an increase correction | amendment based on the said correction equation or the said table. Control device for internal combustion engine. 3. The control device according to claim 1, wherein when the supply voltage is equal to or lower than a predetermined voltage, the control device corrects the increase by replacing the intake air amount or the fuel injection amount with a constant value. Control device for internal combustion engine.   The control device for an internal combustion engine according to claim 3, wherein the constant value is the intake air amount or the fuel injection amount immediately before the supply voltage becomes equal to or lower than the predetermined voltage. When the supply voltage is less than or equal to the predetermined voltage, the control device increases and corrects the intake air amount or the fuel injection amount based on the supply voltage and the rotational speed of the internal combustion engine. The control apparatus for an internal combustion engine according to claim 1 or 2. The control device estimates an intake air amount until the supply voltage becomes equal to or higher than the predetermined voltage after the supply voltage becomes equal to or lower than the predetermined voltage based on an intake air amount immediately after the supply voltage becomes equal to or higher than the predetermined voltage. The control device for an internal combustion engine according to any one of claims 1 to 5 , wherein the fuel injection amount is calculated based on an air amount. The control device determines whether the supply voltage is based on the intake air amount immediately before the supply voltage becomes equal to or lower than the predetermined voltage and the intake air amount immediately after the supply voltage becomes equal to or higher than the predetermined voltage. estimating the intake air amount from becoming less until the predetermined voltage or more, any one of the preceding claims, characterized in that for calculating the fuel injection amount based on the intake air amount and the estimated The control apparatus for an internal combustion engine according to the item. The control device for an internal combustion engine according to claim 6 or 7 , wherein the control device limits the fuel injection amount based on a change amount of the fuel injection amount.

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