JP2013036356A - Air flow rate sensor calibration device and air flow rate sensor calibration vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air flow rate sensor calibration device that allows calibration by off-road test run and achieves improvement in detection accuracy of the intake air quantity, and an air flow rate sensor calibration vehicle.SOLUTION: The air flow rate sensor calibration device 1 is detachably connected to an ECM 6 in order to control each part of a vehicle 2 via the ECM 6. The device includes: an EGR complete shut-off control part 8 for completely shutting off an EGR valve 7; a basic formula calculation part 9 which calculates the intake air quantity by a basic formula while using the manifold air pressure, the intake air temperature, and the engine speed as input variables; a volumetric efficiency correction calculation part 10 which corrects and calculates a variation by multiplying the value, calculated by the basic formula, by a correction term; and a calibrated value writing part 11 which learns a difference between the calculated value of the intake air quantity and a value detected by an MAF sensor 5 and writes the difference as the calibrated value in the ECM 6.

Description

  The present invention relates to an air flow rate sensor calibration device and an air flow rate sensor calibration vehicle that can be calibrated by a trial run on and off the road and can improve the detection accuracy of an intake air amount.

  The intake air amount is one of the important engine parameters for engine control. In order to detect the intake air amount, an air flow sensor (hereinafter referred to as MAF sensor) is installed in the intake pipe of the engine.

  As an example of engine control in which the intake air amount is important, control of an exhaust gas recirculation (EGR) and control of sulfur purge operation will be described.

  In EGR, exhaust gas is taken into the intake air at an appropriate ratio, so that combustion in the engine is blunted and nitrogen oxide (hereinafter referred to as NOx) emission is suppressed. However, if the EGR ratio is too high, the emission of particulate matter (Particulate Matter; hereinafter referred to as PM) increases even if NOx can be suppressed. Conversely, when the EGR ratio is low, PM emissions decrease but NOx emissions increase. That is, in EGR, NOx emission and PM emission are in a trade-off relationship. In the EGR control, the EGR ratio is controlled in a region where the NOx emission and the PM emission fall within specified values.

  At this time, since EGR control is performed based on the intake air amount, if there is a detection error in the MAF sensor, an EGR control error occurs. The EGR control error causes a NOx discharge error and a PM discharge error. Since the PM collection amount in a diesel particulate filter (hereinafter referred to as DPF) varies depending on the PM emission error, the DPF regeneration frequency is affected. When the DPF regeneration frequency varies, the fuel consumption varies. For example, if the same type of vehicle is expected to have the same fuel efficiency, if the detection value of the MAF sensor varies from vehicle to vehicle, a difference in fuel efficiency occurs. The only way to prevent this is to increase the detection accuracy of the MAF sensor.

  On the other hand, with the tightening of exhaust gas regulations, the EGR ratio region where the trade-off between NOx emission and PM emission is established tends to be narrowed. In order to accurately control the EGR ratio in such a narrow region, the importance of suppressing the detection error of the MAF sensor is increasing.

  The sulfur purge operation is performed in order to release sulfur components adhering to the catalyst of the NOx occlusion device (Lean NOx Trap; hereinafter referred to as LNT), and is necessary for vehicles equipped with the LNT that is being realized in recent years. Control. When the sulfur purge operation is performed, the fuel injection amount is increased, so that accurate air-fuel ratio control is required to avoid abnormal catalyst overheating and hydrogen sulfide discharge. In order to perform the air-fuel ratio control accurately, it is necessary to accurately detect the intake air amount, and the importance of suppressing the detection error of the MAF sensor is increasing.

JP 2010-116857 A

  By the way, the detection accuracy of the MAF sensor mounted on the vehicle changes due to the influence from the intake pipe, in addition to the detection accuracy of the MAF sensor alone. Specifically, the detection error of the MAF sensor alone is only about 2 to 3%. However, the detection accuracy of the MAF sensor mounted on the vehicle reaches a maximum of 10%. In addition, individual differences in detection error are large even in the same type of vehicle. There are many possible causes for the detection error in the on-board MAF sensor. For example, the air filter is contaminated, the air filter is attached incorrectly, the dimensional solid difference such as the diameter of the intake pipe from the MAF sensor to the engine, There are solid differences in the amount of thermal expansion. For this reason, the effect on the detection accuracy of the intake air amount in the vehicle brought about by the detection accuracy improvement of the MAF sensor alone is limited, and the detection accuracy of the entire apparatus with the MAF sensor attached to the intake pipe is low. There is a need to improve.

  In addition to the MAF sensor, a speed density method is known in which an engine parameter other than the intake air amount is used to obtain the intake air amount by calculation. The MAF sensor can be diagnosed and calibrated by comparing the value calculated by the speed density type calculation formula with the value detected by the MAF sensor. By calibrating the MAF sensor in this way, it can be expected to improve the detection accuracy of the MAF sensor.

  However, the present inventor has found that in the conventional speed density method, when a specific engine parameter fluctuates, the volume efficiency included in the arithmetic expression fluctuates, and the calculated intake air amount error fluctuates. I found it. Volumetric efficiency is the ratio between the capacity of a mechanical cylinder determined by the cross-sectional area of the cylinder and the piston stroke length and the amount of air actually taken into the cylinder, and has been conventionally considered to be a constant inherent to the engine. However, if the volumetric efficiency fluctuates due to fluctuations in engine parameters and the error in the calculated value of the intake air amount fluctuates, the accuracy of the calculated value decreases, and the calculated value cannot be used effectively for calibration of the MAF sensor.

  In addition, the speed density calculation formula cannot obtain an accurate intake air amount when the EGR valve is open. This arithmetic expression is an expression showing how much gas the engine has inhaled. If the EGR valve is closed and there is no gas return due to EGR, the amount of gas sucked by the engine is equal to the amount of air that has passed through the intake pipe in which the MAF sensor is installed. However, when the EGR valve is open, the gas returned from the exhaust manifold is also sucked into the engine, so that the amount of gas sucked by the engine and the amount of air passing through the intake pipe are not the same. Therefore, if the EGR valve is open, the calculation formula cannot obtain an accurate intake air amount.

  On the other hand, the inventor considers that the EGR valve is controlled to be fully closed and the MAF sensor is calibrated in a state where the calculated value indicates an accurate intake air amount. However, in some countries, from the viewpoint of NOx emission regulation, EGR full closure is legally regulated while traveling on the road. Under such legal restrictions, the MAF sensor cannot be calibrated with the calculated value of the intake air amount by controlling the EGR valve to be fully closed while traveling on the road.

  In vehicles equipped with an exhaust brake, when the exhaust brake is activated, the exhaust gas of the engine tries to return to the intake side without exiting to the exhaust side. The calculation formula of the method is not established. The exhaust brake does not operate if the exhaust brake switch is turned off, but if the exhaust brake switch is turned on, it operates when the foot brake is depressed. Therefore, although it is desirable to turn off the exhaust brake switch in an operation situation that does not require the exhaust brake, many drivers keep the exhaust brake switch on. For this reason, the exhaust brake frequently operates, and it becomes difficult to obtain an opportunity to calibrate the MAF sensor by obtaining the calculated value of the intake air amount.

  Therefore, an object of the present invention is to provide an air flow sensor calibration device and an air flow sensor calibration vehicle that can solve the above-described problems, enable calibration by trial operation outside the road, and improve the detection accuracy of the intake air amount. is there.

  In order to achieve the above object, an air flow sensor calibration device of the present invention is detachable from an engine control device mounted on a vehicle in order to calibrate an air flow sensor for detecting an intake air amount of an intake pipe of a vehicle engine. An air flow rate sensor calibration device that is connected to the vehicle and controls each part of the vehicle via the engine control device, wherein the EGR valve of the vehicle is fully closed so that only intake air that has passed through the intake pipe is drawn into the engine. When the EGR fully-closed control unit to be controlled and the EGR valve are fully closed, the volumetric efficiency measured in advance in the standard operation state with the engine intake pressure, intake air temperature, and engine speed as input variables. A basic formula calculation unit that calculates the intake air amount using a basic formula that is a constant, and an arithmetic value that is measured in advance in the standard operation state for the calculated value of the basic formula. A volumetric efficiency correction calculation unit that performs a correction calculation of the volumetric efficiency variation due to the engine parameter variation by multiplying a correction term based on the ratio between the engine parameter and the current engine parameter, and the calculation of the corrected intake air amount A calibration value writing unit that learns the difference between the value and the detected value of the intake air amount by the air flow rate sensor and writes it as a calibration value in the engine control device.

  A rotation speed sweep control unit that sweeps the rotation speed of the engine to a plurality of learning rotation speeds may be provided, and the calibration value writing unit may perform learning for each swept rotation speed.

  The air flow sensor calibration vehicle of the present invention is a vehicle equipped with an engine control device to which the air flow sensor calibration device is detachably connected, and stores the calibration value written by the calibration value writing unit. A value storage unit, and a calibration calculation unit that adds the calibration value to the detected value of the intake air amount by the air flow rate sensor to obtain the intake air amount.

  The present invention exhibits the following excellent effects.

  (1) Calibration by trial run outside the road becomes possible.

  (2) The detection accuracy of the intake air amount can be improved.

1 is a configuration diagram of an air flow sensor calibration device and an air flow sensor calibration vehicle according to an embodiment of the present invention. It is a graph of the intake air amount with respect to the engine speed before and after performing calibration according to the present invention. (A)-(d) is a rotation speed time change graph which shows the sweep pattern for sweeping an engine rotation speed to several learning rotation speed in this invention. It is a flowchart at the time of the trial run of the air flow sensor calibration apparatus and air flow sensor calibration vehicle of this invention. It is a block diagram of the air flow sensor calibration vehicle which shows other embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an air flow sensor calibration device 1 of the present invention is used when an air flow sensor calibration vehicle (hereinafter simply referred to as a vehicle) 2 of the present invention is trial run. Here, the trial run is a shipping inspection process of a production factory that produces the vehicle 2, a maintenance factory operated by a dealer, a maintenance factory operated by a transportation company, a maintenance factory operated by a fuel supplier or a repairer, a vehicle inspection factory, etc. Refers to the commissioning that takes place. The air flow sensor calibration device 1 is provided as a so-called service tool that is installed in such a maintenance factory and supports the trial operation of the vehicle 2. The air flow sensor calibration apparatus 1 includes a switch (not shown) that is operated by an operator to request learning start, and a display (not shown) that displays a learning condition deficiency factor and learning progress status described later. Is equipped.

  An air flow sensor calibration device 1 is an engine control module (ECM) 6 mounted on the vehicle 2 in order to calibrate the MAF sensor 5 that detects the intake air amount of the intake pipe 4 of the engine 3 of the vehicle 2. And an emulation function for controlling each part of the vehicle 2 via the ECM 6. The ECM 6 is also referred to as an electronic control unit (ECU). The ECM 6 has conventionally been provided with a connection terminal for connection to a service tool. By connecting this connection terminal to the air flow sensor calibration device 1, a command is sent between the air flow sensor calibration device 1 and the vehicle 2. And the air flow sensor calibration device 1 can control the entire vehicle 2 including the engine 3 via the ECM 6.

  The air flow sensor calibration device 1 includes an EGR full-close control unit 8 that fully controls the EGR valve 7 of the vehicle 2 so that only the intake air that has passed through the intake pipe 4 is drawn into the engine 3, and when the EGR valve 7 is fully closed. , A basic equation calculation unit 9 for calculating the intake air amount by a basic equation in which the intake air pressure, the intake air temperature, and the engine speed of the vehicle 2 are input variables, and the volume efficiency measured in advance in the reference operation state of the engine 3 is a constant. And the calculated value of the basic equation is multiplied by a correction term based on the ratio of the engine parameter measured in advance in the reference operation state of the engine 3 to the current engine parameter, and the volumetric efficiency variation due to the engine parameter variation A volumetric efficiency correction calculation unit 10 that corrects and calculates the difference between the calculated value of the intake air amount calculated by the correction and the detected value of the intake air amount by the MAF sensor 5; Includes a calibration value writing unit 11 to write to the emission control device 6 as a calibration value, the rotational speed sweep controller 12 to sweep the rotational speed of the engine to a plurality of learning speed. The calibration value writing unit 11 performs learning for each swept rotational speed.

  The vehicle 2 includes a calibration value storage unit 13 that stores the calibration value written by the calibration value writing unit 11 and a calibration calculation that adds the calibration value to the detected value of the intake air amount by the MAF sensor 5 to obtain the intake air amount. Part 14. The calibration value storage unit 13 and the calibration calculation unit 14 are mounted on the ECM 6.

  The vehicle 2 includes an intake pressure sensor 15 that detects intake pressure, an intake temperature sensor 16 that detects intake air temperature, a crank angle sensor 18 that detects the engine speed from the rotation of the crankshaft 17 of the engine 3, and cooling water. A cooling water temperature sensor 19 for detecting temperature, an exhaust pressure sensor 20 for detecting exhaust pressure, and an atmospheric pressure sensor 21 for detecting atmospheric pressure are provided.

  The vehicle 2 is provided with an air cleaner 22 for collecting dust on the most inlet side of the intake pipe 4. The MAF sensor 5 is located downstream of the air cleaner 22. A compressor 24 of a turbocharger 23 is connected to the intake pipe 4 downstream of the MAF sensor 5, and an intercooler 25 that cools intake air is connected downstream of the compressor 24. An intake throttle 26 is installed in the intake pipe 4 downstream of the intercooler 25, and the intake pipe 4 is connected to an intake manifold 27 of the engine 3 downstream of the intake throttle 26. An exhaust pipe 29 is connected to the exhaust manifold 28 of the engine 3, and a turbine 30 of the turbocharger 23 is provided in the exhaust pipe 29. An exhaust brake 31 is provided downstream of the turbine 30 in the exhaust pipe 29. A diesel particulate diffuser (Diesel Particulate Defuser; hereinafter referred to as DPD) 32 is provided downstream of the exhaust brake 31 to collect PM in the exhaust gas. The DPD 32 is also called a DPF. An EGR pipe 33 is provided between the exhaust manifold 28 and the intake manifold 27. The EGR pipe 33 is provided with an EGR cooler 34 and an EGR valve 7.

  The intake pressure sensor 15 and the intake temperature sensor 16 are installed in the intake manifold 27. The crank angle sensor 18 is installed facing the sensor gear attached to the crankshaft 17. The cooling water temperature sensor 19 is installed at an appropriate location of the cooling water circulation system of the engine 3, for example, a water jacket. The exhaust pressure sensor 20 is installed in the exhaust manifold 28.

  Next, the calculation formula (1) of the intake air amount executed by the basic formula calculation unit 9 and the volumetric efficiency correction calculation unit 10 of the air flow sensor calibration device 1 will be described. The calculation formula (1) for the intake air amount is composed of a basic formula and three correction terms. The basic formula is equivalent to the calculation formula in the conventionally known speed density method. The correction term is set independently for each engine parameter that causes fluctuations in volumetric efficiency, and any of the correction terms is a coefficient term (a term to be multiplied) with respect to the basic formula. In the present embodiment, intake air temperature, cooling water temperature, and intake-exhaust pressure ratio are used as engine parameters that cause fluctuations in volumetric efficiency. Accordingly, the three correction terms are an intake air temperature correction term, a cooling water temperature correction term, and an intake-exhaust pressure ratio correction term.

However,
Mair = intake air volume
Rair = Gas constant of air
TAIm = intake air temperature (intake manifold temperature)
PAIm = intake pressure (boost pressure, intake manifold pressure)
PA_A = atmospheric pressure
Vcyl = total displacement
Ne = engine speed η0 = reference volume efficiency 273 = value that converts Celsius temperature to absolute temperature 2 = number of intake strokes per revolution in four cylinders 60 = engine speed represented by rpm is converted per second value
TAIm0 = reference intake air temperature (reference intake manifold temperature)
m = intake air temperature correction multiplier
THW = Cooling water temperature
THW0 = standard cooling water temperature
a = Cooling water temperature correction multiplier
PETbI = Exhaust pressure (turbine inlet pressure)
PAIm0 = reference intake pressure (reference boost pressure, reference intake manifold pressure)
PETbI0 = reference exhaust pressure (reference turbine inlet pressure)
PA_A0 = Reference atmospheric pressure
n = pressure ratio correction multiplier.

  The gas constant Rair of air is a fixed value. The intake air temperature TAIm is detected by the intake air temperature sensor 16. Since the intake air temperature TAIm is detected in degrees Celsius, 273 is added to obtain the absolute temperature. The intake pressure PAIm is detected by the intake pressure sensor 15. The atmospheric pressure PA_A is detected by the atmospheric pressure sensor 21. Since the intake pressure PAIm is detected as a gauge pressure, it becomes an absolute pressure by adding the atmospheric pressure PA_A. The total displacement Vcyl is a value specific to the engine. The engine speed Ne is detected by the crank angle sensor 18.

  As described above, the basic equation uses the intake air temperature TAIm, the intake pressure PAIm, and the engine speed Ne as input variables, and the reference volume efficiency η0 as a constant.

  In the reference volume efficiency η0, the reference intake air temperature TAIm0, the reference cooling water temperature THW0, the reference intake air pressure PAIm0, the reference exhaust air pressure PETbI0, and the reference atmospheric pressure PA_A0, values obtained by measurement and calculation through experiments are set. As the intake air temperature correction multiplier m, the coolant temperature correction multiplier a, and the pressure ratio correction multiplier n, values obtained by calculation through experiments are set.

  The reference volumetric efficiency η0 is obtained by measuring the intake air amount Mair with a precisely calibrated measuring instrument in the reference operation state when the engine 3 is in a steady operation state (non-transient operation state). This is obtained by calculating back the basic equation from the air amount Mair, the intake air temperature TAIm, the intake air pressure PAIm, and the engine speed Ne. The reference intake air temperature TAIm0, the reference cooling water temperature THW0, the reference intake pressure PAIm0, the reference exhaust pressure PETbI0, and the reference atmospheric pressure PA_A0 are measured in the same operating state as when the reference volume efficiency η0 was obtained. These reference values are set in the map with the reference volume efficiency η0 and the fuel amount and the engine speed as reference axes.

  The intake air temperature correction multiplier m, the cooling water temperature correction multiplier a, and the pressure ratio correction multiplier n vary from the steady operation state of the engine 3 to one desired engine parameter among the intake air temperature, the cooling water temperature, and the intake to exhaust pressure ratio. When the operating state is changed, the intake air amount Mair is measured with a precisely calibrated measuring instrument, and the volume efficiency is obtained by calculating back the basic equation from the intake air amount Mair. It is estimated so that the variation in volumetric efficiency can be obtained. These correction multipliers are set in a map having the fuel amount and the engine speed as reference axes.

  Next, the effect of correcting and calculating the volumetric efficiency variation for the calculated value of the basic formula will be described.

  The reason why the volumetric efficiency fluctuates due to fluctuations in engine parameters is considered as follows.

  Considering the intake air temperature, the gas is sucked from the intake manifold 27 into each cylinder of the engine 3 via the intake port. Such an intake operation is repeatedly performed several tens of times per second according to the engine speed. At this time, the ease of inhalation of the gas is affected by the viscosity of the gas. Since the viscosity of the gas depends on the temperature, the viscosity of the gas varies depending on the intake air temperature, and the ease with which the gas is sucked into the cylinder varies. For this reason, the volumetric efficiency fluctuates due to fluctuations in the intake air temperature.

  Considering the cooling water temperature, the wall temperature of the cylinder and the intake manifold 27 is usually higher than the atmospheric temperature. Since the gas that has entered the cylinder from the intake pipe 4 via the intake manifold 27 is warmed by the wall and expands, the gas that is going to enter thereafter is obstructed. Depending on the wall temperature, the magnitude of the blockage to the gas entering the cylinder varies. The cooling water temperature reflects the wall temperature, and therefore, the volumetric efficiency fluctuates due to fluctuations in the cooling water temperature.

  Considering the intake to exhaust pressure ratio, the exhaust pipe 29 is provided with a post-processing device such as a DPD 31. Depending on the degree of clogging of the aftertreatment device, the amount of exhaust coming out of the cylinder varies. That is, if a large amount of collected matter is accumulated in the post-processing device, the exhaust resistance increases, so that there is a gas that does not come out of the cylinder. Such a phenomenon is called internal EGR. When internal EGR occurs, it becomes difficult for gas to enter the cylinder, and the volumetric efficiency fluctuates. The degree of internal EGR can be expressed by the ratio between the intake pressure and the exhaust pressure. That is, the volumetric efficiency fluctuates due to fluctuations in the intake to exhaust pressure ratio.

  According to the discussion so far, volumetric efficiency varies with any variation in intake air temperature, cooling water temperature, and intake to exhaust pressure ratio, and each is a separate event. In view of this, the present inventor considered performing a calculation using a basic equation that uses the volumetric efficiency (reference value) measured in the reference operating state, and correcting the calculated value for each of these engine parameters. The correction term is a term that becomes a coefficient with respect to the basic formula, and is based on the ratio of the engine parameter (reference value) measured in advance in the reference operation state to the current engine parameter (sensor value). The term represented by the ratio is greater than 1 if the sensor value that is the numerator is larger than the reference value that is the denominator, and less than 1 if the sensor value is smaller than the reference value. By taking the power of this ratio, the correction term can be matched to the volumetric efficiency variation. That is, the correction multiplier used for the power is approximated so that the measurement result at the time of experiment matches the calculation result.

  In the conventional speed density method, the volumetric efficiency is a fixed value regardless of the operating state of the engine 3, so that if the actual volumetric efficiency varies according to the operating state of the engine 3, the intake air amount is accurately calculated. On the other hand, according to the intake air amount calculation formula (1) of the present invention, a correction term for correcting the volumetric efficiency variation due to the engine parameter variation is added to the basic formula using the reference volumetric efficiency η0. Therefore, it is possible to cope with fluctuations in volumetric efficiency and to calculate the intake air amount with high accuracy. Further, since a correction term is provided for each engine parameter, it is possible to individually cope with variations in a plurality of engine parameters and to superimpose them.

  The present inventor conducted an experiment to compare the calculated value calculated by the calculation formula (1) of the intake air amount with the measured value of the intake air amount measured by a precisely calibrated measuring instrument while changing the engine parameter. As a result, a very favorable experimental result was obtained with an error within -0.5 to + 0.8%. From this experimental result, it was confirmed that the intake air amount calculation formula (1) can accurately calculate the intake air amount even if the intake air temperature, the cooling water temperature, and the intake-exhaust pressure ratio that affect the volume efficiency fluctuate.

  Next, the basic operation of the air flow sensor calibration device 1 according to the present invention will be described.

  The EGR fully-closed control unit 8 controls the EGR valve 7 to be fully closed via the ECM 6. As a result, only the intake air that has passed through the intake pipe 4 is drawn into the engine 3, and all of the gas sucked by the engine 3 is equal to the intake air detected by the MAF sensor 5. Thus, the detection error of the MAF sensor 5 can be evaluated.

  After the EGR valve 7 is fully closed, the basic equation calculation unit 9 and the volumetric efficiency correction calculation unit 10 calculate the calculation formula (1) to obtain the calculated value of the intake air amount. As already described, this calculated value is very accurate. Therefore, if the detected value of the intake air amount by the MAF sensor 5 has a deviation from the calculated value, the deviation can be regarded as an error of the MAF sensor 5. Therefore, the calibration value writing unit 11 learns the difference (deviation) between the calculated value of the intake air amount corrected by the calculation formula (1) and the detected value of the intake air amount by the MAF sensor 5, and this value. Is stored in the calibration value storage unit 13 of the vehicle 2 as a calibration value.

  Specifically, the MAF sensor 5 outputs an analog signal between 0 and 5 V, for example, and the digitally converted voltage value is taken into the ECM 6. In the ECM 6, a conversion table between the output voltage value of the MAF sensor 5 and the intake air amount is set, and the intake air amount is read from the voltage value. If a value for calibrating the voltage value referring to the conversion table is stored in the calibration value storage unit 13, the correct suction is performed by referring to the conversion table with the voltage value obtained by adding the calibration value to the output voltage value of the MAF sensor 5. Air volume is obtained. Alternatively, if the calibration value storage unit 13 stores a value for calibrating the intake air amount read from the conversion table, the correct intake air amount can be obtained by adding the calibration value to the intake air amount read from the conversion table. can get.

  FIG. 2 shows the result of an experiment for calibrating the MAF sensor 5. The measured values from a precisely calibrated measuring instrument are plotted with white circles. On the other hand, the detection values of the MAF sensor 5 are plotted with black squares, and it can be seen that the error is large over a wide region of the engine speed. On the other hand, the calculated values according to the calculation formula (1) of the present invention are plotted with black circles. The calculated value according to the calculation formula (1) of the present invention is almost the same as the measured value obtained by a precisely calibrated measuring instrument. Therefore, it can be seen that if the difference between the calculated value obtained by the calculation formula (1) of the present invention and the detected value of the MAF sensor 5 is learned and set as a calibration value, it is possible to calibrate the intake air amount with high accuracy. In general, an on-vehicle MAF sensor has an error of nearly 10%, but the error can be reduced to 1 to 2% by calibrating according to the present invention.

  If the variation of the error due to the engine speed is small, the calibration value may be a constant value that does not depend on the engine speed. If the calibration value depends on the engine speed, the calibration value may be set in a map referred to by the engine speed. For this purpose, the rotation speed sweep control unit 12 sweeps the rotation speed of the engine 3 to a plurality of learning rotation speeds via the ECM 6. The sweep pattern of the engine speed is shown in FIGS. 3 (a) to 3 (d).

  In the sweep pattern (step pattern A) of FIG. 3A, the engine speed is first controlled to the highest learning speed. Thereafter, when the overshoot of the detected engine speed is settled and the engine speed is stabilized, the difference between the calculated value obtained by the calculation formula (1) of the present invention and the detected value of the MAF sensor 5 is learned. Next, the engine speed is controlled to a learning speed that is lower by one segment, and learning is performed when the detected engine speed is stabilized at the learning speed. In the same manner, learning is performed by decreasing the engine speed by one segment. When the learning is completed up to the minimum learning rotational speed, the sweep is finished.

  In the sweep pattern (step pattern B) of FIG. 3B, the engine speed is first controlled to the lowest learning speed. Thereafter, when the overshoot of the detected engine speed is settled and the engine speed is stabilized, the difference between the calculated value obtained by the calculation formula (1) of the present invention and the detected value of the MAF sensor 5 is learned. Next, the engine speed is controlled to a higher learning speed by one division, and learning is performed when the detected engine speed is stabilized at the learning speed. In the same manner, the engine speed is increased by one segment and learning is performed. When the learning is completed up to the maximum learning speed, the sweep is finished.

  In the sweep pattern (ramp pattern) in FIG. 3C, the engine speed is first controlled to be lower than the lowest learning speed. From this state, the engine speed is continuously increased, and the engine is swept up to the maximum learning speed. In the meantime, every time the engine speed reaches a predetermined number of learning rotational speeds (indicated by black dots), the difference between the calculated value according to the calculation formula (1) of the present invention and the detected value of the MAF sensor 5 is learned. In the ramp pattern, the gradient that increases the rotation speed (rotation speed sweep speed) is relatively stable considering the engine inertia, the error tendency of the rotation speed control, the time required for the sweep pattern, the required accuracy of the calibration value, etc. It is preferable to set the gradient so that learning can be performed in a simple state and learning can be performed at a necessary separation interval.

  As in the sweep pattern of FIG. 3D, a ramp-like pattern that sweeps from a high engine speed to a low engine speed is also possible, contrary to FIG. 3C.

  Next, the detailed operation of the air flow sensor calibration device 1 according to the present invention will be described with reference to the flowchart of FIG.

  For example, it is assumed that the vehicle 2 is brought into a maintenance factory operated by a dealer and the air flow sensor calibration device 1 is connected to the ECM 6. The worker turns on an ignition key (not shown) of the vehicle 2 and starts a trial run.

  In step S1, the air flow sensor calibration device 1 determines whether or not the ignition key of the vehicle 2 is turned on. If NO, the process returns to step S1. If YES, the engine 3 is started and the process proceeds to step S2. Here, the engine 3 is assumed to be a no-load free accelerator operation (also called racing). The no-load free accelerator operation is a so-called idling operation in which the transmission 3 is neutral and the engine 3 is operated at an arbitrary engine speed. Thus, the trial run is performed with a no-load free accelerator operation. However, the engine is idling immediately after the engine is started.

  In step S2, the air flow sensor calibration device 1 determines whether or not the engine 3 of the vehicle 2 has been started. If NO, the process returns to step S2. If YES, the process proceeds to step S3.

  In step S <b> 3, the air flow sensor calibration device 1 determines whether there is a learning start request from an operator. If NO, the process returns to step S3. If YES, the process proceeds to step S4. However, if there is an intake-exhaust pressure ratio correction term in the arithmetic expression (1), the process can proceed to step S5.

  Step S4 is a procedure executed when there is no intake-exhaust pressure ratio correction term in the arithmetic expression (1). That is, in step S4, the air flow rate sensor calibration device 1 determines the DPD regeneration start requirement. The DPD regeneration requirement is determined, for example, when the inlet / outlet pressure difference of the DPD 32 exceeds the start threshold value. When DPD regeneration is necessary, the air flow rate sensor calibration device 1 determines DPD regeneration completion requirements after starting DPD regeneration. The requirement for completion of DPD regeneration is determined, for example, when the inlet / outlet pressure difference of the DPD 32 falls below the end threshold. When the DPD playback is completed or when the DPD playback is unnecessary, the process proceeds to step S5. By executing step S4, the volumetric efficiency variation factor due to the internal EGR is eliminated, so that the intake air amount can be accurately calculated even if there is no intake-exhaust pressure ratio correction term in the equation (1). .

  In step S5, the EGR fully-closed control unit 8 of the air flow rate sensor calibration device 1 controls the EGR valve 7 to be fully closed.

In step S6, the air flow rate sensor calibration device 1 determines whether the learning condition is satisfied. Learning conditions include
(1) Foot brake operating state (2) Battery voltage (3) Cooling water temperature (4) Intake air temperature (5) Side brake operating state (6) Vehicle speed 0 km / h
(7) EGR valve fully closed.

  During the trial operation, the vehicle 2 is in a stopped state, but the foot brake may be operated from the viewpoint of safety (this condition is not essential). If the battery voltage drops below the rated voltage, many sensors including the MAF sensor 5 do not operate normally. Therefore, the condition is that the battery voltage is equal to or higher than the rated voltage. If the cooling water temperature and the intake air temperature are abnormal values, the intake air amount cannot be calculated correctly. Therefore, the condition is that the coolant temperature and the intake air temperature are normal values. Side brakes (not shown) are necessary to ensure stopping. Therefore, the condition is that the side brake is operating. The vehicle speed of 0 km / h is confirmation that the vehicle 2 is actually stopped. Therefore, the condition is that the vehicle speed is 0 km / h. The EGR valve fully closed is confirmation that the EGR valve is actually fully closed. Therefore, the condition is that a valve opening sensor (not shown) indicates full close.

  If even one of these learning conditions is not satisfied, the determination is no and the process proceeds to step S7.

  In step S <b> 7, the air flow sensor calibration device 1 displays the item causing the insufficient learning condition on the display, and prompts the worker to start over.

  If the determination in step S6 is YES, the learning condition is satisfied, and the process proceeds to step S8.

  In step S8, the rotational speed sweep control unit 12 starts sweeping the engine rotational speed in accordance with the sweep pattern.

  In step S9, when the engine speed reaches the learning speed and stabilizes, the basic formula calculation unit 9 and the volumetric efficiency correction calculation unit 10 obtain a calculated value of the intake air amount.

  In step S <b> 10, the calibration value writing unit 11 learns the difference between the calculated value of the intake air amount and the detection value of the MAF sensor 5 and stores it in the calibration value storage unit 13 of the vehicle 2 as a calibration value.

  In step S11, the rotational speed sweep control unit 12 determines whether or not the engine rotational speed has been swept to all the learned rotational speeds. If NO, the process returns to step S9. If YES, the process proceeds to step S12.

  In step S12, the air flow rate sensor calibration device 1 returns the engine 3 to the idle operation and displays learning completion on the display to prompt the end of the trial operation. The test run ends when the worker turns off the ignition key.

  Thereafter, while the vehicle 2 is traveling on the road, the calibration calculation unit 14 adds the calibration value read from the calibration value storage unit 13 to the detected value of the intake air amount by the MAF sensor 5 to obtain the intake air amount.

  As described above, according to the present invention, the EGR full-close control unit 8 that performs full-close control of the EGR valve 7 in the air flow sensor calibration device 1 that is detachably attached to the ECM 6, and the basic formula for calculating the basic equation and the correction term. Since the equation calculation unit 9 and the volumetric efficiency correction calculation unit 10 and the calibration value writing unit 11 for writing the calibration value to the ECM 6 are provided, the vehicle 2 is trial run at the maintenance shop where the air flow sensor calibration device 1 is installed, and EGR The calibration value can be calculated with the valve 7 fully closed. Since the trial operation is performed at a maintenance shop, not on the road, even if the EGR valve 7 is fully closed, there is no conflict with the laws and regulations. Exhaust gas discharged from the vehicle 2 during the trial operation can be prevented from being released into the atmosphere by purifying it with the purification facility of the maintenance shop.

  According to the present invention, since the calibration value can be updated by the air flow sensor calibration device 1 at the time of periodic inspection or vehicle inspection of the vehicle 2, no special work relating to calibration of the MAF sensor 5 occurs for the driver. .

  According to the present invention, the air flow sensor calibration device 1 obtains all the engine parameters necessary for the calculation of the intake air amount, such as the intake air temperature, the intake air pressure, and the engine speed, from the sensor mounted on the vehicle 2, The air flow sensor calibration device 1 does not require a special sensor. The air flow rate sensor calibration apparatus 1 can be configured only by adding software to a conventional service tool. Therefore, the air flow sensor calibration device 1 can be realized at low cost.

  According to the present invention, the vehicle 2 is calibrated by performing a trial run at the maintenance shop where the air flow sensor calibration device 1 is installed. Unlike the road running, the vehicle speed is 0 km / h during the trial run. Therefore, the exhaust brake does not operate. Therefore, even if the driver brings the vehicle 2 into the maintenance shop with the exhaust brake switch turned on, it is possible to avoid the exhaust brake from being operated, and the erroneous calculation value of the intake air amount due to the operation of the exhaust brake can be learned. Never used.

  According to the present invention, since a complicated calculation program such as the basic equation calculation unit 9 and the volumetric efficiency correction calculation unit 10 may be installed in the air flow sensor calibration device 1, the load on the ECM 6 can be reduced.

  According to the present invention, the volume efficiency variation is corrected and calculated by the correction term for correcting the volume efficiency variation due to the engine parameter variation, so that the accuracy of the intake air amount calculation is improved. As a result, the MAF sensor 5 is accurately calibrated, and the MAF sensor 5 can detect the intake air amount with high accuracy required for EGR control and sulfur purge operation.

  Next, another embodiment of the present invention will be described.

  In the above-described embodiment, each of the units 8 to 12 is mounted on the air flow rate sensor calibration device 1 installed in the maintenance shop, and only the calibration value storage unit 13 and the calibration calculation unit 14 are mounted on the vehicle 2. The functions 8 to 12 may be realized in the vehicle 2.

  As shown in FIG. 5, an air flow rate sensor calibration vehicle (hereinafter simply referred to as a vehicle) 50 according to the present invention controls the EGR valve 7 to be fully closed so that only intake air that has passed through the intake pipe 4 is drawn into the engine 3. When the EGR fully-closed control unit 51 and the EGR valve 7 are fully closed, the intake air pressure, the intake air temperature, and the engine speed are input variables, and the volume efficiency measured in advance in the reference operation state of the engine 3 is a constant. A basic equation calculation unit 52 for calculating the intake air amount by an equation, and a correction term based on a ratio between an engine parameter measured in advance in the reference operation state of the engine 3 and the current engine parameter as a calculated value of the basic equation And the volumetric efficiency correction calculation unit 53 for correcting and calculating the volumetric efficiency variation due to the variation of the engine parameter, the calculated value of the intake air amount corrected and the air flow A calibration value storage unit 54 that learns a difference from the detected value of the intake air amount by the sensor and stores it as a calibration value, and a calibration that adds the calibration value to the detected value of the intake air amount by the air flow sensor 5 to obtain the intake air amount. A calculation unit 55 and a rotation speed sweep control unit 56 that sweeps the rotation speed of the engine 3 to a plurality of learning rotation speeds are provided.

  All the parts 51 to 56 are mounted on the ECM 6 of the vehicle 50. However, if the ECM 6 is not equipped with a power operation instruction as a basic operation instruction, an approximate expression or a map is stored in the ECM 6 for the power operation. The operations of the respective parts 51 to 56 are substantially the same as those of the above-described embodiment, and the detailed operation at the time of the trial run is similar to that in FIG.

  In the vehicle 50, since all the control functions related to the calibration of the MAF sensor 5 are mounted on the ECM 6, no special member is required for the service tool 57 of the maintenance shop. However, it is preferable that the service tool 57 instructs the ECM 6 to start learning by an operator so that the EGR valve fully closed control is not performed in an inappropriate place such as on the road.

1 Air flow sensor calibration device 2 Air flow sensor calibration vehicle (vehicle)
3 Engine 4 Intake pipe 5 Air flow sensor (MAF sensor)
6 Engine control unit (ECM)
7 EGR Valve 8 EGR Fully Closed Control Unit 9 Basic Equation Calculation Unit 10 Volume Efficiency Correction Calculation Unit 11 Calibration Value Writing Unit 12 Speed Sweep Control Unit 13 Calibration Value Storage Unit 14 Calibration Calculation Unit

Claims (3)

In order to calibrate an air flow sensor for detecting an intake air amount of an intake pipe of an engine of a vehicle, it is detachably connected to an engine control device mounted on the vehicle and controls each part of the vehicle via the engine control device An air flow sensor calibration device
An EGR fully-closed control unit that fully-closes an EGR valve of the vehicle so that only intake air that has passed through the intake pipe is drawn into the engine;
When the EGR valve is fully closed, the intake air amount is obtained by the basic equation using the vehicle intake pressure, the intake air temperature, and the engine speed as input variables, and the volume efficiency measured in advance in the reference operation state of the engine as a constant. A basic expression calculation unit for calculating
The calculated value of the basic formula is multiplied by a correction term based on the ratio of the engine parameter measured in advance in the standard operating state of the engine to the current engine parameter, and the volume efficiency variation due to the variation of the engine parameter. A volumetric efficiency correction calculation unit for correcting and calculating
A calibration value writing unit that learns the difference between the calculated value of the intake air amount that has been corrected and the detected value of the intake air amount by the air flow sensor and writes the difference to the engine control device as a calibration value; Air flow sensor calibration device. A rotational speed sweep control unit for sweeping the rotational speed of the engine to a plurality of learning rotational speeds;
The air flow rate sensor calibration device according to claim 1, wherein the calibration value writing unit performs learning for each swept rotational speed. A vehicle equipped with an engine control device to which the air flow sensor calibration device according to claim 1 is detachably connected,
A calibration value storage unit for storing the calibration value written by the calibration value writing unit;
An air flow rate sensor calibration vehicle comprising: a calibration calculation unit that adds a calibration value to a detected value of the intake air amount by the air flow rate sensor to obtain an intake air amount.