JP5250678B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, for example, an internal combustion engine control apparatus that performs air-fuel ratio correction related to purging of fuel evaporative gas in a fuel evaporative gas adsorbing means.

  As a fuel evaporative gas adsorbing means for adsorbing and storing fuel evaporative gas generated in an in-vehicle fuel tank in order to prevent air pollution, a vehicle such as an automobile using an internal combustion engine (hereinafter sometimes referred to as an engine) as a prime mover, It has a canister tank such as a charcoal canister. The fuel evaporative gas adsorbed by the canister tank is discharged and purged into the intake passage of the engine under flow control by a purge control valve (canister purge control valve). Such control is referred to as canister purge control.

  As an air-fuel ratio control device for an engine in which the fuel evaporative gas divergence control is performed, the purge amount of the fuel evaporative gas from the canister tank is estimated based on the intake pipe negative pressure, the engine speed, and the opening of the purge control valve. The amount of fluctuation in the air-fuel ratio due to the fuel evaporative gas purge is estimated, and during the purge execution, the fuel supply amount is corrected based on the estimated value of the air-fuel ratio fluctuation amount, and the correction coefficient based on the air-fuel ratio detected by the air-fuel ratio sensor (For example, Patent Document 1).

JP 10-141114 A

  The adsorption amount (charge amount) of the fuel evaporative gas in the canister tank is to change according to the state of the vehicle and the state of the engine. If the fuel evaporative gas charge amount in the canister tank is different, a difference in concentration occurs in the purged fuel evaporative gas, and even if the purge control valve has the same opening, there is a difference in the air-fuel ratio fluctuation amount due to purging of the fuel evaporative gas. Will occur.

  When the difference in the air-fuel ratio fluctuation amount is small, there is no problem in the convergence to the target air-fuel ratio by the air-fuel ratio feedback compensation control. However, when the difference is large, the convergence to the target air-fuel ratio is delayed and the emission performance is reduced. It will get worse.

  The present invention has been made in view of the above problems, and the object of the present invention is to achieve convergence to the target air-fuel ratio by air-fuel ratio feedback compensation control regardless of the difference in the amount of fuel evaporative gas charged in the canister tank. It is an object of the present invention to provide a control device for an internal combustion engine that is promptly performed and does not cause deterioration in emission performance.

  In order to achieve the above object, a control apparatus for an internal combustion engine according to the present invention includes a fuel evaporative gas adsorbing means for adsorbing a fuel evaporative gas in a fuel tank, and a purge control valve whose opening degree can be adjusted midway. The fuel evaporative gas purge means for purging the fuel evaporative gas adsorbed by the adsorption means to the intake passage of the internal combustion engine, and the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the air-fuel ratio detected by the air-fuel ratio detection means A control device for an internal combustion engine having a fuel correction means for feedback compensation to the fuel ratio, wherein the purge control valve opening control means performs control for opening the purge control valve under a predetermined condition; and under the predetermined condition While the purge control valve is open, the fuel correction value of the fuel correction means is calculated while the fuel correction means is performing a fuel correction calculation for realizing a predetermined air-fuel ratio. A purge amount calculating means for obtaining a purge amount of the fuel evaporative gas, and a charge for obtaining a charge amount of the fuel evaporative gas adsorbed on the fuel evaporative gas adsorbing means from the purge amount of the fuel evaporative gas obtained by the purge amount calculating means An amount estimating means; a charge amount increase / decrease calculating means for increasing / decreasing the charge amount of the fuel evaporative gas determined by the charge amount estimating means according to the state of the internal combustion engine and the vehicle; Charge amount correction means for correcting an increase / decrease calculation value of the charge amount increase / decrease calculation means, and fuel correction value calculation means for calculating a fuel correction value based on the charge amount increase / decrease calculated by the charge amount increase / decrease calculation means.

  In the control apparatus for an internal combustion engine according to the present invention, preferably, the fuel correction means includes a target air-fuel ratio setting means for obtaining a target air-fuel ratio according to the state of the internal combustion engine, and an air-fuel ratio detected by the air-fuel ratio detection means. An air-fuel ratio feedback control coefficient calculating means for calculating an air-fuel ratio feedback control coefficient for performing PID control from a difference from the target air-fuel ratio set by the target air-fuel ratio setting means, and the fuel correcting means under the predetermined condition From this, the PID control gain is changed while the purge amount of the fuel evaporative gas is obtained.

  In the control apparatus for an internal combustion engine according to the present invention, preferably, the fuel correction means includes a target air-fuel ratio setting means for obtaining a target air-fuel ratio according to the state of the internal combustion engine, and an air-fuel ratio detected by the air-fuel ratio detection means. An air-fuel ratio feedback control coefficient calculating means for calculating an air-fuel ratio feedback control coefficient for performing PID control from a difference from the target air-fuel ratio set by the target air-fuel ratio setting means; and a response for setting a response delay of the air-fuel ratio detecting means Based on the delay setting means and the response delay set by the response delay setting means, the true air-fuel ratio is calculated from the detected value of the air-fuel ratio by the air-fuel ratio detecting means, and the fuel correction value is calculated from the calculated true air-fuel ratio. An air-fuel ratio pre-correction correction part calculation unit for determining the fuel, and corrects the fuel with a fuel correction value by the PID control and the air-fuel ratio pre-correction correction part calculation part.

  In the control apparatus for an internal combustion engine according to the present invention, preferably, the purge control valve opening control means is different from a purge amount calculation means for setting a predetermined fuel evaporative gas flow rate under the predetermined conditions, and a front-rear pressure of the valve. Differential pressure correction value calculation means for calculating a pressure correction value, and configured to correct the valve opening of the purge control valve with the differential pressure correction value to realize the predetermined fuel evaporative gas flow rate. ing.

  In the control apparatus for an internal combustion engine according to the present invention, preferably, the charge amount increase / decrease calculating means includes time constant determining means for determining a time constant that decreases in accordance with the fuel evaporative gas flow rate, and the time constant determining means With the determined time constant, the amount of fuel evaporative gas that evaporates from the fuel tank per unit time is obtained, and the calculation for increasing or decreasing the charge amount is performed.

  In the control apparatus for an internal combustion engine according to the present invention, preferably, the charge amount increase / decrease calculating means calculates the amount of fuel evaporative gas that evaporates from the fuel tank per unit time in accordance with the intake air temperature, vehicle speed, idle, and auxiliary load conditions. The calculation is performed to increase or decrease the charge amount.

  The control apparatus for an internal combustion engine according to the present invention preferably holds a value when the purge control valve is in a closed state as a result of the charge amount increase / decrease calculation means obtaining an increase / decrease in the adsorbed fuel evaporative gas, A value obtained by adding the fuel evaporative gas from the fuel tank corresponding to the state of the internal combustion engine and the vehicle to the held value and adding the fuel evaporative gas from the fuel tank when the purge control valve is opened again. Is set as an initial value, and the fuel correction value based on the charge amount increase / decrease is set.

  The control apparatus for an internal combustion engine according to the present invention preferably realizes a desired air-fuel ratio from the air-fuel ratio detected by the air-fuel ratio detection means in a state where the purge control valve is open with respect to the charge amount estimation means. And a means for obtaining a variable state of the fuel correcting means and a means for obtaining a predetermined interval, and the amount adsorbed by the state of the variable is corrected at every predetermined interval.

  In the control apparatus for an internal combustion engine according to the present invention, preferably, the state of the variable of the fuel correction means for realizing a desired air-fuel ratio from the air-fuel ratio detected by the air-fuel ratio detection means is an average of I of the air-fuel ratio PID control. Value.

  According to the control device for an internal combustion engine according to the present invention, the charge amount of the fuel evaporative gas in the canister tank is detected and the air-fuel ratio correction is performed according to the charge amount. Therefore, regardless of the difference in the charge amount of the fuel evaporative gas in the canister tank. Therefore, the air-fuel ratio fluctuation at the time of purging is suppressed and the convergence to the target air-fuel ratio by the air-fuel ratio feedback compensation control is promptly performed, and the emission performance is not deteriorated. Furthermore, when the charge amount is estimated, the air-fuel ratio fluctuation can also be suppressed by changing the gain of the air-fuel ratio feedback or performing the air-fuel ratio pre-correction.

The block diagram which shows one Embodiment of the internal combustion engine for motor vehicles which performs canister purge control by this invention. The block diagram which shows one Embodiment of the engine control system which performs canister purge control by this invention. 1 is a block diagram showing an embodiment of an engine control device for an internal combustion engine for an automobile that performs canister purge control according to the present invention. The block diagram which shows one Embodiment of the canister purge control means of the control apparatus in this embodiment. The block diagram which shows the detailed example of the starting condition determination part of this embodiment. The block diagram which shows the detailed example of the purge flow rate determination part of this embodiment. The block diagram which shows the detailed example of the charge amount estimation part of this embodiment. The block diagram which shows the detailed example of the relationship between the air fuel ratio prefetch correction | amendment part of this embodiment, and air fuel ratio PID control (air fuel ratio feedback control). The block diagram which shows the detailed example of the air-fuel ratio PID control when not using the air-fuel ratio pre-correction correction part of this embodiment. The block diagram which shows the detailed example of the charge amount increase / decrease calculation part of this embodiment. The block diagram which shows the detailed example of the fuel evaporation amount calculation part of this embodiment. The figure which shows an example of the determination of the charge amount estimation permission flag of this embodiment. An example of a block diagram showing a detailed example of an air-fuel ratio correction coefficient calculation unit of the present embodiment. The time chart which shows the behavior of each control variable of the engine control apparatus which performs canister purge control of this embodiment. The time chart which shows the behavior of each variable of the canister tank charge CPCSUMHLD correction calculation of this embodiment. The flowchart which shows the routine of the engine control apparatus by this embodiment. The flowchart which shows the routine of the canister purge control means by this embodiment. The flowchart which shows the routine of the starting condition determination part by this embodiment. The flowchart which shows the routine of the purge flow rate determination part by this embodiment. The flowchart which shows the routine of the charge amount estimation part by this embodiment. 7 is a flowchart showing a routine of an air-fuel ratio pre-correction correction unit and air-fuel ratio PID control (air-fuel ratio feedback control) according to the present embodiment. 7 is a flowchart showing a routine of air-fuel ratio PID control when the air-fuel ratio pre-correction correction amount is not used according to the present embodiment. The flowchart which shows the routine of the charge amount increase / decrease calculation part by this embodiment. The flowchart which shows the routine of the fuel vapor quantity calculation part of this embodiment. The flowchart which shows the routine of the air fuel ratio correction coefficient calculation part of this embodiment.

An embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of an internal combustion engine (engine) for an automobile that performs canister purge control.

  In FIG. 1, an engine 201 bypasses the intake air system with a thermal air flow meter 202 that measures the amount of intake air, a throttle throttle valve 203 that adjusts the air flow rate sucked by the engine 201, and the throttle throttle valve 203. An idle speed control (ISC) valve 204 that controls the flow passage area of the flow passage connected to the intake pipe 205 and controls the number of revolutions of the engine 201 during idling, and a pressure in the intake pipe that is installed in the intake pipe 205. It has an intake pipe pressure sensor 206 to detect, and a fuel injection valve 207 for each cylinder that injects and supplies the fuel required by the engine 201.

  The engine 201 is supplied with ignition energy based on an ignition signal of the engine control device 250 and an ignition plug 209 of each cylinder for igniting an air-fuel mixture supplied into the cylinder (combustion chamber) 208. A cylinder ignition coil (ignition module) 210 is provided.

  The engine 201 is provided with a cam angle sensor 211 that detects a cam angle and a water temperature sensor 212 that detects a cooling water temperature.

  A catalyst 214 is connected to the exhaust pipe 213. An air-fuel ratio sensor (LAF sensor) 215 that outputs a linear electrical signal proportional to the oxygen concentration in the exhaust gas is disposed upstream of the catalyst 214 as viewed in the exhaust gas flow.

  The engine 201 is, for example, a gasoline engine, and fuel that is pumped up by a fuel pump 221 from a fuel tank 220 that stores gasoline as fuel and is regulated to a predetermined fuel pressure by a pressure regulating means 222 is fuel injection valve 207. To be supplied.

  A canister tank 230 is connected to the fuel tank 220 as fuel evaporative gas adsorbing means for adsorbing and holding the fuel evaporative gas generated in the fuel tank 220 with charcoal or the like. The canister tank 230 is connected to the intake pipe 205 by a purge passage 232 including a purge control valve 231 that can be adjusted in opening degree, that is, the flow rate can be variably controlled.

  The engine 201 is operated and stopped by an ignition key switch 216 that is a main switch. Fuel control including air-fuel ratio control of the engine 201, idle control, ignition timing control, and evaporation purge control are performed by the engine control device 250.

  In this embodiment, the idling speed of the engine 201 is controlled by the idle speed control valve 204. However, when the opening of the throttle throttle valve 203 is controlled by a motor or the like, the throttle throttle valve 203 Since the idling speed can be controlled, the idle speed control valve 204 becomes unnecessary.

  The engine control device 250 is of an electronic control type by a microcomputer, and details thereof are shown in FIG. The engine control device 250 converts an electrical signal of each sensor installed in the engine 201 into a signal for digital calculation processing inside the CPU 301, and converts a control signal for digital calculation into an actual actuator drive signal. It is set in the I / O unit 302. The I / O unit 302 includes a water temperature sensor 212, a crank angle sensor 219, a cam angle sensor 211, an air-fuel ratio sensor 215, an intake air amount sensor (thermal air flow meter) 202, a throttle opening sensor 217, a vehicle speed sensor 241, An ignition switch 216, an intake pipe pressure sensor 206, an atmospheric pressure sensor 243, an intake air temperature sensor 218, and an auxiliary load switch (air conditioner switch) 242 are connected.

  The CPU 301 is connected to a driver 303 for the fuel injection valve 207, ignition coil 210, idle speed control valve 204, and purge control valve 231, and an output signal is sent from the CPU 301 to each actuator via the driver 303. .

  Next, one embodiment of the control block of the engine control apparatus 250 according to the present embodiment will be described with reference to FIG.

  The engine control apparatus 250 executes a computer program to execute engine speed calculation means 101, basic fuel calculation means 102, basic fuel correction coefficient calculation means 103, basic ignition timing calculation means 104, ISC control means 105, canister purge control. The means 106, the air-fuel ratio feedback control coefficient calculation means 107, the target air-fuel ratio setting means 108, the basic fuel correction means 109, and the ignition timing correction means 110 are embodied in software.

  The engine speed calculation means 101 counts the electric signal of the crank angle sensor 219 set at a predetermined crank angle position of the engine 201, mainly the number of inputs per unit time of the pulse signal change, and performs arithmetic processing. The number of revolutions per unit time of the engine 201 is calculated.

  The basic fuel calculation means 102 is based on the engine speed calculated by the engine speed calculation means 101 and the intake air flow rate measured by the thermal air flow meter 202 or the intake pipe pressure detected by the intake pipe pressure sensor 206. The basic fuel amount required by the engine 201 in each operation region is calculated. Since the intake air flow rate and intake pipe pressure represent engine loads, the intake air flow rate and intake pipe pressure are collectively referred to as engine loads.

  The basic fuel correction coefficient calculation means 103 calculates a correction coefficient for each operating region of the engine 201 for the basic fuel amount from a map of engine speed and engine load.

  The basic ignition timing calculation means 104 determines the optimal ignition timing for each operating region from the map of engine speed and engine load.

  The ISC control means 105 sets a target rotational speed at idling in order to keep the idling rotational speed of the engine 201 at a predetermined value from the engine load and water temperature sensor 212, and outputs an ISC valve signal based on the target air flow rate to the ISC valve 203. .

  As a result, the ISC valve 203 is driven so as to achieve the target air flow rate during idling, and the idling speed is set to the target speed under the air amount control by the ISC valve 203.

  The canister purge control means 106 includes a thermal air flow meter 202 or an intake pipe pressure sensor 206, a throttle opening sensor 217, a vehicle speed sensor 241, an intake air temperature sensor 218, auxiliary load switch 242 signals, and air-fuel ratio feedback control described later. The signal of the air-fuel ratio feedback control coefficient output by the coefficient calculation means 107 is input, and based on the intake air temperature, engine load, engine speed, vehicle speed, auxiliary machine load state, idle determination value based on throttle opening, and air-fuel ratio feedback control coefficient Then, the purge amount calculation of the fuel vapor gas (evaporation) from the canister tank 230, the charge amount estimation of the fuel vapor gas in the canister tank 230, and the fuel correction amount at the time of evaporation purge are calculated.

  The canister purge control means 106 outputs a signal for driving the purge control valve 231 with the calculated evaporation purge amount as a target flow rate.

  Thereby, the opening degree of the purge control valve 231 is adjusted so that the evaporation purge amount becomes the target flow rate, and the evaporation purge is performed at the target flow rate.

  The air-fuel ratio feedback control coefficient calculation means 107 calculates an air-fuel ratio feedback control coefficient from the difference between the output of the air-fuel ratio sensor 215 and a target air-fuel ratio described later.

  The target air-fuel ratio setting means 108 determines the target air-fuel ratio (target air-fuel ratio) of the engine 201 from the map of the engine speed and the engine load.

  The basic fuel correction means 109 is the basic fuel calculated by the basic fuel calculation means 102, the correction coefficient of the basic fuel correction coefficient calculation means 103, the air / fuel ratio feedback control coefficient of the air / fuel ratio feedback control coefficient calculation means 107, the engine water temperature. Is corrected by the fuel correction amount at the time of evaporation purge calculated by the canister purge control means 106, and a fuel injection command signal based on the corrected fuel amount is output to the fuel injection valve 207 of each cylinder. Thereby, the fuel injection valve 207 of each cylinder injects and supplies the corrected amount of fuel to each cylinder.

  The ignition timing correction means 110 corrects the correction amount based on the engine water temperature with respect to the basic ignition timing determined by the basic ignition timing calculation means 104, and outputs the corrected ignition timing command signal to the ignition coil 210 of each cylinder. To do.

  As a result, the spark plug 209 of each cylinder sparks at a required ignition timing, and the air-fuel mixture flowing into the cylinder 208 is ignited.

FIG. 4 shows an overall block diagram of the canister purge control means 106.
The canister purge control means 106 includes an activation condition determination unit 401 that determines an activation condition, a purge amount calculation unit 402 that calculates a target purge flow rate, a charge amount estimation unit 403 that estimates an evaporation charge amount of the canister tank 230, The air-fuel ratio pre-correction correction unit 404, the charge amount decay time constant calculation unit 406, the evaporated fuel amount calculation unit 407, the charge amount increase / decrease calculation unit 408, the air-fuel ratio correction coefficient calculation unit 409, and the charge amount correction calculation unit 410 including.

  The air-fuel ratio pre-correction correction unit 404 calculates an air-fuel ratio pre-correction correction coefficient from the actual air-fuel ratio measured by the air-fuel ratio sensor 215. The air-fuel ratio pre-correction correction coefficient is added to the air-fuel ratio correction coefficient (the air-fuel ratio feedback control coefficient of the air-fuel ratio feedback control coefficient calculation means 107) by the adder 405 and is input to the charge amount estimation unit 403.

  The charge amount decay time constant calculation unit 406 calculates a time constant by which the evaporation charge amount of the canister tank 230 is attenuated from the purge flow rate calculated by the purge amount calculation unit 402.

  The evaporated fuel amount calculation unit 407 calculates the evaporated fuel amount adsorbed from the fuel tank 220 to the canister tank 230 based on the vehicle speed, idle switch, auxiliary load switch, and outside air temperature.

  The charge amount increase / decrease calculation unit 408 includes the evaporation charge amount estimated by the charge amount estimation unit 403, the charge amount decay time constant of the charge amount decay time constant calculation unit 406, and the evaporated fuel amount calculated by the evaporated fuel amount calculation unit 407. The increase / decrease in the evaporation charge amount of the canister tank 230 is calculated by the amount and the charge amount correction by the charge amount correction calculation unit 410 described later.

  The air-fuel ratio correction coefficient calculation unit 409 calculates an air-fuel ratio correction coefficient from the increase / decrease value of the evaporation charge amount of the canister tank 230 calculated by the charge amount increase / decrease calculation unit 408.

  The charge amount correction calculation unit 410 calculates a correction value for correcting the charge amount of the canister tank 230 of the charge amount increase / decrease calculation unit 408 from the average value of I of the air-fuel ratio feedback control.

FIG. 5 shows a detailed example of the activation condition determination unit 401.
The starting condition requirement in this detailed example is that the engine water temperature is not less than a predetermined value, the elapse of a predetermined time after the complete explosion, the engine speed is not less than a first predetermined value, the engine speed is not more than a second predetermined value, The AND circuit 501 determines whether the difference between the atmospheric pressure and the intake pipe pressure is equal to or greater than a predetermined value and the air-fuel ratio feedback is being performed, and whether all the conditions for failure determination of each sensor are satisfied. ing.

FIG. 6 shows a detailed example of the purge amount calculation unit 402.
The purge amount calculation unit 402 outputs a duty for driving the purge control valve 231 and a required flow rate. The selection unit 601 determines whether or not the charge amount is estimated based on the charge amount estimation permission flag, and outputs the target flow rate from the estimation flow rate setting unit 602 when the charge amount is estimated.

  The target flow rate search unit 603 searches the map for the target flow rate from the engine speed and the engine load. The maximum flow rate search unit 604 searches for the maximum flow rate in each operation region from the engine speed and the engine load. The selection unit 605 selects the smaller of the target flow rate of the target flow rate search unit 603 and the maximum flow rate of the maximum flow rate search unit 604. This selected value is output to the charge amount non-estimation side of the selection unit 601 together with the signal output of the required flow rate.

  The pressure ratio calculation unit 606 calculates a pressure ratio obtained by dividing the intake pipe pressure by the atmospheric pressure. The differential pressure correction value calculation unit 607 calculates a differential pressure correction value from the pressure ratio of the pressure ratio calculation unit 606. The differential pressure correction unit 608 performs the differential pressure correction on the flow rate selected by the selection unit 601.

  The duty setting unit 609 determines a duty for driving the purge control valve 231 with a flow rate subjected to differential pressure correction by table search. The duty determined by the duty setting unit 609 is input to the duty transition processing unit 610 and is set so as to gradually change the duty according to the set constant.

FIG. 7 shows a detailed example of the charge amount estimation unit 403.
The AND circuit 701 is a start condition unit of the charge amount estimation unit 403, and determines whether or not both the charge amount estimation permission and the canister purge control permission condition are satisfied.

  The delay time setting unit 702 sets the delay time from the intake air amount by table search. The flag on time setting unit 703 sets a predetermined flag on time t from the intake air amount by table search.

  The flag control unit 704 turns on the flag after the delay time determined by the delay time setting unit 702 has elapsed, and the other flag control unit 705 determines the estimation time signal for a predetermined time t determined by the flag on time setting unit 703. Turn on. Each calculation unit 706, 707, 708, selection unit 709, calculation unit 710, and previous value storage unit 711 obtains the purge fuel amount from the canister tank 230 in the section where the estimation signal is on. The realized calculation is the integration of the estimated signal ON section of the value of (1-air-fuel ratio correction coefficient) × intake air amount / target air-fuel ratio.

  The calculation unit 712, the comparison unit 713, the selection unit 714, and the previous value storage unit 715 detect the fall of the estimation time signal. When the fall of the estimation signal is detected, a search end signal is output.

  In the present embodiment, the charge amount estimation is performed once from the engine start to the stop, but the charge amount estimation may be performed again under a predetermined condition.

  FIG. 8 shows a detailed example of the relationship between the air-fuel ratio prefetch correction unit 404 and the air-fuel ratio PID control (air-fuel ratio feedback control).

  The air-fuel ratio PID control unit 801 calculates a correction coefficient by air-fuel ratio PID control from the actual air-fuel ratio (measured air-fuel ratio) and the target air-fuel ratio.

  The time constant setting unit (response delay setting means) 802 sets a time constant (response delay of the air-fuel ratio sensor) T1 from the intake air amount by table search. Another time constant setting unit 803 sets a time constant (calculation delay, etc.) T2 from the engine speed by table search. In this embodiment, the time constants T1 and T2 are searched with a predetermined variable in a table. However, the constants may be simply configured.

  An air-fuel ratio pre-correction correction unit 804 calculates an air-fuel ratio pre-correction from the actual air-fuel ratio and time constants T1 and T2. The calculation of the air-fuel ratio pre-correction correction unit 804 in the air-fuel ratio pre-correction correction unit 804 is performed by the following equations 1-1 to 1-3. Expression 1-1 represents a delay system (secondary delay system) of the measured air-fuel ratio with respect to the true air-fuel ratio. Formula 1-2 is a form that cancels out the delay system of Formula 1-1, and shows a calculation formula that is discretized by applying a lead system, and is calculated as a predicted value of the true air-fuel ratio. Equation 1-3 calculates an air-fuel ratio pre-correction from the predicted value of the true air-fuel ratio and the target air-fuel ratio.

  The selection unit 805 and the calculation unit 806 correct the air-fuel ratio PID control by the air-fuel ratio PID control unit 801 using the air-fuel ratio pre-correction calculation unit 804 only when the estimation time signal is output. Add to the coefficient.

FIG. 9 shows a detailed example of air-fuel ratio PID control when the air-fuel ratio pre-correction correction is not used.
The difference value calculation unit 901 calculates the difference between the actual air fuel ratio and the target air fuel ratio. The gain setting units 902 and 903 and the block 904 search the map for the PID control gain (Kp, Ki, Kd) when the estimation time signal is not output based on the engine load and the engine speed. Further, the gain setting units 905, 906, and 907 search the map for the PID control gain when the estimation time signal is output from the engine load and the engine speed.

  The selection unit 908 switches and selects the PID control gain searched for on the map depending on the presence / absence of an estimation time signal. The P-minute calculating unit 909, the I-minute calculating unit 910, and the D-minute calculating unit 911 calculate the P minutes, I minutes, and D minutes of the PID control with respective set gains. Expression 2-1 is an expression for calculating P minutes, Expression 2-2 is an expression for D minutes, and Expression 2-3 is an expression for determining I minutes.

  These P, I, and D components are added by the calculation unit 912 to obtain an air-fuel ratio feedback control coefficient by PID control.

FIG. 10 shows a detailed example of the charge amount increase / decrease calculation unit 408.
The charge amount calculation unit 1001 obtains the canister tank charge amount from the estimated purge amount by table search.

  The previous value storage unit 1002 and the comparison unit 1003 detect the rise of the estimation end signal. When the rise of the estimation end signal is detected, the canister tank charge amount is held by the selection unit 1007 and the previous value storage unit 1008 until the rise of the canister purge control activation determination is detected.

  When the previous value storage unit 1008 for starting determination and the comparison unit 1007 detect the start of starting determination for canister purge control, the current charge amount of the canister tank described later is held.

  The fuel tank fuel evaporation amount calculation unit 1009 calculates the evaporation amount that evaporates from the fuel tank 220 per unit time based on the vehicle speed, idle switch, auxiliary load switch, and outside air temperature. The calculated evaporation amount is added to the canister tank charge amount by the calculation unit 1010, and the calculation unit 1010 outputs the canister tank charge amount CPCSUMMHLD.

FIG. 11 shows a detailed example of the fuel tank fuel evaporation amount calculation unit 1009.
The selection unit 1101 determines whether or not the vehicle is idle. The idle evaporation amount calculation unit 1103 searches the table for the evaporation amount per unit time when the auxiliary load switch is turned on from the outside temperature. Another idle evaporation amount calculation unit 1104 searches the table for the evaporation amount per unit time when the auxiliary load switch is turned off from the outside air temperature. The selection unit 1105 determines whether or not the auxiliary machine load SW is on, and selects the aforementioned evaporation amount during idling.

  The non-idle evaporation amount calculation unit 1102 searches the map for the evaporation amount per unit time from the outside air temperature and the vehicle speed. The evaporation amount by the non-idle time evaporation amount calculation unit 1102 is selected by the selection unit 1101 when it is not idle.

  The selected evaporation amount is integrated by the calculation unit 1106 and the previous value storage unit 1107 to obtain a total evaporation amount.

  Note that the total evaporation amount is cleared to zero by the operation of the selection unit 1109 when the rising determination start of canister purge control is detected by the previous determination value storage unit 1008 and the comparison unit 1007. It has become.

  FIG. 12 shows an example of determination of the charge amount estimation permission flag. When the estimation end signal is turned on, the charge amount estimation permission signal is inverted and turned off.

FIG. 13 shows a detailed example of the air-fuel ratio correction coefficient calculation unit 409.
The decay time constant setting unit 1301 searches the table for the decay time constant T from the required flow rate output by the purge amount calculation unit 402.

  The charge decay amount calculation unit 1302 performs a correction described later on the decay time constant T and the canister tank charge amount CPCSUMMHLD, and calculates the purge amount from the canister tank 230.

  Expression 3-1 is an attenuation expression, and a conversion of this expression is Expression 3-2. From the above equation, the amount purged from the canister tank 230 is expressed by equation 3-3. The expression 3-3 is discretized as the expression 3-4, and the charge attenuation amount calculation unit 1302 executes this expression. Expression 3-5 represents the current charge amount.

  The attenuation amount fuel correction value calculation unit 1303 calculates the attenuation amount fuel correction value based on the target air-fuel ratio, the intake air amount, and the purge amount calculated by the charge attenuation amount calculation unit 1302. Formula 4 represents a calculation formula of the attenuation amount fuel correction value by the attenuation amount fuel correction value calculation unit 1303.

  The canister tank charge amount correction value calculation unit 1304 calculates a canister from the I-average value of the air-fuel ratio PID control, the target air-fuel ratio, the intake air amount, and the attenuation amount fuel correction value calculated by the attenuation amount fuel correction value calculation unit 1303. The correction value of the tank charge amount CPCSUMMHLD is calculated by using the equations 5-1 and 5-2.

  Expressions 5-1 and 5-2 represent correction calculation formulas for the canister tank charge amount CPCSUMMHLD. The deviation ratio of the attenuation amount fuel correction value is calculated from the I-minute average value of the air-fuel ratio PID control in Expression 5-2, and the correction value of the canister tank charge amount CPCSUMMHLD is calculated in Expression 5-1.

  FIG. 14 shows the behavior of each control variable of the engine control apparatus 250 that performs canister purge control.

  A line 1401 indicates on / off of the start condition. A line 1402 indicates an estimation permission signal, and estimation is permitted in a section 1403.

  A line 1404 is a purge flow rate, and an estimated flow rate is output in a section 1405. In a section 1406, the normal purge flow rate is output. Note that the estimated flow rate gradually approaches 0 after the search is completed in the transition process.

  A line 1407 indicates the actual air-fuel ratio of the exhaust gas, and a line 1408 indicates the actual air-fuel ratio when there is no air-fuel ratio pre-correction described above.

  A line 1409 indicates an air-fuel ratio correction coefficient, and a line 1409 indicates an air-fuel ratio correction coefficient when there is no air-fuel ratio pre-correction described above. A section 1410 shows a case where an attenuation correction value at the time of normal purge is entered. A line 1411 indicates the purge amount integrated value at the time of estimation. The estimation ends at the time 1412, and the purge integrated amount at that time becomes an index of the canister tank charge amount.

  A line 1413 indicates a canister tank charge amount. At time 1414, the canister tank purge amount is determined from the purge integrated amount, and then increases or decreases according to the vehicle state and the target flow rate.

  FIG. 15 shows the behavior of each variable of the canister tank charge amount CPCSUMHLD correction calculation.

  A line 1501 indicates a required flow rate to the purge control valve 231. A section 1502 represents the execution cycle of the correction calculation. A line 1503 represents a change in the canister tank charge amount CPCSUMMHLD. Line 1504 represents an attenuation amount fuel correction value. A line 1505 indicates an average value of I for air-fuel ratio PID control. In this example, every time the canister tank charge amount CPCSUMMHLD is corrected, the attenuation amount fuel correction coefficient is increased, and the average value of I is approaching zero.

  FIG. 16 is an example of a flowchart of the control of the engine control device 250 that performs canister purge control.

  In step 1601, the number of electrical signals of the crank angle sensor 219, mainly the number of inputs per unit time of the pulse signal change, is counted, and the engine speed is calculated by arithmetic processing. In step 1602, the air flow rate converted from the voltage flow rate is read from the output voltage of the thermal air flow meter 202.

  In step 1603, a basic fuel amount is calculated from the engine speed and the intake air amount. In step 1604, a basic fuel correction coefficient is searched for a map from the engine speed and the basic fuel amount.

  In step 1605, the actual air-fuel ratio obtained by converting the output voltage of the air-fuel ratio sensor 215 to voltage-air-fuel ratio is read. In step 1606, a map search is performed for the target air-fuel ratio using the engine speed and basic fuel (load). In step 1607, PID control to the target air-fuel ratio is performed using the target air-fuel ratio and the actual air-fuel ratio.

  In step 1608, it is determined whether the canister purge control is in the estimation mode. If it is the estimation mode, step 1609 and step 1610 are performed. In step 1609, the purge amount per unit time is obtained with the estimated duty (estimated flow rate).

  In step 1610, the charge amount of the canister tank is estimated from the purge amount per unit time.

  If it is determined in step 1608 that the non-estimation mode is selected, step 1611, step 1612, and step 1613 are performed. In step 1611, purging is performed with a normal duty (normal flow rate). In step 1612, a charge amount increase / decrease due to purge and charge balance in the canister tank is calculated. In step 1613, a fuel correction coefficient is calculated from the purge amount.

  In step 1614, the basic fuel amount is corrected by the basic fuel correction coefficient, the air-fuel ratio correction coefficient by the PID control, and the purge amount fuel correction coefficient, and the fuel injection amount is calculated.

  In step 1615, a target value for the idle speed is calculated. In step 1616, an ISC target flow rate that can realize the target value of the idle speed is calculated. In step 1617, the ISC target flow rate is output to the ISC control means. In step 1618, a basic ignition timing is calculated based on the engine speed and the engine load (basic fuel amount). In step 1619, correction such as water temperature correction is performed on the basic ignition timing. In step 1620, the corrected ignition timing is set.

  FIG. 17 is a flowchart showing a control routine of the canister purge control means 106.

  In step 1701, it is determined whether a canister purge control activation condition is satisfied. If true, it is determined in step 1702 whether the canister purge control is in the estimation mode or the normal mode. In the estimation mode, the air-fuel ratio pre-correction is calculated from the actual air-fuel ratio in step 1703.

  In step 1704, the charge amount of the canister tank 230 is estimated. If the normal mode is determined in step 1702, the normal purge flow rate is determined in step 1705. In step 1703, the decay time constant of the charge amount of the canister tank 230 is calculated. In step 1708, the increase / decrease in the charge amount is calculated according to the decay time constant and the state of the vehicle. In step 1709, a purge amount fuel correction coefficient is calculated from the purge amount obtained by increasing or decreasing the charge amount. In step 1710, the charge amount is corrected from the I-average value of the air-fuel ratio PID control.

FIG. 18 is a flowchart showing a routine of the activation condition determination unit 401.
In steps 1801 to 1807, conditions such as engine water temperature, predetermined time after complete explosion, engine speed, difference between atmospheric pressure and intake pipe pressure, air-fuel ratio feedback, and failure determination of each sensor are determined. If all are satisfied, the canister purge start condition is satisfied in step 1808, and if not, the canister purge start condition is not satisfied in step 1809.

FIG. 19 is a flowchart showing a routine of the purge amount calculation unit 402.
In step 1901, it is determined whether or not charge amount estimation is permitted. If not, the estimated flow rate is selected as the target flow rate in step 1902.

  In the case of permission, a map search is performed for the target flow rate using the engine speed and the engine load in step 1903, and a map search is performed for the maximum flow rate using the engine speed and the engine load in step 1904.

  In step 1905, the target flow rate is compared with the maximum flow rate, and the smaller one is selected as the target flow rate. In step 1906, the intake pipe pressure is divided by the atmospheric pressure, and the pressure ratio is calculated. In step 1907, a differential pressure correction value is searched from a table using the pressure ratio. In step 1908, the differential pressure correction is performed on the target flow rate. In step 1909, a table search is made for the output duty from the flow rate after the differential pressure correction. In step 1910, a dynamic limiter is applied to the retrieved duty and a transition process is performed.

FIG. 20 is a flowchart showing a routine of the charge amount estimation unit 403.
In step 2001 and step 2002, it is determined whether or not a charge amount estimation condition is satisfied. The determination condition is a case where both the canister purge control start condition and the charge amount estimation permission are satisfied.

  If it is established, at step 2003, the delay time is searched from the intake air amount in a table, and at step 2004, the predetermined time 1 is searched from the intake air amount as a table.

  In step 2005, the flag is turned on for a predetermined time t after the delay time after the conditions in steps 2001 and 2002 are satisfied.

  In step 2006, it is determined whether or not the flag is turned on. While the flag is turned on, an estimation time signal is outputted in step 2007.

  In step 2008, the value of (1-air-fuel ratio correction coefficient) × air amount / target air-fuel ratio is integrated.

  If the flag is off in step 2006, the integrated amount is set as the estimated purge amount in step 2009.

  In step 2010, it is determined whether or not the flag is reversed from on to off. If reversed, an estimation end signal is output in step 2011.

  FIG. 21 is a flowchart showing a routine of the air-fuel ratio pre-correction unit 404 and air-fuel ratio PID control (air-fuel ratio feedback control).

  In step 2101, air-fuel ratio PID control is performed from the actual air-fuel ratio and the target air-fuel ratio. In step 2102, the table is searched for the time constant T1 from the intake air amount. In step 2102, the table is searched for the time constant T2 from the engine speed.

  In step 2104, the air-fuel ratio pre-correction is calculated from the actual air-fuel ratio, target air-fuel ratio, and time constants T1 and T2.

  In step 2105, it is determined whether an estimation time signal is output. If the estimation time signal is output, in step 2106, the air-fuel ratio pre-correction is added to the correction coefficient for air-fuel ratio PID control.

  FIG. 22 is a flowchart showing a routine of air-fuel ratio PID control when the air-fuel ratio pre-correction correction is not used.

  In step 2201, the difference between the actual air fuel ratio and the target air fuel ratio is calculated. In Step 2202, a map search is performed for the gains Kp, Kd, and Ki for P, I, and D of PID control when no estimation signal is output from the engine load and engine speed.

  In step 2203, a map search is performed for the gains Kp, Kd, and Ki for P minutes, I minutes, and D minutes when the estimation signal is output from the engine load and the engine speed.

  In step 2204, it is determined whether or not an estimated signal is output. When the estimated signal is output, in step 2205, gains Kp, Kd, and Ki when the estimated signal is output are selected. If not, the gain Kp, Kd, Ki when the estimation signal is not output is selected in step 2206.

  In step 2207, air-fuel ratio PID control is performed using the selected gain, and in step 2208, an air-fuel ratio feedback control coefficient is calculated.

FIG. 23 is a flowchart showing a routine of the charge amount increase / decrease calculation unit 408.
In Step 2301, a table search is performed for the canister tank charge amount from the above-described estimated purge amount.

  In step 2302, the amount of fuel evaporation in the fuel tank 220 is calculated from the vehicle speed, idle switch on / off, auxiliary load switch on / off, and outside air temperature.

  In step 2303, the fuel evaporation amount is added to the canister tank charge amount CPCSUMMHLD, and the canister tank charge amount CPCSUMHLD is sequentially changed.

  FIG. 24 is a flowchart of a routine in which the fuel evaporation amount calculation unit 407 obtains the amount of fuel evaporated from the fuel tank 220.

  In step 2401, it is determined whether the idle switch is on. If the idle switch is not on, a map search is performed for the amount of evaporation per unit time from the outside air temperature and the vehicle speed in step 2402.

  If the idle switch is on, it is determined in step 2403 whether or not the auxiliary load switch is on. If the auxiliary load switch is on, a table search is performed in step 2404 for the evaporation amount per unit time when the auxiliary load switch is turned on from the outside air temperature. If the auxiliary load switch is not on, a table search is performed in step 2405 for the evaporation amount per unit time when the auxiliary load switch is turned off from the outside air temperature.

  FIG. 25 is a flowchart showing a routine of the air-fuel ratio correction coefficient calculation unit 409. This flowchart is composed of two time interrupts (a) and (b). Steps 2501 to 2503 shown in (a) are carried out by interruption for a fixed time, and steps 2504 and 2505 shown in (b) are carried out by interruption every fixed time determined in a timely manner.

  In step 2501, the table is searched for the decay time constant T from the required flow rate. In step 2502, the attenuation amount is calculated from the canister tank charge amount and the attenuation time constant T. In step 2503, an attenuation amount fuel correction value is calculated from the attenuation amount, the target air-fuel ratio, and the intake air amount.

  In step 2504, a correction value for the canister purge tank charge amount is calculated from the attenuation amount, the target air-fuel ratio, the intake air amount, and the I-minute average value. In step 2505, the canister purge tank charge amount is corrected with the correction value of the charge amount.

  The outline of the engine control apparatus according to the present embodiment described above is that after the engine is started, the purge valve is driven at a predetermined interval and at a predetermined purge flow rate at the first canister purge. During this time, the purged fuel amount is calculated from the air-fuel ratio feedback correction coefficient, and the charge amount of the fuel evaporative gas in the canister tank 230 is estimated based on this fuel amount. In this way, the fuel evaporative gas is purged at a predetermined purge flow rate for a predetermined period at the first canister purge, and the charge amount of the canister tank is estimated from the purge fuel amount during the purge period. A correction coefficient can be obtained in advance, and this can suppress fluctuations in the air-fuel ratio during purging.

  At the time of charge amount estimation, air-fuel ratio fluctuations can be suppressed by taking into account changes in the air-fuel ratio feedback gain and air-fuel ratio pre-correction. The estimated charge amount is corrected by correcting the balance of the purge from the charge / purge from the fuel tank and the air-fuel ratio feedback coefficient according to the state of the vehicle, so that the estimation error can be suppressed and the canister purge can be suppressed. The accuracy of the fuel correction coefficient can be maintained.

  After the amount of charge in the canister tank 230 is estimated, a fuel correction amount is calculated based on the amount of charge, and the amount of fuel that evaporates from the fuel tank 220 is estimated in accordance with the vehicle conditions, and the canister tank 220 is transferred to the canister tank 220. Since the amount of fuel in the canister tank is estimated from the charge / purge balance, the accuracy of the fuel correction coefficient for the canister purge can be maintained.

  Further, during the calculation of the purged fuel amount, the air-fuel ratio fluctuation is suppressed by adding the pre-correction of the air-fuel ratio feedback and changing the air-fuel ratio feedback gain.

102 Basic fuel calculation means 106 Canister purge control means 107 Air-fuel ratio feedback control coefficient calculation means 108 Target air-fuel ratio setting means 109 Basic fuel correction means 201 Engine 202 Thermal air flow meter 207 Fuel injection valve 211 Cam angle sensor 219 Crank angle sensor 215 Air-fuel ratio sensor 220 Fuel tank 230 Canister tank 231 Purge control valve 250 Engine controller 401 Start condition determination unit 402 Purge amount calculation unit 403 Charge amount estimation unit 404 Air-fuel ratio pre-correction correction unit 406 Charge amount decay time constant calculation unit 407 Evaporated fuel amount Calculation unit 408 Charge amount increase / decrease calculation unit 409 Air-fuel ratio correction coefficient calculation unit 410 Charge amount correction calculation unit

Claims (9)

Fuel evaporative gas adsorbing means for adsorbing fuel evaporative gas in the fuel tank;
A fuel evaporative gas purge means that purges the fuel evaporative gas adsorbed by the fuel evaporative gas adsorbing means into the intake passage of the internal combustion engine, including a purge control valve capable of adjusting the opening;
An internal combustion engine control device comprising:
The controller is
Fuel correction means for performing feedback compensation of the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine to a predetermined air-fuel ratio based on the air-fuel ratio detected by the air-fuel ratio detection means;
Fuel evaporative gas purge control means for performing control to open the purge control valve under predetermined conditions;
While the purge control valve is open, purging the fuel evaporative gas from the fuel correction value of the fuel correction means while the fuel correction means is performing a fuel correction calculation for realizing a predetermined air-fuel ratio. Purge amount calculation means for determining the amount,
When the predetermined condition is first met after starting the internal combustion engine,
A charge amount estimating means for obtaining a charge amount of the fuel evaporative gas adsorbed on the fuel evaporative gas adsorbing means from a purge amount of the fuel evaporative gas obtained by the purge amount calculating means;
The charge amount of the fuel evaporative gas determined by the charge amount estimating means is an internal combustion engine,
A charge amount increase / decrease calculating means that increases / decreases according to the state of the vehicle;
A charge amount correcting means for correcting an increase / decrease calculation value of the charge amount increase / decrease calculating means according to a situation of the fuel correcting means;
A fuel correction value calculating means for calculating a fuel correction value based on the charge amount increase / decrease calculated by the charge amount increase / decrease calculating means after the charge amount estimating means calculates the charge amount of the fuel evaporative gas ;
A control apparatus for an internal combustion engine, comprising: The fuel correction means includes a target air-fuel ratio setting means for obtaining a target air-fuel ratio according to the state of the internal combustion engine, an air-fuel ratio detected by the air-fuel ratio detection means, and a target air-fuel ratio set by the target air-fuel ratio setting means An air-fuel ratio feedback control coefficient calculation means for calculating an air-fuel ratio feedback control coefficient for performing PID control from the difference between the two and the fuel evaporative gas purge amount from the fuel correction means under the predetermined condition 2. The control device for an internal combustion engine according to claim 1, wherein a gain of PID control is changed. The fuel correction means includes a target air-fuel ratio setting means for obtaining a target air-fuel ratio according to the state of the internal combustion engine, an air-fuel ratio detected by the air-fuel ratio detection means, and a target air-fuel ratio set by the target air-fuel ratio setting means Is set by an air-fuel ratio feedback control coefficient calculation means for calculating an air-fuel ratio feedback control coefficient for performing PID control from the difference, a response delay setting means for setting a response delay of the air-fuel ratio detection means, and a response delay setting means. An air-fuel ratio pre-correction partial calculation unit that calculates a true air-fuel ratio from the detected value of the air-fuel ratio by the air-fuel ratio detection means based on the response delay, and obtains a fuel correction value from the calculated true air-fuel ratio. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the fuel is corrected by a fuel correction value by the PID control and the air-fuel ratio pre-correction partial calculation unit. The purge control valve opening control means, the purge amount calculating means for setting the purge amount of the predetermined fuel evaporating gas at the predetermined conditions, the pressure difference correction value calculation for calculating a differential pressure correction value from the before and after pressure of the valve 2. The apparatus according to claim 1, wherein the predetermined fuel evaporative gas flow rate can be realized by correcting a valve opening of the purge control valve by the differential pressure correction value. Control device for internal combustion engine. The charge amount increase / decrease calculating means has time constant determining means for determining a time constant that decreases in accordance with the purge amount of the fuel evaporative gas , and the fuel amount per unit time is determined by the time constant determining means. 2. The control apparatus for an internal combustion engine according to claim 1, wherein an amount of fuel evaporative gas evaporating from the tank is obtained, and calculation for increasing or decreasing the charge amount is performed. The charge amount increase / decrease calculating means calculates the amount of fuel evaporative gas that evaporates from the fuel tank per unit time according to the intake air temperature, vehicle speed, idle, and auxiliary load state, and performs an operation to increase or decrease the charge amount. The control apparatus for an internal combustion engine according to claim 1. The charge amount increase / decrease calculating means holds a value when the purge control valve is closed as a result of obtaining an increase / decrease in the adsorbed fuel evaporative gas, and sets the held value to the state of the internal combustion engine or the vehicle. The fuel correction from the fuel tank based on the charge amount increase / decrease is made with the initial value as the sum of the fuel evaporation gas from the corresponding fuel tank and the addition of the fuel evaporation gas from the fuel tank when the purge control valve is opened again. 2. The control apparatus for an internal combustion engine according to claim 1, wherein a value is set. Means for obtaining a variable state of a fuel correction means for realizing a desired air-fuel ratio from the air-fuel ratio detected by the air-fuel ratio detection means with the purge control valve being open with respect to the charge amount estimation means; 2. The control device for an internal combustion engine according to claim 1, further comprising means for obtaining an interval, and correcting the adsorbed amount at a predetermined interval according to the state of the variable. The variable state of the fuel correction means for realizing a desired air-fuel ratio from the air-fuel ratio detected by the air-fuel ratio detection means is an average value of I for the air-fuel ratio PID control. Control device for internal combustion engine.