JP2007100570A - Purge control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a proper purge flow rate while restraining the deterioration in operability by eliminating erroneous estimation of the purge concentration by preventing insufficiency of an evaporation correction by controlling upper-lower limit values of an evaporation correction value in response to a generating quantity of evaporated gas in a fuel tank. <P>SOLUTION: An evaporated gas generating state is estimated based on an output signal by a means for detecting a fuel residual quantity, the fuel temperature, fuel tank pressure, the intake air temperature and atmospheric temperature, and the upper-lower limit values of the evaporation correction value is set in response to the generating quantity of evaporated gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a purge control device for an internal combustion engine, and more particularly to a purge control device that takes into account the HC concentration of the evaporation gas.

  In general, an internal combustion engine (engine) is supplied with fuel not only by a fuel injection valve but also by an evaporative purge process that releases evaporated fuel (evaporative gas) generated in a fuel tank to an intake system.

  In the evaporative purge process, the evaporative gas generated in the fuel tank is collected and adsorbed by the canister connected to the fuel tank, and then the evaporative gas adsorbed by the canister is released to the intake system by introducing outside air into the canister ( Purging).

  In this case, it is necessary to perform air-fuel ratio control that combines the fuel from the fuel injection valve and the fuel from the evaporation purge process. For this reason, various techniques related to purge control in consideration of the HC concentration of evaporation gas have been proposed.

  In order to suppress fluctuations in the air-fuel ratio due to the evaporation purge process, the purge flow rate is set to a purge rate proportional to the amount of intake air to the engine, and the change in the amount of air passing through the throttle valve is followed so that the control purge rate becomes a predetermined value. By controlling the opening of the canister purge valve, the flow rate is controlled so that the purge flow rate becomes a constant ratio (purge rate) of the air flow rate through the throttle valve, and the adverse effect of the purge fuel on the air-fuel ratio feedback is prevented. Yes.

  Also, the purge concentration is estimated from the deviation from the median value of the air-fuel ratio feedback correction coefficient at the time of purging and the purge rate, and from this estimated value of purge concentration and the purge rate, the increase in fuel vapor during purging is estimated. By calculating the output value of the fuel injection valve according to the amount of increase in fuel vapor (evaporation correction), the amount of fuel vapor that is being purged is increased from the amount of fuel supplied by normal fuel control during the purge stop There is a method that realizes stable air-fuel ratio control by controlling the air-fuel ratio feedback correction coefficient to a median value by taking a method of subtracting the minutes (Patent Document 1).

  In the above-described evaporation correction, upper and lower limits are set for the evaporation correction value in order to prevent an adverse effect on the air-fuel ratio feedback due to excessive evaporation correction when the purge concentration is erroneously estimated.

JP 2000-230450 A

  In recent years, exhaust regulations have been strengthened, and regulations on the amount of fuel evaporation have become stricter. In particular, exhaust regulations in North America require that the canister be fully charged with fuel vapor before the exhaust gas test and purged to a predetermined value during the exhaust gas test.

  However, when the purge concentration is high, such as when the canister is fully charged with fuel vapor, such as in an exhaust gas test, if the purge rate is set to a large value, the high-concentration evaporation gas is drawn into the engine all at once. The amount of correction increases and the evaporation correction value sticks to the upper limit value.

  If the evaporation correction value sticks to the upper limit value, the air-fuel ratio fluctuation that cannot be corrected by the evaporation correction will be corrected by the air-fuel ratio feedback control. A step is generated, which causes a large variation in the air-fuel ratio, which adversely affects drivability. For this reason, the purge rate cannot be set large, and the necessary purge flow rate cannot be secured.

  In addition, since the purge concentration estimation is calculated by the amount of deviation from the median value of the air-fuel ratio feedback correction coefficient and the purge rate, if the evaporation correction value sticks to the upper limit, the evaporation correction will be insufficient, so the air-fuel ratio feedback The correction coefficient does not return to the median value, and as a result, an erroneous estimation of the purge concentration occurs.

  The present invention has been made in view of the above points, and its object is to control the upper and lower limit values of the evaporation correction value in accordance with the amount of evaporation gas generated in the fuel tank, resulting in insufficient evaporation correction. It is an object of the present invention to provide a purge control device for an internal combustion engine that can prevent an erroneous estimation of purge concentration, suppress deterioration in operability, and ensure an appropriate purge flow rate.

  In order to achieve the above object, a purge control apparatus for an internal combustion engine according to the present invention includes an evaporative fuel recovery means for recovering fuel evaporated in a fuel tank, and a release for releasing the fuel recovered by the evaporative fuel recovery means into a combustion chamber. And a purge air-fuel ratio estimating means for estimating a purge air-fuel ratio, and a fuel for the combustion chamber based on the purge air-fuel ratio estimated by the purge air-fuel ratio estimating means. An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount by the fuel injection means for performing injection, and a change in the fuel remaining amount of the fuel tank detected by the means for detecting the fuel remaining amount of the fuel tank. Presence / absence and fuel amount are calculated, and at least one of the upper limit value and the lower limit value of the fuel injection amount correction value by the evaporation correction amount calculation means is calculated according to the calculated fuel amount And a evaporation correction upper and lower limit values means that constant.

  An internal combustion engine purge control apparatus according to the present invention includes an evaporated fuel recovery means for recovering fuel evaporated in a fuel tank, and a discharge means for releasing the fuel recovered by the evaporated fuel recovery means into a combustion chamber. And a purge air-fuel ratio estimating means for estimating a purge air-fuel ratio, and a fuel injection means for injecting fuel into the combustion chamber based on the purge air-fuel ratio estimated by the purge air-fuel ratio estimating means. An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount, and an upper limit of a correction value of the fuel injection amount by the evaporation correction amount calculating means according to the fuel temperature detected by the means for detecting the fuel temperature of the fuel tank Evaporation correction upper and lower limit means for setting at least one of a value and a lower limit value.

  An internal combustion engine purge control apparatus according to the present invention includes an evaporated fuel recovery means for recovering fuel evaporated in a fuel tank, and a discharge means for releasing the fuel recovered by the evaporated fuel recovery means into a combustion chamber. And a purge air-fuel ratio estimating means for estimating a purge air-fuel ratio, and a fuel injection means for injecting fuel into the combustion chamber based on the purge air-fuel ratio estimated by the purge air-fuel ratio estimating means. An upper limit value and a lower limit value of the correction value of the fuel injection amount according to the fuel tank pressure detected by the evaporation correction amount calculation means for calculating the correction amount of the fuel injection amount and the means for detecting the fuel tank pressure of the fuel tank Evaporative correction upper and lower limit value means for setting at least one of the above.

  An internal combustion engine purge control apparatus according to the present invention includes an evaporated fuel recovery means for recovering fuel evaporated in a fuel tank, and a discharge means for releasing the fuel recovered by the evaporated fuel recovery means into a combustion chamber. And a purge air-fuel ratio estimating means for estimating a purge air-fuel ratio, and a fuel injection means for injecting fuel into the combustion chamber based on the purge air-fuel ratio estimated by the purge air-fuel ratio estimating means. An evaporation correction amount calculating means for calculating a correction amount for the fuel injection amount, and at least an upper limit value and a lower limit value for the correction value for the fuel injection amount according to the intake air temperature detected by the means for detecting the intake air temperature of the engine intake system. Evaporative correction upper and lower limit value means for setting one of them.

  An internal combustion engine purge control apparatus according to the present invention includes an evaporated fuel recovery means for recovering fuel evaporated in a fuel tank, and a discharge means for releasing the fuel recovered by the evaporated fuel recovery means into a combustion chamber. And a purge air-fuel ratio estimating means for estimating a purge air-fuel ratio, and a fuel injection means for injecting fuel into the combustion chamber based on the purge air-fuel ratio estimated by the purge air-fuel ratio estimating means. An evaporation correction amount calculating means for calculating a correction amount for the fuel injection amount, and at least one of an upper limit value and a lower limit value for the correction value for the fuel injection amount according to the atmospheric pressure detected by the means for detecting the atmospheric pressure. And an evaporation correction upper / lower limit means for setting.

  The purge control device for an internal combustion engine according to the present invention is a combination of at least two purge control devices for an internal combustion engine according to the above-described invention.

  The purge control device for an internal combustion engine according to the present invention controls the upper and lower limit values of the evaporation correction value in accordance with the amount of evaporated gas by means for detecting the remaining fuel amount, fuel temperature, fuel tank pressure, intake air temperature, and atmospheric pressure. Since the evaporation gas generation state is estimated based on the output signal and the upper and lower limits of the evaporation correction value are set, it is possible to prevent insufficient evaporation correction when the control purge rate is increased when the purge concentration is high. Thus, it is possible to suppress the deterioration of the operability and secure the purge flow rate.

  Hereinafter, an embodiment of an internal combustion engine to which a purge control device according to the present invention is applied will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an overall configuration of an engine system including a purge control device for an internal combustion engine according to the present embodiment. In FIG. 1, an internal combustion engine 1 is a V-type 6-cylinder engine and includes a cylinder group having three cylinders for one bank. The cylinder groups 27a and 27b of the banks A and B are provided with intake manifolds 11a and 11b and exhaust manifolds 21a and 21b, respectively. The intake manifolds 11a and 11b are configured as branched intake pipes.

  The intake manifolds 11 a and 11 b are connected to the air cleaner 2 via the surge tank 9 and the throttle body 5, and the air sucked from the inlet 3 of the air cleaner 2 enters the throttle body 5 through the intake duct 4.

  The intake duct 4 has an air flow meter (air flow meter) 7 for detecting the amount of intake air, and the throttle body 5 has a throttle valve 6 for controlling the air flow rate and a throttle sensor 8 for measuring the opening of the throttle valve 6. It is installed in a proper position.

  The throttle body 5 is provided with an auxiliary air valve (ISC valve) 10 that bypasses the throttle valve 6. The ISC valve 10 controls the amount of air so that the idle speed is maintained at a predetermined value.

  The air that has passed through the throttle body 5 enters the surge tank 9, is distributed by the intake manifolds 11a and 11b, and enters the cylinder groups 27a and 27b.

  The fuel in the fuel tank 13 is sucked and pressurized by a fuel pump (fuel pump) 26, passes through a fuel filter 15, and fuel injection valves (injectors) 12a and 12b installed in the intake manifolds 11a and 11b for each cylinder. Supplied to ... The injectors 12a, 12b... Are one mode of fuel injection means for injecting fuel into the combustion chamber, and inject and supply the fuel to the combustion chamber.

  Connected to the fuel tank 13 is a canister 40 which is an embodiment of a means for recovering evaporated fuel by an evaporation gas pipe 46. The evaporated fuel (evaporative gas) generated in the fuel tank 13 is adsorbed by the canister 40 through the vapor gas pipe 46 and temporarily recovered. The canister 40 is provided with an air introduction port 45 for introducing outside air.

  During the operation of the internal combustion engine 1, the fuel recovered in the canister 40 passes through the evaporative gas pipe 47 and the canister purge valve 41 that controls the flow rate (purge flow rate) for releasing the fuel into the combustion chamber together with the air from the air inlet 45. The canister purge valve 41 supplies the cylinders 27a and 27b. Thereby, the discharge | emission to the exterior of evaporation gas is suppressed.

  One purge valve 41 is common to the banks A and B, and one purge valve 41 is arranged at a position equidistant from the intake manifolds 11a and 11b. The purge valve 41 is introduced with negative pressure by energization, and adjusts and controls the purge flow rate. Here, the purge valve 41 serves as a discharge means for discharging the fuel collected in the canister 40 to the combustion chamber while measuring the flow rate.

  The purge flow rate controlled (measured) by the purge valve 41 is controlled as a purge rate proportional to the amount of intake air to the internal combustion engine 1, and prevents adverse effects (variations) on the air-fuel ratio feedback as will be described later.

The air-fuel mixture in the cylinder groups 27a and 27b is ignited and burned by spark plugs 18a, 18b... Provided for each cylinder. The already burned gas (exhaust gas) is sent to the exhaust manifolds 21a and 21b, purified by the front catalysts 23a and 23b and the main catalyst 24, and then discharged to the atmosphere via the muffler 25. At appropriate positions of the exhaust manifolds 21a and 21b, O ₂ sensors 22a and 22b, which are one mode of means for detecting the air-fuel ratio, are arranged.

Water temperature for detecting the temperature of the engine angle, the cam angle sensor 17, the air flow meter 7, the throttle sensor 8, the O ₂ sensors 22 a and 22 b, which are basic signals for controlling the fuel injection timing and the ignition timing. A signal representing the engine state such as the sensor 20 is input to an engine control device (control unit) 30 including a purge control device 30a.

  As shown in FIG. 2, the control unit 30 is composed of an MPU 31, a read / write free RAM 32, a read only ROM 33, and an I / O LSI 34 for controlling input / output. 36 and 37 are connected so as to be able to transmit signals in both directions.

Specifically, the MPU 31 includes a cam angle sensor 17, an air flow meter 7, a throttle sensor 8, O ₂ sensors 22 a and 22 b, a water temperature sensor 20 that detects the temperature of the internal combustion engine 1, a battery voltage sensor 51, an ignition switch 52, A starter switch 53, a vehicle speed sensor 54, a fuel remaining amount sensor 55 for detecting the remaining amount of fuel in the fuel tank 13, a fuel temperature sensor 56 for detecting the fuel temperature in the fuel tank 13, and a fuel tank pressure sensor for detecting the pressure in the fuel tank 13. 57. Sensor signals and switch signals are input to the I / O LSI 34 from the intake air temperature sensor 58 for detecting the intake air temperature and the atmospheric pressure sensor 59 for detecting the atmospheric pressure, and these input signals are received through the bus 37 and stored in the ROM 33. The processing contents are sequentially called to perform predetermined processing, stored in the RAM 32, and then I / O The LSI 34 outputs drive signals to the injectors 12a, 12b, spark plugs 18a, 18b, ISC valve 10, canister purge valve 41, fuel pump 26, and the like.

  The purge control device 30a included in the control unit 30 includes a fuel feedback compensation system for performing feedback control of the fuel injection amount by the injectors 12a, 12b... Based on the purge flow rate control by the canister purge valve 41 and the purge air-fuel ratio. Fuel injection amount correction control for correcting the fuel injection amount by the injectors 12a, 12b... Is performed.

  Details of the purge control device 30a will be described with reference to FIG. The purge control device 30a includes a base air-fuel ratio learning process performed by the banks A and B for each bank A and B, and a purge process for releasing the evaporated gas adsorbed by the canister 40 to the intake system in this embodiment. Switch each to perform each process.

  Specifically, the purge control device 30a includes a purge period / air-fuel ratio learning period switching unit 30A, air-fuel ratio feedback control units 30Ba and 30Bb on the bank A side and bank B side, and a purge flow rate for performing fuel purge flow rate control. Control means 30a1, evaporation correction upper and lower limit calculation means 30Ha, 30Hb on bank A side and bank B side, evaporation correction amount calculation means 30Ia, 30Ib on bank A side and bank B side, bank A side and bank B side Air fuel ratio learning means 30Da, 30Db and fuel injection amount correction means 30Ga, 30Gb on the bank A side and bank B side.

  The purge flow rate control means 30a1 includes purge air / fuel ratio estimation means 30Ca and 30Cb on the bank A side and bank B side, purge air / fuel ratio comparison / adjustment means 30E, and control purge rate calculation means 30F.

As will be described later, the purge period / air-fuel ratio learning period switching means 30A determines whether or not predetermined conditions such as an air-fuel ratio learning condition and a purge condition are satisfied based on output signals from the O ₂ sensors 22a and 22b. The period of the air-fuel ratio learning process by the air-fuel ratio learning means 30Da, 30Db on the bank A side and the bank B side, and the purge by the purge air-fuel ratio estimation means 30Ca, 30Cb on the bank A side and bank B side of the purge flow rate control means 30a1 Switch between processing periods.

The air-fuel ratio feedback control means 30Ba, 30Bb on the bank A side and the bank B side are provided for each bank A, B so that the actual air-fuel ratio of the exhaust gas measured by the O ₂ sensors 22a, 22b becomes the target air-fuel ratio. Air-fuel ratio feedback control is performed, air-fuel ratio feedback values αa and αb are calculated, and the air-fuel ratio feedback values αa and αb are purged air-fuel ratio estimation means 30Ca and 30Cb on the bank A side and bank B side, Output to the air-fuel ratio learning means 30Da, 30Db on the bank B side and the fuel injection amount correction means 30Ga, 30Gb on the bank A side and bank B side.

  In the bank A side and bank B side air-fuel ratio learning means 30Da, 30Db, the correction amounts by the bank A-side and bank B-side air-fuel ratio feedback control means 30Ba, 30Bb become predetermined values in order to perform air-fuel ratio feedback control. The learning correction values αma and αmb are calculated based on the air-fuel ratio feedback values αa and αb, and the learning correction values αma and αmb are calculated based on the fuel injection amount correction means 30Ga on the bank A side and the bank B side. Output to 30 Gb.

  The purge flow rate control means 30a1 stops the control of the purge valve 41 when the air / fuel ratio feedback control by the bank A side and bank B side air / fuel ratio feedback control means 30Ba and 30Bb is stopped.

  The purge air-fuel ratio estimating means 30Ca, 30Cb on the bank A side and the bank B side estimate the purge air-fuel ratio AFevp based on the air-fuel ratio feedback values αa, αb and the purge rate Kevp, and the estimated purge air-fuel ratio AFevp is purged empty. Output to the fuel ratio comparison adjustment means 30E and the evaporation correction amount calculation means 30Ia, 30Ib. The purge air-fuel ratio AFevp is a basis for calculating the estimated value PDEN of the evaporation concentration. Hereinafter, the estimated value PDEN of the evaporation concentration will be described as being equivalent to the purge air-fuel ratio.

  The purge air-fuel ratio comparison / adjustment means 30E compares the purge air-fuel ratios AFevp of the banks calculated by the purge air-fuel ratio estimation means 30Ca, 30Cb on the bank A side and the bank B side, and calculates the deviation from the target air-fuel ratio that is stoichiometric. The maximum value, more specifically, the maximum absolute value of the deviation is output to the control purge rate calculation means 30F.

  The control purge rate calculation means 30F is based on the purge air / fuel ratio AFevp calculated by the purge air / fuel ratio comparison / adjustment means 30E, the passing air amount Qtvo of the throttle valve 6 measured by the air flow meter 7, and the purge flow rate Qevp of the canister 40. Then, the control purge rate Kevp during the purge period is calculated, and a drive signal based on this is output to the canister purge valve 41. The control purge rate calculation unit 30F outputs the calculated control purge rate Kevp to the evaporation correction amount calculation units 30Ia and 30Ib.

  The evaporation correction upper and lower limit calculation means 30Ha, 30Hb on the bank A side and the bank B side are sensors 55, 56, 57, 58, 59 for detecting the remaining fuel amount, fuel temperature, fuel tank pressure, intake air temperature, and atmospheric pressure. Based on the output signal, the evaporation correction upper and lower limit values of the banks A and B are calculated, and the calculated evaporation correction upper and lower limit values are output to the evaporation correction amount calculating means 30Ia and 30Ib on the bank A side and the bank B side.

  Specifically, the evaporation correction upper / lower limit value calculation means 30Ha, 30Hb affects at least one of the upper limit value and the lower limit value of the correction value of the fuel injection amount by the evaporation correction amount calculation means 30Ia, 30Ib on the generation amount of the evaporation gas. Is set according to one of the following state quantities or a combination of at least two.

(1) The amount of refueling calculated by calculating the presence / absence of refueling and the amount of refueling from the change in the remaining amount of fuel in the fuel tank 13 detected by the fuel remaining amount sensor 55. As a specific example, when the evaporation gas immediately after refueling is likely to be generated, the upper limit of the evaporation correction is set to be large over a predetermined period according to the amount of fuel supply.

(2) The fuel temperature in the fuel tank 13 detected by the fuel temperature sensor 56. As a specific example, when the fuel temperature is high, that is, when evaporative gas is likely to be generated, the upper limit of the evaporation correction is set to a large value. Conversely, when the fuel temperature is low, that is, when evaporative gas is difficult to be generated, Increase the lower limit value.

(3) Pressure in the fuel tank 13 measured by the fuel tank pressure sensor 57 (tank upper space pressure). As a specific example, when the fuel tank pressure is high, that is, when the evaporation gas is generated, the upper limit of the evaporation correction is set to a large value. Conversely, when the fuel tank pressure is low, that is, when the evaporation gas is not generated. , Set a large lower limit for evaporation correction.

(4) The intake air temperature of the engine intake system detected by the intake air temperature sensor 58. As a specific example, when the intake air temperature is high, that is, when evaporative gas is likely to be generated, the upper limit of the evaporation correction is set to be large. Conversely, when the intake air temperature is low, that is, when evaporative gas is difficult to occur, the lower limit of the evaporation correction Set a larger value.

(5) Atmospheric pressure detected by the atmospheric pressure sensor 59. When the atmospheric pressure is low, that is, when the evaporation gas concentration is high, the upper limit of evaporation correction is set large.
The evaporation correction amount calculation means 30Ia and 30Ib on the bank A side and the bank B side include the purge air-fuel ratio AFevp of each bank calculated by the purge air-fuel ratio estimation means 30Ca and 30Cb on the bank A side and the bank B side, and the control purge. The evaporation corrections KLMNTCA and KLMNTCB are calculated based on the control purge rate Kevp calculated by the rate calculation unit 30F and the evaporation correction upper and lower limit values calculated by the evaporation correction upper and lower limit calculation units 30Ha and 30Hb, and the calculated evaporation correction KLMNTCA , KLMNTCB is output to the fuel injection amount correction means 30Ga and 30Gb on the bank A side and the bank B side.

  The fuel injection amount correction means 30Ga and 30Gb on the bank A side and the bank B side correct the basic injection amount based on the engine speed Ne and the intake air amount Qa. The air-fuel ratio feedback on the bank A side and the bank B side Calculation of air-fuel ratio feedback values αa, αb by the control means 30Ba, 30Bb, learning correction values αma, αmb by the air-fuel ratio learning means 30Da, 30Db on the bank A side and bank B side, and evaporation correction amounts on the bank A side and bank B side The basic injection amount is corrected based on the evaporation correction values KLMNTCA, KLMNTCB, etc., which are corrected by means 30Ia, 30Ib, and an injection command signal is output to the injectors 12a, 12b,.

  As described above, the upper and lower limit values of the evaporation correction value according to the amount of evaporation gas generated in the fuel tank 13 are controlled by an output signal by means for detecting the remaining fuel amount, fuel temperature, fuel tank pressure, intake air temperature, and atmospheric pressure. By setting the upper and lower limit values of the evaporation correction value by estimating the generation state of the evaporation gas based on the above, it becomes possible to prevent the evaporation correction from being insufficient when the control purge rate is increased when the purge concentration is high. . As a result, it is possible to suppress the deterioration of the drivability and secure the purge flow rate.

Next, the processing flow in the air-fuel ratio learning period will be described with reference to FIG.
First, in step 100, after the engine is started, it is determined whether or not the air-fuel ratio feedback conditions of the banks A and B are satisfied. If the air-fuel ratio feedback state is not in the fuel cut state or the load is stable, that is, if YES, the routine proceeds to step 101.

  On the other hand, this determination operation is repeated when the air-fuel ratio feedback condition is not satisfied.

In step 101, it is determined whether or not the air-fuel ratio learning conditions for banks A and B are satisfied. If the load is more stable, such as when the air-fuel ratio learning state is present, that is, if YES, step 102 is executed. move on.
On the other hand, this determination operation is repeated when the air-fuel ratio learning condition is not satisfied.

  In step 102, it is determined whether or not the initial base air-fuel ratio learning of the banks A and B has been completed. If the learning has not been completed, that is, if NO, the process proceeds to step 103 as a base air-fuel ratio learning period. Learning is performed, and then the process proceeds to step 104. In step 104, when the air-fuel ratio learning is performed, the learning number counter KLCONTA of the corresponding area is incremented by 1, and the process proceeds to step 105.

  On the other hand, when the first base air-fuel ratio learning is completed, that is, when YES, the routine proceeds to step 108.

  In step 105, it is determined whether or not the learning number counter has reached the predetermined number of times KLCNT. If the learning number counter has reached the predetermined number of times KLCNT, that is, if YES, it is determined in step 106 that the initial base air-fuel ratio learning has ended, and the process proceeds to step 107. Proceed to complete a series of operations.

  On the other hand, when the cumulative number of air-fuel ratio learning is smaller than KLCNT in step 105, the air-fuel ratio learning period has not ended yet, so the routine proceeds to step 103 and the above operations are repeated. This air-fuel ratio learning period is set to a period proportional to the rich and lean cycles.

  On the other hand, when the initial base air-fuel ratio learning of the banks A and B is completed in step 102, it is determined in step 108 whether or not the purge period has ended. If the purge period has ended, that is, if YES, the routine proceeds to step 109 as the base air-fuel ratio learning period, and then proceeds to step 110. However, when the purge period has not ended, the process proceeds to step 111 as the purge period.

In step 110, the air-fuel ratio feedback control means 30Ba, 30Bb determines whether the rich and lean cycles of the O ₂ sensors 22a, 22b have reached the predetermined number of times LRNCNT. If YES, the base air-fuel ratio learning period ends and the routine proceeds to step 107.

  On the other hand, if the predetermined number of times LRNCNT has not been reached, that is, if NO, the base air-fuel ratio period is set.

Next, the processing flow during the purge period will be described with reference to FIG.
First, in step 200, it is determined whether or not the air-fuel ratio learning of the bank A is completed. If this is completed, that is, if YES, the process proceeds to step 201.

On the other hand, when it is not finished, the air-fuel ratio learning period is continued.
In step 201, it is determined whether or not the air-fuel ratio learning of the bank B is completed. If this is completed, that is, if YES, the process proceeds to step 202. On the other hand, the air-fuel ratio learning period is continued when not completed.

  In step 202, it is determined whether the purge conditions such as the elapsed time after engine start, the engine coolant temperature, and the load are satisfied. If these conditions are satisfied, that is, if YES, the routine proceeds to step 203 as the purge period. This operation is repeated until this condition is satisfied.

  When the purge period is reached in step 203, the base air-fuel ratio learning is prohibited in step 204, and in step 205, it is determined whether it is the first purge period before the evaporation concentration that is the basis of the purge air-fuel ratio estimation.

  If it is the first purge period, that is, if YES, the routine proceeds to step 206, where the target purge rate CPBASE is gradually increased, and at step 207, the control purge rate CTRTCTL is set to the target purge rate CPBASE.

  On the other hand, if it is not the first purge period in step 205, that is, if NO, the process proceeds to step 207, and the control purge rate CTRTCTL is set to the target purge rate CPBASE, and the process proceeds to step 208.

  As described above, immediately after the internal combustion engine 1 is started, learning of the air-fuel ratio is started, and when the learning of the air-fuel ratio has been performed a predetermined number of times or when the learning value has converged, the control proceeds to the first purge valve control. To do. The target purge rate will be described later.

  In step 208, the purge air-fuel ratio estimating means 30Ca, 30Cb estimates the purge air-fuel ratios (evaporation concentration estimated values) PDENA, PDENB of the banks A, B, and the process proceeds to step 209. The method for estimating the purge air-fuel ratio will be described later in detail.

  In step 209, each bank A, B is determined based on the output signal of the means for detecting the remaining fuel amount, fuel temperature, fuel tank pressure, intake air temperature, atmospheric pressure, etc. in the evaporation correction upper / lower limit value calculating means 30Ha, 30Hb. The evaporation correction upper and lower limit values KLMNTCMX and KLMNTCMN are calculated, and the process proceeds to Step 210. A method for calculating the evaporation correction upper and lower limit values will also be described in detail later.

  In step 210, the evaporation correction values KLMNTCA and KLMNTCB of the banks A and B are calculated from the control purge rate CTRTCTL, the purge air-fuel ratios PDENA and PDENB, and the evaporation correction upper and lower limit values KLMNTCMX and KLMNTCMN. In step 211, the fuel injection pulses TiA and TiB of the banks A and B are corrected by the evaporation correction values KLMNTCA and KLMNTCB.

In step 212, it is determined whether or not the rich and lean cycle of the O ₂ sensor 22a of the bank A has reached the predetermined number of times LRNCNT. If the predetermined number of times LRNCNT has been reached, that is, if YES, the purge period of the bank A is terminated. Proceed to step 213.

On the other hand, when the predetermined number of times LRNCNT has not been reached, this operation is repeated. In step 213, it is determined whether or not the rich and lean cycle of the O ₂ sensor 22b of the bank B has reached the predetermined number of times LRNCNT. If the predetermined number of times LRNCNT has been reached, that is, if YES, the purge period ends, and step 214 is performed. Go to and end the series of operations. On the other hand, when the predetermined number of times LRNCNT has not been reached, this operation is repeated.

The air-fuel ratio learning control and the purge valve control described above are repeated alternately every predetermined period corresponding to the rich and lean inversion periods of the O ₂ sensors 22a and 22b.

  Next, a processing flow for calculating the purge air-fuel ratio (evaporation concentration estimated value) PDEN that serves as an index of the target purge rate will be described with reference to FIG.

  In step 300, it is determined whether or not the bank A is performing air-fuel ratio feedback. If feedback is being performed, that is, if YES, the process proceeds to step 301. If not, this operation is repeated.

In step 301, it is determined whether the bank B is performing air-fuel ratio feedback. If feedback is being performed, that is, if YES, the process proceeds to step 302. If not, the process returns to step 300. In other words, when the air-fuel ratio feedback control by any one of the air-fuel ratio feedback control means 30Ba and 30Bb based on any one of the O ₂ sensors 22a and 22b is stopped, the control of the purge valve 41 is stopped. Is done.

  In step 302, it is determined whether or not the purge period is in progress. If the purge period is YES, that is, if YES, the process proceeds to step 303. If not, the operation is repeated.

  In step 303, purge air-fuel ratio estimating means 30Ca, 30Cb calculates purge air-fuel ratios (evaporation concentration estimated values) PDENA, PDENB, and in step 304, maximum values of purge air-fuel ratios PDENA, PDENB in bank A and bank B. More specifically, the larger absolute value is calculated as the purge air-fuel ratio (evaporation concentration estimated value) PDEN which serves as an index of the target purge rate.

  7 and 8 are explanatory diagrams of control purge rate calculation performed by the control purge rate calculation means 30F of the purge flow rate control means 30a1. The purge rate calculation means 30F first determines the target purge rate CPBASE, and then calculates the control purge rate.

  As shown in FIG. 7, the target purge rate CPBASE is large when the purge air-fuel ratio AFevp is large, that is, when the purge air-fuel ratio (evaporation concentration estimated value) PDEN as an estimated value of the evaporation concentration is small, or the purge air-fuel ratio AFevp is small. That is, when the purge air-fuel ratio (evaporation concentration estimated value) PDEN is large, it is set low.

  The former is to prevent A / F lean and unnecessary negative pressure from being introduced into the fuel tank 13 due to the empty purge, and the latter is a decrease in drivability when the evaporation concentration is high, such as during thermal damage. This is to prevent it.

  The target purge rate CPBASE is set high in the intermediate value region of the purge air-fuel ratio. Thus, the purge flow rate is gained when the purge air-fuel ratio is an intermediate value, that is, an intermediate value where the evaporation concentration is neither thick nor thin.

  The control purge rate CTRTCTL is calculated by the ratio of the purge flow rate Qevp to the intake air amount Qa of the internal combustion engine 1 (Qevp / Qa), thereby obtaining the purge control amount.

  Here, while the intake air amount Qa varies greatly depending on the running state, the purge flow rate Qevp is limited to the maximum flow rate of the canister purge valve 41, so the control purge rate CTRTCTL decreases as the intake air amount Qa increases. However, when the suction pipe negative pressure approaches the atmospheric pressure, the purge flow rate Qevp decreases when the suction pipe negative pressure approaches the atmospheric pressure. In this case as well, the control purge rate CTRTCTL is not kept constant.

  Therefore, as shown in FIG. 8, the control purge rate CTRTCTL when the canister purge valve 41 is fully opened (valve duty 100%) is preset with reference to the maximum purge rate map obtained from the engine speed and load, and the purge rate To maintain a certain level.

  Thus, the control duty for the canister purge valve 41 can be obtained by dividing the control purge rate CTRTCTL by the control purge rate calculation means 30F by the maximum purge rate.

  Since it is difficult to flow a purge flow rate equal to or higher than the maximum purge rate, the control purge rate CTRTCTL by the control purge rate calculation means 30F is limited by the maximum purge rate.

  Next, the processing flow for calculating the evaporation correction upper and lower limit values by the evaporation correction upper and lower limit value calculating means 30Ha and 30Hb on the bank A side and the bank B side will be described with reference to FIG.

  First, in step 400, it is determined whether or not the fuel supply determination is satisfied. If the fuel supply determination is not satisfied, the process proceeds to step 403, and the fuel supply amount correction coefficients FLMX and FLMN are set to 1.0, respectively.

  On the other hand, when the fuel supply determination is established, the routine proceeds to step 401. This refueling determination method will be described later.

  In step 401, it is determined whether or not the time after engine start is smaller than a predetermined value. When the time is larger than the predetermined value, the process proceeds to step 403, where the fuel supply amount correction coefficients FLMX and FLMN are set to 1.0.

  On the other hand, when the time after engine start is smaller than the predetermined value, the routine proceeds to step 402, and an oil supply amount correction coefficient upper limit table as shown in FIG. 11 and an oil supply amount correction coefficient lower limit table as shown in FIG. Then, oil supply amount correction coefficients FLMX and FLMN corresponding to the amount of oil supplied to the fuel tank 13 are calculated.

  The oil supply amount correction coefficient (upper limit correction coefficient) FLMX is set to a higher value as the oil supply amount is larger according to the oil supply amount correction coefficient upper limit table shown in FIG. The oil supply amount correction coefficient (lower limit correction coefficient) FLMN is set to a higher value as the oil supply amount is smaller according to the oil supply amount correction coefficient lower limit table shown in FIG. Then, the process proceeds to step 404.

  In step 404, based on the output signal of the fuel temperature sensor 56 for detecting the fuel temperature in the fuel tank 13, a fuel temperature correction coefficient upper limit table as shown in FIG. 13 and a fuel temperature correction coefficient lower limit table as shown in FIG. The fuel temperature correction coefficients FTMX and FTMN corresponding to the fuel temperature are calculated.

  The fuel temperature correction coefficient (upper limit correction coefficient) FTMX is set to a higher value as the fuel temperature is higher according to the fuel temperature correction coefficient upper limit table shown in FIG. The fuel temperature correction correction coefficient (lower limit correction coefficient) FTMN is set to a higher value as the fuel temperature is lower according to the fuel temperature correction coefficient lower limit table shown in FIG. Then, the process proceeds to Step 405.

  In step 405, based on the output signal of the fuel tank pressure sensor 57 for detecting the fuel tank pressure of the fuel tank 13, the fuel tank pressure correction upper limit coefficient table as shown in FIG. 15 and the fuel tank pressure as shown in FIG. Referring to the correction lower limit coefficient table, fuel tank pressure correction coefficients FTPMX and FTPMN corresponding to the fuel tank pressure are calculated.

  The fuel tank pressure correction coefficient (upper limit correction coefficient) FTPMX is set to a higher value as the fuel tank pressure is higher according to the fuel tank pressure correction upper limit coefficient table shown in FIG. The fuel tank pressure correction coefficient (lower limit correction coefficient) FTPMN is set to a higher value as the fuel tank pressure is lower according to the fuel tank pressure correction upper limit coefficient table shown in FIG. Then, the process proceeds to Step 406.

  In step 406, the intake air temperature correction coefficient upper limit table as shown in FIG. 17 and the intake air temperature correction coefficient lower limit table as shown in FIG. 18 are referred to based on the output signal of the intake air temperature sensor 58 that detects the intake air temperature. Then, intake air temperature correction coefficients THAMX and THAMN corresponding to the intake air temperature are calculated.

  The intake air temperature correction coefficient (upper limit correction coefficient) THAMX is set to a higher value as the intake air temperature is higher according to the intake air temperature correction upper limit coefficient table shown in FIG. The intake air temperature correction coefficient (lower limit correction coefficient) THAMN is set to a higher value as the intake air temperature is lower according to the intake air temperature correction coefficient lower limit table shown in FIG. Then, the process proceeds to Step 407.

  In step 407, based on the output signal of the atmospheric pressure sensor 59 for detecting the atmospheric pressure, an atmospheric pressure correction coefficient upper limit table as shown in FIG. 19 and an atmospheric pressure correction coefficient lower limit table as shown in FIG. 20 are referred to. The atmospheric pressure correction coefficients ATMMX and ATMMN corresponding to the atmospheric pressure are calculated.

  The atmospheric pressure correction coefficient (upper limit correction coefficient) ATMMX is set to a higher value as the atmospheric pressure is higher according to the atmospheric pressure correction upper limit coefficient table shown in FIG. The atmospheric pressure correction coefficient (lower limit correction coefficient) ATMMN is set to a higher value as the atmospheric pressure is lower according to the atmospheric pressure correction correction coefficient lower limit table shown in FIG. Then, the process proceeds to Step 408.

  In step 408, the basic values KLMX and KLMN of the evaporation correction upper and lower limit values are read, and the process proceeds to step 409.

In step 409, the correction coefficients KLHOSMX and KLHOSMN for the fuel correction upper and lower limit values are calculated by multiplying the correction coefficients calculated in steps 402 to 407 as shown in equations (1) and (2), Proceed to 410.
KLHOSMX = FLMX × FTMX × FTPMX × THAMX × ATMMX (1)
KLHOSMN = FLMN × FTMN × FTPMN × THAMN × ATMMN (2)

In step 410, the evaporation correction upper / lower limit basic values KLMX and KLMN and the fuel correction upper / lower limit value correction unit KLHOSMX and KLHOSMN are multiplied as shown in Equations (3) and (4) to obtain an evaporation correction upper / lower limit value KLMNTCMX. And KLMNTCMN.
KLMNTCMX = KLMX × KLHOSMX (3)
KLMNTCMN = KLMN × KLHOSMN (4)

Next, the processing flow of the fuel supply determination will be described with reference to FIG.
First, in step 500, it is determined whether or not the engine is starting, and if it is not the engine starting, the process is terminated without performing the fuel supply determination. On the other hand, when the engine is started, the routine proceeds to step 501, where the remaining fuel amount is calculated based on the output signal of the remaining fuel sensor 55 that detects the remaining fuel amount, and the routine proceeds to step 502.

In step 502, the remaining fuel amount at the previous stop is read, and the process proceeds to step 503.
In step 503, it is determined whether or not the fuel remaining amount calculated in step 501 subtracted from the fuel remaining at the previous stop read in step 502 is larger than a predetermined value. Then, it is terminated as a refueling determination failure. On the other hand, when it is larger than the predetermined value, the routine proceeds to step 504, where it is determined that the fuel supply determination is established and the routine proceeds to step 505.

  In step 505, the fuel supply amount is calculated from the fuel remaining amount calculated in step 501 subtracted from the fuel remaining amount at the previous stop read in step 502, and the process ends.

  A processing flow for calculating the air-fuel ratio feedback values αa and αb by the air-fuel ratio feedback control means 30Ba and Bb will be described with reference to FIG. Since the air-fuel ratio feedback performs the same operation for the banks A and B, only the operation of one bank will be described below.

First, in step 600, the output of the O ₂ sensor 22 is read. In step 601, the rich / lean determination of the O ₂ sensor 22 is performed. If the output is rich, the process proceeds to step 602, where the lean (Lean) value is determined. ), The process proceeds to step 605. When rich, that is, when the engine air-fuel ratio is small, the output of the O ₂ sensor 22 is about 0.8 v. On the other hand, when lean, that is, when the engine air-fuel ratio is large, the output of the O ₂ sensor 22 is about 0.2 v. Therefore, the rich determination or the lean determination is performed by comparing the output value with a predetermined value (0.5 v).

In step 602, the previous processing state is checked. That is, it is determined whether or not the previous time was rich. If the previous time was not rich, that is, if the previous time that was NO was in the lean state, this time, since the lean state has changed to the rich state, step 603 is performed. Then, as shown in the equation (5), proportional control (subtraction) is performed, and the process proceeds to Step 608.
α = α-ARP (5)
Here, ARP is a proportional correction amount at the time of rich, and data is stored in the ROM 33.

On the other hand, if the previous time is the rich state in step 602, that is, if YES, the process proceeds to step 604, where integral control (subtraction) is performed as shown in equation (6), and the process proceeds to step 608.
α = α-ARI (6)
Here, ARI is the amount of integral correction when rich, and data is stored in the ROM 33.

In step 605, the previous processing state is checked in the same manner as in step 602. That is, it is determined whether or not the previous time was rich. If the previous time was rich, that is, if YES, the state has changed from rich to lean this time, so the process proceeds to step 606 and is shown in equation (7). Thus, proportional control (addition) is performed, and the process proceeds to step 608.
α = α−ALP (7)

Here, ALP is a proportional correction amount at the time of rich, and the data is stored in the ROM 33. On the other hand, when the previous time is not the rich state in step 605, the process proceeds to step 607, where integral control (addition) is performed as shown in (8), and the process proceeds to step 608.
α = α + ALI (8)
Here, ALI is an integral correction amount at the time of lean, and the data is stored in the ROM 33.

  In step 608, each air-fuel ratio feedback value α obtained in step 603, step 604, step 606 or step 607 is stored in the RAM 32 and proceeds to step 609. In this step 609, weighted average processing is performed in this embodiment. Αave after the averaging process of each air-fuel ratio feedback value α is obtained, and a series of operations is terminated.

  Next, the purge air-fuel ratio estimating means 30Ca and 30Cb will be described. Regarding the purge air-fuel ratio estimation, since the same operation is performed for each of the banks A and B, only the operation of one bank will be described below.

First, the effect of the evaporation gas on the air-fuel ratio to the internal combustion engine 1 will be described below.
The engine air-fuel ratio AFcy1 due to the air-fuel mixture supplied into the cylinder group 27 is calculated as in equation (9).
AFcy1 = (Qtvo + qAevp) / (Qinj + qFevp) (9)
Here, Qtvo is the amount of air passing through the throttle valve 6, Qinj is the amount of fuel injected by the injector 12, qAevp is fresh air passing through the canister 40, and qFevp is the amount of fuel leaving the canister 40.

Further, the purge air-fuel ratio AFevp is calculated as shown in Expression (10).
AFevp = (qAevp / qFevp) (10)

Then, the purge flow rate Qevp passing through the canister purge valve 41 is expressed by the equation (11).
Qevp = qAevp + qFevp (11)

Here, since the engine air-fuel ratio AFcy1 is controlled to be the stoichiometric air-fuel ratio 14.7 in the air-fuel ratio feedback on the system, when the air-fuel ratio feedback value α is set, the equation (12) is obtained.
14.7 = (Qtvo + qAevp) / (α × Qinj + qFevp) (12)

When Expression (12) is summarized by the air-fuel ratio feedback value α, Expression (13) is obtained.
α = (Qtvo + qAevp) / (14.7 × Qinj) − (qFevp / Qinj) (13)

Since the fuel injection amount Qinj by the injector 12 is adjusted to be the stoichiometric air-fuel ratio 14.7, if the fuel injection amount Qinj (= Qtvo / 14.7) is deleted from the equation (13), the equation (14 ) Is obtained.
α = 1 + (qAevp / Qtvo) − ((14.7 × qFevp / Qtvo)
... (14)

Therefore, Expression (15) is obtained from Expressions (10), (11), and (14).
α = 1 + (Qevp / Qtvo) × ((AFevp−14.7 / AFev + 1)
... (15)

  Therefore, it can be understood from the equation (15) that if the control purge rate (Qevp / Qtvo) can be controlled to be constant, the purge air-fuel ratio AFevp can be calculated based on the air-fuel ratio feedback value α, and the evaporation used for correcting the injection pulse can be calculated. In the correction value KLMNTC, the portion of (AFevp-14.7) / (AFevp + 1) in the equation (15) is used as the estimated value PDEN of the evaporation concentration, and the deviation (α-1) of the air-fuel ratio feedback value α is controlled purge rate (Qevp / Qa).

Next, the correction to the fuel injection amount TI is performed as follows. First, the fuel amount TIEVP for the evaporation is calculated as shown in Expression (16).
TIEVP = (Qevp / Qtvo) × PDEN × TP × COEF (16)
Here, TP is a basic fuel pulse width, and COEF is a correction amount.

  That is, since the deviation (α-1) of the air-fuel ratio feedback value α indicates the current excess / deficiency of the fuel, the deviation (α-1) is multiplied by the current fuel to be injected (TP × COEF). Thus, the fuel amount TIEVP for the evaporation is calculated.

  Therefore, even if the canister purge valve 41 is opened and the evaporation gas is released to the surge tank 9, it can be understood that the engine air-fuel ratio can be kept constant if the fuel amount TIEVP for the evaporation is reduced from the fuel injection amount TI. This can be expressed as in equation (17), and if the base air-fuel ratio learning is accurately performed, the air-fuel ratio feedback value α is considered to converge to around 1.0. If it is arranged as 1.0, it will become like Formula (18).

When an evaporation correction value KLMNTTC, which is an evaporation density correction value, is used, the following equation (19) is obtained.
TI = (TP × COEF × α) −TIEV = (TP × COEF × α) − (Qevp / Qtvo) × PDEN × TP × COEF
= (TP × COEF) × (α− (Qevp / Qtvo) × PDEN) (17)
TI = (TP × COEF) × (1− (Qevp / Qtvo) × PDEN (18)
TI = (TP × COEF) × (1−KLMNTC) (19)
This KLMNTC is (Qevp / Qtvo) × PDEN.

  Therefore, if the fuel injection amount is corrected with the air-fuel ratio correction value KLMNTC obtained from the deviation (α-1) of the air-fuel ratio feedback value α based on this equation (19), the influence of the evaporation can be absorbed, and the engine Variations in the air-fuel ratio can be prevented.

  Next, the processing flow until the learning correction coefficient αm is updated by the air-fuel ratio learning means 30Da, 30Db will be described with reference to FIG. In the air-fuel ratio learning, the same operation is performed for the banks A and B, so only the operation of one bank will be described below.

  First, at step 700, the air-fuel ratio learning period by the air-fuel ratio learning means 30D is confirmed, and the routine proceeds to step 701.

  In step 701, the air-fuel ratio feedback control means 30B reads the air-fuel ratio feedback value α and proceeds to step 702. In step 702, the air-fuel ratio learning means 30D updates the air-fuel ratio learning correction coefficient αm for the area. A series of operations are terminated.

  Next, the processing flow for calculating the actual injection widths Tea and Teb by the fuel injection amount correction means 30Ga and 30Gb will be described with reference to FIG. Regarding the fuel injection setting, since the same operation is performed for the banks A and B, only the operation of one bank will be described below.

First, in step 800, the engine speed Ne is read and the process proceeds to step 801. In step 801, the intake air amount Qa is read and the process proceeds to step 802. Then, in step 802, the basic injection is performed as shown in equation (20). The amount Tp is calculated and the process proceeds to step 803.
Tp = Kinj × Qa / Ne (20)

Here, Kinj is an injector injection amount coefficient. In step 803, after reading various correction coefficients COEF, the fuel injection width TIOUT is calculated as shown in equation (21), and the process proceeds to step 804.
TIOUT = Tp × COEF (21)

Next, in step 804, the air-fuel ratio feedback value α corresponding to the temporary calculated by the air-fuel ratio feedback control means 30B is read, and the process proceeds to step 805. In step 805, the purge air-fuel ratio estimation means 30C is calculated. The evaporation correction value KLMNTC for the purge period is read and the process proceeds to step 806. In step 806, the air-fuel ratio learning value αm for the learning period calculated by the air-fuel ratio learning means 30D is read and the fuel injection amount correction means 30G is read. The fuel injection width TIOUT is corrected, the actual injection width Te is calculated as shown in Equation (22), and the series of operations is completed.
Te = TIOUT × (α + αm + KLMNTC) + Ts (22)

Here, Ts is the invalid pulse width of the injector 12.
Then, the injector 12 is energized from the I / OLS 134 based on the actual injection width Te, and fuel is injected. Actually, since the calculations described above are performed for the banks A and B, the injection pulse is expressed by the equation (23) for the bank A and the equation (24) for the bank B.
Tea = TIOUTa × (αa + αma + KLMNTCA) + Ts (23)
Teb = TIOUTb × (αb + αmb + KLMNTC) + Ts (24)

  Thereby, fuel injection by the actual injection widths Tea and Teb is performed by the injector 12, and predetermined air-fuel ratio control is appropriately performed.

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

1 is an overall configuration diagram showing one embodiment of an internal combustion engine to which a purge control device according to the present invention is applied. The block diagram which shows one Embodiment of the control system of the internal combustion engine to which the purge control apparatus which concerns on this invention is applied. 1 is a block diagram showing an embodiment of a purge control device for an internal combustion engine according to the present invention. The flowchart which shows the process of the air fuel ratio learning period in this embodiment. The flowchart which shows the process of the purge period in this embodiment. The flowchart which shows the process of the purge air fuel ratio calculation for target purge rate calculation in this embodiment. The graph which shows the characteristic of the target purge rate by the purge rate calculation means in this embodiment. The map figure which shows the maximum purge rate by the purge rate calculation means in this execution form. The flowchart which shows the process of the evaporation correction upper / lower limit value calculation in this embodiment. The flowchart which shows the process of the fuel supply determination of the evaporation correction | amendment upper / lower limit value calculation means in this embodiment. The oil supply amount correction coefficient upper limit table of the evaporation correction upper and lower limit value calculating means in the present embodiment. The oil supply amount correction coefficient lower limit table of the evaporation correction upper and lower limit value calculating means in the present embodiment. The fuel temperature correction coefficient upper limit table of the evaporation correction upper and lower limit calculation means in the present embodiment. The fuel temperature correction coefficient lower limit table of the evaporation correction upper and lower limit calculation means in the present embodiment. The fuel tank pressure correction coefficient upper limit table of the evaporation correction upper and lower limit calculation means in the present embodiment. The fuel tank pressure correction coefficient lower limit table of the evaporation correction upper and lower limit calculation means in the present embodiment. The intake air temperature correction coefficient upper limit table of the evaporation correction upper and lower limit value calculating means in the present embodiment. The intake air temperature correction coefficient lower limit table of the evaporation correction upper and lower limit value calculation means in the present embodiment. The atmospheric pressure correction coefficient upper limit table of the evaporation correction upper and lower limit value calculating means in the present embodiment. The atmospheric pressure correction coefficient lower limit table of the evaporation correction upper and lower limit value calculation means in the present embodiment. The flowchart which shows the process of the air fuel ratio feedback value calculation by the air fuel ratio feedback control means in this embodiment. The flowchart which shows the process of the air fuel ratio learning value calculation by the air fuel ratio learning means in this embodiment. The flowchart which shows the process of fuel injection amount correction value calculation by the fuel injection amount correction | amendment means in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Air cleaner 3 Air cleaner inlet part 4 Intake duct 5 Throttle body 6 Throttle valve 7 Air flow meter (air flow meter)
8 Throttle sensor 9 Surge tank 10 Auxiliary air valve (ISC valve)
11a Bank A side intake manifold 11b Bank B side intake manifold 12a, 12b ... Fuel injection valve (injector)
13 fuel tank 15 fuel filter 17 the cam angle sensor 18a, 18b ... spark plug 20 water temperature sensor 21a bank A side of the exhaust manifold 21b bank B side of the exhaust manifold 22a bank A side of the _{O 2} sensor 22b bank B side of the _{O 2} sensor 23a Bank A side front catalyst 23b Bank B side front catalyst 24 Main catalyst 25 Muffler 26 Fuel pump (fuel pump)
27a Cylinder group on the bank A side 27b Cylinder group on the bank B side 30 Engine control device (control unit)
30a Canister purge control device 30a1 Purge flow rate control means 30A Purge period / air-fuel ratio learning period switching means 30Ba Bank A side air-fuel ratio feedback control means 30Bb Bank B side air-fuel ratio feedback control means 30Ca Bank A side purge air-fuel ratio estimation means 30Cb Bank B side purge air-fuel ratio estimating means 30Da Bank A side air-fuel ratio learning means 30Db Bank B side air-fuel ratio learning means 30E Purge air-fuel ratio comparison adjusting means 30F Control purge rate calculating means 30Ga Bank A side fuel injection amount correction Means 30Gb Fuel injection amount correction means on the bank B side 30Ha Evaporation correction upper / lower limit value calculation means on the bank A side 30Hb Evaporation correction upper / lower limit value calculation means on the bank B side 30Ia Evaporation correction amount calculation means on the bank A side 30Ib Evaporation correction amount calculation It means 31 MPU
32 RAM
33 ROM
34 I / OLSI
35 Bus 40 Canister 41 Canister purge valve 45 Air inlet 46 Evaporative gas piping 47 Evaporative gas piping 51 Battery voltage sensor 53 Ignition switch 53 Starter switch 54 Vehicle speed sensor 55 Fuel level sensor 56 Fuel temperature sensor 57 Fuel tank pressure sensor 58 Intake temperature sensor 59 Large Barometric pressure sensor

Claims (6)

A purge control device for an internal combustion engine comprising: evaporated fuel recovery means for recovering fuel evaporated in a fuel tank; and discharge means for releasing fuel recovered by the evaporated fuel recovery means into a combustion chamber,
Purge air-fuel ratio estimating means for estimating the purge air-fuel ratio;
An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount by the fuel injection means for injecting fuel into the combustion chamber based on the purge air / fuel ratio estimated by the purge air / fuel ratio estimation means;
The presence / absence of fuel supply and the amount of fuel supplied are calculated from the change in the remaining amount of fuel in the fuel tank detected by the means for detecting the fuel remaining amount in the fuel tank, and the fuel by the evaporation correction amount calculating means is calculated according to the calculated amount of fuel supplied. An evaporation correction upper / lower limit means for setting at least one of an upper limit value and a lower limit value of the correction value of the injection amount;
A purge control device for an internal combustion engine, comprising: A purge control device for an internal combustion engine comprising: evaporated fuel recovery means for recovering fuel evaporated in a fuel tank; and discharge means for releasing fuel recovered by the evaporated fuel recovery means into a combustion chamber,
Purge air-fuel ratio estimating means for estimating the purge air-fuel ratio;
An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount by the fuel injection means for injecting fuel into the combustion chamber based on the purge air / fuel ratio estimated by the purge air / fuel ratio estimation means;
Evaporation correction upper and lower limits for setting at least one of an upper limit value and a lower limit value of the correction value of the fuel injection amount by the evaporation correction amount calculation means according to the fuel temperature detected by the means for detecting the fuel temperature of the fuel tank Value means;
A purge control device for an internal combustion engine, comprising: A purge control device for an internal combustion engine comprising: evaporated fuel recovery means for recovering fuel evaporated in a fuel tank; and discharge means for releasing fuel recovered by the evaporated fuel recovery means into a combustion chamber,
Purge air-fuel ratio estimating means for estimating the purge air-fuel ratio;
An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount by the fuel injection means for injecting fuel into the combustion chamber based on the purge air / fuel ratio estimated by the purge air / fuel ratio estimation means;
An evaporation correction upper and lower limit value means for setting at least one of an upper limit value and a lower limit value of the correction value of the fuel injection amount according to the fuel tank pressure detected by the means for detecting the fuel tank pressure of the fuel tank;
A purge control device for an internal combustion engine, comprising: A purge control device for an internal combustion engine comprising: evaporated fuel recovery means for recovering fuel evaporated in a fuel tank; and discharge means for releasing fuel recovered by the evaporated fuel recovery means into a combustion chamber,
Purge air-fuel ratio estimating means for estimating the purge air-fuel ratio;
An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount by the fuel injection means for injecting fuel into the combustion chamber based on the purge air / fuel ratio estimated by the purge air / fuel ratio estimation means;
An evaporation correction upper and lower limit means for setting at least one of an upper limit value and a lower limit value of the correction value of the fuel injection amount in accordance with the intake air temperature detected by the means for detecting the intake air temperature of the engine intake system;
A purge control device for an internal combustion engine, comprising: A purge control device for an internal combustion engine comprising: evaporated fuel recovery means for recovering fuel evaporated in a fuel tank; and discharge means for releasing fuel recovered by the evaporated fuel recovery means into a combustion chamber,
Purge air-fuel ratio estimating means for estimating the purge air-fuel ratio;
An evaporation correction amount calculating means for calculating a correction amount of the fuel injection amount by the fuel injection means for injecting fuel into the combustion chamber based on the purge air / fuel ratio estimated by the purge air / fuel ratio estimation means;
Evaporation correction upper and lower limit value means for setting at least one of an upper limit value and a lower limit value of the correction value of the fuel injection amount in accordance with the atmospheric pressure detected by the means for detecting atmospheric pressure;
A purge control device for an internal combustion engine characterized by comprising:   6. A purge control device for an internal combustion engine comprising a combination of at least two purge control devices for an internal combustion engine according to any one of claims 1 to 5.

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