JP2007192145A - Canister purge control device of internal-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a canister purge control device of internal combustion engine capable of suppressing fluctuations in air fuel ratio of engine, even if an evapogas with excessive concentration is purged rapidly, in a canister purge control device that performs purge of evapogas with purge quantity corresponding to an engine intake air quantity. <P>SOLUTION: A canister purge control device has target purge ratio calculating means for calculating purge quantity corresponding to engine intake air quantity; and air fuel ratio feedback means for detecting engine exhaust air fuel ratio, and correcting a target air fuel ratio. The control device determines whether the air fuel ratio correction feedback quantity is excessive. Then if determined as excessive, a control purge ratio is gradually decreased from the target purge ratio at a certain percentage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a canister purge control device for an internal combustion engine, and more particularly to a canister purge control for an internal combustion engine that suppresses fluctuations in the air-fuel ratio by estimating a purge air-fuel ratio and correcting a fuel injection amount in accordance with the estimated value. Relates to the device.

  In general, some internal combustion engines perform not only fuel supply by a fuel injection valve but also vapor purge processing for releasing and supplying evaporated fuel (evaporative gas) generated in a fuel tank to an intake system. In this evaporation purge process, the evaporation gas is collected and adsorbed by the canister and then released into the intake system by introducing outside air into the canister.

  In this way, when the evaporation purge process is performed, the air-fuel ratio control that combines the fuel by the evaporation purge process and the fuel by the fuel injection valve is necessary. Proposed. The present inventor interrupts the evaporative purge process even during the update process of the air-fuel ratio learning value, as described in JP-A-2002-70659, as a learning control method of the air-fuel ratio when purging the recovered fuel to the engine. In the air-fuel ratio learning period, the purge control fee is set to a small value (fixed value) that does not affect the air-fuel ratio learning, and the learning value update by the air-fuel ratio learning and the evaporation purge process are alternately performed. is suggesting. In order to suppress air-fuel ratio fluctuations, the air-fuel ratio learning is performed by estimating the air-fuel ratio from the air-fuel ratio feedback value during the vapor purge, controlling the purge valve according to the concentration value, and correcting the fuel injection valve output value. Stable air-fuel ratio control is realized even during the period and the purge period.

JP 2002-70659 A

  However, in the method described in Japanese Patent Application Laid-Open No. 2002-70659, when an excessive concentration of evaporated gas is rapidly purged, the estimation of the evaporated air / fuel ratio is not performed correctly, and the fuel injection amount at the time of releasing the evaporated gas is corrected. There was a possibility that it was not done correctly. Further, when the ratio of the purge flow rate to the engine intake air amount is increased at a stretch, there is a possibility that the estimation of the evaporation air-fuel ratio is not performed correctly. That is, in the method described in Japanese Patent Laid-Open No. 2002-70659, no special consideration is given to factors that cause an estimation error of the air-fuel ratio when the evaporation purge amount and the purge concentration change suddenly.

  An object of the present invention is to provide a canister purge control device for an internal combustion engine that suppresses fluctuations in the air-fuel ratio of the engine when the purge amount and the purge concentration suddenly change when the evaporation gas is released.

  By using the apparatus of the present invention, the evaporative air-fuel ratio can be reliably estimated by lowering the purge rate at a constant rate even when the purge flow rate is suddenly changed and when the excessive concentration of evaporative gas is purged at once. It becomes possible. Thereafter, the purge rate is returned at a constant rate, so that the amount of decrease in the purge flow rate can be minimized.

  Hereinafter, the configuration and operation of a canister purge control device for an internal combustion engine according to an embodiment of the present invention will be described with reference to FIGS.

  First, the overall configuration of the engine system including the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIG.

  FIG. 1 is an example of a system configuration diagram showing an overall configuration of an engine system including a canister purge control device for an internal combustion engine according to an embodiment of the present invention.

  The internal combustion engine 1 shows a V-type 6-cylinder engine as an example, and includes cylinders 27a and 27b for each bank 3. The cylinders 27a and 27b are provided with intake manifolds 11a and 11b and exhaust manifolds 21a and 21b. 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. Air sucked from the inlet 3 of the air cleaner 2 enters the throttle body 5 through the intake duct 4. An air flow meter (AFM) 7 for detecting the amount of intake air is installed in the intake duct 4, and a throttle valve 6 for controlling the air flow rate and a throttle sensor 8 for measuring the opening of the throttle valve 6 are installed in the throttle body 5. Is installed. The throttle body 5 has an auxiliary air valve (ISC valve) that bypasses the throttle valve 6.
10 is provided, and the air amount is controlled so that the idling speed is kept constant. The air passing through the throttle body 5 enters the surge tank 9, and the intake manifold 11a,
11b is distributed into the cylinders 27a and 27b.

On the other hand, the fuel in the fuel tank 13 is sucked and pressurized by the fuel pump 26, passes through the fuel filter 15, and is supplied to the fuel injection valves (injectors) 12 a and 12 b that inject the fuel installed in the intake manifold 11 into the combustion chamber. Supplied and injected. Here, the evaporated fuel (evaporative gas) generated in the fuel tank 13 is adsorbed by the canister 40 which is a means for recovering the evaporated fuel through the pipe 46 and is temporarily recovered. The canister 40 is provided with an air introduction port 45 for introducing outside air. After the recovered fuel is guided to the surge tank 9 through the pipe 47 and the canister purge valve 41 which is a means for releasing the fuel into the combustion chamber together with the air from the air inlet 45 during the operation of the internal combustion engine 1. The exhaust gas is supplied to the cylinders 27a and 27b and the exhaust gas is prevented from being discharged to the outside. A negative pressure is introduced by energization of the canister purge valve 41, and the purge flow rate is adjusted and suppressed. Note that the purge flow rate is controlled as a purge rate proportional to the amount of intake air to the internal combustion engine 1, and as described later, an adverse effect on O ₂ feedback is prevented.

The air-fuel mixture in the cylinders 27a and 27b is ignited and burned by the spark plugs 18a and 18b, then sent to the exhaust manifolds 21a and 21b, and purified by the front catalysts 23a and 23b and the main catalyst 24. It is discharged via. The exhaust manifolds 21a and 21b are provided with O ₂ sensors 22a and 22b which are means for outputting binary values and detecting the engine air-fuel ratio.

Note that it is possible to use an air-fuel ratio sensor instead of the O ₂ sensor as a system configuration, or to use a combination of the O ₂ sensor and the air-fuel ratio sensor.

Detection of engine speed Cam temperature sensor 17, air flow meter 7, throttle sensor 8, O ₂ sensors 22 a and 22 b that are basic signals for controlling fuel injection timing and ignition timing, and water temperature for detecting the temperature of internal combustion engine 1 A signal indicating the engine state such as the sensor 20 is input to an engine control unit (control unit: CU) 30 including a purge control unit. Based on these signals, the control unit 30 performs predetermined arithmetic processing, performs various controls such as air-fuel ratio control, and outputs each drive signal to the injectors 12a, 12b, the ISC valve 10, the canister purge valve 41, and the like.

  Next, the configuration of the control unit 30 constituting the canister purge control device for the internal combustion engine according to the present embodiment will be described with reference to FIG.

  FIG. 2 is a block diagram showing a configuration of a control unit constituting the canister purge control device for an internal combustion engine according to the embodiment of the present invention.

The control unit 30 includes an MPU 31, a read / write RAM 32, a read-only ROM 33, and an I / O LSI 34 that controls input / output. These are communicated by buses 35, 36 and 37, respectively, and exchange of each data is performed. Specifically, the MPU 60 receives signals representing the engine state such as the air flow meter 7, the cam angle sensor 17, the O ₂ sensors 22 a and 22 b, the throttle sensor 8, and the water temperature sensor 20 from the I / O LSI 34 through the bus 37. Then, a predetermined process in which the processing contents stored in the ROM 33 are sequentially called is performed and stored in the RAM 32. Then, the injectors 12a, 12b, 12c, 12d, 12e, 12f, the ISC valve 10, and the fuel pump 26 are again transmitted from the I / O LSI 34. The drive signals are output to the canister purge valve 41 and the like.

  Next, the configuration of the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIG.

  FIG. 3 is a control block diagram showing the configuration of a canister purge control device for an internal combustion engine according to an embodiment of the present invention. Since the canister purge control apparatus of the present invention performs the same operation for each of the A and B banks, only one operation will be described.

  The purge control device 300 subtracts the purge amount (control purge rate) with respect to the engine intake air amount from the target value (target purge rate) when the excessive concentration of evaporated gas is purged, Processing to suppress air-fuel ratio fluctuations is performed.

  Specifically, the purge control device 300 includes an intake air amount detection means 301, an exhaust air / fuel ratio detection means 302, an engine speed detection means 304, an air / fuel ratio feedback amount calculation means 303, a target purge rate calculation means 305, a purge air / fuel ratio. Calculation means 306, purge period or air-fuel ratio learning period switching means 307, air-fuel ratio learning calculation means 308, control purge rate calculation means 309, purge rate decrease calculation means 310, excess purge determination means 311, purge valve opening calculation means 312, purge A stop determination unit 313 and a fuel injection amount calculation unit 314 are provided.

As will be described later with reference to FIGS. 4 and 5, the purge period or air-fuel ratio learning period switching means 307 is based on output signals from the O ₂ sensors 22a and 22b and other predetermined conditions such as air-fuel ratio learning conditions and purge conditions. Is switched between the period of the air-fuel ratio learning process by the means 308 for learning and controlling the air-fuel ratio and the period of the purge process by the means for purging air-fuel ratio calculating means 306 for controlling the purge flow rate.

The air-fuel ratio feedback amount calculation means 303 performs air-fuel ratio feedback control for each bank so that the actual air-fuel ratio of the exhaust gas discharged from the combustion chamber by the O ₂ sensors 22a and 22b becomes the target air-fuel ratio. The air-fuel ratio feedback value α which is a temporary amount is calculated, and the purge air-fuel ratio calculating means 306, the air-fuel ratio learning means 308, and the fuel injection amount calculating means 314 are passed through the purge period or air-fuel ratio learning period switching means 307. Output.

  The purge air-fuel ratio calculating means 306 estimates the purge air-fuel ratio AFev and the purge air-fuel ratio correction KLMNTC based on the air-fuel ratio feedback value α and the purge rate Kevp, respectively, and the excess purge determining means 311, purge rate decrease calculating means 310 and the fuel injection amount calculation means 314.

  The target purge rate calculating means 305 determines the ratio of the purge with respect to the engine intake air amount according to the air / fuel ratio of the evaporation gas obtained by the purge air / fuel ratio calculating means, and outputs it to the control purge rate calculating means 309.

  The excess purge determination unit 311 determines whether or not the excess gas is determined based on whether the air-fuel ratio of the evaporation gas determined by the purge air-fuel ratio calculation unit 306 is within a predetermined value, and outputs the determination result to the purge rate reduction calculation unit 310. To do.

  The purge rate reduction calculation unit 310 determines the purge rate reduction according to the air / fuel ratio of the evaporation gas obtained by the purge air / fuel ratio calculation unit 306, and outputs it to the control purge rate calculation unit 309 and the purge stop determination unit 313. To do.

  The purge stop determination means 313 determines whether or not to stop the purge from the purge rate reduction obtained by the purge rate reduction calculation means 310 and the engine speed obtained from the engine speed detection means 304, and determines the judgment result as a purge valve. Output to the opening calculation means 312.

  The purge valve opening degree calculation means 312 calculates the opening degree of the purge valve from the purge rate obtained from the control purge rate calculation means 309 and the engine intake air amount obtained from the intake air amount detection means 301, and sends it to the canister purge valve 41. A drive signal is output to release the evaporated gas into the engine intake pipe. When the purge stop determining means 313 determines that the purge is stopped, it outputs a valve closing drive signal to the canister purge valve 41 to stop the emission of the evaporation gas.

  The air-fuel ratio learning unit 308 performs learning so that the correction amount by the air-fuel ratio feedback amount calculation unit 303 becomes a predetermined value in order to perform air-fuel ratio feedback control, and a learning correction value αm based on the air-fuel ratio feedback value α. Is output to the fuel injection amount calculation means 314.

  The purge period or air-fuel ratio learning period switching means 307 switches the purge period and the air-fuel ratio learning period depending on the operating state, and converts the air-fuel ratio feedback amount obtained by the air-fuel ratio feedback amount calculating means 303 into the purge air-fuel ratio calculating means 306 or the air-fuel ratio learning period. Output to the fuel ratio learning means 308.

  The fuel injection amount calculation means 314 corrects the basic injection amount based on the engine speed Ne and the intake air amount Qa, and the air / fuel ratio feedback values αa and αb by the air / fuel ratio feedback amount calculation means 303 and the air / fuel ratio learning means. The basic injection amount is corrected based on the three correction values such as the learning correction values αma and αmb by 308 and the purge air-fuel ratio corrections KLMNTCA and KLMNTCB by the purge air-fuel ratio calculation means 306, and output to the injectors 12a and 12b.

  Next, the operation of the purge period or air-fuel ratio learning period switching means 307 of the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIGS.

  4 and 5 are flowcharts showing the operation of the purge period or air-fuel ratio learning period switching means of the canister purge control device for an internal combustion engine according to one embodiment of the present invention. FIG. 4 shows the operation during the air-fuel ratio learning period, and FIG. 5 shows the operation during the purge period.

  First, the operation during the air-fuel ratio learning period will be described with reference to FIG.

  In step S100 of FIG. 4, the purge period or air-fuel ratio learning period switching means 307 determines whether or not an air-fuel ratio feedback condition is satisfied after the engine is started. The case where the air-fuel ratio feedback condition is satisfied is a case where the air-fuel ratio feedback state is not in the fuel cut state or the addition is stable, and in this case, the process proceeds to step S101. On the other hand, this operation is repeated when the air-fuel ratio feedback condition is not satisfied.

  Next, in step S101, it is determined whether or not the air-fuel ratio learning condition is satisfied. If the load is more stable, for example, the process proceeds to step 102. On the other hand, this operation is repeated when the air-fuel ratio learning condition is not satisfied.

  Next, in step S102, it is determined whether or not the initial base air-fuel ratio learning has not been completed. If it has not been completed, the process proceeds to step S103 as a base air-fuel ratio learning period. On the other hand, if the base air-fuel ratio learning has been completed, the process proceeds to step S108.

  When the initial base air-fuel ratio learning is not completed, the base air-fuel ratio learning of bank A is performed in step S103. When the air-fuel ratio learning is performed, in step S104, the learning number counter KLCONT for the corresponding area is incremented by 1, and the process proceeds to step S105.

  Next, in step S105, 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, it is determined that the initial base air-fuel ratio learning has ended, and the process proceeds to step S106. On the other hand, when the accumulated number of air-fuel ratio learning is smaller than KLCNT in step S105, the air-fuel ratio learning period has not ended yet, so the process proceeds to step S103 and the above operations are repeated. That is, the air-fuel ratio learning period is set to a period proportional to the rich and lean cycles.

  If it is determined in step S105 that the learning number counter has reached the predetermined number of times KLCNT, the initial base air-fuel ratio learning is terminated in step S106, and the base air-fuel ratio learning period of bank A is terminated in step S107.

  If it is determined NO in step S102, it is determined in step S108 whether the purge period has ended. If the purge period has ended, the process proceeds to step S109 as the base air-fuel ratio learning period. On the other hand, if the purge period has not ended, the process proceeds to step S111 as the purge period.

If the purge period has ended, the base air-fuel ratio learning of bank A is performed in step S109. In step S110, the air-fuel ratio feedback amount calculation means 303 determines whether the rich and lean cycle of the O ₂ sensor 22 has reached the predetermined number of times LRNCNT. As the fuel ratio learning period ends, the process proceeds to step S107. On the other hand, if the predetermined number of times LRNCNT has not been reached, the base air-fuel ratio period is set.

  If it is determined in step S108 that the purge period has not ended, the purge period is set in step S111.

  Next, the operation of the purge period or the air-fuel ratio learning period switching means 307 (see FIG. 3) will be described with reference to FIG.

  In step S200, the purge period or air-fuel ratio learning period switching unit 307 determines whether the air-fuel ratio learning of the bank A has been completed. If completed, the process proceeds to step S201. If not completed, the air-fuel ratio learning period is continued.

  Next, in step S201, it is determined whether or not the air-fuel ratio learning of the bank B has been completed. If completed, the process proceeds to step S202. If not completed, the air-fuel ratio learning period is continued.

Next, in step S202, it is determined whether purge conditions such as the elapsed time after engine start, the engine coolant temperature, and the load are satisfied. If the condition is satisfied, step S is set as the purge period.
Proceed to 203. If not completed, the process waits until the purge condition is satisfied.

When the purge condition is satisfied, a purge period is set in step S203, and step S
At 204, base air-fuel ratio learning is prohibited.

Next, in step S205, it is determined whether it is the first purge period before calculation of the evaporation concentration that is the basis of the purge air-fuel ratio estimation. If it is the first purge period, the process proceeds to step S206, and the purge rate CTRTCTL is set. In step S207, the purge rate CTRTCTL is set to the target purge rate CPBASE. If it is determined in step S205 that it is not the first purge period, the process proceeds to step S207, and the purge rate CTRTCTL is set to CPBASE. The target purge rate will be described later.

  Next, in step S208, the purge air-fuel ratio calculating unit 306 determines the purge air-fuel ratio update condition, and proceeds to step S209 only when the update condition is satisfied. The purge air-fuel ratio update condition will be described later with reference to FIG. 6. However, when the evaporated air-fuel ratio is estimated, the estimation of the evaporated gas is stopped and the previous estimated value is stopped when in an operating state causing an error. Hold. As a factor causing an error in the estimation of the evaporation gas, when the ratio of the emission amount of the evaporation gas to the intake air amount is not constant, or when the opening of the purge valve where the evaporation of the evaporation gas is not stably performed is small, and the correction amount of the fuel injection May exceed the predetermined value and the air-fuel ratio of the engine is not stable. When these conditions are determined, the estimation of the evaporated air-fuel ratio is stopped. Further, by limiting the fuel injection correction amount based on the estimated value of the evaporated air / fuel ratio, the engine is protected when the abnormality is estimated.

  Next, in step S209, the purge air-fuel ratio calculating unit 306 estimates the purge air-fuel ratios PDENA and PDENB of each bank. A method for estimating the purge air-fuel ratio will be described later.

  Next, in step S210, the purge air-fuel ratio calculating means 306 calculates purge air-fuel ratio fuel correction values KLMNTCA and KLMNTCB for each bank from the purge air-fuel ratios PDENA and PDENB estimated in step S209.

  Next, in step S211, the fuel pulses TiA and TiB of each bank are corrected based on the fuel injection amount calculation means 314 and the purge air-fuel ratio fuel correction values KLMNTCA and KLMNTCB calculated in step S210.

Next, in step S212, the air-fuel ratio feedback amount calculation means 303 determines whether the rich and lean cycle of the O ₂ sensor 22 of the A bank has reached a predetermined number of times LRNCNT, and if it has reached the predetermined number of times LRNCNT. The process proceeds to step S213. On the other hand, if the predetermined number of times LRNCNT has not been reached, the determination in step S212 is repeated.

Next, in step S213, it is determined whether the rich and lean cycle of the O ₂ sensor 22 in the B bank has reached a predetermined number of times LRNCNT. If the predetermined number of times LRNCNT has been reached, the process proceeds to step S214, where the purge period ends. And On the other hand, if the predetermined number of times LRNCNT has not been reached, the process returns to step S212, and the operations in steps S212 and S213 are repeated.

  Next, the purge air-fuel ratio update condition in the purge period or air-fuel ratio learning period switching means 307 of the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIG.

  FIG. 6 is a flowchart showing a purge air-fuel ratio update condition in the purge period or air-fuel ratio learning period switching means of the canister purge control device for an internal combustion engine according to one embodiment of the present invention.

  First, in step S300, it is determined whether or not the control purge rate is constant. If the purge rate is constant, the process proceeds to step S301. When the control purge rate changes, the purge air-fuel ratio update condition is restarted from the beginning.

Next, in step S301, it is determined whether or not a certain period (INGCPTM) has elapsed since the opening CPCVON of the purge valve becomes equal to or greater than a predetermined value (INHCP). If this condition is satisfied, the process proceeds to step S302. It has been experimentally verified that the threshold value (INHCP) for determining the opening of the purge valve at this time is 5 to 20% including the invalid pulse of the valve. Further, it has been experimentally verified that the period determination threshold (INGCPTM) is 2 to 5 seconds.

Next, in step S302, it is determined whether the fuel injection correction amount COEFA of the bank A is equal to or smaller than a predetermined value (INHCPCEF). If the correction amount is equal to or smaller than the predetermined value, the process proceeds to step S303. When the correction amount is equal to or greater than the predetermined value, the purge air-fuel ratio update condition determination is repeated from the beginning.

Next, in step S303, the fuel injection correction amount COEFB in the bank B is a predetermined value.
It is determined whether or not (INHCPCEF) or less. If the correction amount is less than or equal to a predetermined value, the process proceeds to step S304. When the correction amount is equal to or greater than the predetermined value, the purge air-fuel ratio update condition determination is repeated from the beginning. It is experimentally verified that the threshold value (INHCPCEF) of the correction amount for determination in steps S302 and 303 is about 5 to 10% of the fuel injection amount in the experiment.

  When the conditions of steps S300 to S303 are satisfied, the purge air-fuel ratio update is established in step S304, and the determination process is terminated.

  Next, the operation of the target purge rate calculation means 305, purge rate decrease calculation means 310, and control purge rate calculation means 309 of the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIGS. explain.

  FIG. 7 is an explanatory diagram of the target purge rate obtained by the control purge rate calculation means of the canister purge control device for an internal combustion engine according to one embodiment of the present invention. FIG. 8 is an explanatory diagram of an excess purge determination unit and a purge rate reduction calculation unit of the canister purge control device for an internal combustion engine according to the embodiment of the present invention. FIG. 9 is an explanatory diagram of the control purge rate obtained by the control purge rate calculation means of the canister purge control device for an internal combustion engine according to one embodiment of the present invention.

  When the purge air-fuel ratio is large, that is, when the estimated value PDEN of the evaporation concentration is small, or when the purge air-fuel ratio is small, that is, when the estimated value PDEN of the evaporation concentration is large, the target purge rate is narrowed down. Is set. 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 is set high at an intermediate value of the purge air-fuel ratio, and the purge flow rate is increased.

  Next, an excess purge determination and control purge rate calculation method will be described with reference to FIG.

  In step S400, after the engine is started, it is determined whether an air-fuel ratio feedback condition is satisfied. The case where the air-fuel ratio feedback condition is satisfied is the case where the air-fuel ratio feedback state is not in the fuel cut state or the addition is stable, and in this case, the process proceeds to step S401. On the other hand, this operation is repeated when the air-fuel ratio feedback condition is not satisfied.

  Next, in step S401, it is determined whether or not the air-fuel ratio learning condition is satisfied. If the air-fuel ratio learning state is in effect, such as when the load is more stable, the process proceeds to step S702. On the other hand, this operation is repeated when the air-fuel ratio learning condition is not satisfied.

  Next, in step S402, it is determined whether or not learning of the base air-fuel ratio has ended. If learning of the base air-fuel ratio has ended, such as whether learning of a predetermined operating region has been performed a predetermined number of times, the process proceeds to step S703. If the base air-fuel ratio learning is not completed, this operation is repeated.

  Next, in step S403, it is determined whether or not it is a purge period. If the conditions for the purge period are satisfied, such as the engine speed and the load are within predetermined values, the process proceeds to step S704. On the other hand, when the purge period condition is not satisfied, this operation is repeated.

  Next, in step S404, the purge rate subtraction amount CPCLMP is reflected by the initial value 0 in equation (1), and the process proceeds to step S405.

CPCLMP (i) = 0 (1)
In step S405, the control purge rate CPCNT is obtained by equation (2) and the process proceeds to step S406.

CPCNT = CTDT-CPCLMP (i) (2)
In step S406, it is determined whether or not the air-fuel ratio feedback amount α is other than a predetermined value. If it is within the predetermined value, the process proceeds to step S407, and if it is not the predetermined value, the process proceeds to step S408.

  In step S407, the control purge rate is obtained by equation (3), and the process proceeds to step S409.

CPCLMP (i) = CPCLMP (i−1) −CPSUB (3)
In step S408, it is determined that the purge is excessive, and the process proceeds to step S409, where the control purge rate is obtained by equation (4), and the process proceeds to step S410.

CPCLMP (i) = CPCLMP (i−1) + CPADD (4)
Here, CPADD and CPSUB are set as shown in FIG. That is, CPADD and CPSUB are set larger as the purge air-fuel ratio obtained by the purge air-fuel ratio calculating means 306 is larger, and CPADD and CPSUB are set smaller when the purge air-fuel ratio is smaller. Further, by setting so that CPADD ≧ CPSUB, it is prevented that the excessive purge is determined again when the purge rate is restored.

  The above shows an example based on the purge air-fuel ratio in calculating CPADD and CPSUB, but these can also be calculated using the target purge rate or both the purge air-fuel ratio and the target purge rate. is there.

  In step S410, it is determined whether or not the target purge rate subtraction amount CPCLMP is 0 or more. When the target purge rate subtraction amount CPCLMP is 0 or more, the process proceeds to step S412, and when it is less than 0, the process proceeds to step S411.

  In step S411, the target purge rate subtraction amount CPCLMP is set to equation (5), and the process proceeds to step S412.

CPCLMP (i) = 0 (5)
In step S412, the control purge rate is obtained by equation (6).

CPCNT = CTDT-CPCLMP (i) (6)
After obtaining the control purge rate in step S412, the process returns to S406 and this operation is repeated.

  When the purge period or the air-fuel ratio learning period is changed by the purge period or the air-fuel ratio learning period switching unit 307, the value of the purge rate subtraction amount CPCLMP is held, and when the air-fuel ratio learning period returns to the purge period, A control purge rate CPCNT is calculated using the purge rate subtraction amount CPCLMP value held.

  However, if the purge period is not reached for a predetermined time, the CPCLMP value is initialized to zero.

  Next, the determination method of the purge stop determination means 313 of the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIG.

  First, in step S500, it is determined whether or not the purge rate subtraction amount CPCLMP is 0. If it is 0, the process proceeds to step S201. If it is other than 0, this determination is repeated.

  In step S201, it is determined whether or not the engine speed is greater than or equal to a predetermined value. If the engine speed is greater than or equal to the predetermined value, the process proceeds to step S502, and if smaller than the predetermined value, the process proceeds to step S503.

  In step S502, it is determined that purge is permitted, and the process returns to step S500.

  In step S503, it is determined that purge is prohibited, and the process returns to step S500.

  Next, a calculation method of the purge valve opening calculation means 312 of the internal combustion engine canister purge control apparatus according to the present embodiment will be described.

  While the engine 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 that the control purge rate decreases and increases as the intake air amount Qa increases. When the suction pipe negative pressure approaches atmospheric pressure, the purge flow rate Qevp decreases, and in this case as well, the control purge rate is not held constant.

Therefore, referring to the maximum purge rate map obtained from the engine speed and the engine intake pipe pressure as shown in FIG. 10, when the canister purge valve 41 is fully opened (valve DUTY).
100%) is set in advance to keep the purge rate constant.

Thereby, the required opening degree for the canister purge valve 41 can be obtained by dividing the control purge rate by the control purge rate calculation means 309 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 by the control purge rate calculation means 309 is limited by the maximum purge rate.

  Here, when the purge stop determining means 313 determines that the purge is prohibited, the purge valve is immediately closed to stop the release of the evaporation gas to the engine intake pipe.

  Next, a calculation method of the air-fuel ratio feedback value α by the air-fuel ratio feedback amount calculation means 303 of the internal combustion engine canister purge control apparatus according to the present embodiment will be described with reference to FIG. Since the air-fuel ratio feedback amount calculation means 303 performs the same operation for each of the A and B banks, only one operation will be described.

  FIG. 11 is a flowchart showing an air-fuel ratio feedback value calculation method by the air-fuel ratio feedback means of the canister purge control device for an internal combustion engine according to one embodiment of the present invention.

First, in step S600, the output of the O ₂ sensor 22 is read.
In 601, it is determined whether Rich (the engine air-fuel ratio is small) or Lean (the engine air-fuel ratio is large). In the case of Rich, the process proceeds to step S602, and in the case of Lean, the process proceeds to step S605. Incidentally, Rich, i.e., when the engine air-fuel ratio is small, the output of the O ₂ sensor 22 becomes the about 0.8 v, whereas, Lean, i.e., when the engine air-fuel ratio is large, the output of the O ₂ sensor 22 is zero. Since it becomes about 2v, Rich judgment or Lean judgment is made by comparing this output value with a predetermined value (0.5v).

In the case of Rich, the previous processing state is checked in step S602. In other words, it is determined whether or not the previous time was Rich, and if the previous time was not Rich and was in the Lean state, this means that the current state has changed from Lean to Rich state.
Proceeding to 403, the air-fuel ratio feedback value α is subjected to proportional control (subtraction) as shown in the following equation (7),
α = α-ARP (7)
Next, the process proceeds to step S608. Here, ARP is a proportional correction amount at the time of Rich, and this data is stored in the ROM 33.

On the other hand, when it is determined in step S602 that the previous time is the Rich state,
Proceed to 404, perform integral control (subtraction) as shown in the following equation (8),
α = α-ARI (8)
Next, the process proceeds to step S608. Here, ARI is an integral correction amount at the time of Rich, and this data is stored in the ROM 33.

On the other hand, if it is determined as Lean in step S601, the previous processing state is checked in step S605 as in step S602. That is, it is determined whether or not the previous time was Rich. If the previous time was Rich, the state has changed from Rich to Lean at this time, so the process proceeds to Step S403, and the following equation (9) is obtained. Proportional control (addition)
α = α-ARP (9)
Next, the process proceeds to step S608. Here, ALP is a proportional correction for Rich, and this data is stored in the ROM 33.

On the other hand, when the previous time is not the Rich state in step S605, step S605 is executed.
Proceed to 607 and perform integral control (addition) as shown in the following equation (10).
α = α + ARI (10)
Next, the process proceeds to step S608. Here, ALI is an integral correction for Lean time, and this data is stored in the ROM 33.

  Next, in step S608, the nuclear air / fuel ratio feedback value α obtained in step S603, step S604, step S606 or step S407 is stored in the RAM 32. Next, in step S609, each air / fuel ratio feedback value is obtained by weighted average processing. An average air-fuel ratio feedback value αave after the averaging process of α is obtained, and a series of operations is terminated.

  Next, processing contents of the purge air-fuel ratio calculating means 306 will be described. Regarding the calculation of the air-fuel ratio, since the same operation is performed for each of the A and B banks, only one operation will be described.

  First, the influence of the evaporation gas on the air-fuel ratio of 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 27 is calculated by the following equation (11).

AFcy1 = (Qtvo + qAevp) / (Qinj + qFevp) (11)
Here, Qtvo is the amount of air passing through the throttle valve 3, 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 expressed by the following equation (12):
AFevp = (qAevp / qFevp) (12)
Is calculated.

The purge flow rate Qevp passing through the canister purge valve 41 is expressed by the following equation (13).

Qevp = qAevp + qFevp (13)
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 (14) is obtained.

14.7 = (Qtvo + qAevp) / (α × Qinj + qFevp) (14)
When Expression (14) is summarized by the air-fuel ratio feedback value α, Expression (15) is obtained.

α = (Qtvo + qAevp) / (14.7 × Qinj) − (qFevp / Qinj) (15)
Since the fuel injection amount Qinj by the injector 12 is adjusted to be the stoichiometric air-fuel ratio 14.7, when the fuel injection amount Qinj (= Qtvo / 14.7) is deleted from the equation (15), the equation (16 ) Is obtained.

α = 1 + (qAevp / Qtvo) − ((14.7 × qFevp / Qtvo)
... (16)
Therefore, the following equation (17) is obtained from the equations (12), (13), and (16).

α = 1 + (Qevp / Qtvo) × ((AFevp−14.7 / AFev + 1))
... (17)
Therefore, if the control purge rate (Qevp / Qtvo) can be controlled to be constant from the equation (17), the purge air-fuel ratio calculating means 306 can calculate the purge air-fuel ratio AFevp based on the air-fuel ratio feedback value α. Further, the purge air-fuel ratio correction value KLMNTC used for correcting the injection pulse has an (AFevp-14.7) / (AFevp + 1) portion of the equation (17) as the estimated value PDEN of the evaporation concentration and the air-fuel ratio feedback value α. Calculated by dividing the deviation (α-1) by the control purge rate (Qevp / Qa).

  The calculation of the purge air-fuel ratio in the purge air-fuel ratio calculation means 306 requires that the control purge rate be kept constant. If this cannot be maintained in the operating state, the calculation and update of the purge air-fuel ratio is stopped, The previous purge air-fuel ratio is maintained. Thereafter, the purge air-fuel ratio is calculated again.

  Next, a method for correcting the fuel injection amount TI by the fuel injection amount calculation means 314 will be described.

  The fuel amount TIEVP for the evaporation is calculated by the following equation (18).

TIEVP = (Qevp / Qtvo) × PDEN × TP × COEF (18)
Here, TP is a basic fuel pulse width, and COEF is a correction amount.

  That is, the deviation (α-1) of the air-fuel ratio feedback value α indicates the current excess / deficiency of the fuel, and 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 discharged 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 the following equation (19).

TI = (TP × COEF × α) −TIEVP
= (TP x COEF x α)
-(Qevp / Qtvo) x PDEN x TP x COEF
= (TP × COEF) × (α− (Qevp / Qtvo) × PDEN)
... (19)
Further, if the base air-fuel ratio learning is performed accurately, the air-fuel ratio feedback value α is converged to around 1.0, and is arranged as α = 1.0 as shown in the equation (20). become.

TI = (TP × COEF) × (1− (Qevp / Qtvo) × PDEN (20)
When the purge air-fuel ratio correction value KLMNTC, which is the evaporation concentration correction value, is used, equation (21) is obtained.

TI = (TP × COEF) × (1-KLMNTC) (21)
Here, KLMNTC is (Qevp / Qtvo) × PDEN.

  Therefore, the fuel injection amount calculation means 314 corrects the fuel injection amount by the air-fuel ratio correction value KLMNTC obtained from the deviation (α-1) of the air-fuel ratio feedback value α based on the equation (21), thereby The influence can be absorbed and fluctuations in the engine air-fuel ratio can be prevented.

  In addition, in the estimation of the evaporated air / fuel ratio, if there is an erroneous estimation for some reason, KLMNTC becomes an abnormal value, and if the fuel injection amount to the engine is abnormally large or abnormally small, it may cause engine failure. Therefore, the air-fuel ratio correction value KLMNTC is limited to a predetermined range.

  Next, a method for updating the learning correction coefficient αm by the air-fuel ratio learning unit 308 of the canister purge control device for the internal combustion engine according to the present embodiment will be described with reference to FIG.

  FIG. 12 is a flowchart showing a method of updating the learning correction coefficient αm by the air-fuel ratio learning means of the internal combustion engine canister purge control apparatus according to one embodiment of the present invention.

  In step S700, the air-fuel ratio learning means 308 confirms the air-fuel ratio learning engine, and proceeds to step S701.

  Next, in step S701, the air-fuel ratio feedback values αa and αb are read from the air-fuel ratio feedback amount calculation means 303, and the process proceeds to step S702.

  Next, a method for calculating the actual injection widths Tea and Teb by the fuel injection amount calculation means 314 of the canister purge control device for an internal combustion engine according to the present embodiment will be described with reference to FIG.

  FIG. 13 is a flowchart showing a method of calculating the actual injection width by the fuel injection correction means of the canister purge control device for an internal combustion engine according to one embodiment of the present invention.

  First, in step S800, the fuel injection amount calculating means 314 reads the engine speed Ne, then in step S601, reads the intake air amount Qa, and then in step S602, the basic fuel is calculated by the following equation (22). The injection amount Tp is calculated.

Tp = Kinj × Qa / Ne (22)
Here, Kinj is an injector injection amount coefficient.

Next, in step S803, after reading various correction coefficients COEF, the fuel injection amount width TIOUT is expressed by equation (23) TIOUT = Tp × COEF (23)
And calculate.

  In step S804, the air-fuel ratio feedback amount calculation unit 303 reads the calculated temporary air-fuel ratio feedback value α.

  Next, in step S805, the purge air-fuel ratio learning value αm calculated by the purge air-fuel ratio calculating means 306 is read, the fuel injection amount TIOUT is corrected, and the actual injection amount Te is calculated by the equation (24). Complete the operation.

Te = TIOUT × (α + αm + KLMNTC) + Ts (24)
Here, Ts is the invalid pulse width of the injector 12. Then, the injector 12 is energized from the I / OLSI 134 based on the actual injection width Te, and fuel is injected. The calculation of the actual injection width in the equation (24) is performed by each of the fuel injection amount calculation means 314.

  As described above, according to the present embodiment, the maximum value of the purge air-fuel ratio is selected from the purge air-fuel ratios estimated from the plurality of air-fuel ratio sensors, and one purge valve is controlled based on this. By suppressing the air-fuel ratio fluctuation in excessive purge, it is possible to sufficiently comply with regulations on automobiles such as North American exhaust gas regulations and run loss regulations.

1 is a system configuration diagram showing the overall configuration of an engine system provided with a canister purge control device of the present invention. The figure which shows the structure of the control unit of the canister purge control apparatus of this invention. The control block diagram which shows the structure of the canister purge control apparatus of this invention. The flowchart which shows operation | movement of the purge period of the canister purge control apparatus of this invention or an air fuel ratio learning period switching means. The flowchart which shows operation | movement of the purge period of the canister purge control apparatus of this invention or an air fuel ratio learning period switching means. The flowchart which shows the purge air-fuel ratio update conditions of the purge period of the canister purge control apparatus of this invention or an air-fuel ratio learning period switching means. The flowchart which showed the purge rate reduction | decrease calculation means of the canister purge control apparatus of this invention. The graph which showed the purge rate reduction | decrease of the canister purge control apparatus of this invention. The flowchart which showed the purge prohibition determination means of the canister purge control apparatus of this invention. The figure which showed the maximum purge rate used for control purge rate calculation of the canister purge control apparatus of this invention. The flowchart which showed the air fuel ratio feedback value calculation method of the canister purge control apparatus of this invention. The flowchart which showed the update method of learning correction coefficient (alpha) m of the air fuel ratio learning means of the canister purge control apparatus of this invention. The flowchart which showed the calculation method of the actual injection width by the fuel-injection correction | amendment means of the canister purge control apparatus of this invention.

Explanation of symbols

7 ... air flow meter (AFM), 11a, 11b ... intake manifold, 12a, 12b ... fuel injection valve (injector), 13 ... fuel tank, 22a, 22b ... O ₂ sensor, 30 ... control unit, 40 ... canister 41 DESCRIPTION OF SYMBOLS ... Canister purge valve, 300 ... Purge control device, 301 ... Intake air amount detection means, 302 ... Exhaust air / fuel ratio detection means, 303 ... Air / fuel ratio feedback amount calculation means, 304 ... Engine speed detection means, 305 ... Target purge rate calculation means 306 ... Purge air / fuel ratio calculating means 307 ... Purge period or air / fuel ratio learning period switching means 308 ... Air / fuel ratio learning calculating means 309 ... Control purge rate calculating means 310 ... Purge rate decrease calculating means 311 ... Excess purge determination Means 312 ... Purge valve opening calculation means 313 ... Purge stop determination means 314 ... Fuel injection amount calculating means.

Claims (7)

Means for detecting the engine intake air amount, means for recovering the fuel evaporated in the fuel tank, evaporation gas purge means for releasing the recovered fuel into the combustion chamber, and control to a predetermined purge amount with respect to the intake air amount A canister purge control device for an internal combustion engine, comprising: target purge rate means for detecting engine air-fuel ratio; means for feeding back from the air-fuel ratio to a preset air-fuel ratio;
A canister purge control for an internal combustion engine, wherein when the air-fuel ratio feedback amount is out of a predetermined range, the target purge rate is decreased at a predetermined rate.   2. A canister purge control apparatus for an internal combustion engine according to claim 1, wherein the purge rate reduction ratio is set to a value based on at least one of an engine operating state, a purge air-fuel ratio, and a target purge rate.   2. The canister purge control device for an internal combustion engine according to claim 1, wherein when the air-fuel ratio feedback amount falls within a predetermined range, the reduced purge rate is restored at a constant rate.   4. The canister purge control device for an internal combustion engine according to claim 2, wherein a recovery rate of the purge rate is made smaller than a decrease rate of the purge rate.   2. The canister purge control apparatus for an internal combustion engine according to claim 1, wherein when the engine speed becomes equal to or less than a predetermined value, the purge amount control of the evaporation gas by the target purge rate means is prohibited.   4. The canister purge control apparatus for an internal combustion engine according to claim 2, wherein when the purge is returned from the purge prohibited state, the purge amount is set to a purge rate immediately before the purge is prohibited. 6. The canister purge control device for an internal combustion engine according to claim 5, wherein when the purge prohibition state has reached a predetermined time or longer, the control for decreasing the target purge rate at a fixed rate is stopped.

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