JP2003074423A - Canister purge control device and method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purging device with purge control and failure diagnosis for a purge valve, capable of improving the responsiveness in purging, securing the purging amount, and not affecting the variation of an air-fuel ratio by the variation of the purge valve, even when the air-fuel ratio is learned and controlled in the canister purge control of an internal combustion engine. SOLUTION: An air-fuel ratio learning period for learning the air-fuel ratio and a purging period for performing the purge are separately provided, and alternately repeated. A small value to a degree not giving the influence on the learning of the air-fuel ration is determined as a purge controlled variable CPCVON in the air-fuel ratio learning period to increase the responsiveness in purging. A set value of the purge valve controlled variable is determined as the purge controlled variable by monitoring the change in the air-fuel ratio and the like when the purge valve is gradually opened. The failure of the purge valve is also diagnosed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a canister purge control device and control method for an internal combustion engine, and in particular,
The present invention relates to a canister purge control device and control method for performing a purge process even during an air-fuel ratio learning period.

[0002]

2. Description of the Related Art As an air-fuel ratio learning control method when purging recovered fuel into an engine, Japanese Patent Laid-Open No. 2000-252 is known.
As disclosed in Japanese Patent Publication No. 761 Gazette, the evaporative purge processing is not interrupted during the progress of the air-fuel ratio learning value, and the purge control amount is a small value that does not affect the air-fuel ratio learning during the air-fuel ratio learning period (fixed. Value), and the method of updating the learning value by air-fuel ratio learning and performing the evaporative purge process alternately has been proposed by the present inventor.

In addition, JP-A-10-115241, JP-A-7-4322, and JP-A-11-107.
Japanese Laid-Open Patent Publication No. 864 discloses a technique of processing evaporated fuel of an engine. In addition, JP-A-10-213022
The publication discloses a failure diagnosis device for evaporative purge.

[0004]

In view of the fact that the evaporative gas is a disturbance of the air-fuel ratio control and the engine air-fuel ratio is disturbed, the purging device taking the evaporative gas into consideration is to prevent the variation on the engine side. The learning value update process based on the air-fuel ratio learning of the base and the evaporative purge process are divided, and the evaporative purge process is interrupted / stopped during the air-fuel ratio learned value update process.

However, in the purge control, it is not desirable to completely interrupt or stop the purge process during the air-fuel ratio learning process. This is because the evaporative gas discharged from the canister returns to the canister and the fuel tank again, which deteriorates the responsiveness of the purge at the next purge control. In other words, when restarting the desired evaporative purge process, the purge flow rate cannot be instantaneously increased.

The return of the evaporative gas to the canister and the fuel tank means that the evaporative gas having a low concentration is released at the beginning of the next purge control, and thereafter,
Since a high concentration of evaporative emission gas can be released, there is a problem that the engine air-fuel ratio suddenly changes due to the evaporative purge treatment.

Up to now, in the purge control for performing the learning value update process by the air-fuel ratio learning and the evaporative purge process,
In order to perform the air-fuel ratio control without interrupting the evaporation purge process even during the update process of the air-fuel ratio learning value, the purge control amount is set to a small value (fixed value) that does not affect the air-fuel ratio learning. It has been found that the various problems can be solved by performing the air-fuel ratio learning control. However, in the above-mentioned conventional technique, while the learning value updating process by the air-fuel ratio learning is being performed, by setting it to be smaller (fixed value) than the purge control amount by the means for controlling the purge flow rate, Although the above-mentioned problem is solved with respect to the purge valve, the above-mentioned problem is not completely solved due to variations in individual purge valves, and no special consideration is given.

On the other hand, the evaporative purge failure diagnosis device disclosed in Japanese Patent Laid-Open No. 10-213022 is for performing a failure diagnosis during deceleration, and requires a device separate from the air-fuel ratio learning means.

The present invention has been made in view of such a problem, and an object thereof is to set the purge control amount during the learning period of the air-fuel ratio as the purge control amount in consideration of the variation of the purge valve. By setting the value according to the calculation method of, the problems such as the deterioration of the purge response due to the variation of the purge valve and the engine air-fuel ratio fluctuation are solved, and the purge response is improved to secure the purge flow rate, and
An object of the present invention is to provide a purge control device and a control method for an internal combustion engine that can suppress fluctuations in the engine air-fuel ratio.

Another object of the present invention is to provide a purge control device and control method for an internal combustion engine, which is capable of diagnosing a purge valve failure with a simple structure.

[0011]

[Means for Solving the Problems] To achieve the above object,
The present invention relates to air-fuel ratio control means for performing feedback control of the air-fuel ratio based on an output signal of means for detecting the air-fuel ratio of an internal combustion engine, an air-fuel ratio learning period for performing air-fuel ratio learning control, and a fuel purge flow rate. In the canister purge control device for an internal combustion engine, comprising: a purge control device that switches a purge period for controlling the purge control amount; and a purge control amount setting means that sets the purge control amount during the learning period of the air-fuel ratio. The control amount setting means gradually increases the purge control amount from the state where the control amount is zero, and calculates the value at the place where the operating state of the internal combustion engine changes by a predetermined value or more as the purge control amount increases as the purge control amount. A purge control amount calculating means is provided for setting the calculated value as the purge control amount during the air-fuel ratio learning period.

In a concrete mode of the purge control apparatus for an internal combustion engine of the present invention, the purge control amount during the learning period of the air-fuel ratio gradually opens from the state of zero control amount, and the air-fuel ratio changes by a predetermined value or more. Is to calculate and set the value of. Or, the calculated value is used as a final value for backup,
It is to store. Alternatively, the control device gradually sets the purge control amount during the learning period of the air-fuel ratio from a state where the control amount is zero, and calculates and sets a value where the air amount in the intake manifold changes by a predetermined value or more. Especially. The calculated value is stored in the backup as the final value.

Alternatively, the control device gradually opens the purge control amount during the learning period of the air-fuel ratio from the state where the control amount is zero, and calculates a value when the deviation of the engine speed changes by a predetermined value or more. Then set. Alternatively, the calculated value is stored in the backup as the final value.

According to the present invention, the purge control amount during the air-fuel ratio learning period is calculated by gradually opening the purge control amount to absorb variations in the purge valve, and to perform an appropriate purge according to each purge valve. The amount can be set.

Another feature of the present invention is that the controller controls the purge control amount during the learning period of the air-fuel ratio in consideration of the response hysteresis of the purge valve in the case of the next start (restart). In order to accelerate the calculation, the purge control amount is gradually opened by starting a value obtained by subtracting a predetermined value from the final value stored as a backup during the air-fuel ratio learning period, and calculating the purge control amount during the air-fuel ratio learning period. , Is set.

As still another specific aspect of the purge control apparatus for an internal combustion engine of the present invention, the control apparatus is configured such that the purge control amount during the learning period of the air-fuel ratio is gradually changed from a state where the control amount is zero. When there is no change in the process of increasing the purge control amount by calculating where the open, air-fuel ratio, air amount, or deviation of the engine speed has changed by a predetermined value or more, A failure of the purge valve can be detected. That is, the failure of the purge valve can be detected by a simple configuration and method using the learning period of the air-fuel ratio. When a failure of the purge valve is detected, the MIL can be turned on to notify the user of the failure. Alternatively, when the control device detects a failure of the purge valve, the air-fuel ratio learning value and the purge control amount during the air-fuel ratio learning period refer to a preset fail-safe value when the user brings the vehicle to the dealer. In addition, the feature is that consideration was given without deteriorating the drivability.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Figure 1
FIG. 1 shows an overall configuration of an engine system including a purge control device for an internal combustion engine of this embodiment.

The internal combustion engine 1 comprises four cylinders 27,
An intake manifold 11 and an exhaust manifold 21 are installed in the cylinder 27, and the intake manifold 11 is configured as a branched intake pipe.

The intake manifold 11 is connected to the air cleaner 2 via the surge tank 9 and the throttle body 5.
The air sucked from the inlet portion 3 of the air cleaner 2 passes through the intake duct 4 and enters the throttle body 5. The throttle body 5 has an air flow meter (AFM) 7 for detecting the intake air amount, a throttle valve 6 for controlling the air flow rate, and a throttle sensor 8 for measuring the opening degree of the throttle valve 6 as appropriate. It is installed in the position. Further, the throttle body 5 is provided with an auxiliary air valve (ISC valve) 10 that bypasses the throttle valve 6, and the air amount is controlled so that the idle speed is kept constant. Then, the air that has passed through the throttle body 5 enters the surge tank 9 and the intake manifold 11
Are distributed by and enter the cylinder 27.

On the other hand, the fuel in the fuel tank 13 is sucked and pressurized by the fuel pump 26, passes through the fuel damper 14 and the fuel filter 15, and is a means for injecting the fuel installed in the intake manifold 11 into the combustion chamber. It is supplied to the fuel injection valve (injector) 12 which is a mode and injected. The fuel pressure acting on this injector 12 is regulated by a fuel pressure regulating valve (pressure regulator) 16, and the negative pressure of the intake manifold 11 is introduced to introduce the fuel pressure and the intake manifold 11 into each other.
The difference from the internal pressure is always kept constant.

Here, the evaporated fuel (evaporative gas) generated in the fuel tank 13 is adsorbed to the canister 40 which is one mode of means for collecting the evaporated fuel through the pipe 46,
It is temporarily collected. The canister 40 is provided with an air introduction port 45 for introducing outside air. During operation of the internal combustion engine 1, the recovered fuel passes through a pipe 47, a canister purge valve 41, which is one mode of a means for discharging the fuel into the combustion chamber, and a pipe 48 together with the air from the air introduction port 45. After being guided to the tank 9, it is supplied to the cylinder 27, and the exhaust of the evaporation gas to the outside is suppressed. The canister 40 is provided with a canister purge cut valve 44, and a negative pressure passage 49 and a negative pressure passage 50 are connected to the canister purge cut valve 44 via the purge cut valve 43. Negative pressure is introduced by energization, release to the surge tank 9 is stopped, and the purge flow rate is adjusted / controlled. The purge flow rate is controlled as a purge rate proportional to the amount of intake air into the internal combustion engine 1 to prevent adverse effects on O2 feedback as described later.

The air-fuel mixture in the cylinder 27 is ignited and burned by the spark plug 18, then sent to the exhaust manifold 21 side, cleaned by the front catalyst 23 and the main catalyst 24, and then discharged through the muffler 25. It At an appropriate position of the exhaust manifold 21, an O2 sensor 22 which is one mode of means for outputting a binary value to detect the engine air-fuel ratio is arranged.

The water temperature for detecting the temperature of the internal combustion engine 1, which is the basic signal for detecting the engine speed, controlling the fuel injection timing and the ignition timing, is the cam angle sensor 17, the air flow meter 7, the throttle sensor 8, and the O2 sensor 22. Signals indicating the engine state of the sensor 20, the fuel tank pressure sensor 51, the fuel temperature sensor 52, etc. are input to an engine control device (control unit) 30 including a purge control device 30a. The control unit 30 performs predetermined arithmetic processing based on these signals to perform various controls such as air-fuel ratio control, and controls the injector 12, ISC valve 10, canister purge valve 41, purge cut valve 43, igniter 19 and the like. Output each drive signal.

FIG. 2 shows the internal structure of the control unit 30. The control unit 30
Controls the MPU 31, the read / write free RAM 32, the read-only ROM 33, and the input / output. I / OLSI34
And are connected by buses 35, 36, and 37, respectively, and each data is exchanged. Specifically, the MPU 60 includes an air flow meter 7, a cam angle sensor 17,
The O2 sensor 22, the fuel temperature sensor 52, and other signals indicating the engine state, which are received from the I / OLSI 34 via the bus 37, sequentially execute the predetermined processing by calling the processing contents stored in the ROM 33, store them in the RAM 32, and then store them again in the I 32 Each drive signal is output from the / OLSI 34 to the injector 12, the canister purge valve 41, the purge cut valve 43, the igniter 19, and the like.

FIG. 3 is a control block diagram of the purge control device 30a. The purge control device 30a performs each process by switching between the base air-fuel ratio learning process due to variations in the internal combustion engine 1 itself and the purge process due to the emission of evaporative gas from the canister 40. In this case, a small amount of evaporative gas is released to the extent that it does not affect the air-fuel ratio learning.

Specifically, the purge control device 30a includes an air-fuel ratio learning period / purge period switching means 30, an air-fuel ratio learning control means 30a1, a purge flow rate control means 30a2, and an air-fuel ratio learning time. It comprises a purge control amount setting means 30E, an air-fuel ratio feedback means 30G, a recovered fuel purge means 30J, and a fuel injection correction means 30I.

As will be described later, the air-fuel ratio learning period / purge period switching means 30A determines whether predetermined conditions such as an air-fuel ratio learning condition and a purge condition are satisfied based on the output signal of the O2 sensor 22 and the like. Then, the period of the air-fuel ratio learning processing by the means 30a1 for learning and controlling the air-fuel ratio and the period of the purge processing by the means 30a2 for controlling the purge flow rate are switched.

The means 30a2 for controlling the purge flow rate includes a purge rate calculating means 30B and a purge period setting means 30C.
And the purge air-fuel ratio calculating means 30F, and the purge period setting means 30C sets the purge period and the like based on the output signal of the air-fuel ratio learning period / purge period switching means 30A, and the purge rate calculating means 30B and Output to the air-fuel ratio feedback means 30G.

The purge rate calculating means 30B has a flow rate Qtvo of the throttle valve 3 and a purge flow rate Qev of the canister 40.
The control purge rate Kevp during the purge period is calculated based on p and output to the purge air-fuel ratio calculation means 30F and the recovered fuel purge means 30J. Then, the recovered fuel purge means 30
J outputs a drive signal to the canister purge 41 based on the purge rate Kevp to cause the evaporative gas to be discharged to the cylinder 27.

The means 30a1 for learning and controlling the air-fuel ratio includes an air-fuel ratio learning period setting means 30D and an air-fuel ratio learning means 30H.
The air-fuel ratio learning period setting means 30D sets the length of the air-fuel ratio learning period based on the output signal of the air-fuel ratio learning period / purge period switching means 30A, and the purge control amount at the time of learning the air-fuel ratio. It outputs to the setting means 30E and the air-fuel ratio feedback means 30G.

The purge control amount setting means for learning the air-fuel ratio and the means 30L for diagnosing the failure of the purge valve are composed of the purge control amount setting 30E for learning the air-fuel ratio and the failure diagnosis 30K for the purge valve. The control amount setting means 30E gradually opens the purge valve during the air-fuel ratio learning process, and sets a value at a place where the air-fuel ratio or the like has changed by a predetermined value or more as the purge control amount.
The purge control amount is a small value that does not affect the learning of the air-fuel ratio.
Output to. Then, the recovered fuel purge means 30J outputs a drive signal to the canister purge 41 based on the purge control amount, and causes the evaporation gas to be released to the cylinder 27.

The purge valve failure diagnosis 30K detects a failure of the purge valve when the air-fuel ratio or the like does not change by a predetermined value or more when calculating and setting the purge control amount during the air-fuel ratio learning period. The MIL is turned on by the failure display means to notify the failure. Further, in this case, the fail-safe value set in advance is referred to for the air-fuel ratio learning value and the purge control amount by the failure control means.

The air-fuel ratio feedback means 30G uses O2
The air-fuel ratio feedback control is performed so that the actual air-fuel ratio of the exhaust gas discharged from the combustion chamber by the sensor 22 becomes the target air-fuel ratio, and the purge period, the air-fuel ratio learning period, etc. are input, which is a temporary amount. The air-fuel ratio feedback value α is calculated and output to the purge air-fuel ratio calculation means 30F, the air-fuel ratio learning means 30H, and the fuel injection correction means 30I.

The purge air-fuel ratio calculation means 30F of the means 30a2 for controlling the purge flow rate estimates the purge air-fuel ratio AFevp and the purge air-fuel ratio correction KLMNTC on the basis of the air-fuel ratio feedback value α and the purge rate Kevp, and It outputs to the injection correction means 30I. At this time, as will be described later, learning of the engine air-fuel ratio is stopped.

The air-fuel ratio learning means 30H of the means 30a1 for learning and controlling the air-fuel ratio performs learning so that the correction amount by the air-fuel ratio feedback means 30G becomes a predetermined value in order to perform air-fuel ratio feedback control. The learning correction value αm is calculated based on the air-fuel ratio feedback value α and is output to the fuel injection correction means 30I.

The fuel injection correction means 30I is a fuel injection setting means 3 based on the engine speed Ne and the intake air amount Qa.
The basic injection amount of 0b is corrected, and the air-fuel ratio feedback value α by the air-fuel ratio feedback means 30G is
Learning correction value αm by the air-fuel ratio learning means 30H and purge air-fuel ratio correction KLMN by the purge air-fuel ratio calculation means 30F.
The basic injection amount is corrected based on the three correction values by TC, and the corrected injection amount is output to the injector 12.

FIG. 4 is a purge control device 3 for learning the air-fuel ratio.
It is an operation flowchart of 0a, the purge control device 30
In a, the air-fuel ratio learning process by means 30a1 for learning and controlling the air-fuel ratio and the purge process by means 30a2 for controlling the purge flow rate are alternately repeated.

In step 100, the air-fuel ratio learning period / purge switching means 30A determines whether or not the air-fuel ratio feedback condition is satisfied after the engine is started.

When the air-fuel ratio is in the feedback state such as not in the fuel cut state or the load is stable, that is, in the case of YES, the routine proceeds to step 101. on the other hand,
This operation is repeated when the air-fuel ratio feedback condition is not satisfied.

In step 101, the air-fuel ratio learning period / purge switching means 30A determines whether or not the air-fuel ratio learning condition is satisfied, and if the load is more stable and the air-fuel ratio learning state is in effect. , That is, when YES,
Proceeding to step 102, the air-fuel ratio learning period setting means 30D
To the base air-fuel ratio learning period, and step 10
Go to 3. On the other hand, when the air-fuel ratio learning condition is not satisfied, this operation is repeated.

At step 103, the air-fuel ratio learning means 30
When the air-fuel ratio learning is performed at H, the learning number counter KLCONT of the corresponding area is incremented by 1 and the process proceeds to step 104.

In step 104, the purge rate KLevp is set by the purge control amount 30E at the time of learning the air-fuel ratio, the purge control amount is determined and output to the recovered fuel purge means 30J, and the routine proceeds to step 105. This purge rate KLevp is
The purge rate is such that the air-fuel ratio learning is not impaired, and the purging process is performed during the air-fuel ratio learning period. The method of calculating the purge rate KLevp will be described with reference to FIG.

In step 105, it is judged whether or not the learning number counter KLCONT is larger than the cumulative number KLCNT of the air-fuel ratio learning, and the learning number counter KL.
When CONT is larger than the cumulative number KLCNT of the air-fuel ratio learning, that is, when it is YES, the end of the base air-fuel ratio learning is determined and the routine proceeds to step 106.

In step 106, the air-fuel ratio feedback means 30G learns the air-fuel ratio of the rich and lean O2 sensors 22 for a predetermined number of cycles LRNCNT, and during this period, the air-fuel ratio feedback means 30G and the air-fuel ratio learning. The fuel injection correction means 30I corrects the injection pulse based on the output signal of the means #H. Then O
2 It is determined whether or not the number of rich and lean cycles of the sensor 22 reaches a predetermined number of times LRNCNT, and the predetermined number of times LRNCNT is determined.
If it becomes CNT, that is, if YES, the routine proceeds to step 107 to shift to the purge period. on the other hand,
In step 105, the cumulative number KLCNT of the air-fuel ratio learning
If it is smaller than the above, or if it is not the predetermined number of times LRNCNT in step 106, the air-fuel ratio learning period has not yet ended, so the routine proceeds to step 102, and the above-mentioned respective operations are repeated. That is, the air-fuel ratio learning period is set to a period proportional to the rich and lean cycles.

In step 107, the air-fuel ratio learning period / purge period switching means 30A determines whether or not the purge condition is satisfied. If the purge condition is satisfied, that is, if YES, the process proceeds to step 108. Then, the purge period setting means 30C is switched to, purge valve control is performed, and the process proceeds to step 109. On the other hand, when the purge condition is not satisfied, this operation is repeated. The purge valve control in step 108 will be described later with reference to FIGS. 5 and 10.

At step 109, learning of the air-fuel ratio is prohibited and the routine proceeds to step 110. At the fuel recovery purging means 30J, the purge rate calculating means 30B reaches the target value of step 110 based on the set rate of increase. The control purge rate is increased, the purge flow rate by the canister purge valve 41 is gradually increased to release the recovered fuel, and step 11
Go to 1. The purge rate control in step 110 will be described later with reference to FIGS. 7 and 8.

In step 111, the purge air-fuel ratio calculation means 30F causes the purge air-fuel ratio AFevp (evaporation concentration).
Is calculated, the purge air-fuel ratio fuel correction value KLMNTC is calculated and stored, and the process proceeds to step 112, in which the fuel injection correction means 30I uses the output signals of the air-fuel ratio feedback means 30G and the purge air-fuel ratio calculation means 30F, The injection pulse is corrected according to the purge air-fuel ratio, and the routine proceeds to step 113.

In step 113, it is determined whether the number of rich and lean cycles of the O2 sensor 22 has reached the predetermined number LRNCNT. If the number of times reaches the predetermined number LRNCNT, that is, if YES, the air-fuel ratio learning period is entered. To proceed to step 102. On the other hand, a predetermined number of times LR
If it is not NCNT, the purge period has not ended yet, so the routine proceeds to step 108, and the above-mentioned operations are repeated. That is, the purge period is also set to a period proportional to the rich and lean cycles.

FIG. 5 shows an embodiment of the purge valve control (step 108 in FIG. 4) by the purge control amount setting means 30E at the time of learning the air-fuel ratio in FIG. First, the purge control amount C
The PCVON is calculated and set by gradually opening the purge control amount from the state where the control amount is zero and operating the internal combustion engine, for example, the air-fuel ratio (α) 60, the intake air amount (Qa) 61 in the intake manifold, the engine. Rotational speed deviation (ΔNe) 62,
When any of the above has changed by a predetermined value or more, that is, when the purge flow rate Qevp63 has started to flow, the purge control amount CPCV
ON65 is calculated and set as the purge control amount during the air-fuel ratio learning period. By this calculation method, the appropriate purge control amount CPC according to the variation of each purge valve can be obtained.
Since the VON 65 can be set, variations in purge valves can be absorbed, the responsiveness of purge cannot be increased at the time of the next purge control, the purge flow rate cannot be instantaneously increased, and problems such as deterioration of the engine air-fuel ratio due to the evaporation purge process can be solved. it can.

The set value CPCVON65 is stored in the backup as the final value so that the backup value C can be saved at the next start (restart) as shown in FIG.
Subtract a predetermined value Z from PCVON65, and obtain that value CPCVO
Starting from N64, the purge control amount is gradually opened, and the purge control amount in the air-fuel ratio learning period is calculated and set to consider the response hysteresis of the purge valve and to determine the purge control amount during the air-fuel ratio learning period. Can be calculated and set early.

FIG. 6 shows an embodiment of failure diagnosis means for the purge valve. The purge valve failure diagnosis and detection method includes:
When calculating the purge control amount CPCVON65 during the air-fuel ratio learning period, when the purge valve control amount CPCVON (for example, 30%) is increased to CPCVON66 and the air-fuel ratio (α) 60 or the like does not change by a predetermined value or more, the purge valve When a failure is detected and the MIL is turned on, the user is notified of the abnormality. Further, in this case, the air-fuel ratio learning value and the purge control amount CPCVON during the air-fuel ratio learning period are referred to the preset fail-safe value, so that the user can drive the vehicle even when the user brings the vehicle to the dealer. Care should be taken so that the items can be brought in without deteriorating. The purge valve failure detection is performed in step 409 of FIG. 10 described later.
Is processed in.

7 and 8 are explanatory views of the operation (step 110 in FIG. 4) of the purge rate calculating means 30B of the means 30a2 for controlling the purge flow rate. The purge rate calculation means 3
0B first determines the target purge rate, and then calculates the control purge rate.

The target purge rate is, as shown in FIG.
The purge air-fuel ratio is large, that is, the estimated value P of the evaporation concentration
When the DEN 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 and set to a low value. The former is
This is to prevent the introduction of excess negative pressure into the A / F lean and the fuel tank 13 due to empty purging, and the latter is to prevent deterioration of drivability when the evaporation concentration is high, such as during heat damage traveling. Is. Then, the target purge rate is set high at an intermediate value of the purge air-fuel ratio to earn the purge flow rate.

Next, the control purge rate is the ratio (Q of the purge flow rate Qevp to the intake air amount Qa of the internal combustion engine 1).
evp / Qa), and the purge control amount is obtained from this.

Here, while the intake air amount Qa changes 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 increases as the intake air amount Qa increases. Is decreased and is kept constant, and when the suction pipe negative pressure approaches the atmospheric pressure, the purge flow rate Qevp is decreased. Therefore, in this case as well, the controlled purge rate is not kept constant. Therefore, as shown in FIG. 8, when the canister purge valve 41 is fully opened (valve DUTY1 by referring to the maximum purge rate map obtained from the engine speed and load).
(00%), the control purge rate is set in advance to maintain the purge rate constant.

Thus, the control duty for the canister purge valve 41 can be obtained by dividing the control purge rate by the purge rate calculating means 30B by the maximum purge rate. Since it is difficult to flow a purge flow rate higher than the maximum purge rate, the control purge rate by the purge rate calculating means 30B is limited by the maximum purge rate.

FIG. 9 is a flow chart for calculating the air-fuel ratio feedback value α by the air-fuel ratio feedback means 30G shown in FIG.

In step 300, when the output of the O2 sensor 22 is Rich (the engine air-fuel ratio is small) or Richi, the routine proceeds to step 302. When Rich, that is, the engine air-fuel ratio is small, the output of the O2 sensor 22 is about 0.8v, while when Lean, that is, when the engine air-fuel ratio is large, the output of the O2 sensor 22 is about 0.2v. This output value and a predetermined value (0.5
Rich judgment or Lea by comparing v)
n determination has been made.

In step 302, the fully opened processing state is checked. That is, it is determined whether or not the previous time was Rich, and when the previous time is not Rich, that is, when the previous time when the result is NO is the Lean state, the current time is Lean.
Since this means that the state has changed from the Rich state to the Rich state, proportional control (subtraction) is performed as shown in the equation (1) that has proceeded to step 303, and the procedure proceeds to step 308.

Α = α-ARP (1) Here, ARP is the proportional correction amount at the time of Rich, and the data is stored in the ROM 33.

On the other hand, if the previous time is the Rich state, that is, YES, the routine proceeds to step 304, where integral control (subtraction) is performed as shown in the equation (2), and then the routine proceeds to step 308.

Α = α-ARI (2) Here, ARI is the integral correction amount at the time of Rich, and the data is stored in the ROM 33.

In step 305, similarly to step 302, the previous processing state is checked. That is, it is determined whether or not the previous time was Rich, and if the previous time was Rich, that is, if YES, this time from Rich to L
Since the state has changed to ean, step 30
Proportional control (addition) is performed as shown in the equation (3) that has proceeded to step 3, and step 308 follows.

Α = α-ALP (3) Here, ALP is the proportional correction amount at the time of Reah, and the data is stored in the ROM 33.

On the other hand, in step 305, the previous time is Rich.
If not, go to step 307 and use equation (4)
Integral control (addition) is performed as shown in step 308.
Proceed to.

Α = α + ALI (4) Here, ALI is the integral correction amount at the time of Rean, and the data is stored in the ROM 33.

In step 308, the above step 30 is performed.
3, step 304, step 306 or step 30
The air-fuel ratio feedback value α obtained in 7 is stored in the RAM 3
2 and then proceeds to step 309, where step 309
Then, in the present embodiment, αave after the averaging processing of each air-fuel ratio feedback value α is obtained by the weighted averaging processing, and the series of operations is ended.

Next, the purge air-fuel ratio calculating means 30F will be described. First, the influence 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 27 is given by the equation (5).
Is calculated as follows.

AFcy1 = (Qtvo + qAevp) / (Qinj + qFevp) (5) where Qtvo is the amount of air passing through the throttle valve 3, Qinj is the amount of fuel injected by the injector 12, and qAevp is fresh air passing through the canister 40. , QFevp is the amount of fuel leaving the canister 40.

Further, the purge air-fuel ratio AFevp is calculated by the equation (6). AFevp = (qAevp / qFevp) (6) Then, the purge flow rate Qevp passing through the canister purge valve 41 is expressed by the equation (7).

Qevp = qAevp + qFevp (7) Here, in the system, the air-fuel ratio feedback is controlled so that the engine air-fuel ratio AFcy1 becomes the theoretical air-fuel ratio 14.7, so the air-fuel ratio feedback value α Then, it becomes like Formula (8).

14.7 = (Qtvo + qAevp) / (α × Qinj + qFevp) (8) When formula (8) is summarized by the air-fuel ratio feedback value α, formula (9) is obtained.

Α = (Qtvo + qAevp) / (14.7 × Qinj)-(qFevp / Qinj) (9) Then, the fuel injection amount Qinj by the injector 12
Is adjusted so that the stoichiometric air-fuel ratio becomes 14.7.
From the equation (9), the fuel injection amount Qinj (= Qtvo / 14.
Eliminating 7) yields equation (10).

Α = 1 + (qAevp / Qtvo)-((14.7 × qFevp / Qtvo) (10) Therefore, the equations (6), (7), and (10) are obtained from the equation (11).

Α = 1 + (Qevp / Qtvo) × ((AFevp-14.7 / AFevp + 1) ... (11) Therefore, from the equation (11), 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 purge air-fuel ratio correction value KLMNTC used for the correction of the injection pulse is expressed by (11) AF
evp-14.7) / (AFevp + 1) is the estimated value PDEN of the evaporation concentration, and the deviation (α-1) of the air-fuel ratio feedback value α is divided by the control 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 amount is calculated by the equation (12).

TIEVP = (Qevp / Qtvo) × PDEN × COEF ... (12) 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) indicates the current injection scheduled fuel (TP × CO).
By multiplying EF), the fuel amount TIEV for the evaporation amount
P will be calculated.

Therefore, even if the canister purge valve 41 is opened and the evaporative emission gas is released to the surge ton 9, it can be understood that the engine air-fuel ratio can be kept constant by reducing the fuel amount TIEVP for the evaporation amount from the fuel injection amount TI. This can be expressed as in Expression (13), and if the base air-fuel ratio learning is performed accurately, the air-fuel ratio feedback value α is converged to around 1.0, and α
Equation (14) is obtained by rearranging as 1.0. Then, the purge air-fuel ratio correction value K that is the correction value of the evaporation concentration
If LMNTC is used, it becomes like a formula (15).

TI = (TP × COEF × α) −TIEV = (TP × COEF × α) − (Qevp / Qtvo) × PDEN × TP × COEF = (TP × COEF) × (α− (Qevp / Qtvo) × (13) TI = (TP × COEF) × (1- (Qevp / Qtvo) × PDEN …… (14) TI = (TP × COEF) × (1-KLMNTC) ………… (15) This KLMNTC is (Qevp / Qtvo) × PDEN
Is.

Therefore, based on this equation (15), 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, the effect of the evaporation amount can be absorbed. Therefore, the fluctuation of the engine air-fuel ratio can be prevented.

FIG. 10 shows means 30 for learning and controlling the air-fuel ratio.
a1 and purge control amount setting means 30 during the air-fuel ratio learning period
It is a flowchart of L.

At step 400, the air-fuel ratio learning period by the air-fuel ratio learning period setting means 30D is confirmed, and the routine proceeds to 401, where the purge control amount setting means 30E for air-fuel ratio learning sets the purge control amount during the air-fuel ratio learning period. However, if it is the first time, that is, if YES, the routine proceeds to step 402, 2
In the case of the first time (restart), that is, in the case of NO, the routine proceeds to step 403.

After proceeding to steps 402 and 403, in step 404, the condition for calculating the purge control amount during the air-fuel ratio learning period, (the air-fuel ratio has changed by a predetermined value or more = the condition is satisfied) is confirmed, that is, YES. Then step 40
5, the purge control amount is set during the air-fuel ratio learning period.

After that, the purge control amount set in step 405 is stored in the backup 406 as the final value, and then the process returns to the first step.

If the calculation condition (the air-fuel ratio etc. does not change by a predetermined value or more) is not satisfied in step 404, that is, if NO, the routine proceeds to step 409, where a failure of the purge valve is detected and the MIL is turned on (see FIG. 6).

Furthermore, when a failure is detected, the routine proceeds to step 410, at which the air-fuel ratio learning value and the purge control amount during the air-fuel ratio learning period are referred to the fail-safe value, and the process ends.

FIG. 11 is a flowchart for calculating the actual injection width Te by the fuel injection setting means 30b and the fuel injection correction means 30I.

First, at step 500, the engine speed Ne is read by the fuel injection setting means 30b and the routine proceeds to step 501. At step 501, the intake air amount Q
The value a is read and the process proceeds to step 502. Then, at step 502, the basic injection amount Tp is calculated as in equation (16), and the process proceeds to step 503. Cage air-fuel ratio calculation means Tp = Kinj × Qa / Ne (16) where Kinjha injector injection amount coefficient.

At step 503, various correction factors CO
After reading EF, the fuel injection width TIOUT is calculated as shown in Expression (17), and the routine proceeds to step 504.

TIOUT = Tp × COEF (17) Next, at step 504, the temporary air-fuel ratio feedback value α calculated by the air-fuel ratio feedback means 30G is read. Up to this point, the learning control does not include vapor.

Next, the routine proceeds to step 505, where it is calculated by the purge air-fuel ratio calculating means 30F (step 11 in FIG. 4).
1) The purge air-fuel ratio correction value KLMNTC for the purge period is read and the process proceeds to step 506. At step 506, the air-fuel ratio learning value αm for the learning period calculated by the air-fuel ratio learning means 30H is read, and the fuel injection correction means 30I
At, the fuel injection width TIOUT is corrected, the actual injection width Te is calculated as shown in equation (18), and the series of operations is ended.

Te = TIOUT × (α + am + KLMNTC) + Ts (18) where Ts is the invalid pulse width of the injector 12. The I / OL is calculated based on the actual injection width Ts.
From S134, the injector 12 is energized and fuel is injected.

As described above, the embodiment of the present invention has the following functions due to the above configuration.

That is, the purge control device 30a for an internal combustion engine according to the present embodiment comprises an air-fuel ratio learning period / purge switching means 30A, an air-fuel ratio learning control means 30a1.
A means 30a2 for controlling the purge flow rate, a purge control amount setting means 30E for learning the air-fuel ratio, a failure diagnosis means 30K for the purge valve, an air-fuel ratio feedback means 30G, a fuel injection correction means 30I, and a recovered fuel purge means 30J. The purge control amount setting means 30E for learning the air-fuel ratio does not affect the air-fuel ratio learning even during the air-fuel ratio learning process by the purge control amount setting means capable of absorbing the variation of the purge valve. With a suitable purge control amount of a certain degree, for example, a small amount of evaporative gas is released so that the value of the O2 sensor 22 does not change, so the evaporative gas in the pipe 48 or the like is returned to the canister 40 and the fuel tank 13. Without increasing the purging responsiveness during the purging period to secure the purging flow rate. It is possible to suppress the fluctuation of the engine air-fuel ratio to release the evaporative gas of constant concentration. Further, the purge control amount setting means 30E during the air-fuel ratio learning period uses the change of the air-fuel ratio and the like during the purge valve control as the calculation condition, and therefore the purge valve failure diagnosis 30K is also possible.

In the purge control device 30a, the air-fuel ratio learning period / purge switching means 30A switches between the base air-fuel ratio learning process and the purge process under a predetermined cycle without interrupting the evaporation gas discharge. By alternately and repeatedly ensuring the accuracy of the air-fuel ratio learning and ensuring the purge flow rate, it is possible to sufficiently comply with the regulations on the automobile, such as the North American LEV regulation and the run loss regulation.

Further, the purge control device 30a prohibits learning of the air-fuel ratio during the purge period by the means 30a2 for controlling the purge flow rate, and controls the purge flow rate after the end of the air-fuel ratio learning period. 30a2 is switched to the purge period, the air-fuel ratio learning period is prioritized over the purge period, and the purge control is performed after all the variations on the internal combustion engine 1 side are learned, so that the accuracy of the air-fuel ratio learning is further improved. It is possible to improve.

Further, the air-fuel ratio learning period setting means 30D and the purge period setting means 30C of the purge control device 30a.
Since the air-fuel ratio learning period and the purge period are set to a period proportional to the rich and lean periods of the air-fuel ratio, it is possible to perform switching according to each operating state such as idle time and normal time. High accuracy air-fuel ratio learning can be achieved.

Further, means 30a2 for controlling the purge flow rate
The purge air-fuel ratio calculation means 30F of the purge air-fuel ratio AFev is based on the air-fuel ratio feedback value α during the purge period.
Since p is estimated, it is possible to realize the purge control in which the fluctuation of the engine air-fuel ratio is further reduced.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment,
Various modifications can be made in the design without departing from the spirit of the invention described in the claims.

[0101]

As can be understood from the above description, the canister purge control system for an internal combustion engine according to the present invention performs the air-fuel ratio learning control in consideration of the variation of the purge valve even during the engine air-fuel ratio learning process. Since the evaporative gas is released to the extent that it does not affect, it is possible to secure the purge flow rate during the purge period and to suppress the fluctuation of the engine air-fuel ratio.

Further, since the purge control amount setting means during the air-fuel ratio learning period uses the change of the air-fuel ratio and the like during the purge valve control as the calculation condition, it is possible to diagnose the purge valve failure with a simple structure.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine system including a purge control device for an internal combustion engine of the present embodiment.

FIG. 2 is an internal configuration diagram of a control unit including the purge control device of FIG.

FIG. 3 is a control block diagram of the purge control device of FIG.

4 is an operation flowchart of the purge control device in FIG.

FIG. 5 is a specific explanatory diagram of the purge control amount calculation and setting during the air-fuel ratio learning period of the purge control device of FIG.

6 is an explanatory diagram of a purge valve failure diagnosis detection method of the purge control apparatus of FIG.

FIG. 7 is an explanatory diagram of calculation of a target purge rate during a purge period by the purge rate calculation means in the purge control apparatus of FIG.

8 is a maximum purge rate map during a purge period by the purge rate calculating means in the purge control apparatus of FIG.

9 is a flowchart for calculating an air-fuel ratio feedback value by air-fuel ratio feedback means in the purge control device of FIG.

FIG. 10 is a flowchart at the time of learning correction coefficient updating and purge valve failure diagnosis by means of air-fuel ratio learning control in the purge control apparatus of FIG.

11 is a flowchart for calculating a fuel injection width such as fuel injection correction means in the purge control device of FIG.

[Explanation of symbols]

12 means for injecting fuel into the combustion chamber (injector) 13 fuel tank 22 means for detecting engine air-fuel ratio (O2 sensor) 30a purge control device 30al means for learning control of air-fuel ratio 30a2 means for controlling the purge flow rate of fuel 30A empty Means 30B for switching the fuel ratio between learning control and purge control 30C for calculating the fuel purge rate 30C For setting the fuel purge period 30D For setting the air-fuel ratio learning period 30E Purge control amount during the air-fuel ratio learning period Means 30F means for estimating the purge air-fuel ratio during the fuel purge period 30G means for performing feedback control of the air-fuel ratio 30H means for learning the air-fuel ratio 30I means for correcting the fuel injection amount 40 means for recovering the evaporated fuel (Canister) 41 Means for releasing fuel into the combustion chamber (canister purge valve)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 45/00 F02D 45/00 340F 362 362J (72) Inventor Shinsaku Tsukada 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Incorporated company Hitachi Ltd. Automotive equipment group (72) Inventor Kazuya Saito 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Incorporated Hitachi Ltd. Automotive equipment group (72) Inventor Heikichi Kamoshida 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi Car Engineering Co., Ltd. (72) Inventor Yoshiaki Nagasawa 2477 Takaba, Hitachinaka City, Ibaraki Prefecture F Term in Hitachi Car Engineering Co., Ltd. (reference) 3G044 BA08 BA16 BA22 EA03 EA35 EA40 EA44 EA49 EA55 FA08 FA27 FA28 GA02 3G084 BA09 BA13 BA27 DA12 EA11 EB06 EB20 FA07 FA29 FA 33 3G301 HA01 HA14 JA04 JB09 JB10 LB01 MA01 MA11 ND21 NE03 PA01Z PD02Z PE02Z

Claims (9)

[Claims] 1. An air-fuel ratio control means for performing feedback control of the air-fuel ratio based on an output signal of a means for detecting an air-fuel ratio of an internal combustion engine, an air-fuel ratio learning period for performing air-fuel ratio learning control, and fuel purging. A canister purge control device for an internal combustion engine, comprising: a purge control device for switching a purge period for controlling a flow rate; and a purge control amount setting means for setting the purge control amount during a learning period of the air-fuel ratio, The purge control amount setting means gradually increases the purge control amount from the state of zero control amount, and the value at the place where the operating state of the internal combustion engine changes by a predetermined value or more as the purge control amount increases is set as the purge control amount. A canister purge control system for an internal combustion engine, comprising: a purge control amount calculation means for calculating, and setting the calculated value as a purge control amount during the air-fuel ratio learning period. Apparatus. 2. The canister purge control device according to claim 1, wherein the purge control amount setting means gradually increases the purge control amount from a state in which the control amount is zero, and the purge control amount of the internal combustion engine is changed according to the change of the purge control amount. A value at a place where the air-fuel ratio has changed by a predetermined value or more is calculated, and the calculated value is used as the purge control amount during the air-fuel ratio learning period,
A canister purge control device for an internal combustion engine, which is stored in a backup means as a final value. 3. The canister purge control device according to claim 1, wherein the purge control amount during the air-fuel ratio learning period is gradually increased from the state in which the control amount is zero, and is accompanied by a change in the purge control amount. A value at a place where the amount of air in the intake manifold of the internal combustion engine has changed by a predetermined value or more is calculated, and the calculated value is used as the purge control amount during the air-fuel ratio learning period,
A canister purge control device for an internal combustion engine, which is stored in a backup means as a final value. 4. The canister purge control device according to claim 1, wherein the purge control amount during the air-fuel ratio learning period gradually increases the purge control amount from a state where the control amount is zero, and is accompanied by a change in the purge control amount. A value at a place where the deviation of the engine speed changes by a predetermined value or more is calculated, and the calculated value is set as the purge control amount during the air-fuel ratio learning period,
A canister purge control device characterized by storing the final value in a backup means. 5. The canister purge control device according to claim 2, wherein the purge control amount setting means sets the purge control amount during the air-fuel ratio learning period when the internal combustion engine is next started. Starting from a value obtained by subtracting a predetermined value from the final value stored in the backup means during the learning period of the air-fuel ratio, the purge control amount is gradually opened, and the purge control amount during the air-fuel ratio learning period is calculated. A canister purge control device for an internal combustion engine, comprising: 6. The canister purge control device according to claim 1, further comprising means for diagnosing a failure of the purge valve, wherein the air-fuel ratio learning value and the air-fuel ratio when the purge valve fails. The canister purge control device for an internal combustion engine, wherein the control purge control amount during the learning period refers to a fail value. 7. The canister purge control device according to claim 6, wherein when the purge valve fails during calculation of the purge control amount during the air-fuel ratio learning period, the purge control amount is increased in the process of increasing the purge control amount. A canister purge control device for an internal combustion engine, which detects a failure of the purge valve and notifies the user of an abnormality when the operating state of the internal combustion engine has not changed. 8. The canister purge control device according to claim 6 or 7, wherein the air-fuel ratio learning value and the purge control amount during the air-fuel ratio learning period are preset when the purge valve fails. A canister purge control device for an internal combustion engine, which refers to a fail-safe value. 9. An air-fuel ratio control means for performing feedback control of the air-fuel ratio based on an output signal of a means for detecting an air-fuel ratio of an internal combustion engine, an air-fuel ratio learning period for performing air-fuel ratio learning control, and fuel purging. A canister purge control method for an internal combustion engine, comprising: a purge control device that switches a purge period for controlling a flow rate; and a purge control amount setting means that sets the purge control amount during the learning period of the air-fuel ratio. By the purge control amount setting means, the purge control amount is gradually increased from the zero control amount state, and the value at which the operating state of the internal combustion engine changes by a predetermined value or more as the purge control amount increases is taken as the purge control amount. A canister purge control method for an internal combustion engine, comprising calculating and setting the value of the purge control amount as a purge control amount during the air-fuel ratio learning period.