JP2002070659A - Purge control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purge control device for an internal combustion engine capable of securing a purge flow rate by setting a purge control quantity even during a learning period of an air-fuel ratio to improve the responsiveness of purge, and of restraining the variation of an engine air-fuel ratio. SOLUTION: This purge control device for an internal combustion engine is provided with a means for recovering fuel vaporized in a fuel tank and a means for discharging the recovered fuel to a combustion chamber. The control device is provided with a means for executing the feedback control of the air-fuel ratio based on an output signal of a means for detecting the air-fuel ratio, a means for learning and controlling the air-fuel ratio, a means for controlling the purge flow rate of the fuel, and a means for setting the purge control quantity during the learning period of the air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a purge control device for an internal combustion engine, and more particularly to a purge control device for an internal combustion engine that performs an evaporative purge process even when learning the air-fuel ratio of the engine to suppress fluctuations in the engine air-fuel ratio.

[0002]

2. Description of the Related Art In general, some internal combustion engines perform an evaporative purge process in which, in addition to fuel supply by a fuel injection valve, evaporated fuel (evaporated gas) generated in a fuel tank is released and supplied to an intake system. It is known that, in the evaporative purge process, after the evaporative gas is collected and adsorbed in a canister, the evaporative gas is discharged into the intake system by introducing outside air into the canister.

In this case, since it is necessary to control the air-fuel ratio of the fuel from the evaporative purge process and the fuel from the fuel injection valve, various technologies relating to a purge control device considering the evaporative gas have been proposed. (For example, JP-A-7-151020, JP-A-8-28370, JP-A-9-32610, JP-A-2000-73885, and JP-A-11-2.
94269, JP-A-7-139398).

The purge control apparatus described in Japanese Patent Application Laid-Open No. H7-151020 interrupts the evaporative purge process based on the air-fuel ratio by evaporative gas and learns the air-fuel ratio. The above-described purge control device ensures the stability of the air-fuel ratio by selectively performing either an update process of a learning value by air-fuel ratio learning or an evaporative purge process. The purge control device disclosed in the official gazette prohibits learning of the air-fuel ratio based on the air-fuel ratio feedback correction value when the air-fuel ratio is affected by the evaporative purge process.

The purge control apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-73885 corrects the air-fuel ratio based on the calculation of the concentration of the evaporative gas.
The purge control device disclosed in Japanese Patent Application Laid-Open No. Hei 7-139398 learns the purge concentration based on the air-fuel ratio feedback correction value and the actual air-fuel ratio during execution of the evaporative purge process. The purge control device of the first embodiment reduces the air-fuel ratio feedback correction initial value when the evaporative purge process is started, and increases the correction initial value when the evaporative purge process is completed.

[0006]

By the way, the purging control device considering the evaporative gas is designed to prevent the evaporative gas from being disturbed in the air-fuel ratio control and causing the engine air-fuel ratio to be disturbed. The process is divided into a process of updating a learning value based on air-fuel ratio learning and a process of evaporative purge with respect to the variation of the air-fuel ratio, and the process of updating the air-fuel ratio learning value is interrupted and stopped.

However, in the purge control, it is not desirable to completely interrupt / 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, so that the purge response is deteriorated at the next purge control. That is, there is a problem that the purge flow rate cannot be instantaneously increased when the desired evaporative purge process is restarted.

Further, the return of the evaporative gas to the canister and the fuel tank means that, when the next purge control is started, a thin concentration of the evaporative gas is released first, and thereafter a dense concentration of the evaporative gas can be released. Another problem is that the engine air-fuel ratio is suddenly changed by the evaporative purge process.

That is, in the purge control for performing the learning value update process based on the air-fuel ratio learning and the evaporative purge process, the present inventor does not interrupt the evaporative purge process even during the air-fuel ratio learned value update process. New knowledge has been obtained that the above problems can be solved by performing fuel ratio control. However, in the above-described conventional technique, the evaporative purge process is interrupted and stopped while the process of updating the learning value by the air-fuel ratio learning is performed. However, no special consideration is given to simultaneous execution of the learning value updating process by the air-fuel ratio learning and the evaporation purge process.

The present invention has been made in view of such a problem, and an object thereof is to set a purge control amount even during an air-fuel ratio learning period to improve purge responsiveness. It is an object of the present invention to provide a purge control device for an internal combustion engine that can secure a purge flow rate and suppress fluctuations in the engine air-fuel ratio.

[0011]

In order to achieve the above object,
A purge control apparatus for an internal combustion engine according to the present invention basically includes a means for recovering fuel evaporated in a fuel tank and a means for discharging the recovered fuel to a combustion chamber. The control device includes: a unit that performs feedback control of the air-fuel ratio based on an output signal of the unit that detects the air-fuel ratio; a unit that performs learning control of the air-fuel ratio; and a unit that controls a purge flow rate of the fuel. Means for setting the purge control amount during the learning period of the air-fuel ratio.

In the purge control apparatus for an internal combustion engine according to the present invention configured as described above, the means for setting the purge control amount during the learning period of the air-fuel ratio interrupts the evaporative gas emission even during the air-fuel ratio learning control. Instead, the purge control amount is set, and the fuel is constantly discharged, so that the purge responsiveness can be improved, the purge flow rate can be secured, and the fluctuation of the air-fuel ratio can be suppressed.

In a specific aspect of the purge control apparatus for an internal combustion engine according to the present invention, the means for setting the purge control amount during the learning period of the air-fuel ratio controls the purge control amount and the purge flow rate. It is characterized in that it is set smaller than the purge control amount by means.

In another specific aspect 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 does not change the actual air-fuel ratio by the means for detecting the air-fuel ratio. Or the control device inhibits the learning of the air-fuel ratio during the purge period by the means for controlling the purge flow rate, or the control device controls the air-fuel ratio from the means for detecting the air-fuel ratio. Setting the learning period of the air-fuel ratio and the purge period by the means for controlling the purge flow rate based on the rich and lean cycles of the air conditioner, or the control device is configured to output the air-fuel ratio based on an output signal of the air-fuel ratio detecting means. Switching between the means for learning control of the air-fuel ratio and the means for controlling the purge flow rate, or after the learning period of the air-fuel ratio ends, It is characterized in that switching to purge period by means of controlling the purge flow rate.

Still another specific aspect of the purge control device for an internal combustion engine according to the present invention is that the control device performs feedback control of the air-fuel ratio, learning control of the air-fuel ratio, and The fuel injection amount of the means for injecting fuel into the combustion chamber is corrected based on each output signal of the means for controlling the purge flow rate.

Further, the means for controlling the purge flow rate includes:
Estimating the purge air-fuel ratio during the purge period by the means for controlling the purge flow rate based on the output signal of the means for performing the feedback control of the air-fuel ratio, or the control device performs the control during the purge period. Correcting the fuel injection amount of the means for injecting fuel into the combustion chamber based on the estimated purge air-fuel ratio, or controlling the purge flow rate, when the purge air-fuel ratio is estimated for the first time, The first purge period is set to be longer than the other purge periods, or the means for controlling the purge flow rate is a means for discharging the fuel to the combustion chamber when the estimation of the purge air-fuel ratio is the first time. The controller estimates the purge air-fuel ratio by gradually increasing the purge flow rate to a target value, or the controller determines that the purge air-fuel ratio is higher than the target value when the purge air-fuel ratio is estimated for the second time or later. The purge air-fuel ratio after the first purge period is set to the final value of the purge air-fuel ratio in the previous purge period, or the control device determines that the purge flow rate by the means for controlling the purge flow rate is less than or equal to a predetermined value and the predetermined period has elapsed. In this case, the purge air-fuel ratio for the second and subsequent times is reset, and in the next purge period, the purge flow rate of the means for discharging the fuel to the combustion chamber is gradually increased to a target value to estimate the purge air-fuel ratio. It is characterized by doing.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a purge control apparatus for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows an overall configuration of an engine system including a purge control device for an internal combustion engine according to the present embodiment. The internal combustion engine 1 includes four cylinders 27, in each of which the intake manifold 11 and the exhaust manifold 21 are installed. The intake manifold 11 is configured as a branched intake pipe.

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

On the other hand, the fuel in the fuel tank 13 is sucked and pressurized by a fuel pump 26, passes through a fuel damper 14, a fuel filter 15, and injects fuel installed in the intake manifold 11 into a combustion chamber. The fuel is supplied to a fuel injection valve (injector) 12, which is an embodiment, and is injected. The fuel pressure acting on the injector 12 is regulated by a fuel pressure regulating valve (pressure regulator) 16 to introduce a negative pressure of the intake manifold 11 so that the difference between the fuel pressure and the pressure in the intake manifold 11 is always constant. Holding.

Here, the evaporated fuel (evaporated gas) generated in the fuel tank 13 passes through a pipe 46 and is adsorbed by a canister 40 which is an embodiment of a means for collecting the evaporated fuel.
Collected temporarily. The canister 40 is provided with an air introduction port 45 for introducing outside air. During the operation of the internal combustion engine 1, the recovered fuel is supplied to the surge tank via the pipe 47, the canister purge valve 41 which is one mode of a means for discharging fuel to the combustion chamber, and the pipe 48 together with the air from the air inlet 45. After being guided to 9, the gas is supplied to the cylinder 27, and the discharge of the evaporative gas to the outside is suppressed. The canister 40 is provided with a canister purge cut valve 44. The canister purge cut valve 44 is connected to the negative pressure passage 49 and the negative pressure passage 5 through the purge cut valve 43.
0 is connected, a negative pressure is introduced by energization of the purge cut valve 43, the discharge to the surge tank 9 is stopped, and the purge flow rate is adjusted and controlled. The purge flow rate is controlled as a purge rate proportional to the amount of intake air to the internal combustion engine 1 so as to prevent an adverse effect on O2 feedback as described later.

The air-fuel mixture in the cylinder 27 is ignited and burned by the ignition plug 18, sent to the exhaust manifold 21 side, purified by the front catalyst 23 and the main catalyst 24, and then discharged through the muffler 25. You. Exhaust manifold 21
An O2 sensor 22, which is an embodiment of a means for outputting a binary value and detecting the engine air-fuel ratio, is disposed at an appropriate position in FIG.

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

FIG. 2 shows the internal configuration of the control unit 30. The control unit 30
Are an MPU 31, a read / write RAM 32, a read-only ROM 33, and an I / OLSI 34 for controlling input / output.
, And are connected by buses 35, 36, and 37, respectively, and exchange data. Specifically, the MPU 60 includes an air flow meter 7, a cam angle sensor 17,
After receiving signals indicating the engine state, such as the O2 sensor 22 and the fuel temperature sensor 52, from the I / O LSI 34 via the bus 37, the processing contents stored in the ROM 33 are sequentially called, predetermined processing is performed, and stored in the RAM 32. The drive signals are output again from the I / 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 a base air-fuel ratio learning process based on variations in the internal combustion engine 1 itself,
Each process is performed by switching between the purge process and the purge process based on the release of evaporative gas from the canister 40. During the air-fuel ratio learning process, a small amount of evaporative gas is released so as not to affect the learning of the air-fuel ratio. Is going.

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

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 an output signal of the O2 sensor 22 and the like, as described later. The period of the air-fuel ratio learning process by the air-fuel ratio learning means 30a1 and the period of the purge process by the purge flow rate controlling means 30a2 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 a purge air-fuel ratio calculating unit 30F. The purge period setting unit 30C sets the length of the purge period and the like based on the output signal of the air-fuel ratio learning period / purge period switching unit 30A. 30B and output to the air-fuel ratio feedback means 30G.

The purge rate calculating means 30B calculates the purge air flow Qev of the canister 40 and the airflow Qtvo passing through the throttle valve 3.
The control purge rate Kevp during the purge period is calculated based on p, and is output to the purge air-fuel ratio calculation means 30F and the recovered fuel purge means 30J. Then, the recovered fuel purging means 30
J outputs a drive signal to the canister purge valve 41 based on the purge rate Kevp to reduce the amount of evaporative gas to the cylinder 2.
Release to 7.

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 sets the purge control amount at the time of air-fuel ratio learning. Output to setting means 30E and air-fuel ratio feedback means 30G.

A purge control amount setting means 30 for learning the air-fuel ratio.
E sets a purge control amount during the air-fuel ratio learning process. The purge control amount is a small value that does not impair the learning of the air-fuel ratio (for example, the valve DUTY is about 7%). The purge control amount is output to the recovered fuel purge means 30J. Then, the recovered fuel purge means 30J outputs a drive signal to the canister purge valve 41 based on the purge control amount to discharge the evaporative gas to the cylinder 27.

The air-fuel ratio feedback means 30G is provided with O2
Feedback control of the air-fuel ratio 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 a purge period, an air-fuel ratio learning period, and the like are input, and a temporary period is input. 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 calculating 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 value KLMNTC based on the air-fuel ratio feedback value α and the purge rate Kevp. Output to the fuel injection correction means 30I. At this time, as will be described later, the learning of the engine air-fuel ratio is stopped.

The air-fuel ratio learning means 30H of the air-fuel ratio learning means 30a1 performs learning so that the correction amount by the air-fuel ratio feedback means 30G becomes a predetermined value in order to perform feedback control of the air-fuel ratio. 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 correcting means 30I includes a fuel injection setting means 3 based on the engine speed Ne and the intake air amount Qa.
0b, the air-fuel ratio feedback value α by the air-fuel ratio feedback means 30G.
The learning correction value αm by the air-fuel ratio learning means 30H and the purge air-fuel ratio correction value KL by the purge air-fuel ratio calculation means 30F
The basic injection amount is corrected based on three correction values and the like by the MNTC and output to the injector 12.

FIG. 4 is a flowchart showing the operation of the purge control device 30a. The purge control device 30a includes an air-fuel ratio learning process by means of learning control of the air-fuel ratio 30a1 and a purge process by means 30a2 of controlling the purge flow rate. And are alternately repeated.

In step 100, the air-fuel ratio learning period / purge period switching means 30A determines whether or not the air-fuel ratio feedback condition is satisfied after the engine is started. Not in fuel cut condition, stable load, etc.
When in the air-fuel ratio feedback state, that is, YES
In step, the process proceeds to step 101. On the other hand, when the air-fuel ratio feedback condition is not satisfied, this operation is repeated.

In step 101, the air-fuel ratio learning period / purge period switching means 30A determines whether the air-fuel ratio learning condition is satisfied, and the air-fuel ratio learning state is established such that the load is more stable. In this case, that is, if YES, the routine proceeds to step 102, where the air-fuel ratio learning period setting means 30D is switched to the base air-fuel ratio learning period, and the routine proceeds to step 103. On the other hand, when the air-fuel ratio learning condition is not satisfied, this operation is repeated.

In step 103, the air-fuel ratio learning means 30
When the air-fuel ratio learning is performed at H, the learning counter KLCONT of the corresponding area is counted up by one, and the routine proceeds to step 104. In step 104, the purge rate KLevp is set by the purge control amount setting means 30E during the air-fuel ratio learning.
Is set, the purge control amount is determined and output to the recovered fuel purge means 30J, and the routine proceeds to step 105. The purge rate KLevp is a purge rate that does not impair the air-fuel ratio learning, and the purge process is performed during the air-fuel ratio learning period.

In step 105, it is determined whether or not the learning number counter KLCONT is larger than the integrated number KLCNT of the air-fuel ratio learning.
If CONT is greater than the cumulative number of times of air-fuel ratio learning KLCNT, that is, if 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 predetermined number LRNCNT of rich and lean cycles of the O2 sensor 22, and during this time, the air-fuel ratio feedback means 30G and the air-fuel ratio learning means The injection pulse is corrected by the fuel injection correction means 30I based on the output signal of 30H. Thereafter, it is determined whether or not the number of rich and lean cycles of the O2 sensor 22 has reached the predetermined number LRNCNT. If the number of times has reached the predetermined number LRNCNT, that is, if YES, the process proceeds to step 107 to shift to the purge period. On the other hand, if it is determined in step 105 that the number of times of the air-fuel ratio learning is smaller than the cumulative number KLCNT,
If the predetermined number of times is not LRNCNT, the process proceeds to step 102 because the air-fuel ratio learning period has not yet ended, 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.

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 process is switched to the purge period setting means 30C to set the purge period, and the process proceeds to step 109. On the other hand, when the purge condition is not satisfied, this operation is repeated.

In step 109, the air-fuel ratio learning is inhibited and the routine proceeds to step 110. In step 110, the purge period setting means 30C sets the purge period during the first purge period before the calculation of the evaporative concentration based on the estimation of the purge air-fuel ratio. If it is the first purge period, that is, if YES, the routine proceeds to step 111, where the first purge period is made longer than the other purge periods, and the purge rate calculation means 30B and the air-fuel ratio feedback are performed. Output to means 30G. Then, the control purge rate by the purge rate calculation means 30B is increased by the recovered fuel purge means 30J based on the set increase rate until the target value of step 112 is reached, and the purge flow rate by the canister purge valve 41 is gradually increased. Then, the collected fuel is released, and the routine proceeds to step 113. On the other hand, when it is not the first purge period in step 110, the recovered fuel is purged by the recovered fuel purging means 30J at the purge flow rate based on the set purge rate as the target value in step 112 without increasing the purge flow rate. Proceed to 113.

At step 113, the purge air-fuel ratio AFevp (evaporation concentration) is calculated by the purge air-fuel ratio calculating means 30F.
Is calculated, and a purge air-fuel ratio fuel correction value KLMNTC is calculated, and the routine proceeds to step 114, where the purge air is corrected by the fuel injection correction unit 30I based on the output signals of the air-fuel ratio feedback means 30G and the purge air-fuel ratio calculation means 30F. Step 115 corrects the injection pulse according to the fuel ratio.
Proceed to.

In step 115, it is determined whether or not the number of rich and lean cycles of the O2 sensor 22 has reached a predetermined number LRNCNT. If the number of times has reached the predetermined number LRNCNT, that is, if YES, the process proceeds to the air-fuel ratio learning period. Go to step 102 for this. On the other hand, the predetermined number of times LR
If it is not NCNT, since the purge period has not ended yet, the process proceeds to step 108, and the above operations are repeated. That is, the purge period is also set to a period proportional to the rich and lean cycles.

FIGS. 5 and 6 are explanatory diagrams of the purge rate calculating means 30B of the means 30a2 for controlling the purge flow rate.
The purge rate calculating means 30B first determines a target purge rate, and then calculates a control purge rate. As shown in FIG. 5, the target purge rate is set 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. The former is to prevent the A / F lean due to the empty purge and the introduction of an extra negative pressure to the fuel tank 13, and the latter is to deteriorate the drivability when the evaporative concentration is high such as during heat damage driving. This is to prevent And
The target purge rate is set high at an intermediate value of the purge air-fuel ratio, and the purge flow rate is obtained.

Next, the control purge rate is determined by the ratio of the purge flow rate Qevp to the intake air amount Qa of the internal combustion engine 1 (Qe
vp / Qa), whereby the purge control amount is obtained. Here, while the intake air amount Qa changes greatly depending on the traveling state, the purge flow rate Qev
Since p is limited to the maximum flow rate of the canister purge valve 41, the control purge rate decreases with an increase in the intake air amount Qa and is kept constant, and further, when the intake pipe negative pressure approaches the atmospheric pressure, Since the purge flow rate Qevp decreases, the control purge rate is not maintained constant in this case as well. Therefore, as shown in FIG.
The control purge rate when the canister purge valve 41 is fully opened (valve Duty 100%) is set in advance with reference to a maximum purge rate map obtained from the engine speed and the load, and the purge rate is kept constant.

Thus, the control duty for the canister purge valve 41 can be obtained by dividing the control purge rate by the purge rate calculation means 30B by the maximum purge rate. Since it is difficult to flow a purge flow rate equal to or greater than the maximum purge rate, the control purge rate by the purge rate calculation means 30B is limited by the maximum purge rate. FIG. 7 shows the air-fuel ratio feedback means 3.
It is a flowchart of calculation of an air-fuel ratio feedback value α by 0G. In step 300, the output of the O2 sensor 22 is read, and the routine proceeds to step 301.

In step 301, the output of the O2 sensor 22 is set to Rich (the engine air-fuel ratio is small) or Lean.
(The engine air-fuel ratio is large), and if the output of the O2 sensor 22 is Rich, the process proceeds to step 302. On the other hand, if the output of the O2 sensor 22 is lean, the process proceeds to step 305. Note that when Rich, that is, the engine air-fuel ratio is small, the output of the O2 sensor 22 is about 0.8 V, while when Lean, that is, the engine air-fuel ratio is large, the output of the O2 sensor 22 is about 0.2 V.
v, this output value and a predetermined value (about 0.5 v)
Are compared, a Rich determination or a Lean determination is made.

In step 302, the previous processing state is checked. That is, it is determined whether or not the previous time was Rich. If the previous time was not Rich, that is, if the previous time, which is NO, was in the lean state, the current
Since the state has changed from “Rich” to “Rich”, the process proceeds to step 303 to perform proportional control (subtraction) as shown in equation (1), and then proceeds to step 308.

[0050]

Α = α−ARP (1) Here, ARP is a proportional correction amount at the time of Rich, and data is stored in the ROM 33. On the other hand, step 30
If the previous state is the Rich state, that is, if YES in step 2, the process proceeds to step 304 to perform integral control (subtraction) as shown in equation (2), and then proceeds to step 308.

[0051]

Α = α-ARI (2) Here, ARI is an integral correction amount at the time of Rich, and data is stored in the ROM 33. In step 305, as in step 302, the previous processing state is checked. That is, it is determined whether or not the last time was Rich. If the last time was Rich, that is, if YES, it means that the state has changed from Rich to Lean this time, so the process proceeds to step 303 and is expressed by equation (3). As described above, the proportional control (addition) is performed, and the process proceeds to step 308.

[0052]

Α = α + ALP (3) Here, ALP is a proportional correction amount at the time of Lean, and data is stored in the ROM 33. On the other hand, step 30
If the previous time is not in the Rich state in step 5, step 3
07, the integral control (addition) is performed as shown in equation (4).
And the process proceeds to step 308.

[0053]

Α = α + ALI (4) Here, ALI is an integral correction amount at the time of lean, and data is stored in the ROM 33. In step 308, steps 303, 304, 3
06 or the air-fuel ratio feedback value α obtained in step 307 is stored in the RAM 32, and the process proceeds to step 309. In step 309, in the present embodiment, the weighted average processing is performed to smooth the air-fuel ratio feedback value α. Αa
ve is obtained, and a series of operations ends.

Next, the purge air-fuel ratio calculating means 30F will be described. First, the effect of the evaporative gas on the air-fuel ratio to the internal combustion engine 1 will be described below. The engine air-fuel ratio AFcyl based on the air-fuel mixture supplied into the cylinder 27 is calculated as in equation (5).

[0055]

AFcyl = (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. The amount of air, qFevp, is the amount of fuel desorbed from the canister 40. Further, the purge air-fuel ratio AFevp is calculated as in equation (6).

[0056]

AFevp = qAevp / qFevp (6) The purge flow rate Qevp passing through the canister purge valve 41 is expressed by equation (7).

[0057]

Qevp = qAevp + qFevp (7) Here, in the system, the air-fuel ratio feedback is controlled so that the engine air-fuel ratio AFcyl becomes the stoichiometric air-fuel ratio of 14.7. Then, Expression (5) becomes Expression (8).

[0058]

## EQU8 ## 14.7 = (Qtvo + qAevp) / (α × Qinj + qFevp) (8) Formula (8) is summarized by formula (9) using air-fuel ratio feedback value α.

[0059]

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 equation (9), the fuel injection amount Qinj (= Qtvo / 14.
Eliminating 7) gives equation (10).

[0060]

Α = 1 + (qAevp / Qtvo) − ((14.7 × qFevp) / Qtvo) (10) Therefore, Expression (11) is obtained from Expressions (6), (7) and (10). can get.

[0061]

Α = 1 + (Qevp / Qtvo) × ((AFevp−14.7) / (AFevp + 1)) (11) Therefore, from the equation (11), the control purge rate (Qevp) is obtained.
/ 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 correcting the injection pulse is also O2 as described above.
It can be estimated from the value of α of the feedback.

That is, the purge air-fuel ratio correction value KLMNTC
Is (AFevp-14.7) / (AFe
vp + 1) as the estimated value PDEN of the evaporative concentration,
It is calculated by dividing the deviation (α-1) of the air-fuel ratio feedback value α 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 is calculated by the equation (1).
It is calculated as in 2).

[0063]

TIEVP = (Qevp / Qtvo) × PDEN × TP × COEF (12) where 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 excess or deficiency of the current fuel, the deviation (α-1) includes the current fuel to be injected (TP ×
COEF), the fuel amount TI of the evaporation amount is obtained.
EVP will be calculated.

Therefore, even if the canister purge valve 41 is opened and the evaporative gas is discharged to the surge tank 9,
It is understood that the engine air-fuel ratio can be kept constant by reducing the fuel amount TIEVP for the evaporation from the fuel injection amount TI. This can be expressed as in equation (13). Further, if the base air-fuel ratio learning is correctly performed, the air-fuel ratio feedback value α is considered to converge to around 1.0. Equation (14) is obtained by rearranging as 1.0. When the purge air-fuel ratio correction value KLMNTC, which is a correction value of the evaporation concentration, is used, Expression (15) is obtained.

[0065]

(13) TI = (TP × COEF × α) −TIEVP = (TP × COEF × α) − (Qevp / Qtvo) × PDEN × TP × COEF = (TP × COEF) × (α− (Qevp / Qtvo) × PDEN) (13) TI = (TP × COEF) × (1- (Qevp / Qtvo) × PDEN) (14) TI = (TP × COEF) × (1-KLNMTC) (15) This KLMNTC is (Qevp / Qtvo) × PDEN
It is.

Therefore, if the fuel injection amount is corrected by the purge air-fuel ratio correction value KLMNTC obtained from the deviation (α-1) of the air-fuel ratio feedback value α based on the equation (15), the influence of the evaporation is absorbed. Thus, fluctuations in the engine air-fuel ratio can be prevented. In the estimation and calculation of the purge air-fuel ratio and the like, as shown in FIG. 8, if the canister purge valve 41 is opened from the closed state to the target value at a stretch, the air-fuel ratio feedback value α cannot follow and becomes stable. During this period, it can be seen that the engine air-fuel ratio fluctuates and the exhaust performance deteriorates.

Therefore, as shown in FIG. 9, the purge control device 30a of the present embodiment sets the purge air-fuel ratio AFevp and the purge air-fuel ratio correction value KLMNTC corresponding to the estimated value PDEN of the first evaporative concentration to the canister purge valve 41. The fuel injection amount is gradually opened at a constant rate, and is estimated and calculated from the deviation of the air-fuel ratio feedback value α at each time to correct the fuel injection amount, thereby maintaining the engine air-fuel ratio at a stoichiometric ratio. The air-fuel ratio feedback value α is reset to 1.0 for each correction, and as described above, the purge duty of the canister purge valve 41 is gradually increased to the target value, and the purge duty once reaches the target value.
Even after the purge air-fuel ratio AFevp is estimated, the purge air-fuel ratio AFevp is updated at predetermined intervals with the deviation of the air-fuel ratio feedback value α, and the current purge air-fuel ratio AFevp is always estimated.

It should be noted that the above-described purge control for increasing at a constant rate is performed by calculating the first purge air-fuel ratio AFevp. Except for this, the control for opening the canister purge valve 41 at a stretch to achieve the target purge rate is performed. Do. This is because if the purge control for increasing the flow rate at a constant rate is always performed, the purge flow rate may not be secured.

That is, after the first estimation of the purge air-fuel ratio, the canister purge valve 41 is opened and the purge air-fuel ratio AF estimated and calculated during the previous purge period is simultaneously measured.
The fluctuation of the engine air-fuel ratio is prevented by correcting the fuel injection pulse based on the final value of the purge air-fuel ratio correction value KLMNTC based on evp.

On the other hand, when the purge flow time equal to or less than the predetermined value becomes longer, the evaporative gas in the fuel tank 13 is adsorbed in the canister 40, and the current purge air-fuel ratio AFevp for obtaining the purge air-fuel ratio correction value KLMNTC is compared with the previous purge air-fuel ratio AFevp. Since a difference occurs with the purge air-fuel ratio AFevp, if the closing time of the canister purge valve 41 exceeds a predetermined value, the estimated purge air-fuel ratio AFevp is reset, and in the next purge period, as described above, The purge air-fuel ratio AFevp is estimated again by increasing the purge flow rate to a target value at a constant rate, and the purge air-fuel ratio correction value KLMNTC is calculated based on this.

FIG. 10 shows a means 30 for learning and controlling the air-fuel ratio.
a1 learning correction coefficient α by air-fuel ratio learning control means 30H
It is a flowchart until it updates m. In 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 step 401, where the purge control amount for air-fuel ratio learning by the purge control amount setting means 30E for air-fuel ratio learning is set and collected. The signal is output to the fuel purge means 30J and the like, and the routine proceeds to step 402.

In step 402, the average value αa of the air-fuel ratio feedback value α is obtained by the air-fuel ratio feedback 30G.
ve, the process proceeds to step 403, and step 40
In 3, the air-fuel ratio learning means 30H updates the air-fuel ratio learning correction coefficient αm of the area and ends a series of operations.

FIG. 11 is a flowchart for calculating the actual injection width Te by the fuel injection setting means 30b and the combustion 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 Qa is read, and the routine proceeds to step 502. Then, in step 502, the basic injection amount T is calculated as in equation (16).
Calculate p and go to step 503.

[0074]

Tp = Kinj × Qa / Ne (16) where Kinj is an injector injection amount coefficient. In step 503, after reading various correction coefficients COEF, the fuel injection width TIOUT is calculated as shown in the equation (17), and the process proceeds to step 504.

[0075]

[Expression 15] TIOUT = Tp × COEF (17) Next, in step 504, the temporary air-fuel ratio feedback value α calculated by the air-fuel ratio feedback means 30G is read, and the flow advances to step 505. Then, the purge air-fuel ratio correction value KLMNTC for the purge period calculated by the purge air-fuel ratio calculation means 30F is read, and the process proceeds to step 506. In 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 width TIOUT is corrected by the combustion injection correction means 30I.
The actual injection width Te is calculated, and the series of operations ends.

[0076]

[Expression 16] Te = TIOUT × (α + αm + KLMNTC) + Ts (18) Here, Ts is an invalid pulse width of the injector 12. Then, based on the actual injection width Te, the I / O
Electric power is supplied from the LSI 34 to each injector 12, and fuel is injected. As described above, the embodiment of the present invention has the following functions by the above configuration.

That is, the purge control device 30a for the internal combustion engine of the present embodiment includes an air-fuel ratio learning period / purge switching means 30A, a means 30a1 for learning control of the air-fuel ratio, a means 30a2 for controlling the purge flow rate, and an air-fuel ratio It has a purge control amount setting means 30E for learning, an air-fuel ratio feedback means 30G, a fuel injection correction means 30I, and a recovered fuel purge means 30J, and the purge control amount setting means 30E for learning the air-fuel ratio is provided. To the extent that the learning of the air-fuel ratio is not affected during the air-fuel ratio learning process, for example,
Since a small amount of evaporative gas is released so that the value of the O2 sensor 22 does not change, the evaporative gas in the pipe 48 or the like is not returned to the canister 40 and the fuel tank 13, and the responsiveness of the purge during the purge period is improved. It is possible to secure the purge flow rate by improving the pressure, and furthermore, it is possible to constantly discharge the evaporative gas of a constant concentration and suppress the fluctuation of the engine air-fuel ratio.

The purge control device 30a switches the air-fuel ratio learning process and the purge process of the base at predetermined intervals by the air-fuel ratio learning period / purge switching means 30A without interrupting the evaporative gas release. By alternately and repeatedly ensuring the accuracy of the learning of the air-fuel ratio and the securing of the purge flow rate, it is possible to sufficiently comply with the regulations for automobiles, for example, the North American LEV regulations and the run-loss regulations.

The purge control device 30a prohibits the learning of the air-fuel ratio during the purge period by the purge flow rate controlling means 30a2, and controls the purge flow rate after the end of the air-fuel ratio learning period. The purge period is switched to the purge period 30a2, the air-fuel ratio learning period is prioritized over the purge period, and the purge control is performed after learning all variations on the internal combustion engine 1 side. Therefore, the accuracy of the air-fuel ratio learning is further improved. Can be achieved.

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 periods that are proportional to the rich and lean cycles of the air-fuel ratio, it is possible to perform switching according to each operation state such as idling and normal operation. Thus, highly accurate air-fuel ratio learning can be achieved.

The means 30a2 for controlling the purge flow rate
The purge air-fuel ratio calculating means 30F calculates the purge air-fuel ratio AFev 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.

When the estimation of the purge air-fuel ratio by the purge air-fuel ratio calculation means 30F is the first time, the purge calculation means 30B and the purge period setting means 30C gradually increase the control purge rate and set the purge period to be long. Therefore, it is possible to improve the convergence of the estimation of the purge air-fuel ratio by the purge air-fuel ratio calculation means 30F, and to eliminate the estimation error.

Although the embodiment of the present invention has been described in detail, the present invention is not limited to the embodiment, and various designs may be made without departing from the spirit of the invention described in the appended claims. Can be changed.

[0084]

As can be understood from the above description, the purge control apparatus for an internal combustion engine according to the present invention discharges the evaporative gas also during the engine air-fuel ratio learning process. And the fluctuation of the engine air-fuel ratio can be suppressed.

[Brief description of the drawings]

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

FIG. 2 is an internal configuration diagram of a control unit including the purge control device of FIG. 1;

FIG. 3 is a control block diagram of the purge control device of FIG. 1;

FIG. 4 is an operation flowchart of the purge control device of FIG. 1;

FIG. 5 is an explanatory diagram of calculation of a target purge rate during a purge period by a purge rate calculation unit in the purge control device of FIG. 1;

FIG. 6 is a maximum purge rate map of a purge period by a purge rate calculation unit in the purge control device of FIG. 1;

FIG. 7 is a flowchart of calculating an air-fuel ratio feedback value by an air-fuel ratio feedback unit in the purge control device of FIG. 1;

FIG. 8 is an explanatory diagram of a conventional purge air-fuel ratio estimation.

FIG. 9 is an explanatory diagram of a purge air-fuel ratio estimation by a purge air-fuel ratio calculation unit in the purge control device of FIG. 1;

FIG. 10 is a flowchart until a learning correction coefficient is updated by means for learning control of an air-fuel ratio in the purge control device of FIG. 1;

FIG. 11 is a flowchart of a fuel injection width calculation by a combustion injection correction means and the like in the purge control device of FIG. 1;

[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 30a1 Means for Learning and Controlling Air-Fuel Ratio 30a2 Means for Controlling Fuel Purge Flow Rate 30A Empty Means for switching between fuel ratio learning control and purge control 30B Means for calculating fuel purge rate 30C Means for setting fuel purge period 30D Means for setting air-fuel ratio learning period 30E Purge control during air-fuel ratio learning period Means for setting the amount 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 Recovering the evaporated fuel Means (Canister) 41 Means for releasing fuel into the combustion chamber (Canister Valve)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (reference) F02D 43/00 301 F02D 43/00 301M 45/00 368 45/00 368G F-term (reference) 3G044 AA05 BA08 BA29 DA02 DA08 EA04 EA12 EA13 EA23 EA26 EA40 EA44 EA49 FA04 FA08 FA13 FA15 FA20 FA27 3G084 AA00 BA09 BA13 BA27 DA12 EA11 EB11 EB19 EB20 EC06 FA20 FA26 FA33 3G301 HA01 HA14 JA03 JA04 LA00 LB02 PE04ZA04 ND04

Claims (14)

[Claims] 1. A purge control apparatus for an internal combustion engine, comprising: means for recovering fuel evaporated in a fuel tank; and means for discharging the recovered fuel to a combustion chamber. The control apparatus detects an air-fuel ratio. Means for performing feedback control of the air-fuel ratio, means for learning control of the air-fuel ratio, means for controlling the purge flow rate of the fuel, and setting of the purge control amount during the learning period of the air-fuel ratio based on the output signal of the means for performing the Means for purging an internal combustion engine. 2. The method according to claim 1, wherein the means for setting a purge control amount during the learning period of the air-fuel ratio sets the purge control amount to be smaller than a purge control amount by the means for controlling the purge flow rate. Item 2. A purge control device for an internal combustion engine according to Item 1. 3. The internal combustion engine according to claim 1, wherein the purge control amount during the learning period of the air-fuel ratio is set to such an extent that the actual air-fuel ratio by the means for detecting the air-fuel ratio does not change. Purge control device. 4. The control device according to claim 1, wherein the control device inhibits learning of the air-fuel ratio during a purge period by means for controlling the purge flow rate. A purge control device for an internal combustion engine. 5. The control device sets a learning period of the air-fuel ratio and a purge period by the unit that controls the purge flow rate based on a rich and lean cycle from the unit that detects the air-fuel ratio. 5. The method according to claim 1, wherein:
A purge control device for an internal combustion engine according to any one of the preceding claims. 6. The controller according to claim 1, wherein the controller switches between a means for learning control of the air-fuel ratio and a means for controlling the purge flow rate based on an output signal of the means for detecting the air-fuel ratio. The purge control device for an internal combustion engine according to any one of claims 1 to 5. 7. The apparatus according to claim 1, wherein the control device switches to a purge period by means for controlling the purge flow rate after the end of the learning period of the air-fuel ratio. A purge control device for an internal combustion engine. 8. The control device according to claim 1, wherein the control device controls the air-fuel ratio based on output signals of the means for performing feedback control of the air-fuel ratio, the means for learning control of the air-fuel ratio, and the means for controlling the purge flow rate. The purge control apparatus for an internal combustion engine according to any one of claims 1 to 7, wherein a fuel injection amount of an injection unit is corrected. 9. The method according to claim 9, wherein the means for controlling the purge flow rate estimates a purge air-fuel ratio during a purge period by the means for controlling the purge flow rate based on an output signal of the means for performing feedback control of the air-fuel ratio. A purge control device for an internal combustion engine according to any one of claims 1 to 8, characterized in that: 10. The controller according to claim 9, wherein the controller corrects a fuel injection amount of a means for injecting fuel into a combustion chamber based on the estimated purge air-fuel ratio during the purge period. A purge control apparatus for an internal combustion engine according to claim 1. 11. The method according to claim 11, wherein when the purge air-fuel ratio is estimated for the first time, the first purge period is set longer than other purge periods. The purge control apparatus for an internal combustion engine according to claim 9 or 10. 12. The method of controlling the purge flow rate, wherein, when the purge air-fuel ratio is estimated for the first time, the purge flow rate of the means for discharging the fuel to the combustion chamber is gradually increased to a target value to increase the purge air-fuel ratio. The purge control device for an internal combustion engine according to any one of claims 9 to 11, wherein a fuel ratio is estimated. 13. The controller according to claim 1, wherein, when the purge air-fuel ratio is estimated for the second time or later, the controller sets the purge air-fuel ratio for the second time or later to the final value of the purge air-fuel ratio in the previous purge period. The purge control device for an internal combustion engine according to any one of claims 10 to 12, wherein: 14. The controller according to claim 1, wherein when the purge flow rate by the control means for controlling the purge flow rate is equal to or less than a predetermined value and a predetermined period has elapsed, the second and subsequent purge air-fuel ratios are reset. 14. The purge control apparatus for an internal combustion engine according to claim 13, wherein during the purge period, the purge air-fuel ratio is estimated by gradually increasing the purge flow rate of the means for discharging the fuel to the combustion chamber to a target value.