JPH0723706B2 - Evaporative fuel processor for engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an evaporated fuel processing apparatus for an engine, which supplies evaporated fuel to an intake system.

(Prior Art) In order to prevent evaporative fuel generated in a fuel tank or a float chamber of a carburetor from leaking to the atmosphere, an automobile engine normally uses evaporative fuel in a canister containing an adsorbent such as activated carbon. An evaporative fuel treatment device is provided which is once adsorbed and collected, and is separated (purged) by suction negative pressure during engine operation and introduced into the intake system.

In such an evaporated fuel processing device, normally, a control valve that responds to a negative pressure in a VC hole opens a purge passage when a throttle valve is slightly opened, so that evaporated fuel is released and sucked.
Further, the supply of the evaporated fuel to the intake system may be stopped in some specific operating conditions other than during idling. For example, when such an evaporated fuel processing device is used in an engine equipped with a feedback air-fuel ratio control device for performing learning control, the amount of evaporated fuel supplied to the intake system varies and the air-fuel ratio changes. Since the influence exerted is not constant, in order to prevent erroneous learning, it is necessary to temporarily stop the supply of evaporated fuel during learning. Also, in the case where the feedback control device is also provided, when the O ₂ sensor detects an abnormal state such as sticking to the lean side or the rich side due to disconnection or short circuit, a large amount of evaporated fuel is supplied even if there is no abnormality. _{2 In} some cases, the phenomenon of sticking of the sensor occurred, so it is necessary to temporarily cut off the evaporated fuel. If the evaporative fuel is turned off in such a specific region, a large amount of the evaporative fuel will suddenly enter the combustion chamber when the supply of the evaporative fuel is restarted, so the air-fuel ratio will be large. Change and the torque fluctuates. For example, if such a situation exactly coincides with the operation of the throttle, the driver will not notice so much, so there is no problem, but if the throttle fuel does not move much and the supply of evaporated fuel is restarted and the output fluctuates In such a steady state, the driver does not predict the output fluctuation, which causes a problem of poor driving feeling.

By the way, if a large amount of evaporated fuel is supplied to the intake system at one time, the air-fuel ratio may fluctuate. Therefore, it is known that the evaporated fuel is gradually supplied to prevent this. (See JP-A-58-91357).

However, since such a conventional technique does not change the control amount according to the degree of change in the operating state such as the throttle opening, it is difficult to be a means for solving the above problems peculiar to the steady state. It is originally desirable to purge and supply the adsorbed fuel vapor so that the canister does not saturate.Therefore, even if the supply is restricted from the viewpoint of drive feeling, such a restriction is limited to when it is necessary. It must be done.

(Object of the Invention) The present invention has been made in view of the problems that cannot be solved by the conventional techniques as described above, and an engine that does not cause a torque shock when the supply of the evaporated fuel to the intake system is restarted. It is an object of the present invention to provide a vaporized fuel processing device of the above.

(Structure of the Invention) The overall structure of the present invention is as shown in FIG. That is, the evaporated fuel processing apparatus for an engine according to the present invention is
An operating condition detecting means for detecting an operating condition of the engine; an evaporated fuel supply device for supplying evaporated fuel to an intake system of the engine; and an evaporated fuel control device for operating the evaporated fuel supply device according to the operating condition of the engine, Stop region detection means for detecting a specific region in which the supply of evaporated fuel is to be temporarily stopped and outputting a stop signal, and operation state change at restart for detecting the rate of change of the engine operating condition when the supply of evaporated fuel is restarted The rate detection means and the supply restriction means for restricting the supply of the evaporated fuel when the change in the operating state when the supply is restarted are small.

(Operation) The evaporated fuel generated in the fuel tank or the float chamber of the vaporizer is once collected in the evaporated fuel supply device. Then, when the engine operates and reaches a predetermined operating state, the collected evaporated fuel is supplied to the intake system. Evaporative fuel is not supplied in an operating region where the supply of evaporated fuel may impair the stability of combustion, such as during idling or when the engine temperature is low. Further, when it is detected that a specific region is reached, such as during learning in the feedback air-fuel ratio control system or when the O ₂ sensor is stuck, the supply of evaporated fuel is temporarily stopped. . Then, after passing through such a stop region, the supply is restarted, but when the change rate of the operating state such as the change of the throttle opening at this time is observed and the rate of change is large, the supply of the evaporated fuel is restarted as it is. However, when the rate of change is small, that is, in the steady state, the supply is controlled to be stopped or gradually supplied. That is,
When the change in the operating state is small, the restart of the evaporated fuel is limited to suppress the torque shock due to the change in the air-fuel ratio.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 2 shows an embodiment of the present invention applied to an engine that performs learning control of the air-fuel ratio.

As shown in the figure, a fuel injection valve 5 is provided in the intake passage 2 of the engine 1 at a position downstream of the throttle valve 3 and close to the intake valve 4. A hot wire type air flow sensor 7 is provided immediately downstream of the air cleaner 6 in the intake passage on the upstream side of the throttle valve 3, and an intake air temperature sensor 8 for detecting the intake air temperature is provided downstream of the throttle valve 3.
Is provided. Further, an opening sensor 9 for detecting the throttle valve opening is attached to the throttle valve. On the other hand, the exhaust passage 11 through which the exhaust gas discharged from the exhaust valve 10 passes
Is provided with an O ₂ sensor 12 that detects the oxygen concentration in the exhaust gas. Further, a distributor 15 that is connected to the igniter 13 and sends an ignition signal to the ignition plug 14 has a built-in rotation speed sensor. A water temperature sensor 17 that detects the temperature of the cooling water is attached to the cylinder block 16 of the engine 1. The engine 1 also includes a canister 19 that adsorbs evaporated fuel generated in the fuel tank 18. The canister 19 is configured to adsorb the evaporated fuel introduced from the fuel tank 18 through the introduction passage 20 and supply it to the intake passage 2 through the purge passage 22 when the negative pressure control valve 21 is opened. The negative pressure control valve 21 is opened and closed by the VC negative pressure immediately upstream of the throttle valve 3. When the throttle valve 3 is closed, the outlet to the purge passage 22 is closed and the throttle valve 3 is opened to open the VC hole. When negative pressure acts on the purge passage 22
Open to purge adsorbed fuel. Further, a solenoid type switching control valve 23 is provided in the purge passage 22. The switching control valve 23 switches the purge passage 22 opening to the intake passage 2 to the canister side or the atmosphere side according to a control signal from the control unit 24. When switched to the atmosphere side, the air filtered by the filter 26 from the atmosphere passage 25 enters the intake passage 2 instead of the evaporated fuel. The control unit 24 linearly controls the supply of evaporated fuel by changing the duty ratio of the control signal to the switching control valve 23. Further, the control unit 24 controls the fuel injection condition and the ignition timing based on the output signal of each sensor. Fuel injection control is
The learning value is created based on the feedback control signal, and the learning value is used as the next feedback control signal to perform so-called learning control to control the target air-fuel ratio.

Next, a flow chart for executing the control of this embodiment will be described with reference to FIG. In the figure, S _{1 to} S ₃₃ indicate each step.

First, after performing the initialization in S _1, the intake air quantity Qa at S _2, the engine rotational speed Ne or the like, reads the signals from various sensors, based on the intake air amount Qa and the engine speed Ne at S ₃ Basic The injection pulse width Tp is calculated from the equation Tp = (Qa / Ne) · K (K is a constant). Here, (Qa / Ne) corresponds to the intake charge amount, that is, the engine load, so Tp corresponds to the engine load.
Further, in S ₄ , the water temperature correction coefficient C _W , the intake air temperature correction coefficient C _AIR and the area correction coefficient C _R (O in the feedback zone) for correcting the basic injection pulse width Tp according to the engine operating state at that time are read, then in order to determine whether or not the engine 1 is in the zone to be feedback control of the air-fuel ratio, engine load Tp at S ₅ is whether or not a predetermined value Tp ₁ or less, S ₆
Determines whether the engine speed Ne is less than or equal to a predetermined value Ne ₁ , and when any of the determinations is NO, that is, Tp> Tp ₁
Alternatively, when Ne> Ne _1, it is determined that it is not in the feedback zone, the feedback correction coefficient C _FB for correcting the basic injection pulse width Tp is set to 1 in S ₇ , and immediately S ₂₅
Proceed to.

On the other hand, if YES in both the determination of the S ₅ and S _6, i.e. T
When p ≦ Tp ₁ and Ne ≦ Ne ₁ , it is judged that the air-fuel ratio is in the feedback zone, and in S ₈ , it is determined whether the air-fuel ratio of the air-fuel mixture is richer than the target air-fuel ratio based on the output of the exhaust sensor 25. and, one at YES is rich subtracting corrected by the feedback correction coefficient C _FB in S ₉ alpha, the target air-fuel ratio by adding correction by the feedback correction coefficient C _FB in S ₁₀ alpha at the time of a lean NO Feedback control is performed to achieve the fuel ratio.

Next, in order to determine whether the engine 1 is in the zone where the learning control of the air-fuel ratio should be performed (this zone corresponds to the zone where the lean burn operation is performed), in S ₁₁ , the engine load Tp is set.
Is in the range of Tp _G0 ≤ Tp ≤ Tp _G1 , whether the engine speed Ne is in the range of Ne _G0 ≤ Ne ≤ Ne _G1 is determined in S ₁₂ , and whether it is in the steady operation is determined in S _13. , These judgments are all YE
When S, that is, when at Tp _G0 ≦ Tp ≦ Tp _G1 is Ne _G0 ≦ Ne ≦ Ne _G1 a and steady operation proceeds to S ₁₄ to perform the learning control of the air-fuel ratio is judged to be in the learning zone. The above S
When any of the determinations of ₁₁ , S ₁₂ and S ₁₃ is NO, the learning control is not performed and the process immediately proceeds to S ₂₅ .

The first determines whether a learning control is completed in S _14, initially still proceeds to S ₁₅ from the non-learning control, while cutting the supply of evaporative fuel into the intake passage 2 Or not. When the evaporative fuel is being supplied to NO, the air-fuel ratio of the air-fuel mixture fluctuates due to the evaporative fuel and the learning control accuracy is degraded, so the supply of the evaporative fuel is cut off in S ₁₆ . This is an operation of adding 0% to the duty ratio E of the switching control valve 23 described above. And S
After setting the evaporative fuel cut flag at ₁₇ , immediately after S ₃₃
And the final injection pulse width Tp is calculated by the formula TP = Tp × (1 + C _W +
_{C AIR + C R + C FB} ) is calculated from.

On the other hand, if YES the supply of evaporative fuel in S ₁₅ is cut, prior to learning control determines whether the counter T ₁ in S ₁₈ is 0. This is because it is necessary to wait a little because the evaporated fuel does not disappear immediately after cutting, so it is checked whether a predetermined time has passed after cutting. Since it is not 0 yet at the beginning, learning control immediately after the supply cut of the evaporated fuel is avoided by repeatedly reducing T ₁ by 1 at S ₁₉ and increasing the time until T ₁ = 0. Therefore, erroneous learning due to residual evaporated fuel is prevented. After that, when T ₁ becomes 0, it is determined that there is no evaporated fuel in the intake passage 2, the feedback correction coefficient C _FB is averaged in S ₂₀ to calculate the learning value C _STDY , and then the learning time counter is counted in S _21. The process of reducing T ₂ by 1 is performed, and the counter T ₂ is incremented by S _22.
Waits until 0 becomes 0 and when T ₂ becomes 0, a learning completion flag is set in S ₂₃ .

Thereafter, if it the learning control is completed the determination of S ₁₄ becomes YES, the calculated feedback correction coefficient C _FB is multiplied by a predetermined lean coefficient to the learned value C _STDY in S _24, the process proceeds to S _25.

In S _25, it determines whether or not the vaporized fuel cut. And N
If it is O, it means that the vaporized fuel is being supplied, so bypass without doing anything. If So during the fuel cut (YES), first, enter the throttle opening S _26, then determines whether the rate of change of the throttle opening is large at S _27. In other words, it is observing whether acceleration or deceleration or steady operation is being performed. Then, when NO, that is, when the rate of change is small, this means that the driver is not aware of the change in the throttle, and therefore is not expecting a torque shock. At this time, go to S ₂₈ ,
5% is added to the duty ratio E (0%) at the time of fuel cut and gradually increased. Then, in S ₂₉ , it is determined whether E has become 100%, and this is repeated until it becomes 100%. E
If becomes 100%, go to S ₃₁ with YES to remove the evaporated fuel cut flag. Further, the term YES, that the throttle change rate S ₂₇ is large, this is a state in which the driver is aware of the output change in not stepping on the throttle, at this time go to S ₃₀ E immediately 100 % To open the purge passage for evaporated fuel.

In this embodiment, the supply of the evaporated fuel is gradually restarted when the throttle change is small, but it is also possible to perform control so as to completely cut the supply, instead of gradually increasing the supply amount. is there.

Further, the present invention is not limited to the above-mentioned embodiments and can be implemented in various other modes.

(Advantages of the Invention) Since the present invention is configured as described above, it is possible to prevent torque shock from occurring due to air-fuel ratio fluctuations accompanying vaporized fuel supply.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is an overall diagram of an embodiment of the present invention, and FIG. 3 is a flow chart for executing control of the embodiment. 1: engine, 2: intake passage, 3: throttle valve, 9: opening sensor, 19: canister, 21: negative pressure control valve, 23: switching control valve, 2
4: Control unit.

Claims (1)

[Claims] 1. An operating state detecting means for detecting an operating state of an engine, an evaporated fuel supply device for supplying evaporated fuel to an intake system of the engine, and an evaporation system for operating the evaporated fuel supply device according to the operating condition of the engine. Fuel control means, stop area detection means for detecting a specific area where the supply of vaporized fuel should be temporarily stopped and outputting a stop signal, and rate of change of the engine operating state when restarting supply of vaporized fuel is detected. An evaporative fuel treatment apparatus for an engine, comprising: a restarting operation state change rate detecting means; and a supply limiting means for limiting the supply of the evaporated fuel when the change in the operating state at the time of restarting the supply is small.