JPS63189665A - Vapor fuel processing device for engine - Google Patents

Abstract

PURPOSE:To prevent a torque shock, by temporarily stopping the supply of vaporizing fuel in a specific operation region and limiting the supply of the vaporizing fuel when an operative condition small changes in the time of restarting the supply of the vaporizing fuel. CONSTITUTION:A control unit 24, which calculates a basic fuel injection amount being based on detection values of a hot wire type air flow meter 7 and an engine speed sensor built in a distributor 15, performs a feedback control of air-fuel ratio on the basis of a detection value of an O2 sensor 12 in a predetermined operation region. In a steady operation condition with the basic fuel injection and engine speed in a predetermined range, an engine, which switches a selector control valve 23 connecting a purge passage 22 from the side of a canister 19 to the side of an atmospheric passage 25 and cutting the supply of vaporizing fuel, performs a study control of the air-fuel ratio. When the supply of the vaporizing fuel is restarted with the engine in a transfer from its steady operation to acceleration or deceleration operation, a supply amount of the vaporizing fuel is limited if a throttle opening provides a small change rate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an evaporated fuel processing device for an engine that supplies evaporated fuel to an intake system.

(Prior art) Automotive engines normally store evaporated fuel in a canister containing an adsorbent such as activated carbon to prevent the evaporated fuel generated in the fuel tank or the float chamber of the carburetor from leaking into the atmosphere. It is equipped with an evaporated fuel processing device that once adsorbs and collects the fuel, then removes it (purged) using negative intake pressure during engine operation and introduces it into the intake system.

Such evaporative fuel processing devices normally open the purge passage when the throttle valve is slightly depressed by a control valve that responds to the negative pressure in the C hole, allowing evaporative fuel to be drawn in and released, but in addition, it is also In some cases, the supply of evaporated fuel to the intake system may be stopped under certain operating conditions. For example, when such an evaporative fuel processing device is used in an engine equipped with a feedback air-fuel ratio control device that performs learning control, the amount of evaporative fuel supplied to the intake system fluctuates, causing the air-fuel ratio to change. Since the influence is not constant, it is necessary to temporarily stop the supply of evaporated fuel during learning to prevent erroneous learning. In addition, in a similar device equipped with a feedback control device, when the Ot sensor detects an abnormal condition such as sticking to the lean side or rich side due to a disconnection or short circuit, it is possible that a large amount of evaporated fuel has been supplied even if there is no abnormality. O: There are cases where the sensor sticks, so it is necessary to temporarily cut off the evaporated fuel. If the vaporized fuel is cut off in such a specific area, a large amount of vaporized fuel will suddenly enter the combustion chamber when the vaporized fuel supply is resumed, resulting in a large air-fuel ratio. and the torque fluctuates.

For example, if such a situation coincides with the throttle operation, the driver will hardly notice and there is no problem, but if the evaporative fuel supply is resumed during steady state when the throttle is not moving much, the output will fluctuate. , In such a steady state, the driver does not anticipate the output fluctuations, so there is a problem that the driving feeling is poor.

By the way, if a large amount of evaporated fuel is supplied to the intake system at once, problems such as fluctuations in the air-fuel ratio will occur, so in order to prevent this, it is known that the evaporated fuel is gradually supplied (especially (Refer to Publication No. 58-91357)
.

However, such conventional techniques do not change the control amount depending on the degree of change in operating conditions such as throttle opening, and therefore are difficult to serve as a means for solving the above-mentioned problems specific to steady state conditions. It is originally desirable to purge and supply adsorbed evaporated fuel quickly so that the canister does not become saturated, and even if supply is restricted from the perspective of drive feeling, such restrictions should only be applied when necessary. Because it must be done.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems that cannot be solved by the conventional techniques, and is an object of the present invention to provide an engine that does not cause torque shift when restarting the supply of evaporated fuel to the intake system. The purpose of the present invention is to provide an evaporative fuel processing device.

(Configuration of the Invention) The overall configuration of the present invention is as shown in FIG. That is, the evaporative fuel processing device for an engine according to the present invention has the following features:
an operating state detection means for detecting the operating state of the engine; an evaporative fuel supply device for supplying evaporative fuel to the intake system of the engine; and an evaporative fuel control means for operating the evaporative fuel supply device according to the operating state of the engine; stop area detection means that detects a specific area where the supply of vaporized fuel should be temporarily stopped and outputs a stop signal; and a change in operating state upon restart that detects the rate of change in the engine operating state when the supply of vaporized fuel is resumed. and a supply restriction means for restricting the supply of evaporated fuel when the change in the operating state at the time of resumption of supply is small.

(Function) The evaporated fuel that is completed in the fuel tank or the float chamber of the vaporizer is once collected in the evaporated fuel supply device.

Then, when the engine starts and reaches the specified operating condition,
The collected evaporated fuel is supplied to the intake system.

Evaporative fuel is not supplied in operating ranges where supplying evaporative fuel may impair combustion stability, such as when the engine is idling or when the engine temperature is low. Also, while learning is being performed in the feedback air-fuel ratio control system, 0. If a specific area is detected, such as when a sensor is stuck, the supply of evaporated fuel is temporarily stopped. Supply is resumed once such a stop region is passed, but changes in operating conditions such as changes in throttle opening are observed at this time, and if the rate of change is large, the supply of evaporated fuel is resumed. However, when the rate of change is small, that is, when it is steady, the supply is controlled to remain stopped or to be supplied gradually. In other words, when the change in operating conditions is small, resumption of vaporized fuel is restricted to suppress torque shock due to fluctuations in the air-fuel ratio.

(Example) Embodiments of the present invention will be described below based on the drawings.

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

As shown in the figure, a fuel injection valve 5 is provided in an intake passage 2 of an engine 1 at a position downstream of a throttle valve 3 and close to an intake valve 4. In the intake passage on the upstream side of the throttle valve 3, a hot wire type air flow sensor 7 is provided immediately downstream of the air cleaner 6, and an intake temperature sensor 8 that detects 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, an Ot sensor 12 for detecting the oxygen concentration in the exhaust gas is provided in the exhaust passage 11 through which the exhaust gas discharged from the exhaust valve IO passes. Further, a power distributor 15 connected to the igniter 13 and sending an ignition signal to the spark plug 14 has a built-in rotation speed sensor. A water temperature sensor 17 is attached to the cylinder block 16 of the engine 1 to detect the temperature of cooling water. The engine l also includes a canister 19 that adsorbs evaporated fuel generated within the fuel tank 18. The canister 19 is connected to the introduction passage 2.
The vaporized fuel introduced from the fuel tank 18 through the purge passage 22 is adsorbed and supplied into 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 when the throttle valve 3 is opened, the VC hole is closed. When negative pressure acts on the purge passage 22, the adsorbed fuel is purged. Furthermore, this purge passage 2
2 is provided with a solenoid type switching control valve 23. The switching control valve 23 switches the purge passage 22 that opens into the intake passage 2 to the canister side or the atmosphere side in response to a control signal from the control unit 24. When switching to the atmosphere side, air filtered by the filter 26 from the atmosphere passage 25 flows into the intake passage 2 instead of the evaporated fuel.
to go into. The control unit 24 includes a switching control valve 23
The supply of vaporized fuel is linearly controlled by changing the duty ratio of the control signal. Furthermore, the control unit 24 controls fuel injection conditions and ignition timing based on output signals from each sensor. Fuel injection control involves creating a learning value based on a feedback control signal and performing so-called learning control, which is used as the next feedback control signal, to control the air-fuel ratio to a target air-fuel ratio.

Next, a flowchart for executing control in this embodiment will be explained with reference to FIG. In the figure, S1 to S13 indicate each step.

First, after initializing with Sl, the intake air amount Q with S
a, reads the signals of various sensors such as engine speed Ne, and calculates the basic injection pulse width Tp based on the intake air amount Qa and engine speed Ne using the formula Tp= (Qa/Ne
)・K (K is a constant) Here, (Q
Since a/N e ) corresponds to the intake air filling amount, that is, the engine load, Tp corresponds to the engine load. Also,
In S4, the water temperature correction coefficient C11, intake temperature correction coefficient CAIR, and region correction coefficient CR (O in the feedback zone) are read, which correct the basic injection pulse width Tp according to the engine operating state at that time, and then the engine! In order to judge whether or not the air-fuel ratio is in the zone where feedback control is required, the engine load Tp is set to a predetermined value T (I) at S.
In S6, it is determined whether or not the engine speed Ne is equal to or less than a predetermined value N e +.If either of these determinations is No, that is, Tp>Tp or Ne>N
When it is e+, it is determined that it is not in the feedback zone, and in S7, the feedback correction coefficient Cra for correcting the basic injection pulse width Tp is set to 1, and immediately Sts
Proceed to.

On the other hand, when the determinations in S5 and S8 are both YES,
That is, when Tp≦Tp+ and Ne≦Ne+, it is determined that the feedback zone exists, and in S8 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, When YES is rich, the feedback correction coefficient CFII is corrected by subtracting α by Sg, while when NO is lean, Sg is used.

Then, the feedback correction coefficient CFB is added and corrected by α to perform feedback control so that the air-fuel ratio becomes the target air-fuel ratio.

Next, the zone where engine 1 should perform air-fuel ratio learning control (
In order to judge whether or not this zone corresponds to the zone where lean burn operation is required, the engine load 'r
Whether p is in the range of TI)co≦'rp≦Tpa+,
At lffi, engine speed Ne is Neco < Ne
<N e It is determined whether or not it is in the a+ range and whether it is in steady operation using srs, and both of these determinations are YE.
When S, that is, Tpao≦'rp<'rp6, Ne
When ao≦Ne≦Nec+ and the engine is in steady operation, it is determined that the engine is in the learning zone, and the process proceeds to S to perform air-fuel ratio learning control. Note that the above S1. .

If either Si1 or 5rff is NO, the process immediately proceeds to StS without performing learning control.

First, in S14, it is determined whether learning control has been completed, and since learning control has not yet been performed at the beginning, Si
5, it is determined whether or not the supply of vaporized fuel to the intake passage 2 is being cut. When the fuel vapor is supplied (NO), the air-fuel ratio of the air-fuel mixture changes depending on the fuel vapor and the learning control accuracy decreases, so the supply of the fuel vapor is cut at Sll+. This is an operation of setting the duty ratio E of the switching control valve 23 to 0%.

And St? After setting the evaporative fuel cut flag at
Immediately proceed to S33 and calculate the final injection pulse width Tp using the formula 'r
p='r'px (1+Cw+CAzR+Cn+CpJ
Calculate from

On the other hand, YE whose vaporized fuel supply is cut off at S16
In the case of S, it is determined in S II whether the counter T is 0 or not before performing permanent control. This is because evaporative fuel does not disappear immediately even if it is cut, so it is necessary to wait for a while, so it is checked whether a predetermined amount of time has passed since the cut. Initially, it has not yet reached 0, so by repeatedly decreasing T by 1 with Sl, and gaining time until T becomes -0, learning control can be avoided immediately after the vaporized fuel supply is cut. This is to prevent erroneous learning due to residual evaporated fuel. After that, when T1 becomes O,
It is determined that there is no evaporated fuel in the intake passage 2, and S. Average the feedback correction coefficient CFB.

After calculating the learning value C5TDY, the learning time counter T is decremented by 1 in Sll, and S9. Wait until the counter T, becomes O, and when T, = 0, 92
Set the learning completion flag at 3.

After that, the above learning control is completed and the judgment of S +4 becomes Y.
When ES is reached, the learning value CIITDY is multiplied by a predetermined lean coefficient in Sl4 to calculate a feedback correction coefficient CFB, and the process proceeds to SZS.

At Szs, it is determined whether or not evaporative fuel is being cut.

If the answer is No, it means that evaporated fuel is being supplied, so the route is bypassed without doing anything. Fuel cut in progress (YES)
), first enter the throttle opening in StS, then enter S6. to determine whether the rate of change in throttle opening is large.

In other words, we are looking at acceleration, deceleration, or steady operation. If No, that is, the rate of change is small, this means that the driver is not aware of the throttle change and therefore does not expect a torque shock.In this case, go to SRS and cut the fuel. Add 5% to the duty ratio E (0%) and gradually increase it.

And S. Determine whether E has reached 100% with
Repeat this until it reaches 100%. When E reaches 100%, say YES to 931 and lower the evaporative fuel cut flag. Also, St? If you say YES, that is, the throttle change rate is large, this means that the driver is stepping on the throttle and is aware of the change in output, and in this case, go to S3° and immediately set 100% to E. Open the vaporized fuel purge passage all at once.

In addition, in this embodiment, the supply of vaporized fuel is gradually resumed when the throttle change is small, but it is also possible to perform control to completely cut off the supply amount instead of gradually increasing the amount of vaporized fuel. It is.

Furthermore, the present invention is not limited to the above embodiments, but can be implemented in various other ways.

(Effects 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 the supply of evaporated fuel.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is an overall diagram of an embodiment of the invention, and FIG. 3 is a flowchart for executing control of the embodiment. l: Engine, 2: Intake passage, 3: Throttle valve, 9:
Opening sensor, 19: Canister, 21: Negative pressure control valve, 2
3: switching control valve, 24: control unit. Agent Patent Attorney Jun Shinfuji - Figure 1

Claims (1)

[Claims] (1) An operating state detection means for detecting the operating state of the engine, an evaporative fuel supply device that supplies evaporative fuel to the intake system of the engine, and evaporative fuel control that operates the evaporative fuel supply device according to the engine operating state. stop area detection means for detecting a specific area where the supply of evaporative fuel should be temporarily stopped and outputting a stop signal; and restart time detecting means for detecting a rate of change in the engine operating state when the supply of evaporative fuel is resumed. A evaporated fuel processing device for an engine, comprising an operating state change rate detection means and a supply restriction means for restricting the supply of evaporated fuel when the change in the operating state at the time of resumption of supply is small.