JP3196001B2 - Evaporative fuel treatment system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an evaporative fuel treatment system for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a measure for preventing the expansion of air pollution due to the release of evaporated fuel generated in a fuel supply system such as a fuel tank into the atmosphere, the evaporated fuel is temporarily adsorbed by an adsorbing means called a canister. Then, a purge gas (a mixture of purged fuel and outside air introduced into the canister at the time of desorption) obtained by desorbing (purge) the adsorbed fuel from the canister during operation of the engine is introduced into the intake air for processing (hereinafter, referred to as "gas"). ,
An evaporative fuel processing apparatus that performs purging is known, for example, as shown in FIG.

The purge control valve 3 opens and closes (ON / OFF) the communication between a canister 5 communicating with an upper space of a fuel tank 11 via a check valve 12 and an intake passage 2 of the engine 1. The purge fuel is interposed in the purge passage 4 and the purge fuel is sucked from the canister 5 into the intake system by the engine suction negative pressure when the purge control valve 3 is turned on. Then, the opening degree of the purge control valve 3 (for example, when a duty control valve is used as the purge control valve, the ON time ratio during a predetermined ON / OFF cycle, etc.) is changed via the control unit 10 to thereby purge gas. Adjust the amount. It should be noted that a venturi 6 provided at the connection between the purge passage 4 and the intake passage 2 on the intake upstream side of the throttle valve 7 is provided.
Is provided to induce a larger negative pressure in the purge passage 4 by the action of the negative pressure of the venturi 6 and to efficiently suck the purge gas into the intake passage 2.

However, since the venturi 6 is provided so as to protrude into the intake passage 2, the ventilation resistance is increased, so that the intake air flow rate is reduced at a high load or the like where a large intake air flow rate is required. However, there is a problem that the engine output is reduced. Therefore, as shown in FIG. 9, a bypass passage 9 is provided in the intake passage 2, and the venturi 6 is provided in the bypass passage 9. By closing the control valve 8 provided in the inside, the bypass passage 9
In the same way as in the above-described apparatus, the negative pressure is guided into the purge passage 4 by passing the intake air to the side, while the control valve 8 is opened when the intake air flow rate is high and the airflow resistance is a problem. In this case, a desired intake air flow rate can be obtained by enlarging the passage area (see FIG. 10 showing the relationship between the throttle valve opening and the control valve opening). ).

[0005]

However, in the configuration shown in FIG. 9, although the output characteristics of the engine can be improved, when the control valve 8 is opened, it flows through the bypass passage 9 side. Since the intake air flow rate is reduced, the negative pressure generated in the venturi 6 is also reduced, and the purge gas amount is reduced (see FIG. 11 showing the relationship between the control valve opening and the purge gas amount). In addition, there is a problem that the purging process cannot be performed and an air-fuel ratio step occurs to deteriorate the engine operability, the exhaust performance, and the like.

Another problem is as follows. That is, as shown in FIGS. 8 and 9, when the purge passage 4 is connected to the intake passage 2 on the upstream side of the throttle valve 7, the introduced purge gas collides with the throttle valve 7 or the like. Even when the control valve 3 is used, the generation of the air-fuel ratio of the intake air-fuel mixture due to the intermittent flow of the purge gas generated by the ON / OFF control of the purge control valve 3 is suppressed. In comparison with the type that introduces the above, the fluctuation of the air-fuel ratio due to the intermittent flow of the purge gas is small. Originally less. However, when the opening degree of the throttle valve 7 exceeds a predetermined value, the probability that the purge gas collides with the throttle valve 7 decreases, the effect of suppressing the generation of the air-fuel ratio of the intake air-fuel mixture due to the intermittent flow of the purge gas decreases, and the engine stabilizes. It is conceivable that problems such as a decrease in performance, a decrease in exhaust purification performance, and a hunting of the air-fuel ratio feedback control may occur, but such consideration has not been taken at all.

The present invention has been made in view of such a conventional problem, and is directed to an evaporative fuel treatment apparatus for an internal combustion engine in which purge gas is introduced into an intake passage upstream of a throttle valve. In the case where a bypass passage is provided in the passage, a purge gas is introduced into the bypass passage, and a control valve for controlling a flow rate of intake air flowing into the bypass passage is controlled according to an operation state.
It is a first object of the present invention to provide an evaporative fuel processing apparatus for an internal combustion engine capable of securing a desired engine output in the entire operation region and performing a desired purge process without generating an air-fuel ratio step in the entire operation region. Aim.

In the fuel vapor treatment apparatus for an internal combustion engine in which purge gas is introduced into an intake passage on the upstream side of the throttle valve, even if the opening degree of the throttle valve exceeds a predetermined value,
It is a second object of the present invention to provide an evaporative fuel processing apparatus for an internal combustion engine capable of suppressing fluctuations in an air-fuel ratio due to intermittent flow of purge gas and maintaining high engine stability and exhaust gas purification performance.

[0009]

Therefore, an evaporating apparatus for an internal combustion engine according to the first aspect of the present invention temporarily absorbs the evaporative fuel generated in a fuel tank A or the like as shown in FIG. The evaporative fuel stored in the adsorbing means is interposed in a purge passage connecting the adsorbing means B and the suction means B and the intake system upstream of the throttle valve C under predetermined engine operating conditions. A purge control valve D whose opening degree is controlled to be detached and introduced into the intake system upstream of the throttle valve;
Together constitute include, to form a bypass passage E merging into the intake system passage again branches throttle valve C upstream from the intake system passage of the throttle valve C upstream, downstream of the purge passage to the bypass passage E The suction air flow rate through which the evaporated fuel desorbed by connecting its ends flows through the bypass passage E
And a control valve F for controlling the flow rate of intake air flowing into the bypass passage E is provided, and the opening of the control valve F is controlled in accordance with the engine operating state. The purge control valve opening correction means G for correcting the opening of the purge control valve D in accordance with the opening of the control valve F during the process of introducing the desorbed evaporated fuel.

According to the second aspect of the present invention, the purge control valve opening correction means G is configured to correct the opening of the purge control valve D to increase as the opening of the control valve F increases.
Was.

According to the third aspect of the present invention, as shown in FIG.
As described above, the adsorbing means B for temporarily adsorbing and storing the evaporated fuel generated in the fuel tank A and the like, and the purge passage connecting the adsorbing means B and the intake system upstream of the throttle valve C, A purge control valve D whose opening degree is controlled so as to desorb the evaporated fuel stored in the adsorbing means B and introduce it into the intake system on the upstream side of the throttle valve C under the following engine operating conditions;
And a bypass passage E branching from the intake passage on the upstream side of the throttle valve C and merging again with the intake passage on the upstream side of the throttle valve C is formed. A control valve F for controlling the flow rate of the intake air flowing into the bypass passage E while sucking and introducing the evaporated fuel desorbed by connecting the ends by the negative pressure generated according to the flow amount of the intake air flowing through the bypass passage E And the purge valve D is periodically opened and closed by controlling the opening and closing of the control valve F in accordance with the operating state of the engine. Control the amount of fuel vapor introduced,
A purge control valve opening correction means G for correcting the opening of the purge control valve D according to the opening of the control valve F during the introduction of the desorbed evaporative fuel; The opening and closing frequency of the purge control valve D is
And a purge control valve opening / closing frequency control means H variably controlled according to the degree of opening.

[0012]

According to the first aspect of the present invention, the opening of the purge control valve is corrected via the purge control valve opening correcting means in accordance with the opening of the control valve. I do. Accordingly, in a situation in which the control valve is opened and the flow rate of intake air flowing through the bypass passage decreases, the negative pressure in the bypass passage decreases, and the introduction amount of the desorbed evaporated fuel decreases, for example, According to the second aspect of the present invention, the opening of the purge control valve can be increased and corrected in accordance with the opening of the control valve, so that the decrease in the introduction amount of the desorbed evaporated fuel is compensated for. As a result, a satisfactory purging process can be performed, and the occurrence of an air-fuel ratio step is suppressed, so that the engine operability, exhaust performance, and the like can be maintained satisfactorily.

[0013]

According to the third aspect of the present invention, the opening of the purge control valve is corrected in accordance with the opening of the control valve through the purge control valve opening correcting means, and the purge control valve opening / closing frequency is adjusted. An opening / closing frequency of the purge control valve is changed according to an opening degree of the throttle valve via a control means. As a result, the control valve is opened, the flow rate of intake air flowing through the bypass passage decreases, the negative pressure in the bypass passage decreases, and a problem associated with a decrease in the amount of the desorbed evaporated fuel introduced. Evaporated fuel (purge gas) introduced into the intake passage when the opening degree exceeds a predetermined value
However, the probability of colliding with the throttle valve is reduced, and it is possible to suppress the occurrence of a problem caused by the fluctuation of the air-fuel ratio of the intake air-fuel mixture being increased due to the intermittently introduced evaporated fuel.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the same reference numerals as those shown in FIG. 9 will be described with the same reference numerals. In FIG. 3, an intake passage 2 of an engine 1 has an air flow meter 24 for detecting an intake air flow rate Q of intake air taken through an air cleaner (not shown) and a throttle valve for controlling the intake air flow rate Q in conjunction with an accelerator pedal. An electromagnetic fuel injection valve 14 is provided for each cylinder in a downstream manifold portion.

The fuel injection valve 14 is driven to open by an injection pulse signal set by a method described later in the control unit 10 containing a microcomputer, and injects and supplies a predetermined amount of fuel. A fuel pump 18 is mounted in the fuel tank 11, and the fuel pumped from the fuel pump 18 is adjusted to a predetermined pressure through a fuel supply passage 20 provided with a pressure regulator 19, and the fuel injection valve 14 is provided. Supplied to Excess fuel from the pressure regulator 19 is returned to the fuel tank 11 via a return fuel passage 21.

The exhaust passage 15 is provided with an air-fuel ratio sensor 16 for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas at the manifold gathering portion. A three-way catalyst (not shown) is provided as an exhaust gas purifying catalyst for purifying by oxidizing HC and reducing NO _X. The distributor (not shown in FIG. 3) has a built-in crank angle sensor 17 which counts a crank unit angle signal output from the crank angle sensor 17 in synchronization with the engine rotation for a predetermined time, or The engine rotation speed N is detected by measuring the period of the reference angle signal.

The control unit 50 calculates a fuel amount corresponding to the target air-fuel ratio based on the values detected by the various sensors, and outputs an injection pulse signal having a pulse width corresponding to the fuel amount to the fuel injection valve 14. Output. That is, from the intake air flow rate Q detected by the air flow meter 24 and the engine speed N obtained by counting the pulse signal of the crank angle sensor 17 for a certain period of time,
Basic fuel injection pulse width (corresponding to fuel injection amount) Tp
(Tp = k × Q / Ne, where k is a constant)
Correction amount Ts for correcting the various correction coefficients COEF corresponding to the engine operating state, the air-fuel ratio feedback correction coefficient alpha, the learning correction coefficient K _L, the change in the effective opening time of the electromagnetic fuel injection valve by the battery voltage calculated preparative respectively, so that the actual air-fuel ratio becomes the target air-fuel ratio, setting a final fuel injection pulse width Ti = Tp · COEF · α · K L + Ts the basic fuel injection pulse width Tp correction operation to It is supposed to.

Note that the various correction coefficients COEF are, for example,
If COEF = 1 + K_MR+ K_TW+ K _AS+ K_AI+ ...
Where K is_MRIs the air-fuel ratio supplement
Positive coefficient, K_TWIs the water temperature increase correction coefficient, K_ASIs starting and starting
Post-increase correction coefficient, K_AIIs the post-idle increase correction coefficient.
You. The air-fuel ratio feedback correction coefficient α is
Proportional / product based on the detection result of the exhaust air-fuel ratio by the ratio sensor 16
It is increased or decreased by minute control, etc.
Controls the air-fuel ratio of the intake air-fuel mixture to the target air-fuel ratio (stoichiometric air-fuel ratio)
It is possible. Therefore, during the purging process
Is also determined by the air-fuel ratio feedback correction coefficient α.
The amount of radiation has been corrected and the target air-fuel ratio can be controlled well.
I am able to do it.

Further, the deviation from the reference value of the air-fuel ratio feedback correction coefficient in the air-fuel ratio feedback control alpha, by determining the predetermined learned for each area of each engine operating state learning correction coefficient K _L, the in the calculation of the fuel injection amount is calculated (when the alpha = 1.0) basic fuel injection amount Tp is corrected by the learning correction coefficient K _L, the air-fuel ratio feedback correction coefficient alpha by without correction The target air-fuel ratio is obtained from the fuel injection amount Ti, and the air-fuel ratio feedback correction coefficient α is used when the operating conditions change.
The air-fuel ratio control accuracy is improved with good responsiveness even before the data can be acquired.

The fuel vapor stored in the upper space of the fuel tank 11 is guided to the canister 5 through a fuel vapor passage 13 provided with a check valve 12. The evaporated fuel temporarily adsorbed in the canister 5 is introduced into a bypass passage 9 upstream of the throttle valve 7 via a purge passage 4 provided with a purge control valve 3 under predetermined operating conditions. The purge passage 4 and the bypass passage 9 are located upstream of the throttle valve 7 on the intake side.
A venturi 6 is provided at the connection portion with. The intake passage 2 is provided with a control valve 8 for distributing intake air to the intake passage 2 and the bypass passage 9.
The opening of the control valve 8 is controlled in accordance with the operating state (engine load, rotation speed, etc.). The control is performed, for example, by using an accelerator pedal [or a throttle valve 7].
May be achieved by interlocking with the control unit via a link mechanism or the like, or may be driven and controlled by a step motor or the like. As described above, the opening characteristic of the control valve 8 with respect to the opening of the throttle valve 7 is shown in FIG.
The relationship is as shown in FIG.

In this embodiment, a first temperature sensor 22 for detecting the temperature around the canister 5 in order to control the purge gas amount, and hence the purge rate (purge gas amount / intake air flow rate Q) with high accuracy, A second temperature sensor 23 for detecting the temperature inside the canister 5;
Estimates the amount of fuel vapor adsorbed on the canister 5 based on conditions including the temperature state of the canister 5 detected by the first temperature sensor 22 and the second temperature sensor 23,
The purge rate of the evaporated fuel is controlled by controlling the opening of the purge control valve 30 based on the evaporated fuel amount. It should be noted that the opening of the purge control valve 3 may be controlled in accordance with the opening set in advance according to the operating state.

Here, the estimation of the amount of fuel vapor adsorbed on the canister 5 by the control unit 10 and the control of the opening of the purge control valve 3 based on the estimation result will be described with reference to the flowcharts of FIGS. 4 showing a routine for estimating the adsorption evaporative fuel amount, (referred to as S in FIG. Hereinafter, the same) In step 1 reads the temperature T _a of the canister 5 peripheral portion detected by the first temperature sensor 22.

In step 2, the temperature _Tc inside the canister 5 detected by the second temperature sensor 23 is read. In step 3, the canister 5 canister 5 internal temperature relative to the temperature T _a of the peripheral portion T _c deviation ΔT (= T _c -T
_a ) In step 4, it calculates a time integration value S _c of the [Delta] T.

Here, S _c = ∫ΔT ≒ ΣS ₁ -ΣS ₂ where ΣS ₁ is the integrated value of ΔT which becomes a positive value due to the exothermic reaction caused by the adsorption of the evaporated fuel, and ΣS ₂ is the accumulated value of the evaporated fuel. This is the integrated value of ΔT that becomes a negative value in the endothermic reaction due to desorption.
In step 5, the amount of evaporated fuel adsorbed in the canister 5 in this operation based on a time integration value S _c of [Delta] T G _cN
Is estimated by a search from a map previously obtained experimentally and stored in the ROM. In the case of に は S ₁ <ΣS _2, the amount of desorption is larger than the amount of adsorption, and in that case, G _cN is a negative value.

In step 6, by adding the amount of evaporated fuel C _cN currently adsorbed to the amount of evaporated fuel G _cO adsorbed to the canister 5 in the previous operation, the amount of evaporated fuel currently adsorbed to the canister 5 is increased. to estimate the amount G _c. In step 6, ON / OFF of the key switch is determined.
Then, when the key switch is turned off, the estimated amount of adsorbed fuel vapor G _c is stored in the backup memory as G _cO .

Next, the purge amount of evaporative fuel based on adsorption evaporative fuel amount G _c of the estimated canister 5 (i.e.,
The opening control of the purge control valve 3 for controlling the opening of the purge control valve 3) will be described with reference to the flowchart shown in FIG. In step 11, the intake negative pressure P _E in the venturi 6 is estimated based on the engine speed N and the basic fuel injection amount Tp.

[0028] In step 12, on the basis of the intake negative pressure P _E and the suction evaporative fuel amount G _c, which can be purged, i.e. the maximum of the fuel vapor purge amount P _AMAX in the case of the fully open purge control valve 3 It is determined by a search from a preset map. In step 13, the engine speed N and the basic fuel injection amount Tp (or the intake negative pressure P _E estimated in step 11)
, The required value P _ASET of the purge amount of the evaporated fuel is obtained by searching a preset map.

In step 14, the target value P _AMAX is determined based on the maximum evaporated fuel purge amount P _AMAX and the target value P _ASET.
The final valve opening control duty P _ADUTY of the purge control valve 3 for obtaining _ASET is obtained by searching a preset map. Subsequently, in step 15, the valve opening duty P _ADUTY obtained in step 14 is obtained from the relationship between the opening of the control valve 8 (a sensor or the like or the opening of the throttle valve 7 in FIG. 10). The correction amount A is obtained by referring to the map of FIG. 6 based on the opening degree of the control valve 8 and added to the P _ADUTY to make a final correction of the purge control valve 3. _{Obtain the} valve opening control duty P _ADUTY . Therefore, even in the situation where the control valve 8 is opened and the flow rate of the intake air flowing through the bypass passage 9 decreases, the negative pressure generated in the venturi 6 decreases and the purge gas amount decreases, the purge control valve 3 _Valve opening duty P _ADUTY
Is increased in accordance with the opening degree of the control valve 8, so that the decrease in the purge gas amount can be compensated for, so that a good purge process can be performed and the occurrence of the air-fuel ratio step is suppressed, and Drivability, exhaust performance, etc. can be maintained satisfactorily. Step 15 corresponds to the purge control valve opening correction means of the present invention.

In step 16, the frequency f at which the control signal of the valve opening duty P _ADUTY obtained in step 15 is issued
From a preset map such as that shown in the flow based on the opening of the throttle valve 7. The opening / closing frequency f of the purge control valve 3 may be set to a high frequency when the opening of the throttle valve 7 is equal to or more than a predetermined value, as shown in FIG. Note that, even when the frequency f is changed, the purge control valve 3 is opened per valve so that the total valve opening time (purge gas amount per predetermined time) of the purge control valve 8 within the predetermined time is maintained. The time is changed (that is, if the frequency is doubled, the one opening time of the purge control valve 8 is changed to １ ／).

As described above, even when the opening degree of the throttle valve 7 becomes a predetermined value or more and the probability that the purge gas collides with the throttle valve 7 is reduced, the generation cycle of the air-fuel ratio of the intake air-fuel mixture due to the intermittent flow of the purge gas. Was shortened,
As a whole, the degree of air-fuel ratio shading occurrence is suppressed (shortening of shading generation cycle and shading difference is reduced), thereby lowering engine stability, lowering exhaust gas purification performance, and reducing air-fuel ratio feedback control. The fluctuation of the air-fuel ratio that causes a problem such as hunting is suppressed. Step 16 corresponds to the purge control valve opening / closing frequency control means of the present invention.

In step 17, the valve opening control duty P _ADUTY corrected as described above in accordance with the frequency f obtained in step 16 is output to the purge control valve 3. In step 18, when the fuel vapor is not purged, the purge amount target value P is determined from the fuel injection pulse width Ti set according to the engine operation state (engine speed N _, intake air flow rate Q _, water temperature _TW, etc.). By subtracting the value multiplied by the conversion constant m to convert _ASET into the injection pulse width, the final fuel injection pulse width Ti ′ of the fuel injection valve 14 is obtained.
Ask for.

In step 19, the fuel injection pulse width T
and outputs an injection pulse signal having i 'to the fuel injection valve 14.
Then, this flow ends. As described above, according to the present embodiment,
Then, the control valve 8 is opened and the suction flowing through the bypass passage 9 side is performed.
Incoming air flow is reduced and negative pressure generated by venturi 6 is small.
In situations where the amount of purge gas decreases
However, the valve opening duty P of the purge control valve 3 _ADUTYThe system
The increase correction is made according to the opening of the control valve 8, so that
Can compensate for the decrease in
Processing, and the occurrence of air-fuel ratio steps is suppressed.
Good engine operability, exhaust performance, etc.
You.

The switching frequency f of the purge control valve 3 is
Since the opening degree of the throttle valve 7 is changed according to the opening degree of the throttle valve 7, the probability that the purge gas collides with the throttle valve 7 is reduced, and the ON / OFF cycle of the purge control valve 3 is reduced. Even in a situation in which the air-fuel ratio fluctuates due to the intermittent flow of the purge gas generated in synchronization with, the generation cycle of the concentration of the air-fuel ratio of the intake air-fuel mixture due to the intermittent flow of the purge gas can be shortened. Since the degree of air-fuel ratio shading can be suppressed (shortening of shading generation cycle and shading difference per valve opening), engine stability is reduced, exhaust purification performance is reduced, and hunting of air-fuel ratio feedback control is performed. It is possible to suppress the fluctuation of the air-fuel ratio that causes the problem of the above.

In this embodiment, the ventilator 6 has been described. However, the ventilator 6 need not be provided. That is, the present invention can be applied to a configuration in which the intake valve is passed through the bypass passage at a small intake air flow rate and the control valve 8 is opened at a large intake air flow rate to prevent a decrease in the intake air flow rate. Steps 15 and 16 in the flowchart of FIG. 5 are independently established as inventions. For example, only step 15 is provided, and only the opening of the purge control valve 3 is corrected according to the opening of the control valve 8. In the case of carrying out (claims 1 and 2), the purge control valve 3
It is not necessary to use a duty control valve.

[0036]

As described above, according to the first aspect of the present invention, the degree of opening of the purge control valve is changed according to the degree of opening of the control valve via the purge control valve opening correction means. The control valve is opened, the flow rate of intake air flowing through the bypass passage decreases, the negative pressure in the bypass passage decreases, and the introduction amount of the desorbed evaporated fuel decreases. Under such circumstances, for example, the opening degree of the purge control valve is
Since the increase can be corrected in accordance with the opening degree of the control valve, it is possible to compensate for the decrease in the introduction amount of the desorbed evaporative fuel, thereby performing a good purge process and generating an air-fuel ratio step. And the engine operability, exhaust performance and the like can be maintained satisfactorily.

[0037]

According to the third aspect of the present invention, the purge control valve opening correction means corrects the purge control valve opening in accordance with the control valve opening via the purge control valve opening / closing frequency. Through the control means, since the opening and closing frequency of the purge control valve is changed according to the opening degree of the throttle valve, the control valve is opened, the flow rate of intake air flowing through the bypass passage decreases, When the negative pressure in the bypass passage decreases and the amount of the desorbed evaporative fuel introduced decreases, and the opening degree of the throttle valve becomes a predetermined value or more, the evaporative fuel introduced into the intake passage becomes a throttle valve. The probability that the air-fuel ratio of the intake air-fuel mixture will fluctuate due to the evaporative fuel introduced intermittently can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the invention described in claim 1;

FIG. 2 is a diagram corresponding to claims of the invention described in claim 3;

FIG. 3 is an overall configuration diagram according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a routine for estimating the amount of fuel adsorbed by the canister according to the embodiment;

FIG. 5 shows the valve opening duty of the purge control valve of the embodiment.
Flowchart showing a switching frequency control routine

FIG. 6 is a diagram showing the relationship between the control valve opening and the opening (valve opening duty) correction amount A of the purge control valve in the embodiment.

FIG. 7 is a diagram showing a relationship between a throttle valve opening and an opening / closing frequency f of a purge control valve in the embodiment.

FIG. 8 is an overall configuration diagram showing an example of a conventional evaporative fuel processing apparatus.

FIG. 9 is an overall configuration diagram showing another example of a conventional evaporated fuel processing apparatus.

FIG. 10 is a diagram showing a relationship between a throttle valve opening and a control valve opening.

FIG. 11 is a diagram illustrating a relationship between a control valve opening and a purge gas amount.

[Explanation of symbols]

 Reference Signs List 1 engine 2 intake passage 3 purge control valve 4 purge passage 5 canister 7 throttle valve 8 control valve 9 bypass passage 14 fuel injection valve 10 control unit 11 fuel tank 17 crank angle sensor 24 air flow meter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-280636 (JP, A) JP-A-6-229330 (JP, A) JP-A-6-280688 (JP, A) 101059 (JP, U) Japanese Utility Model 4-1658 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 25/08 301

Claims (3)

(57) [Claims] 1. An adsorbing means for temporarily adsorbing and storing evaporative fuel generated in a fuel tank and the like, and a purge passage connecting the adsorbing means and an intake system upstream of a throttle valve are provided. A purge control valve whose opening is controlled to desorb evaporative fuel stored in the adsorbing means and to introduce the fuel into the intake system upstream of the throttle valve under engine operating conditions; A bypass passage branching off from the intake system passage on the side of the throttle valve and merging again with the intake system passage on the upstream side of the throttle valve, and connecting the downstream end of the purge passage to the bypass passage to discharge the desorbed fuel vapor. A suction valve is introduced by a negative pressure generated in accordance with a flow rate of intake air flowing through the bypass passage, and a control valve for controlling a flow rate of intake air flowing into the bypass passage is provided. The opening control of the purge control valve is performed during the introduction process of the desorbed evaporative fuel, and the opening of the purge control valve is corrected according to the opening of the control valve. An evaporative fuel treatment apparatus for an internal combustion engine, comprising: 2. The evaporator of an internal combustion engine according to claim 1, wherein said purge control valve opening correction means corrects an increase in the opening of said purge control valve as the opening of said control valve increases. Fuel processor. 3. An adsorbing means for temporarily adsorbing and storing evaporative fuel generated in a fuel tank or the like, and a purging passage connecting the adsorbing means and an intake system upstream of a throttle valve are provided. A purge control valve whose opening is controlled to desorb evaporative fuel stored in the adsorbing means and to introduce the fuel into the intake system upstream of the throttle valve under engine operating conditions; A bypass passage branching off from the intake system passage on the side of the throttle valve and merging again with the intake system passage on the upstream side of the throttle valve, and connecting the downstream end of the purge passage to the bypass passage to discharge the desorbed fuel vapor. A suction valve is introduced by a negative pressure generated in accordance with a flow rate of intake air flowing through the bypass passage, and a control valve for controlling a flow rate of intake air flowing into the bypass passage is provided. And the purge control valve is periodically opened and closed to control the opening / closing time ratio, thereby controlling the amount of the desorbed fuel vapor to be introduced. A purge control valve opening correction means for correcting the opening of the purge control valve in accordance with the opening of the control valve during the introduction of the desorbed evaporative fuel; And a purge control valve opening / closing frequency control means for variably controlling the opening / closing frequency of the purge control valve in accordance with the opening of the throttle valve.