JPH0533731A - Vapor fuel controller of internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] When the purge flow meter deteriorates with time or when the output characteristics change due to some accident, there is no need to immediately repair or replace the purge flow meter, and the purge gas from the canister is not necessary. PROBLEM TO BE SOLVED: To provide an evaporated fuel control device for an internal combustion engine, which can appropriately control the supply of fuel to the engine. [Arrangement] A switching valve 21 is provided in a purge pipe 17, and under a predetermined condition, the atmosphere is supplied from an atmosphere intake port 211 provided in the switching valve 21 to purge flow meters 19 and 20, and when the atmosphere is supplied, The output values of the purge flow meters 19, 20 are corrected based on the outputs of the purge flow meters 19, 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel control system for an internal combustion engine, which controls the flow rate of fuel evaporative gas supplied from a canister to an engine intake system via a purge passage.

[0002]

2. Description of the Related Art Conventionally, a fuel evaporative emission control device has been widely used to prevent the fuel evaporative emission generated from fuel in a fuel tank from being released into the atmosphere. In this device, the fuel evaporative emission gas is temporarily stored in the canister, and the stored evaporative fuel is supplied to the intake system of the internal combustion engine through the purge passage provided between the canister and the internal combustion engine intake system. The supply (purge) of the evaporated fuel to the intake system is performed by controlling the flow rate of the evaporated fuel by the purge control valve provided in the purge passage, but when the purge evaporated fuel is large, the mixture is supplied to the engine. The air-fuel ratio of air may fluctuate, and as a result, the exhaust gas characteristics of the engine may deteriorate and the output torque may fluctuate. Therefore, it is necessary to accurately detect the flow rate of the purged vaporized fuel and control the flow rate to a value that does not cause a change in the air-fuel ratio according to the detected flow rate of the purged vaporized fuel.

In order to meet this demand, the amount of purged fuel vapor is reduced for a predetermined period of time (Japanese Patent Laid-Open No. 63-63).
Japanese Patent Laid-Open No. 62-131962) has been attempted to reduce the amount of fuel supplied to the engine based on the predicted value of the fluctuation of the purged fuel vapor amount.

However, none of the above-mentioned conventional methods detect the actual amount of purged fuel vapor, so that the air-fuel ratio may not be accurately controlled. Therefore, in order to accurately detect the actual flow rate of the fuel evaporative emission gas, a plurality of purge flow meters are provided in the purge pipe, and the concentration of the fuel evaporative emission gas and the air-fuel mixture containing the fuel evaporative emission gas are based on the output of the purge flow rate meters. The applicant of the present invention has proposed a device for measuring a component of a purge gas, which is adapted to detect at least one of the volumetric flow rates of the gas (hereinafter abbreviated as "purge gas") (Japanese Patent Application No. Hei 3).
-80726).

[0005]

In the evaporative fuel control system for an internal combustion engine provided with such a purge flow meter, the inspection and adjustment of the output characteristics of the purge flow meter are usually performed only when the purge flow meter is manufactured. Therefore, no correction means was provided for fluctuations in the output value due to deterioration of the purge flow meter over time. Therefore, if the output characteristics of the purge flow meter change due to deterioration over time and an error occurs in the detected concentration of fuel evaporative gas (hereinafter abbreviated as "vapor"), the actual vapor concentration may be too high (overrich In the case of), hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas increase and the exhaust gas characteristics deteriorate,
On the contrary, if the actual vapor concentration is too low (in the case of over lean), there is a disadvantage that the purging efficiency of the canister is lowered.

The present invention has been made in order to eliminate such inconveniences of the conventional evaporated fuel control device for an internal combustion engine. The purge flow meter is deteriorated with time, or the output characteristic is changed due to some accident or the like. At this time, it is an object of the present invention to provide an evaporated fuel control device for an internal combustion engine, which can appropriately control the supply of purge gas from the canister to the engine without having to immediately repair or replace the purge flow meter.

[0007]

An internal combustion engine evaporative fuel control system according to the present invention is provided between a canister for adsorbing fuel evaporative gas generated from a fuel tank and an engine intake system to purge the fuel evaporative gas. An evaporative fuel control device for an internal combustion engine, comprising: a purge passage for controlling the flow rate of the fuel evaporative gas supplied to the engine intake system via the purge passage; A purge flow meter whose output characteristics change according to the concentration of the fuel evaporative gas, and an atmosphere supply means for supplying the atmosphere to the purge flow meter under predetermined conditions,
Output correction means for correcting the output of the purge flow meter based on the output of the purge flow meter when the air is supplied.

[0008]

In the evaporated fuel control apparatus for an internal combustion engine of the present invention, when the output characteristic of the purge flow meter deteriorates, the atmosphere supply means supplies the atmosphere to the purge flow meter, and the purge flow meter output at this time is used as a basis. Since the output of the purge flow meter is corrected by the output correcting means, the supply of the purge gas from the canister to the engine can be properly controlled without immediately repairing or replacing the purge flow meter.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of an evaporative fuel control system for an internal combustion engine according to an embodiment of the present invention. Reference numeral 1 indicates, for example, a 4-cylinder internal combustion engine, and an intake pipe 2 of the engine 1
A throttle body 3 is provided on the way, and a throttle valve 301 is arranged inside thereof. Throttle valve 3
A throttle valve opening (θTH) sensor 4 is connected to 01, and an electronic control unit (hereinafter referred to as “EC
U ") 5. This ECU 5 has an output correction means.

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 301 and slightly upstream of an intake valve (not shown) of the intake pipe 2, and each fuel injection valve 6 is provided with a fuel pump 7. Is connected to the fuel tank 8 via and is electrically connected to the ECU 5, and the valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

An intake pipe absolute pressure (PBA) sensor 10 is provided immediately downstream of the throttle valve 301 via a pipe 9. The absolute pressure signal converted by the absolute pressure sensor 10 into an electric signal is sent to the ECU 5. Supplied.

The engine speed (NE) sensor 11 is mounted around a cam shaft or crank shaft (not shown) of the engine 1, and a signal pulse (hereinafter referred to as "hereinafter referred to as" a signal pulse "at a predetermined crank angle position every 180 degrees rotation of the crank shaft of the engine 1). (Referred to as “TDC signal pulse”), and this TDC signal pulse is supplied to the ECU 5.

An engine water temperature (TW) sensor 22 such as a thermistor is attached to the peripheral wall of the cylinder filled with the cooling water of the cylinder block of the engine 1, and the engine cooling water temperature TW detected by the TW sensor 22 is electric. It is converted into a signal and supplied to the ECU 5.

O ₂ sensor 1 as an exhaust gas concentration detector
2 is attached to the exhaust pipe 13 of the engine 1, detects the oxygen concentration in the exhaust gas, outputs a signal according to the concentration, and supplies it to the ECU 5.

A two-way valve 14 and an adsorbent 151, which constitute a fuel evaporative emission control device, are provided between the closed upper portion of the fuel tank 8 and the intake pipe 2 downstream of the throttle body 3.
A canister 15 having a built-in valve, and a purge control valve 1 which is a linear control valve (EACV) having a solenoid for driving the valve
6 is provided. The solenoid of the purge control valve 16 is connected to the ECU 5, and the purge control valve 16 is controlled according to a signal from the ECU 5 to linearly change the valve opening amount. According to this fuel evaporative emission control device, the fuel evaporative emission (fuel vapor) generated in the fuel tank 8 pushes the positive pressure valve of the two-way valve 14 when it reaches a predetermined set pressure, and flows into the canister 15. Then, it is adsorbed and stored by the adsorbent 151 in the canister 15. The purge control valve 16 is closed when the solenoid is not energized by the control signal from the ECU 5, but when the solenoid is energized according to the control signal, the valve is opened according to the energizing amount. The purge control valve 16 is opened by the amount, and the canister 1
Due to the negative pressure in the intake pipe 2, the vaporized fuel temporarily stored in the intake air intake port 5 has an outside air intake port 152 provided in the canister 15.
The air is sucked into the intake pipe 2 through the purge control valve 16 together with the outside air sucked from and is sent to each cylinder. Further, when the fuel tank 8 is cooled by the outside air and the negative pressure in the fuel tank 8 increases, the negative pressure valve of the two-way valve 14 opens, and the evaporated fuel temporarily stored in the canister 15 is stored in the fuel tank 8
Returned to. In this way, the fuel evaporative gas generated in the fuel tank 8 is prevented from being released to the atmosphere.

An orifice 171 is provided on the purge control valve 16 side of a purge pipe 17 connecting the canister 15 and the purge control valve 16. Further, a pressure gauge 19 is installed in the purge pipe 17 between the orifice 171 and the purge control valve 16 via a pipe 18. The pressure gauge 19 and the orifice 171 constitute a differential pressure flowmeter. The pressure gauge 19 is composed of an atmospheric pressure differential pressure gauge, and has a purge pipe 1 for the atmospheric pressure.
The relative pressure P1 in 7 is detected and the detection signal is detected by the ECU 5
Supply to. In this differential pressure flowmeter, the ECU 5 calculates the combined air vapor flow rate Q passing through the orifice 171 by the jet area of the orifice 171 and the relative pressure P ₁ detected by the pressure gauge 19.

Further, the canister 15 and the orifice 17
A hot-wire type flow meter (mass flow meter) 20 is provided in the purge pipe 17 between 1 and 1, and an output signal corresponding to the flow rate of the air-fuel mixture (purge gas) containing the fuel evaporative gas flowing in the purge pipe 17 is sent to the ECU 5. Supply. This hot wire type flow meter 20 utilizes the fact that when a platinum wire heated by passing an electric current is exposed to an air stream, the platinum wire is deprived of heat to lower its temperature and its electric resistance decreases.

In the purge pipe 17 between the hot wire type flow meter 20 and the canister 15, the differential pressure flow meter and the hot wire type flow meter 2 are provided.
Atmosphere intake port 2 when a predetermined condition described below is satisfied
A switching valve 21 for supplying the air taken in from 11 is provided. A control signal is supplied to the switching valve 21 from the ECU 5, and when the pressure gauge 19 or the hot-wire flow meter 20 changes with time, a correction coefficient to be described later is set.
The control signal causes the switching valve 21 to switch to the side where the air intake port 211 takes in fresh air.

The ECU 5 shapes the waveforms of the input signals from various sensors, corrects the voltage level to a predetermined level, converts the analog signal value into a digital signal value, and the like, a correction coefficient VQKO described later. ₂ and EPCV value calculation program and a central processing circuit (hereinafter referred to as “CPU”) that executes a program for setting the correction coefficient when the predetermined condition is satisfied, various calculation programs executed by the CPU, a Ti map described later, and Storage means for storing the calculation result, the correction coefficient, etc., the fuel injection valve 6,
The purge control valve 16 includes an output circuit that supplies a drive signal.

The CPU discriminates various engine operating states such as a feedback control operating region and an open loop control operating region according to the oxygen concentration in the exhaust gas based on the engine operating parameter signals from the various sensors mentioned above, and Based on the following equation (1) according to the operating state,
The fuel injection time Tout of the fuel injection valve 6 is calculated in synchronization with the TDC signal pulse.

Tout = Ti × KO ₂ × VQKO ₂ + K1 + K2 (1) Here, Ti is a reference value of the fuel injection time Tout of the fuel injection valve 6, and is the engine speed NE and the intake pipe absolute pressure P.
It is read from the Ti map set according to BA.

KO ₂ is an air-fuel ratio feedback correction coefficient and is set according to the oxygen concentration in the exhaust gas detected by the O ₂ sensor 12 during feedback control, and a plurality of open loop control operations without feedback control are performed. In the region, it is a coefficient set according to each operating region.

VQKO ₂ is a vapor flow rate correction coefficient and is a value set in accordance with the vapor flow rate detected when purging is being executed. The details will be described later with reference to FIG.

K1 and K2 are other correction coefficients and correction variables calculated according to various engine operating parameter signals, respectively, and optimization of various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to the engine operating state is performed. Is set to a predetermined value.

The CPU supplies a drive signal for opening the fuel injection valve 6 based on the fuel injection time Tout obtained as described above to the fuel injection valve 6 via the output circuit.

2 and 3 show the vapor flow rate correction coefficient VQ.
Shows a flowchart of the calculation program of KO ₂ and EPVC value, which is executed in the CPU.

In step S1 of FIG. 2, it is determined whether or not "1" is set in the flowmeter correction flag. This is because the correction due to the deterioration of the pressure gauge 19 and the hot-wire flowmeter 20 which configure the purge flowmeter is executed only once from the time when the engine 1 is started to the time when the engine 1 is stopped. It is to determine whether or not it is being executed.

"1" is set in the flowmeter correction flag,
If the correction has already been performed, the following correction steps S2 to S5 are skipped and the process proceeds to step S6 in FIG.

If "1" is not set in the flowmeter correction flag and the correction has not been made yet, the process proceeds to the next step S2.

In step S2, it is determined whether or not the engine operating condition is such that the flow meter correction condition is satisfied. This is because after the engine 1 is started, the output of the flow meter is corrected after waiting for the operating state to become stable, and the operating state of the engine 1 does not satisfy the conditions described below and is stable. If not, the flow meter output correction is not performed and the process proceeds to step S6 in FIG.

The conditions indicating a stable operating state of the engine 1 are as follows, for example. That is, first, the engine cooling water temperature TW detected by the engine water temperature sensor 22.
Is larger than the predetermined value A, and the engine 1 is at a high temperature. Secondly, the absolute value | ΔNE | of the fluctuation amount ΔNE of the engine speed NE of the engine 1 detected by the engine speed sensor 11 is a predetermined value. It is smaller than B, and thirdly, the absolute value | ΔPBA | of the variation amount ΔPBA of the intake pipe absolute pressure PBA detected by the absolute pressure sensor 10 is smaller than the predetermined value C. When all of the first to third conditions are satisfied, it is determined that the engine 1 is in a stable operating state, and the routine proceeds to step S3 and subsequent steps for correcting the flow meter output.

In step S3, the switching valve 21 is switched to the fresh air side and fresh air is taken into the purge pipe 17 from the air intake port 211. As a result, the gas in the purge pipe 17 has a vapor concentration β = 0% (atmosphere 100%). At this time,
As is clear from the graph of FIG. 4 described later, the hot wire type flow meter coefficient KH and the differential pressure flow meter coefficient KS are adjusted to be equal. If this adjustment goes wrong due to changes over time, the displayed values of both flowmeters will differ. If there is a discrepancy between the display values of both flowmeters, it is corrected in step S4.

[0034] At step S4, comparing incorporation and display value Q ₂ of the display value Q _1, differential pressure flow meter of hot-wire flow meter 22 to the CPU. Assuming that the air flow rate at this time is QA and the correction coefficients of the display values of each flow meter are K ₁ and K ₂ , respectively, the corrected display values QH = Q ₁ × 1 / K ₁ and QS = Q ₂ × 1 / K ₂ is equal, QA = QH = QS = Q ₁ / K ₁ = Q ₂ / K ₂ , and from this equation, the correction coefficient K _{1 is set} so as to satisfy the relationship of K ₁ = (Q ₁ / Q ₂ ) × K _2. , K ₂ are set, the display values of both flowmeters match. The correction coefficients K ₁ and K ₂ set so as to satisfy the relationship of the above equation are stored in the storage means of the ECU 5.

The switching valve 21 is switched to the fresh air side,
When the vapor concentration β becomes 0%, the display value Q of both flow meters
_{When 1} and Q ₂ match, no abnormal phenomenon such as aging has occurred in each flow meter, so the correction coefficients K ₁ and K ₂ are stored in the storage means as K ₁ = K ₂ = 1. To be done.

In step S5, the flow rate correction flag is set to "1" to indicate that the flow rate has been corrected.

In step S6 of FIG. 3, the air amount QENG taken into the engine 1 is calculated by the following equation (2).

QENG = Tout × NE × CEQ (2) Here, Tout is the fuel injection time calculated by the equation (1), and CEQ is a constant for converting into the intake air amount.

In step S7, the target vapor flow rate ratio K
QPOBJ is searched for a KQPOBJ map according to the detected engine speed NE and the intake pipe absolute pressure PBA. KQPOBJ map shows the engine intake air amount QEN
6 is a map in which a target vapor flow rate ratio with respect to G is set corresponding to a plurality of predetermined engine speeds NE and an intake pipe absolute pressure PBA.

In step S8, the engine intake air amount QENG and the target vapor flow rate ratio KQPOBJ are applied to the following equation (3) to calculate the target vapor flow rate QPOBJ. QPOBJ = QENG × KQPOBJ (3) This target vapor flow rate QPOBJ may be appropriately corrected by the engine water temperature TW.

In step S9, the actual value of the vapor flow rate VQ of the purge pipe 17 due to the fuel vapor (vapor) discharged from the canister 15 to the purge pipe 17 is calculated. The vapor flow rate VQ discharged from the canister 15 to the purge pipe 17 depends on the fuel vapor (vapor) adsorbed to the canister 15 coming from the fuel tank 8 and directly adsorbed by the canister 15 from the fuel tank 8. It is the vapor flow rate that is the sum of those without passing through the orifice 171. A method of calculating the actual value of the vapor flow rate VQ will be described later.

In step S10, the vapor flow rate correction coefficient VQKO _{2 is} calculated based on the calculated actual vapor flow rate VQ.
To calculate. That is, first, the vapor flow rate V is calculated based on the following equation (4).
Q (l / min) is equivalent to gasoline weight in liquid state GV
Convert to Q (g / min).

[Equation 1] KVQ is a coefficient indicating the ratio of the gasoline vapor flow rate (l / min) included in the vapor flow rate VQ (l / min), and is 1 / 1.69. VMOL is 1 molar volume value,
It is represented by 22.4 l / MOL value at 0 ° C. Gasoline vapor molecular weight is about 64. Using the gasoline weight equivalent GVQ (g / min) thus obtained, the vapor flow rate correction coefficient VQKO ₂ is calculated based on the following equation (5).

[0043]

[Equation 2] The basic injection weight is a value obtained by converting the reference value Ti of the fuel injection time into the fuel weight (g).

Vapor flow rate correction coefficient VQ thus obtained
KO ₂ is 1.0 when the purge control valve 16 is closed and when the purge is cut, and becomes 1.0 or less when the purge control valve 16 is opened and the purge is executed. Using this value, the fuel injection time Tout is calculated based on the equation (1), and the fuel injection valve 6 supplies the engine 1 with the fuel amount for suppressing the fluctuation of the air-fuel ratio due to the magnitude of the purge amount. To be done.

Further, in step S11, step S
It is determined whether or not the vapor flow rate VQ calculated in 9 is greater than or equal to the target vapor flow rate QPOBJ calculated in step S8.

The answer to step S11 is negative (NO), that is, the calculated vapor flow rate VQ is the target vapor flow rate QPOBJ.
If it is smaller, the control amount EPCV value corresponding to the valve opening amount of the purge control valve 16 is increased by the value C from the current value in order to increase the vapor amount to increase the fuel vapor emission suppression capability (step S12), This program ends.
The value C is an update constant of the EPCV value. On the other hand, step S1
The answer of 1 is affirmative (YES), that is, the calculated vapor flow rate V
If Q is equal to or more than the target vapor flow rate QPOBJ, the vapor amount is decreased to prevent the feedback control from being deteriorated in responsiveness, and the control amount EPCV value of the purge control valve 16 is decreased from the current value by the value C (step S13), this program ends.

As described above, in the present embodiment, when the flowmeter is deteriorated, the displayed value is corrected, the actual vapor flow rate VQ is detected, and the fuel injection amount is corrected accordingly. Then, (step S10), the variation of the air-fuel ratio due to the purge is prevented, and the opening amount of the purge control valve 16 is controlled according to the detected vapor flow rate (step S1).
2, S13) The average value of the air-fuel ratio correction coefficient KO ₂ is prevented from deviating significantly from the value of 1.0. As a result, the display error of the flow meter is removed, and the average value used as the initial value of the air-fuel ratio correction coefficient KO ₂ when the air-fuel ratio control shifts from the open loop mode to the feedback mode is a value.
It is possible to prevent the responsiveness of feedback control from deteriorating when it deviates significantly from 1.0.

Next, a method of calculating the actual value of the vapor flow rate VQ in step S9 of FIG. 3 will be described. In order to calculate the vapor flow rate VQ, in the present embodiment, the total flow rate (volume flow rate) of the air vapor flowing in the purge pipe 17 (the vapor flow rate VQ due to the fuel vapor (vapor) discharged from the canister 15 and the outside air removal of the canister 15). Flow rate Q'combined with the air flow rate Q'of the air sucked from the inlet 152) Q
Then, the vapor concentration contained in the total flow rate Q is obtained.

In this embodiment, the vapor flow rate VQ is calculated according to the volume flow rate Q and the vapor concentration, and the volume flow meter 19 shown in FIG.
171 and the output of the mass flowmeter 22. Both of these two different types of flowmeters have different output characteristics with respect to changes in the density (vapor concentration) of the gas to be measured (vapor mixture). For example, the gas to be measured is 100% air.
Shows a different output value (display amount) even when the volumetric flow rate is the same (when the density is low) and when the vapor (HC) is 100% (high density). When the air is 100%, the output value is small and the vapor 100%. When, the output value is large. Further, the change curve of the output characteristic with respect to the change of the density of the gas to be measured, that is, the vapor concentration also differs between the volume flow meter and the mass flow meter.
For example, when the evaporative mixture is 100% air, the output display amount of both flowmeters is 1.0 as described above, while when the vaporized mixture is 100%, the volume flowmeter is 1.69, whereas the mass flowmeter is. Indicates 4.45.

The present embodiment utilizes the fact that the output characteristics differ depending on the vapor concentration of the vaporized mixture depending on the type of the flow meter.
Based on the outputs of the two types, in this embodiment, the volume flow meter and the mass flow meter, the volume flow rate Q of the evaporative mixture, the vapor concentration β,
As a result, the vapor flow rate VQ is measured.

The method of calculating the vapor flow rate VQ of this embodiment will be described in more detail below.

The combined air vapor flow rate Q at an arbitrary vapor concentration measured by the above two flow meters is expressed by the following equations (6) and (7).

[0053]

[Equation 3]

[0054]

[Equation 4] Here, as described above, QH is the corrected display value of the hot-wire type flow meter 22 (the display amount of the volume flow rate), QS is the corrected display value of the differential pressure flow meter (the display amount of the volume flow rate), KH
And KS are a hot-wire type flow meter coefficient and a differential pressure flow meter coefficient, which are determined by the vapor concentration (volume ratio), and KH and KS are experimentally obtained coefficients, for example, vapor concentration β = 0. When KH = KS = 1
Both flowmeters are adjusted so that The relationship between KH and KS and the above vapor concentration β is shown in the graph of FIG. Figure 4
, Solid lines Sa and Sb indicate the differential pressure flowmeter coefficient and the hot wire type flowmeter coefficient, respectively, and the dotted line Sc indicates KH.
The value of / KS = α is shown. The following expression (8) is established from the expressions (6) and (7).

[0055]

[Equation 5] That is, α is obtained from the display values QH and QS of the hot wire type flowmeter 22 and the differential pressure flowmeter, and therefore the vapor concentration β in the evaporative mixture is obtained from FIG. Further, since KH and KS are also obtained from FIG. 4 according to the concentration β, the total air vapor flow rate Q is also obtained from the equation (6) or (7). From the above Q and β, the vapor flow rate VQ (l / min) is obtained by the following equation (9).

VQ = Q × β (β ≦ 1) (9) By substituting this VQ value into the equation (4), the gasoline weight equivalent flow rate GVQ can be obtained. Therefore, from the equation (5), the vapor flow rate correction coefficient VQKO ₂ Is required.

In this way, V = can be calculated by varying α = QH / QS depending on the vapor concentration.

When the flowmeter deteriorates, the coefficient K in FIG.
The solid line Sa representing S has a deviation of the inclination, and the solid line Sb representing the coefficient KH has a drift, which causes a detection error of the flowmeter. Especially in the case of the drift of the solid line Sb,
The lower the purge flow rate, the larger the detection error rate. The present invention corrects such a display error.

FIG. 5 is a flow chart showing a program for executing the calculation operation of the vapor flow rate VQ. First, the corrected display values QS and QH of each flow meter are set to the ECU 5
It is stored in the storage means (step S21). Next, EC
U5 finds α from QS and QH by the equation (8) (step S22), and searches KS, KH, and β from this α (step S23). Only one of KS and KH need be searched.

Next, the ECU 5 sends QH and KH or QH.
Q is obtained from S and KS (step S24), and VQ is obtained from Q and β (step S25). That is, the vapor flow rate VQ is obtained from the flow rates QS and QH. This is shown in FIG. Therefore, if the value of VQ corresponding to each value of QS and QH is stored in the storage means as a map, it is not necessary to calculate VQ each time, and the processing is speeded up.

Although the differential pressure flowmeters 19 and 171 and the hot wire type flowmeter 22 are connected in series in the embodiment of FIG. 1, both flowmeters may be connected in parallel, In the embodiment, the vapor concentration β and the total flow rate Q are first obtained, and the vapor flow rate VQ is obtained from this, but the present invention is not limited to this, and for example, from the map of QS and QH, V
Q is calculated from another map of QS and QH, and VQ and Q
Therefore, the vapor concentration may be obtained from VQ / Q = β.

Further, in the above embodiment, the combination of the differential pressure flowmeter and the hot wire type flowmeter has been described, but the present invention is not limited to this, and it suffices that the two flowmeters have different output characteristics with respect to the vapor concentration. An ultrasonic flowmeter, a vortex flowmeter, etc. can be combined as appropriate.

[0063]

As described above, according to the present invention,
At the time of deterioration of the purge flow meter, the atmosphere is supplied to the purge flow meter by the atmosphere supply means, and the output of the purge flow meter is corrected based on the output of the purge flow meter at the time of supplying the atmosphere. It is not necessary to immediately repair or replace the flow meter, and the supply of purge gas to the engine can be properly controlled, and therefore deterioration of exhaust gas characteristics and reduction of purge efficiency can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a part of a program for executing the operation of the embodiment of FIG.

FIG. 3 is a flowchart showing a part of a program for executing the operation of the embodiment of FIG.

FIG. 4 is a graph showing a relationship between a flow meter coefficient and vapor concentration.

FIG. 5 is a flowchart showing a procedure for calculating a vapor flow rate.

FIG. 6 is a graph for obtaining a vapor flow rate from respective flow rate display values of a differential pressure flowmeter and a hot wire type flowmeter.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Intake Pipe 5 Electronic Control Unit (ECU) 6 Fuel Injection Valve 8 Fuel Tank 15 Canister 16 Purge Control Valve 17 Purge Pipe 19 Pressure Gauge 20 Hot Wire Flowmeter 21 Switching Valve 22 TW Sensor 171 Orifice 211 Air Intake Port

Claims (1)

Claim: What is claimed is: 1. A purge passage, which is provided between a canister for adsorbing fuel evaporative gas generated from a fuel tank and an engine intake system, for purging the fuel evaporative gas, and the purge passage. In an evaporative fuel control device for an internal combustion engine having a purge control valve for controlling a flow rate of the fuel evaporative gas supplied to an engine intake system, an output characteristic is provided in the purge passage and is dependent on a concentration of the fuel evaporative gas. Of the purge flow meter, an atmosphere supply means for supplying the atmosphere to the purge flow meter under a predetermined condition, and an output for correcting the output of the purge flow meter based on the output of the purge flow meter at the time of supplying the atmosphere. An evaporated fuel control apparatus for an internal combustion engine, comprising: a correction unit.