JPH0734921A - Fuel supply controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To maintain base air-fuel ratio stably in the vicinity of target air-fuel ratio by computing fuel supply amount by estimating air amount and fuel amount to be supplied by canister purge. CONSTITUTION:An intake air amount detection means detects the amount of intake air amount of an engine, and an engine speed detection means detects engine speed. A purge air amount assumption means assumes purge air amount to be supplied via a purge passage from the detected intake air amount and engine speed. Also, a fuel concentration detection means detects concentration of fuel in the purge passage. On the other hand, a fuel supply amount computing means computes fuel supply amount based on the detected intake air amount and engine speed. A fuel supply amount compensating means compensates the computing of fuel supply amount in the fuel supply amount computing means based on purge air amount assumed by the purge air amount assumption means and concentration of fuel detected by the fuel concentration detection means. As a consequence, it is possible to compensate fuel supply amount to a value obtained by estimating influence of canister purge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly to an internal combustion engine equipped with a canister that adsorbs and collects evaporated fuel in a fuel tank, in consideration of the effect of canister purge. The present invention relates to a technique for improving the control accuracy of supply amount.

[0002]

2. Description of the Related Art Conventionally, after the evaporated fuel generated in a fuel tank is once adsorbed and collected by a canister, the evaporated fuel adsorbed and collected by the canister is purged (desorbed) and supplied to an internal combustion engine. There has been proposed a system for preventing the vaporized fuel in the fuel tank from being diffused into the atmosphere (see Japanese Patent Laid-Open No. 62-7962, etc.).

[0003]

By the way, in an engine equipped with a canister as described above, when the canister is purged, excess fuel is supplied into the cylinder by that amount, and the air-fuel ratio is overriched. Will be changed. Here, in the fuel supply device having the air-fuel ratio feedback control function, the enrichment accompanying the canister purge will be compensated by the air-fuel ratio feedback control, but until the air-fuel ratio feedback control effectively operates, The amount of HC and CO in the exhaust gas will increase.

Further, when the air-fuel ratio learning control function is provided, the correction level required in connection with the canister purge is learned, but the canister purge is always performed in the operating region where such learning is performed. Not always
Further, even if the canister purge is performed, the amount of fuel supplied by the purge fluctuates, so that the next time the vehicle is operated in the same operating region, it is affected by the situation of the canister purge and the air-fuel ratio learning correction value There is an excess or deficiency in the correction level. Then, the exhaust property deteriorates until the air-fuel ratio deviation caused by the excess or deficiency of the correction level is compensated by the air-fuel ratio feedback control.

As described above, it is difficult to stably avoid the air-fuel ratio deviation due to the canister purge by the air-fuel ratio feedback control and the air-fuel ratio learning control. Further, conventionally, a system for performing a failure diagnosis of the fuel supply system based on the result of the air-fuel ratio learning has been proposed, but as described above, when the enrichment of the air-fuel ratio accompanying the canister purge is learned. However, there is also a problem that the diagnosis accuracy is deteriorated by making a diagnosis based on the learning result.

The present invention has been made in view of the above problems, and even if the canister purge is performed, the air-fuel ratio is stabilized by setting the fuel supply amount in consideration of the fuel amount supplied by the canister purge. An object of the present invention is to provide a fuel supply control device that can be maintained.

[0007]

Therefore, a fuel supply control device for an internal combustion engine according to the present invention adsorbs and collects evaporated fuel in a fuel tank, purges the adsorbed and collected evaporated fuel, and purges the purged air. A fuel supply control device for an internal combustion engine, comprising a canister for supplying the intake air passage of the internal combustion engine through a purge passage, which is configured as shown in FIG.

In FIG. 1, intake air amount detecting means detects the intake air amount of the engine, and rotation speed detecting means detects the rotation speed of the engine. The purge air amount estimating means estimates the amount of purge air supplied through the purge passage from the detected intake air amount and rotation speed. Further, the fuel concentration detecting means detects the fuel concentration in the purge passage.

On the other hand, the fuel supply amount calculation means calculates the fuel supply amount based on the detected intake air amount and rotation speed. Then, the fuel supply amount correction means corrects the calculation of the fuel supply amount in the fuel supply amount calculation means based on the purge air amount estimated by the purge air amount estimation means and the fuel concentration detected by the fuel concentration detection means. To do.

[0010]

According to the fuel supply control device having such a configuration, the amount of purge air supplied through the purge passage is estimated from the amount of intake air and the rotation speed, whereby the amount of air actually sucked into the engine is calculated. The amount supplied through the purge passage is detected. On the other hand, since the fuel concentration in the purge passage is detected, it is possible to estimate the amount of fuel supplied to the engine together with the purge air based on the estimated purge air and the fuel concentration. The fuel supply amount calculated independently of the purge can be corrected to a value that allows for the influence of the canister purge.

[0011]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, air is drawn into the internal combustion engine 1 through a throttle chamber 2 and an intake manifold 3. The throttle chamber 2 is provided with a throttle valve 4 interlocking with an accelerator pedal (not shown) to control the intake air amount of the engine 1.

An electromagnetic fuel injection valve 5 is provided for each cylinder at a branch portion of the intake manifold 3, and fuel which is pressure-fed from a fuel pump (not shown) and is controlled to a predetermined pressure by a pressure regulator is introduced into the intake manifold 3.
Inject and supply. The fuel injection valve 5 is intermittently driven to open according to an injection pulse signal sent from a control unit 6 having a built-in microcomputer, and fuel is supplied according to the pulse width of the injection pulse signal calculated by the control unit 6. The amount is controlled.

A spark plug 7 is provided in each cylinder of the internal combustion engine 1, and a high voltage generated in an ignition coil 8 is sequentially applied to these cylinders through a distributor 9, whereby spark ignition is performed. The mixture is ignited and burned. Here, the ignition coil 8 is configured such that the generation timing of the high voltage is controlled via the attached power transistor 10.

The throttle valve 4 has an opening TVO.
Sensor that detects the pressure with a potentiometer
11 are attached. A crank angle sensor 12 (rotational speed detecting means) built in the distributor 9 outputs a detection signal for each predetermined crank angle, and the engine rotation speed Ne can be calculated based on the detection signal.

Further, the cooling water jacket of the engine 1 has a water temperature sensor for detecting a cooling water temperature Tw representative of the engine temperature.
13 is provided, the exhaust manifold 14 is provided with an oxygen sensor 15 for detecting the oxygen concentration in the exhaust gas, which has a close relationship with the air-fuel ratio of the intake air-fuel mixture of the engine 1, and further, at the upstream side of the throttle chamber 2. An air flow meter 33 (intake air amount detecting means) for detecting the intake air amount Q _A of the engine 1 is provided in the intake duct portion.

On the other hand, the engine 1 is provided with an evaporative gas treatment device 21 for the fuel tank 20. The evaporative gas treatment device 21 causes the adsorbent 23 such as activated carbon filled in the canister 22 to adsorb and collect the evaporative gas of the fuel generated in the fuel tank 20 to collect the fuel adsorbed by the adsorbent 23. Purging is performed and the purge air is supplied to the intake passage downstream of the throttle valve 4 via the purge passage 24.

The purge passage 24 is provided with an HC sensor (fuel concentration detecting means) 34 for detecting the fuel concentration in the purge air flowing through the purge passage 24. The canister 22 has an evaporative gas passage in which a check valve 25 that opens when the positive pressure in the fuel tank 20 exceeds a predetermined value is provided.
The evaporative gas in the fuel tank 20 is introduced through the pressure passage 26, and the purge passage 24 has a pressure chamber in which throttle negative pressure or atmospheric pressure is introduced through the reference pressure introduction passage 27. A diaphragm valve 28 having the above is interposed.

The diaphragm valve 28 opens the purge passage 24 against the closing biasing force of the spring 28a when a negative pressure is applied to the pressure chamber, and closes the spring 28a when the pressure chamber becomes atmospheric pressure. The purge passage 24 is closed by closing the valve by the valve biasing force. Here, in order to selectively apply a throttle negative pressure to the pressure chamber of the diaphragm valve 28, a purge control solenoid 29 whose current is controlled by the control unit 6 is interposed in the reference pressure introducing passage 27.

The purge control solenoid 29 is
In the off (open) state, the negative pressure introducing passage 30 for introducing the throttle negative pressure is communicated with the reference pressure introducing passage 27, and in the on (closed) state, atmospheric pressure is introduced from the upstream side of the throttle valve 4. The atmospheric pressure introducing passage 31 and the reference pressure introducing passage 27 are connected to each other. Therefore, by turning on / off the purge control solenoid 29, it is possible to switch between the negative pressure of the throttle valve and the atmospheric pressure and introduce the same into the pressure chamber of the diaphragm valve 28, whereby the opening / closing of the purge passage 24 is electronically controlled by the control unit 6. You can do it.

The control unit 6 opens and closes the purge passage 24 (canister purge) based on operating conditions such as the coolant temperature Tw detected by the water temperature sensor 13 and the vehicle running speed VSP detected by the vehicle speed sensor 32. conditions)
Is determined, and the purge control solenoid 29 is turned on / off according to the determination result. Here, the state of the fuel injection control by the control unit 6 is shown in FIG.
It will be described in accordance with the flowchart of.

In the present embodiment, the functions of the purge air amount estimating means, the fuel supply amount calculating means, and the fuel supply amount correcting means are provided by software in the control unit 6 as shown in the flow chart of FIG. . In the flowchart of FIG. 3, step 1 (in the figure, S
It is set as 1. The same applies hereinafter), by determining whether the purge control solenoid 29 is on or off,
It is determined whether the canister purge is being performed.

When the canister purge is not performed, the routine proceeds to step 6, where the engine calculated based on the intake air amount Q _A detected by the air flow meter 33 and the output signal from the crank angle sensor 12. Based on the rotation speed Ne, the basic injection pulse width Tp (← K × Q _A / Ne: K
Is a constant). Next, in step 7, the air-fuel ratio feedback correction coefficient α, which is set so that the actual air-fuel ratio approaches the target air-fuel ratio based on the detection result of the oxygen sensor 15, and the air-fuel ratio feedback correction coefficient α are learned for each operating region. Based on the obtained air-fuel ratio learning correction coefficient KBLRC, various correction coefficients COEF set according to operating conditions such as cooling water temperature Tw, and correction amount Ts due to battery voltage, the basic injection pulse width Tp (basic fuel supply amount )
And the final injection pulse width Ti (← Tp × α × K
BLRC × COEF + Ts) is obtained.

Then, in the next step 8, an injection pulse signal having a pulse width corresponding to the injection pulse width Ti (fuel supply amount) is output to the fuel injection valve 5 at a predetermined injection timing, and the fuel injection valve 5 Control the fuel injection by. On the other hand, when it is determined in step 1 that the canister purge is being performed, the process proceeds to step 2 and is calculated based on the intake air amount Q _A detected by the air flow meter 33 and the output signal from the crank angle sensor 12. based on the has been the engine speed Ne, to estimate the purge air quantity Q _P supplied via the purge passage 24.

Here, the gas is supplied through the purge passage 24.
Purge air is not detected by the air flow meter 33.
Is the air added on the way, and the true engine intake air amount
Is the air amount Q detected by the air flow meter 33._ATo
The estimated purge air amount Q _PIt becomes the amount which added.
Therefore, in order to form the desired air-fuel ratio mixture,
Q_A+ Q_PThe basic injection pulse width Tp is calculated according to
In the next step 3, Tp ← K × (Q
_A+ Q_P) / Ne (K is a constant) basic injection pulse width
Calculate Tp.

The basic injection pulse width Tp is an appropriate value when the fuel is not mixed in the purge air, but in reality, the fuel (evaporated fuel generated in the fuel tank) is mixed in the purge air and supplied. The fuel in the purge air will be additionally supplied. Therefore, the sum of the fuel injected and supplied from the fuel injection valve 5 and the fuel supplied by the canister purge is subtracted from the basic injection pulse width Tp by subtracting the amount corresponding to the amount of fuel supplied together with the purge air. It is necessary to set a predetermined amount corresponding to the air Q _A + Q _P.

Therefore, in the next step 4, the amount of fuel supplied through the purge passage 24, which is estimated based on the purge air amount Q _P and the fuel concentration in the purge passage 24 detected by the HC sensor 34, is the pulse width of the injection pulse signal outputted to the fuel injection valve 5 Tpp (← K × fuel concentration × Q _P /
Calculate as Ne). In step 5, the basic injection pulse width T calculated by considering the purge air amount as described above.
The pulse width Tpp corresponding to the amount of fuel added through the purge passage 24 is subtracted from p, and the subtraction result is used for the actual fuel injection control.
pp). Then, the process proceeds to steps 7 and 8 to execute the fuel injection control based on the basic injection pulse width Tp calculated in the step 5.

The basic injection pulse width Tp calculated in step 5 is a value that allows for the amount of air and the amount of fuel supplied through the purge passage 24 during canister purging,
As a result, even when the purge air is supplied from the purge passage 24, the base air-fuel ratio obtained without the air-fuel ratio correction control can be maintained at the target air-fuel ratio. Therefore, a large change in the air-fuel ratio does not occur due to the canister purge, it is possible to avoid deterioration of the exhaust property when the canister purge is performed, and the air-fuel ratio learning erroneously learns the air-fuel ratio deviation due to the canister purge. Therefore, the accuracy of the fuel system diagnosis based on the result of the air-fuel ratio learning can be improved.

Incidentally, in the evaporative gas treatment apparatus 21 of this embodiment,
Although the configuration is such that the purge passage 24 is opened and closed by a diaphragm type valve, the purge passage 24 may be opened and closed directly by a solenoid valve, and the canister purge is not electronically controlled but the engine load is not controlled. The purge passage may be opened by the diaphragm valve when the pressure is equal to or higher than a predetermined value.

[0029]

As described above, according to the present invention, the fuel supply amount is calculated in consideration of the air amount and the fuel amount supplied by the canister purge. Therefore, even when the canister purge is performed, Since the air-fuel ratio can be stabilized near the target air-fuel ratio, the deterioration of the exhaust property due to the canister purge can be avoided, and the air-fuel ratio learning is not affected by the canister purge due to the stabilization of the base air-fuel ratio. There is an effect that the accuracy of diagnostic control using the result of the air-fuel ratio learning can be improved.

[Brief description of drawings]

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

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing a fuel injection control of the above embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 6 Control Unit 12 Crank Angle Sensor 13 Water Temperature Sensor 20 Fuel Tank 21 Evaporative Gas Treatment Device 22 Canister 23 Adsorbent 24 Purge Passage 28 Diaphragm Valve 29 Purge Control Solenoid 32 Vehicle Speed Sensor 33 Air Flow Meter 34 HC Sensor

Claims (1)

[Claims] 1. An internal combustion engine having a canister that adsorbs and collects evaporated fuel in a fuel tank, purges the adsorbed and collected evaporated fuel, and supplies the purge air to an intake passage of an internal combustion engine through a purge passage. A fuel supply control device for an engine, comprising: an intake air amount detecting means for detecting an intake air amount of the engine; a rotation speed detecting means for detecting a rotation speed of the engine; and the intake air amount and the rotation speed thus detected. On the basis of the purge air amount estimating means for estimating the purge air amount supplied through the purge passage, the fuel concentration detecting means for detecting the fuel concentration in the purge passage, and the detected intake air amount and rotation speed. Based on the fuel supply amount calculation means for calculating the fuel supply amount, the purge air amount estimated by the purge air amount estimation means, and the fuel concentration detected by the fuel concentration detection means. The fuel supply amount calculation means fuel supply amount correcting means and the fuel supply control system for an internal combustion engine, characterized in that it is configured to include a correcting calculation of the fuel supply amount in Te.