JP2964118B2 - Evaporative fuel control 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 evaporative fuel control system for an internal combustion engine in which fuel vapor is temporarily stored in a fuel tank and is taken into a suction system of the engine while controlling the amount of suction under predetermined engine operating conditions. .

[0002]

2. Description of the Related Art As a measure for regulating the amount of evaporative fuel generated from a fuel tank, the evaporative fuel is temporarily adsorbed by an adsorbing means called a canister, and the adsorbed fuel is suction-negative-pressured in a predetermined engine operating state. A system has been considered in which the fuel is sucked (purged) into the intake system for combustion treatment. Although the system itself is mounted on an actual vehicle, a recent measure is to start purging from a state in which the canister is filled with evaporative fuel so as to reliably prevent the evaporative fuel from being released from the canister. It is a harsh condition that it is required to perform combustion treatment and keep the emission amount within the regulation value.

[0003]

When such a large amount of fuel vapor is purged, the intake of the fuel vapor causes a large deviation in the air-fuel ratio in normal air-fuel ratio control.
To increase the emission of various exhaust polluting components, it is necessary to control the ratio of the amount of evaporative fuel suctioned to the amount of fuel supplied to the engine from the fuel supply means to maintain an appropriate air-fuel ratio. However, conventionally, such measures have not been sufficiently implemented.

The present invention has been made in view of such conventional problems, and detects the concentration of evaporated fuel sucked into an intake system of an engine from an adsorption means to supply the evaporated fuel to the engine or supply it to the engine. It is an object of the present invention to provide an evaporative fuel control device for an internal combustion engine that can maintain a good air-fuel ratio by correcting the amount of fuel to be supplied.

[0005]

For this reason, the air-fuel ratio control device of the internal combustion engine with the evaporative fuel control device according to the present invention, as shown in FIG. Then, in an evaporative fuel control device for an internal combustion engine, the stored evaporative fuel is sucked into the intake system of the engine while controlling the amount of suction under predetermined engine operating conditions .
Operating state detecting means B and operating state detecting means
According to the detected operating state of the engine, the fuel supply means C
Of fuel supplied to the engine and evaporation drawn into the intake system
A distribution ratio setting means D for setting a sharing ratio of the fuel amount, and the fuel vapor concentration detecting means E for detecting the concentration of fuel vapor drawn into the intake system from the suction means, the injection ratio setting means
The amount of evaporative fuel set based on the set share rate
Evaporation detected by the evaporative fuel concentration detection means
When the fuel concentration is higher than the fuel concentration,
When the fuel concentration is low and the fuel vapor concentration is low,
A first evaporative fuel amount correcting means F for performing increasing correction, machine
The air-fuel ratio of the mixture of fuel and air supplied to the
Air-fuel ratio detection means G, is detected by the air-fuel ratio detecting means that
Fuel supply means so that the adjusted air-fuel ratio approaches the target air-fuel ratio.
The amount of fuel supplied to the engine from the
Air-fuel ratio feedback correction means H for increasing / decreasing correction using
And the fuel vapor based on the feedback correction amount.
A second evaporative fuel amount correcting means I to increase or decrease correcting the amount, the first
The first evaporative fuel amount correcting means and the second evaporative fuel amount correcting means
And adjust the amount of evaporated fuel sucked into the intake system.
Means for controlling the amount of fuel vapor suction J to be controlled, and the concentration of the fuel vapor.
Fuel supply in accordance with the fuel vapor concentration detected by the detection means.
Correct and set the amount of fuel supplied to the engine from the supply means
And a fuel supply amount correcting means K.

[0006]

[0007]

[0008]

[0009]

According to the present invention, the share ratio setting means D responds to the operating state of the engine.
The amount of fuel supplied to the engine by the fuel supply means C
The share ratio with the amount of evaporated fuel sucked into the intake system is set,
The first evaporative fuel amount correction means F determines whether the set share ratio
Evaporated fuel concentration detection based on the amount of evaporative fuel set based on
The fuel vapor concentration is compared with the fuel vapor concentration detected by the means E.
When the fuel concentration is high, the amount of fuel vapor
When the degree is low, a correction for increasing the amount of evaporated fuel is performed. one
On the other hand, the air-fuel ratio feedback correction means H is an air-fuel ratio detecting means.
Let the air-fuel ratio detected by stage G approach the target air-fuel ratio
The amount of fuel supplied from the fuel supply means C to the engine
Increase / decrease correction using the feedback correction amount to obtain the second evaporated fuel amount.
The correction means I is based on the feedback correction amount.
The fuel vapor amount is increased or decreased. Then, the evaporated fuel intake amount
The control means J controls the first evaporated fuel amount correction means F and the second
Corrected by the evaporated fuel amount correction means I and sucked into the intake system
Control the amount of evaporative fuel that is taken
The correction means K determines the fuel amount set based on the share ratio.
Is the evaporative fuel detected by the evaporative fuel concentration detecting means E.
Is adjusted according to the material concentration, and the adjusted
An amount of fuel is supplied to the engine from the fuel supply means C. this
If so, the concentration of fuel vapor drawn into the intake system from the adsorption unit A will vary with the temperature condition and the like, for example, while the engine is stopped may be such as adsorption of the fuel vapor proceeds at a high temperature state, detection Is evaporated when the fuel concentration is high.
Reduce the amount of fuel intake and evaporate when the concentration of evaporated fuel is low.
By controlling to increase the amount of fuel generated ,
Fluctuations in the air-fuel ratio can be suppressed. Further, by correcting the evaporative fuel suction amount based on the deviation of the feedback correction amount from the reference value, the air-fuel ratio feedback control with high responsiveness can be performed by adjusting the amount of evaporative fuel in the gas state. Further, the air-fuel ratio can be set to an appropriate value by correcting and decreasing the amount of fuel from the fuel supply unit E by an amount corresponding to the amount of evaporative fuel suctioned based on the evaporative fuel concentration detection unit B.

[0010] Further, the fuel vapor intake amount is set based on the sharing ratio set by the sharing ratio setting means F, and the suction amount is controlled such that the set value is obtained based on the detected fuel vapor concentration. This makes it possible to control the amount of fuel vapor intake while setting an appropriate sharing ratio in accordance with the operating state detected by the operating state detecting means D. In the air-fuel ratio feedback control, the amount of evaporative fuel suction is corrected based on the deviation of the feedback correction amount from the reference value, so that the amount of evaporative fuel in the gaseous state is increased or decreased to provide a highly responsive air-fuel ratio feedback control. Control can be performed.

Further, in the second evaporative fuel control device for the internal combustion engine, the amount of fuel from the fuel supply means E is corrected to be reduced by an amount corresponding to the amount of evaporative fuel suctioned based on the evaporative fuel concentration detection means B. Thereby, an appropriate air-fuel ratio can be set. In this case, the fuel supply amount can be corrected with respect to the evaporated fuel amount which is naturally taken in without actively controlling the evaporated fuel. Needless to say, the present invention can also be applied to a device for controlling the amount of fuel vapor suction.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 3 showing a configuration of an embodiment, an intake passage 12 of an engine 11 is provided with an air flow meter 13 for detecting an intake air flow rate Q and a throttle valve 14 for controlling the intake air flow rate Q in conjunction with an accelerator pedal. In the downstream manifold part, an electromagnetic fuel injection valve as a fuel supply means for each cylinder
15 are provided.

The fuel injection valve 15 is driven to open by an injection pulse signal from a control unit 16 containing a microcomputer to inject and supply fuel. In addition, agencies
A water temperature sensor 17 for detecting a cooling water temperature Tw in the cooling jacket 11 is provided. On the other hand, the exhaust passage 18 is provided with an air-fuel ratio sensor 19 as an air-fuel ratio detecting means for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas at the manifold collecting portion. A three-way catalyst 20 is provided as an exhaust gas purifying catalyst for purifying by oxidizing CO and HC in exhaust gas and reducing NO _X.

A distributor (not shown in FIG. 3) has a built-in crank angle sensor 21. The crank unit angle signal output from the crank angle sensor 21 in synchronization with the engine rotation is counted for a predetermined time. Alternatively, the period of the crank reference angle signal is measured to detect the engine speed N. Incidentally, the air flow meter 13, the water temperature sensor 17, the crank angle sensor 21 and the like correspond to the operating state detecting means.

Next, the fuel supply system will be described. A fuel pump 23 is mounted in a fuel tank 22, and the fuel pump
The fuel fed from 23 is adjusted to a predetermined pressure through a fuel supply passage 25 with a pressure regulator 24 interposed, and is supplied to the fuel injection valve 15. Excess fuel from the pressure regulator 24 is returned to the fuel tank 22 via a return fuel passage 26.

The fuel vapor stored in the upper space of the fuel tank 22 is supplied to a fuel vapor passage 28 having a check valve 27 interposed therebetween.
Through the canister 29. The evaporative fuel temporarily adsorbed in the canister 29 is sucked into the intake passage 12 downstream of the throttle valve 14 through a purge passage 31 provided with a purge control valve 30 as evaporative fuel suction amount control means under predetermined operating conditions. Is done.

In the vicinity of a branch point between the purge passage 31 and the intake passage 12, a concentration sensor as evaporative fuel concentration detecting means for detecting the concentration of the evaporative fuel sucked into the intake passage 12.
32 is installed. The opening degree of the purge control valve 30 is set by the control unit 16 based on the condition including the evaporated fuel concentration detected by the concentration sensor 32, and the set opening control signal is transmitted to the control unit.
Controlled by input from 16.

Next, the air-fuel ratio control routine by the control unit 16 will be described with reference to the flowcharts of FIGS. 4 and 5 show an air-fuel ratio control routine in this embodiment. This routine is executed for a predetermined period (for example, 10
(2) It is performed every time. In step (denoted by S in the figure) 1, the amount of intake air per unit rotation is determined based on the intake air flow rate Q detected by the air flow meter 13 and the engine speed N calculated based on a signal from the crank angle sensor 21. the basic fuel injection pulse width T _P of the fuel injection valve 15 which is set in proportion to the computed according to the following equation.

T _P = K × Q / N (K is a constant) In step 2, various correction coefficients COEF are set based on the cooling water temperature Tw detected by the water temperature sensor 17. In step 3, the basic fuel supply quantity T _P to the various correction coefficients COEF to be multiplied by the effective fuel injection pulse width T
Calculate _e .

In step 4, a voltage correction value T _S is set based on the battery voltage value. This is for correcting a change in the injection flow rate of the fuel injection valve 15 due to the battery voltage fluctuation. In step 5, the ROM is set based on the engine speed N and the basic fuel injection pulse width _TP, and the ROM
And the share ratio k _SET of the evaporated fuel suction amount to the total fuel supply amount stored in the map of FIG. This step 5
Function corresponds to the sharing ratio setting means.

In step 6, a required fuel supply amount _QTE is obtained by multiplying the effective fuel injection pulse width _Te by a conversion constant m. In step 7, the target value Q _PA evaporative fuel intake amount by multiplying the allocation ratio k _SET to the required fuel supply amount Q _TE. Steps 5 to 7 described above correspond to claims 2 including a sharing ratio setting unit.

[0022] In step 8, reads the detection value Q _S from the density sensor 32. In step 9, it is set based on the engine rotational speed N and the basic fuel injection pulse width T _P, determined by searching the basic value P _A of the control duty of the purge control valve 30 stored in the map in advance ROM. In step 10, it compares the target value Q _PA and the detected value Q _S of the vaporized fuel inlet value.

If Q _PA > Q _S , the control duty integral value IPA of the purge control valve 30 is determined in step 11.
Was increased by a predetermined amount, when a Q _PA <Q _S, the step
In step 12, the control duty integral value IPA of the purge control valve 30 is reduced by a predetermined amount, and then the process proceeds to step 13, respectively, where Q _PA =
When a Q _S is, the process proceeds to step 13. In step 13, a feedback correction amount α of the air-fuel ratio set as described later during the air-fuel ratio feedback control is read, and a deviation Δ between the average value of the α and a reference value (for example, 1) is read.
Calculate α.

In step 14, it is determined whether or not the deviation Δα is larger than a predetermined positive value. If YES, the process proceeds to step 15 in which the feedback correction LPA of the control duty of the purge control valve 30 is calculated. After the correction by the predetermined amount is reduced, the process proceeds to step 18. If the determination in step 14 is NO, the process proceeds to step 16 to determine whether or not the deviation Δα is smaller than a predetermined negative value. If the determination is YES, the process proceeds to step 17 and the purge control valve 30 After increasing the feedback correction value LPA of the control duty by a predetermined amount, the process proceeds to step 18. If the determination in step 16 is NO, the process directly proceeds to step 18.

In step 18, the final purge control valve 30
Control duty P _ADUTY of the set at a value obtained by adding to the base value P _A and the integral value IPA and the feedback correction value LPA. In step 19, a signal of the set control duty P _ADUTY is output to the purge control valve 30.

Next, at step 20, the fuel injection valve 15
The effective injection pulse width T _e of the reset is corrected by the following equation. T _e ′ = (Q _TE −Q _S ) / m Step 21 is an injection pulse having an injection pulse width T _I obtained by adding the voltage correction amount T _S as an invalid injection pulse to the effective injection pulse width T _e ′. A signal is output to the fuel injection valve 15.

Here, a fuel injection valve as a fuel supply means
The fuel supply amount from 15 to the total required fuel quantity Q _TE instead of subtracting the amount Q _PA corresponding to control duty P _A of the purge control valve 30, the amount based on the concentration detected by the concentration sensor 32 Q _S
Is subtracted because the detected value is a value that accurately reflects the actual inhalation amount. For example, if, as hardly storing evaporated fuel in the canister 29, Q _PA is a value which differs greatly from the intake amount of fuel vapor.

Next, an air-fuel ratio feedback correction coefficient setting routine will be described with reference to the flowchart of FIG. This routine is executed in synchronization with the engine rotation. This air-fuel ratio feedback correction coefficient setting routine corresponds to an air-fuel ratio feedback correction unit. In step 31, it is determined whether or not the operating condition is such that the air-fuel ratio feedback control is performed. If the operating conditions are not satisfied, this routine ends. In this case, the feedback correction coefficient α
Is clamped to the value at the end of the previous feedback control or a fixed reference value, and the feedback control is stopped.

In step 32, the signal voltage V _O2 from the air-fuel ratio sensor 19 is input. In step 33, the signal voltage V _O2 input in step 32 is compared with a reference value SL corresponding to a target air-fuel ratio (stoichiometric air-fuel ratio) to determine whether the air-fuel ratio is rich or lean. judge. When the air-fuel ratio is lean ( _VO2 <SL), the process proceeds to step 34, where it is determined whether or not the rich-to-lean inversion is performed (immediately after the inversion).
And the air-fuel ratio feedback correction coefficient α is updated with a value obtained by adding a predetermined proportional amount P _L to the current value. It is updated with the value obtained by adding the I _L.

On the other hand, if it is determined in step 33 that the air-fuel ratio is rich (V _O2 > SL), the routine proceeds to step 37, in which the lean->
It is determined whether the time of the rich inversion (after inversion) at the time of reversing the flow proceeds to step 38, updates the air-fuel ratio feedback correction coefficient α by a value obtained by subtracting from the current value of the predetermined proportional portion P _R, when inverted except updates with the air-fuel ratio feedback correction coefficient value obtained by subtracting from the current value of the predetermined integral portion I _L of α proceeds to step 39.

With this configuration, the set value can be obtained while appropriately setting the target amount of the evaporated fuel to be taken in based on the sharing ratio set based on the operating state, and detecting the concentration of the evaporated fuel. Thus, the feedback control of the evaporated fuel suction amount can be performed. Further, since the evaporated fuel intake amount is corrected based on the feedback correction amount in the air-fuel ratio feedback control, the air-fuel ratio feedback control with high responsiveness can be performed by adjusting the amount of evaporated fuel in the gas state.

Further, by reducing and correcting the fuel amount from the fuel supply means by an amount corresponding to the amount of the evaporated fuel, the mixture of the supplied fuel and the evaporated fuel can be set to an appropriate air-fuel ratio. . In the case where the air-fuel ratio is variably controlled according to the operating conditions, the air-fuel ratio of the fuel vapor in the intake manifold is estimated according to the detected value of the fuel vapor concentration, and the fuel supply is determined according to the difference from the target air-fuel ratio. A configuration in which the amount is corrected and controlled may be adopted.

[0033] Figure 7 shows the embodiment of the control, based on fuel vapor concentration Q _S read in step 41, estimated air-fuel ratio INTAF in the intake manifold at step 42, the engine in step 43 setting a target air-fuel ratio TGAF based on the rotational speed N and the load (basic fuel injection quantity T _P, etc.),
In step 44, the air-fuel ratio INTAF in these intake manifolds
And the fuel supply amount T _I is set by the following equation based on the target air-fuel ratio TGAF.

T _I = T _e × (TGAF−INTAF) / TGAF + T _S

[0035]

As has been described in the foregoing, according to the present invention
In the evaporative fuel control device for an internal combustion engine, fluctuations in the air-fuel ratio can be suppressed by controlling the amount of evaporative fuel sucked while detecting the concentration of the evaporative fuel. In addition, it is possible to control the amount of evaporated fuel suction while setting an appropriate share of the evaporated fuel according to the operating state.

Further, by correcting the evaporated fuel suction amount based on the feedback correction amount in the air-fuel ratio feedback control, the air-fuel ratio feedback control with high responsiveness can be performed by adjusting the amount of evaporated fuel in the gas state. In addition, an appropriate air-fuel ratio can be set by reducing and correcting the amount of fuel from the fuel supply unit by an amount corresponding to the amount of evaporated fuel sucked.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a system configuration according to an embodiment;

FIG. 3 shows a first part of the air-fuel ratio control routine of the embodiment .
The flowchart shown .

FIG. 4 is a flow chart showing a latter part.

FIG. 5 shows an air-fuel ratio feedback correction amount setting in the embodiment .
9 is a flowchart showing a routine.

FIG. 6 is a flowchart showing a second embodiment of the air-fuel ratio control .
G.

[Explanation of symbols]

 11 Engine 13 Air flow meter 15 Fuel injection valve 16 Control unit 19 Air-fuel ratio sensor 21 Crank angle sensor 22 Fuel tank 28 Evaporated fuel passage 29 Canister 30 Purge control valve 32 Concentration sensor

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 25/08 301 F02D 41/02 330 F02D 41/04 330 F02D 41/14 310

Claims (1)

(57) [Claims] An evaporator for an internal combustion engine that temporarily adsorbs and stores evaporative fuel on an adsorbing means and inhales the stored evaporative fuel into an intake system of the engine while controlling the amount of suction under predetermined engine operating conditions. a fuel control apparatus, the operating condition detecting means for detecting an operating condition of the engine, the operating state of the engine detected by said operating condition detecting means
Fuel supplied to the engine by the fuel supply means according to
The share between the fuel and the amount of evaporated fuel sucked into the intake system
Based on the sharing ratio set by the sharing ratio setting unit, the evaporated fuel concentration detecting unit for detecting the concentration of the evaporated fuel sucked into the intake system from the adsorption unit, and the sharing ratio set by the sharing ratio setting unit.
The evaporative fuel concentration detection means detects the set amount of evaporative fuel
The fuel vapor concentration is compared with the fuel vapor concentration detected by
When the fuel vapor concentration is high, the amount of fuel vapor
The first evaporative fuel that makes a correction to increase the amount of evaporative fuel
Detects charge correction means and the air-fuel ratio of the mixture of fuel and air supplied to the engine
Air-fuel ratio detecting means and the target air-fuel ratio detected by the air-fuel ratio detection means for
From the fuel supply means to the engine so that
Air-fuel that increases or decreases the charge using the feedback correction amount
Ratio feedback correction means, and the evaporative fuel amount based on the feedback correction amount.
A second evaporative fuel amount corrector for increasing / decreasing correction, and a first evaporative fuel amount corrector and a second evaporative fuel amount corrector.
Of the evaporative fuel sucked into the intake system
Evaporative fuel suction amount control means for controlling the amount of fuel injected, and the evaporative fuel concentration detected by the evaporative fuel concentration detection means
The amount of fuel supplied from the fuel supply means to the engine in accordance with
An evaporative fuel control device for an internal combustion engine, comprising: a fuel supply amount correcting means set to be correct .