JPH0612235Y2 - Air-fuel ratio controller for internal combustion engine - Google Patents

Description

The present invention relates to an air-fuel ratio control device for an internal combustion engine of an automobile or the like, and more specifically, to an air-fuel ratio that appropriately corrects the air-fuel ratio according to changes in the fuel vapor amount. Regarding the control device.

(Prior Art) Recently, the demand for automobile engines is increasing,
There is a tendency to achieve high levels of conflicting issues such as exhaust gas reduction, high output, and low fuel consumption. Air-fuel ratio feedback control is performed to meet these requirements. There is also an engine in which a canister for collecting fuel vapor is provided between the fuel tank and the intake passage of the engine in order to prevent evaporation loss due to the fuel vapor of the fuel tank.

As a conventional air-fuel ratio control device for an internal combustion engine of this type, there is, for example, one disclosed in Japanese Patent Laid-Open No. 58-131343. In this device, the air-fuel ratio is detected by an oxygen sensor provided in the exhaust pipe, and the fuel injection amount is operated based on the detection result to perform feedback control so that the air-fuel ratio becomes the target air-fuel ratio.

Further, the same control is used to correct air-fuel ratio fluctuations caused by changes in the amount of fuel vapor supplied from the canister to the intake passage. FIG. 6 is a timing chart of such air-fuel ratio control. In FIG. 6, the base M
The R correction coefficient K _BLRC is a coefficient for correcting the operating air-fuel ratio to the target air-fuel ratio, and K _BLRC is feedback-controlled based on the detection result of the oxygen sensor.

(Problems to be solved by the invention) However, in such a conventional air-fuel ratio control device for an internal combustion engine, correction of the air-fuel ratio variation accompanying a change in the amount of fuel vapor supplied from the canister during operation is also possible. Since the feedback control is performed by detecting the oxygen concentration in the exhaust gas, the control delay for a sudden change in the fuel vapor amount increases, the air-fuel ratio deviates significantly from the target air-fuel ratio, and the operability of the engine deteriorates. This has led to an increase in exhaust emissions. In particular, the problem becomes remarkable when refueling. Here, the behavior of the air-fuel ratio during refueling will be described with reference to FIG.

In FIG. 8, the canister state during refueling has largely changed from empty to saturated, and the fuel vapor amount at the time of engine start immediately after refueling is rapidly increased. Since the K _BLRC value for correcting the air-fuel ratio against such a sudden change in the fuel vapor gradually changes as shown by the solid line with respect to the target value (broken line), a control delay occurs in the shaded portion. Not only is feedback control performed based on the output of the oxygen sensor, but the K _BLRC value before refueling is stored in the memory in the control unit, and it is stored when the engine starts after refueling.
_This is because control is started from the _BLRC value. That is, the feedback control of the K _BLRC value _gradually becomes richer as the fuel amount decreases, and the target K _BLRC value (K _BLRC value for the rapid increase in the fuel vapor amount immediately after refueling is calculated.
There is a large deviation from the value <1).

Also, since the K _BLRC value is learned and corrected based on the output of the oxygen sensor, it cannot respond instantaneously to the air-fuel ratio that changes stepwise, and a control delay occurs in the shaded area, causing the air-fuel ratio to change. Becomes overrich.

(Purpose of the Invention) Therefore, the present invention detects the fuel amount in the fuel tank and adds a correction coefficient of the air-fuel ratio based on the change in the fuel amount to the calculation element of the fuel injection in advance, so that the fuel vapor amount changes according to the change in the fuel vapor amount. The purpose of the present invention is to improve the drivability of the engine and reduce the exhaust emission by correcting the fuel ratio fluctuation without control delay.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device for an internal combustion engine according to the present invention has a canister connected to an intake passage, and an engine for desorbing a vapor of the canister during operation,
Air-fuel ratio detection means a for detecting the air-fuel ratio of the intake air-fuel mixture
And a fuel amount detecting means b for detecting the amount of fuel in the fuel-fuel tank at the time of refueling and storing the increase amount of the fuel amount at the time of refueling, and the air-fuel ratio to the target air-fuel ratio based on the output of the air-fuel ratio detecting means. First computing means c for computing the first air-fuel ratio correction coefficient to be corrected
And estimating the fuel vapor adsorption state of the canister based on the increase amount of the fuel amount during refueling stored in the fuel amount detection means,
Second calculating means d for calculating a second air-fuel ratio correction coefficient for correcting the air-fuel ratio according to the vapor concentration in the canister,
Control means e that calculates a control value that controls the fuel injection amount or the intake air flow rate so that the air-fuel ratio becomes the target air-fuel ratio based on the outputs of the first calculation means and the second calculation means, and the output of the control means And an operating means f for operating the injection amount of fuel or the flow rate of intake air based on the above.

(Operation) In the present invention, the fuel amount in the fuel tank is detected, and the correction coefficient of the air-fuel ratio based on the change of the fuel amount is added to the calculation element of the fuel injection in advance so that the change of the air-fuel ratio with the change of the fuel vapor amount is detected. The correction is performed without control delay, and the air-fuel ratio during operation is always corrected optimally.

Therefore, the drivability of the engine is improved and the exhaust emission is reduced.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 7 are views showing an embodiment of an air-fuel ratio control system for an internal combustion engine according to the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an engine, and the engine 1 has at least an injector (operating means) 2 and an oxygen sensor (air-fuel ratio detecting means) 3.

The injector 2 injects fuel based on the injection signal Si from the control unit 4. The oxygen sensor 3 detects the oxygen concentration in the exhaust gas of the engine 1 and outputs the detection signal S _O to the control unit 4. In the control unit 4, a fuel level sensor (fuel amount detecting means) 6 mounted in the fuel tank 5 and a switch 7 mounted in the fuel filler port (5a) are used to control the fuel amount signal S _F and the fuel gun 8 insertion signal, respectively. S _G has been entered. The control unit 4 performs an air-fuel ratio correction calculation based on the signals S _O , S _F , and S _G , and outputs an injection signal Si to control the amount of fuel injected from the injector 2. That is, the control unit 4 has a function as a first calculation means, a second calculation means, and a control means.

Further, a key signal _SK is inputted to the control unit 4 from an ignition key 9, and the ignition key 9 is switched to OFF, ON and Start positions. The canister 10 is a canister for collecting refueling vapor, and the canister 10 communicates with the fuel tank 5 via a pipe 11 and also with an intake passage of the engine 1 via a vapor purge line 12.

Incidentally, 13 is cut valve, 14 is a control valve, the cut valve 13 is opened and closed by an output signal S _G of the switch 7, the control valve 14 canister 10
The amount of fuel vapor supplied to the engine 1 from is adjusted.
In addition to the canister 10, there is provided a well-known canister (not shown) that also collects fuel vapor generated at the time of refueling. It should be noted that the single canister 10 may collect fuel vapor generated not only during refueling but also during refueling.

Further, the control valve may be configured as a duty valve so as to respond to the intake negative pressure, or the engine speed and the intake air amount (in a fuel injection engine, the basic fuel injection amount obtained from the intake air amount and the engine speed may be used. ) And the duty ratio obtained from the engine water temperature.

Next, the operation will be described.

FIG. 3 is a flow chart showing a program for air-fuel ratio control, and this program is for correcting the air-fuel ratio when the engine is restarted after the engine is stopped according to the fuel amount. First, at P ₁ , it is confirmed that the ignition key 9 is ON (represented by _SK = ON), and at P ₂ , the amount of fuel remaining in the fuel tank 5 immediately before the ignition key 9 is turned ON is controlled as a fuel amount signal F _1. Look up from a memory or the like stored in the unit 4. That is, P
Reference numeral ₂ is a step of looking up the fuel amount immediately before refueling in the region in the timing chart of the present embodiment shown in FIG. F ₁ is the IN signal (S _G = S _G =) of the switch 7 which is output when the fuel gun 8 is inserted as shown in FIG.
IN) is stored in advance in the memory in the control unit 4.

Since the canister state is gradually changing in the region, the air fuel consumption is almost feedback-corrected by the base MR correction coefficient K _BLRC (first air-fuel ratio correction coefficient). The K _BLRC value in this region is calculated based on the detection output S _O of the oxygen sensor 3.

Next, at P ₃ , the fuel amount signal F ₂ detected by the fuel level sensor 6 for the fuel amount in the fuel tank 5 immediately after the ignition key 9 is turned on is read. In P ₃ has detected the amount of fuel during fueling the end of the region of FIG. 4 (in oil), F ₂
Is stored in the control unit 4 in advance by the OUT signal (S _G = OUT) of the switch 7 which is output when the fuel gun 8 is pulled out as shown in FIG.

Then, calculates the _F 2 -F ₁ at _{P 4,} the correlation between the K _OMBEVP value and fuel quantity indicating when lubricating base MR correction coefficient K _OMBEVP the (second air-fuel ratio correction coefficient) in Figure 6 at _{P 5} The calculation is performed based on the diagram shown in FIG.

That is, the _KOMBEVP value is calculated and stored in advance before the engine is started so that the air-fuel ratio deviated by the fuel vapor supplied from the canister 10 to the engine 1 becomes the target air-fuel ratio. In this embodiment, the fuel vapor adsorption state of the canister 10 is estimated by detecting the fuel amount in the fuel tank 5, and the K _OMBEVP value is set based on this fuel amount as shown in FIG. There is.

Next, at P ₆ , the ignition key 9 is turned on to start
It is determined whether or not it has been switched to t (S _K = Start). If it has not been switched, the process returns. If it has been switched, the process proceeds to P ₇ . At P ₇ , the normal injection amount (driving pulse width) Ti of the injector 2 is calculated by the following equation.

Ti = Tp × COEF × (α + K _BLRC ) × K _OMBEVP + Ts, where Tp: basic injection amount COEF: various correction coefficients α: air-fuel ratio feedback correction coefficient Ts: voltage correction coefficient That is, in P ₇ , K _BLRC to K _OMBEVP By multiplying by the value, the K _BLRC value at engine start immediately after refueling is optimally corrected. Then, the injection signal Si based on the Ti from the control unit 4 at P ₈ is output to the injector 2, the fuel from the injector is injected into the engine 1.

By executing the steps P _{1 to} P ₅ before the engine starts as described above, the K _BLRC value immediately after the engine starts is corrected to the target K _BLRC without a time delay as shown in FIG. The air-fuel ratio is optimally controlled even when the state suddenly changes from air to saturation. As a result, the overrich region (hatched portion) due to the control delay is avoided.

Therefore, in this embodiment, paying attention to the mutual relationship between the fuel vapor adsorption state in the canister 10 and the fuel amount in the fuel tank 5, unlike the prior art, only the feedback correction of the air-fuel ratio based on the oxygen concentration in the exhaust gas is performed. Instead, the air-fuel ratio correction coefficient K _OMBEVP value based on the fuel amount is calculated in advance in the time from the engine stop to the engine restart, and it is used as the calculation element of the fuel injection amount immediately after the engine starts, so that the fuel vapor amount changes suddenly It is possible to control to the target air-fuel ratio without a time-dependent control delay with respect to the change in the air-fuel ratio due to

That is, the air-fuel ratio is optimally corrected for a sudden change in the fuel vapor amount immediately after refueling, and the overrich region is reliably avoided.

As shown in FIG. 7, the K _OMBEVP value is set according to the atmospheric temperature T and the atmospheric pressure P, and is calculated from the detected atmospheric temperature (T ₁ , T ₂ ) and atmospheric pressure (A ₁ , A ₂ ). You may do it. In this case, the air-fuel ratio correction based on the _KOMBEVP value becomes more accurate.

In this way, the air-fuel ratio of the engine 1 is always controlled optimally with no time delay, so that the drivability of the engine 1 is improved and the exhaust emission can be reduced. (Effect) According to the present invention, the fuel amount in the fuel tank is detected, and the air-fuel ratio correction coefficient based on the change in the fuel amount is added to the calculation element of the fuel injection in advance. Fluctuations can be corrected without control delay, and the air-fuel ratio during operation can be constantly and optimally corrected.

As a result, it is possible to improve the drivability of the engine and reduce exhaust emissions.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 5 are diagrams showing an air-fuel ratio control device for an internal combustion engine according to the present invention, FIG. 2 is its overall configuration diagram, and FIG. 3 is its air-fuel ratio. 4 is a flow chart showing a control program, FIG. 4 is a timing chart for explaining the operation, FIG. 5 is a timing chart showing the relationship between the fuel gun and fuel, and FIG. 6 is the second air-fuel ratio correction coefficient. Graph showing correlation of fuel amount, No. 7
FIG. 8 is a graph in which elements of atmospheric temperature and atmospheric pressure are added to FIG. 6, and FIG. 8 is a timing chart for explaining the operation of the conventional air-fuel ratio control device for an internal combustion engine. 1 ... Engine, 2 ... Injector (operating means), 3 ... Oxygen sensor (air-fuel ratio detecting means), 4 ... Control unit (first computing means, second computing means, control means), 6 ... Fuel Level sensor (fuel amount detection means).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area F02M 25/08 301 J 7114-3G

Claims (1)

[Scope of utility model registration request] 1. An a-fuel ratio detecting means for detecting an air-fuel ratio of an intake air-fuel mixture of an engine having a canister connected to an intake passage and performing vapor desorption of the canister during operation, and b) refueling. Fuel amount detection means for detecting the fuel amount in the fuel tank at the time of refueling and storing the increased amount of the fuel amount at the time of refueling; A first calculating means for calculating an air-fuel ratio correction coefficient of 1; and d) estimating the fuel vapor adsorption state of the canister based on the amount of increase in the fuel amount during refueling stored in the fuel amount detecting means,
Second calculating means for calculating a second air-fuel ratio correction coefficient for correcting the air-fuel ratio according to the vapor concentration in the canister; and e) the target air-fuel ratio based on the outputs of the first calculating means and the second calculating means. Control means for calculating a control value for controlling the fuel injection amount or the intake air flow rate such that: f) an operating means for operating the fuel injection amount or the intake air flow rate based on the output of the control means, An air-fuel ratio control device for an internal combustion engine, comprising: