JPS6357841A - Air-fuel ratio controller for engine - Google Patents

Abstract

PURPOSE:To make the convergence of an air-fuel ratio onto the desired air-fuel ratio performable in a short time, by compensating a fundamental control variable at the point that a feedback compensation value exceeds the setting value when evaporated fuel is purged during feedback control over the air-fuel ratio. CONSTITUTION:According to the fundamental controlled variable found on the basis of output of a driving state detecting device 65, fuel is metered by a fuel metering device 79, while an air-fuel ratio of mixture is feedback- controlled to the desired value by an air-fuel ratio controlling device 80 according to the compensation value conformed to output of an air-fuel ratio sensor 54. In a suchlike device, there is provided with a purge controlling device 82 which controls a purge device 35 purging evaporated fuel to a suction system of an engine 1 according to an engine driving state. And, at a time when a detecting device 84 detects purge time of the evaporated fuel, when the compensation value of feedback control by the air-fuel ratio controlling device 80 exceeds the setting value, there is also provided with a fundamental controlled variable compensating device 85 compensating the fundamental controlled variable of the fuel metering device 79.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an air-fuel ratio control device for an engine, and in particular, measures to improve the controllability of the air-fuel ratio during purging to supply evaporated fuel from a fuel tank or the like to the engine. Regarding.

(Prior Art) Conventionally, in order to prevent black light fuel generated in fuel tanks etc. from dispersing into the atmosphere, for example, Japanese Patent Laid-Open No. 59-192858
As determined in the above publication, vaporized fuel is adsorbed into an adsorption device such as a canister, and the adsorbed evaporated fuel is supplied to the intake system of the engine depending on the operating state of the engine.

(Problems to be Solved by the Invention) However, when the above-described purge of vaporized fuel is applied to an engine that controls the air-fuel ratio of the air-fuel mixture, the following drawbacks occur. In other words, in air-fuel ratio control of the mixture,
The air-fuel ratio sensor detects the air-fuel ratio of the air-fuel mixture supplied to the engine, and the air-fuel ratio of the air-fuel mixture supplied to the engine is feedback-controlled to a target value by a correction amount according to the output of the air-fuel ratio sensor. The magnitude of the correction amount for this air-fuel ratio feedback control is usually set within a predetermined range in order to prevent incorrect air-fuel ratio control caused by noise entering the output signal of the air-fuel ratio sensor. It is limited within. For this reason, during feedback control of the air-fuel ratio, especially when purging of evaporated fuel is performed at a low intake air amount, the air-fuel ratio fluctuates greatly due to this purging of evaporated fuel, which tends to cause lynch. As a result, the feedback correction amount of the air-fuel ratio control increases toward the lean side, and is limited to the maximum value within the setting range, which is greatly different from the correction amount value corresponding to the target air-fuel ratio. The disadvantage is that the air-fuel ratio is not controlled to the target air-fuel ratio, resulting in poor controllability.

Therefore, various solutions are being considered, but even in that case, when the purge of vaporized fuel is completed and only feedback control of the air-fuel ratio is returned to, the air-fuel ratio should immediately converge to the target value. It is necessary to be able to perform air-fuel ratio control with good responsiveness.

This light was developed in view of the above, and its purpose is to prevent the correction amount of air-fuel ratio control from exceeding a predetermined value when purge of evaporated fuel is performed simultaneously during air-fuel ratio feedback control. At times, by changing the basic control jI]ffl determined according to the engine operating state, for example, the basic fuel injection amount in a fuel injection type engine, to a value different from that during non-purging, even when purging evaporated fuel,
The overall air-fuel ratio, including the basic control amount and feedback control correction amount, can be converged to the target air-fuel ratio, and at the end of the subsequent purge, the feedback correction amount can be adjusted from around its reference value. The air-fuel ratio can be controlled to converge to the target air-fuel ratio within a small adjustment range.
The purpose is to improve the responsiveness of air-fuel ratio control.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention, as shown in FIG. A fuel metering device 79 receives the output of the device 65 and adjusts the amount of fuel supplied to the engine 1 based on a basic control 6111 depending on the engine operating state, and an air-fuel ratio of the air-fuel mixture supplied to the engine 1. an air-fuel ratio sensor 54 that detects the air-fuel ratio; and an air-fuel ratio control means 8 that feedback-controls the air-fuel ratio of the air-fuel mixture supplied to the engine 1 to a target value with a correction amount according to the output of the air-fuel ratio sensor 54.
Air/fuel pressure control of an engine with o and t! ! 1 device is assumed. Then, in response to the outputs of the purge means 35 for purging the evaporated fuel into the intake system of the engine 1 and the operating state detection means 65, the purge means 35 is controlled to purge the evaporated fuel into the engine 1 according to the engine operating state. The air-fuel ratio control means 80 receives the output of the purge time detection means 84 and detects when the vaporized natural material is purged. When the correction amount controlled by feedback 1IilJ exceeds the set value, the fuel metering means 79
The basic control amount correction means 85 corrects the basic control amount.

(Function) With the above configuration, in the present invention, when only the feedback control of the air-fuel ratio of the air-fuel mixture is performed, the amount of fuel supplied to the engine 1 is controlled by the fuel metering means 79 by the basic control. The air-fuel ratio of the air-fuel mixture supplied to the engine is detected by the air-fuel ratio sensor 54 while being adjusted to a predetermined amount according to the operating condition, and a feedback correction amount is calculated according to the output of the air-fuel ratio sensor 54. The basic control Offi is feedback-controlled in accordance with this feedback correction amount, and the air-fuel ratio of the air-fuel mixture supplied to the engine is adjusted to the target air-fuel ratio by the air-fuel ratio control means 80.

In addition, during feedback control of the air-fuel ratio as described above, if purging of vaporized fuel is simultaneously performed depending on the operating state of the engine 1, the air-fuel ratio becomes rich due to this purge, and the target air-fuel ratio In this case, basic control of the fuel metering means 79] f
Since fi is corrected to the lean side by the basic 11i1J111 suspension correction means 85, the air-fuel ratio is quickly controlled to the target air-fuel ratio while the feedback correction amount is maintained near the reference value.

When the purge of evaporated fuel is completed and the air-fuel ratio feedback control is returned to, the value of the basic control p is returned to the original value, and the basic control i is successively corrected by the feedback correction amount. The fuel ratio converges to the target air-fuel ratio. At that time, since the feedback correction amount is near the reference value,
Even when the air-fuel ratio changes due to subsequent disturbances, the range of successive changes in the feedback correction amount is as small as possible, and as a result, the air-fuel ratio converges to the target air-fuel ratio as quickly as possible. Become.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

Figure 2 shows the overall configuration of the air-fuel ratio control device for a fuel injection engine, where 1 is the engine, and 2 is the cylinder 3 of the engine 1.
A combustion chamber 5 is formed with a variable volume by a piston 4 slidably inserted into the combustion chamber 5. One end of the combustion chamber 5 communicates with the atmosphere via an air cleaner 6, and the other end opens into the combustion chamber 2 to supply intake air to the engine 1. An intake passage 7 for supplying air is an exhaust passage whose one end opens into the combustion chamber 2 and whose other end is open to the atmosphere to discharge exhaust air. A throttle valve 8 for controlling the amount of fuel and a fuel injection valve 9 for injecting and supplying fuel to the vicinity of the combustion chamber 2 on the downstream side of the throttle valve 8 are respectively disposed, while in the middle of the exhaust passage 7, A catalyst device 10 for purifying exhaust gas is provided.

Reference numeral 15 denotes a fuel tank, and the fuel inside the fuel tank 15 is supplied through a fuel pump 16 and a fuel filter 17 disposed inside the fuel tank 15, and a fuel supply passage 19 through which another fuel filter 18 is interposed. The fuel in the fuel tank 15 can be injected into the intake passage 5 from the fuel injection valve 9.

Further, a pressure regulator 21 for regulating fuel pressure is connected to the fuel supply passage 19 of the fuel injection valve 9 through a pressure regulation passage 20 communicating with the fuel injection valve 9. The fuel is returned to the fuel tank 15 via the fuel return passage 22, and the pressure of the fuel supplied to the fuel injection valve 11 is adjusted to a set value.

Furthermore, a canister 27 containing activated carbon that adsorbs evaporated fuel is connected to the inside of the fuel tank 15 through an evaporated fuel distribution passage 26 in which a one-way valve 25 is interposed. The inside of the canister 27 is connected to an evaporated fuel supply passage 28.
The purge control valve 29 is connected to the downstream side of the throttle valve 8 of the intake passage 5 through the intake passage 5 and opens and closes according to the action of atmospheric pressure and negative pressure. A three-way valve 32 is connected through the passage 30, and the three-way valve 32 allows purge air to be introduced into the oil M.
30ffi When negative pressure is introduced into the intake passage 5 downstream of the throttle valve 8 through the negative pressure introduction passage 33, the purge control valve 29 is closed to stop purging of evaporated fuel, while the three-way valve 32 When the bar share introduction passage 30 is communicated with the atmosphere, the two purge control valves are opened by the atmosphere (purge air), and then the evaporative fuel in the canister 27 is transferred to the evaporative fuel supply 3 [! ! A purge means 35 is configured to purge the intake passage 5 downstream of the throttle valve 8 via the passage 28.

Further, a first orifice 37 for restricting purging of the vaporized fuel is interposed in the middle of the vaporized fuel supply passage 28, and a bypass passage 38 is provided before and after the first orifice 37, and the bypass passage 3. 8, there is a second orifice 39 with a larger diameter than the first orifice 37.
and an on-off valve 40 that opens and closes the bypass passage 38. A three-way valve 41 for controlling the opening and closing of the on-off valve 40 is connected to the three-way valve 41, and the three-way valve 41 opens and closes atmospheric pressure. When the valve 40 is actuated, the on-off valve 40 is closed and the vaporized fuel is purged through the first orifice 37 without bypassing, thereby obtaining a predetermined purge speed, while the three-way valve 41 closes the on-off valve 40 and purges the vaporized fuel through the first orifice 37. When the negative pressure on the downstream side of the throttle valve 8 of No. 5 is applied to the opening/closing valve 40, the opening/closing valve 4
0 is opened and vaporized fuel is purged into the engine 1 through the second orifice 39 of the bypass passage 38, the purge speed is made faster than the predetermined speed, and the purge speed can be switched to two stages. There is.

In addition, 50 is an air flow sensor that detects the amount of intake air on the upstream side of the throttle valve 8 in the intake passage 5, 51 is an opening sensor that detects the opening of the throttle valve 8, and 52 is a rotation speed sensor that detects the engine speed. 53 is a cooling water temperature sensor that detects the engine cooling water temperature; 54 is disposed in the exhaust passage 7 and detects the air-fuel ratio of the air-fuel mixture supplied to the engine based on the M water concentration component in the exhaust gas. An air-fuel ratio sensor, 55 is a start switch operated by the driver, 56 is an idle switch that detects when the engine 1 is idling based on the opening degree of the throttle valve 8, 57 is a neutral switch that detects the neutral position of the transmission, 58 59 is a cooler switch that detects when the in-vehicle cooler is activated; 60 is a power steering switch that detects when the power steering device is activated; 61 is an electric load. 62 is a power switch that detects high load based on the opening degree of the throttle valve 8. 63 is a power switch that detects when the engine coolant temperature is above a predetermined temperature (for example, 5o'c>JX). The air 70-sensor 50 and distributor 52 constitute an operating state detection means 65 that detects the operating state of the engine 1.The sensors and switches 50 to 63 are water temperature switches.
The detection signals of the controllers 70 each have a built-in CPU, etc.
The control 0-770 controls the operation of the fuel injection valve 9 and the two three-way valves 32 and 41, respectively. In addition, in the figure, 75 directs the blow-by gas to the intake passage 5.
The PCV valve 76, which returns the downstream side of the throttle valve 8, is installed in the middle of the bypass passage 77 that bypasses the throttle valve 8 in the intake passage 5, and is an idle adjustment valve that adjusts the idle speed of the engine by adjusting the amount of bypass intake air. It's a valve.

Then, the controller 70 receives the outputs of the air 70-sensor 50 and the distributor 52 (operating state detection means 65), and determines the basic fuel injection amount τ according to the operating state of the engine 1. is successively calculated from a pre-stored fuel injection amount map corresponding to the engine operating state, and this read basic fuel injection amount τ is obtained. It has a function as a filling metering means 79 that adjusts the amount of fuel supplied to the engine 1 by controlling the operation of the fuel injection valve 9 so that the fuel is injected from the fuel injection valve 9.

The controller 70 also controls the air-fuel ratio sensor 54.
The detection signal (air-fuel ratio signal) is received, the air-fuel ratio signal value is compared in magnitude with the target air-fuel ratio, and the feedback correction ff1cFs (reference value - 〇) is changed by a small increase or decrease according to the magnitude. The fuel injection amount τ from the fuel injection valve 9 is set as the basic fuel injection amount τ using the feedback correction amount CFa. Based on the following formula (% formula %) C^; Correction coefficient when purging vaporized fuel (described later), the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is feedback-controlled to the target air-fuel ratio by increasing or decreasing it. The air-fuel ratio control means 80 is configured as follows. Further, the controller 70 has the following functions in order to prevent erroneous control of the air-fuel ratio:
The upper and lower limits of the magnitude of the feedback correction ff1cFs are within the setting range of +25% (±0°25) (-25%≦C
If the feedback correction amount c゛FB exceeds this set range, the value is set to the upper limit (+25%) or lower limit (-2) within the set range.
5%).

Further, during the feedback control, the controller 70 receives detection signals from the air flow sensor 50, the distributor 52, the coolant temperature sensor 53, the neutral switch 57, and the clutch switch 58, and controls the engine 1 based on these detection signals. When it is determined that the engine is operating under load and the engine cooling water temperature is 506C or higher, the three-way purge valve 32 is switched and controlled so as to introduce atmospheric air into the purge air introduction passage 30, and the vaporized fuel is used for engine operation. A purge control means 82 is configured to purge the intake system of the engine 1 depending on the state.

Next, the basic control amount of the feedback control by the controller 70, that is, the change control of the fuel injection amount from the fuel injection valve 9 will be explained based on the flowchart of FIG. After starting, in step S1, it is determined whether the air-fuel ratio is being controlled by feedback control, and in step S2, it is determined whether or not the evaporated fuel is being purged. In Case of,
In step S3, the magnitude of the feedback correction ff1cFs is set to one side - X% (lx%l <l 25%;)
If CF8 exceeds -X% and is larger than -X% (YES), it is determined that the air-fuel ratio has become rich due to vaporized fuel purge, and correction is made in step S4. By subtracting the coefficient CA by a predetermined value from the reference value P○'', the basic fuel injection amount is reduced by a predetermined amount, and the value of the feedback control afJcFs is reduced to "'O".
The value is returned to the original value and the process proceeds to step S6.

And, like this, the basic fuel injection amount τ. After reducing the amount, the feedback correction ff1cFa has a value of "0", so the determination in step S3 is N.

In step S5, the feedback correction amount CFEI is changed in order to grasp the situation in which the feedback correction amount CF e increases as the amount of vaporized fuel purge decreases over time. Determine whether or not the predetermined value X% (X% <25%) on the + side has been exceeded, and CF
, in the case of No, B≦+X%, the basic fuel injection amount τ. While reducing the amount, the feedback correction ff is performed in step S6.
Control the air-fuel ratio of the mixture to the target air-fuel ratio with 1 cFe σp
On the other hand: The feedback correction amount CFB is set to its setting value (
CF exceeding +X%), if >+X% YES,
It is determined that the deviation of the air-fuel ratio from the target air-fuel ratio has become large, and in step S7 the correction coefficient CA is adjusted to
Return to the On value and set the basic fuel injection amount τ.

After returning to the original value, the process proceeds to step S6, where the air-fuel ratio of the air-fuel mixture is controlled to the target air-fuel ratio using the feedback correction mcFa.

Then, in the case of NO in which the purge of vaporized fuel has been completed in step S2, or in the case of NO in which feedback control of the air-fuel ratio is no longer performed due to a change in the engine operating state in step S1, the next feedback control is performed in step S8. In preparation for control, the current feedback correction fJ
The value of cFe is canceled and returned to the reference value "0", and the process ends.

Therefore, in the flow shown in FIG. 2, from step S2, the purge time detection means 8 detects the time when the M source fuel is purged.
In addition, in step S*, 84, the output of the purge detection means 84 is received, and the magnitude of the feedback correction ff1cF day by the air-fuel ratio control means 80 is determined by the air-fuel ratio when purging the vaporized fuel. When the set value (-X%) is exceeded due to a shift to the rich side,
Basic control 11 correction means 85 which sets the correction coefficient CA to a negative value and corrects the basic charge tIl (basic fuel injection amount τ) of the fuel metering means 79 by a predetermined amount.
It consists of

Therefore, in the embodiment described above, the basic fuel injection amount τ of the fuel metering means 79 initially corresponds to the engine operating state.

When the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is detected by the air-fuel ratio sensor 54, the feedback correction ff1cFe is changed in size based on the air-fuel ratio signal, and the fuel injection valve is adjusted according to the feedback correction ff1cFa. The fuel injection amount τ from 9 is adjusted to increase or decrease, and the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is feedback-controlled to the target air-fuel ratio.

Further, during the feedback control described above, in a specific engine operating state (that is, a state where the engine cooling water temperature is 50'C or higher under load), the purge means 35 is operated and controlled by the purge control means 82, and the inside of the canister 27 is controlled. The evaporated fuel is supplied to the intake passage 5 via the evaporated fuel supply passage 28.
The evaporated fuel is purged downstream of the throttle valve 8 to prevent the evaporated fuel from diffusing into the atmosphere.

In this case, especially when the intake air amount is low, the effect of purging the vaporized fuel on the air-fuel ratio is large, and the air-fuel ratio fluctuates greatly toward the rich side, but at this time, the feedback correction amount CFB
When the amount of fuel increases to the set value (-X%), the basic fuel injection amount τ. (Basic 11i17 ?nn Since the basic control amount correction means 85 makes a reduction adjustment using the correction coefficient CA, the air-fuel ratio quickly approaches the target air-fuel ratio, and then feedback control is performed by changing the size of the feedback correction ff1cFs, with high accuracy. The air-fuel ratio converges to the target air-fuel ratio.In this case, the air-fuel ratio approaches the target value by adjusting the reduction ffi of the basic fuel injection amount using the correction coefficient C^, so the feedback correction ff1cFe is )
As shown in , when the fuel injection amount τ is reduced to reach the -Wata setting value (-X%), it is returned to the standard value of "0" and then increases and decreases around this "'○" value. , the air-fuel ratio converges to the target value. Thereafter, as shown in the figure (b), the feedback correction amount GFB increases to the + side as the purge amount of vaporized fuel decreases and reaches a predetermined value (+X%), when the correction coefficient CA becomes smaller than the reference value. The basic fuel injection amount τ returns to the 0″ value.

As the amount increases, the air-fuel ratio decreases again and changes up and down near the '0 value, and the air-fuel ratio converges to the target air-fuel ratio.

As a result, when the purge of evaporated fuel is completed, the feedback correction ff1cFs is near the 0 value, and even if the situation changes only to feedback control of the air-fuel ratio, the air-fuel ratio is feedback-controlled to the target air-fuel ratio in a short time. Therefore, when purging evaporated fuel, the air-fuel ratio can be well controlled to the target air-fuel ratio, and even after this purge is finished, the air-fuel ratio can be brought to the target air-fuel ratio in a short time without causing any deviation in the air-fuel ratio. Good convergence can be achieved, and the controllability of the air-fuel ratio can be improved.

In the above embodiment, the present invention is applied to an engine equipped with a fuel injection valve 9, but it goes without saying that the present invention can be similarly applied to an engine equipped with a carburetor.

(Effects of the Invention) As explained above, according to the present invention, when purge of vaporized fuel is performed simultaneously during feedback control of the air-fuel ratio, when the feedback correction amount exceeds the set value, the engine operation is started. Since the basic control I suspension is corrected according to the state and the air-fuel ratio is controlled to the target air-fuel ratio within a small feedback correction amount range, the air-fuel ratio can be well controlled to the target value when purging evaporated fuel, and Even when the air-fuel ratio shifts from the purge to the non-purge region and only feedback control of the air-fuel ratio is performed, the air-fuel ratio can be satisfactorily converged to the target air-fuel ratio in a short time without causing any deviation in the air-fuel ratio.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the composition of the present invention. Figures 2 to 4 show embodiments of this light, Figure 2 is an overall configuration diagram, Figure 3 is a flowchart diagram showing the operation of the controller, and Figures 4 (a) and (b) are operation explanatory diagrams. It is. 7... Exhaust passage, 9... Fuel injection valve, 15... Fuel tank, 27... Canister, 28... Evaporated fuel supply passage, 29... Purge control valve, 30... Purge air Introduction passage, 32... Three-way valve, 35... Purge means, 54... Air-fuel ratio sensor, 63... Water temperature switch, 65... Operating state detection means, 70... Controller, 79... - Fuel metering means, 80... Air-fuel ratio control means, 82... Purge control means, 83... Feedback control detection means, 84... Purge detection means, 8
5...Basic control amount correction means.

Claims (1)

[Claims] (1) Operating state detecting means for detecting the operating state of the engine, and fuel for receiving the output of the operating state detecting means and metering the fuel to be supplied to the engine based on a basic control amount according to the engine operating state. a metering means, an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture supplied to the engine, and feedback of the air-fuel ratio of the air-fuel mixture supplied to the engine to a target value with a correction amount according to the output of the air-fuel ratio sensor. and purge means for purging the evaporated fuel into the intake system of the engine, and receiving the output of the operating state detection means to purge the evaporated fuel to the intake system of the engine according to the engine operating state. a purge control means for controlling the purge means so as to purge the fuel vapor; a purge time detection means for detecting when the evaporated fuel is purged; and a purge time detection means that receives the output of the purge time detection means and provides feedback by the air-fuel ratio control means when the evaporated fuel is purged. An air-fuel ratio control device for an engine, comprising basic control amount correction means for correcting the basic control amount of the fuel metering means when the control correction amount exceeds a set value.