JPH0425423B2 - - Google Patents

Description

[Detailed description of the invention] Technical field The present invention relates to an air-fuel ratio control device for an internal combustion engine.

The device according to the invention is used in a motor vehicle engine equipped with an electronically controlled fuel injection system.

BACKGROUND OF THE INVENTION One type of air-fuel ratio control device for an engine is known in the art. This type of device includes means for generating a basic fuel signal representative of the fuel demand of the engine at steady state in response to the values of predetermined engine operating parameters, including engine temperature, representative of the fuel demand of the engine; means for detecting transient engine operating conditions indicative of demand;
responsive to the measured value of engine temperature and the detected transient engine operating condition, the first value being equal to the first value determined by the engine temperature and determined by the detected transient engine condition; means for generating a reinforcement boost signal having an initial value of 1 and increasing by a factor that varies toward unity at a rate determined by the temperature of the engine; and means for supplying fuel to the engine, thereby supplying fuel to the engine on demand during both steady state and transient conditions of the engine. This device provides a fuel supply system that always ensures an optimum air-fuel ratio not only in the steady state of the engine but also in the transient state, thereby obtaining the optimum operation of the engine (see, for example, Japanese Patent Laid-Open No. 56-6034).

In the above-mentioned type of equipment, changes in engine characteristics over time, such as changes in valve clearance and EFI due to deposits adhering to the injector nozzle, deposits adhering to the back of the cylinder intake valve, etc. (lubricating oil components and combustion products) It does not take into account changes in characteristics due to changes in characteristics caused by sticky substances such as carbon particles derived from carbon particles, etc., and changes in volatility due to variations in gasoline properties. Since there is no means to detect changes in the air-fuel ratio from the optimum value, drivers may experience sluggishness during acceleration due to the use of low-volatility gasoline or dilution of the gas mixture during acceleration due to changes in the engine over time. There was a problem in that there was a possibility that the stability would deteriorate, or conversely, if gasoline with good volatility was used, the mixed gas would become rich during acceleration, resulting in deterioration in fuel efficiency and deterioration in emissions.

FIG. 1 illustrates the fluctuations in the air-fuel ratio in this case, particularly when deposits are attached to the back surface of the intake valve. In Figure 1, A/F(O)
A/F (DEP) represents the change in the air-fuel ratio before the deposit is deposited, and A/F (DEP) represents the change in the air-fuel ratio after the deposit is deposited. ACC determines the acceleration point, A/F (OPT) determines the optimum air-fuel ratio, A/F (LN) determines the lean side,
A/F (RCH) represents the rich side.

In addition, clogging of the injector can be corrected by feedback from the air-fuel ratio sensor during normal operation, but the same problem occurs during acceleration because there is no correction means. Also, the engine
Similar problems have also occurred due to variations in the manufacturing process of air flow meters and changes over time.

FIG. 2 illustrates the fluctuations when the gasoline properties are changed, and the same problem as in the case of deposits in FIG. 1 occurred. Gasoline is generally commercially available from the same manufacturer with different characteristics, such as one for summer and one for winter. Reed vapor pressure and distillation properties are generally well-known numerical values that indicate the volatility of gasoline, but when we looked at gasoline from one manufacturer throughout the year, the Reid vapor pressure was 0.5 Kg/cm ² to 0.86 Kg/cm. ² , and the temperature during 10% distillation also varies from 40 to 58°C, and changes in volatility due to differences in gasoline properties cause air-fuel ratio fluctuations as shown in Figure 2. In FIG. 2, G(S) represents the case of summer gasoline, and G(W) represents the case of winter gasoline. Although FIG. 2 shows an example of a change to the lean side, it may also change to the rich side.

OBJECT OF THE INVENTION One object of the present invention is to measure the difference between the correction amount determining factor amount corresponding to the intake condition such as the amount of income air per revolution, the negative pressure in the intake pipe, the slot opening degree, etc. and its smoothed value at a predetermined interval. A transient correction pattern in which the attenuation rate gradually decreases is formed by
The objective is to perform air-fuel ratio control that performs optimal correction without lean spikes.

Another object of the present invention is to detect rich/lean spikes with high sensitivity when transient conditions change due to changes over time, etc. by performing air-fuel ratio control that performs this optimal correction, to quickly learn, and to The objective is to improve the controllability of the temporal air-fuel ratio.

Configuration of the Invention In the present invention, a transient state of an internal combustion engine is detected;
When a transient state is detected, a transient fuel correction amount is determined at predetermined intervals according to the transient state, and the internal combustion engine air conditioner corrects the amount of fuel supplied to the internal combustion engine based on the transient fuel correction amount. In the fuel ratio control method, an air-fuel ratio deviation from an optimum air-fuel ratio during a transient period of the internal combustion engine is detected using the output of an air-fuel ratio sensor, and the transient air-fuel ratio is determined based on the ratio of the air-fuel ratio deviation to an amount of change equivalent to the intake air amount. Calculate a fuel ratio deviation, calculate a smoothing amount of a correction amount determining factor amount corresponding to an intake condition of the internal combustion engine according to the transient air-fuel ratio deviation, and determine a correction amount corresponding to the intake condition according to the smoothing amount. An internal combustion engine characterized in that the transient fuel correction amount obtained from the difference between the factor amount and the smoothing amount is corrected, thereby preventing deviation of the mixed gas fuel from the optimum air-fuel ratio during the transient period. An air-fuel ratio control method is provided.

Embodiment An apparatus for performing an air-fuel ratio control method for an internal combustion engine as an embodiment of the present invention is shown in FIG.

In the third device, 1 is a known electronically controlled fuel injection 6-cylinder spark ignition engine that is the power source of the automobile, 2 is a known intake air amount detection device that detects the amount of air taken into the engine 1, and 3 is a known intake air amount detection device that detects the amount of air taken into the engine 1. engine 1
4 is a known water temperature sensor that measures the cooling water temperature of the engine 1; 5 is an exhaust passage of the engine 1; 6 is an exhaust passage 5;
This is a well-known air-fuel ratio sensor installed in

7 is an intake pipe of the engine 1, 8 is a known electromagnetic fuel injection valve provided in the intake pipe 7, 9 is a throttle valve that controls the amount of air taken into the engine 1, and 91 is a sensor that detects the movement of the throttle valve 9. A well-known throttle sensor CONT is a control circuit that calculates the amount of fuel to be supplied to the engine 1 and operates the fuel injection valve 8.

When the engine is in a steady state, the amount of fuel supplied to the engine 1 is determined by the control circuit CONT as a basic fuel amount from the angle detection signals of the intake air amount detection device 2, the rotation speed sensor 3, and the water temperature sensor 4. The feedback correction amount obtained from the signal of the air-fuel ratio sensor 6 is corrected to obtain the valve opening time of the fuel injection valve 8.

In addition, the control circuit CONT is the throttle sensor 9
1 or the intake air amount detection device 2
When an acceleration state is detected, the fuel amount is increased during acceleration to a level greater than the amount of fuel determined during steady state.

The configuration of the control circuit CONT in the device shown in FIG. 3 is shown in FIG. The control circuit CONT includes, as an input system, a multiplexer 101 that receives signals from the intake air amount sensor 2 and the water temperature sensor 4, an AD converter 102, a shaping circuit 103 that receives signals from the air-fuel ratio sensor 6, and input signals from the shaping circuit and the throttle sensor 91. an input port 104 for receiving a signal from
Input counter 105 that receives the signal from rotation sensor 3
has.

The control circuit also includes a bus 106, a ROM 107,
CPU108, RAM109, output counter 11
0, and a power drive section 111. The output of the power drive section 111 is supplied to the fuel injection valve 8.

In internal combustion engines, an O ₂ sensor is used as an air-fuel ratio deviation detection means to control the engine's air-fuel ratio to the optimum air-fuel ratio. The control at that time is shown in FIGS. 5 and 6. In Figure 5, (1) air-fuel ratio sensor output signal, (2) shaped signal, (3) signal after delay processing, (4)
The signal after symmetric integration processing and the signal after (5) skip processing are shown, respectively. In Figure 5, RCH is rich, LN is lean, DR, DL is delayed, INTG
is the integral signal, V(F) is the air-fuel ratio correction signal, COR
(RCH) represents rich correction, COR (LN) represents lean correction, and RS represents skip amount. 6th
In the figure, each step of air-fuel ratio sensor signal output S1, shaping S2, delay processing S3, symmetrical integration processing S4, skip processing S5, and basic injection amount correction by F are shown. Steps S1 to S5 in FIG. 6 correspond to waveforms 1 to 5 in FIG.

In addition, the control waveform of the O ₂ sensor and the air-fuel ratio behavior when the air-fuel ratio actually becomes lean during a transient state are
As shown in the figure. As shown in Fig. 7, it is possible to detect air-fuel ratio changes from the optimum air-fuel ratio during transient periods from the air-fuel ratio correction signal V(F), but in actual vehicles, steady-state operation is rare and acceleration/deceleration is It occurs quite often. Therefore, in order to accurately detect transient air-fuel ratio fluctuations using V(F), the amount of change in V(F) when V(F) changes from a steady state where V(F) is stable is It is necessary to use this to detect transient air-fuel ratio fluctuations, and use this to correct acceleration increases and deceleration decreases.

FIG. 8 shows a schematic flowchart of the control program of the control circuit CONT. This program is for performing electronically controlled fuel injection.
It starts in S100, and in S101, memory and input/output ports are initialized. In S102,
Intake air amount data Q and engine speed data N
The basic fuel injection amount is calculated from the water temperature sensor data θ _W.

In S103, the signal from the air-fuel ratio sensor 6 is used to correct the basic fuel amount by performing feedback control so that the air-fuel ratio is constant. In S104 and S105, transient air-fuel ratio deviation detection and transient fuel correction ratio calculation are performed.

In S106, one revolution of the engine is determined, and in S107, the opening time of the fuel injection valve 8 once per engine revolution is calculated from the basic fuel amount corrected by feedback control and the transient fuel correction ratio. ,
Fuel injection valve control is performed in S108.

FIG. 9 shows a detailed flowchart of the air-fuel ratio deviation detection process in FIG. 8. This process
As shown in S201, processing is performed every time the air-fuel ratio correction signal V(F) is skipped in the air-fuel ratio feedback control. Let V(F) immediately before the skip be f _o . In S202, if the current f _o is f _i , the average value A _V (f) of the previous four skip points values f _i-1 , f _i-2 , f _i-3 , f _i-4
seek.

In S203, if the difference between the values of A _V (f) and f _i-1 , f _i-2 , f _i-3 , f _i-4 is within a certain value L _f , V(F) is stable. state. Next, in S204, the difference between A _V (f) and the current value f _i of V(F), that is, the air-fuel ratio deviation Δf from the optimum air-fuel ratio during the transient period is determined.

When the absolute value of Δf deviates from L _f , lean spikes and rich spikes occur in the air-fuel ratio.
In S205, it is checked whether the absolute value of Δf is within a certain range, and if it is outside the range, it is assumed that a lean spike or rich spike has occurred. Next, in S206, it is determined whether this spike is caused by acceleration. In the case of a spike caused by acceleration, a value D _af is calculated by dividing Δf by the acceleration amount A in S207. In the present invention, the acceleration amount A is expressed by the intake air amount variation value ΔQ/N per rotation. This D _af represents the transient air-fuel ratio deviation. That is, for lean spikes D _af
is positive, and in the case of rich spikes, D _af is negative. In S208, the transient air-fuel ratio deviation correction coefficient
Add D _af to D _p and update D _p .

FIG. 10 shows a flowchart for calculating the transient fuel correction ratio f (AEW). In S301, the intake air amount Q/N per engine rotation is determined from the intake air amount signal Q from the intake air amount detection device 2 and the rotation speed signal N from the rotation speed detection device 3.
In S302, the following process is performed every fixed time (for example, 32.7ms)
make the determination for each).

In S303, the correction coefficient C _a and the correction coefficient
C _b is determined as a relationship between the values of the transient air-fuel ratio correction coefficient D _p . In other words, the correction coefficient C _a and the smoothing coefficient C _b are determined as values corresponding to the air-fuel ratio deviation during acceleration.

In S304, (Q/N) _i , which is obtained by smoothing Q/N, is obtained from the following formula.

(Q/N) _i = (Q/N) _i-1 + {Q/N-(Q/N) _i-1 }/C _b However, (Q/N) _i calculated 32.7ms ago is (Q/N) N) Set as _i-1 .

In S305, the transient fuel correction ratio f (AEW) is calculated using the following equation from the value K determined by Q/N, (Q/N) _i , C _a and the cooling water temperature.

f(AEW)={Q/N−(Q/N) _i }×C _a ×K Here, K is a correction ratio for engine cooling and is stored in the map in advance. Also f (AEW)
takes both positive and negative values depending on the change in Q/N. Correction is performed by multiplying the basic fuel amount by the transient fuel correction ratio f (AEW).

Therefore, as shown in Figure 11, (1) When accelerating with the throttle opened (T _h is the throttle opening), (2)
The Q/N value also increases, (3) the (Q/N) _i value also gradually increases, and (4) the transient fuel correction ratio f (AEW) increases with the waveform shown in the figure. , (5) The fuel injection valve opening time U is determined and fuel is supplied.
In addition, (6) when the throttle is closed to decelerate, (7) the Q/N value decreases, (8) the (Q/N) _i value also gradually decreases, and (9) the transient fuel correction ratio f. (AEW) is reduced by taking the waveform as shown in the figure, (10) the fuel injection valve opening time U is determined, and fuel is supplied.

In carrying out the present invention, various modifications can be made in addition to the embodiments described above. For example, in the above embodiment, as shown in step S302, (Q/N) _i was calculated at fixed time intervals (32.7 ms), but instead, as shown in the flowchart of FIG. It is also possible to calculate (Q/N) _i in synchronization with the engine rotation, for example, every engine rotation. In Figure 12, in S401, Q/
N is calculated, and a determination is made for each engine rotation in S402. In S403, the correction coefficient C _a and the smoothing coefficient C _b are determined as a function of the transient air-fuel ratio correction coefficient D _p . In other words, the correction coefficient C _a and the smoothing coefficient C _b are determined as values corresponding to the air-fuel ratio deviation during acceleration.

S404 smoothed Q/N (Q/
N) Find _j using the following formula.

(Q/N) _j = (Q/N) _j-1 + {Q/N-(Q/N) _j-1 }/C _b However, (Q/N) _j calculated before one revolution of the engine
Let be (O/N) _j-1 .

In S405, the transient air-fuel ratio correction ratio f' (AEW) is calculated using the following equation from the value K' determined by Q/N, (Q/N) _j , C _a and the cooling water temperature.

f′(AEW)={Q/N−(Q/N) _j }×C _a ×K′ Correction is performed by multiplying the basic fuel amount by this f′(AEW).

By determining the above (Q/N) _j in synchronization with the engine rotation, the number of engine combustion cycles to which the increase/decrease due to the transient air-fuel ratio correction ratio f' (AEW) contributes is the same regardless of the engine rotation speed. They are almost the same under acceleration conditions. Therefore, it is possible to prevent the air-fuel ratio from fluctuating during transient periods under various engine conditions.

In addition, in the above-mentioned embodiment, the increase is made based on the intake air amount Q/N and its equivalent amount as the correction amount determining factor, but this is based on other quantities such as the intake pipe negative pressure value and the throttle opening. , may be based on the amount of consideration.

Effects of the Invention According to the present invention, the difference between the correction amount determining factor amount corresponding to intake conditions such as intake air amount per revolution, intake pipe negative pressure, throttle opening, etc. and its smoothed value is calculated at predetermined intervals. By doing so, a transient correction pattern in which the attenuation rate gradually decreases is formed, and air-fuel ratio control can be performed in which optimum correction is performed without rich/lean spikes.

Further, according to the present invention, by performing air-fuel ratio control that performs this optimal correction, rich/lean spikes are detected with high sensitivity when the transient state changes due to changes over time, etc., and learning is performed quickly. Controllability of the transient air-fuel ratio can be improved.

[Brief explanation of drawings]

Figure 1 shows how the air-fuel ratio fluctuates when deposits adhere to the back of the intake valve, Figure 2 shows how the air-fuel ratio fluctuates when the gasoline properties change, and Figure 3 shows how the air-fuel ratio fluctuates when the gasoline properties change. FIG. 4 is a diagram illustrating an apparatus for performing an air-fuel ratio control method for an internal combustion engine as an embodiment of the invention.
Figure 3 shows the configuration of the control circuit in the device; Figures 5 and 6 are signal wave diagrams and flowcharts to explain air-fuel ratio control; Figure 7 is the O ₂ sensor signal and air-fuel ratio behavior. FIG. 8 is a flowchart of the control process of the control circuit, FIG. 9 is a flowchart showing details of the air-fuel ratio deviation detection process in FIG.
Figure 10 is a flowchart of the calculation of the transient fuel correction ratio, Figure 11 is a waveform diagram showing the signal waveforms of each part of the circuit in Figure 4, and Figure 12 is a flowchart showing the flow of calculation in another example of the calculation process. be. (Explanation of symbols), 1... Engine, 2... Intake air amount detection device, 3... Rotation speed sensor, 4... Water temperature sensor, 5... Exhaust passage, 6... Air-fuel ratio sensor, 7... Intake Pipe, 8...fuel injection valve, 9...throttle valve, 91...throttle sensor,
CONT...Control circuit.

Claims (1)

[Claims] 1. Detects a transient state of the internal combustion engine, and when detecting the transient state, determines a transient fuel correction amount at predetermined intervals according to the transient state, and determines the transient fuel correction amount based on the transient fuel correction amount. In the air-fuel ratio control method for an internal combustion engine that corrects the amount of fuel supplied to the internal combustion engine, the air-fuel ratio deviation from the optimum air-fuel ratio during a transient period of the internal combustion engine is detected using the output of an air-fuel ratio sensor, A transient air-fuel ratio deviation is calculated based on the ratio of the fuel ratio deviation to the intake air amount equivalent change amount, and a smoothing amount of the correction amount determining factor amount corresponding to the intake state of the internal combustion engine is calculated according to the transient air-fuel ratio deviation. , Correcting the transient fuel correction amount obtained from the difference between the correction amount determining factor corresponding to the intake state and the smoothing amount in accordance with the smoothing amount, thereby determining the optimum emptying of the mixed gas fuel during the transient period. An air-fuel ratio control method for an internal combustion engine, characterized in that a deviation from the fuel ratio is prevented.