JPH04101035A - Air/fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To obtain proper transient air/fuel ratio all the time without being affected by a carburetion characteristic of gasoline by increasing a fuel injection amount when an engine is in an acceleration state and by gradually decreasing an increase when not in the acceleration state and air fuel ratio is in a rich state. CONSTITUTION:Pressure in an intake pipe 2 connected to an engine 1 is detected by a pressure sensor 4, temperature of an engine 1 is detected by a water temperature sensor 10, revolution of the engine 1 is detected by a revolution sensor 5, and air/fuel ratio in an exhaust pipe 7 is detected by an air/fuel ratio sensor 8. And a required fuel amount is calculated at a control part 9 from information of the sensors 4, 5, 8 and 10, and an injector 6 is driven and controlled according to it. In this case, a fuel injection amount is increasingly corrected when an acceleration state of the engine is more than a predetermined value. And when the acceleration state is less than the predetermined value and the air/fuel ratio is in a rich state, an increase is gradually decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an air-fuel ratio control device for an engine, and is particularly adapted to correct deviations in the air-fuel ratio during transient periods.

[Conventional technology]

Generally, during transient operation of an engine, a different amount of fuel is required than in a steady state. For this reason, conventional devices (for example, Japanese Patent Publication No. 49-45646) calculate the rate of change in the intake pipe pressure or throttle valve position, which represents the engine load condition, and when this rate of change exceeds a predetermined value, an acceleration increase signal is sent. The amount of fuel injected was increased in response to the increase in fuel injection amount, and then the amount was gradually decreased as time elapsed.

FIG. 1 shows the configuration of a conventional device and a device of the present invention, in which 1 is an engine, 2 is an intake pipe connected to the engine 1, and 3 is a throttle valve provided in the intake pipe 2. The pressure inside the intake pipe 2 is detected by a pressure sensor 4, and the detected force is sent to an A/D converter 91. Also, the engine
A signal from the water temperature sensor 0 that detects the temperature of the water is also sent to the A/D converter 91. Further, the rotation of the engine I is detected as a pulse by the rotation sensor 5, and the output of the rotation sensor 5 is sent to the input circuit 92. Further, fuel is injected by an intake pipe 2 injector 6, and this injector 6 is driven by the output of an output circuit 96.

Further, an exhaust pipe 7 is connected to the engine 1, and an output corresponding to the air-fuel ratio of the exhaust gas components in the exhaust pipe 7 is outputted from the air-fuel ratio sensor 8 to the A/D converter 91. Further, the control unit 9 calculates the required amount of fuel from the information of each sensor 4, 58.10, and generates a driving pulse for the injector 6 with a width corresponding to the required amount of fuel. The A/D converter 91 connects each sensor 4
．． The analog signal of 810 is converted into a digital value and sent to the microprocessor 93. The input circuit 92 also converts the level of the pulse input signal from the rotation sensor 5 and sends it to the microprocessor 93.

The microprocessor 93 calculates the amount of fuel to be supplied to the engine I based on the digital and pulse signals obtained from the A/D converter 91 and the input circuit 92, and outputs the driving pulse width of the injector 6 according to the result. Note that the air-fuel ratio sensor 8 is a λ02 sensor that determines the stoichiometric air-fuel ratio.

Next, the operation of the conventional device will be explained using the flowchart shown in FIG. 2 and the waveform diagrams shown in FIGS. In step 401, a pulse signal input from the rotation sensor 5, that is, the engine rotation speed N, is read, and in step 4
In step 02, the intake pipe internal pressure (absolute pressure) P, obtained from the pressure sensor 4 is read, and in step 403, the basic injection amount Q0 is determined from Q, =, , P, ·η9. In addition, K
1 is a constant, η1 is intake pipe pressure P, and engine speed N
.

The filling efficiency is determined by Next, in step 404, the output of the air-fuel ratio sensor 8 is read, and if the output is greater than the determination level λ1, it is determined that the output is rich or low, and in step 405, the integral gain is decreased when rich, and increased when lean. Then, the feedback correction coefficient C'FII is calculated. In step 406, the basic injection amount Q0 is corrected by Q,=Qo-Crg to obtain the injection amount Q1. Note that Qo is actually the water temperature sensor 1.
According to the output of 0, the amount is corrected to increase when the temperature is low.

Further, in step 407, the amount of change ΔP of the intake pipe internal pressure P at fixed time intervals is expressed as ΔP b=P bffil P
1++1l-11 (n is the sample time).

In step 408, it is determined whether or not the amount of change ΔPb of the intake pipe internal pressure P5 at fixed time intervals is greater than or equal to a predetermined value α, and if it is greater than or equal to the predetermined value α, in step 409 the engine rotation speed N and the water temperature sensor 1o are determined. The acceleration increase amount Q, cc is calculated from a predetermined value according to the output of and ΔP. On the other hand, if ΔP is less than α, in step 410, Qmcc
= Q-cc

That is, when the change in the intake pipe pressure ΔP disappears, Q m
c c is also gradually reduced to zero. In step 411, for the injection amount Q1, Q 2 = Q + + Q a cc
Acceleration correction is performed by In step 412, 2
- The injection amount Q2 is converted into the injection pulse width τ of the injector 6 by Q2 (Kz is a constant), and the injector 6 is driven by the output circuit 96 for a driving time τ.

[Problem to be solved by the invention] In the conventional engine air-fuel ratio control device described above,
The fuel injection amount during the transient period is corrected by a predetermined fuel amount in response to changes in the pressure inside the intake pipe. Here, the deviation in the air-fuel ratio during a transient period of the speed density type fuel injection device is due to a delay in detecting a change in intake air, that is, a change in the pressure inside the intake pipe, or due to a change in the pressure inside the intake pipe in response to a change in load. This is because the vaporization speed of the gasoline injected from the injector 6 changes. These deviations can be determined in advance through engine tests, and
The correction amount can be set in the ROM 94 in the control unit 9. However, if the fuel composition, especially the vaporization characteristics, supplied to the engine are significantly different from those during the engine test when the correction amount was set, the air-fuel ratio during the transient period will not improve, but will deviate significantly, causing major problems in driving performance. I'll wake you up. In other words, when accelerating with low-volatility gasoline using the correction amount set for regular gasoline, the vaporization rate of gasoline changes in response to the load change described above (generally, the time required for vaporization of gasoline is determined by the suction pressure. (Accordingly, during acceleration, the intake pipe pressure changes to the higher side, so the amount of vaporization per unit time decreases.) In addition, gasoline itself has poor vaporization properties, so there is a significant air-fuel ratio deviation. occurs.

This invention has been made to solve the above-mentioned problems, and provides an engine air-fuel ratio control device that can always obtain an appropriate transient air-fuel ratio without being affected by the vaporization characteristics of gasoline. The purpose is to

[Means to solve the problem]

The air-fuel ratio control device for an engine according to the present invention includes a correction means for increasing the fuel injection amount when the acceleration state of the engine is above a predetermined value, and a correction means for increasing the fuel injection amount when the acceleration state is below the predetermined value and the air-fuel ratio is in a rich state. It is provided with an adjusting means for gradually decreasing the amount increased.

Further, the air-fuel ratio control device for an engine according to the present invention includes a correction means for increasing the fuel injection amount when the acceleration state of the engine is equal to or higher than a predetermined value, and a correction means for increasing the amount of fuel injection when the acceleration state of the engine is equal to or lower than a predetermined value. In addition, an adjusting means is provided for increasing the rate of gradual decrease when the air-fuel ratio is in a rich state.

[Operation] In this invention, the fuel injection amount is increased when the engine is in an accelerating state, and this increased amount is gradually decreased when the air-fuel ratio is in a rich state rather than in an accelerating state.

Therefore, in the lean state, the increased amount is not gradually reduced, and the air-fuel ratio deviation is eliminated.

Further, in this invention, the fuel injection amount is increased when the engine is in an accelerating state, and this increased amount is gradually decreased when the engine is not in an accelerating state. However, when the air-fuel ratio is in a rich state, the gradual reduction speed becomes faster and the air-fuel ratio deviation is eliminated.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. The configuration of this embodiment is the same as that in FIG. 1, but the arithmetic processing and data setting centering on the microprocessor sensor 93 in the control section 9 are partially different from the conventional one.

The operation will be explained below with reference to the flowchart of FIG. 5 and the waveform diagram of FIG. 6. Steps 201-209 are similar to conventional steps 401-409. Step 208
If ΔP1 is less than α, the process proceeds to step 210, and in step 210, if the output of the air-fuel ratio sensor 8 is greater than the determination level λ, (which may be equal to or different from λ), it is determined to be rich, If it is smaller than λ2, it is determined to be lean. In the case of lean, the process advances to step 212 while maintaining the acceleration increase amount Qicc and performs acceleration correction,
In step 213, it is converted into the injection pulse width τ of the injector 6. If it is rich, the process proceeds to step 211, where Q a c c is gradually decreased over time by an acceleration increase/decrease calculation, and the process proceeds to step 212 .

In the above-described embodiment, the increased amount is not gradually reduced in the lean state even when the engine is not in the acceleration state, so the deviation in the air-fuel ratio is quickly resolved.

FIG. 7 is a flowchart according to a second embodiment of the present invention, and steps 201 to 213 are the same as in the first embodiment. If ΔP is less than α, it is determined in step 214 whether or not the air-fuel ratio sensor 8 is normal; if it is normal, it is determined in step 215 whether or not the air-fuel ratio sensor 8 is active;
If it is active, proceed to step 210. That is, when the air-fuel ratio sensor 8 is normal and active and is in a lean state, the gradual reduction of the increased amount is stopped. This is intended to perform a gradual reduction stop when the output of the air-fuel ratio sensor 8 is reliable, thereby achieving better control.

Note that in steps 205 and 206, the air-fuel ratio sensor 8
The integral term of the air-fuel ratio feedback may be held when the output of the air-fuel ratio is less than λ1, that is, lean.

The flow chart in FIG. 8 and the waveform chart in FIG.
c=QaccX Ks (0<KS<1) to gradually reduce the amount of increase and increase the air-fuel ratio.

In the case of Q, the process advances to step 217 and Qmcc-Q-c
The increased amount is gradually reduced by cXKa (0<Ka<Ks<1). That is, in this example, when the air-fuel ratio is lean, the gradual deceleration speed is slowed down to suppress deviations in the air-fuel ratio due to poor fuel vaporization, and in the case of Lynch, there is no need to slow down the gradual deceleration speed, so the gradual deceleration speed is (do it quickly. Other actions are the first
This is similar to the embodiment.

FIG. 10 shows a fourth embodiment of the present invention, and similarly to the second embodiment, if the output of the air-fuel ratio sensor 8 is lean when the air-fuel ratio sensor 8 is normal and active, the gradual deceleration speed is slowed down. However, under other conditions, the rate of gradual decline is increased.

In each of the above embodiments, the case of a speed density type fuel injection device has been described, but the same effect can be achieved even in the case of other fuel injection devices.

[Effects of the Invention] As described above, according to the present invention, when the air-fuel ratio is lean, the gradual decrease in the acceleration increase in fuel injection is stopped, thereby preventing deviations in the air-fuel ratio due to poor vaporization of the fuel. I can do it.

Furthermore, according to this invention, the gradual decrease speed of acceleration increase is slowed when the air-fuel ratio is lean, and the gradual decrease speed is increased when the air-fuel ratio is lean, so deviations in the air-fuel ratio due to poor vaporization are also prevented. In addition, if a fuel with good vaporization properties is used, appropriate measures can be taken.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the conventional device and the device of this invention, and Figures 2 to 4.
The figure shows a flowchart and a waveform diagram showing a second example of the operation of the conventional device, FIGS. 8 and 9 are flowcharts and waveform diagrams according to the third embodiment of the present invention, and FIG. 10 is a flowchart according to the fourth embodiment of the present invention. 1... Engine, 2... Intake pipe, 3... Throttle valve,
4... Pressure sensor, 5... Rotation sensor, 6... Injector, 7... Exhaust pipe, 8... Air-fuel ratio sensor,
9...Control unit, 10...Water temperature sensor. Figure 1 Agent Masuo Oiwa 5 times η' 10, '$iJ5I=NR Figure 3 Figure Figure Figure Figure Procedure Correction 6° Contents of Amendment July 23, 1991 Details Calligraphy No. 1 0, line 9 of the original handwriting, “Nao,

Claims (2)

[Claims] (1) an injector that supplies fuel to the engine; an air-fuel ratio detection means that detects the air-fuel ratio of exhaust gas from the engine;
A control means for feedback controlling the fuel injection amount so that the air-fuel ratio becomes a predetermined value; an acceleration state detection means for detecting the acceleration state of the engine; an air-fuel ratio control device for an engine, comprising: a correction means for adjusting the amount; and an adjustment means for gradually decreasing the increased amount when the acceleration state is below a predetermined value and the air-fuel ratio is in a rich state. (2) an injector that supplies fuel to the engine; and an air-fuel ratio detection means that detects the air-fuel ratio of exhaust gas from the engine;
A control means for feedback controlling the fuel injection amount so that the air-fuel ratio becomes a predetermined value, an acceleration state detection means for detecting the acceleration state of the engine, and a correction means for increasing the fuel injection amount when the acceleration state is equal to or higher than the predetermined value. and adjusting means for gradually decreasing the amount of increase when the acceleration state is below a predetermined value and increasing the gradual reduction rate when the acceleration state is below a predetermined value and the air-fuel ratio is in a rich state. Engine air-fuel ratio control device.