JPH1030479A - Air-fuel ratio controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate any slippage in an air-fuel ratio due to the response delay of a large-area type air-fuel ratio sensor. SOLUTION: Various state quantities of an engine are inputted (S1), a target air-fuel ratio TGLMD is set up (S2) from engine speed Ne and basic fuel injection quantity TP, a variation ΔQ of intake air flow rate, a variation ΔTVO of throttle valve opening, and a variation ΔA/F of air-fuel ratio detected value are all calculated (S3), while a zero-order delay till the detected value of an air-fuel ratio sensor starts its change to a target air-fuel ratio change is calculated (S4), likewise a first-order delay till the detected value comes to the target air-fuel ratio TGLMD after being changed since it has started the change is calculated (S5), and then a proportional part P is compensated from the zero- order delay (S6), and further an integral part I is compensated (S7) from the first-order delay as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to a technology for detecting an air-fuel ratio and performing feedback control to a target air-fuel ratio to improve control accuracy.

[0002]

2. Description of the Related Art A conventional air-fuel ratio control device for an internal combustion engine is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-240840. To explain the outline of this, the basic fuel supply amount _TP (= K) corresponding to the amount of air sucked into the cylinder by detecting the intake air flow rate Qa and the rotation speed N of the engine.
Qa / N; K is a minute), and this basic fuel supply amount T
_P is corrected by the engine temperature, etc., and feedback correction is performed by a signal from an air-fuel ratio sensor (oxygen sensor) that detects the air-fuel ratio of the air-fuel mixture by detecting the oxygen concentration in the exhaust gas, and correction by the battery voltage is also performed. finally setting the fuel supply quantity T _I.

[0003] Then, by outputting a driving pulse signal having a pulse width corresponding to the thus set fuel supply quantity T _I at a predetermined timing, so that injects supply a predetermined amount of fuel to the engine. In recent years, attempts have been made to improve the exhaust purification performance and the fuel efficiency by controlling the air-fuel ratio to be significantly lean, so that the air-fuel ratio is set while changing the target air-fuel ratio in a wide range according to the operating conditions. In order to perform feedback control, a so-called wide-range air-fuel ratio sensor that can linearly detect the air-fuel ratio from the oxygen concentration or the like in the exhaust gas that can cope with the feedback control is used.

[0004]

However, the air-fuel ratio sensor delays the response from the change of the target air-fuel ratio to the detection of the target air-fuel ratio, and the feedback to the target air-fuel ratio is caused by the response delay. The control, especially during the transition, has not been performed well, and the exhaust purification performance and the fuel efficiency have not yet been sufficiently improved.

The present invention has been made in view of such a conventional problem, and accurately grasps a response delay of an air-fuel ratio sensor and appropriately sets a control constant for setting a feedback correction coefficient in response to the response delay. Focusing on improving the responsiveness by setting the value, the appropriate control constant is set even during the transition when the engine operating state changes, so that it can be maintained near the target air-fuel ratio. An object is to provide an air-fuel ratio control device for an internal combustion engine.

[0006]

According to the first aspect of the present invention, as shown by the solid line in FIG. 1, the air-fuel ratio of the air-fuel mixture supplied to the engine from the components in the exhaust gas is provided in a wide range. The air-fuel ratio is made closer to the target air-fuel ratio by an air-fuel ratio detecting means to be detected and a feedback correction coefficient set by using a control constant while comparing the detected value of the air-fuel ratio by the air-fuel ratio detecting means with the target air-fuel ratio. An air-fuel ratio feedback control means for controlling an internal combustion engine, an operation state detection means for detecting an operation state of the engine, and an air-fuel ratio detection means for detecting a change in a target air-fuel ratio. A zero-order delay calculating means for calculating a zero-order delay until the detection value of the target air-fuel ratio starts to change;
First-order delay calculating means for calculating a first-order delay from when the detection value of the air-fuel ratio detecting means starts to change to detecting the changed target air-fuel ratio; and zero-order delay of the calculated air-fuel ratio detecting means. And a control constant correction means for correcting a control constant in the air-fuel ratio feedback control means based on the first-order lag.

The operation and effect of the invention according to claim 1 are as follows. When the target air-fuel ratio TGLMD changes and the control air-fuel ratio changes, as shown in FIG. 4, the air-fuel ratio detection means does not change immediately, and there is a zero-order delay before the change starts. Thus, the zero-order delay calculating means calculates the zero-order delay based on the operating state detected by the operating state detecting means.

Further, as shown in FIG. 4, there is a first-order delay from when the detection value of the air-fuel ratio detecting means starts to change to when the detection value corresponding to the target air-fuel ratio is obtained. Therefore, the primary delay calculating means calculates the primary delay based on the operating state detected by the operating state detecting means. The control constant correction means corrects the control constant in the air-fuel ratio feedback control means based on the zero-order delay and the first-order delay of the air-fuel ratio detection means thus calculated.

With this configuration, the response delay of the air-fuel ratio detecting means is calculated separately for the 0th-order delay and the 1st-order delay, and the control constant is corrected based on the calculated delay. Satisfactorily, the air-fuel ratio feedback control can be performed even during a transition. Further, the invention according to claim 2 includes an operating state detecting means for detecting an operating state of the engine and a vehicle speed detecting means for detecting a vehicle speed, as indicated by a dashed line in FIG. The means calculates the 0th-order delay based on a condition including the detected operating state of the engine, and the first-order delay calculating means calculates the detected operating state of the engine and the detected vehicle speed. The method is characterized in that the first-order lag is calculated based on the included conditions.

The operation and effect of the invention according to claim 2 are as follows. The zero-order delay of the air-fuel ratio detection means is as follows:
In addition to the delay until the exhaust gas whose air-fuel ratio has changed reaches the air-fuel ratio detection means, the intake air flow rate, the throttle valve opening change amount,
It is determined by the engine operating state such as the engine cooling water temperature and the intake air temperature. Therefore, the zero-order delay calculating means can accurately calculate the zero-order delay based on the conditions including the various engine operating states detected by the operating state detecting means.

The primary delay of the air-fuel ratio detecting means is determined by the amount of change of the intake air flow, the amount of change of the air-fuel ratio, the temperature of the engine cooling water, the temperature of the intake air, the vehicle speed, etc., in addition to the amount of intake air. Is done. Therefore, the first-order lag calculating means includes:
The first-order lag can be accurately calculated based on the conditions including the various engine operating states detected by the operating state detecting means and the vehicle speed detected by the vehicle speed detecting means.

According to a third aspect of the present invention, the air-fuel ratio feedback control means sets a feedback correction coefficient including a proportional component and an integral component as control constants, and the control constant correction means sets the zero-order The proportional component is corrected according to the 0th-order delay calculated by the delay calculation means,
It is characterized in that the integral is corrected according to the primary delay calculated by the secondary delay calculating means.

The functions and effects of the invention according to claim 3 are as follows. The proportional component is corrected according to the 0th-order lag, and 1
By correcting the integral according to the next delay, the correction corresponding to each delay is performed, and the air-fuel ratio feedback control during the transient can be performed as well as possible.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing a system configuration according to 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 Qa and a throttle valve 14 for controlling the intake air flow rate Qa in conjunction with an accelerator pedal. In the downstream manifold portion, an electromagnetic fuel injection valve 15 is provided for each cylinder as fuel supply means.

The fuel injection valve 15 is driven to open by an injection pulse signal from a control unit 16 containing a microcomputer, and is supplied by pressure from a fuel pump (not shown) to inject and supply fuel controlled to a predetermined pressure by a pressure regulator. . Further, a water temperature sensor 17 for detecting a cooling water temperature Tw in a cooling jacket of the engine 11, an intake air temperature sensor 31 for detecting an intake air temperature T _AIR, and a throttle sensor 32 for detecting an opening TVO of the throttle valve 14 are provided. And a wide-range air-fuel ratio sensor 19 for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the concentration of oxygen in the exhaust gas in the exhaust passage 18.
Three-way catalyst 20 that purifies by oxidizing HC and reducing NO _X 20
Is provided.

A distributor (not shown) has a built-in crank angle sensor 21. The control unit 16 receives a crank unit angle signal output from the crank angle sensor 21 in synchronization with the engine rotation and outputs a constant signal. The engine speed Ne is detected by counting time or measuring the cycle of the crank reference angle signal. Further, a vehicle speed sensor 33 for detecting a vehicle speed VSP is provided on a transmission output shaft or the like (not shown).

The control unit 16
The target air-fuel ratio TGLMD is set based on the engine operating state, and the fuel injection valve 15 is set based on the air-fuel ratio detection value from the air-fuel ratio sensor 19 so that the target air-fuel ratio TGLMD is obtained.
The feedback control of the air-fuel ratio is performed by controlling the fuel injection amount from the air-fuel ratio.At this time, the response delay of the air-fuel ratio sensor 19 is calculated, and the control constant is corrected based on the response delay, thereby making the transient. Control with good responsiveness can be performed even during operation.

Hereinafter, the routine of the air-fuel ratio feedback control will be described with reference to the flowchart of FIG. Step (referred to as S in the figure; hereinafter the same) In step 1, the engine rotation speed Ne is calculated based on the signal from the crank angle sensor 21, the intake air flow rate Q detected by the air flow meter 13, the air-fuel ratio sensor The air-fuel ratio A / F detected by 19, the cooling water temperature (hereinafter referred to as water temperature) Tw detected by the water temperature sensor 17, the intake air temperature T _AIR detected by the intake air temperature sensor 31, and detected by the throttle sensor 32 Throttle valve opening TV
O: The vehicle speed VSP detected by the vehicle speed sensor 33 is input, and the fuel injection valve 15 calculated by another routine is input.
, The basic fuel injection amount T _P (= K · Q / Ne; K is a constant).

[0019] In step 2, the based on the engine rotational speed Ne and basic fuel injection quantity T _P, the target air-fuel ratio TGLMD commensurate with the operating region, set by the retrieval or the like from the map. In step 3, a change amount ΔQ per unit time of the intake air flow rate Q, a change amount ΔTVO per unit time of the throttle valve opening TVO, and a change amount ΔA / F per unit time of the air-fuel ratio A / F are calculated. .

In step 4, the 0th-order delay until the detection value A / F of the air-fuel ratio sensor 19 starts to change with respect to the change in the target air-fuel ratio TGLMD is determined by the following equation. It is calculated as a function of the amount of change ΔTVO per unit time of the throttle valve opening TVO, the water temperature Tw, and the intake air temperature T _AIR . The function of step 4 corresponds to the zero-order delay calculating means.

Zero-order delay = K ₁ ｛f ₁ (Q) + f ₂ (ΔT
VO) + f ₃ (Tw, T _AIR ) −e ₁ ｝ + B ₁ where e ₁ is an error due to fuel wall flow and the like, and B ₁ is a constant determined by the mounting position of the air-fuel ratio sensor 19.
The equation of the zero-order delay will be described. The operating state parameters for determining the zero-order delay include the change amount ΔTV per unit time of the intake air flow rate Q and the throttle valve opening TVO.
O, water temperature Tw and intake air temperature T _{AIR There are} water temperature Tw and intake air temperature T _AIR , and f ₁ , f ₂ , and f ₃ are
(Contribution rate to zero-order delay) × (conversion coefficient of each parameter to zero-order delay).

Of course, Q, ΔTVO, Tw, and T _AIR include factors of flow velocity, temperature, and pressure that affect the time that exhaust gas reaches the air-fuel ratio sensor. Referring now to B _1, which, as shown in FIG. 5, the correlation of the primary between the operating state and the 0-order lag (linearity) is determined in a certain region, indicating a linear line and 0-order lag This is a value obtained as an intersection with the vertical axis, and is a value substantially determined by the mounting position of the air-fuel ratio sensor as described above. That is, in the state where the vehicle is not actually driving, the 0th-order lag is 0, but when the value of each operation parameter is small due to the end effect, the correlation is not satisfied. Generally, the flow is affected by the viscous term in the case of laminar flow, and becomes non-linear with respect to the influencing factor (mainly ΔP). Sex is enhanced. Looking at the flow of exhaust gas from the internal combustion engine, the idle region is already a turbulent region.

In step 5, the primary delay until the detected value A / F of the air-fuel ratio sensor 19 becomes the target air-fuel ratio TGLMD after the change with respect to the change in the target air-fuel ratio TGLMD is expressed by the following equation. It is calculated as a function of the change amount ΔQ of the intake air flow rate, the change amount ΔA / F of the air-fuel ratio, the water temperature Tw, the intake air temperature T _AIR , and the vehicle speed VSP. The function of step 5 corresponds to a zero-order delay calculating means.

First order delay = K ₂ ｛f ₄ (ΔQ) + f ₅ (Δ
A / F) + f ₆ (Tw, T _AIR ) + f ₇ (VSP) -e
₂ ｝ + B ₂ Here, e ₂ is an error amount, and B ₂ is a constant retrieved from a map or the like from the intake air flow rate Q or the like. F ₇ (VS
P) is an amount corresponding to the cooling amount of the vehicle body determined by the traveling wind.

The equation for the first-order lag is set in the same way as the zero-order lag. In step 6, the proportional component P is corrected and set by the function f of the zero-order delay (zero-order delay), for example, a constant multiple of the zero-order delay as in the following equation. P = P ₀ + f (0th order delay) Here, P ₀ may be a fixed value, but may be set as a constant corresponding to a steady operation state for each operation region.

In step 7, the first order lag function f
(Primary delay) For example, the integral I is corrected and set according to a constant multiple of the primary delay as in the following equation. I = I ₀ + f (first-order delay) Here, I ₀ may be a fixed value, but may be set as a constant corresponding to a steady operation state for each operation region.

The functions of steps 6 and 7 correspond to control constant correction means. As described above, the response delay of the air-fuel ratio sensor 19 is calculated by dividing the response delay into the zero-order delay and the first-order delay, and the proportional component and the integral component, which are the control constants, are corrected based on them. , A good air-fuel ratio feedback control can be performed even during a transition.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the invention according to claims 1 and 2;

FIG. 2 is a diagram showing a system configuration of an embodiment according to the present invention.

FIG. 3 is a flowchart showing a routine for calculating a response delay and correcting a control constant of the air-fuel ratio sensor according to the present invention.

FIG. 4 is a time chart for explaining a response delay of the air-fuel ratio sensor.

FIG. 5 is a diagram showing a relationship between an operating state and a zero-order delay.

[Explanation of symbols]

 11 Internal combustion engine 13 Air flow meter 15 Fuel injection valve 16 Control unit 17 Water temperature sensor 19 Air-fuel ratio sensor 21 Crank angle sensor 31 Intake air temperature sensor 32 Throttle sensor 33 Vehicle speed sensor

Claims (3)

[Claims] 1. An air-fuel ratio detecting means provided in an exhaust passage for detecting an air-fuel ratio of an air-fuel mixture supplied to an engine from a component in exhaust gas over a wide range, an air-fuel ratio detected value by the air-fuel ratio detecting means, and a target air-fuel ratio. An air-fuel ratio feedback control means for controlling the air-fuel ratio to be close to the target air-fuel ratio by a feedback correction coefficient set using a control constant while comparing A zero-order delay calculating means for calculating a zero-order delay until the detection value of the air-fuel ratio detecting means starts to change with respect to a change in the target air-fuel ratio; and the air-fuel ratio detecting means with respect to a change in the target air-fuel ratio. A first-order delay calculating means for calculating a first-order delay from when the detected value of は じ め starts to change until a target air-fuel ratio after the change is detected; and a zero-order lag and a first-order lag of the calculated air-fuel ratio detecting means. Based Te, the air-fuel ratio control apparatus for an internal combustion engine, characterized in that configured to include a control variable correcting means for correcting the control constant in the air-fuel ratio feedback control means. 2. An operating state detecting means for detecting an operating state of the engine, and a vehicle speed detecting means for detecting a vehicle speed, wherein the zero-order lag calculating means is adapted to a condition including the detected operating state of the engine. Calculating the first order delay based on a condition including the detected operating state of the engine and the detected vehicle speed. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein 3. The air-fuel ratio feedback control means sets a feedback correction coefficient including a proportional component and an integral component as control constants, and the control constant correction means sets a feedback correction coefficient calculated by the zero-order delay calculating means. 3. The internal combustion engine according to claim 1, wherein the proportional component is corrected according to a secondary delay, and the integral component is corrected according to a primary delay calculated by the primary delay calculating unit. 4. Engine air-fuel ratio control device.