JPH10220268A - Engine control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an air fuel ratio without applying uncomfortable feeling to a driver by judging the degree of influence applied to driver's feeling by fluctuation of the air-fuel ratio, and changing feed back gain on the basis of its result. SOLUTION: An engine control system is provided with a feed back control unit 60 and a feed back gain calculating unit 70. In the feed back control unit 60, a signal E outputted from an oxygen sensor is inputted, and a feed back correcting signal Fba is decided on the basis of the output signal E so as to carry out O2 feed back control. A leaning data is collected to correct the difference between a model base control unit 20 and a real engine 1. In the feed back gain calculating unit 70, the degree of influence taken to a driver's feeling is judged by fluctuation of an air-fuel ratio during O2 feed back controlling, and a feed back gain (g) in the feed back control unit 60 is decided in the range in which uncomfortable feeding is not taken to a driver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control system for controlling an air-fuel ratio according to a predetermined target value.

[0002]

2. Description of the Related Art With the recent tightening of exhaust gas regulations, air-fuel ratios have been controlled to reduce unburned gas. As the control method of the air-fuel ratio, as shown in FIG. 14, the basic fuel injection amount is determined based on the operation information of the engine, and at the same time, the correction coefficient calculation unit adapts the current operation information from the operation information. The correction coefficient is calculated as described above, the basic fuel injection amount is multiplied by the correction coefficient, an oxygen sensor is provided in the exhaust pipe of the engine, the output of the oxygen sensor is fed back, and the feedback control unit performs the correction. A so-called O2, which determines and outputs a feedback correction signal for further correcting the basic fuel injection amount.
Generally, feedback control is used. In the O2 feedback control, since the oxygen sensor reacts only to the stoichiometric air-fuel ratio, as shown in FIG. 6B, the air-fuel ratio is periodically changed to rich so that the oxygen sensor repeats ON / OFF periodically. The air-fuel ratio is maintained in a predetermined range by maintaining the air-fuel ratio in a state that the air-fuel ratio fluctuates lean.

[0003]

However, when the air-fuel ratio is periodically varied between rich and lean in order to use the oxygen sensor as described above, FIG.
As shown in the figure, the torque also fluctuates with it, and depending on the operating state of the engine, the driving environment, etc., the fluctuation of the torque becomes a level that can be experienced, and it may give an unpleasant feeling to the driver. There's a problem. In particular, in the conventional O2 feedback control, the air-fuel ratio is changed based only on the output of the oxygen sensor without considering the influence of the change in the air-fuel ratio on the driver's feeling, so that the driver feels uncomfortable. Likely to give. In the conventional O2 feedback control described above, the fuel injection amount is determined based on the output of the oxygen sensor fed back, so that high responsiveness is required to increase control accuracy, and as a result, responsiveness is improved. For this purpose, the feedback gain is increased, and the air-fuel ratio is changed in a stepwise manner as shown in FIG. 11 (c). Therefore, there is a problem that the fluctuation of the torque increases. The present invention
An engine capable of solving the above-mentioned problems of the engine control system using the conventional oxygen sensor and performing the air-fuel ratio control without giving an unpleasant feeling to the driver even when the oxygen sensor is used as the air-fuel ratio sensor. It is intended to provide a control method.

[0004]

In order to achieve the above object, an engine control system according to claim 1 of the present invention comprises:
Feedback the exhaust air-fuel ratio using an air-fuel ratio sensor,
Judgment of the degree of influence of the change in the air-fuel ratio on the driver's feeling in an engine control system that performs feedback control to maintain the air-fuel ratio in a state where the output of the air-fuel ratio sensor repeats ON and OFF periodically. Then, the feedback gain is changed based on the result. According to the engine control method of the present invention, the exhaust air-fuel ratio is fed back using the air-fuel ratio sensor, and the air-fuel ratio is changed so that the output of the air-fuel ratio sensor periodically repeats ON and OFF. In the engine control system that performs feedback control to maintain the state of the air conditioner, the degree of influence of the change in the air-fuel ratio on the driver's feeling is determined, and the ON / OFF cycle of the air-fuel ratio sensor is changed based on the result. It is characterized by the following.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an engine control system according to the present invention will be described below with reference to an embodiment shown in the accompanying drawings. FIG. 1 is a schematic diagram showing a relationship between an engine 1 and a control device 10 capable of executing an engine control method according to the present invention. In the engine 1, an air-fuel mixture is introduced into a combustion chamber of a cylinder 5 via an air cleaner 3 and a fuel injection device 4 provided in an intake pipe 2, and exhaust gas after combustion is exhausted to the atmosphere via an exhaust pipe 6. This is a four-cycle engine, and other components such as an intake valve and an exhaust valve are omitted in the drawing. In FIG. 1, reference numeral 7 denotes a crankcase, and reference numeral 8 denotes a throttle valve. The control device 10 controls the value of the air-fuel ratio in the exhaust gas by operating the amount of fuel injection from the fuel injection device 4. As shown in FIG. 1, the control device 10 includes information α regarding the throttle opening obtained from a throttle opening detecting means 12 provided in the throttle valve 8.
And information r about the crank angle obtained from the crank angle detecting means 13 provided on the crankcase 7 and information tw about the intake pipe wall temperature obtained from the intake pipe wall temperature detecting means 14 provided on the intake pipe 2. Based on the input information, an operation amount Mf (that is, a fuel injection amount) of the fuel injection device 4 provided in the intake pipe 2 is determined and output, and an oxygen sensor provided in the exhaust pipe 6 is output. A detection signal E relating to the actual air-fuel ratio obtained from 15 is input as necessary, and correction and learning based on this information are performed so that optimal control can always be performed. FIG. 2 is a schematic block diagram illustrating a configuration of the control device 10. Control device 1
0 is a model base control unit 20 that determines a fuel injection amount using a feedforward control logic along a target air-fuel ratio Ep, a target air-fuel ratio calculation unit 30 that calculates the target air-fuel ratio Ep, and an engine speed calculation unit 40 A feedback control unit 60 that performs O2 feedback control based on an output from the oxygen sensor 15 while executing feedforward control by the model base control unit 20 in order to correct a shift of the model base control unit 20; And a feedback gain calculating section 70 for determining the feedback gain g in the feedback control section 60 in consideration of the influence of the change in the air-fuel ratio during O2 feedback control on the driver's feeling. Perform control mode or feed forward control Executes want the O2 feedback control to operate in one of the feedback correction mode. The model base controller 20 calculates the engine speed n calculated by the engine speed calculator 40, the throttle opening α, the intake pipe wall temperature tw, and the target air-fuel ratio Ep calculated by the target air-fuel ratio calculator 30. The basic operation amount Mfn of the fuel injection device 4 is determined based on the input information, and the conversion unit 50 converts the basic operation amount Mfn into a fuel injection cycle of the engine 1 and converts the basic operation amount Mfn into an operation amount Mf. Output from The target air-fuel ratio calculation unit 30 receives the engine speed n and the throttle opening α, determines a target air-fuel ratio Ep that matches the operating state of the engine based on these information, and determines a model-based control unit. 20.
The feedback control unit 60 and the feedback gain calculation unit 70 function only when the control device 10 is put into the feedback correction mode. The feedback control unit 60 receives an output signal E from the oxygen sensor 15,
A feedback correction signal FB based on the output signal E;
a is determined and output to the model-based control unit 20 to perform O2 feedback control to acquire learning data for correcting a deviation between the model-based control unit 20 and the actual engine 1; Is O
(2) The degree of influence of the change in the air-fuel ratio during the feedback control on the driver's feeling is determined, and the feedback gain in the feedback control unit 60 is determined within a range that does not give the driver an unpleasant feeling.

(Regarding the Model Base Control Unit) The configuration of the model base control unit 20 will be described below with reference to FIGS. FIG. 3 is a schematic block diagram showing the configuration of the model base control unit 20 in FIG. The model-based control unit 20 includes an air system forward model 21 that models the behavior of air in the intake pipe 2, a fuel system forward model 22 that models the behavior of fuel injected from the fuel injection device 4, and each forward model. An estimated air-fuel ratio calculation unit 23 that calculates an estimated air-fuel ratio Ev based on the estimated air amount Av and the estimated fuel amount Fv output from 21 and 22 is provided. Further, the model base control unit 20 includes a feedback loop for feeding back the estimated air-fuel ratio Ev output from the estimated air-fuel ratio calculation unit 23 to the basic operation amount calculation unit 24. The basic manipulated variable calculator 24 receives the estimated air-fuel ratio Ev output from the estimated air-fuel ratio calculator 23 and the target air-fuel ratio Ep output from the target air-fuel ratio calculator 30 and receives the fuel injection device of the engine 1. Then, a basic operation amount Mfn (basic fuel injection amount) with respect to No. 4 is calculated. The basic operation amount Mfn is output from the model base control unit 20 and also input to the fuel system forward model 22, and the fuel system forward model 22 calculates an estimated fuel amount Fv based on the basic operation amount Mfn. As described above, in the model base control unit 20, a forward model of the engine 1 is configured by the air system forward model 21, the fuel system forward model 22, and the estimated air-fuel ratio calculation unit 23, and the fuel system forward model 22, Estimated air-fuel ratio calculator 23 and basic manipulated variable calculator 2
Engine 1 using a feedback loop including
Of the engine which outputs the basic operation amount Mfn by feeding back the estimated air-fuel ratio Ev output from the forward model.

FIG. 4 is a schematic block diagram showing the structure of the fuel system forward model 22. The fuel system forward model 22 is a model of the behavior of the fuel injected from the fuel injection device 4 as described above. The fuel system forward model 22 includes a non-adhered fuel operation unit 22a, an adhering fuel operation unit 22b, and first-order lag units 22c and 22c.
2d, a fuel adhesion rate estimating unit 22e, and an evaporation time constant estimating unit 22f. The fuel actually entering the cylinder 8 is calculated from the basic operation amount Mfn (basic fuel injection amount) input from the basic operation amount calculating unit 24. Estimate the amount. The fuel adhesion rate estimating unit 22e calculates the engine speed n and the throttle opening α
The fuel adhesion rate x is modeled by using a fuzzy neural network, a neural network, or a CMAC or the like in which the relationship between the fuel adhesion rate x and the fuel adhesion rate x has been learned in advance. Based on the information, a ratio x (hereinafter, referred to as a fuel adhesion rate x) of the fuel injected from the fuel injection device 4 adhering to the wall surface of the intake pipe 2 or the like.
Is estimated. Although not shown, the fuel adhesion rate estimating unit 22e generates learning data based on a comparison result between the actual air-fuel ratio and the target air-fuel ratio Ep when the operating state of the engine is in a transient state, if necessary. It can be configured to be able to input and correct an error of the forward model of the fuel system caused by a change over time or the like, so that learning can be performed. In addition, the evaporation time constant estimating unit 22
f represents a fuzzy neural network, a neural network, a CMAC, or the like in which the relationship between the engine speed n, the throttle opening α, the intake pipe wall temperature tw (or the engine water temperature), and the evaporation time constant τ is learned in advance. Is used to model the evaporation time constant τ. The engine speed n, the throttle opening α, and the intake pipe wall temperature tw (or the engine water temperature) are input, and based on these information, the evaporation time constant τ is attached to the wall. A time constant τ at which the fuel evaporates (hereinafter, an evaporation time constant τ) is estimated.
The evaporating time constant estimating unit 22f is not shown as in the case of the fuel adhesion rate estimating unit 22e.
Inputting learning data based on the result of comparison between the actual air-fuel ratio and the target air-fuel ratio Ep when the operating state of the engine is in a transient state, and correcting errors in the fuel system forward model caused by aging and learning. It can be configured to be able to. The fuel adhesion rate estimating unit 22e and the evaporating time constant estimating unit 22f are disclosed in detail in Japanese Patent Application No. 8-271188 filed on Oct. 14, 1996 by the present applicant. The non-adhered fuel calculation unit 22a is configured to calculate the basic operation amount Mfn (ie, the basic operation amount Mfn input from the basic operation amount calculation unit 24) based on the fuel adhesion ratio x obtained from the fuel adhesion ratio estimation unit 22e.
The amount of fuel directly entering the combustion chamber of the cylinder 5 from the fuel injection device 4 in the basic fuel injection amount is calculated. The adhering fuel calculation unit 22b once adheres to the wall surface in the basic operation amount Mfn (basic fuel injection amount) input from the basic operation amount calculation unit 24 based on the fuel adhesion ratio x obtained from the fuel adhesion ratio estimating unit 22e. After that, the amount of fuel entering the cylinder 5 is calculated. The amount of fuel obtained from the non-adhered fuel operation unit 22a and the amount of fuel obtained from the adhering fuel operation unit 22b are respectively equal to the primary delay unit
In c and 22d, after being approximated by a first-order lag system based on the evaporation time constants τ1 and τ2 obtained from the evaporation time constant calculation unit 22f, they are added and output from the fuel system forward model 22 as an estimated fuel amount Fv. . Normally, when modeling the behavior of the fuel injected from the fuel injection device 4 in the engine 1, the dead time until the injected fuel enters the cylinder 5 from the fuel injection device 4 is considered in FIG. A phase delay unit 2 for the dead time which delays the phase by the dead time as shown in FIG.
Although it is necessary to provide 2 g, the fuel system forward model 22 in this embodiment eliminates the need to provide the dead time phase delay unit 22 g by advancing the phase of the fuel system forward model by the dead time. As a result, the fuel system forward model 22 becomes a simple first-order lag system.
In the case where feedback control is performed using the output of No. 2, the feedback gain can be increased, and an accurate inverse model that can obtain an appropriate basic operation amount even during a transition is configured.

FIG. 5 is a schematic block diagram showing the configuration of the air system forward model 21. The air system forward model 21 includes a throttle opening phase advance section 21a, an air amount calculation section 21b, a pressure conversion section 21
c, an intake negative pressure calculating unit 21d, a volume efficiency estimating unit 21e, and an engine speed phase lead unit 21f.

(Regarding each phase advance section 21a and 21f) The phase advance section 21a for throttle opening and the phase advance section 21f for engine speed are provided by the fuel system forward model 2
2, the phase of the throttle opening α and the phase of the engine speed n that are input are advanced by the removed dead time (that is, the time from when the injected fuel is injected from the fuel injection device 4 to when it enters the cylinder 5). . Specifically, each of the phase advance units 21a and 21f includes a neural network in which a change pattern of the engine speed or the throttle opening with respect to time is previously learned. The phase is advanced by obtaining a future value of the engine speed or the throttle opening based on the engine speed or the throttle opening at. As described above, in the air system forward model 21, the phases of the throttle opening and the engine speed are advanced by the dead time, so that the phases of both the fuel system forward model 22 and the air system forward model 21 are advanced by the dead time. In other words, the phase difference between the estimated fuel amount Fv and the estimated air amount Av is eliminated by removing the dead time in the fuel system forward model 22,
The estimated air-fuel ratio calculator 23 can estimate an appropriate estimated air-fuel ratio. Further, for example, in the case of an in-cylinder injection type engine in which there is no dead time until the injected fuel enters the cylinder from the fuel injection device, or in a case where the dead time is so small as to be negligible, the injected fuel is When the behavior is modeled, there is no need to provide a phase delay portion for dead time from the beginning, so that there is no need to provide each phase lead portion 21a and 21f in the air system forward model 21. The method of advancing each phase is not limited to a method using a neural network, but may be any method, for example, a least square method or the like.

The calculation units 21b and 21d for the air amount Av and the intake negative pressure Pman perform modeling using hydrodynamic equations (1) and (2). Here, Ct is the flow rate count at the throttle, D is the diameter of the throttle, Pamb is the atmospheric pressure, k is the specific heat of air, Tam
b is the atmospheric temperature, R is the gas constant, Mao is the correction coefficient, Tma
n is the intake pipe temperature, V is the intake pipe volume, β1 is a count that depends on the throttle opening, and β2 is a count that depends on the intake pipe pressure. In addition, since it is difficult to model the volume efficiency η using mathematical formulas, the volume efficiency estimating unit 21e has learned the relationship between the engine speed signal n and the throttle opening α and the volume efficiency η in advance by using a fuzzy neural network ( Or, modeling is performed by a neural network, CMAC, or the like. still,
The output from the volumetric efficiency estimator 21e is corrected by the feedback correction signal FBa from the feedback controller 30 when the control device 10 is in the feedback correction mode, and the volumetric efficiency estimator 21e calculates the corrected volumetric efficiency η. It is configured to be able to learn as learning data.

The target air-fuel ratio calculator 30 receives the throttle opening α and the engine speed n and determines the optimum target air-fuel ratio at each time based on the information. And outputs it to the model base control unit 20.

Next, a feedback correction mode using the feedback control unit 60 and the feedback gain calculation unit 70 will be described. As shown in FIG. 6 (a), when the operating state of the engine changes by a predetermined amount or more, for example, when the throttle opening changes by a predetermined change rate or more, as shown in FIG. Switch to mode. In the feedback correction mode, O2 feedback control is performed based on the output signal E of the oxygen sensor 15 while performing feedforward control in which the target value is kept constant by the model base control unit 20. This is a mode for acquiring learning data for correcting a deviation between the forward model and the actual engine. During this mode, the target air-fuel ratio calculator 30 maintains the target air-fuel ratio Ep at the stoichiometric air-fuel ratio. Specifically, the feedback control unit 60 provided information on the actual air-fuel ratio of the engine 1 controlled by the feedforward control logic to the exhaust pipe 6 using the stoichiometric air-fuel ratio as the target value Ep by the model-based control unit 20. Feedback as the output signal E of the oxygen sensor 15
When the output signal is "1", that is, when the air-fuel ratio is rich, the fuel injection amount is reduced. When the output signal is "0", that is, when the air-fuel ratio is lean, Is a model-based control unit 20 for increasing the fuel injection amount.
Feedback correction signal F for correcting the output of the forward model
Ba is determined and output. Feedback control unit 6
0, the feedback correction signal FBa is, specifically, the air system forward model 2 of the model base controller 20.
1 to correct the volumetric efficiency η output from the volumetric efficiency estimating unit 21e, which is input to the air system forward model 21 as shown in FIG.
It is added to the output from 1e as a correction value. This feedback correction mode is performed until the teacher data is obtained such that the deviation between the forward model of the engine and the actual engine 1 in the model base control unit 20 is within an allowable range, that is, the output of the feedback control unit 60. FBa
(Or the output Mfn of the model-based control unit 20) periodically starts to oscillate between rich and lean across the stoichiometric air-fuel ratio, and thereafter, the control device 10 is switched to the normal control mode (FIG. 6 ( a)). The air system forward model 21 acquires the corrected volumetric efficiency η obtained in the feedback correction mode as learning data, and performs learning based on the learning data. As a result, after the learning, the deviation between the forward model of the engine and the actual engine is within an allowable range.

(Regarding Feedback Gain Calculator 70) During the feedback correction mode, the feedback gain of the feedback controller 60 is determined by the feedback gain calculator 70. FIG. 7 is a schematic block diagram of the feedback gain calculator 70. As shown in the drawing, the feedback gain calculator 70 includes a basic feedback gain calculator 71 and a feedback gain limiter 72.

(Basic Feedback Gain Calculating Unit) The basic feedback gain calculating unit 71 determines the engine speed n and the throttle opening α, and the feedback gain in a range that does not affect the operating characteristics of the engine (ie, during the O2 feedback. Of the engine speed n and the throttle opening α are input, and affect the operating characteristics of the engine under these conditions. Is obtained in a range that does not affect the above, and this is output as the basic feedback gain gn.

(Regarding Feedback Gain Limiting Section)
The feedback gain limiting section 72 includes a fluctuation allowable value determining section 72a, a rotation fluctuation detecting section 72b, a comparing section 72c, and a correction value calculating section 72d. The degree of influence on the driver's feeling is determined based on the torque fluctuation, which is a factor that easily affects the driver's feeling, that is, the rotation fluctuation of the engine, and the fluctuation of the air-fuel ratio during the feedback correction mode is determined. The basic feedback gain gn is corrected so as not to give an unpleasant feeling to the driver. Hereinafter, specific processing of each unit of the feedback gain limiting unit 72 will be described. As shown in FIG. 9, the rotation fluctuation detecting unit 72b includes an angular velocity detecting unit, an angular acceleration detecting unit, an angular acceleration average value calculating unit, and a cumulative deviation adding unit. The obtained crank angle signal r at two predetermined points when the engine 1 is in the expansion stroke is input as feedback information, and based on the crank angle signal r, the angular velocity v between the two crank angles at each cycle is determined for each cycle.
Is further calculated by the angular acceleration detector from the angular velocities (v1 and v2) between the two crank angles.
c) is calculated. Each time the calculation of the angular acceleration is repeated, that is, in each cycle, the average value of the angular acceleration (acc_ave) is obtained by the average angular acceleration calculation unit, and the angular acceleration (acc) and the average angular acceleration (acc_ave) at that time are obtained. The absolute value of the difference with the angular acceleration variation value (f1) is used as the angular acceleration variation value (f1), and the angular acceleration variation value (f1) is cumulatively added one after another as the combustion deterioration index (pnt) by the deviation accumulator. The combustion deterioration index (p) obtained by repeating the above process for 100 cycles
nt) is output as rotation fluctuation. On the other hand, the permissible fluctuation value determination unit 72a obtains a permissible rotational fluctuation value (lim) corresponding to the engine speed and the throttle opening degree of the engine 1 that does not give an unpleasant feeling to the driver through experiments or the like in advance. The engine speed signal n and the throttle opening signal α are input, and an allowable value (lim) of rotation fluctuation at that time is output. The comparison unit 72c compares the actual rotation fluctuation (pnt) obtained from the rotation fluctuation detection unit 72b with the fluctuation allowable value (lim) obtained from the fluctuation allowable value determination unit 72a, and calculates the correction value. Output to the unit 72d. Correction value calculator 7
2d indicates that the actual rotation fluctuation (pnt) is the fluctuation allowable value (li).
m), it is determined that the fluctuation of the air-fuel ratio during the O2 feedback control by the current feedback gain g gives an unpleasant feeling to the driver, and the rotation fluctuation (pnt) is allowed to fluctuate. Limiting correction signal L for reducing the skip amount and integral gain of basic feedback gain gn so as to fall within the range of value (lim).
a is determined and output. In addition, the actual target rotation fluctuation (p
nt) is smaller than the fluctuation allowable value (lim), it is determined that the fluctuation of the air-fuel ratio during the O2 feedback control by the current feedback gain g does not give an unpleasant feeling to the driver, and the rotation fluctuation ( The correction signal La for correcting the basic feedback gain gn is determined and output so that (pnt) becomes maximum within the range of the variation allowable value (lim). FIG. 10 is a flowchart showing a series of processes of the above-described fluctuation limiting unit 72.

The feedback gain calculating section 70 adds the output La from the feedback gain limiting section 72 to the output gn of the basic feedback gain calculating section 71 as described above.
Is added to the feedback control unit 60 as a feedback gain g, and the feedback control unit 60 performs feedback control using the feedback gain g to determine and output a feedback correction signal FBa. As a result, for example, in a driving state or a driving environment that easily affects the driver's feeling, for example, the skip amount is set to zero and the integral gain is reduced, so that the feedback control unit 60
11A, the feedback correction signal FBa does not fluctuate extremely as shown in FIG. 11A, and as a result, the fluctuation of the torque also decreases. In addition, for example, in a driving state or driving environment that does not affect the driver's feeling,
For example, since both the skip amount and the integral gain are relatively large, the feedback correction signal FBa from the feedback control unit 60 fluctuates relatively largely as shown in FIGS. 11B and 11C, and the O2 feedback control is performed. Responsiveness is increased, and the time for acquiring learning data can be shortened. In this way, by determining the feedback gain while determining the degree of influence of the change in the air-fuel ratio on the driver's feeling, the influence on the driver's feeling as in the conventional O2 feedback control can be completely considered. Compared with the control method in which the skip amount and the integral gain are always maintained at constant values shown in FIG. 11C, the influence on the driver's feeling without reducing the responsiveness of the O2 feedback control more than necessary is extremely large. It becomes possible to lower.

(Learning of Basic Feedback Gain Calculation Unit) The basic feedback gain calculation unit 7
The neural network that constitutes 1 performs the learning by using the corrected feedback gain g obtained by adding the correction signal La output from the feedback gain limiting unit 72 as learning data in accordance with the engine speed and the throttle opening at that time. Do. As a result, in the control after learning, the basic feedback gain calculation unit 71 is improved by following the time-dependent change of the engine and the like, and the responsiveness is increased within a range that does not give an unpleasant feeling to the driver. The basic feedback gain gn that can be output is output.
As described above, by feeding back the rotation fluctuation, which is a factor that easily affects the driver's feeling, and determining the feedback gain while correcting the rotation fluctuation so as to fall within the allowable value range, O2 is obtained.
The responsiveness can be improved within a range in which the fluctuation of the air-fuel ratio during the feedback control does not give an unpleasant feeling to the driver and the driver does not give an unpleasant feeling. By learning the subsequent feedback gain as learning data, it becomes possible to cope with a temporal change.

(Effects of the Embodiment) According to the above-described embodiment, the degree of influence on the driver's feeling is determined by using the rotation fluctuation, and the feedback gain is limited based on the determination result to reduce the air-fuel ratio. Since the fluctuation is controlled, it is possible to maintain the air-fuel ratio at an optimum value by performing O2 feedback control by changing the air-fuel ratio without giving an unpleasant feeling to the driver. . Further, in the present embodiment, the O2 feedback control is performed by the feedback control unit 60 only when learning data is acquired, if necessary, while performing the feedforward control by the model-based control unit 20.
Unlike the feedback control, it is not necessary to constantly change the air-fuel ratio, and the time during which torque fluctuation occurs due to the O2 feedback control can be minimized.

(Another application example) In the embodiment described above,
During the normal control mode, the feedforward control is executed by the model base control unit 20 using the forward model and the inverse model of the engine. During the feedback correction mode, the feedback control unit 60 and the feedback control unit 60 are used in addition to the feedforward control. Although the configuration is such that the O2 feedback control by the gain calculation unit 70 is executed, the control logic for executing the feedforward control is not limited to the present embodiment. For example, as shown in FIG. May be configured. In this case, the map control unit 110 is configured by a map that can be learned such as a CMAC, or is configured by a normal map and a learnable correction unit that can correct the output from the map. The unit 130 operates only when the control device enters the feedback correction mode, and outputs a feedback correction signal FBa for correcting the basic operation amount Mfn output from the map control unit 110 according to the output of the oxygen sensor. In the feedback correction mode, as in the embodiment described with reference to FIGS. 1 to 11, teacher data is acquired such that the deviation between the map data in the map control unit 110 and the actual engine 1 is within an allowable range. Until the teacher data is acquired. The map control unit 110 learns using the corrected operation amount Mf obtained in the feedback correction mode as learning data, and outputs an appropriate operation amount according to the driving state after learning. The feedback gain calculation unit 140 also determines the degree of influence of the fluctuation of the air-fuel ratio on the driver's feeling during the feedback correction mode, as in the embodiment described with reference to FIGS. The feedback gain g of the feedback control unit 60 is changed within a range where no e-ring is given.

Further, in the present embodiment, the O2 feedback control is partially performed in combination with the feedforward control. However, the feedback control logic using the air-fuel ratio sensor is not limited to the present embodiment. As shown in FIG. 13, for example, at the same time as determining the basic fuel injection amount based on the engine operation information such as the engine speed and the throttle opening, the correction coefficient calculation unit converts the current operation information from the operation information to the respective operation information. A correction coefficient is calculated so as to be suitable, the basic fuel injection amount is multiplied by the correction coefficient, and an oxygen sensor is provided in an exhaust pipe of the engine,
A feedback gain calculating unit is added to a so-called conventional O2 feedback control logic in which the output of the oxygen sensor is fed back and the O2 feedback control unit determines and outputs a correction signal for further correcting the corrected basic fuel injection amount. May be provided, and the feedback gain may be changed so that the fluctuation of the air-fuel ratio does not give the driver an unpleasant feeling. Further, in the present embodiment, an example in which the engine control system is applied to a four-stroke engine is described. However, the type of an engine to which the engine control system according to the present invention is applied is not limited to this embodiment. For example, it goes without saying that the present invention can be applied to any type of engine such as a two-cycle engine and a direct injection engine.
Further, in the present embodiment, the O2 feedback control is executed by changing the feedback gain so that the fluctuation of the air-fuel ratio does not give an unpleasant feeling to the driver, but the fluctuation of the air-fuel ratio is limited. The factor is not limited to the present embodiment, and the ON / OF of the oxygen sensor is
An F period may be used. In this case, ON / OFF of the oxygen sensor
The longer the OFF cycle, the smaller the fluctuation of the air-fuel ratio and the smaller the influence on the driver's feeling. Therefore, for example, the influence on the driver's feeling based on the rotation fluctuation as in this embodiment. When judging the degree, if the control is performed so as to shorten the cycle within a range in which the rotation fluctuation does not exceed the range of the fluctuation allowable value, unpleasant feeling is given to the driver without reducing the responsiveness more than necessary. O2 feedback control can be executed so as not to occur. Furthermore, in the present embodiment, the influence of the change in the target value on the driver's feeling is determined based on the engine rotation fluctuation, but the factor for determining the influence is not limited to the present embodiment. Without limitation, any factor may be used as long as it can judge the driver's feeling. For example, as described in Japanese Patent Application No. 7-306264, the driver's equipment such as a helmet and gloves is used. A sensor or the like that detects the driver's own physiological conditions such as heart rate, body temperature, sweating state, pulse, etc. is provided at the part that comes into contact with the driver, such as the accelerator or the like in the vehicle, And the driver's feeling may be determined directly from the driver's physiological state, or the driver's feeling may be determined from the operating state of the vehicle or engine other than the rotation fluctuation. It may be configured to determine a grayed. Further, in the present embodiment, both the skip amount and the integral gain are determined by the feedback gain calculating unit. However, the present invention is not limited to this embodiment, and one of the skip amount and the integral gain is changed. You may.

[0021]

According to the engine control system of the present invention described above, the air-fuel ratio is fed back using the air-fuel ratio sensor so that the output of the air-fuel ratio sensor periodically repeats ON and OFF. In an engine control system that performs feedback control to maintain the fluctuation of the air-fuel ratio, the degree of influence of the fluctuation of the air-fuel ratio on the driver's feeling is determined, and the feedback gain and the ON / OFF of the air-fuel ratio sensor are determined based on the result. Since the cycle is changed, it is possible to perform the feedback control using the air-fuel ratio sensor without lowering the responsiveness more than necessary and without giving the driver an unpleasant feeling.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a relationship between an engine 1 and a control device 10 capable of executing an engine control method according to the present invention.

FIG. 2 is a schematic block diagram illustrating a configuration of a control device 10.

FIG. 3 is a schematic block diagram showing a configuration of a model base control unit 20 in FIG.

FIG. 4 is a schematic block diagram showing a configuration of a fuel system forward model 22.

FIG. 5 is a schematic block diagram showing a configuration of an air system forward model 21.

FIG. 6A is a diagram showing a relationship between a feedback correction signal in a control device 10 and engine torque fluctuation, and FIG. 6B is a diagram showing a feedback correction signal and engine torque in a conventional feedback control using an oxygen sensor. It is a figure showing the relation with fluctuation.

FIG. 7 is a schematic block diagram of a feedback gain calculation unit 70.

FIG. 8 is a schematic configuration diagram of a neural network constituting the basic feedback gain calculation unit 71.

FIG. 9 is a schematic block diagram illustrating a configuration of a rotation fluctuation detection unit 72b.

FIG. 10 is a flowchart showing a series of processes of a variation limiting unit 72.

FIGS. 11A to 11C are diagrams illustrating a relationship between a feedback correction signal and a torque variation with respect to an output value of an oxygen sensor and a determination value of an ECU.

FIG. 12 is a schematic diagram showing a relationship between an engine 1 and a control device using a map control logic capable of executing an engine control method according to the present invention.

FIG. 13 is a schematic block diagram showing an example in which an engine control method according to the present invention is applied to a conventional O2 feedback control logic.

FIG. 14 is a schematic block diagram of a conventional O2 feedback control logic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Intake pipe 3 Air cleaner 4 Fuel injection device 5 Cylinder 6 Exhaust pipe 7 Crankcase 8 Throttle valve 10 Control device 12 Throttle opening detection means 13 Crank angle detection means 14 Intake pipe wall temperature detection means 15 Oxygen sensor 20 Model base control Unit 21 Air system forward model 21a Throttle opening degree phase advance unit 21b Air amount operation unit 21c Pressure conversion unit 21d Intake negative pressure operation unit 21e Volume efficiency estimation unit 21f Engine speed phase advance unit 22 Fuel system forward model 22a Non-adhesion Fuel calculation unit 22b Adhered fuel calculation unit 22c Primary delay unit 22d Primary delay unit 22e Fuel adhesion rate estimation unit 22f Evaporation time constant estimation unit 23 Estimated air-fuel ratio calculation unit 24 Basic operation amount calculation unit 30 Target air-fuel ratio calculation unit 40 Engine speed Operation unit 50 Conversion unit 60 Feedback system Controller 70 feedback gain calculator 71 basic feedback gain calculator 72 feedback gain limiter 72a variation allowable value determiner 72b rotation fluctuation detector 72c comparator 72d correction value calculator α throttle opening r crank angle tw intake pipe wall temperature n Engine speed Mf Operation amount Mfn Basic operation amount E Detection signal regarding actual air-fuel ratio Ep Target air-fuel ratio Ev Estimated air-fuel ratio Av Estimated air amount Fv Estimated fuel amount FBa Feedback correction signal g Feedback gain

Claims (12)

[Claims] 1. An engine control method for performing feedback control for feeding back an exhaust air-fuel ratio using an air-fuel ratio sensor and maintaining the air-fuel ratio in a fluctuating state such that the output of the air-fuel ratio sensor periodically repeats ON and OFF. An engine control method according to any one of claims 1 to 3, wherein a degree of influence of a change in air-fuel ratio on a driver's feeling is determined, and a feedback gain is changed based on the result. 2. The engine control method according to claim 1, wherein the feedback gain is determined by feedforward control with a learning function. 3. The feedforward control with learning function is performed by a neural network, a fuzzy neural network,
The engine control method according to claim 2, wherein the control is performed using at least one of a CMAC and a map. 4. The engine control system according to claim 1, wherein the feedback gain is determined so that a stepwise change in the air-fuel ratio is reduced or eliminated. . 5. The engine control method according to claim 1, wherein the degree of influence of the change in the air-fuel ratio on the driver's feeling is determined from the torque change. 6. The engine control system according to claim 5, wherein the torque fluctuation is detected by using a rotation fluctuation of an engine. 7. An engine control method for performing feedback control of feeding back the exhaust air-fuel ratio using an air-fuel ratio sensor and maintaining the air-fuel ratio in a state where the output of the air-fuel ratio sensor periodically repeats ON and OFF. In the above, the degree of influence of the change in the air-fuel ratio on the driver's feeling is determined, and based on the result, the ON / OFF of the air-fuel ratio sensor is determined.
An engine control method characterized by changing the cycle of the FF. 8. The engine control method according to claim 7, wherein the cycle is determined by feedforward control with a learning function. 9. The feedforward control with learning function is performed by a neural network, a fuzzy neural network,
The engine control method according to claim 8, wherein the control is performed using at least one of a CMAC and a map. 10. The engine control system according to claim 7, wherein the cycle is determined so that a stepwise change in the air-fuel ratio is reduced or eliminated. 11. The engine control method according to claim 7, wherein the degree of influence of the change in the air-fuel ratio on the driver's feeling is determined from the torque change. 12. The engine control method according to claim 11, wherein the torque fluctuation is detected by using a rotation fluctuation of an engine.