JP2785373B2 - Air-fuel ratio control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device, and more particularly to an air-fuel ratio that receives a detection signal from an exhaust sensor and performs feedback control of the air-fuel ratio of an internal combustion engine based on the detection signal. It relates to a control device.

[Background Art] An internal combustion engine for a vehicle has extremely large fluctuations in the vehicle running speed, that is, the engine rotation speed and the load, and in various operating states in which these two variable elements are combined, low fuel consumption, low harmful exhaust gas, etc. Performance is required. Therefore, it is necessary to properly maintain the air-fuel ratio in various operating states.

An air-fuel ratio control device is disclosed in Japanese Patent Application Laid-Open No. 63-154833. The air-fuel ratio control device for an internal combustion engine disclosed in this publication provides an idle engine according to the cumulative driving time (or running time) of the engine stored in the cumulative engine driving time storage means and the idle load by the idle load detecting means. The feedback control constant of the fuel ratio is changed, and the air-fuel ratio is adjusted by the air-fuel ratio adjusting means according to the air-fuel ratio correction amount,
Changes in the initial characteristics of the air-fuel ratio sensor are reliably compensated to prevent deterioration of exhaust emissions.

Further, there is one disclosed in JP-A-63-189645. Air-fuel ratio feedback control method for an internal combustion engine disclosed in this publication, the output characteristic of the O ₂ sensor is in view for a change over time, until the exhaust concentration detection value becomes the lean side minimum value from the rich side maxima The ratio between the first time and the second time from the lean minimum value to the rich maximum value is determined, the reference value is changed according to this ratio, and the air-fuel ratio feedback control is performed. The air-fuel ratio of the air-fuel mixture is modified accordingly to achieve the target air-fuel ratio, and the engine operating performance, fuel efficiency, and exhaust gas characteristics are improved.

[Problems to be Solved by the Invention] In the conventional air-fuel ratio control device, as shown in FIG. 5, the air-fuel ratio control device is provided to supply air to the internal combustion engine 202, and the fuel injection valve 210 and the air are supplied to the intake system. A pressure sensor 248 for detecting pressure is provided, and a catalytic converter 230 composed of a three-way catalyst and a zirconia-type O ₂ sensor 254 as an exhaust sensor are provided in the exhaust system.

Further, a control unit (ECU) 258 for inputting detection signals from the pressure sensor 248 and the O ₂ sensor 254 is provided, and the fuel injection valve 210 is connected to the control unit 258 so as to control the fuel amount by the control signal. Provided.

Then, according to the output from the O ₂ sensor 254, the sixth
As shown in FIGS. 7A and 7B, the O ₂ feedback coefficient is determined, and the air-fuel ratio is controlled by adjusting the fuel injection time of the fuel injection valve (see the broken line in FIG. 7).

That, O ₂ feedback coefficient, the output is inverted from the O ₂ sensor 254, for example, when the maximum output value V _H is minimized output value V _L, proportional amount is added at the beginning, then the signal is inverted, for example, minimum integrated amount is added from the output value V _L until the maximum output value V _H.

An electronic fuel injection system having a control unit comprising a conventional microcomputer, generally, the injection time of the fuel injection valve, the basic injection time × (1 + O ₂ feedback correction + K1 + K2
…) K1, K2: It can be calculated by the correction coefficient.

However, the lead wire of the O ₂ sensor is only on the + (plus) side, and the ground on the − (minus) side is the O ₂ sensor body.

For this reason, the O ₂ sensor mounting position is restricted by the compactness of the internal combustion engine layout, the earth potential flowing through the internal combustion engine body is increased due to the progress of electrification of the internal combustion engine control, and the O ₂ sensor output signal due to the prolonged service life of the vehicle Various factors such as an increase in contact resistance at the take-out site cause a potential difference.

Then, when a potential difference occurs between the ground of the control unit and the O ₂ sensor take-out site, the output of the O ₂ sensor increases by ΔV as shown by the broken line in FIG. 7, and when the air-fuel ratio is in a rich state, the control unit determined, the air-fuel ratio becomes possible to feedback controlled to lean, will then lean more than necessary air will increase the emissions of nO _X, there is a shaking disadvantages not play a exhaust gas cleaning.

Further, for example, aging progresses, by the potential difference becomes even larger, will then feedback control to further lean air-fuel ratio is always appropriate in response to aging of the contact resistance of the part take-out O ₂ sensor output signal The air-fuel ratio cannot be set to a high value, which is disadvantageous in practical use.

[Object of the Invention] Accordingly, an object of the present invention is to eliminate the above-mentioned inconvenience by storing in advance a basic output value of an exhaust sensor of an air-fuel ratio control device and an initial potential difference with respect to this basic output value, and at the time of a predetermined engine operating state. By providing a control unit that calculates the aging potential difference with respect to the initial potential difference due to aging, stores this aging potential difference with a learning function, corrects the basic output value with the aging potential difference, and feedback controls the air-fuel ratio to an appropriate state, the learning function It can respond to aging and can always control the air-fuel ratio to an appropriate value by correcting the potential difference.
Exhaust gas can be cleaned and the configuration is not complicated,
An object of the present invention is to realize an air-fuel ratio control device that can reduce costs.

[Means for Solving the Problems] In order to achieve this object, the present invention provides an air-fuel ratio control device for feedback-controlling the air-fuel ratio of an internal combustion engine based on a detection signal from an exhaust sensor. An exhaust sensor for detection is provided, a basic output value of the exhaust sensor and an initial potential difference with respect to the basic output value are stored in advance, and an aged potential difference with respect to the initial potential difference due to aging is calculated in a predetermined engine operating state, and the aged potential difference is learned. And a control unit for correcting the basic output value based on the aged potential difference and performing feedback control of the air-fuel ratio to an appropriate state.

[Operation] With the configuration described above, the basic output value of the exhaust sensor of the air-fuel ratio control device and the initial potential difference with respect to this basic output value are stored in advance, and the aging potential difference with respect to the initial potential difference due to aging during a predetermined engine operation state is calculated. Calculate and store the aging potential difference by the learning function, correct the basic output value by the aging potential difference, feedback-control the air-fuel ratio to the appropriate state by the control unit, make the learning function correspond to aging, correct the potential difference The air-fuel ratio is constantly controlled to an appropriate value to purify exhaust gas and reduce costs.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

1 to 4 show an embodiment of the present invention. 2, 2 is an internal combustion engine, 4 is an air cleaner, 6 is a throttle body, 8 is a body intake passage, 10 is a fuel injection valve, 12 is a throttle valve, 14 is an intake manifold, 16 is a manifold intake passage, and 18 is intake air. Port, 20 is combustion chamber, 22
Is an exhaust manifold, 24 is a manifold exhaust passage, 26 is an exhaust pipe, 28 is a pipe exhaust passage, and 30 is a catalytic converter.

Air-fuel ratio control device, for example, fuel injection type air-fuel ratio control device
The fuel injection valve 10 constituting the fuel injection valve 32 includes a throttle valve 12
It is arranged in the body intake passage 8 on the upstream side. The fuel in the fuel tank 34 is supplied to the fuel injection valve 10.
That is, the fuel in the fuel tank 34 is filtered by the fuel filter 40 via the fuel supply passage 38 by the fuel pump 36 and is supplied to the fuel injection valve 20.

The fuel supply passage 38 is provided with a fuel pressure regulator 42 for regulating the fuel pressure acting on the fuel injection valve 10 at a constant level. The fuel pressure regulator 42 is operated by an intake pipe pressure from a fuel pressure passage 44 that opens into the manifold intake passage 16 downstream of the air cleaner 4.

A pressure sensor via a detection pressure passage 46 for detecting an intake pipe negative pressure which is an intake pipe pressure in the manifold intake passage 16
48 are provided. The intake manifold 14 is provided with a water temperature sensor 52 for detecting a temperature of a cooling water in a cooling water passage 50 formed in the intake manifold 14, and an exhaust manifold 22 for detecting an oxygen concentration in exhaust gas. sensor serving O ₂ sensor 54 is attached.

Further, the throttle valve 12 has a throttle opening sensor for detecting the throttle opening of the throttle valve 12.
56 are provided.

The fuel injection valve 10, fuel pump 36, the pressure sensor 48, the water temperature to the sensor 52, O ₂ sensor 54, a throttle opening sensor 56 is communicated to the control unit 58.

The control unit 58 stores in advance the basic output value of the O ₂ sensor 54 and the initial potential difference with respect to this basic output value, calculates the potential difference with respect to the initial potential difference due to aging during a predetermined engine operating state, and Is stored by a learning function, and the basic output value is corrected by an aged potential difference, and the air-fuel ratio is feedback-controlled to an appropriate state.

That is, the control unit 58 determines the basic output value of the O ₂ sensor 54 and a factor that does not undergo aging, that is, the internal combustion engine 2
The initial potential DELV of increase in the ground potential through the internal combustion engine body by electroporation of progression of constraints and the internal combustion engine control of the O ₂ sensor mounting position due to compact layout of
With stores in advance 0, calculates factors, i.e. the age difference DELV1 the increase in the contact resistance of the output signal exit site of the O ₂ sensor 54 according to the service life prolonged automobile affected by aging.

The aged potential difference DELV1 is calculated by the following method.

That is, a predetermined engine operating state, for example, the internal combustion engine 2
When the vehicle is shifted from the running state after the complete warm-up to the idle state, that is, as shown in FIG. 3 (b), the state is shifted from the state in which the O ₂ feedback control is performed to the idle operation state, and n1 times are skipped ( After skipping), the integration constant is added n2 times from the time when the output signal from the O ₂ sensor 54 changes from the rich side to the lean side, and the O ₂ feedback correction constant is fixed for T _msec. O ₂ while fixed
The output of the sensor 54, that is, the minimum output value _VL is measured.

Said one output of the O ₂ sensor 54 is the maximum output value V _H or minimum output value V _L, it is determined by the threshold level V _T shown in FIG. 3 (a), proportional portion P is minimum output value V _L
From maximum output value _VH or maximum output value _VH to minimum output value
When it changes to _VL , it is added only once, and then the O ₂ sensor 54
Integrated amount I output until crossing the threshold level V _T is what is added in a predetermined cycle. A case where the proportional component P is added is called a skip.

The minimum output value V _{L is, V L = V 0T + (} DELV0 + DELV1) V 0T: have a relationship between the basic output value, the output value V of the standard O ₂ sensor 54 can be regarded as basic output value V _0T by previously storing the _LS and the initial potential difference DELV0, DELV1 = V _L - a (V _LS + DELV0).

The operation of obtaining the aging potential difference DELV1 is performed only once by turning on an ignition switch (not shown), and the obtained aging potential difference DELV1 is stored by the learning function of the control unit 58.

The control unit 58 has an ignition coil 60 for detecting an ignition signal, an engine speed, and the like, a battery 62, one end opening to the manifold intake passage 16 downstream of the throttle valve 12, and the other end opening to the air cleaner 4. A negative pressure switching valve 66 provided in the middle of the bypass passage 64 communicates.

Reference numeral 68 denotes a blow-by gas passage, and reference numeral 70 denotes a PCV valve.

Further, as shown in FIG. 4, the control unit 58 includes an A / D converter 72, an input interface circuit 74, a first memory
76, a second memory 78, a central processing unit 80, and an interface circuit 82.

The A / D converter 72, the output signal from the O ₂ sensor 54 and other sensors and converts A / D.

The first memory 76 is a read only memory (RO
It consists M), storing in advance an output value V _LS and early potential DELV0 standard O ₂ sensor 54 can be regarded as basic output value V _0T.

Further, the second memory 78 is composed of a random access memory (RAM), and stores the aged potential difference DELV1 by a learning function.

The central processing unit 80 includes the A / D converter 72 and the first,
The arithmetic processing is performed based on the signals from the second memories 76 and 78.

Further, the output interface circuit 82 receives an output signal from the central processing unit 80 and outputs a control signal to the fuel injector 10.

Next, the operation will be described with reference to the control flowchart of the air-fuel ratio control device of FIG.

The internal combustion engine 2 is started, and the program of the control flowchart is started (100).

Then, the O ₂ sensor 54 performs the determination (102) whether or not inert, YES in the case (which is active), the cooling water temperature is the predetermined temperature, that is T0 ° C. <coolant temperature <T1 of ° C. The process proceeds to determination (104) as to whether or not it is within the range, and determination (102) is NO.
(Inactive), the determination is repeated until the determination (102) becomes YES.

If the determination (104) is YES, the warm-up state is confirmed, and it is determined whether or not the idle switch is ON (10).
The process proceeds to 6), and in the case of NO, the determination is repeated until the determination (104) becomes YES.

If the above determination (106) is YES, it is confirmed that the throttle is fully closed, and the process proceeds to determination (108) as to whether or not the vehicle speed is, for example, Akm / h. The determination is repeated until the determination (106) becomes YES.

If the determination (108) is YES, it is confirmed not decelerating, O ₂ feedback correction constant is shifted to skip (Skip) was determined whether (110), this in the case of NO The determination is repeated until the determination (108) becomes YES.

If the determination (110) is YES, 1 is added to the number of skips NSKIP to obtain a new number of skips NSKIP (112),
The process proceeds to a judgment (114) as to whether or not the skip count NSKIP is larger than the correction coefficient K1. If the judgment (110) is NO, the process is repeated until the judgment (110) becomes YES.

If the determination (114) is YES, the process proceeds to the determination (116) as to whether or not the constant of the proportional component P is smaller than 0, and NO
In the case of, the process moves to the judgment (110).

The determining (116) is outputted directivity of the direction O ₂ sensor 54 for enriching the air-fuel ratio in If NO, repeated until the determination (116) is YES, in the case of YES is, O ₂ feedback correction constant plus K2% constant of the integral component I which is set to an appropriate value (118), input to the control unit 58 an output from the O ₂ sensor 54 as the minimum output value V _L (120).

The minimum output value V _L, wherein DELV1 = V _L - substituted into (V _LS + DELV0), calculates the aging potential DELV1 (122).

Thereafter, the program of the control flowchart shifts to return (124), and the program ends.

Thus, to calculate the age difference DELV1 by the control unit 58 stores the age difference DELV1 by the learning function of the control unit 58, an increase in contact resistance output signal taken out of the site of the O ₂ sensor 54 according to automobile service life prolonged The initial potential difference DELV0 can be corrected, and the air-fuel ratio can always be adjusted to an appropriate value, that is, the stoichiometric air-fuel ratio (14.7). And is practically advantageous.

In addition, by being able to respond only by changing the program in the control unit 58, the configuration is not complicated,
It is easy to manufacture, the cost can be reduced, and it is economically advantageous.

[Effects of the Invention] As described above in detail, according to the present invention, the basic output value of the exhaust sensor of the air-fuel ratio control device and the initial potential difference with respect to this basic output value are stored in advance, and at the time of a predetermined engine operating state, the aging change occurs. The control unit calculates the aged potential difference with respect to the initial potential difference, stores this aged potential difference by a learning function, corrects the basic output value based on the aged potential difference, and performs feedback control of the air-fuel ratio to an appropriate state. In addition, by storing the aging potential difference by the learning function of the control unit, it is possible to respond to aging such as an increase in the contact resistance of the output signal extraction portion of the exhaust sensor,
The initial potential difference can be corrected, and the air-fuel ratio can always be controlled to an appropriate value, which can reliably purify the exhaust gas, which is practically advantageous. In addition, since the configuration can be dealt with only by changing the program in the control unit, the configuration is not complicated, the manufacturing is easy, the cost can be reduced, and the cost is low as compared with the conventional one.

[Brief description of the drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a flowchart for controlling an air-fuel ratio control device of an internal combustion engine, FIG. 2 is a schematic diagram of an air-fuel ratio control device, and FIGS. b),
(C) is a time chart of the air-fuel ratio control device, and FIG. 4 is a block diagram of the control unit. 5 to 7 show a prior art of the present invention, FIG. 5 is a schematic diagram of an air-fuel ratio control device, FIGS. 6 (a) and (b) are time chart diagrams of the air-fuel ratio control device, and FIG. FIG. 4 is a diagram illustrating output characteristics of an O ₂ sensor. In the figure, 2 is an internal combustion engine, 4 is an air cleaner, 8 is a body intake passage, 10 is a fuel injection valve, 12 is a throttle valve, 16 is a manifold intake passage, 24 is a manifold exhaust passage, 28 is a pipe exhaust passage, and 34 is fuel tank, the pressure sensor 48, water temperature sensor 52, the O ₂ sensor 54, 56 is a throttle opening sensor, 58 control unit, 72 A / D converter, 74 an input interface circuit, the 76 first memory, 78 Is a second memory, 80 is a central processing unit, and 82 is an interface circuit.

Claims (1)

(57) [Claims] An air-fuel ratio control device for feedback-controlling an air-fuel ratio of an internal combustion engine based on a detection signal from an exhaust sensor is provided with an exhaust sensor for detecting an oxygen concentration in exhaust gas. An initial potential difference with respect to the basic output value is stored in advance, and an aged potential difference with respect to the initial potential difference due to aging is calculated in a predetermined engine operating state, the aged potential difference is stored by a learning function, and the basic output value is corrected by the aged potential difference to correct the air-fuel ratio. An air-fuel ratio control device, further comprising a control unit for performing feedback control of the air-fuel ratio to an appropriate state.