JP7706837B2 - Fuel injection amount correction system - Google Patents

Description

The present invention relates to correction control of the amount of fuel injected into the cylinders of an internal combustion engine mounted on a vehicle.

In general, a three-way catalyst is installed in the exhaust passage of an internal combustion engine to oxidize/reduce harmful substances HC, CO, and _NOx contained in gas exhausted from the cylinders to render them harmless (see, for example, the following patent document). This type of catalyst has the ability to store excess oxygen when lean air-fuel ratio gas flows in ( _O2 storage capacity). Then, when rich air-fuel ratio gas flows in, the stored oxygen is released. This allows the _NOx contained in lean air-fuel ratio gas to be appropriately reduced, and the HC and CO contained in rich air-fuel ratio gas to be appropriately oxidized.

However, in order to efficiently purify all of HC, CO, and _NOx , it is necessary to keep the air-fuel ratio of the gas within a certain range near the theoretical air-fuel ratio. For this purpose, it is common to install an air-fuel ratio sensor in the exhaust passage of the internal combustion engine and implement feedback control to make the air-fuel ratio detected by the sensor follow a required target value.

3 shows an example of air-fuel ratio feedback control in which an _O2 sensor is installed downstream of a catalyst in the exhaust passage as an air-fuel ratio sensor, and the amount of fuel injected into a cylinder is increased or decreased by referring to the output signal of the _O2 sensor. As is well known, the output characteristic of an O2 sensor shows a steep slope with a large rate of change in output voltage with respect to the air-fuel ratio in a certain range near the theoretical air-fuel ratio, and in a lean region where the air-fuel ratio is higher than that, the output voltage asymptotically approaches a lower saturation value, and in a rich region where the air-fuel ratio is lower than that, the output voltage asymptotically approaches a higher saturation value, drawing a so-called Z characteristic curve.

In this air-fuel ratio feedback control, the fuel injection amount is corrected using a value obtained by adding a correction amount according to the deviation between the output voltage of the _O2 sensor downstream of the catalyst and the target value to the base value. If the output voltage of the _O2 sensor is higher than the target value, that is, if the air-fuel ratio of the gas flowing out downstream of the catalyst is richer than the target air-fuel ratio, the above correction amount is gradually decreased. As a result, the fuel injection amount is further reduced.

On the other hand, if the output voltage of the _O2 sensor is lower than the target value, that is, if the air-fuel ratio of the gas flowing downstream of the catalyst is leaner than the target air-fuel ratio, the above correction amount is gradually increased, resulting in a further increase in the amount of fuel injected.

Fluctuations in the air-fuel ratio of the gas downstream of the catalyst indicate that most of the oxygen stored in the catalyst has been consumed, resulting in a shortage of oxygen, or that the catalyst has been stored close to its maximum oxygen storage capacity, resulting in an excess of oxygen. When there is a shortage of oxygen in the catalyst, it becomes difficult to oxidize HC and CO, and these are more likely to be discharged. When the catalyst is filled with oxygen, it becomes difficult to reduce _NOx , and _NOx is more likely to be discharged. Correcting the amount of fuel injection based on the air-fuel ratio of the gas downstream of the catalyst is very effective in suppressing the emission of harmful substances.

JP 2021-102933 A

When a driver takes his/her foot off the accelerator pedal while the vehicle is running and requests coasting or deceleration, a fuel cut is performed to temporarily halt fuel injection into the cylinders of the internal combustion engine. During the fuel cut, air containing a large amount of oxygen flows into the catalyst, and the oxygen is stored in the catalyst. Since fuel cuts occur frequently, _NOx emissions can become a problem at many times after the internal combustion engine has finished warming up.

The maximum oxygen storage capacity of a catalyst decreases with age. A deteriorated catalyst has a lower _NOx purification efficiency. In other words, there is a concern that the amount of _NOx emissions may increase.

Therefore, as shown in Fig. 3, in air-fuel ratio feedback control, there is a tendency to adjust the fuel injection amount so that the air-fuel ratio of the gas downstream of the catalyst is not obviously leaner than the target air-fuel ratio, but is rather richer than the target air-fuel ratio. In conventional systems, the base value in air-fuel ratio feedback control was set to a high value with a margin in advance in anticipation of aging deterioration of the catalyst (enough to satisfy the legal emission standards even after a long driving distance), and a larger amount of fuel was always injected as a measure to prevent an increase in _NOx emissions even if the catalyst deteriorates with age.

However, the above base value is always constant regardless of the degree of catalyst deterioration. Therefore, for new or undeteriorated catalysts with a large oxygen storage capacity, the amount of fuel injected may be excessive, resulting in reduced fuel economy or increased emissions of HC and CO. For the new catalyst shown in Figure 3 (I), the air-fuel ratio downstream of the catalyst is much richer than for the deteriorated catalyst shown in Figure 3 (II).

The present invention was developed with the above in mind, and aims to optimize air-fuel ratio feedback control based on the output signal of an air-fuel ratio sensor installed in the exhaust passage of an internal combustion engine.

In the present invention, a fuel injection amount correction system is configured that obtains a first index value indicating the distance a vehicle has traveled using an exhaust purification catalyst currently installed in the exhaust passage of the internal combustion engine, or the length of time the internal combustion engine has been operated in that state, obtains a second index value indicating the current degree of deterioration of the catalyst, which is a combination of the degree of deterioration of the catalyst when fuel is supplied to the cylinders of the internal combustion engine and burned while using the catalyst, and the degree of deterioration of the catalyst when a fuel cut is performed in which no fuel is supplied to the cylinders, and modifies the amount of fuel injected into the cylinders by referring to at least one of the first index value and the second index value.

More specifically, in a feedback control in which the fuel injection amount is increased or decreased according to the deviation between the output signal of an air-fuel ratio sensor installed in an exhaust passage of an internal combustion engine and its target value, the fuel injection amount is corrected using a base value to which a correction amount according to the deviation has been added, and the base value in the feedback control is updated so as to increase the fuel injection amount as the deterioration of the catalyst estimated by referring to the first index value and the second index value progresses, and the base value is kept low if the deterioration of the catalyst is not progressing.

In addition, data defining the relationship between the first index value and the second index value predicted at the time of the first index value is stored in advance in the memory, and the base value stored and held may be updated by referring to the first index value or the second index value , provided that the deviation between the current first index value converted into the second index value and the current second index value is smaller than a predetermined value.

The method for correcting the fuel injection amount according to the present invention involves obtaining a first index value indicating the distance a vehicle has been traveled using an exhaust purification catalyst currently installed in the exhaust passage of the internal combustion engine, or the length of time the internal combustion engine has been operated in that state, obtaining a second index value indicating the current degree of deterioration of the catalyst, which is a combination of the degree of deterioration of the catalyst when fuel is supplied to the cylinders of the internal combustion engine and burned while using the catalyst, and the degree of deterioration of the catalyst when a fuel cut is performed in which no fuel is supplied to the cylinders, and correcting the fuel injection amount for the cylinders by referring to at least one of the first index value and the second index value. More specifically, in a feedback control in which the fuel injection amount is increased or decreased according to the deviation between the output signal of an air-fuel ratio sensor installed in the exhaust passage and a target value thereof, the fuel injection amount is corrected using a base value to which a correction amount according to the deviation has been added, and the base value in the feedback control is updated so as to increase the fuel injection amount as the deterioration of the catalyst estimated by reference to the first index value or the second index value becomes more advanced, and the base value is kept low if the deterioration of the catalyst is not advanced.

The present invention makes it possible to optimize air-fuel ratio feedback control based on the output signal of an air-fuel ratio sensor installed in the exhaust passage of an internal combustion engine.

1 is a diagram showing a schematic configuration of an internal combustion engine and a control device according to an embodiment of the present invention; FIG. 4 is a timing chart illustrating the air-fuel ratio feedback control executed by the control device in the embodiment. FIG. 4 is a timing diagram illustrating the contents of conventional air-fuel ratio feedback control.

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overview of an internal combustion engine for a vehicle in this embodiment. The internal combustion engine in this embodiment is a spark-ignition four-stroke gasoline engine, and is equipped with multiple cylinders 1 (one of which is shown in FIG. 1). An injector 11 that injects fuel toward the intake port is provided near the intake port of each cylinder 1. In addition, an ignition plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The ignition plug 12 generates a spark discharge between a center electrode and a ground electrode when an induced voltage generated by an ignition coil is applied to the ignition coil. The ignition coil is integrally built into the coil case together with an igniter, which is a semiconductor switching element.

The intake passage 3 for supplying intake air takes in air from the outside and directs it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream on the intake passage 3.

An exhaust passage 4 for discharging exhaust gas leads exhaust gas generated by burning fuel in the cylinders 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4. Air-fuel ratio sensors 43, 44 for detecting the air-fuel ratio of gas flowing through the exhaust passage 4 are provided upstream and downstream of the catalyst 41 in the exhaust passage 4. The air-fuel ratio sensors 43, 44 may be _O2 sensors having nonlinear output characteristics with respect to the air-fuel ratio of gas, or may be linear A/F sensors having output characteristics proportional to the air-fuel ratio of gas. In this embodiment, both the air-fuel ratio sensor 43 upstream of the catalyst 41 and the air-fuel ratio sensor 44 downstream of the catalyst 41 are assumed to be _O2 sensors.

The exhaust gas recirculation device 2 includes an external EGR passage 21 that connects the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 to control the flow rate of EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

The ECU (Electronic Control Unit) 0, which is the control device for the internal combustion engine in this embodiment, is a microcomputer system having a processor, memory, an input interface, an output interface, etc. The ECU 0 may be configured by connecting multiple ECUs or controllers so that they can communicate with each other via an electric communication line such as a CAN (Controller Area Network).

The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed (or the rotation speed of the wheels), a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft, which is the output shaft of the internal combustion engine, and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal by the driver or the opening of the throttle valve 32 as the accelerator opening (in other words, the required engine load rate or engine torque), and an intake passage 3 ( In particular, the following signals are input: intake air temperature/intake pressure signal d output from a temperature/pressure sensor that detects the intake air temperature and intake pressure in the surge tank 33 or intake manifold 34; a cooling water temperature signal e output from a water temperature sensor that detects the cooling water temperature of the internal combustion engine; an air-fuel ratio signal f output from an air-fuel ratio sensor 43 that detects the air-fuel ratio of the gas upstream of the exhaust purification catalyst 41; an air-fuel ratio signal g output from an air-fuel ratio sensor 44 that detects the air-fuel ratio of the gas downstream of the catalyst 41; and an atmospheric pressure signal h output from an atmospheric pressure sensor that detects the atmospheric pressure.

The output interface of ECU0 outputs an ignition signal i to the igniter of the spark plug 12 of the internal combustion engine, a fuel injection signal j to the injector 11, an opening control signal k to the motor that drives the valve body of the throttle valve 32, an opening control signal l to the motor that drives the valve body of the EGR valve 23, etc.

The processor of ECU0 interprets and executes programs stored in memory in advance, and calculates operating parameters to control the operation of the internal combustion engine. ECU0 acquires various information a, b, c, d, e, f, g, and h required for operating control of the internal combustion engine and vehicle via the input interface, and determines operating parameters such as the required fuel injection amount (required to realize the theoretical air-fuel ratio or a target air-fuel ratio close to the theoretical air-fuel ratio) corresponding to the amount of air (fresh air) drawn into cylinder 1, the fuel injection timing (including the number of fuel injections per combustion), the fuel injection pressure, the ignition timing (including the number of ignitions per combustion), the required EGR rate (or the amount of EGR gas), and the like. ECU0 applies various control signals i, j, k, and l corresponding to the operating parameters via the output interface.

ECU0 feedback controls the air-fuel ratio of the mixture filled in cylinder 1, and therefore the air-fuel ratio of the exhaust gas discharged from cylinder 1. ECU0 first calculates the amount of fresh air filled in cylinder 1 from the intake pressure and intake temperature, engine speed, required EGR rate, etc., and determines the basic injection amount TP that corresponds to this.

Next, this basic injection amount TP is corrected by a feedback correction coefficient FAF that is determined according to the air-fuel ratio of the gas upstream and/or downstream of the catalyst 41 in the exhaust passage 4. In general, the feedback correction coefficient FAF is adjusted according to the deviation between the air-fuel ratio of the gas actually measured via the air-fuel ratio sensors 43, 44 and the target air-fuel ratio (normally the theoretical air-fuel ratio or its vicinity), and increases when the actual air-fuel ratio is leaner than the target air-fuel ratio, and decreases when the actual air-fuel ratio is richer than the target air-fuel ratio.

Then, the final fuel injection time T is calculated taking into consideration various correction coefficients K determined according to the state of the internal combustion engine, environmental conditions, and the invalid injection time TAUV of the injector 11. The fuel injection time T is calculated as follows:
T=TP×FAF×K+TAUV
The ECU 0 energizes the injector 11 with a signal j for the fuel injection time T, thereby opening the injector 11 and injecting fuel.

Feedback control that references the air-fuel ratio signals f, g upstream and/or downstream of the catalyst 41 is performed when all of the following conditions are met: a predetermined time has passed since the internal combustion engine was started cold, the engine's cooling water temperature is higher than a predetermined temperature (the internal combustion engine has already been warmed up, and the catalyst 41 and the air-fuel ratio sensors 43, 44 have also been warmed up and activated), fuel is not being cut off, power is not being boosted, the intake pressure is normal, etc.

Furthermore, when a predetermined fuel cut condition is met, ECU0 executes a fuel cut to temporarily interrupt the fuel supply to cylinder 1. When ECU0 determines that the fuel cut condition is met when at least the engine coolant temperature is higher than a predetermined temperature, the accelerator opening is equal to or lower than a threshold value close to 0, and the current engine speed is higher than the fuel cut permission speed, ECU0 stops fuel injection from injector 11.

If a specific fuel cut end condition is met after the fuel cut condition is met, the fuel cut is ended and fuel injection from the injector 11 is resumed. ECU0 determines that the fuel cut end condition is met when the accelerator opening exceeds a threshold value, the engine speed drops below the fuel cut return speed, etc.

The following describes in detail the air-fuel ratio feedback control implemented by ECU0 based on the output signal g of the air-fuel ratio sensor 44 downstream of the catalyst 41.

Figure 2 shows an example of the air-fuel ratio feedback control. In this air-fuel ratio feedback control, the ECU 0 calculates a value by adding (adding or multiplying) a correction amount according to the deviation between the output signal g of the air-fuel ratio sensor 44 and a target value to a base value, and uses this value to correct the fuel injection amount. More specifically, the value obtained by adding the correction amount according to the deviation to the base value affects the feedback correction coefficient FAF. The larger the value obtained by adding the correction amount according to the deviation to the base value, the larger the correction coefficient FAF becomes, and as a result, the fuel injection amount increases. Conversely, the smaller the value obtained by adding the correction amount according to the deviation to the base value, the smaller the correction coefficient FAF becomes, and as a result, the fuel injection amount decreases.

The above base value can be set to a different value for each operating range of the internal combustion engine. Map data that specifies the relationship between the operating range of the internal combustion engine [engine speed, intake pressure (or accelerator opening (engine load factor), intake volume or fuel injection volume, etc.)] and the base value is stored in advance in the memory of ECU0. ECU0 searches the map using the current operating range [engine speed, intake pressure, etc.] as a key to obtain the base value.

In this embodiment, an _O2 sensor is assumed as the air-fuel ratio sensor 44 downstream of the catalyst 41. The voltage of the output signal g of the _O2 sensor 44 shows a large and steep gradient in the rate of change of the output voltage with respect to the air-fuel ratio in a certain range near the stoichiometric air-fuel ratio, and in a lean region where the air-fuel ratio is larger than that, the output voltage asymptotically approaches a lower saturation value, and in a rich region where the air-fuel ratio is smaller than that, the output voltage asymptotically approaches a higher saturation value.

The ECU 0 gradually reduces the correction amount according to the deviation while the output voltage g of the O ₂ sensor 44 is higher than the target value, that is, while the air-fuel ratio of the gas flowing down from the catalyst 41 is richer than the target air-fuel ratio.

On the other hand, while the output voltage g of the O ₂ sensor 44 is lower than the target value, that is, while the air-fuel ratio of the gas flowing down from the catalyst 41 is leaner than the target air-fuel ratio, the correction amount according to the deviation is gradually increased.

The feature of this embodiment is that the base value is changed according to the current degree of deterioration of the catalyst 41. As shown in Figures 3(I) and 3(II), in conventional control, the base value is always fixed regardless of the degree of deterioration of the catalyst 41. In the control of this embodiment, when the degree of deterioration of the catalyst 41 is large, the base value is made larger than when the degree of deterioration of the catalyst 41 is smaller. Figure 2(I) is an example of control when the catalyst 41 is new, and Figure 2(II) is an example of control when the catalyst 41 has deteriorated. The latter base value is larger than the former base value. If the base value is larger, the correction coefficient FAF becomes larger accordingly, and the fuel injection amount increases.

The catalyst 41 deteriorates over time due to exposure to high heat and poisoning from the exhaust gas flowing into it, and its oxygen storage capacity decreases. The ECU 0 estimates the degree of deterioration of the catalyst 41 currently being used based on at least one of the following two index values:
[First index value]
A first index value is calculated which indicates the distance the vehicle has traveled using the catalyst 41 currently installed in the exhaust passage 4 of the internal combustion engine, or the length of time the internal combustion engine has been operated in that state.
The travel distance of the vehicle can be obtained by referring to a value measured by an on-board odometer or by integrating (or time-integrating) the vehicle speed determined from the output signal a of a vehicle speed sensor.
The operating length of the internal combustion engine can be obtained, for example, by integrating the engine speed determined from the output signal b of the crank angle sensor (or integrating it over time, which means calculating the cumulative number of rotations of the internal combustion engine), or by integrating the amount of intake air filled into cylinder 1 or the amount of fuel injected into cylinder 1 (or integrating it over time, which means calculating the total cumulative amount of gas that has flowed into the catalyst 41).
The first index value indirectly indicates the current degree of deterioration of the catalyst 41. It can be inferred that the larger the first index value is, the more deteriorated the catalyst 41 is.
[Second index value]
A second index value is calculated which indicates the degree of deterioration of the catalyst 41, by combining the degree of deterioration of the catalyst 41 during firing (particularly during air-fuel ratio feedback control after warm-up is complete) when fuel is supplied to cylinder 1 and burned to operate the internal combustion engine, while using the catalyst 41 currently installed in the exhaust passage 4, and the degree of deterioration of the catalyst 41 during fuel cut when no fuel is supplied to cylinder 1.
The thermal deterioration sensitivity D _{F ,} which is the degree of deterioration per unit time during firing or per unit cycle (one cycle is a series of intake stroke - compression stroke - expansion stroke - exhaust stroke), is
D _F = eα
α=C _F ×log _e T _F −S _F
In the above formula, e is the Napier's number. T _F is the temperature of the catalyst 41 during firing, and can be estimated according to any known method. For example, the temperature of the exhaust gas flowing into the catalyst 41 is calculated based on the current operating range of the internal combustion engine. Map data that specifies the relationship between the operating range of the internal combustion engine [engine speed, intake pressure, etc.] and the exhaust gas temperature is stored in advance in the memory of the ECU 0. The ECU 0 searches the map using the current operating range [engine speed, intake pressure, etc.] as a key to obtain the exhaust gas temperature. The estimated temperature T _F of the catalyst 41 is calculated taking into account the time required for the heat of the exhaust gas flowing into the catalyst 41 to be transmitted to the catalyst 41 and to raise the temperature of the catalyst 41. Of course, if a sensor that detects the temperature T _F of the catalyst 41 is attached, the temperature T _F of the catalyst 41 can be actually measured via the temperature sensor.
C _F and S _F are positive constants determined experimentally. C _F and S _F may vary in value depending on the specifications of the internal combustion engine including the catalyst 41 (the number of cylinders 1, the displacement, the output, the capacity of the catalyst 41, etc.).
The thermal degradation sensitivity D _{S ,} which is the degree of degradation per unit time or per unit cycle during fuel cut, is
D _S = eβ
β=C _S ×log _e T _S -S _S
Ts is the temperature of the catalyst 41 during fuel cut, and can be estimated according to any known method. Of course, if a sensor for detecting the temperature _Ts of the catalyst 41 is provided, the temperature _Ts of the catalyst 41 can be actually measured via the temperature sensor.
C _S and S _S are positive constants that are determined experimentally. The values of _{C S} and S _S may vary depending on the specifications of the internal combustion engine including the catalyst 41. C _S is not necessarily equal to C _F , and S _S is not necessarily equal to S _F.
Then, the sum of the integrated (or time-integrated) thermal degradation sensitivity D _F during firing and the integrated (or time-integrated) thermal degradation sensitivity D _S during fuel cut is calculated as a second index value, in other words, a thermal degradation index of the catalyst 41. The second index value more directly indicates the current degree of degradation of the catalyst 41. It can be estimated that the larger the second index value, the more the catalyst 41 is deteriorated.
[Modification of the second index value (oxygen storage capacity of the catalyst 41)]
The ECU 0 may estimate the current maximum oxygen storage capacity of the catalyst 41 and use this as the second index value. The oxygen storage capacity of the catalyst 41 may be estimated by adopting any known method. For example, in a state where oxygen is completely released from the catalyst 41, the air-fuel ratio of the gas flowing into the catalyst 41 is forcibly operated to be lean, and the amount of gas flowing into the catalyst 41 is integrated during the period from when the output signal f of the air-fuel ratio sensor 43 installed upstream of the catalyst 41 switches to lean until the output signal g of the air-fuel ratio sensor 44 installed downstream of the catalyst 41 switches to lean, and the amount of oxygen stored by the catalyst 41 is estimated from the amount of gas. The amount of oxygen stored at the time when the output g of the air-fuel ratio sensor 44 downstream of the catalyst 41 reverses to lean is the current maximum oxygen storage capacity of the catalyst 41.
Alternatively, with oxygen stored in the catalyst 41 up to its oxygen storage capacity, the air-fuel ratio of the gas flowing into the catalyst 41 is forcibly operated to be rich, and the amount of gas flowing into the catalyst 41 is integrated during the period from when the output signal f of the air-fuel ratio sensor 43 upstream of the catalyst 41 switches to rich until the output signal g of the air-fuel ratio sensor 44 downstream of the catalyst 41 switches to rich, and the amount of oxygen released by the catalyst 41 is estimated from that gas amount. The amount of oxygen released at the time when the output g of the air-fuel ratio sensor 44 downstream of the catalyst 41 reverses to rich is the current maximum oxygen release capacity of the catalyst 41, i.e., the maximum oxygen storage capacity.
The oxygen storage capacity estimated in this way can also be a second index value that combines the degree of deterioration of the catalyst 41 during firing and the degree of deterioration of the catalyst 41 during fuel cut. It can be estimated that the smaller the oxygen storage capacity is, the more deteriorated the catalyst 41 is.

Thus, the ECU 0 changes the base value in the air-fuel ratio feedback control in accordance with the first index value and/or the second index value. In principle, the base value is increased as the deterioration of the catalyst 41 progresses, and conversely, the base value is kept low if the deterioration of the catalyst 41 is not advanced.
The larger the first index value, the larger the base value is set. And/or
The larger the second index value is (however, if the current oxygen storage capacity is used as the second index value instead of the thermal deterioration index, the smaller this value is), the larger the base value is made. If the current operating range of the internal combustion engine, the deviation between the measured air-fuel ratio and the target air-fuel ratio, and other conditions are the same, the larger the base value is, the larger the fuel injection amount is.

When determining the base value, if both the first index value and the second index value are referenced, then if the first index values are equal, the base value is increased as the second index value is greater. Also, if the second index values are equal, the base value is increased as the first index value is greater.

As already mentioned, map data that defines the relationship between the operating range of the internal combustion engine (engine speed, intake pressure, etc.) and the base value is stored in the memory of ECU0, and this map data is searched to obtain the base value that corresponds to the current operating range, and this is used to control the fuel injection amount.

In this embodiment, the ECU 0 appropriately updates the base value on the map data. The condition for updating the map data is that the deviation between the first index value and the second index value at the current time is smaller than a predetermined value. If the absolute value of the difference (or ratio) between the current first index value converted to the second index value and the current second index value is smaller than a predetermined value (for example, if the absolute value of the difference between the two is within 10% to 15% of the former (or the latter)), it is considered that both have high accuracy. Therefore, the map data is updated by storing and holding the base value determined from the current first index value and/or second index value in memory as map data. The updated map data is used for controlling the fuel injection amount thereafter.

The ECU0 memory stores data that defines the relationship between a first index value, such as the vehicle's travel distance, and a second index value that is predicted after that travel distance has been reached. The ECU0 searches the data using the current first index value as a key, obtains the predicted second index value, and converts the first index value into the second index value.

In this embodiment, a first index value is obtained that indicates the distance the vehicle has traveled using the exhaust purification catalyst 41 currently installed in the exhaust passage 4 of the internal combustion engine, or the length of time the internal combustion engine has been operated in that state. A second index value is obtained that indicates the current degree of deterioration of the catalyst 41, which is a combination of the degree of deterioration of the catalyst 41 when fuel is supplied to cylinder 1 of the internal combustion engine and burned while using the catalyst 41, and the degree of deterioration of the catalyst 41 when a fuel cut is performed in which no fuel is supplied to cylinder 1. A fuel injection amount correction system is configured that modifies the amount of fuel injected into cylinder 1 by referring to the first index value and the second index value.

More specifically, the fuel injection amount is adjusted using a base value plus a correction amount according to the deviation in a feedback control that increases or decreases the fuel injection amount according to the deviation between the output signal g of the air-fuel ratio sensor 44 installed downstream of the catalyst 41 and its target value. In addition, the base value stored and held is updated by referring to the first index value or the second index value, provided that the deviation between the first index value and the second index value is smaller than a predetermined value.

In this embodiment, the base value is set smaller when the catalyst 41 is not yet degraded, and is increased as the catalyst 41 deteriorates. According to this embodiment, it is possible to converge the air-fuel ratio of the gas downstream of the catalyst 41 to the vicinity of the target air-fuel ratio, whether it is a new or undegraded catalyst 41 as shown in FIG. 2(I) or a degraded catalyst 41 as shown in FIG. 2(II). Even with the new catalyst shown in FIG. 2(I), the air-fuel ratio downstream of the catalyst 41 does not become significantly rich.

Moreover, there is no need to inject excessive amounts of fuel into a new or undegraded catalyst 41, meaning that fuel consumption can be reduced and saved. This can further improve fuel economy. In addition, there is no need to increase emissions of HC and CO.

The system of this embodiment does not require a sensor to accurately measure the temperature of the catalyst 41, and can be implemented at low cost.

The present invention is not limited to the embodiment described above. The specific configuration of each part and the processing procedure can be modified in various ways without departing from the spirit of the present invention.

The present invention can be applied to the control of an internal combustion engine mounted on a vehicle.

0...Control unit (ECU)
1... cylinder 11... injector 4... exhaust passage 41... catalyst 44... air-fuel ratio sensor ( _O2 sensor) downstream of catalyst
g... Air-fuel ratio signal downstream of the catalyst

Claims (3)

obtaining a first index value indicating a travel distance of a vehicle using an exhaust gas purification catalyst installed in an exhaust passage of an internal combustion engine, or a length of time during which the internal combustion engine has been operated with the catalyst installed;
obtaining a second index value indicating a degree of deterioration of the catalyst, the second index value being a combination of a degree of deterioration of the catalyst when fuel is supplied to a cylinder of an internal combustion engine and the fuel is combusted while the catalyst is in use, and a degree of deterioration of the catalyst when a fuel cut is performed in which no fuel is supplied to the cylinder ;
a feedback control for increasing or decreasing a fuel injection amount in accordance with a deviation between an output signal of an air-fuel ratio sensor installed in the exhaust passage and a target value thereof, the fuel injection amount being corrected by using a base value plus a correction amount in accordance with the deviation;
A fuel injection amount correction system that updates the base value in the feedback control so as to increase the fuel injection amount as the deterioration of the catalyst estimated by referring to the first index value or the second index value progresses, and keeps the base value low if the deterioration of the catalyst is not progressing. The memory stores in advance data defining a relationship between the first index value and the second index value predicted at the time of the first index value,
2. A fuel injection amount correction system according to claim 1, wherein the base value is updated by referring to the first index value or the second index value, under the condition that a deviation between the current first index value converted into the second index value and the current second index value is smaller than a predetermined value. obtaining a first index value indicating a travel distance of a vehicle using an exhaust gas purification catalyst installed in an exhaust passage of an internal combustion engine, or a length of time during which the internal combustion engine has been operated with the catalyst installed;
obtaining a second index value indicating a degree of deterioration of the catalyst, the second index value being a combination of a degree of deterioration of the catalyst when fuel is supplied to a cylinder of an internal combustion engine and the fuel is combusted while the catalyst is in use, and a degree of deterioration of the catalyst when a fuel cut is performed in which no fuel is supplied to the cylinder ;
a feedback control for increasing or decreasing a fuel injection amount in accordance with a deviation between an output signal of an air-fuel ratio sensor installed in the exhaust passage and a target value thereof, the fuel injection amount being corrected by using a base value plus a correction amount in accordance with the deviation;
A method for correcting a fuel injection amount, in which the base value in the feedback control is updated so as to increase the fuel injection amount as the deterioration of the catalyst estimated by referring to the first index value or the second index value progresses, and the base value is kept low if the deterioration of the catalyst is not progressing.

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