Air-fuel ratio sensor output value correction device for internal combustion engine

Abstract

Provided is a device for correcting an output value of an air-fuel ratio sensor for an internal-combustion engine, the device comprising: a relational expression storage means 112 for storing a relational expression between an air-fuel ratio and an output value of an air-fuel ratio sensor 30; a reference relational expression storage means 110 for previously storing a rich region reference relational expression and a lean region reference relational expression; a slightly rich state operation means 103; a rich region correction relational expression decision means 105 for deciding a rich region correction relational expression on the basis of an actually measured output value Vrr in a slightly rich operation and a reference output value Vr0; a relational expression correspondence storage means 111 for storing the correspondence between the rich region correction relational expression and a lean region correction relational expression; a lean region correction relational expression decision means 106 for deciding a lean region correction relational expression with reference to the rich region correction relational expression and the relational expression correspondence storage means 111; and a relational expression rewriting means 107 for rewriting the relational expression of the relational expression storage means 112 into a correction relational expression, wherein even when a deviation occurs in the relationship between the air-fuel ratio and the output value of the air-fuel ratio sensor, the deviation of the detected value of the air-fuel ratio sensor is corrected without the provision of a separate oxygen sensor.

Description

[Technical Field]

[0001] The present invention relates to an air-fuel ratio sensor output value correction device for an internal combustion engine, which corrects deviations in the output value of an air-fuel ratio sensor of an internal combustion engine. [Background technology]

[0002] Conventionally, in an exhaust device of an internal combustion engine, there is an exhaust purification system for an internal combustion engine that uses a signal from an air-fuel ratio sensor (LAF sensor) provided in the exhaust passage to control the air-fuel ratio in the exhaust passage to a target air-fuel ratio (such as a stoichiometric air-fuel ratio) by braking operation of a control unit of the air-fuel ratio sensor that performs PI control (proportional-integral control) or the like. Deviations may occur in the relationship between the air-fuel ratio and the output value of the air-fuel ratio sensor due to individual differences in the air-fuel ratio sensor, sensor characteristics such as aging, and environmental influences such as pressure and temperature. In such cases, there is a method of correcting the target air-fuel ratio using a signal from an oxygen sensor provided in an exhaust passage separate from the air-fuel ratio sensor, thereby providing control as if an air-fuel ratio sensor with no deviation was being used (see Patent Document 1).

[0003] However, since another oxygen sensor is used to correct the target air-fuel ratio so as to prevent deviations in the detected value of the air-fuel ratio sensor, deviations in the output value of the air-fuel ratio sensor become large when the oxygen sensor deteriorates. Therefore, it is required to correct deviations in the output value of the air-fuel ratio sensor using only the air-fuel ratio sensor, without using the output value of the oxygen sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-56753 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide an air-fuel ratio sensor output value correction device for an internal combustion engine that can correct deviations in the detection value of an air-fuel ratio sensor, even if deviations occur in the relationship between the air-fuel ratio and the output value of the air-fuel ratio sensor, without the need to provide a separate oxygen sensor. [Means for solving the problem]

[0006] The present invention provides an air-fuel ratio sensor output value correction device for an internal combustion engine that corrects an output value of an air-fuel ratio sensor provided in an exhaust system of the internal combustion engine, comprising: an air-fuel ratio and an output value of the air-fuel ratio sensor at the air-fuel ratio are expressed by a relational expression, the relationship between the air-fuel ratio in a rich region and the output value of the air-fuel ratio sensor is expressed by a rich region relational expression, and the relationship between the air-fuel ratio in a lean region and the output value of the air-fuel ratio sensor is expressed by a lean region relational expression, a relational expression storage means for storing the rich region relational expression and the lean region relational expression; the air-fuel ratio sensor has a reference output value serving as a reference for each air-fuel ratio; and a reference relational expression storage means for pre-storing a rich region reference relational expression in a rich region and a lean region reference relational expression in a lean region; a weak rich state operating means for operating the internal combustion engine at a predetermined weak rich air-fuel ratio for a predetermined period of time; a rich region correction relational expression determining means for calculating and determining a rich region correction relational expression by comparing an actual output value at the slight rich air-fuel ratio with a reference output value; a relational expression correspondence storage means for storing in advance the correspondence between the rich region correction relational expression and the lean region correction relational expression; a lean region correction relational expression determining means for determining a lean region correction relational expression in a lean region by referring to the rich region correction relational expression determined by the rich region correction relational expression determining means and the relational expression correspondence storing means; and relational expression rewriting means for rewriting the rich region relational expression stored in the relational expression storage means into the rich region correction relational expression calculated by the rich region correction relational expression determination means, and for rewriting the lean region relational expression stored in the relational expression storage means into the lean region correction relational expression determined by the lean region correction relational expression determination means.

[0007] Since deviations in the output value of the air-fuel ratio sensor can be corrected using only the air-fuel ratio sensor without providing a separate oxygen sensor, costs can be reduced. Furthermore, since deviations in the output value of the air-fuel ratio sensor can be detected in the rich region where NOx does not increase and the output values ​​of the air-fuel ratio sensor in the rich region and the lean region can be corrected, the output accuracy required of the air-fuel ratio sensor in the lean region can be relaxed and the cost of the air-fuel ratio sensor can be reduced.

[0008] Furthermore, the present invention is characterized in that the larger the difference between the actual output value and the reference output value at the weak rich air-fuel ratio, the larger the difference between the slope of the rich region correction relational expression and the slope of the rich region reference relational expression, and the difference between the slope of the lean region correction relational expression and the slope of the lean region reference relational expression.

[0009] When using only an air-fuel ratio sensor, the greater the difference between the measured output value and the reference output value at a weak rich air-fuel ratio, the greater the difference in slope between the lean region correction relational expression and the reference relational expression, and the difference in slope between the rich region correction relational expression and the reference relational expression. Therefore, the output accuracy required of the air-fuel ratio sensor in the lean region can be relaxed, and the cost spent on the air-fuel ratio sensor can be reduced.

[0010] Furthermore, the present invention is characterized in that, when the actual output value of the air-fuel ratio sensor is lower than the reference output value at the weak rich air-fuel ratio, the slope of the lean region correction relational expression is corrected to be larger than the slope of the lean region reference relational expression.

[0011] Since the air-fuel ratio sensor uses an oxygen battery, when the actual measurement value of the air-fuel ratio sensor is lower than the reference value at a slight rich air-fuel ratio, the slope of the lean region correction relational expression can be corrected to be larger than the slope of the reference relational expression, thereby relaxing the output accuracy required of the air-fuel ratio sensor in the lean region, and enabling the use of an inexpensive air-fuel ratio sensor.

[0012] Furthermore, the present invention is characterized in that, when the actual output value of the air-fuel ratio sensor is higher than the reference output value at the weak rich air-fuel ratio, the slope of the lean region correction relational expression is corrected to be smaller than the slope of the lean region reference relational expression.

[0013] Since the air-fuel ratio sensor uses an oxygen battery, when the actual measurement value of the air-fuel ratio sensor is higher than the reference value at a slight rich air-fuel ratio, the output accuracy required of the air-fuel ratio sensor in the lean region can be relaxed by correcting the slope of the lean region correction relational expression to be smaller than the slope of the reference relational expression, thereby enabling the use of an inexpensive air-fuel ratio sensor. [Effects of the Invention]

[0014] According to the present invention, the deviation of the output value of the air-fuel ratio sensor can be corrected using only the air-fuel ratio sensor without providing a separate oxygen sensor, thereby reducing costs. Furthermore, since the deviation of the output value of the air-fuel ratio sensor can be detected in the rich region where NOx does not increase and the output value of the air-fuel ratio sensor in the rich region and the lean region can be corrected, the output accuracy required of the air-fuel ratio sensor in the lean region can be relaxed and the cost of the air-fuel ratio sensor can be reduced. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of an air-fuel ratio sensor output correction device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] 1 is a block diagram of an air-fuel ratio sensor output correction device according to an embodiment of the present invention; [Figure 3]3 is a flowchart of an air-fuel ratio sensor output correction device according to one embodiment of the present invention. [Figure 4] 4 is a graph showing a reference relational expression, a rich region correction relational expression, and a lean region correction relational expression of an air-fuel ratio sensor; [Figure 5] 4 is a graph showing a reference relational expression and an example of a correction relational expression of an air-fuel ratio sensor; [Figure 6] 10 is a graph showing a reference relational expression and another example of a correction relational expression of an air-fuel ratio sensor. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an internal combustion engine 1 and an air-fuel ratio sensor output value correction device 100 according to this embodiment.

[0017] The internal combustion engine 1 is mounted on a vehicle and is, for example, a direct injection gasoline engine in which fuel is injected directly into each of a plurality of cylinders by a fuel injection valve 10 provided for each cylinder.

[0018] 1, an electronically controlled throttle valve 11 that adjusts the amount of intake air is provided in an intake passage 2 of an internal combustion engine 1. The throttle valve 11 is provided with a throttle position sensor 12 that measures the opening of the throttle valve 11. Furthermore, an air flow rate detection means (for example, an air flow sensor 13) is provided upstream of the throttle valve 11 in the intake passage 2.

[0019] Furthermore, the internal combustion engine 1 is provided with sensors (not shown) that detect the operating conditions of the internal combustion engine 1.

[0020] A catalytic converter 31 is disposed in the exhaust passage 3 of the internal combustion engine 1 . An air-fuel ratio sensor 30 for detecting oxygen concentration is provided downstream of the internal combustion engine 1 and upstream of the catalytic device 31.

[0021] The ECU 40 is a control device that controls the operating conditions of the internal combustion engine 1 and also performs overall control, and includes an input device, an output device, a storage device (ROM, RAM, etc.), and a central processing unit (CPU).

[0022] The input side of the ECU 40 receives detection information from various sensors that detect the operating state of the internal combustion engine 1 and the vehicle, such as the throttle position sensor 12, air flow sensor 13, air-fuel ratio sensor 30, and other sensors such as a crank angle sensor, a water temperature sensor, an accelerator position sensor, and a vehicle speed sensor.

[0023] The output side of the ECU 40 is connected to various devices such as the throttle valve 11, the fuel injection valve 10, and other devices such as spark plugs. The ECU 40 calculates a target throttle opening, a fuel injection amount, an ignition timing, etc. based on detection information from various sensors, and outputs the calculated values ​​to various output devices to control the throttle valve 11 and the fuel injection valve 10. The ECU 40 determines the fuel injection mode, such as the fuel injection amount and fuel injection timing, of the fuel injection valve 10, and drives the fuel injection valve 10 to open and close so as to achieve the determined fuel injection mode.

[0024] The air-fuel ratio sensor 30 is subject to sensor characteristics such as individual differences and deterioration over time, as well as environmental influences such as pressure and temperature, which may cause the output value of the air-fuel ratio sensor relative to the air-fuel ratio to deviate from the output value based on the basic characteristics. In this case, if the air-fuel ratio is determined based on the output value from the air-fuel ratio sensor 30, a deviation from the actual air-fuel ratio will occur, and if feedback control of the combustion state of the internal combustion engine is performed based on the deviated air-fuel ratio, it will be difficult to achieve the target combustion state.

[0025] Therefore, the ECU 40 has an air-fuel ratio sensor output value correction function for correcting the deviation of the output value of the air-fuel ratio sensor 30. The ECU 40 serves as an air-fuel ratio sensor output value correction device 100.

[0026] In Figure 4, the relationship between the air-fuel ratio and the output value of the air-fuel ratio sensor 30 is shown by a solid line as the basic characteristic when there is no deviation between the air-fuel ratio and the output value of the air-fuel ratio sensor 30. The relationship between the air-fuel ratio and the output value of the air-fuel ratio sensor 30 is a linear relationship and is expressed by a relational expression. The expression that expresses the relationship between the output value of the air-fuel ratio sensor 30 and the air-fuel ratio of the basic characteristic is called the reference relational expression. The relationship between the output value of the air-fuel ratio sensor in the rich region and the relationship between the output value of the air-fuel ratio sensor in the lean region are each expressed by separate equations. The respective equations in the basic characteristic of the air-fuel ratio sensor are called the rich region reference relational expression and the lean region reference relational expression.

[0027] FIG. 2 shows a block diagram of the air-fuel ratio sensor output value correction device 100. The air-fuel ratio sensor output value correction device 100 of this embodiment is configured to include correction timing determination means 101, means 102 for determining whether stoichiometric operation has continued for a specified time, weak rich state operation means 103, air-fuel ratio sensor actual value measurement means 104, rich region correction relational equation determination means 105, lean region correction relational equation determination means 106, relational equation rewriting means 107, reference relational equation storage means 110, relational equation correspondence storage means 111, and relational equation storage means 112.

[0028] The correction timing determination means 101 determines whether or not to correct the relational expression that indicates the relationship between the output value of the air-fuel ratio sensor 30 and the air-fuel ratio, based on the cumulative mileage of the vehicle stored in the odometer. The cumulative mileage at which it is determined that correction should be performed is predetermined, and determines the timing to eliminate the difference between the output value of the air-fuel ratio sensor 30 for the air-fuel ratio after traveling a predetermined distance and the output value in the basic characteristics. Furthermore, if the correction is set to be performed even when the cumulative mileage is zero, the means 101 corrects the difference due to individual differences in the air-fuel ratio sensor 30.

[0029] The stoichiometric operation specified time continuation determination means 102 determines whether the stoichiometric operation state of the internal combustion engine 1 has continued for a predetermined time or more. When the stoichiometric state has continued for the predetermined time, the complete combustion state continues for a certain period of time, so when the operating state is changed to a weak rich operating state to obtain the correction relational expression, the influence of the state of the exhaust system immediately before can be reduced.

[0030] The weak rich state operation means 103 measures the intake amount using an air flow meter or the like and controls the opening of the throttle valve 11 and the amount of fuel injected from the fuel injection valve so that the air-fuel ratio becomes a predetermined weak rich state air-fuel ratio Rr.

[0031] The air-fuel ratio sensor actual measurement value measuring means 104 receives the voltage output by the air-fuel ratio sensor 30 when the air-fuel ratio sensor 30 is in a slight rich state as an actual measurement output value Vrr.

[0032] The reference relational expression storage means 110 stores a reference relational expression that indicates the relationship between the air-fuel ratio and the output value of the air-fuel ratio sensor 30. The reference relational expression is expressed by a linear function that differs between the rich region and the lean region, as shown by the solid line in Fig. 4, and stores a rich region reference relational expression and a lean region reference relational expression. The lean region reference relational expression and the lean region reference relational expression are in a relationship where they intersect at the reference voltage Vs at the stoichiometric value Rs. The rich region reference relational expression is expressed as y=a0x+b0, where y is the voltage output from the sensor and x is the air-fuel ratio corresponding to the output voltage. The lean region reference relational expression is expressed as y=a0'x+b0'. Before correcting the output value of the air-fuel ratio sensor 30, these reference relational expressions are stored as relational expressions, and the air-fuel ratio is calculated by substituting the voltage of the actual measured value of the air-fuel ratio sensor 30 into these relational expressions.

[0033] The rich region correction relational expression determining means 105 determines a corrected rich region correction relational expression y=a from the difference between the actual measurement output value Vrr, which is the voltage value of the air-fuel ratio sensor 30 measured by the air-fuel ratio sensor actual measurement value measuring means 104 when the weak rich state operating means 103 operates the internal combustion engine 1 at a predetermined weak rich state air-fuel ratio Rr, and the reference voltage Vr0 at the air-fuel ratio Rr stored in the reference relational expression storing means 110. c x+b c A processing method for obtaining the rich region correction relational expression based on the difference between the actual measured output value Vrr and the reference voltage Vr0 is stored in advance, and the rich region correction relational expression y=a c x+b cis determined.

[0034] There is a predetermined relationship between the gradient a of the rich region relational expression and the gradient a' of the lean region relational expression, which is stored in the relational expression correspondence storage means. 4 shows examples of the basic relational expressions and a plurality of correction relational expressions of the air-fuel ratio sensor output value correction device 100 of this embodiment. The relationship between the rich region relational expressions and the corresponding lean region relational expressions is also shown. For example, the correspondence relationship, such as the slope a1 of the rich region relational expression corresponds to the slope a1' of the lean region relational expression, the slope a2 of the rich region relational expression corresponds to the slope a2' of the lean region relational expression, etc., or an equation for calculating the slope a' of the lean region from the slope a of the rich region is stored. Or, not only the relationship between the slope a of the rich region equation and the slope a' of the lean region equation, but also the relationship between the slope a of the rich region equation y=a c x+b c The corresponding lean region correction equation is y=a c 'x+b c ' may be pre-entered.

[0035] As shown in FIG. 4, in this embodiment, the gradient a of the rich region correction relational expression c The larger the difference between the slope a0 of the basic equation and the slope a of the lean region equation, c ' is set so that the difference with the slope a0' of the basic relational expression becomes large. Furthermore, as shown in FIG. 5, the slope a of the rich region correction relational expression c If the slope of the basic equation is greater than a0, the slope of the lean region correction equation a c ' is set to be larger than the slope a0' of the reference relational expression. As shown in FIG. 6, the slope a of the rich region correction equation c If the slope of the basic equation is smaller than a0, the slope of the lean region correction equation is a c ' is set to be smaller than the slope a0' of the reference relational expression.

[0036] The lean region correction relational expression determining means 106 determines the slope a of the rich region correction relational expression calculated by the rich region correction relational expression determining means 105. c and the slope a of the rich region relational expression stored in the relational expression correspondence storage means 111. c The slope of the lean region equation corresponding to c ' or directly from the Ricci region relation y=a c x+b c From the lean region correction equation y=a c 'x+b c ' to determine.

[0037] The relational expression rewriting means 107 rewrites the relational expression stored in the relational expression storage means 112, which indicates the relationship between the actual measured voltage of the air-fuel ratio sensor 30 and the air-fuel ratio, by the relational expression y=a calculated by the rich region correction relational expression determining means 105. c x+b c and y=a determined by the lean region correction relational expression determining means 106. c 'x+b c ', and rewrite it.

[0038] Next, the processing procedure of the air-fuel ratio sensor output value correction device 100 in this embodiment will be described with reference to the flowchart shown in FIG.

[0039] In step 1, the processing of the air-fuel ratio sensor output value correction device 100 is started at a predetermined timing, such as when the internal combustion engine 1 is started.

[0040] Next, the process proceeds to step 2, where the correction timing determination means 101 determines whether the air-fuel ratio sensor 30 satisfies the conditions for starting correction. In the air-fuel ratio sensor output value correction device 100 of this embodiment, the timing for starting correction of the air-fuel ratio sensor is determined based on the cumulative mileage of the vehicle. If it is determined that the cumulative mileage has reached a predetermined distance, correction of deviations due to deterioration of the air-fuel ratio sensor is started. Furthermore, if the predetermined cumulative mileage is set to 0, variation in the initial value of the air-fuel ratio sensor is corrected.

[0041] If it is determined in step 2 that the correction requirement is satisfied, the process proceeds to step 3, where the stoichiometric operation specified time continuation determination means 102 determines whether stoichiometric steady-state operation has continued for a predetermined specified time. If it is determined in step 3 that stoichiometric operation has not continued for the specified time, the process returns to step 3 again, and continues to determine whether stoichiometric operation has continued for the specified time. The determination of whether stoichiometric steady-state operation has continued for the specified time is made to eliminate the possibility that fluctuations in the air-fuel ratio will affect the measurement of the air-fuel ratio during weak rich operation in the next step 3.

[0042] If it is determined in step 3 that stoichiometric operation has continued for a specified time, the process proceeds to step 4, where the weak rich state operation means 103 changes the fuel injection amount of the fuel injection valve 10 and the opening of the throttle valve 11, and the combustion state of the internal combustion engine 1 is shifted to a predetermined air-fuel ratio Rr, which is a weak rich operating state in which the fuel ratio is slightly higher than the stoichiometric air-fuel ratio.

[0043] When the internal combustion engine 1 is in an operating state with the air-fuel ratio Rr, the process proceeds to step 5, where the air-fuel ratio sensor actual value measuring means 104 measures and stores the actual measured output value Vrr, which is the voltage of the air-fuel ratio sensor 30 at the air-fuel ratio Rr.

[0044] When step 5 is completed, the process proceeds to step 6. In step 6, the rich region correction relational expression is determined by the rich region correction relational expression determining means 105 based on the difference between the reference output value Vr0 and the actual measured output value Vrr at the predetermined air-fuel ratio Rr in the slight rich state.

[0045] After step 6 is completed, the process proceeds to step 7, where the lean region correction relational expression is determined by the lean region correction relational expression determining means 106. The actual output value, which is the actual output value of the oxygen concentration sensor in a slightly rich operating state, is input and stored as the reference output value at the air-fuel ratio Rr.

[0046] When step 7 is completed, the process proceeds to step 8, where the operation in the weak rich state is terminated and the normal operating state is restored.

[0047] When step 8 is completed, the process proceeds to step 9. In step 8, the rich region correction relational expression determined by the rich region correction relational expression determination means 105 and the relational expression correspondence storage means 111 are referenced to determine the rich region correction relational expression.

[0048] When step 9 is completed, the process proceeds to step 10, where the rich region relational expression stored in the relational expression storage means 112 is rewritten to the rich region correction relational expression determined by the rich region correction relational expression determination means 105, and the lean region relational expression is rewritten to the lean region correction relational expression determined by the lean region correction relational expression determination means 106.

[0049] When step 10 is completed, the process proceeds to step 11, where the processing of the air-fuel ratio sensor output value correction device 100 ends, and from this point on, the air-fuel ratio sensor 30 applies the actually measured voltage to the rewritten new rich region relational expression and lean region relational expression to output the air-fuel ratio.

[0050] The intake structure for an internal combustion engine according to the embodiment of the present invention is configured as described above, and therefore provides the following effects.

[0051] The present invention relates to an air-fuel ratio sensor output value correction device for an internal combustion engine that corrects the output value of an air-fuel ratio sensor 30 provided in an exhaust system of the internal combustion engine 1, and includes relational expression storage means 112 that stores the rich region relational expression and the lean region relational expression, wherein the air-fuel ratio and the output value of the air-fuel ratio sensor 30 at that air-fuel ratio are represented by a relational expression, the relationship between the air-fuel ratio in a rich region and the output value of the air-fuel ratio sensor 30 in a lean region is represented by a rich region relational expression, and the relationship between the air-fuel ratio in a lean region and the output value of the air-fuel ratio sensor 30 is represented by a lean region relational expression, the reference relational expression storage means 110 that stores in advance the rich region reference relational expression in the rich region and the lean region reference relational expression in the lean region, the air-fuel ratio sensor has a reference output value that serves as a reference for each air-fuel ratio, and the reference relational expression storage means 110 stores in advance the rich region reference relational expression in the rich region and the lean region reference relational expression in the lean region, the weak rich state operation means 103 that operates the internal combustion engine 1 for a predetermined time at a predetermined weak rich air-fuel ratio Rr, and the actual measured output value Vrr at the weak rich air-fuel ratio Rr The air-fuel ratio sensor output value correction device 100 for an internal combustion engine comprises: rich region correction relational expression determining means 105 that calculates and determines a rich region correction relational expression by comparing with a reference output value Vr0; relational expression correspondence storing means 111 that stores in advance the correspondence between the rich region correction relational expression and the lean region correction relational expression; lean region correction relational expression determining means 106 that determines a lean region correction relational expression in the lean region by referring to the rich region correction relational expression determined by the rich region correction relational expression determining means 105 and the relational expression correspondence storing means 111; and relational expression rewriting means 107 that rewrites the rich region relational expression stored in the relational expression storing means 112 with the rich region correction relational expression calculated by the rich region correction relational expression determining means 105, and rewrites the lean region relational expression stored in the relational expression storing means 112 with the lean region correction relational expression determined by the lean region correction relational expression determining means 106.

[0052] With the above-described configuration, deviations in the output value of the air-fuel ratio sensor 30 can be corrected using only the air-fuel ratio sensor 30 without providing a separate oxygen sensor, thereby reducing costs. Furthermore, since deviations in the output value of the air-fuel ratio sensor 30 can be detected in the rich region where NOx does not increase and the output values ​​of the air-fuel ratio sensor 30 in the rich region and the lean region can be corrected, the output accuracy required of the air-fuel ratio sensor 30 in the lean region can be relaxed and the cost of the air-fuel ratio sensor 30 can be reduced.

[0053] Furthermore, the larger the difference between the measured output value Vrr and the reference output value Vr0 at the weak rich air-fuel ratio Rr, the greater the gradient a of the rich region correction relational expression. c and the difference between the slope a0 of the rich region reference equation and the slope a of the lean region correction equation c Since the difference between the gradient a0' of the lean region reference relational expression and the gradient a0' of the lean region reference relational expression becomes large, the output accuracy required of the air-fuel ratio sensor 30 in the lean region can be relaxed, and the cost of the air-fuel ratio sensor 30 can be reduced.

[0054] In addition, when the measured output value Vrr of the air-fuel ratio sensor is lower than the reference output value Vr0 at a slight rich air-fuel ratio Rr, the slope a of the lean region correction relational expression c Since the air-fuel ratio sensor uses an oxygen battery, the output accuracy required of the air-fuel ratio sensor 30 in the lean region can be relaxed, and an inexpensive air-fuel ratio sensor 30 can be used.

[0055] Furthermore, when the measured output value Vrr of the air-fuel ratio sensor 30 is higher than the reference output value Vr0 at a slight rich air-fuel ratio Rr, the slope a of the lean region correction relational expression c Since the gradient a0' of the lean region reference relational expression is corrected to be smaller than the gradient a0' of the lean region reference relational expression, the output accuracy required of the air-fuel ratio sensor 30 in the lean region can be relaxed, and an inexpensive air-fuel ratio sensor 30 can be used.

[0056] The present invention is not limited to internal combustion engines that inject fuel into cylinders as in the above-described embodiment, but can be applied to various types of internal combustion engines, and can be widely applied to correcting the output value of an air-fuel ratio sensor provided in such internal combustion engines. [Explanation of symbols]

[0057] 1... internal combustion engine, 30... air-fuel ratio sensor, 100... air-fuel ratio sensor output value correction device, 103... weak rich state operation means, 105... rich region correction relational expression determination means, 106... lean region correction relational expression determination means, 107... relational expression rewriting means, 110...reference relational expression storage means, 111...relational expression correspondence storage means, 112...relational expression storage means, Rr...predetermined air-fuel ratio in a weak rich state, Vrr...actually measured output value in a weak rich state, Vr0...reference output value in a weak rich state, a c ...Slope of the rich region correction equation, a0...Slope of the rich region reference equation, a c '...slope of the lean region correction equation, a0'...slope of the lean region reference equation.

Claims

1. An apparatus for correcting an output value of an air-fuel ratio sensor (30) provided in an exhaust system of an internal combustion engine (1), comprising: an air-fuel ratio and an output value of the air-fuel ratio sensor (30) at the air-fuel ratio are expressed by a relational expression, the relationship between the air-fuel ratio in a rich region and the output value of the air-fuel ratio sensor (30) is expressed by a rich region relational expression, and the relationship between the air-fuel ratio in a lean region and the output value of the air-fuel ratio sensor (30) is expressed by a lean region relational expression, a relational expression storage means (112) for storing the rich region relational expression and the lean region relational expression; the air-fuel ratio sensor has a reference output value serving as a reference for each air-fuel ratio, and a reference relational expression storage means (110) for pre-storing a rich region reference relational expression in a rich region and a lean region reference relational expression in a lean region; a weak rich state operating means (103) for operating the internal combustion engine (1) at a predetermined weak rich air-fuel ratio (Rr) for a predetermined time; The actual output value (Vrr) at the slightly rich air-fuel ratio (Rr) and the reference output value (Vr 0 ) and a rich region correction relational expression determining means (105) for calculating and determining a rich region correction relational expression; a relational expression correspondence storage means (111) for storing in advance the correspondence between the rich region correction relational expression and the lean region correction relational expression; a lean region correction relational expression determining means (106) for determining a lean region correction relational expression in a lean region by referring to the rich region correction relational expression determined by the rich region correction relational expression determining means (105) and the relational expression correspondence storing means (111); a relational expression rewriting means (107) that rewrites the rich region relational expression stored in the relational expression storage means (112) into the rich region correction relational expression calculated by the rich region correction relational expression determination means (105), and rewrites the lean region relational expression stored in the relational expression storage means (112) into the lean region correction relational expression determined by the lean region correction relational expression determination means (106); 1. An air-fuel ratio sensor output value correction device for an internal combustion engine, comprising:

2. The actual output value (Vrr) at the slightly rich air-fuel ratio (Rr) and the reference output value (Vr 0 ) the greater the difference, the greater the gradient (a c ) and the slope of the rich region reference equation (a 0 ) and the slope of the lean region correction relational expression (a c ') and the slope of the lean region reference relational expression (a 0 2. The apparatus for correcting an output value of an air-fuel ratio sensor for an internal combustion engine according to claim 1, wherein the difference between the air-fuel ratio sensor output value and the air-fuel ratio sensor output value is large.

3. At the slight rich air-fuel ratio (Rr), the actual output value (Vrr) of the air-fuel ratio sensor is equal to or exceeds the reference output value (Vr 0 ), the slope of the lean region correction equation (a c ') is calculated by the slope (a 0 3. The apparatus for correcting an output value of an air-fuel ratio sensor for an internal combustion engine according to claim 1, wherein the output value is corrected so as to be greater than the air-fuel ratio sensor output value.

4. At the slight rich air-fuel ratio (Rr), the actual output value (Vrr) of the air-fuel ratio sensor is equal to or exceeds the reference output value (Vr 0 ), the slope of the lean region correction equation (a c ') is calculated by the slope (a 0 3. The apparatus for correcting an output value of an air-fuel ratio sensor for an internal combustion engine according to claim 1, wherein the output value is corrected so as to be smaller than the air-fuel ratio sensor output value.

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