JP7382378B2 - Air fuel ratio control device - Google Patents

Description

The present invention relates to an air-fuel ratio control device that controls an air-fuel ratio in an internal combustion engine based on a detected value of an oxygen concentration sensor provided downstream of a catalyst section of an exhaust pipe.

Conventionally, as an air-fuel ratio control device that controls the air-fuel ratio in an internal combustion engine, in order to reduce costs, there is a known device that eliminates the oxygen sensor upstream of the catalyst section and uses only the downstream oxygen sensor to feedback control the air-fuel ratio. (For example, see Patent Document 1).

In the air-fuel ratio control device of Patent Document 1, immediately after the fuel cut control or deceleration lean is completed, the air-fuel ratio control is once set to open-loop rich spike control, and the actual air-fuel ratio is changed based on the output value of the oxygen sensor. At the stage when it is determined that the rich side has been reached, the closed-loop air-fuel ratio feedback control in the air-fuel ratio controller main body is restarted.

In the open-loop rich spike control described above, a predetermined amount of fuel is supplied to the combustion chamber of the engine while referring to the rich spike map. As a result, the oxygen concentration sensor (linear air-fuel ratio (LAF) sensor in the embodiment of Patent Document 1) upstream of the catalyst section is eliminated, and the air-fuel ratio is optimized and the cost of the system is reduced.

Japanese Patent Application Publication No. 2014-70600

However, according to the air-fuel ratio control device of Patent Document 1, after the air-fuel ratio control is set to open-loop rich spike control until the actual air-fuel ratio becomes rich, the air-fuel ratio control unit main body controls the air-fuel ratio. Fuel ratio feedback control is stopped. The accuracy of setting the air-fuel ratio during this rich spike control depends on the accuracy of setting the rich spike map and the like. Therefore, it takes time to settle the actual air-fuel ratio to an appropriate value.

On the other hand, if the rich spike control of Patent Document 1 is not performed, the healthier the function of the catalyst, the more the actual air-fuel ratio (excess air ratio λ) upstream of the catalyst of the internal combustion engine and the downstream of the catalyst A discrepancy occurs between the catalyst downstream air-fuel ratio detected by the side oxygen concentration sensor. In this case, the amount of oxygen in the exhaust gas is effectively reduced by the action of a healthy catalyst section, resulting in a state where the excess air ratio λ is greater than 1 on the upstream side of the catalyst section, that is, within the cylinders of the internal combustion engine, that is, over lean. Even if it is, the excess air ratio λ on the downstream side of the catalyst section will be smaller than 1, that is, it will be in a rich state. This deviation causes events such as engine stalling and hesitation (breathing of the engine) when performing feedback control of the air-fuel ratio using only the downstream oxygen sensor, resulting in poor drivability.

In view of the problems of the prior art, an object of the present invention is to provide an air-fuel ratio control device that can correct the occurrence of the overlean state in the cylinder and avoid deterioration of drivability.

The air-fuel ratio control device of the present invention includes:
a throttle opening detection unit that detects a value related to the opening of a throttle valve that opens and closes an intake pipe of the internal combustion engine;
an air-fuel ratio feedback section configured to increase or decrease an air-fuel ratio feedback coefficient based on feedback of a detected value of an oxygen concentration sensor provided downstream of a catalyst section of an exhaust pipe of the internal combustion engine;
a torque calculation unit that detects the operating state of the internal combustion engine and calculates the torque generated by the internal combustion engine;
a directionality checking unit that checks whether the torque increases or decreases when the throttle valve opens ;
and an air-fuel ratio feedback limiting section configured to limit the setting of the air-fuel ratio feedback coefficient that reduces the torque when the directionality confirmation section confirms that the torque decreases. .

In the present invention, a sign of hesitation is detected (predicted) when the torque of the internal combustion engine is inversely proportional (decreased) to the acceleration (increase in opening) operation of the throttle valve. At this time, if the air-fuel ratio feedback coefficient by the oxygen concentration sensor downstream of the catalyst tends to decrease in proportion to the decrease in torque, then as the amount of oxygen in the exhaust gas is reduced at the catalyst, Although the excess air ratio λ on the side is rich, the excess air ratio λ upstream of the catalyst section, that is, within the cylinders of the internal combustion engine is considered to be heading toward a state larger than 1, that is, an overlean state.

In this regard, according to the present invention, when the direction confirmation section confirms that the torque decreases when the throttle valve opens, the air-fuel ratio feedback limiting section provides air-fuel ratio feedback such that the torque decreases. Limit the settings of coefficients. This makes it possible to foresee and avoid problems such as engine stalling and hesitation due to the overlean condition. Therefore, even though the oxygen concentration sensor on the upstream side of the catalyst section is eliminated, deterioration in drivability can be suppressed, and the merit of cost reduction due to the elimination of the oxygen concentration sensor on the upstream side of the catalyst section can be fully promoted.

In the present invention, the directionality confirmation unit calculates a torque opening ratio by dividing the torque generated by the internal combustion engine by a value related to the opening of a throttle valve provided in an intake pipe of the internal combustion engine. It may include a ratio calculation section, a threshold setting section that sets a threshold for the torque opening ratio, and a determination section that determines the magnitude relationship between the torque opening ratio and the threshold.

According to this, the opening/closing direction of the throttle valve is determined based on the magnitude relationship determined by the determination section between the torque opening ratio calculated by the torque opening ratio calculation section and the threshold value set by the threshold value setting section. It is possible to accurately confirm whether or not the direction of increase/decrease in the generated torque is the same as the direction of change.

In this case, the air-fuel ratio feedback restriction section sets the regulation value based on the determination result by the regulation value setting section that sets a regulation value for regulating the changeable range of the air-fuel ratio feedback coefficient, and the determination section. The control unit may also include a regulation execution unit that changes the regulation execution unit.

According to this, the regulation execution unit sets the regulation value for the changeable range of the air-fuel ratio feedback coefficient set by the regulation value setting unit based on the determination result of the magnitude relationship between the torque opening ratio and the threshold value by the determination unit. and can be changed appropriately.

In this case, the air-fuel ratio feedback unit includes an air-fuel ratio feedback learning unit that calculates a representative value of the air-fuel ratio feedback coefficient, and the regulation value setting unit is capable of changing the air-fuel ratio feedback coefficient by changing the regulation value. A regulation value modification unit may be provided that adjusts the range and modifies the air-fuel ratio feedback coefficient using the regulation value so that it approaches the representative value.

According to this, when the changeable range of the air-fuel ratio feedback coefficient is adjusted by the regulation value, the air-fuel ratio feedback coefficient is gradually modified and changed together with the regulation value so as to approach the representative value. Thereby, it is possible to stabilize the exhaust gas to an appropriate value while preventing shocks (rapid rotational speed fluctuations of the internal combustion engine) that may occur due to sudden changes in the air-fuel ratio.

In the present invention, the air-fuel ratio feedback limiting section may include a gain adjusting section that adjusts an increase/decrease rate of the air-fuel ratio feedback coefficient of the air-fuel ratio feedback section based on the determination result by the determining section.

According to this, by adjusting the rate of increase/decrease of the air-fuel ratio feedback coefficient using the gain adjustment section, the rate of change of the air-fuel ratio feedback coefficient is slowed down, and the overshoot of the air-fuel ratio feedback coefficient towards the lean side is reduced. can be done.

1 is a schematic diagram schematically showing the configuration of main parts of an internal combustion engine including an air-fuel ratio control device according to an embodiment of the present invention. 2 is a block diagram showing the main components of an ECU of the internal combustion engine of FIG. 1. FIG. FIG. 3 is a block diagram showing the configuration of a feedback coefficient calculating section in the block diagram of FIG. 2. FIG. 4 is a timing chart for explaining the operation of the feedback coefficient calculating section of FIG. 3. FIG.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the main parts of a four-stroke internal combustion engine equipped with an air-fuel ratio control device according to an embodiment of the present invention. This air-fuel ratio control device for an internal combustion engine has a function of performing air-fuel ratio feedback control based on a deviation between an excess air ratio obtained based on the oxygen concentration in the exhaust gas of the internal combustion engine and a target excess air ratio.

As shown in the figure, an engine body 1 of this internal combustion engine has an intake pipe 2 provided at an intake port, and an air cleaner 4 provided in the intake pipe 2 that controls the amount of intake air supplied to the intake port. and a throttle valve 3 that is adjusted according to the

The throttle valve 3 is provided with a throttle sensor 5 that detects the opening degree of the throttle valve 3. The throttle sensor 5 constitutes a throttle opening detection section that detects a value related to the opening of the throttle valve 3 that opens and closes the intake pipe 2 . A fuel injection valve 6 for injecting fuel is provided near the intake port of the intake pipe 2. Fuel is fed under pressure to the fuel injection valve 6 from a fuel tank (not shown) by a fuel pump.

The intake pipe 2 is provided with an intake pressure sensor 7 for detecting the intake pressure in the intake pipe 2 and an intake temperature sensor 8 for detecting the temperature of intake air in the intake pipe 2. In the exhaust pipe 10 connected to the exhaust port of the engine body 1, a catalytic converter 11 that reduces unburned components in the exhaust gas from the exhaust pipe 10 and an oxygen concentration sensor 12 that detects the oxygen concentration in the exhaust gas are provided. The oxygen concentration sensor 12 detects the oxygen concentration in the exhaust gas in the exhaust pipe 10 on the downstream side of the catalytic converter 11 as a catalyst section installed in the exhaust pipe 10 .

A spark plug 13 connected to an ignition device 14 is fixed to the engine body 1 . When the ECU (electronic control unit) 15 issues an ignition timing command to the ignition device 14, spark discharge occurs within the cylinder combustion chamber of the engine body 1.

The ECU 15 receives analog voltages indicating respective detection values of the throttle sensor 5, intake pressure sensor 7, intake temperature sensor 8, oxygen concentration sensor 12, cooling water temperature sensor 17, and atmospheric pressure sensor 20 that detects atmospheric pressure. Ru. Moreover, the above-mentioned fuel injection valve 6 is connected to the ECU 15.

A signal indicating the rotational angular position of the crankshaft 18 from the crank angle sensor 19 is further input to the ECU 15 . That is, the crank angle sensor 19 includes a plurality of convex portions provided at predetermined angle intervals (for example, 15 degrees) on the outer circumference of the rotor 19a that rotates in conjunction with the crankshaft 18, and arranged near the outer circumference of the rotor 19a. The pickup 19b detects it magnetically or optically, and the pickup 19b generates a pulse (crank signal) every time the crankshaft 18 rotates by a predetermined angle.

Specifically, the crank angle sensor 19 outputs a signal indicating the reference angle to the ECU 15 every time the piston 9 reaches the top dead center or every time the crankshaft 18 rotates 360 degrees.

FIG. 2 shows the main configuration of the ECU 15. As shown in the figure, an oxygen concentration sensor 12 that supplies a detection signal of the oxygen concentration in the exhaust gas to the ECU 15 is provided so as to be in contact with the exhaust gas of an internal combustion engine that has exhaust pulsation. A sensor element 12a as a part, and a sensor heater 12b that is adjacent to the sensor element 12a and heats the sensor element 12a.

The sensor element 12a has a resistance value that changes substantially stepwise when the exhaust gas of the internal combustion engine has an oxygen concentration near the stoichiometric value, and the detected value obtained from the resistance value is determined by the temperature of the sensor element 12a and the exhaust pulsation. It exhibits a pulse waveform with a peak value corresponding to the wave height. As the sensor element 12a, in this embodiment, a titania type sensor element, which is a resistance type oxygen sensor whose resistance value changes depending on the oxygen concentration, is used.

The ECU 15 includes a heater controller 22 that controls the sensor heater 12b, a temperature calculation unit 23 as a temperature reading unit that calculates a temperature value T indicating the temperature of the sensor element 12a, and an output signal of the sensor element 12a, which is connected to the sensor element 12a. It includes a voltage calculation unit 24 that converts into a voltage value VHG as a detected value indicating oxygen concentration.

The temperature of the sensor heater 12b is controlled by the heater controller 22 by controlling the amount of current I supplied to the sensor heater 12b from an unillustrated power source (storage battery) using pulse width modulation (PWM) using the ECU 15. Further, the temperature value T is calculated by the temperature calculation unit 23 by, for example, reading each value of the heater voltage and the current amount I applied to the sensor heater 12b with the ECU 15 to determine the resistance value of the sensor heater 12b, and calculating the resistance value of the sensor heater 12b. This is done by converting using table data or a calculation formula prepared in advance in the ECU 15 that indicates the correspondence between the heater resistance value and the temperature value T. The calculation results from the temperature calculation section 23 and the voltage calculation section 24 are supplied to an alternative value calculation section 26 of the excess rate calculation section 25, which will be described later.

The ECU 15 also includes a rotational speed calculation unit 27 that calculates the rotational speed NE and angular velocity NETC of the internal combustion engine based on the detection results of the crank angle sensor 19, and a rotational speed calculation unit 27 that calculates the rotational speed NE and angular velocity NETC of the internal combustion engine based on the detection results of the crank angle sensor 19, and a It includes an excess air ratio calculation section 25 that calculates an excess air ratio λ based on the voltage value VHG and the angular velocity NETC from the rotational speed calculation section 27.

Further, the ECU 15 includes a target value calculation unit 28 that calculates a target excess air ratio λcmd based on an estimated value of the amount of oxygen stored in the catalyst of the catalytic converter 11, a rotation speed NE from the rotation speed calculation unit 27, and a rotation speed NE from the rotation speed calculation unit 27. The basic injection amount calculation unit 29 calculates the basic injection amount BJ based on the pressure PM in the intake pipe 2 from the intake pressure sensor 7, and the excess air ratio λ calculated by the excess ratio calculation unit 25 is set as the target excess air ratio λcmd. A feedback coefficient calculation section 30 calculates a feedback coefficient K for correcting the basic fuel injection amount BJ calculated by the basic injection amount calculation section 29 in order to match the basic injection amount BJ, and calculates the fuel injection amount based on the feedback coefficient K and the basic injection amount BJ. It includes an injection amount calculation unit 31 that calculates Ti and operates the fuel injection valve 6. This injection amount calculating section 31 functions as a fuel injection amount capturing section that captures the fuel injection amount Ti supplied for one combustion of the internal combustion engine.

In the feedback coefficient calculating section 30, a feedback coefficient K is calculated by performing PID control based on the deviation between the excess air ratio λ and the target excess air ratio λcmd. Based on the fuel injection amount Ti calculated by the injection amount calculation unit 31 based on the feedback coefficient K and the basic injection amount BJ, the fuel injection valve 6 is opened for a corresponding time. Thus, an amount of fuel is injected into the cylinder combustion chamber of the engine body 1 in an amount corresponding to the feedback coefficient K of the PID control based on the comparison between the excess air ratio λ and the target excess air ratio λcmd.

Based on the voltage value VHG from the temperature calculation unit 23 and the temperature value T from the temperature calculation unit 23, the excess rate calculation unit 25 linearizes the voltage value VHG with respect to the excess air ratio while compensating for its temperature characteristics. The excess air ratio λ of the exhaust gas is calculated using the data LD obtained. However, this calculation is applied when the voltage value VHG is less than the lean side conversion limit value (threshold value LREF described later), and when the voltage value VHG is larger than this conversion limit value, the excess air ratio is calculated using another method described later. λ is found.

The excess rate calculation unit 25 includes a torque calculation unit 32 that calculates a torque value TQ that is increased or decreased in the internal combustion engine based on the crank angular speed NETC of the internal combustion engine using the method described in, for example, Japanese Patent No. 06254633, and the above-mentioned linearization conversion. A limit threshold setting unit 33 that sets a conversion limit threshold of λ, a storage unit 34 that stores data and tables necessary to calculate an alternative value R for the excess air ratio λ, and an alternative value calculation unit that calculates an alternative value R. 26.

The limit threshold value setting unit 33 sets a lean side threshold value LREF, which is a conversion limit threshold value on the lean side, and a rich side threshold value RREF, which is a conversion limit value on the rich side, as conversion limit threshold values, with respect to the voltage value VHG from the voltage calculation unit 24. Set. However, in the titania type sensor element 12a, when the temperature changes, the dynamic range of the output value (minimum value and maximum value in the linear region of the sensor output voltage) changes. Therefore, the conversion limit threshold value is changed according to the temperature value T from the temperature calculation unit 23.

The storage unit 34 stores, as data necessary for calculating the alternative value R, an execution time Ti1 of fuel injection by the fuel injection valve 6, a torque value TQ1, when the voltage value VHG from the voltage calculation unit 24 is less than or equal to the conversion limit threshold LREF. The excess air ratio λb related to the conversion limit threshold LREF is stored.

When the voltage value VHG exceeds the conversion limit threshold LREF, the substitute value calculation unit 26 calculates the substitute value R using the following formula (1), setting the execution time of the immediately preceding fuel injection as Ti2 and the immediately preceding torque value as TQ2. do.
R=((Ti1÷Ti2)÷(TQ1÷TQ2))×λb (1)

Then, when the voltage value VHG exceeds the conversion limit threshold LREF, the excess rate calculation unit 25 calculates a substitute value R for the exhaust air in place of the excess air rate λ as the linearized data LD. Regarded as excess rate λ. Note that the air-fuel ratio feedback control of the internal combustion engine described above is detailed in Japanese Patent Application No. 2020-179511.

FIG. 3 shows the configuration of the feedback coefficient calculating section 30 described above. The air-fuel ratio control device of the present embodiment includes this feedback coefficient calculating section 30 and the above-mentioned throttle sensor 5 as a throttle opening detecting section that detects a value related to the opening of the throttle valve 3 that opens and closes the intake pipe of the internal combustion engine. , and the above-mentioned torque calculation unit 32 that detects the operating state of the internal combustion engine and calculates the torque to be increased or decreased in the internal combustion engine.

As shown in FIG. 3, the feedback coefficient calculation unit 30 increases or decreases a provisional feedback coefficient MHG (adjusted as necessary and converted into a feedback coefficient K) based on feedback of the detected value of the oxygen concentration sensor 12. The air-fuel ratio feedback unit 35 is provided to set the air-fuel ratio to The air-fuel ratio feedback unit 35 includes an air-fuel ratio feedback learning unit 36 that obtains a representative value of the provisional feedback coefficient MHG.

Further, the feedback coefficient calculation section 30 performs a direction check to check whether the opening/closing direction of the throttle valve 3 and the direction of increase/decrease of the torque value TQ calculated by the torque calculation section 32 have the same direction of change. If it is confirmed that the directionality of this change is in a different relationship with section 37, the change in the provisional feedback coefficient MHG is limited to the same side as the direction in which the torque value TQ is changing, and the limited feedback coefficient K is and an air-fuel ratio feedback limiting section 38 that outputs.

The direction confirmation unit 37 includes a torque opening ratio calculation unit 39 that calculates the torque opening ratio RTOTQTH by dividing the torque value TQ by the opening TH of the throttle valve 3, and a torque opening ratio calculation unit 39 that calculates the torque opening ratio RTOTQTH by dividing the torque value TQ by the opening TH of the throttle valve 3. It includes a threshold setting unit 40 that sets a threshold TV for the torque opening ratio RTOTQTH, and a determining unit 41 that determines the magnitude relationship between the torque opening ratio RTOTQTH and the threshold TV and outputs a flag F_DR indicating the determination result. .

The air-fuel ratio feedback restriction unit 38 sets a normal regulation range for setting the changeable range of the provisional feedback coefficient MHG to a standard range, and a changeable range of the provisional feedback coefficient MHG to a range narrower than this normal regulation range. The value of the provisional feedback coefficient MHG is limited based on the regulation value setting unit 42 that sets the regulation value LV for adjusting the regulation value, the determination result F_DR by the determination unit 41, and the regulation value LV by the regulation value setting unit 42. , and a regulation execution unit 43 that converts the feedback coefficient K into a feedback coefficient K.

Furthermore, the regulation value setting section 42 activates the regulation value LV to limit the change range of the provisional feedback coefficient MHG, and also controls the regulation value modification section 44 to modify the regulation value LV so that it approaches a representative value MREFHG, which will be described later. Be prepared.

Further, the air-fuel ratio feedback restriction section 38 includes a gain adjustment section 45 that adjusts the rate of increase/decrease of the provisional feedback coefficient MHG in the air-fuel ratio feedback section 35 based on the flag F_DR indicating the determination result by the determination section 41.

FIG. 4 shows the operation of the air-fuel ratio control device. In the figure, the rotational speed NE of the internal combustion engine, the opening TH of the throttle valve 3, the torque TQ generated by the internal combustion engine, the torque opening ratio RTOTQTH obtained by dividing the torque TQ by the throttle opening TH, the feedback coefficient K, and the determination Regarding the flag F_DR indicating the determination result by the unit 41, how the flag F_DR changes depending on the processing performed by the air-fuel ratio control device in each control cycle at fixed time intervals according to the progression of time T is illustrated.

As shown in FIG. 4, for example, a state in which the opening degree TH of the throttle valve 3 exceeds an opening degree of 0.8 from the opening degree state (fully closed) when the rotational speed NE of the internal combustion engine is idling. , the rotational speed NE of the internal combustion engine changes from the rotational speed IDLE at idle to exceed 1800 rpm. In this case, hesitation (breathing of the engine) may occur in the internal combustion engine in which the torque TQ does not follow the opening TH.

At this time, if the provisional feedback coefficient MHG determined by the oxygen concentration sensor 12 downstream of the catalytic converter 11 tends to decrease in proportion to the decrease in torque TQ, then the amount of oxygen in the exhaust gas is increased by the catalytic converter 11 in the exhaust pipe 10. As a result, the excess air ratio λ downstream of the catalytic converter 11 is rich, but the excess air ratio λ upstream of the catalytic converter 11, that is, in the cylinders of the internal combustion engine, is greater than 1, that is, the internal combustion engine has a sign of hesitation. It is thought that an overlean state is occurring.

Therefore, in the air-fuel ratio control device of this embodiment, hesitation is avoided by eliminating this over-lean state. For this purpose, each time the control cycle is repeated, the feedback coefficient calculation unit 30 adjusts the provisional feedback coefficient MHG output by the air-fuel ratio feedback unit 35 as necessary, and outputs it as the feedback coefficient K.

Adjustment of this provisional feedback coefficient MHG is performed by checking by the direction checking unit 37 whether or not the opening/closing direction of the throttle valve 3 and the increasing/decreasing direction of the torque generated by the internal combustion engine have the same direction of change. If it is confirmed that the direction of change is in a different relationship, the regulation value setting unit 42 of the air-fuel ratio feedback limiting unit 38 limits the change in the provisional feedback coefficient MHG to the same direction as the direction in which the generated torque is changing. It is done by doing.

That is, the air-fuel ratio control device performs the following process every time the control cycle is repeated. First, the torque value TQ is determined by the torque calculation unit 32 based on the angular velocity NETC. Further, the throttle opening degree TH is acquired by the throttle sensor 5. Then, the feedback coefficient calculating section 30 obtains a feedback coefficient K for correcting the basic fuel injection amount BJ in the following procedure.

First, the air-fuel ratio feedback unit 35 calculates a provisional feedback coefficient MHG in order to make the excess air ratio λ calculated by the excess air ratio calculation unit 25 coincide with the target excess air ratio λcmd. Further, the directionality checking unit 37 checks whether the opening/closing direction of the throttle valve 3 and the direction of increase/decrease of the torque TQ generated by the internal combustion engine have the same directionality of change.

To confirm this, first, in the torque opening ratio calculating section 39, the torque opening ratio RTOTQTH is calculated by dividing the torque TQ calculated by the torque calculating section 32 by the throttle opening TH from the throttle sensor 5. .

Next, the threshold value setting section 40 sets a threshold value TV (for example, #0.2) based on the rotation speed NE from the rotation speed calculation section 27. This threshold value TV is preset through preliminary experiments and the like from the viewpoint of determining whether or not the above-described hesitation may occur due to the torque TQ not appropriately following the throttle opening TH.

Next, in the determination unit 41, a flag F_DR is set according to the relationship between the torque opening ratio RTOTQTH and the threshold value TV. That is, when the torque opening ratio RTOTQTH<threshold value TV, the flag F_DR is set to "1". In this case, the flag F_DR indicates that the opening/closing direction of the throttle valve 3 is different from the increasing/decreasing direction of the torque TQ generated by the internal combustion engine, and the above-mentioned hesitation is predicted.

On the other hand, when the torque opening ratio RTOTQTH is equal to or greater than the threshold value TV, the flag F_DR is set to "0". In this case, the flag F_DR confirms that the opening/closing direction of the throttle valve 3 and the increasing/decreasing direction of the torque TQ generated by the internal combustion engine are the same, that is, it indicates that hesitation is not foreseen.

Next, based on the flag F_DR from the determination unit 41, if it is confirmed that the opening/closing direction of the throttle valve 3 and the increasing/decreasing direction of the torque TQ are the same, the air-fuel ratio feedback limiting unit 38 performs air-fuel ratio feedback. The provisional feedback coefficient MHG from the unit 35 is output as is as the feedback coefficient K. That is, when the set flag F_DR is "0", the air-fuel ratio feedback limiting section 38 sets the provisional feedback coefficient MHG from the air-fuel ratio feedback section 35 within the normal regulation range, and performs basic fuel injection. It is output as a feedback coefficient K for correcting the amount BJ.

On the other hand, if it is confirmed that the opening/closing direction of the throttle valve 3 and the increasing/decreasing direction of the torque TQ are different based on the flag F_DR from the determining section 41, the air-fuel ratio feedback limiting section 38 outputs a signal from the air-fuel ratio feedback section 35. The change in the provisional feedback coefficient MHG is limited.

That is, when the set flag F_DR is "1", the air-fuel ratio feedback limiting section 38 causes the regulation value setting section 42 to change the changeable range of the provisional feedback coefficient MHG from the air-fuel ratio feedback section 35 to the normal range. A regulation value LV for regulating the range narrower than the regulation range is set.

Here, the regulation value LV is a value obtained by subtracting the variable α from the representative value MREFHG of the provisional feedback coefficient MHG obtained by learning the provisional feedback coefficient MHG in the air-fuel ratio feedback learning section 36 (=MREFHG- α) is adopted. For example, if the upper limit of the normal regulation range is 1.15 and the lower limit is 0.85, then the upper limit of 1.15 and the lower limit of 0.95 are adopted as a narrower regulation range. This lower limit value of 0.95 is set as the regulation value LV.

Next, the regulation execution unit 43 changes the lower limit value that regulates the changeable range of the air-fuel ratio feedback coefficient to the regulation value LV set by the regulation value setting unit 42. That is, the limit value that regulates the range of increase/decrease in the provisional feedback coefficient MHG is switched to the limit value that regulates the range narrower than the normal regulation range. For example, the lower limit of the normal regulatory range is 0.85, the feedback coefficient K in the previous control cycle is 0.95, and the representative value MREFHG of the provisional feedback coefficient MHG is 1.0. In this case, the value of the variable α is set to 0.05, and thus the value of the regulation value LV is changed from 0.85 to 0.95 (=MREFHG−α). As a result, when the feedback coefficient MHG is smaller than the regulation value LV, the value of the provisional feedback coefficient MHG is forcibly regulated to the regulation value LV (for example, 0.95).

Further, when the flag F_DR is "1", the gain adjustment unit 45 can reduce the rate of change of the provisional feedback coefficient MHG, that is, the amount of change for each control cycle. Specifically, the gains of the integral term and the proportional term are reduced compared to those in the previous control cycle. As a result, for example, the slope of the change curve of the provisional feedback coefficient MHG shown by the solid line A in FIG. 4 is changed to a gentler slope than the slope shown by the broken line B in FIG.

In subsequent control cycles, if the flag F_DR continues to be "1", in the successive control cycles, the regulation value modification unit 44 sequentially adjusts the regulation values via the regulation value LV set in the regulation value setting unit 42. The change range of the provisional feedback coefficient MHG is limited, and the regulation value LV is successively modified so as to approach the representative value MREFHG obtained by the air-fuel ratio feedback learning section 36.

Specifically, the value of the variable α in the regulation value LV (=MREFHG−α) is gradually decreased toward zero with each successive control cycle. Then, in successive control cycles, the regulation execution unit 43 changes the regulation value LV, which is set as the lower limit value of the above-mentioned regulation range, so that it approaches the representative value MREFHG. Accordingly, the feedback coefficient K(MHG) approaches the learning value MREFHG and is merged with the learning value MREFHG, as shown in FIG. 4.

This corrects the over-lean condition that tends to occur when performing air-fuel ratio feedback control using only the oxygen concentration sensor 12 downstream of the catalytic converter 11. Therefore, occurrence of hesitation due to overlean conditions is avoided.

As described above, according to the present embodiment, when the directionality confirmation unit 37 confirms that the opening/closing direction of the throttle valve 3 and the increasing/decreasing direction of the torque TQ are different, the air-fuel ratio feedback limiting unit 38 causes the torque TQ to increase/decrease. Since the change in the feedback coefficient K (MHG) in the same direction as the change direction is restricted, it is possible to avoid the above-mentioned overlean state from occurring. Therefore, even though the oxygen concentration sensor upstream of the catalyst is eliminated, the deterioration of drivability can be suppressed, and the cost reduction benefits due to the elimination of the oxygen concentration sensor upstream of the catalyst can be fully utilized.

Furthermore, whether or not the opening/closing direction of the throttle valve 3 in the directionality checking section 37 is different from the increasing/decreasing direction of the torque TQ is determined by the torque opening ratio RTOTQTH calculated by the torque opening ratio calculation section 39 and the threshold value setting section 40. This can be accurately confirmed based on the magnitude relationship (flag F_DR) determined by the determination unit 41 with respect to the threshold TV set by the determination unit 41.

Further, the air-fuel ratio feedback restriction section 38 sets the restriction value LV based on the determination result by the determination section 41 and the restriction value setting section 42 that sets the restriction value LV for regulating the changeable range of the provisional feedback coefficient MHG. Since the regulation execution unit 43 is provided with a regulation execution unit 43 for changing, the regulation value LV for the changeable range of the provisional feedback coefficient MHG set by the regulation value setting unit 42 is determined by the regulation execution unit 43 based on the determination result by the determination unit 41. Can be modified appropriately.

Further, the air-fuel ratio feedback unit 35 includes an air-fuel ratio feedback learning unit 36 that obtains a representative value of the provisional feedback coefficient MHG, and the regulation value setting unit 42 activates the regulation value LV to limit the change range of the provisional feedback coefficient MHG. At the same time, since the regulation value modification unit 44 is provided to modify the regulation value LV so as to approach the representative value MREFHG, the provisional feedback coefficient MHG is gradually changed to prevent shocks that may occur due to sudden changes in the air-fuel ratio. be able to.

Furthermore, the air-fuel ratio feedback limiting section 38 includes a gain adjusting section 45 that adjusts the rate of increase/decrease of the provisional feedback coefficient MHG of the air-fuel ratio feedback section 35 based on the determination result by the determining section 41. By adjusting the rate of increase/decrease of the provisional feedback coefficient MHG, for example, the rate of increase/decrease of the provisional feedback coefficient MHG can be slowed down, and excessive feedback to the lean side (overshoot) can be reduced.

As explained above, the air-fuel ratio control device of the present embodiment can avoid hesitation in situations where the occurrence of hesitation is predicted. For example, when the air-fuel ratio fluctuation shock occurs in the vehicle body, Although this control device is suitable for use in internal combustion engines of motorcycles that tend to lose balance, it can also be used in internal combustion engines of four-wheeled vehicles. The present invention is not limited to the embodiments described above, and various design changes can be made without departing from the scope of the present invention as set forth in the claims.

1... Engine body, 2... Intake pipe, 3... Throttle valve, 4... Air cleaner, 5... Throttle sensor, 6... Fuel injection valve, 7... Intake pressure sensor, 8... Intake temperature sensor, 9... Piston, 10... Exhaust pipe , 11... Catalytic converter, 12... Oxygen concentration sensor, 12a... Sensor element, 12b... Sensor heater, 13... Spark plug, 14... Ignition device, 15... ECU (electronic control unit), 17... Cooling water temperature sensor, 18... Crank Axis, 19...Crank angle sensor, 19a...Rotor, 19b...Pickup, 20...Atmospheric pressure sensor, 22...Heater controller, 23...Temperature calculation section, 24...Voltage calculation section, 25...Excess rate calculation section, 26...Alternative Value calculation section, 27... Rotation speed calculation section, 28... Target value calculation section, 29... Basic injection amount calculation section, 30... Feedback coefficient calculation section, 31... Injection amount calculation section, 32... Torque calculation section, 33... Limit threshold value Setting section, 34... Storage section, 35... Air-fuel ratio feedback section, 36... Air-fuel ratio feedback learning section, 37... Direction checking section, 38... Air-fuel ratio feedback limiting section, 39... Torque opening ratio calculation section, 40... Threshold value Setting section, 41... Judgment section, 42... Regulation value setting section, 43... Regulation execution section, 44... Regulation value modification section, 45... Gain adjustment section.

Claims (5)

a throttle opening detection unit that detects a value related to the opening of a throttle valve that opens and closes an intake pipe of the internal combustion engine;
an air-fuel ratio feedback section configured to increase or decrease an air-fuel ratio feedback coefficient based on feedback of a detected value of an oxygen concentration sensor provided downstream of a catalyst section of an exhaust pipe of the internal combustion engine;
a torque calculation unit that detects the operating state of the internal combustion engine and calculates the torque generated by the internal combustion engine;
a directionality checking unit that checks whether the torque increases or decreases when the throttle valve opens ;
and an air-fuel ratio feedback limiting section configured to limit the setting of the air-fuel ratio feedback coefficient that reduces the torque when the directionality confirmation section confirms that the torque decreases. Air-fuel ratio control device. The directionality confirmation unit is
a torque opening ratio calculation unit that calculates a torque opening ratio by dividing the torque generated by the internal combustion engine by a value related to the opening of a throttle valve provided in an intake pipe of the internal combustion engine;
a threshold setting unit that sets a threshold for the torque opening ratio;
The air-fuel ratio control device according to claim 1, further comprising a determination unit that determines a magnitude relationship between the torque opening ratio and the threshold value. The air-fuel ratio feedback limiting section includes a regulation value setting section that sets a regulation value for regulating a changeable range of the air-fuel ratio feedback coefficient;
The air-fuel ratio control device according to claim 2, further comprising a regulation execution unit that changes the regulation value based on a determination result by the determination unit. The air-fuel ratio feedback unit includes an air-fuel ratio feedback learning unit that calculates a representative value of the air-fuel ratio feedback coefficient,
The regulation value setting unit changes the regulation value to adjust a changeable range of the air-fuel ratio feedback coefficient, and adjusts the air-fuel ratio feedback coefficient to approach the representative value via the regulation value. The air-fuel ratio control device according to claim 3, further comprising a value modification section. 5. The air-fuel ratio feedback limiting section includes a gain adjusting section that adjusts an increase/decrease rate of the air-fuel ratio feedback coefficient of the air-fuel ratio feedback section based on the determination result by the determining section. The air-fuel ratio control device according to item 1.

Images