JP2018204576A - Engine controller and engine control program - Google Patents

Abstract

To prevent engine stall and maintain an output air-fuel ratio even in highland traveling.SOLUTION: An engine controller comprises: a determination unit 110 configured to determine whether a current operation region is a feedback region or not; a feedback control unit 120 configured to, when it is determined to be the feedback region, calculate a feedback correction coefficient for making an actual air-fuel ratio approach a target air-fuel ratio; a correction coefficient learning unit 140 configured to, when it is determined to be a non-feedback region, learn a second correction coefficient; and a fuel injection control unit 150 configured to, based on at least the feedback correction coefficient, the second correction coefficient and a basic injection amount, obtain a fuel injection amount to send a corresponding fuel injection control signal to an injector 40.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an engine control device and an engine control program that enable stable high-altitude traveling by maintaining an output air-fuel ratio and preventing occurrence of engine stall.

Conventionally, a control device has been proposed in which appropriate fuel injection can be performed in a region other than the O ₂ feedback control region. For example, in a load region other than the O ₂ feedback control region, an air-fuel ratio learning control device that controls the fuel injection amount using a learned value in an O ₂ feedback region adjacent to the load region has been proposed (patent) Reference 1).

According to this device, it is possible to reduce the cost by eliminating the need for an intake pressure sensor and an atmospheric pressure sensor, and to perform air-fuel ratio control by fuel injection that reflects changes with time of the internal combustion engine in a region other than the O ₂ feedback control region. did it.

  Further, learning correction coefficients for a plurality of modes in which the reference value for each engine load is determined according to altitude are stored, and when an instruction is given from the learning value change instruction means, the control unit An apparatus for replacing the reference value with the learning value of the learning correction coefficient so far has also been proposed (see Patent Document 2). According to this apparatus, it was possible to change the learning value so far to a learning value that is highly matched by a user operation.

Japanese Patent No. 5411728 (page 2-11, FIG. 6) JP2011-157830 (page 2-9, Fig. 2)

However, according to the prior art described in Patent Document 1 and Patent Document 2, in the O ₂ feedback region, O ₂ feedback control is performed so as to approach the target air-fuel ratio based on the oxygen concentration detected by the O ₂ sensor. However, in the non-feedback region that is a region other than the O ₂ feedback region, the feedback correction coefficient is fixed to “1.0” and feedback control is not performed.

  However, when driving in a non-feedback area where the air becomes thin when driving at high altitude and the throttle opening is increased, if feedback control is not performed, problems such as engine stall occur and stabilize. May not be able to run smoothly. Further, according to the apparatus described in Patent Document 2, the reference value of the learning correction coefficient is determined for a plurality of modes according to altitude, and the reference value of the mode selected according to the specific operation pattern of the accelerator grip is Therefore, it is not assumed that fine air-fuel ratio control is performed according to altitude.

  The present invention has been made to solve such a conventional problem, and an engine control device and an engine control program that enable stable running while maintaining an output air-fuel ratio even in a high altitude where air is lean The purpose is to provide.

In order to achieve the above object, an engine control apparatus of the present invention is an engine control apparatus capable of calculating a feedback correction coefficient for asymptotically approaching an actual air-fuel ratio measured by an oxygen sensor to a target air-fuel ratio,
A correction coefficient learning unit that learns a second correction coefficient that is a fuel injection amount correction coefficient for correcting the fuel injection amount together with the feedback correction coefficient when the current operation region is a non-feedback region other than the feedback region;
A fuel injection control unit that obtains a fuel injection amount based on the basic injection amount, the feedback correction coefficient, and the second correction coefficient and provides a corresponding fuel injection control signal to the fuel injection device;
The correction coefficient learning unit
The second correction coefficient is changed and controlled according to the output signal of the oxygen sensor at the start of learning,
The second correction coefficient at the time when the output signal crosses the threshold value corresponding to the stoichiometric air-fuel ratio, and the previous second correction coefficient is updated and stored.

A determination unit that determines whether or not the current operation region is a feedback region;
When it is determined that the feedback region, the engine control device may include a feedback control unit that calculates the feedback correction coefficient.

More specifically, the fuel injection control unit
When the feedback region is determined, the fuel injection amount is obtained by multiplying the addition result of the feedback correction coefficient and the second correction coefficient by the basic injection amount,
When it is determined as the non-feedback region, the fuel injection amount is obtained by multiplying the addition result obtained by adding the feedback correction coefficient and the second correction coefficient by the basic injection amount and a preset constant. The preset constant is, for example, a constant “1.168” obtained by dividing the theoretical air-fuel ratio by the output air-fuel ratio.

The correction coefficient learning unit
When it is determined at the start of learning that the stoichiometric air-fuel ratio is rich based on the output signal of the oxygen sensor, a target A / F correction value that is a correction amount corresponding to the target air-fuel ratio is associated with the output air-fuel ratio. A decreasing function that gradually decreases from the value to the value corresponding to the theoretical air-fuel ratio,
From the time when the target A / F correction value reaches a value corresponding to the theoretical air-fuel ratio, the second correction coefficient is gradually decreased, and when the output signal becomes equal to or less than the threshold, the decrease of the second correction coefficient is stopped. A learning function for updating and storing the second correction coefficient up to that time with the second correction coefficient at the time of decrease stop;
A return function for returning the target A / F correction value to a value corresponding to the output air-fuel ratio after storing the second correction coefficient.

In addition, the learning function by other operation modes is
In the process of decreasing the target A / F correction value by the decrease function, if the output signal falls below the threshold value, the decrease function is stopped and the target A / F correction value and the stoichiometric air / fuel ratio when the decrease function is stopped are supported. Increasing the second correction coefficient by an amount corresponding to the difference from the value to be
It is preferable that the second correction coefficient up to that point is updated and stored with the increased second correction coefficient.

According to another operation mode, the correction coefficient learning unit
At the start of learning, when it is determined that the lean state with respect to the theoretical air-fuel ratio is determined based on the output signal of the oxygen sensor, a target A / F correction value that is a correction amount corresponding to the target air-fuel ratio is associated with the output air-fuel ratio. A control function for gradually decreasing the value from the value to a value corresponding to the theoretical air-fuel ratio and gradually increasing the second correction coefficient;
A learning function for updating and storing the second correction coefficient up to that time with the second correction coefficient when the output signal becomes equal to or greater than a threshold value by the control function;
And a return function for returning the target A / F correction value to a value corresponding to the output air-fuel ratio.

According to still another operation mode, the correction coefficient learning unit
The configuration further includes a correction coefficient increasing function for increasing the second correction coefficient by a predetermined value when the output signal of the oxygen sensor crosses the threshold value a predetermined number of times within a predetermined time from the start of learning.

The engine control program of the present invention is a program for operating an engine control device capable of calculating a feedback correction coefficient for asymptotically approaching a target air-fuel ratio from an actual air-fuel ratio measured by an oxygen sensor,
A correction coefficient learning process for learning a second correction coefficient for correcting the fuel injection amount together with the feedback correction coefficient when the current operation area is a non-feedback area other than the feedback area;
A program for causing a computer to execute a fuel injection control process for obtaining a fuel injection amount based on a basic injection amount, a feedback correction coefficient, and a second correction coefficient and providing a corresponding fuel injection control signal to the fuel injection device. Yes,
The correction coefficient learning process
The second correction coefficient is changed and controlled according to the output signal of the oxygen sensor at the start of learning, and the second correction coefficient at the time when the output signal crosses the threshold value corresponding to the theoretical air-fuel ratio. An engine control program that updates and stores coefficients.

  According to the present invention, it is possible to obtain an effect of enabling stable traveling while maintaining the output air-fuel ratio even in a highland where air is lean.

1 is a schematic explanatory diagram of a configuration outline of an engine 1. FIG. 2 is a functional configuration diagram of a control device 100. FIG. It is a flowchart for demonstrating whole operation | movement. It is explanatory drawing of the driving map. 2 is a hardware configuration diagram of a control device 100. FIG. It is explanatory drawing of the output characteristic of the oxygen sensor. It is a flowchart for demonstrating learning operation | movement. It is a flowchart for demonstrating learning operation | movement. 6 is a timing chart showing an operation example 1; 10 is a timing chart showing an operation example 2; 10 is a timing chart showing an operation example 3; 10 is a timing chart showing an operation example 4;

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment of the present invention described below is an example, and the present invention is not limited to this embodiment, and various modifications, changes, and the like are possible with respect to configuration examples, information examples, and the like of the present embodiment. In the following, the output air-fuel ratio at which the engine output becomes maximum is “12.5”, and the stoichiometric air-fuel ratio (stoichiometry) is “14.6”.

(Outline of engine 1)
FIG. 1 is a schematic configuration diagram of a control system including an engine 1 and a control device 100. The engine 1 includes a cylinder 2 and a piston 3 that is fitted inside the cylinder 2 so as to be slidable in the vertical direction. One end side of the connecting rod 4 is connected to the piston 3, and the other end side of the connecting rod 4 is connected to the crankshaft 5. A flywheel 7 is rotatably fixed to the end of the crankshaft 5 on the transmission (not shown) side. In a predetermined angular region on the outer periphery of the flywheel 7, a reluctor (projection) 20 made of a magnetic material is formed.

  The electromagnetic pickup 22 arranged to face the reluctor 20 outputs a positive voltage pulse when the reluctator 20 approaches, and outputs a negative voltage pulse when the reluctor 20 moves away. When a known waveform shaping circuit shapes the waveform so that one rectangular pulse is output based on the positive and negative bipolar pulse signals, one rectangular pulse is output each time the flywheel 7 rotates once. Therefore, in one cycle of “intake → compression → combustion → exhaust → intake”, the crankshaft 5 rotates 720 °, so that the electromagnetic pickup 22 outputs a two-pulse rectangular signal (engine rotation signal) in one cycle.

Based on the engine rotation signal from the electromagnetic pickup 22, the rotation speed of the engine 1 can be obtained. Further, the position where the reluctator 20 is formed on the outer periphery of the flywheel 7 is set to an appropriate angular region, and the timing at which fuel ignition is performed by giving an ignition control signal to the spark plug 45 based on the signal from the electromagnetic pickup 22 is set as a desired timing. be able to.

  An intake pipe 50 and an exhaust pipe 60 are connected to the cylinder head at the top of the cylinder 2. An intake passage 51 is formed inside the intake pipe 50 for taking in fresh air from the outside into the combustion chamber 70. In addition, an air cleaner 32 for removing fresh dust and the like, a throttle valve 24 for adjusting the intake amount of fresh air, and an injector 40 for performing fuel injection are arranged in the intake passage 51 from the upstream side. ing. And the timing which takes in fresh air in the combustion chamber 70 is controlled by the valve opening / closing operation | movement of the intake valve 12 urged | biased by the spring not shown in the valve closing direction.

The spark plug 45 is disposed on the top of the cylinder head so that its tip faces the combustion chamber. Further, a throttle opening sensor 26 for detecting the opening of the throttle valve is provided. Although not shown, the fuel stored in the fuel tank is supplied to the injector 40 via the supply hose, while the surplus fuel is recovered to the fuel tank via the recovery hose. The fuel pressurized to a predetermined pressure is supplied.

  On the other hand, an exhaust passage 61 for exhausting exhaust from the combustion chamber 70 is formed inside the exhaust pipe 60. A catalytic device 30 for purifying exhaust gas is disposed downstream of the exhaust passage 61, and an oxygen sensor 28 for detecting the concentration of oxygen remaining in the exhaust gas is provided on the upstream side of the catalytic device 30. It is also possible to employ a configuration in which the silencer is silenced after the exhaust gas is purified by the catalyst device 30. The timing of exhaust emission from the combustion chamber 70 is controlled by the valve opening / closing operation of the exhaust valve 10 that is biased in the valve closing direction by a spring (not shown).

FIG. 6 is an explanatory diagram of output characteristics of the oxygen sensor 28 (also referred to as “O ₂ sensor”). The direction in which the horizontal axis in FIG. 6 extends is the large air-fuel ratio direction, and the vertical axis is the oxygen sensor output signal (VS). As the air-fuel ratio increases, the oxygen sensor output signal (VS) decreases, and when the oxygen sensor output signal (VS) is greater than or equal to the rich determination threshold, it is determined that the engine is in a rich state, while the oxygen sensor output signal (VS When VS) is equal to or less than the lean determination threshold, it is determined that the vehicle is lean. The output signal (VS) of the oxygen sensor 28 changes rapidly in the vicinity of “14.6” where the air-fuel ratio is the stoichiometric air-fuel ratio. As described above, since the oxygen sensor output signal (VS) changes according to the air-fuel ratio, the actual air-fuel ratio can be detected by acquiring VS.

Further, by detecting VS, it can be determined whether the engine is in a rich state or a lean state with respect to the stoichiometric air-fuel ratio. Since VS changes abruptly in the vicinity of the theoretical air-fuel ratio, the accuracy of determining rich and lean with respect to theoretical air fuel is good.

The control device 100 that controls the operation of the engine 1 receives the outputs of the throttle opening sensor 26, the electromagnetic pickup 22, and the oxygen sensor 28. The throttle opening sensor 26 outputs a throttle opening signal indicating the opening of the throttle valve, and the electromagnetic pickup 22 outputs a rectangular pulse signal corresponding to the engine rotation described above. The O ₂ sensor 28 outputs an O ₂ sensor output signal indicating the concentration of oxygen remaining in the exhaust gas. On the other hand, the control device 100 outputs a fuel injection control signal for driving and controlling the injector 40 and an ignition control signal for controlling ignition of the spark plug 45.

The control device 100 performs fuel injection control (injection amount, injection timing) by the injector 40, ignition timing control by the spark plug 45, and the like based on the throttle opening signal, the engine rotation, the O ₂ sensor output signal, and the like. Then, the reciprocating motion of the piston 1 in the vertical direction in the cylinder 2 is converted into the rotational motion of the crankshaft 5. The rotational movement of the crankshaft 5 is transmitted to drive wheels via a transmission (not shown), and the vehicle (two wheels, four wheels) moves forward by repeating the process of “intake → compression → combustion → exhaust”.

FIG. 1 is an example of the configuration of the engine 1 and the control device 100. For example, the control device 100 includes the intake air temperature of the engine 1 in addition to the throttle opening signal, the engine rotation, and the O ₂ sensor output signal. The engine 1 can also be controlled with reference to the coolant temperature or the like. That is, in order to improve drivability, it is possible to calculate engine parameters such as an air-fuel ratio correction coefficient by increasing the types of sensors. Moreover, although the engine 1 which has the process of 4 cycles with a single cylinder is assumed, an appropriate thing can be employ | adopted for a cylinder number and a cylinder arrangement | sequence aspect.

(Functional configuration of control device 100)
FIG. 2 is a functional configuration diagram of the control device 100. The control device 100 includes a determination unit 110, a feedback control unit 120, a storage unit 130, a correction coefficient learning unit 140, a fuel injection control unit 150, and an ignition control unit 160. The storage unit 130 includes a program 132, a map 134, a nonvolatile storage area 136, and a work area 138. Each function can implement a series of controls by executing the program 132. The work area 138 is a temporary storage area for temporarily storing parameters such as correction coefficients in the calculation process, and the non-volatile storage area 136 stores parameters such as feedback correction coefficients and second correction coefficients in a non-volatile manner. This is a storage area for storing information automatically.

  FIG. 4 is an explanatory diagram of the map 134. The horizontal axis is the engine speed (rpm), and the vertical axis is the throttle opening (%). A region where the engine speed is less than NEH (rpm) and the throttle opening is less than THH (%) is a feedback region. On the other hand, the region where the engine speed is NEH (rpm) or more or the throttle opening is THH (%) or more is a non-feedback region which is a region other than the feedback region. That is, the map 134 indicating the entire operating state is composed of a feedback region and a non-feedback region. FIG. 4 is an example of the operation map, and the boundary line of the region does not have to be a straight line, and the feedback region does not necessarily have to be a square shape, and hysteresis may be provided on the boundary line.

Returning to FIG. 2, the description will be continued. The determination unit 110 is stored in the storage unit 130 based on the throttle detection signal corresponding to the detected value of the throttle opening by the throttle opening sensor 26 and the engine rotation detection signal corresponding to the engine rotation detection by the electromagnetic pickup 22. With reference to map 134, it is determined whether the current driving region is a feedback region or a non-feedback region other than this. Specifically, information on the throttle opening and the engine speed is acquired from the throttle opening sensor 26 and the electromagnetic pickup 22, and the engine speed is less than NEH (rpm) with reference to the map 134 in FIG. When the throttle opening is less than THH (%), it is determined that the current operation region is a feedback region, while in other cases, the current operation region is a non-feedback region. judge.

  The feedback control unit 120 obtains a control deviation between the actual air-fuel ratio according to the output signal VS of the oxygen sensor 26 that outputs an output signal according to the actual air-fuel ratio and the target air-fuel ratio (also referred to as a target A / F value). The air-fuel ratio feedback correction coefficient (hereinafter referred to as “O2FB correction coefficient”) is obtained so that the obtained control deviation becomes zero. The target air-fuel ratio is stored at a specific address in the non-volatile storage area 136 that should be referred to by the program 132 stored in the storage unit 130, for example. The feedback control unit 120 recognizes the target air-fuel ratio with reference to this. This target air-fuel ratio is a value that makes a fuel injection amount, which will be described later, a desired value. The feedback control unit 120 updates and stores the calculated O2FB correction coefficient in the nonvolatile storage area 136 so that it can be read.

  The correction coefficient learning unit 140 uses the initial value of the target air-fuel ratio as the output air-fuel ratio, and based on the sensor output signal VS of the oxygen sensor 26 and the like, a second correction coefficient (a second correction coefficient that is different from the O2FB correction coefficient ( (Hereinafter referred to as O2FF correction coefficient). More specifically, the correction coefficient learning unit 140 sequentially updates the second correction coefficient to a new value in real time, and stores it in the nonvolatile storage area 136 of the storage unit 130. This learning value is held until the next control. The O2FF correction coefficient stored and held in the non-volatile storage area 136 is read out at the next control and becomes the initial value of the O2FF correction coefficient. Details of the learning method will be described later.

  The fuel injection control unit 150 obtains the fuel injection amount and gives a corresponding fuel injection control signal to the fuel injection device. That is, the fuel injection control unit 150 obtains the fuel injection amount, and gives a fuel injection control signal corresponding to the obtained fuel injection amount to the injector 40. Thereby, the injector 40 injects fuel with the fuel injection amount according to the fuel injection control signal. When the operation region is the feedback region, the fuel injection control unit 150 obtains the fuel injection amount based on the “O2FB correction coefficient” and the “basic injection amount”, and a fuel injection control signal corresponding to the obtained fuel injection amount Is given to the injector 40.

On the other hand, when the operation region is the non-feedback region, the fuel injection control unit 150 determines the fuel injection amount based on the “O2FB correction coefficient”, the “O2FF correction coefficient”, and the “basic injection amount”, and determines the calculated fuel. A fuel injection control signal corresponding to the injection amount is given to the injector 40. Here, “FB” means feedback, and “FF” means feed forward. The basic fuel injection amount is a constant fuel injection amount that is a base for calculating the fuel injection amount.

  Specifically, when the current operation region is the feedback region, the fuel injection control unit 150 calculates the fuel calculated by “fuel injection amount = basic injection amount × 100 (%) × (O2FB correction coefficient + O2FF correction coefficient)”. A fuel injection control signal corresponding to the injection amount is output. On the other hand, when the current operation region is the non-feedback region, the fuel injection control unit 150 determines that “fuel injection amount = basic injection amount × target A / F correction value × (O2FB correction coefficient + O2FF correction coefficient); From “F correction value = (14.6 / target A / F value) × 100 (%), target A / F value = 12.5 (output air-fuel ratio)”, “fuel injection amount = basic injection amount × 116.8”. A fuel injection control signal corresponding to the fuel injection amount calculated by “(%) × (O2FB correction coefficient + O2FF correction coefficient)” is output. Thus, the target A / F correction value is an air-fuel ratio correction value for the target air-fuel ratio, and is a value determined based on the target air-fuel ratio (target A / F value). The correction coefficient learning unit 140 performs learning by performing increase / decrease control on the target A / F value to increase / decrease the target A / F correction value.

Since the calculation is 100 (%) = 1.0, in the “feedback region”, “fuel injection amount = basic injection amount × 1.0 × (O2FB correction coefficient + O2FF correction coefficient)”. On the other hand, in the “non-feedback region”, “fuel injection amount = basic injection amount × 1.168 × (O2FB correction coefficient + O2FF correction coefficient)”. That is, “1.168” is a constant for setting the target A / F correction value to a value corresponding to the output air-fuel ratio, and “theoretical air-fuel ratio / output air-fuel ratio = 1.168”.

For example, the fuel injection control unit 150 divides fuel in half in each of the compression stroke and the exhaust stroke until the stroke determination of the engine 1 is completed, and performs fuel injection collectively in the exhaust stroke after the stroke determination is completed. Thus, the fuel injection control signal is controlled to be given to the injector 40 so as to perform the fuel injection control.

  The ignition control unit 160 generates an ignition control signal based on an engine speed signal that is an output signal of the electromagnetic pickup 22 and supplies the ignition control signal to the ignition plug 45. Upon receiving this ignition control signal, the spark plug 45 ignites the air-fuel mixture introduced into the combustion chamber 70.

(Hardware configuration diagram)
FIG. 5 is a hardware configuration diagram of the control device 100. The control device 100 includes an A / D converter 250, a CPU 200, a ROM 210, a RAM 220, a flash memory 230, and a D / A converter 260. The A / D converter 250 performs analog / digital conversion of a throttle opening detection signal from the throttle opening sensor 26, an engine rotation detection signal from the electromagnetic pickup 22, and an oxygen sensor output signal from the oxygen sensor 28. Send to CPU200.

On the other hand, the D / A converter 260 converts the fuel injection control signal to the injector 40 output from the CPU 200 and the ignition control signal to the ignition plug 45 from digital to analog, and sends them to the injector 40 and the ignition plug 45.

  The CPU 200 reads out the program 132 recorded in the ROM 210 and executes the program 132 while using the work area 138 and the like formed in the RAM 220. During the execution process, the calculated correction coefficient and the like are updated and stored in the nonvolatile storage area 136 of the flash memory 230. Further, the map 134 stored in the flash memory 230 is used by the CPU 200 to determine whether or not the current operation region is the feedback region. In addition, the CPU 200 recognizes the elapse of a predetermined time based on a time-out using a timer 205 inside itself.

  A processor such as a CPU 200 or a DSP (Digital Signal Processor) executes a program 132 recorded on a recording medium such as a ROM 210, whereby the determination unit 110, the feedback control unit 120, the correction coefficient learning unit 140, and the correction coefficient learning unit 140 illustrated in FIG. The fuel injection control unit 150 and the ignition control unit 160 can be realized. Further, the ROM 210, the RAM 220, and the flash memory 230 implement the storage unit 130.

(Description of overall operation)
The overall operation will be described with reference to FIG. First, in step S300, the determination unit 110 acquires the value of the throttle opening degree detection signal from the throttle opening degree sensor 26, and substitutes this into the variable TH as the opening amount of the throttle 24. Next, in step S310, the determination unit 110 calculates the engine speed based on the engine rotation detection signal from the electromagnetic pickup 22, and substitutes the calculation result for the variable NE. Since the engine rotation detection signal from the electromagnetic pickup 22 is output as one pulse rectangular signal every time the flywheel 7 makes one rotation, for example, by calculating the arrival number of the first pulse signal per 60 seconds, Calculate the rotation speed. The method for calculating the engine speed is not limited to this.

  Next, in step S320, the determination unit 110 refers to the variables TH, NE, and the map 134 to determine whether the current operation region is a feedback region or a non-feedback region other than this. When the two-dimensional position corresponding to the variable TH and the variable EN substituted in Step S300 and Step S310 is plotted in the feedback region on the map 134 of the horizontal axis NE and the vertical axis TH, the determination unit 110 On the other hand, it is determined that the region is a feedback region (Yes in step S330). On the other hand, if the region is plotted in other regions, it is determined that the region is a non-feedback region (No in step S330).

  When the process proceeds to step S340, the feedback control unit 120 obtains the O2FB correction coefficient so that the control deviation between the target air-fuel ratio and the actual air-fuel ratio becomes zero, stores it in the nonvolatile storage area 136, and ends. To do. On the other hand, when the process proceeds to step S350, the correction coefficient learning unit 140 increases / decreases the O2FF correction coefficient that is the second correction coefficient, performs learning, and ends. The learned value is updated and stored, and is read and used when the next control is executed. The above is an overview of the overall operation.

(Learning operation example)
Next, an example of the learning operation will be described with reference to FIGS. The learning operation shown in FIGS. 7 and 8 is an example of the learning operation performed by the correction coefficient learning unit 140 according to the embodiment of the present invention, and the O2FF correction coefficient may be learned by other methods. In the following operation, the output signal of the oxygen sensor 28 is set to “VS”, and the threshold value for determining whether the stoichiometric air-fuel ratio is lean or rich is set to “O ₂ TH”. Further, the variable corresponding to the target A / F correction value is set to AFH, and its initial value is set to a value corresponding to the output air-fuel ratio. The operations of FIGS. 7 and 8 are executed by the correction coefficient learning unit 140.

First, in response to the establishment of a highland fuel correction execution condition (learning start condition) to be described later, in step S700, it is determined whether or not a predetermined time has elapsed since the rich state or the lean state has continued. If it is determined that the state where the VS is equal to or higher than the rich threshold is continued for a predetermined time, or the state where the VS is equal to or lower than the lean threshold is continued for a predetermined time, “Yes” is obtained in step 700. The predetermined time is a time set for the output of the oxygen sensor 28 to be stabilized. If it is determined that the predetermined time has not elapsed (No in step S700), it is determined in step S705 whether or not VS has changed in a predetermined pattern. If it is determined that there is no change in the predetermined pattern (No in step S705), the process returns to step S700 and the determination of the elapse of the predetermined time is continued.

On the other hand, if it is determined that the change has occurred (Yes in step S705), the process proceeds to step S710, the O2FF correction coefficient is increased by a predetermined amount, branching to the connector B, and learning is once ended. The operation in step S710 will be described later as “Operation Example 4”.

  If it is determined that the predetermined time has elapsed (Yes in step S700), it is determined in step 715 whether or not VS is equal to or less than the lean determination threshold value. If it is determined that VS is equal to or less than the lean determination threshold value, that is, if it is determined that the vehicle is lean, the process branches to connector C in FIG.

In step S810, the variable AHF indicating the target A / F correction value (target air-fuel ratio correction value) is decreased by Δh1, and the variable O2FF indicating the O2FF correction coefficient is increased by Δh4. As described above, the initial value of the variable AHF is a value corresponding to the output air-fuel ratio. In step S820, it is determined whether or not the variable AHF is equal to a reference value (a value corresponding to the theoretical air-fuel ratio). If it is determined that the variable AHF is equal (Yes in step S820), the process proceeds to step S830. On the other hand, when it is determined that the variable AHF is not equal to the reference value (No in step S820), the process returns to step S810. Next, in step S830, the variable O2FF indicating the O2FF correction coefficient is increased by Δh4. Next, in Step S840, when it is determined that VS is smaller than the threshold value O ₂ TH (No in Step S840), the process returns to Step S830 again. On the other hand, when it is determined that VS is equal to or higher than the threshold value O ₂ TH (Yes in step S840), the process jumps to the connector D in FIG.

  After jumping to the connection D, learning of the O2FF correction coefficient as the second correction coefficient is executed by updating and storing the variable O2FF in the nonvolatile storage area 136 in step S750. The learning value is read as the initial value for the next control. Next, in step S755, the variable AFH is increased by Δh1 in order to return it to the initial value. In step S760, it is determined whether or not the variable AFH has become a value corresponding to the output air-fuel ratio.

If it is determined in step S760 that the variable AFH is not a value corresponding to the output air-fuel ratio (No in step S760), the process returns to step S755, and the variable AHF is increased again. On the other hand, if it is determined that the variable AFH has become equal to the value corresponding to the output air-fuel ratio (Yes in step S760), the control is temporarily terminated.

A series of processing in steps S700, S715, S810, S820, S750, S755, and S760 corresponds to “Operation Example 3” described later. In other words, if the output signal VS of the oxygen sensor 28 is equal to or less than the lean determination threshold at the start of learning after the predetermined time has elapsed, the target A / F correction value is changed from a value corresponding to the output air-fuel ratio to a value corresponding to the stoichiometric air-fuel ratio. Decrease gradually and increase O2FF correction factor gradually. When the target A / F correction value becomes the reference value, the decrease of the target A / F correction value is stopped and the O2FF correction coefficient is gradually increased.

Then, learning is performed to update the O2FF correction coefficient up to that time with the O2FF correction coefficient when VS becomes equal to or greater than the threshold value O ₂ TH, and the target A / F correction value is returned to a value corresponding to the output air-fuel ratio.

If it is determined in step S715 that VS is greater than the lean determination threshold value (No in step S715), that is, in the rich state, the process proceeds to step S720, and the variable AFH is decreased by Δh1. In other words, considering the determination result in step S700, if it is determined that VS is equal to or greater than the rich determination threshold, the process proceeds to step S720, and the variable AFH is decreased by Δh1. Next, in step S730, it is determined whether or not VS is equal to or less than the threshold value O ₂ TH. If it is determined that VS is equal to or less than the threshold value O ₂ TH (Yes in step S730), the process proceeds to step S765.

On the other hand, if it is determined in step S730 that VS is greater than the threshold value O ₂ TH (No in step S730), whether or not the variable AFH is equal to the reference value (a value corresponding to the theoretical air-fuel ratio) in step S735. If it is determined whether or not they are equal (Yes in step S735), the process proceeds to step S740. On the other hand, when it is determined that the value of the variable AFH is not equal to the reference value (No in step S735), the process returns to step S720, and the variable AFH reduction process is repeated.

That is, when VS is larger than the threshold value O ₂ TH (No in step S730), the value of the variable AFH is decreased until it reaches the reference value. On the other hand, if it is determined that VS is equal to or lower than the threshold value O ₂ TH in the process of decreasing the variable AFH (Yes in step S730), the process proceeds to step S765. In step S765, in step S765, the variable O2FF is increased by the difference value Δh3 between the reference value of the target A / F correction value and the value of the variable AFH at that time.

Next, the process proceeds to step S750, where the variable O2FF indicating the O2FF correction coefficient is updated and stored in the nonvolatile storage area 136, thereby learning the O2FF correction coefficient. The learning value is read as the initial value for the next control. Next, the process proceeds to step S755, where Δh1 is increased to return the variable AFH. In step S760, it is determined whether the variable AFH is equal to the initial value, that is, the value corresponding to the output air-fuel ratio. If it is determined in step 760 that the variable AFH is not equal to the value corresponding to the output air-fuel ratio (No in step S760), the process returns to step S755. On the other hand, if it is determined that the variable AFH has become equal to the value corresponding to the output air-fuel ratio (Yes in step S760), the control is temporarily terminated.

A series of processing in steps S700, S715, S720, steps S765, S750, S755, and S760 corresponds to “operation example 2” described later. That is, in steps S700, S715, S720, S730, and S765, when the output signal VS of the oxygen sensor 28 is greater than or equal to the rich determination threshold at the start of learning after the lapse of a predetermined time, the target A / F correction value is reduced. When VS becomes equal to or less than the set threshold value O ₂ TH, the decrease of the target A / F correction value is stopped, and the variable is set by the difference between the reference value of the target A / F correction value and the value of the variable AFH at that time. Increase O2FF. Then, learning for updating and storing the O2FF correction coefficient up to that time is performed with the O2FF correction coefficient at that time, and the target A / F correction value is returned to the output theoretical ratio.

When the process proceeds from Yes in step S735 to step S740, the value of the variable O2FF is decreased by Δh2, and in step S745, it is determined whether VS is equal to or less than the threshold value O ₂ TH. When it is determined that VS is equal to or less than the threshold value O ₂ TH (Yes in step S745), the process proceeds to step S750. On the other hand, when it is determined that VS is larger than the threshold value O ₂ TH (No in step S745), the process returns to step 740 and the variable O2FF is decreased by Δh2.

In step S750, the variable O2FF is updated and stored in the nonvolatile storage area 136, thereby learning the O2FF correction coefficient as the second correction coefficient. The learning value is read as the initial value for the next control.

Next, in step S755, in order to return the variable AFH to the initial value, it is increased by Δh1, and in step S760, it is determined whether or not the variable AFH is equal to the initial value, that is, a value corresponding to the output air-fuel ratio. . If it is determined in step S760 that the variable AFH is not equal to the value corresponding to the output air-fuel ratio (No in step S760), the process returns to step S755. On the other hand, if it is determined that the variable AFH has become equal to the value corresponding to the output air-fuel ratio (Yes in step S760), the control is temporarily terminated.

  A series of processing in steps S700, S715, S720, S730, S735, S740, S745, S750, S755, and S760 corresponds to “Operation Example 1” described later. In other words, when it is determined in steps S700 and S715 that the output signal VS of the oxygen sensor is equal to or greater than the rich determination threshold at the start of learning after the elapse of a predetermined time, the target A / F correction value is set in steps S720, S730, and S735. The value is gradually decreased from a value corresponding to the output air-fuel ratio to a value corresponding to the theoretical air-fuel ratio.

Then, step S740, S745, in S750, gradually reduced the O2FF correction coefficient, in O2FF correction coefficient when the output signal of the oxygen sensor 28 is equal to or less than the threshold value O ₂ TH, O2FF correction coefficient to that point In step S755 and S760, the target A / F correction value is returned to a value corresponding to the output air-fuel ratio. Note that the above-described increase / decrease Δh1 of the variable AFH, decrease Δh2 of the variable O2FF, increase h3, h4, and the like can be set to appropriate values.

(Operation Example 1 to Operation Example 4)
Next, operation example 1 to operation example 4 will be described with reference to FIGS. 9 to 12. 9 to 12, the horizontal axis is set to time. 9 to 12, the “sensor voltage determination threshold” is set to refer to the output voltage VS of the oxygen sensor 28 to determine whether the engine is in a rich state or a lean state with respect to the theoretical air-fuel ratio. The set threshold value.

(Operation example 1)
FIG. 9 is a timing chart illustrating “Operation Example 1”. “Operation example 1” is an operation in the case where the air is thinned by traveling from a lowland to a highland. The initial value of the target A / F correction value is set to a value corresponding to the output air / fuel ratio. Next, the target A / F correction value is gradually decreased to the reference value. The reference value is a value at which the target A / F correction value corresponds to the theoretical air-fuel ratio. The target A / F correction value is gradually decreased from a value corresponding to the output air-fuel ratio to a value corresponding to the stoichiometric air-fuel ratio, and when the value becomes a value corresponding to the stoichiometric air-fuel ratio, the decrease is stopped.

  When the decrease of the target A / F correction value is stopped, it is confirmed that the output signal VS of the oxygen sensor 28 is in a rich state equal to or higher than the rich sensor voltage determination threshold, and the value of the O2FF correction coefficient is gradually decreased. The initial value of the O2FF correction coefficient is the value of the previous learning result. When VS is below the sensor voltage determination threshold value, that is, when it is in a lean state, the decrease in the value of the O2FF correction coefficient is stopped, and the value of the O2FF correction coefficient at this time is the value up to this point. Is updated and stored. Thus, learning of the O2FF correction coefficient is performed. In response to the update of the O2FF correction coefficient, the target A / F correction value is gradually returned to a value corresponding to the output air-fuel ratio.

As described above, the correction coefficient learning unit 140 calculates the target A / F correction value from the value corresponding to the output air-fuel ratio when the output signal VS of the oxygen sensor 28 is equal to or higher than the rich sensor voltage determination threshold at the start of learning. Decreasing function that gradually decreases to the value corresponding to the air-fuel ratio, and the O2FF correction coefficient is gradually decreased at the timing when the target A / F correction value reaches the value corresponding to the theoretical air-fuel ratio. In response to this update, the learning function that stops the decrease of the O2FF correction coefficient when the voltage judgment threshold value is reached, and updates and stores the O2FF correction coefficient up to that point with the O2FF correction coefficient at the time of the decrease stop. And a return function for returning the target A / F correction value to a value corresponding to the output theoretical ratio.

  According to the first operation example, the O2FF correction coefficient is decreased because it is initially in the rich state. However, when the output signal VS of the oxygen sensor 28 is equal to or lower than the sensor voltage determination threshold, it is determined that the lean state in which the air is lean is obtained. Then, the decrease of the O2FF correction coefficient is stopped. As a result, even if the vehicle travels from a lowland to a highland where the air is lean, the air / fuel ratio “A / F” is greater than or equal to the output air / fuel ratio “12.5” as shown in the expected transition result of the A / F value in the lower part of FIG. Can be maintained.

(Operation example 2)
FIG. 10 is a timing chart illustrating “Operation Example 2”. “Operation example 2” is an operation example when, for example, the air travels slightly from a highland to a lowland and the air becomes thin. The initial value of the target A / F correction value is set to a value corresponding to the output air / fuel ratio. Next, the target A / F correction value is gradually decreased to the reference value. Similar to the first operation example, the reference value is a value corresponding to the theoretical air-fuel ratio as the target A / F correction value. The target A / F correction value is gradually decreased from a value corresponding to the output air-fuel ratio to a value corresponding to the stoichiometric air-fuel ratio, and when the value becomes a value corresponding to the stoichiometric air-fuel ratio, the decrease is stopped. However, before being reduced to the reference value, the rich state is changed to the lean state.

  In this case, the increase in the target A / F correction value is stopped when the output signal VS of the oxygen sensor 28 becomes equal to or lower than the sensor voltage determination threshold, that is, when the lean state is reached, and the target A / F correction value The value of the O2FF correction coefficient is increased by the difference between the reference value and the value of the variable AFH at that time. The initial value of the O2FF correction coefficient before increasing the value of the O2FF correction coefficient is the value of the previous learning result. Then, the value up to this point is updated and stored with the value of the O2FF correction coefficient at this time. Thus, learning of the O2FF correction coefficient is performed.

Also, as shown in FIG. 10, the amount of increase of the O2FF correction coefficient from the previous learning value is a value corresponding to the difference between the reference value of the target A / F correction value and the target A / F correction value when the reduction process is stopped. It is. As a result, the fuel injection amount corresponding to the rich air can be earned by the O2FF correction coefficient, and the output air-fuel ratio can be maintained.

  As described above, in the process of decreasing the target A / F correction value, the correction coefficient learning unit 140 stops increasing the target A / F correction value and stops increasing the target A / F correction value when VS becomes equal to or lower than the sensor voltage determination threshold value. The O2FF correction coefficient increased by the difference between the reference value of the / F correction value and the value of the variable AFH at that time, the O2FF correction coefficient up to that point is updated, and the target A / F correction value is set to the output theoretical ratio. Has the function to return to

  According to the second operation example, even when the air travels slightly from the highland to the lowland and the air becomes dense, by increasing the O2FF correction coefficient, as shown in the lower part of FIG. The value of “F” can be maintained to be equal to or higher than the output air-fuel ratio “12.5”.

(Operation example 3)
FIG. 11 is a timing chart illustrating “Operation Example 3”. “Operation example 3” is an operation example when traveling from a highland to a lowland and air dilution is eliminated. In this case, since the air is dark from the beginning, the lean state is established from the beginning of learning. First, the initial value of the target A / F correction value is set to a value corresponding to the output air-fuel ratio. First, it is confirmed that the output signal VS of the oxygen sensor 28 is equal to or less than the lean sensor voltage determination threshold, and the target A / F correction value is gradually decreased to the reference value and the O2FF correction coefficient value is gradually increased. Let When the target A / F correction value reaches the reference value, the decrease is stopped. The initial value of the O2FF correction coefficient is the learning value up to the previous time.

  Then, when the VS is equal to or higher than the sensor voltage determination threshold value, that is, when the VS becomes rich, the increase of the O2FF correction coefficient is stopped, and the value of the O2FF correction coefficient up to this point is determined by the O2FF correction coefficient at that time. Update and store. Thus, learning of the O2FF correction coefficient is executed. Then, in response to the update of the O2FF correction coefficient, the target A / F correction value is gradually returned to a value corresponding to the output air-fuel ratio.

As described above, the correction coefficient learning unit 140 calculates the target A / F correction value from the value corresponding to the output air-fuel ratio when the output voltage VS of the oxygen sensor 28 is equal to or lower than the lean sensor voltage determination threshold at the start of learning. A control function that gradually increases the air-fuel ratio to a value corresponding to the air-fuel ratio and gradually decreases the O2FF correction coefficient, and stops increasing the O2FF correction coefficient when VS becomes equal to or greater than the sensor voltage determination threshold. A learning function for updating the O2FF correction coefficient up to that point with the correction coefficient and a return function for returning the target A / F correction value to a value corresponding to the theoretical air-fuel ratio in response to this update are provided.

  According to Operation Example 3, the O2FF correction coefficient is increased from the beginning even when the altitude changes from a high altitude where air is scarce to a low altitude, and the increase of the O2FF correction coefficient is stopped when shifting to the rich state. 11, the air-fuel ratio “A / F” can maintain the output air-fuel ratio “12.5”.

(Operation example 4)
FIG. 12 is a timing chart showing “Operation Example 4”. In “Operation Example 4”, the sensor output signal (VS) from the oxygen sensor 28 becomes equal to or lower than the sensor voltage determination threshold and becomes equal to or higher than the sensor voltage determination threshold within a predetermined time after the highland fuel correction execution condition is satisfied. Repeat that.

  As described above, the lean state and the rich state are repeated a predetermined number of times with respect to the stoichiometric air-fuel ratio within a predetermined time after the highland fuel correction execution condition is satisfied. In this case, the correction coefficient learning unit 150 increases the second correction coefficient (O2FF correction coefficient) by a predetermined amount all at once. Thus, the fuel injection amount can be increased at a stretch in an unstable air-fuel ratio state in the non-feedback region, and the air-fuel ratio during high altitude traveling can be stabilized. In addition, it is possible to cope with a case where learning is insufficient when establishment of the highland fuel correction execution condition becomes late during highland travel.

According to the embodiment described above, the determination unit 110 determines whether or not the current operation region is the feedback region with reference to the throttle opening, the engine speed, and the map 134. When the determination unit 110 determines that the current operating region is feedback, the feedback control unit 120 causes the air-fuel ratio to approach the target air-fuel ratio so that the actual air-fuel ratio according to the output signal VS of the oxygen sensor 28 is approached. Calculate the feedback correction coefficient “O2FB coefficient”.

On the other hand, when the determination unit 110 determines that the current operation region is the non-feedback region, the correction coefficient learning unit 140 learns the O2FF correction coefficient using the initial value of the target air-fuel ratio as the output air-fuel ratio. . Learning is executed by updating and storing the O2FF correction coefficient up to that point, and the initial value of the next O2FF coefficient is the previous learning result.

Then, the fuel injection control unit 150 obtains the fuel injection amount by multiplying the “O2FB coefficient” that is the air-fuel ratio feedback correction coefficient, the “O2FF coefficient” that is the second correction coefficient, and the “basic injection amount”. On the other hand, when the non-feedback region is determined, the fuel injection is performed by multiplying the “O2FB coefficient”, the “O2FF coefficient”, the “basic injection amount”, and the constant “1.168 (theoretical air fuel ratio / output air fuel ratio)”. The amount is obtained, and a fuel injection control signal corresponding to the obtained fuel injection amount is given to the injector 40.

  As described above, the “O2FF coefficient” which is the second correction coefficient reflecting the atmospheric pressure change is introduced, and the O2FF coefficient is learned while referring to the output signal of the oxygen sensor 28, so that fuel injection is performed even during high altitude traveling. The amount can be adjusted appropriately. As a result, engine stall can be prevented and the output air-fuel ratio can be maintained even when the air becomes lean. Further, since the target air-fuel ratio is gradually increased or decreased without increasing or decreasing all at once, drivability is not adversely affected.

(High altitude fuel correction implementation condition (learning start condition))
The learning described with reference to FIGS. 7 and 8 is started when the highland fuel correction execution condition is satisfied. The highland fuel correction execution conditions are as follows: (1) After the process determination has been completed by the CPU 200 based on the signal from the electromagnetic pickup 22, (2) No fuel cut, (3) Not in acceleration / deceleration mode (4) All conditions such as a predetermined time has passed since the last learning are satisfied. However, the highland fuel correction execution conditions are not limited to these.

As described above, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made. For example, the increase / decrease of the target A / F correction value may be linear instead of stepped, or may be interpolated with a polynomial. In addition to the two wheels, the control device 200 can be mounted on four wheels. In addition, the contents of the map 134 can be variously changed. Moreover, although the example which determines whether it is a rich state or a lean state using the rich determination threshold value and the lean determination threshold value in steps S700 and S715 has been described, it is not limited thereto. For example, a threshold value O ₂ TH may be used. In this case, when it is determined that VS is larger than the threshold value O ₂ TH, it is determined that it is in a rich state, and when it is determined that VS is smaller than the threshold value O ₂ TH, it is determined that it is in a lean state.

  As described above, the present invention can be applied to engine control of a two-wheeled vehicle, a four-wheeled vehicle, etc. that frequently travel on high ground.

1 Engine 2 Cylinder 3 Piston 22 Electromagnetic Pickup 26 Throttle Opening Sensor 28 Oxygen Sensor (O ₂ Sensor)
40 Injector 45 Spark Plug 100 Control Device 110 Determination Unit 120 Feedback Control Unit 130 Storage Unit 132 Program 134 Map 136 Nonvolatile Storage Area 140 Fuel Injection Control Unit 150 Correction Coefficient Learning Unit 160 Ignition Control Unit

Claims (8)

An engine control apparatus capable of calculating a feedback correction coefficient for asymptotically approaching a target air-fuel ratio from an actual air-fuel ratio measured by an oxygen sensor,
A correction coefficient learning unit that learns a second correction coefficient that is a correction coefficient for correcting the fuel injection amount together with the feedback correction coefficient when the current operation area is a non-feedback area other than the feedback area;
A fuel injection control unit that obtains a fuel injection amount based on the basic injection amount, the feedback correction coefficient, and the second correction coefficient and provides a corresponding fuel injection control signal to the fuel injection device;
The correction coefficient learning unit
The second correction coefficient is changed and controlled according to the output signal of the oxygen sensor at the start of learning, and the second correction coefficient at the time when the output signal crosses the threshold value corresponding to the theoretical air-fuel ratio, the previous correction coefficient An engine control device that updates and stores the second correction coefficient. The engine control device according to claim 1,
A determination unit for determining whether or not the current operation region is a feedback region;
An engine control device comprising: a feedback control unit that calculates the feedback correction coefficient when it is determined as the feedback region. The engine control device according to claim 1 or 2,
The fuel injection control unit
When the feedback region is determined, the fuel injection amount is obtained by multiplying the addition result of the feedback correction coefficient and the second correction coefficient by the basic injection amount,
When the non-feedback region is determined, the fuel injection amount is obtained by multiplying the addition result obtained by adding the feedback correction coefficient and the second correction coefficient by the basic injection amount and a preset constant. A characteristic engine control device. The engine control device according to any one of claims 1, 2, and 3,
The correction coefficient learning unit
When it is determined at the start of learning that the stoichiometric air-fuel ratio is rich based on the output signal of the oxygen sensor, a target A / F correction value that is a correction value corresponding to the target air-fuel ratio is output. A decreasing function for gradually decreasing from a value corresponding to the value to the theoretical air-fuel ratio,
When the target A / F correction value reaches a value corresponding to the theoretical air-fuel ratio, the second correction coefficient is gradually decreased, and when the output signal becomes equal to or less than the threshold, the second correction coefficient A learning function that stops the decrease of the second correction coefficient and updates and stores the second correction coefficient up to that time with the second correction coefficient at the time of the decrease stop;
An engine control device comprising: a return function for returning the target A / F correction value to a value corresponding to the output air-fuel ratio after storing the second correction coefficient. The engine control device according to claim 4,
The learning function is
In the process of decreasing the target A / F correction value by the decreasing function, when the output signal becomes equal to or less than the threshold value, the decreasing function is stopped and the target A / F correction value at the time of stopping the decreasing function is And increasing the second correction coefficient by an amount corresponding to the difference between the value and the value corresponding to the theoretical air-fuel ratio,
The engine control apparatus, wherein the second correction coefficient up to that point is updated and stored with the increased second correction coefficient. The engine control device according to any one of claims 1, 2, and 3,
The correction coefficient learning unit
When it is determined at the start of learning that the lean state is determined with respect to the theoretical air-fuel ratio based on the output signal of the oxygen sensor, a target A / F correction value that is a correction value corresponding to the target air-fuel ratio is output. A control function for gradually decreasing the value corresponding to the theoretical air-fuel ratio to a value corresponding to the stoichiometric air-fuel ratio and gradually increasing the second correction coefficient;
A learning function for updating and storing the second correction coefficient up to that time with the second correction coefficient when the output signal becomes equal to or greater than the threshold by the control function;
An engine control device comprising: a return function for returning the target A / F correction value to a value corresponding to the output air-fuel ratio. The engine control device according to any one of claims 1, 2, 3, 4 and 5,
The correction coefficient learning unit
A correction coefficient increasing function for increasing the second correction coefficient by a predetermined value when the output signal of the oxygen sensor crosses the threshold value a predetermined number of times within a predetermined time from the start of learning; A characteristic engine control device. A program for operating an engine control device capable of calculating a feedback correction coefficient for asymptotically approaching an actual air-fuel ratio measured by an oxygen sensor to a target air-fuel ratio,
A correction coefficient learning process for learning a second correction coefficient that is a correction coefficient for correcting the fuel injection amount together with the feedback correction coefficient when the current operation area is a non-feedback area other than the feedback area;
A fuel injection control process for determining a fuel injection amount based on the basic injection amount, the feedback correction coefficient, and the second correction coefficient and providing a corresponding fuel injection control signal to the fuel injection device. Program,
The correction coefficient learning process includes
The second correction coefficient is changed and controlled according to the output signal of the oxygen sensor at the start of learning, and the second correction coefficient at the time when the output signal crosses the threshold value corresponding to the theoretical air-fuel ratio, the previous correction coefficient An engine control program for updating and storing the second correction coefficient.

Images