JP4532306B2 - Air-fuel ratio control device for internal combustion engine for outboard motor - Google Patents

Description

  The present invention relates to an air-fuel ratio control apparatus for an outboard motor internal combustion engine.

_2. Description of the Related Art Conventionally, a technique is known in which an air-fuel ratio of an internal combustion engine is feedback controlled using an O ₂ sensor arranged in an exhaust system. In this type of technology, since the O ₂ sensor utilizes the property that the characteristic changes in the vicinity of the stoichiometric air-fuel ratio, feedback control cannot be performed when the target air-fuel ratio is other than the stoichiometric air-fuel ratio. . Therefore, the learning correction coefficient is calculated based on the feedback correction coefficient used in the feedback control, and when the target air-fuel ratio is other than the theoretical air-fuel ratio, the basic fuel injection amount is corrected using this learning correction coefficient, The air-fuel ratio is controlled to an air-fuel ratio other than the stoichiometric air-fuel ratio (open loop control) (see, for example, Patent Document 1). A technique in which the air-fuel ratio is controlled using a LAF sensor that generates a linear output with a wide air-fuel ratio instead of the O ₂ sensor is also widely known.
JP-A-57-105530

When the LAF sensor is used, the correction coefficient can be calculated even when the target air-fuel ratio is other than the stoichiometric air-fuel ratio, so that the air-fuel ratio can be controlled with higher accuracy than using the O ₂ sensor. On the other hand, the LAF sensor is more expensive than the O ₂ sensor and has a drawback of increasing the cost.

Therefore, the object of the present invention is to solve the above-described problems and to control the air-fuel ratio to an air-fuel ratio other than the stoichiometric air-fuel ratio with high accuracy while using an O ₂ sensor whose output characteristics change near the stoichiometric air-fuel ratio. An object is to provide an air-fuel ratio control device for an outboard motor internal combustion engine.

In order to solve the above object, according to claim 1, in the air-fuel ratio control apparatus for an outboard motor internal combustion engine that controls the air-fuel ratio of the internal combustion engine mounted on the outboard motor, at least the engine speed and An operating state detecting means for detecting an operating state of the internal combustion engine including an engine load; an O ₂ sensor which is disposed in an exhaust system of the internal combustion engine and generates an output whose characteristics change in the vicinity of a theoretical air-fuel ratio; The first fuel injection amount determined based on the operating state is corrected with a feedback correction coefficient determined based on the output of the O ₂ sensor, thereby controlling the air-fuel ratio of the internal combustion engine to the stoichiometric air-fuel ratio. And a learning correction unit for correcting the basic fuel injection amount in each of the plurality of storage areas, the control means, and a plurality of storage areas divided according to the engine speed and the engine load value. A learning correction coefficient storing means for storing said feedback learning correction coefficient calculating means for calculating the learning correction coefficient based on the correction coefficient, the internal combustion engine is set according the engine load on the engine rotational speed is constant Learning correction coefficient updating means for updating the calculated learning correction coefficient by overwriting the stored learning correction coefficient when in a predetermined load range indicating that the engine is in operation; the engine speed and the engine load And a second control means for controlling the air / fuel ratio to an air / fuel ratio different from the stoichiometric air / fuel ratio by retrieving the learning correction coefficient from the engine and correcting the basic fuel injection amount with at least the retrieved learning correction coefficient. It comprised so that it might be equipped with.

  According to a second aspect of the present invention, the second control means is configured to execute the control only when the learning correction coefficient is an updated value.

  According to a third aspect of the present invention, the second control means is configured to execute the control when a difference between the feedback correction coefficient and the updated learning correction coefficient is a predetermined value or less.

In the air-fuel ratio control apparatus for an outboard motor internal combustion engine according to claim 1, the basic fuel injection amount is corrected by a feedback correction coefficient determined on the basis of the output of the O ₂ sensor. A first control means for controlling the fuel ratio to the stoichiometric air-fuel ratio and a learning correction coefficient for correcting the basic fuel injection amount are stored in each of a plurality of storage areas divided according to the engine speed and the engine load value. A learning correction coefficient storage means, a learning correction coefficient calculation means for calculating a learning correction coefficient based on the feedback correction coefficient, and a predetermined value indicating that the engine load is set according to the engine speed and the internal combustion engine is in steady operation When the load is within the load range, the learning correction coefficient update means for updating the calculated learning correction coefficient by overwriting the stored learning correction coefficient, and the learning correction coefficient is searched from the engine speed and the engine load. Since it is configured to include a second control means for controlling the different air-fuel ratio from the stoichiometric air-fuel ratio by correcting the basic fuel injection quantity by the learning correction coefficient obtained I, using the O ₂ sensor However, the air-fuel ratio can be accurately controlled to an air-fuel ratio other than the stoichiometric air-fuel ratio.

More specifically, in an internal combustion engine mounted on an outboard motor, unlike an internal combustion engine mounted on a four-wheeled vehicle or the like, the engine load during steady operation is limited to a certain range. Therefore, the learning correction coefficient is updated only when the engine load is within a predetermined load range set in accordance with the engine speed (that is, during steady operation), so that learning correction such as transient operation is performed. Factors that disturb the value of the coefficient can be eliminated, and the learning correction coefficient can be set to a more appropriate value. Therefore, the air-fuel ratio can be accurately controlled to an air-fuel ratio other than the stoichiometric air-fuel ratio while using an O ₂ sensor that is less expensive than the LAF sensor.

  In the air-fuel ratio control apparatus for an outboard motor internal combustion engine according to claim 2, the air-fuel ratio is calculated only when the learning correction coefficient retrieved from the engine speed and the engine load has been updated. Since the control is executed to the air-fuel ratio other than the fuel ratio, in addition to the above-described effect, the optimal learning correction coefficient can always be used for the air-fuel ratio control, so that the air-fuel ratio can be controlled more accurately. it can.

In the air-fuel ratio control apparatus for an outboard motor internal combustion engine according to claim 3, when the difference between the feedback correction coefficient and the updated learning correction coefficient is equal to or smaller than a predetermined value, the air-fuel ratio is set to a value other than the stoichiometric air-fuel ratio. Since the control is executed to the air-fuel ratio, in addition to the above-described effect, the air-fuel ratio control is performed using a learning correction coefficient that is not accurate and is calculated immediately after the start when the output of the O ₂ sensor is unstable. Can be prevented, and the air-fuel ratio can be controlled more accurately.

  The best mode for carrying out an air-fuel ratio control apparatus for an outboard motor internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing an outboard motor including a hull mounted with an air-fuel ratio control apparatus for an internal combustion engine for an outboard motor according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes an outboard motor. The outboard motor 10 is attached to the rear of the hull (hull) 12 as shown in the figure.

  An internal combustion engine (hereinafter referred to as “engine”) 14 is mounted on the outboard motor 10. The engine 14 is a multi-cylinder spark ignition gasoline engine. On the other hand, a propeller 16 is provided below the outboard motor 10. The propeller 16 rotates when the output of the engine 14 is transmitted via a shift mechanism (described later) or the like, and generates a thrust force that moves the hull 12 forward or backward.

  An electronic control unit (hereinafter referred to as “ECU”) 20 is disposed in the vicinity of the engine 14. The ECU 20 is composed of a microcomputer, and controls the air-fuel ratio of the engine 14 based on the output of each sensor described later.

  In the vicinity of the cockpit of the hull 12, a throttle lever 22 that can be swung by the operator is disposed. The throttle lever 22 is connected to a throttle valve (not shown in FIG. 1) of the engine 14 via a push-pull cable 24. The hull 12 is also provided with a shift lever for operating the shift mechanism of the outboard motor 10, a switch for inputting an instruction for adjusting the tilt / trim angle of the outboard motor 10, and the like. Since there is no direct relationship, the illustration is omitted.

  FIG. 2 is a schematic diagram showing the engine 14 and the ECU 20 shown in FIG.

As shown in FIG. 2, a throttle valve 28 is disposed on the upstream side of the intake pipe 26 of the engine 14. As described above, the throttle valve 28 is connected to the throttle lever 22 provided in the hull (not shown in FIG. 2 ) via the push-pull cable 24, and is opened and closed according to the operation amount of the throttle lever 22 to be engine. 14 intakes are metered. A throttle opening sensor 30 is provided in the vicinity of the throttle valve 28 and outputs a signal corresponding to the throttle opening θTH.

  An injector 32 is provided for each cylinder (not shown) in the vicinity of the intake port immediately after the intake manifold (not shown) downstream of the throttle valve 28. The injector 32 pumps gasoline fuel from a fuel tank (not shown) via a fuel pump and a fuel pipe, and the valve opening time is controlled by a control signal from the ECU 20.

  An intake pipe pressure sensor 34 and an intake air temperature sensor 36 are disposed downstream of the throttle valve 28 in the intake pipe 26, and output signals indicating the intake pipe internal pressure (load) PBA and the intake air temperature TA, respectively. Further, a water temperature sensor 38 is disposed on a cylinder peripheral wall (not shown) filled with cooling water in the cylinder block of ethidine 14 and outputs a signal corresponding to the engine cooling water temperature TW.

  A cylinder discrimination sensor 40 is disposed in the vicinity of the crankshaft (not shown) of the engine 14 and outputs a cylinder discrimination signal CYL when a specific cylinder reaches a predetermined classic angle position. Further, a TDC sensor 42 and a crank angle sensor 44 are disposed in the vicinity of the crankshaft of the engine 14. The TDC sensor 42 outputs a TDC signal at a predetermined crank angle position related to the TDC position of the piston of each cylinder, and the crank angle sensor 44 outputs a CRK signal at a crank angle having a shorter cycle than the TDC signal (for example, 30 degrees). To do.

An O ₂ sensor 50 is disposed on the exhaust system of the engine 14, specifically on the upstream side of the three-way catalyst 48 provided in the exhaust pipe 46. The O ₂ sensor 50 generates an output whose characteristics change in the vicinity of the theoretical air-fuel ratio. Specifically, the output voltage of the O ₂ sensor 50 changes suddenly near the theoretical air-fuel ratio. Therefore, it is possible to determine whether the air-fuel ratio is lean or rich with respect to the stoichiometric air-fuel ratio by comparing the output voltage of the O ₂ sensor 50 with a reference voltage representing the stoichiometric air-fuel ratio. An atmospheric pressure sensor 52 is disposed at an appropriate position near the engine 14. The atmospheric pressure sensor 52 outputs a signal corresponding to the atmospheric pressure PA.

The output of each sensor described above is input to the ECU 20. ECU20 includes a CPU20a performing an operation for executing a control of each part of the engine 14, and ROM20b for storing various programs and data for executing the control of each part of the engine 1 4, calculated in the sensor output and CPU20a A RAM 20c (learning correction coefficient storage means) for storing a learning correction coefficient (described later), an EEPROM 20d (Electrically Erasable Programmable Read Only Memory) that is a non-volatile memory for storing the learning correction coefficient, and the like. An input circuit 20e for inputting the incoming signal and an output circuit 20f for sending a control signal to each part of the engine 14 are provided.

  The input circuit 20e shapes the input signal waveform, corrects the voltage level to a predetermined level, and converts the analog signal value to a digital signal value. The CPU 20a processes the converted digital signal, executes an operation according to a program stored in the ROM 20b, and sends a control signal to the injector 32 and other actuators (not shown) via the output circuit 20f. The CRK signal input to the ECU 20 is counted by a counter (not shown), and the engine speed NE is detected.

  In addition, an ignition switch 54 is provided at an appropriate position of the outboard motor 10 or the hull 12. The ignition switch 54 has an OFF position, an ON position, and a start position in order, and supplies and shuts off electric power to each portion according to the position selected by the ship operator. Specifically, when the off position is selected, all power supply to the ECU 20, the injector 32, each sensor, and the like is cut off. On the other hand, when the on position is selected, power supply to the ECU 20, the injector 32, each sensor, and the like excluding the cell motor (not shown) is started. When the start position is selected after passing through the on position, the cell motor operates to start cranking, and the engine 14 is started.

  Next, with reference to FIG. 3 and subsequent figures, the control of the engine 14 executed by the ECU 20, specifically, the air-fuel ratio control will be described.

  FIG. 3 is an explanatory diagram showing an outline of air-fuel ratio control executed by the ECU 20.

  As shown in FIG. 3, when the engine speed NE is in the low / medium speed range and the intake pipe pressure PBA (engine load) is in the low / medium load range, lean burn control (open loop control) is executed. Is done.

  Also, the air-fuel ratio is feedback-controlled to the stoichiometric air-fuel ratio in an extremely low load such as idling, an extremely low rotation range, and a higher load and a higher rotation range than the lean burn range (shown as a stoichiometric range in the figure). On the other hand, the air-fuel ratio is open-loop controlled in a higher load range than the stoichiometric range.

The air-fuel ratio is controlled by adjusting the fuel injection amount Tout (more specifically, the valve opening time of the injector 32). The fuel injection amount Tout is calculated according to the following equation.
Fuel injection amount Tout = basic fuel injection amount Ti × feedback correction coefficient KO ₂
× Learning correction coefficient KTIM × Environment correction term × Target equivalent ratio KCMD

In the above equation, the basic fuel injection amount Ti is obtained by searching a preset map with the engine speed NE and the intake pipe pressure PBA. Further, the feedback correction coefficient KO ₂ is calculated based on the output of the O ₂ sensor 50. Specifically, the output voltage of the O ₂ sensor 50 is compared with a reference voltage representing the theoretical air-fuel ratio to determine whether the current air-fuel ratio is lean or rich. If the air-fuel ratio is rich, the feedback correction coefficient KO ₂ is set. Decrease in steps, while in the case of lean increase in steps.

The learning correction coefficient KTIM is as will be described in detail later, is calculated based on the running of the feedback control to the output of the feedback correction coefficient KO _2. The environmental correction term is calculated based on the intake air temperature TA, the engine coolant temperature TW, the atmospheric pressure PA, and the like. The target equivalent ratio KCMD is a value corresponding to the target air-fuel ratio, and is obtained based on the engine speed NE and the intake pipe pressure PBA.

During the feedback control, the learning correction coefficient KTIM is fixed at 1.0, and the target equivalent ratio KCMD is fixed at a value representing the stoichiometric air-fuel ratio. On the other hand, the feedback correction coefficient KO ₂ is fixed at 1.0 during the lean burn control. Further, the open-loop control at the time of high load, the feedback correction coefficient KO ₂ and the learning correction coefficient KTIM is set to 1.0 both separately acceleration increase correction to the above is performed.

  The air-fuel ratio control apparatus for an outboard motor internal combustion engine according to the present invention is characterized by the above-described lean burn control, and will be described in detail below.

  FIG. 4 is a main routine flowchart showing a lean burn control process executed by the ECU 20. The illustrated program is executed in the ECU 20 at a predetermined cycle (for example, at an interval of 10 msec).

  In the following, first, in S10, the target equivalent ratio KCMD is calculated.

  FIG. 5 is a sub-routine flowchart showing the calculation process of the target equivalent ratio KCMD.

  Referring to the flowchart of FIG. 5, first, at S100, the lean burn control transition permission flag F.R. It is determined whether the SLBREFOK bit is set to 1. Lean burn control transition permission flag When the SLBREFOK bit (initial value 0) is set to 1, this indicates that the transition to lean burn control, that is, execution of lean burn control is permitted.

  When the result in S100 is negative, the program proceeds to S102, where the target equivalent ratio KCMD is set to a value representing the theoretical air-fuel ratio (14.7). Then, the process proceeds to S104 and the lean burn execution flag F.S. Reset the SLB bit to zero. Lean burn in progress flag SLB indicates that lean burn control is being executed when the bit (initial value 0) is set to 1. The target equivalence ratio KCMD set in S102 is used to calculate the fuel injection amount Tout by feedback control or open loop control at high load.

  On the other hand, when the result in S100 is affirmative, the routine proceeds to S106, where it is determined whether or not the current routine is the first routine after allowing the shift to lean burn control. When the result in S106 is affirmative, the program proceeds to S108, in which the learning correction coefficient KTIM stored in the EEPROM 20d is overwritten on the learning correction coefficient map stored in the RAM 20c and updated. The learning correction coefficient KTIM stored in the RAM 20c and the EEPROM 20d will be described in detail later. If the determination at S106 is No, the process at S108 is skipped.

  In S110, a learning correction coefficient map is searched from the operating state of the engine 14 to obtain a learning correction coefficient KTIM (this process will be described in detail later). Next, in S112, the target equivalent ratio KCMD is calculated. Specifically, a target prepared value KBS is obtained by searching a map prepared in advance from the engine speed NE and the intake pipe pressure PBA, and the value of the target equivalent ratio KCMD so as to converge to the obtained target converged value KBS. Is gradually changed. The learning correction coefficient KTIM obtained in S110 and the target equivalent ratio KCMD calculated in S112 are used to calculate the fuel injection amount Tout by lean burn control. Therefore, the target equivalent ratio KCMD calculated in S112 is set to a value representing the air-fuel ratio leaner than the theoretical air-fuel ratio. Thereafter, the process proceeds to S114, where the lean burn execution flag F.I. Set the SLB bit to 1.

  Returning to the description of FIG. It is determined whether the SLB bit is set to 1, that is, whether lean burn control is being executed. When the result in S12 is negative, the program proceeds to S14 to correct the learning correction coefficient map.

  FIG. 6 is a sub-routine flowchart showing the correction process of the learning correction coefficient map.

Referring to the flowchart of FIG. 6, first, the output voltage of the O ₂ sensor 50 is read in S200. Next, in S202, the output voltage of the O ₂ sensor 50 read in S200 is compared with a reference voltage representing the stoichiometric air-fuel ratio, and it is determined whether the current air-fuel ratio is lean or rich with respect to the stoichiometric air-fuel ratio. When the lean determination is made at S202, the enrichment coefficient is calculated at S204, while when the rich determination is made at S202, the leaning coefficient is calculated at S206. The enrichment coefficient and the leaning coefficient are an addition term and a subtraction term that are obtained according to the degree of lean and rich, respectively.

Next, in S208, a learning correction coefficient KTIM is calculated. The learning correction coefficient KTIM is closer to the feedback correction coefficient KO ₂ used in the feedback control, is stepwise increased or decreased by using the enrichment factor and the lean coefficient. The learning correction coefficient KTIM calculated in S208 is specifically the average value of KTIM calculated within a predetermined period.

  Next, in S210, the storage area of the learning correction coefficient map corresponding to the current operating state is searched.

  FIG. 7 is an explanatory diagram showing a learning correction coefficient map stored in the RAM 20c.

  As shown in FIG. 7, the learning correction coefficient map includes a plurality of storage areas divided according to the values of the engine speed NE and the intake pipe pressure PBA (engine load). Specifically, it consists of a total of 64 storage areas divided into 8 rows according to the value of the engine speed NE and 8 rows according to the value of the intake pipe pressure PBA, and each memory area has a learning correction. The coefficient KTIM is stored. Hereinafter, the learning correction coefficient KTIM is expressed as “KTIMn” (n: an integer from 0 to 63) as necessary.

  In addition, eight columns divided according to the magnitude of the engine speed NE are represented by “NKTIMm” (m: an integer from 1 to 8), and eight rows divided according to the magnitude of the intake pipe pressure PBA are represented by “ “PBKTIMm” (m: integer from 1 to 8). The column NKTIMm indicates that the higher the value of m is, the higher the rotation region is, and the row PBKTIMm indicates that the higher the value of m, the higher the load region.

  In FIG. 7, KTIMn stored in the storage area surrounded by a thick line is an updatable value (initial value 1.0). On the other hand, all KTIMn stored in other storage areas are fixed values (1.0). Hereinafter, the storage area in which the updateable learning correction coefficient KTIM is stored is referred to as “updatable area”. As shown in the figure, if the intake pipe pressure PBA is within a predetermined range for a certain engine speed NE, the learning correction coefficient KTIM can be updated. In other words, the update of the learning correction coefficient KTIM is limited only when the intake pipe pressure PBA is within a predetermined range with respect to the engine speed NE.

  Note that the range (row PBKTIMm) of the intake pipe pressure PBA in which the learning correction coefficient KTIM can be updated changes according to the value of the engine speed NE. Specifically, as the engine speed NE increases (the value of m in the column NKTIMm increases), the load range becomes wider (the number of row PBKTIMm increases) and moves to the higher load side (in the row PBKTIMm). m increases).

  Returning to the description of the flowchart in FIG. 6, the process then proceeds to S212, in which it is determined whether the storage area searched in S210 is an updatable area. When the result is affirmative in S212, the process proceeds to S214, and the learning correction coefficient KTIMn stored in the searched updatable area is overwritten with the learning correction coefficient KTIM calculated in S208 and updated. On the other hand, when the result in S212 is negative, the process of S214 is skipped.

  Returning to the description of the flowchart of FIG. 4, the process then proceeds to S16, in which it is determined whether or not the transition to lean burn control is permitted. When the determination at S12 is affirmative (that is, when lean burn control is being executed), the process at S14 is skipped.

  FIG. 8 is a sub-routine flowchart showing a process related to determination of permission to shift to lean burn control.

  Referring to the flowchart of FIG. It is determined whether or not the bit (initial value 0) of NKTIMm (m: integer from 1 to 8) is set to 1. Store completion flag F. The meaning of NKTIMm will be described later.

  When the result in S300 is affirmative, the program proceeds to S302, where the lean burn execution flag F.S. It is determined whether or not the SLB bit is set to 1. When the result in S302 is affirmative, the subsequent processing is skipped, while when the result in S302 is negative, the process proceeds to S304.

  In S304, a learning correction coefficient KTIMn (specifically, a value stored in a storage area searched from the current engine speed NE and the intake pipe pressure PBA. Hereinafter, the same applies to the description of the flowchart of FIG. 8). Then, it is determined whether or not it has been updated in the process of S14 described above. When the result in S304 is negative, the program proceeds to S306, in which the lean burn control transition permission flag F.S. Reset the SLBREFOK bit to zero. That is, the shift to lean burn control is prohibited.

On the other hand, when the result is affirmative in S30 4 proceeds to S308, it is determined whether or not the cruise. The determination in S308 is made by determining whether or not the engine speed NE has been maintained for a predetermined time within the range of the same column NKTIMm. That is, “cruising” means that the vehicle is in steady operation. The predetermined time is counted by a timer tmKTAREA (down counter). Further, the value (that is, the predetermined time) set in the timer tmKTAREA is made different for each column NKTIMm.

When the result in S308 is negative, the program proceeds to S306 and the shift to lean burn control is prohibited. On the other hand, when the result in S308 is affirmative, the program proceeds to S310, where the learning correction coefficient KTIMn is compared with the feedback correction coefficient integrated average value KO ₂ MEN, and the program proceeds to S312, where the difference between KTIMn and KO ₂ MEN is equal to or less than a predetermined value. Judge whether or not. Here, KO ₂ MEN specifically means that the feedback correction coefficient KO ₂ is integrated at a predetermined interval (for example, every 10 msec) until the output of the O ₂ sensor 50 changes from lean to rich, and the integrated value is It is a value averaged by dividing by the number of integration. In S312, a difference between the environment when KTIMn is calculated (learned) and the current environment (more specifically, when lean burn control is executed) is prevented. In other words, KTIMn is not set. In order to prevent an accurate value, whether the difference between KTIMn and KO ₂ MEN is equal to or smaller than a predetermined value is confirmed.

  When the result in S312 is negative, the program proceeds to S306. When the result in S312 is positive, the program proceeds to S314, in which the lean burn execution flag F. Set the SLB bit to 1. Next, the process proceeds to S316, and the learning correction coefficient KTIMn is stored (stored) in the store value map stored in the EEPROM 20d.

  FIG. 9 is an explanatory diagram showing a store value map stored in the EEPROM 20d.

  As shown in FIG. 9, the store value map includes a plurality of storage areas divided according to the value of the engine speed NE. More specifically, eight storage areas divided in correspondence with the column NKTIMm of the learning correction coefficient map are provided, and the learning correction coefficient KTIMn is stored (stored) in each of the storage areas. Hereinafter, the learning correction coefficient KTIMn stored in the EEPROM 20d is referred to as a store value KTMRSTRm (m: an integer from 1 to 8).

  In S316, the learning correction coefficient KTIMn is stored in the storage area of the EEPROM 20d (KTMRSTRm is updated) as KTMRSTRm having the same value of m as the column NKTIMm to which the updatable area in which the value is stored belongs.

  Next, in S318, the store completion flag F.S. The bit of NKTIMm (specifically, F. NKTIMm having the same value of m as the column NKTIMm to which the stored learning correction coefficient KTIMn belongs) is set to 1. That is, the store completion flag F.I. NKTIMm means that when the bit is set to 1, a store value KTMSTRm having the same value of m is stored (updated) in the EEPROM 20d.

  In S300 described above, the store completion flag F.I. When the bit of NKTIMm is set to 1, that is, when the learning correction coefficient KTIMn is stored in the EEPROM 20d, the determination is affirmative and the process proceeds to S302. On the other hand, the store completion flag F.I. When the bit of NKTIMm is 0, the result in S300 is negative and the program proceeds to S320. After resetting the SLBREFOK bit to 0 (prohibition of transition to lean burn control), the process proceeds to S304 and thereafter.

  Here, the flowchart in FIG. 5 will be described again.

  In the flowchart of FIG. 5, first, at S100, the lean burn control transition permission flag F.R. It is determined whether or not the SLBREFOK bit is set to 1, that is, whether or not the shift to lean burn control is permitted. Flag F. As described above, the SLBREFOK bit is set to 1 at the same time as the learning correction coefficient KTIMn is stored in the EEPROM 20d (S314 and S316 in the flowchart of FIG. 8). The stored learning correction coefficient KTIMn is an updated value calculated and stored in the RAM 20c during the execution of feedback control. That is, the determination here corresponds to determining whether or not the learning correction coefficient KTIMn updated on the RAM 20c is stored in the EEPROM 20d.

  If the current routine is the first routine after permission to shift to lean burn control, the determination is affirmative in S100 and S106, and the process proceeds to S108. In S108, the learning correction coefficient KTIMn stored in the EEPROM 20d, that is, the store value KTMRSTRm is overwritten and updated on the learning correction coefficient map stored in the RAM 20c. Specifically, the store value KTMRSTm is overwritten on all the updatable areas (that is, a plurality of storage areas that can be searched from the same engine speed) belonging to the column NKTIMm having the same value of m. Thus, in the updatable areas belonging to the same column NKTIMm, the value of KTIMn is shared.

  When the engine 14 is restarted, the stored value KTMRSTRm is overwritten on the learning correction coefficient map as the initial value of the learning correction coefficient KTIMn regardless of the conditions of S100 and S106.

  Thereafter, the learning correction coefficient KTIM is searched from the detected values of the engine speed NE and the intake pipe pressure PBA, and the fuel injection amount Tout is calculated using KTIM obtained by the search, and the air-fuel ratio of the engine 14 is calculated theoretically. Open-loop control is performed to a target air-fuel ratio that is leaner than the air-fuel ratio.

  The above-described lean burn control process will be described again with reference to FIG.

  FIG. 10 is a time chart showing the lean burn control process executed based on the flowchart of FIG. FIGS. 11 to 16 are explanatory diagrams showing a learning correction coefficient map, a store value map, and the like.

When the intake pipe pressure PBA shows a value within a predetermined range with respect to the engine speed NE, as shown in FIG. 10, the learning correction coefficient KTIMn is updated stepwise so as to approach KO ₂ MEN. The processing at this time is shown in the flowchart of FIG. FIG. 11 shows an example of the learning correction coefficient map being updated. Note that the operation region in which lean burn control is executed is included in the operation region in which feedback control is executed, as shown in FIG. Therefore, when the intake pipe pressure PBA shows a value within a predetermined range with respect to the engine speed NE and the lean burn control is not executed, the feedback control is executed and KO ₂ and KO ₂ MEN are continuously updated. Therefore, the learning correction coefficient KTIMn can be updated.

When the countdown of the timer tmKTAREA ends and it is determined that the vehicle is cruising, a comparison between the updated learning correction coefficient KTIMn and KO ₂ MEN is started. When the difference between them becomes equal to or smaller than the predetermined value, the value of the learning correction coefficient KTIMn being updated is stored in the EEPROM 20d as the store value KTMRSTRm. At the same time, the flag F. SLBREFOK and flag F.F. The bit of NKT I Mm is set to 1. The process at this time is the flowchart of FIG. An example of the learning correction coefficient map and the store value map at this time is shown in FIG. FIG. 12 shows that the value of the learning correction coefficient KTIM27 belonging to the column NKTIM4 is stored in the EEPROM 20d as the store value KTMRSTR4. In the columns NKTIM1 and NKTIM2, the learning correction coefficient KTIMn is updated on the RAM 20c, but the stored value KTMRSTR1 or KTMRST R2 is not stored in the EEPROM 20d (the conditions of S308 and S312 were not satisfied). It is shown that.

  The store value KTMSTRm stored in the EEPROM 20d is overwritten on all updatable areas belonging to the column NKTIMm having the same value of m, so that all of the plurality of learning correction coefficients KTIMn stored in that area have the same value. Updated. That is, all updatable areas searched from a certain engine speed are overwritten with one value (KTMRSTRm). An example of the learning correction coefficient map and the store value map at this time is shown in FIG. As shown in FIG. 13, the value of the store value KTMRSTR4 is reflected in all of the KTIM19, KTIM27, and KTIM35, which are updateable areas belonging to the column NKTIM4.

  Then, the learning correction coefficient KTIM corresponding to NE and PBA is searched from the learning correction coefficient map updated as described above.

  FIG. 14 is an explanatory diagram showing a part of the learning correction coefficient map.

  The search for the learning correction coefficient KTIM will be described with reference to FIG. As described above, the learning correction coefficient map is divided into eight columns NKTIMm according to the engine speed NE, and into eight rows PBKTIMm according to the intake pipe pressure PBA. Specifically, the column NKTIMm has a certain width, for example, NKTIM3 is 1500 to 2000, and NKTIM4 is 2000 to 2500. The same applies to the row PBKTIMm.

  Therefore, the learning correction coefficient KTIM is obtained by linear interpolation, specifically, 4-point interpolation. For example, if the search point obtained from the engine speed NE and the intake pipe pressure PBA is point a in FIG. 14, KTIM 26, stored in four storage areas close to (or including point a), point a. Four-point interpolation is performed using KTIM27, KTIM34, and KTIM35, and the obtained value is used as a search value for the learning correction coefficient KTIM. However, when an unupdated value is included in the four KTIMn to be used for the four-point interpolation as in the case where the search point is the point b (in the example of FIG. 14, the bit of the flag F.NKTIM5 is 0) (Therefore, KTIM 28, KTIM 36, and KTIM 44 belonging to column NKTIM 5 have not been updated yet.) The four-point interpolation is stopped, and the value of the storage area including b point, that is, the value of KTIM 43 is set as the search value.

  The retrieved learning correction coefficient KTIM is used for correcting the basic fuel injection amount Ti together with other correction terms and the target equivalence ratio KCMD, and the fuel injection amount Tout during lean burn control is calculated. As shown in FIG. 10, the target equivalent ratio KCMD is changed stepwise toward the target convergence value KBS (lean side value). The process at this time is the flowchart of FIG.

In addition, as shown in FIG. When a transition is made to a column in which the bit of NKT I Mm is not set to 1 (FIG. 15 shows an example of transition from column NKTIM4 to column NKTIM5), flags F. The SLBREFOK bit is reset to zero. As a result, feedback control is executed instead of lean burn control, and the learning correction coefficient KTIMn belonging to the column NKTIM5 is updated.

  After that, when the learning correction coefficient KTIMn is stored in the EEPROM 20d as the store value KTMRSTR5 through the same processing as described above, the flag F. SLBREFOK and flag F.F. The bit of NKTMm is set to 1 (see FIG. 16). Then, after the value of KTMRSTR5 is overwritten on all of KTIM20, KTIM28, KTIM36, and KTIM44 belonging to the column NKTIM5, lean burn control is executed. Thus, the lean burn control is executed only when the learning correction coefficient KTIMn to be used is an updated value.

Thus, in the air-fuel ratio control apparatus for an outboard motor internal combustion engine according to the first embodiment of the present invention, the learning correction coefficient KTIMn used for open loop control (specifically, lean burn control) Since the intake pipe pressure PBA (engine load) is updated only when it is within a predetermined range with respect to the engine speed NE, the air-fuel ratio is changed to an air-fuel ratio other than the stoichiometric air-fuel ratio while using the O ₂ sensor. It can be controlled with high accuracy.

More specifically, in an engine mounted on an outboard motor, unlike an engine mounted on a four-wheeled vehicle or the like, the engine load during steady operation is limited to a certain range. Therefore, by updating the learning correction coefficient KTIMn only when the intake pipe pressure PBA is within a predetermined range with respect to the engine speed NE (that is, during steady operation, in other words, during cruise), Factors that disturb the value of the learning correction coefficient such as transient operation can be eliminated, and the learning correction coefficient can be set to a more appropriate value. Therefore, the air-fuel ratio can be accurately controlled to an air-fuel ratio other than the stoichiometric air-fuel ratio while using an O ₂ sensor that is less expensive than the LAF sensor.

  Further, among the plurality (64) of storage areas provided in the RAM 20c, a plurality of learning correction coefficients KTIMn stored in the updatable areas having the same column NKTIMm (that is, a plurality of search from the same engine speed). (KTIMn) is overwritten with one value (stored value KTMRSTRm) stored in the EEPROM 20d. In other words, in the storage area searched from the same engine speed, the value of the learning correction coefficient KTIMn is made common. As a result, the number of learning correction coefficients to be stored in the EEPROM 20d can be reduced, and thus the capacity of the EEPROM 20d can be reduced. The basic fuel injection amount Ti increases and decreases linearly with changes in the engine load (intake pipe pressure PBA). Therefore, if the engine speed is constant, the learning correction coefficient changes almost even if the engine load changes. do not do. Therefore, if the columns NKTIMm are the same, there is no practical problem even if the learning correction coefficient is shared.

  In addition, since the open loop control is executed only when the learning correction coefficient KTIMn used for correcting the basic fuel injection amount Ti has been updated, the optimal learning correction coefficient is always used for the air-fuel ratio control. It is possible to control the air-fuel ratio more accurately.

Further, since the open loop control is executed only when the difference between the feedback correction coefficient (specifically, KO ₂ MEN) and the updated learning correction coefficient KTIMn is equal to or less than a predetermined value, the output of the O ₂ sensor 50 This makes it possible to prevent the air-fuel ratio control from being performed by using a learning correction coefficient that is calculated with a low degree of accuracy, such as immediately after start-up, and to control the air-fuel ratio more accurately. .

  Further, when the engine 14 is restarted, the learning correction coefficient KTIMn (stored value KTMSTRm) stored in the EEPROM 20d is overwritten on the learning correction coefficient map of the RAM 20c as the initial value of the learning correction coefficient KTIMn. When the engine 14 is restarted, the learning correction coefficient calculated at the previous start can be used, and the air-fuel ratio can be quickly and accurately controlled to an air-fuel ratio other than the stoichiometric air-fuel ratio.

As described above, in the first embodiment of the present invention, in the air-fuel ratio control apparatus for an outboard motor internal combustion engine that controls the air-fuel ratio of the internal combustion engine (engine 14) mounted on the outboard motor (10). Operating state detecting means (crank angle sensor 44, intake pipe pressure sensor 34, etc.) for detecting the operating state of the internal combustion engine including at least the engine speed (engine speed NE) and engine load (intake pipe pressure PBA); An O ₂ sensor (50) that is arranged in the exhaust system of the internal combustion engine and generates an output whose characteristics change near the stoichiometric air-fuel ratio, and a basic fuel injection amount (Ti) determined based on the operating state of the internal combustion engine First control means (ECU 20) for controlling the air-fuel ratio of the internal combustion engine to the stoichiometric air-fuel ratio by correcting with a feedback correction coefficient (KO ₂ ) determined based on the output of the O ₂ sensor; And a plurality of storage areas divided according to the engine speed and the engine load value, and a learning correction coefficient (KTIMn) for correcting the basic fuel injection amount in each of the plurality of storage areas. The stored learning correction coefficient storage means (RAM 20c), the learning correction coefficient calculation means (ECU 20, S208 in the flowchart of FIG. 6) for calculating the learning correction coefficient based on the feedback correction coefficient, and the engine load is the engine speed A learning correction coefficient update that is set in accordance with and updates the calculated learning correction coefficient by overwriting the stored learning correction coefficient when the internal combustion engine is in a predetermined load range indicating that the engine is in steady operation. Means (ECU 20, S210, S212, S214 in the flowchart in FIG. 6, S316 in the flowchart in FIG. 8, flowchart in FIG. 5) S108), and the learning correction coefficient is searched from the engine speed and the engine load, and the basic fuel injection amount is corrected by at least the searched learning correction coefficient, whereby the air-fuel ratio is made the theoretical air-fuel ratio. Is configured to include second control means (ECU 20, S110 to S114 in the flowchart of FIG. 5) for controlling to different air-fuel ratios (lean burn control).

  The second control means executes the control (lean burn control) only when the learning correction coefficient is an updated value (S300 and S320 in the flowchart of FIG. 8, S100 in the flowchart of FIG. 5). It was configured as follows.

  The second control means executes the control (lean burn control) when the difference between the feedback correction coefficient and the updated learning correction coefficient is equal to or smaller than a predetermined value (S312 and S306 in the flowchart of FIG. 8). The configuration is as shown in S100 of the flowchart of FIG.

  In the above description, the learning correction coefficient KTIMn is used for lean burn control, but it may be used for open loop control at high load.

  Further, the learning correction coefficient KTIMn is stored in the EEPROM 20d, but other storage media may be used as long as it is nonvolatile.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an outboard motor including an hull including an air-fuel ratio control apparatus for an outboard motor internal combustion engine according to a first embodiment of the present invention. It is the schematic showing the engine and ECU shown in FIG. It is explanatory drawing showing the outline | summary of the air fuel ratio control performed by ECU shown in FIG. 3 is a main routine flowchart showing a lean burn control process executed by the ECU shown in FIG. 1. FIG. 5 is a sub-routine flowchart showing a target equivalence ratio calculation process executed in the flowchart of FIG. 4. FIG. 5 is a sub-routine flowchart showing correction processing of a learning correction coefficient map executed in the flowchart of FIG. 4. FIG. 5 is an explanatory diagram illustrating a learning correction coefficient map used in the flowchart of FIG. 4. FIG. 5 is a sub-routine flowchart showing processing related to determination of permission to shift to lean burn control executed in the flowchart of FIG. 4. 4 is an explanatory diagram showing a store value map used in the flowchart. 5 is a time chart showing lean burn control processing executed based on the flowchart of FIG. 4 is an explanatory diagram showing a learning correction coefficient map, a store value map, and the like used in the flowchart of FIG. Similarly, it is explanatory drawing showing a learning correction coefficient map, a store value map, etc. FIG. Similarly, it is explanatory drawing showing a learning correction coefficient map, a store value map, etc. FIG. It is explanatory drawing showing a part of learning correction coefficient map shown in FIG. It is explanatory drawing showing a learning correction coefficient map, a store value map, etc. similar to FIG. Similarly, it is explanatory drawing showing a learning correction coefficient map, a store value map, etc. FIG.

Explanation of symbols

10: Outboard motor, 14: Engine (internal combustion engine), 20: ECU (first and second control means, learning correction coefficient calculating means, learning correction coefficient updating means), 20c: RAM (learning correction coefficient storage means) 34: Intake pipe pressure sensor (operation state detection means), 44: Crank angle sensor (operation state detection means), 50: O ₂ sensor

Claims (3)

In the air-fuel ratio control apparatus for an outboard motor internal combustion engine that controls the air-fuel ratio of the internal combustion engine mounted on the outboard motor,
a. An operating state detecting means for detecting an operating state of the internal combustion engine including at least the engine speed and the engine load;
b. An O ₂ sensor disposed in the exhaust system of the internal combustion engine and generating an output whose characteristics change in the vicinity of the theoretical air-fuel ratio;
c. By correcting the basic fuel injection amount determined based on the operating state of the internal combustion engine with a feedback correction coefficient determined based on the output of the O ₂ sensor, the air-fuel ratio of the internal combustion engine is controlled to the stoichiometric air-fuel ratio. First control means to:
d. A learning correction comprising a plurality of storage areas divided according to the engine speed and the engine load value, and storing a learning correction coefficient for correcting the basic fuel injection amount in each of the plurality of storage areas Coefficient storage means;
e. Learning correction coefficient calculating means for calculating the learning correction coefficient based on the feedback correction coefficient;
f. When the engine load is set according to the engine speed and is within a predetermined load range indicating that the internal combustion engine is in steady operation , the calculated learning correction coefficient is overwritten on the stored learning correction coefficient. Learning correction coefficient updating means for updating
g. The learning correction coefficient is searched from the engine speed and the engine load, and the air-fuel ratio is made different from the stoichiometric air-fuel ratio by correcting the basic fuel injection amount with at least the searched learning correction coefficient. Second control means for controlling;
An air-fuel ratio control apparatus for an internal combustion engine for an outboard motor.   2. The air-fuel ratio control apparatus for an outboard motor internal combustion engine according to claim 1, wherein the second control means executes the control only when the learning correction coefficient is an updated value.   3. The outboard motor according to claim 1, wherein the second control unit executes the control when a difference between the feedback correction coefficient and the updated learning correction coefficient is a predetermined value or less. 4. An air-fuel ratio control apparatus for an internal combustion engine.

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