WO2011148517A1 - 内燃機関の空燃比制御装置 - Google Patents
内燃機関の空燃比制御装置 Download PDFInfo
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- WO2011148517A1 WO2011148517A1 PCT/JP2010/059486 JP2010059486W WO2011148517A1 WO 2011148517 A1 WO2011148517 A1 WO 2011148517A1 JP 2010059486 W JP2010059486 W JP 2010059486W WO 2011148517 A1 WO2011148517 A1 WO 2011148517A1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1439—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
- F02D41/1441—Plural sensors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1477—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
- F02D41/1479—Using a comparator with variable reference
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1477—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
- F02D41/1482—Integrator, i.e. variable slope
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1477—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
- F02D41/1483—Proportional component
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
- F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
- F02D41/2425—Particular ways of programming the data
- F02D41/2429—Methods of calibrating or learning
- F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
- F02D41/2454—Learning of the air-fuel ratio control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
- F02D41/1456—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio with sensor output signal being linear or quasi-linear with the concentration of oxygen
Definitions
- the present invention relates to an air-fuel ratio control apparatus for an internal combustion engine provided with a catalyst in an exhaust passage.
- a three-way catalyst exhaust gas purification catalyst unit
- the three-way catalyst has an “oxygen storage function” for storing oxygen flowing into the three-way catalyst and releasing the stored oxygen.
- the three-way catalyst is also simply referred to as “catalyst”.
- One of the conventional air-fuel ratio control devices (hereinafter referred to as “conventional device”) is provided with a downstream air-fuel ratio sensor disposed in the engine exhaust passage and downstream of the catalyst.
- the conventional apparatus obtains a “basic fuel injection amount for making the air-fuel ratio of the air-fuel mixture supplied to the engine coincide with the stoichiometric air-fuel ratio” based on the air amount sucked into the cylinder, and at least the basic fuel injection amount is downstream. Correction is made based on the output value of the side air-fuel ratio sensor.
- the exhaust gas flowing into the catalyst is referred to as “catalyst inflow gas”, and the exhaust gas flowing out from the catalyst is referred to as “catalyst outflow gas”.
- an air-fuel ratio smaller than the stoichiometric air-fuel ratio is called “rich air-fuel ratio”
- an air-fuel ratio larger than the stoichiometric air-fuel ratio is called “lean air-fuel ratio”.
- the air-fuel ratio of the air-fuel mixture supplied to the engine is referred to as “engine air-fuel ratio”.
- the downstream air-fuel ratio sensor used in the conventional apparatus is generally a concentration cell type oxygen concentration sensor.
- the output value Voxs of the downstream air-fuel ratio sensor is a value near the maximum output value Max when the air-fuel ratio of the catalyst outflow gas is smaller than the stoichiometric air-fuel ratio as shown by the curve C1 in FIG. Become.
- the output value Voxs of the downstream air-fuel ratio sensor becomes a value near the minimum output value Min when the state in which the air-fuel ratio of the catalyst outflow gas is larger than the stoichiometric air-fuel ratio continues.
- the output value Voxs of the downstream air-fuel ratio sensor changes from a value near the maximum output value Max to a value near the minimum output value Min when the air-fuel ratio of the catalyst outflow gas changes from the rich air-fuel ratio to the lean air-fuel ratio. It changes rapidly.
- the output value Voxs of the downstream air-fuel ratio sensor rapidly increases from a value near the minimum output value Min to a value near the maximum output value Max. Change.
- the output value Voxs becomes a value near the minimum output value Min.
- the conventional device sets the feedback amount of the air-fuel ratio so that the output value Voxs of the downstream air-fuel ratio sensor matches the “target value VREF set to the value corresponding to the theoretical air-fuel ratio (that is, the median value Vmid)”. Calculation is based on proportional / integral control (PI control).
- This air-fuel ratio feedback amount is also referred to as a “sub-feedback amount” for convenience.
- the conventional apparatus feedback-controls the air-fuel ratio of the air-fuel mixture supplied to the engine by correcting the basic fuel injection amount with the sub-feedback amount (see, for example, JP-A-2005-171982).
- FIG. 28 is a time chart showing a state of air-fuel ratio feedback control by such a conventional apparatus.
- the conventional apparatus maintains the target value VREF at a constant value (a reference value Vf that is a value in the vicinity of the median value Vmid), and determines whether the air-fuel ratio of the catalyst outflow gas is a rich air-fuel ratio or a lean air-fuel ratio.
- the conventional apparatus determines the “air-fuel ratio of the engine (required air-fuel ratio) required for efficiently purifying the exhaust gas using the catalyst” based on the “output value Voxs and reference value Vf”.
- the conventional apparatus when the output value Voxs is larger than the reference value Vf (for example, time t1 to time t2, time t3 to time t4, and time t5 to time t6), It is determined that the air-fuel ratio is a rich air-fuel ratio, and the required air-fuel ratio is determined to be a lean air-fuel ratio (that is, a lean request is generated). When the lean request is generated, the conventional apparatus controls the air / fuel ratio of the engine to the lean air / fuel ratio.
- Vf for example, time t1 to time t2, time t3 to time t4, and time t5 to time t6
- the conventional device determines that the air-fuel ratio of the catalyst outflow gas is a lean air-fuel ratio, and requests It is determined that the air-fuel ratio is a rich air-fuel ratio (that is, a rich request is generated).
- the conventional device controls the air / fuel ratio of the engine to the rich air / fuel ratio.
- the output value Voxs increases and becomes larger than the reference value Vf.
- the air-fuel ratio of the engine becomes too large or too small.
- nitrogen oxides (NOx) or unburned substances (CO, HC, etc.) are not completely purified by the catalyst. It may be discharged outside the organization.
- NOx emission amount increases before and after time t2, time t4, and time t6.
- the air-fuel ratio of the catalyst outflow gas is “a rich air-fuel ratio with a large absolute value of the difference from the theoretical air-fuel ratio. Is.
- the amount of oxygen stored in the catalyst (hereinafter also referred to as “oxygen storage amount OSA”) is substantially “0”. Therefore, the conventional apparatus determines that a lean request has occurred and sets the air / fuel ratio of the engine to the lean air / fuel ratio.
- the oxygen storage amount OSA increases.
- the catalyst can efficiently store oxygen. Therefore, immediately after time t1, most of the excess oxygen contained in the catalyst inflow gas is occluded by the catalyst.
- the output value Voxs of the downstream air-fuel ratio sensor changes with a delay with respect to the change in the oxygen partial pressure of the catalyst outflow gas. This is presumed to be due to the following factors. (1) Since there is a distance between the catalyst and the downstream air-fuel ratio sensor, it takes time until the catalyst outflow gas reaches the element of the downstream air-fuel ratio sensor. (2) Since the downstream air-fuel ratio sensor is generally provided with a protective cover, it takes time until the catalyst outflow gas reaches the element of the downstream air-fuel ratio sensor. (3) Since the element of the downstream air-fuel ratio sensor is covered with “a layer for allowing the oxygen-balanced gas to reach the element (for example, diffusion resistance layer)”, the oxygen partial pressure of the gas reaching the element The change in is delayed. This delay becomes significant when there is oxygen or unburned material accumulated so far around the downstream air-fuel ratio sensor element.
- the output value Voxs Due to the delay in the change of the output value Voxs, the output value Voxs is larger than the reference value Vf until the time t2, so that the conventional apparatus continues to determine that the lean request is generated until the time t2. Therefore, the air-fuel ratio of the engine continues to be set to a lean air-fuel ratio. As a result, the oxygen storage amount OSA continues to increase and reaches a value near the “maximum oxygen storage amount Cmax that is the maximum value of the catalyst oxygen storage amount OSA” immediately before time t2 or time t2.
- the catalyst inflow gas contains a large amount of NOx (nitrogen oxide).
- NOx nitrogen oxide
- the oxygen storage amount OSA reaches a value close to the maximum oxygen storage amount Cmax, the catalyst cannot sufficiently purify NOx. As a result, a relatively large amount of NOx is discharged downstream of the catalyst in the period near time t2.
- the rich request is generated even when the oxygen storage amount OSA is close to “0” (for example, immediately before time t1, immediately before time t3, and immediately before time t5). Is determined. As a result, excessive unburned matter flows into the catalyst, and the unburned matter may be discharged downstream of the catalyst without being purified.
- the air-fuel ratio of the engine may be set to “an air-fuel ratio that is undesirable for the exhaust gas purification action of the catalyst”.
- the present invention has been made to address the above-described problems. That is, one of the objects of the present invention is to control the air-fuel ratio of the engine so that the air-fuel ratio of the catalyst inflow gas becomes “the air-fuel ratio desirable for the exhaust gas purification action of the catalyst”. It is to provide a control device.
- One aspect of an air-fuel ratio control apparatus for an internal combustion engine is: A catalyst disposed in an exhaust passage of the internal combustion engine; a downstream air-fuel ratio sensor disposed in the exhaust passage and downstream of the catalyst; and an air-fuel ratio control means.
- the downstream air-fuel ratio sensor includes an element for detecting the air-fuel ratio.
- the element shows an output value that changes in accordance with the oxygen partial pressure of a gas reaching the element (hereinafter also referred to as “element-arriving gas”).
- the downstream air-fuel ratio sensor is preferably a concentration cell type oxygen concentration sensor (O 2 sensor).
- O 2 sensor concentration cell type oxygen concentration sensor
- the output value of the downstream air-fuel ratio sensor increases as “the air-fuel ratio of the element-arriving gas” becomes smaller (richer).
- the downstream air-fuel ratio sensor may be a limiting current type wide-range air-fuel ratio sensor or the like.
- the downstream air-fuel ratio sensor When the downstream air-fuel ratio sensor is a limit current type wide-range air-fuel ratio sensor, the output value of the downstream air-fuel ratio sensor becomes smaller as the “air-fuel ratio of the element reaching gas” becomes smaller (richer). Further, the downstream air-fuel ratio sensor may be a sensor having a zirconia element or a sensor having a titania element.
- the air-fuel ratio control means increases the air-fuel ratio of the engine during a lean request generation period in which the air-fuel ratio of the engine needs to be increased to bring the output value of the downstream air-fuel ratio sensor close to a predetermined target value. To do.
- the air-fuel ratio of the engine may be gradually increased or set to a predetermined (constant or variable) lean air-fuel ratio.
- the air-fuel ratio control means controls the air-fuel ratio of the engine during a rich request generation period in which the air-fuel ratio of the engine needs to be decreased in order to bring the output value of the downstream air-fuel ratio sensor close to the target value. Decrease.
- the air-fuel ratio of the engine may be gradually decreased or set to a predetermined (constant or variable) rich air-fuel ratio.
- feedback control air-fuel ratio feedback control or sub-feedback control
- the downstream air-fuel ratio sensor is a concentration cell type oxygen concentration sensor
- the air-fuel ratio of the catalyst outflow gas is a rich air-fuel ratio
- the air-fuel ratio of the engine is controlled to the lean air-fuel ratio.
- the downstream air-fuel ratio sensor is a concentration cell type oxygen concentration sensor
- the output value of the downstream air-fuel ratio sensor is smaller than the target value
- the air-fuel ratio of the catalyst outflow gas is a lean air-fuel ratio
- the downstream air-fuel ratio sensor is a limit current type wide-range air-fuel ratio sensor
- the air-fuel ratio of the catalyst outflow gas is a lean air-fuel ratio. Therefore, the rich request is generated ", and the air-fuel ratio of the engine is controlled to the rich air-fuel ratio.
- the downstream air-fuel ratio sensor is a limit current type wide-area air-fuel ratio sensor
- the output value of the downstream air-fuel ratio sensor is smaller than the target value
- the air-fuel ratio of the catalyst outflow gas is a rich air-fuel ratio. Therefore, the lean request is generated ", so that the air-fuel ratio of the engine is controlled to the lean air-fuel ratio.
- the air-fuel ratio control means includes target value changing means.
- the target value changing means includes The target value used in the feedback control is set to a predetermined reference value, and any one of the “region larger than the reference value and the region smaller than the reference value” is one of the regions and the downstream side. It gradually approaches the predetermined value within the region where the output value of the air-fuel ratio sensor exists as time passes.
- the predetermined reference value is that the oxygen partial pressure of “the gas reaching the element of the downstream air-fuel ratio sensor (element-arriving gas)” is “when the air-fuel ratio of the element-arriving gas is the stoichiometric air-fuel ratio”.
- the oxygen partial pressure it is a value within a “predetermined range” including “a value indicated by the output value of the downstream air-fuel ratio sensor (hereinafter also referred to as“ theoretical air-fuel ratio equivalent value ”)”.
- one aspect of the air-fuel ratio control apparatus for an internal combustion engine according to the present invention controls the output value of the downstream air-fuel ratio sensor so as not to be excessive or small (that is, the oxygen storage amount OSA is a value near “0”).
- the output value of the downstream air-fuel ratio sensor can be brought close to the reference value while avoiding the vicinity of the maximum oxygen storage amount Cmax).
- one aspect of the air-fuel ratio control apparatus for an internal combustion engine according to the present invention prevents the “excessive oxygen or excessive unburned matter” from flowing into the catalyst in order to efficiently perform the exhaust purification action of the catalyst.
- the “engine air-fuel ratio” can be controlled. Therefore, one aspect of the air-fuel ratio control apparatus can maintain emissions well.
- the catalyst is properly purifying the substance to be purified. Therefore, when the output value of the downstream air-fuel ratio sensor fluctuates in the vicinity of the reference value, the target value differs from the reference value (the value between the current downstream air-fuel ratio sensor output value and the reference value). ) Is not necessary.
- the absolute value of the difference between the output value of the downstream side air-fuel ratio sensor and the reference value is large, it means that a large amount of excess oxygen or excess unburned matter has reached the downstream side air-fuel ratio sensor.
- FIG. 14 is a flowchart showing a routine executed by the CPU of the air-fuel ratio control apparatus (second control apparatus) according to the second embodiment of the present invention.
- FIG. 15 is a flowchart showing a routine executed by the CPU of the air-fuel ratio control apparatus (third control apparatus) according to the third embodiment of the present invention.
- FIG. 16 is a flowchart showing a routine executed by the CPU of the air-fuel ratio control apparatus (fourth control apparatus) according to the fourth embodiment of the present invention.
- FIG. 17 is a flowchart showing a routine executed by the CPU of the air-fuel ratio control apparatus (fifth control apparatus) according to the fifth embodiment of the present invention.
- the main body portion 20 includes a cylinder block portion and a cylinder head portion.
- the main body portion 20 includes a plurality (four) of combustion chambers (first cylinder # 1 to fourth cylinder # 4) 21 including a piston top surface, a cylinder wall surface, and a lower surface of the cylinder head portion.
- the exhaust system 40 includes an exhaust manifold 41, an exhaust pipe (exhaust pipe) 42, an upstream catalyst 43, and a downstream catalyst 44.
- the upstream side catalyst (catalyst device (unit) for exhaust purification) 43 supports “noble metal as a catalyst material” and “ceria (Ce02) as an oxygen storage material” on a support including ceramic, and stores oxygen.
- -It is a three-way catalyst having a release function (oxygen storage function).
- the upstream catalyst 43 is disposed (intervened) in the exhaust pipe 42. When the upstream catalyst 43 reaches a predetermined activation temperature, it exhibits a “catalytic function for simultaneously purifying unburned substances (HC, CO, H 2, etc.) and nitrogen oxides (NOx)” and “oxygen storage function”. .
- the upstream catalyst 43 is also referred to as a start catalytic converter (SC) or a first catalyst.
- the first control device includes a hot-wire air flow meter 51, a throttle position sensor 52, an engine speed sensor 53, a water temperature sensor 54, an upstream air-fuel ratio sensor 55, a downstream air-fuel ratio sensor 56, and an accelerator opening sensor 57. .
- the throttle position sensor 52 detects the opening degree of the throttle valve 34 and outputs a signal indicating the throttle valve opening degree TA.
- the downstream air-fuel ratio sensor 56 includes a protective cover that covers the element portion including the solid electrolyte layer, the exhaust gas side electrode layer, the atmosphere side electrode layer, and the diffusion resistance layer.
- the protective cover is made of metal and includes a plurality of through holes.
- the exhaust gas that has reached the outside of the protective cover reaches the outside of the element portion through the through hole.
- the diffusion resistance layer is formed by combining the gas that has reached the outer peripheral portion of the downstream air-fuel ratio sensor 56 with the oxygen-equilibrium gas (the gas after combining the existing unburned material with the existing oxygen, Or a gas containing only excess oxygen).
- the accelerator opening sensor 57 shown in FIG. 1 detects the operation amount of the accelerator pedal AP operated by the driver, and outputs a signal indicating the operation amount Accp of the accelerator pedal AP.
- the backup RAM provided in the electric control device 60 is a battery mounted on the vehicle regardless of the position of an ignition key switch (not shown) of the vehicle on which the engine 10 is mounted (any one of an off position, a start position, an on position, etc.). It is supposed to receive power supply from. When receiving power from the battery, the backup RAM stores data according to an instruction from the CPU (data is written) and holds (stores) the data so that the data can be read. The backup RAM cannot retain data when the power supply from the battery is interrupted, for example, when the battery is removed from the vehicle. In other words, the data held so far is lost (destroyed).
- the interface of the electric control device 60 is connected to the sensors 51 to 57 so as to supply signals from the sensors 51 to 57 to the CPU. Further, the interface sends an instruction signal (drive signal) or the like to the ignition plug 24 of each cylinder, the fuel injection valve 25 of each cylinder, the intake valve control device 26, the throttle valve actuator 34a, etc. in accordance with an instruction from the CPU. It is like that.
- the electric control device 60 sends an instruction signal to the throttle valve actuator 34a so that the throttle valve opening TA increases as the acquired accelerator pedal operation amount Accp increases.
- a predetermined range (Vmid ⁇ v2 to Vmid + ⁇ v1) including a value (for example, median value Vmid) indicated by the output value Voxs of the downstream air / fuel ratio sensor when the air / fuel ratio is the oxygen partial pressure when the air / fuel ratio is the theoretical air / fuel ratio. It is a value in.
- the determination of the air-fuel ratio is performed based on a comparison between the output value Voxs of the downstream air-fuel ratio sensor and the target value VREF, as will be described later.
- the state of the catalyst 43 is a state where oxygen is excessive (a state where the oxygen storage amount OSA is larger than another predetermined value OSAmax larger than the predetermined value OSAmin). Therefore, when the determination of the air-fuel ratio is lean, in order for the catalyst 43 to purify the “substance to be purified” with high purification efficiency, the air-fuel ratio of the catalyst inflow gas (and hence the air-fuel ratio of the engine) is set to the rich air. It is necessary to set the fuel ratio. Therefore, the first control device determines that the rich request is generated when the determination of the air-fuel ratio is lean. When a rich request is occurring, the engine air / fuel ratio is reduced. In other words, the air-fuel ratio of the engine is controlled to be a “rich air-fuel ratio” that is an air-fuel ratio smaller than the stoichiometric air-fuel ratio.
- the first control device determines that the air-fuel ratio is “rich” when the output value Voxs is larger than the target value VREF. Accordingly, the first control device determines that a lean request has occurred when the output value Voxs is greater than the target value VREF. The first control device determines that the air-fuel ratio is “lean” when the output value Voxs is smaller than the target value VREF. Therefore, the first control device determines that a rich request has occurred when the output value Voxs is smaller than the target value VREF.
- the first control device acquires the “maximum value Vmax and minimum value Vmin” of the output value Voxs.
- the first control device determines whether a lean request is currently generated (that is, whether the air / fuel ratio of the engine is set to a lean air / fuel ratio) or a rich request is generated (that is, the air / fuel ratio of the engine is rich).
- the target value VREF determination threshold value VREF is determined according to “maximum value Vmax and minimum value Vmin” as shown in Table 1 below.
- the minimum value Vmin is larger than the reference value Vf.
- the first control device sets “a value obtained by adding a positive constant value B1 to the minimum value Vmin (Vmin + B1)” as the target value VREF (see FIG. 5C).
- the value B1 is also referred to as a second change value.
- the target value VREF set for determining whether or not the fuel ratio has changed to rich is also referred to as “a rich determination target value VREFR or a rich determination threshold value VREFR”.
- the value A2 is also referred to as a first change value
- the value B2 is also referred to as a second change value.
- the value A1 and the value A2 may be equal to each other.
- the value B1 and the value B2 may be the same value B.
- the first control device determines that the air-fuel ratio is “lean” and determines that a “rich request” has occurred. Therefore, after time t6, the air-fuel ratio of the engine starts to decrease.
- the reference value Vf is set as the target value VREF (the target value VREFR for rich determination) (see point P4).
- the first control apparatus determines that the air-fuel ratio is “rich” and determines that a “lean request” has occurred. Therefore, the air-fuel ratio of the engine starts to increase after time t8.
- the reference value Vf is set as the target value VREF (lean determination target value VREFL) based on the determination method (see point P5).
- the first control device determines that the air-fuel ratio is “lean” and determines that a “rich request” has occurred. Therefore, after time t10, the air-fuel ratio of the engine starts to decrease.
- the first control apparatus gradually brings the target value VREF closer to the reference value Vf, thereby increasing the amplitude of the output value Voxs.
- the output value Voxs can be brought close to the reference value Vf while keeping the value small.
- a small amplitude of the output value Voxs means that a large amount of oxygen or unburned matter does not flow out from the catalyst 43.
- the first control device purifies the output value Voxs to the reference value Vf while purifying the unburned matter and NOx by the catalyst 43. It can be moved to the vicinity.
- the first control device gradually brings the target value VREF closer to the reference value Vf even when the output value Voxs becomes a value near the minimum output value Min. . Therefore, as in the case shown in FIG. 6, the first control device can bring the output value Voxs closer to the reference value Vf while keeping the amplitude of the output value Voxs small.
- MapX (a1, a2,...)” Is a “table having arguments a1, a2,...” And represents “a table for obtaining the value X”.
- the CPU of the first control device repeatedly executes the fuel injection control routine shown in FIG. 8 for each cylinder every time the crank angle of any cylinder reaches a predetermined crank angle before the intake top dead center. It has become.
- the predetermined crank angle is, for example, BTDC 90 ° CA (90 ° crank angle before intake top dead center).
- a cylinder whose crank angle coincides with the predetermined crank angle is also referred to as a “fuel injection cylinder”.
- the CPU calculates the commanded fuel injection amount (final fuel injection amount) Fi and instructs fuel injection by this fuel injection control routine.
- FC condition a fuel cut condition
- step 810 makes a “No” determination at step 810 to sequentially perform the processes from step 820 to step 860 described below. Thereafter, the CPU proceeds to step 895 to end the present routine tentatively.
- Step 820 The CPU determines the target air-fuel ratio abyfr (upstream target air-fuel ratio abyfr) based on the operating state of the engine 10.
- the target value VREF is set to a stoichiometric air fuel ratio stoichi (for example, 14.6).
- Step 830 The CPU sets the “intake air amount Ga measured by the air flow meter 51, the engine rotational speed NE acquired based on the signal of the engine rotational speed sensor 53, and the lookup table MapMc (Ga, NE)”. Based on this, “the amount of air taken into the fuel injection cylinder (that is, the in-cylinder intake air amount Mc (k))” is acquired.
- the in-cylinder intake air amount Mc (k) is stored in the RAM while corresponding to each intake stroke.
- the in-cylinder intake air amount Mc (k) may be calculated by a well-known air model (a model constructed according to a physical law simulating the behavior of air in the intake passage).
- Step 840 The CPU obtains the basic fuel injection amount Fb by dividing the in-cylinder intake air amount Mc (k) by the target air-fuel ratio abyfr.
- the basic fuel injection amount Fb is a feedforward amount of the fuel injection amount necessary to obtain the target air-fuel ratio abyfr (theoretical air-fuel ratio stoich in this example).
- This step 840 constitutes a feedforward control means for making the air-fuel ratio of the air-fuel mixture supplied to the engine (the air-fuel ratio of the engine) coincide with the target air-fuel ratio abyfr.
- the main FB learning value KG and the main feedback coefficient FAF are obtained by a routine shown in FIG.
- the main FB learning value KG is stored in the backup RAM.
- Steps 820 to 860 constitute command fuel injection amount control means for “controlling the command fuel injection amount Fi so that the air-fuel ratio of the engine matches the target air-fuel ratio abyfr”.
- step 810 the CPU makes a “Yes” determination at step 810 to directly proceed to step 895 to end the present routine tentatively. In this case, since fuel injection by the process of step 860 is not executed, fuel cut control (fuel supply stop control) is executed.
- the CPU repeatedly executes the “main feedback control routine” shown in the flowchart of FIG. 9 every elapse of a predetermined time ta. Therefore, when the predetermined timing comes, the CPU starts the process from step 900 and proceeds to step 905 to determine whether or not the “main feedback control condition (upstream air-fuel ratio feedback control condition)” is satisfied.
- the main feedback control condition is satisfied when all of the following conditions are satisfied.
- (A1) The upstream air-fuel ratio sensor 55 is activated.
- (A2) The engine load KL is equal to or less than the threshold KLth.
- the load KL is a load factor obtained by the following equation (1).
- an accelerator pedal operation amount Accp may be used.
- Mc is the in-cylinder intake air amount
- ⁇ is the air density (unit is (g / l))
- L is the exhaust amount of the engine 10 (unit is (l))
- “4” is the engine.
- the number of cylinders is 10.
- KL (Mc / ( ⁇ ⁇ L / 4)) ⁇ 100% (1)
- the CPU makes a “Yes” determination at step 905 to sequentially perform the processing from step 910 to step 950 described below to obtain the main feedback amount DFi, the main feedback coefficient FAF, and the like.
- Step 910 The CPU acquires the feedback control output value Vabyfc according to the following equation (2).
- Vabyfs is an output value of the upstream air-fuel ratio sensor 55
- Vafsfb is a sub-feedback amount calculated based on the output value Voxs of the downstream air-fuel ratio sensor 56.
- Step 915 The CPU obtains the feedback control air-fuel ratio abyfsc by applying the feedback control output value Vabyfc to the table Mapyfs shown in FIG. 2 as shown in the following equation (3).
- abyfsc Mapabyfs (Vabyfc) (3)
- Step 920 The CPU “in-cylinder fuel supply amount Fc (k ⁇ N)” which is “the amount of fuel actually supplied to the combustion chamber 21 at a time point N cycles before the current time” according to the following equation (4): “ That is, the CPU divides “the in-cylinder intake air amount Mc (k ⁇ N) at a point N cycles before the current point (ie, N ⁇ 720 ° crank angle)” by “the feedback control air-fuel ratio abyfsc”. Thus, the in-cylinder fuel supply amount Fc (k ⁇ N) is obtained.
- Fc (k ⁇ N) Mc (k ⁇ N) / abyfsc (4)
- the in-cylinder intake air amount Mc (k ⁇ N) N cycles before the current time is divided by the feedback control air-fuel ratio abyfsc. This is because “a time corresponding to N cycles” is required until “the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber 21” reaches the upstream air-fuel ratio sensor 55.
- Step 935 The CPU obtains the main feedback amount DFi according to the following equation (7).
- Gp is a preset proportional gain
- Gi is a preset integral gain.
- the “value SDFc” in the equation (7) is “an integral value of the in-cylinder fuel supply amount deviation DFc”. That is, the CPU calculates the “main feedback amount DFi” by proportional-integral control for making the feedback control air-fuel ratio abyfsc coincide with the target air-fuel ratio abyfr.
- This main feedback amount DFi is converted into a main feedback coefficient FAF in step 945 described later.
- DFi Gp ⁇ DFc + Gi ⁇ SDFc (7)
- Step 940 The CPU adds the in-cylinder fuel supply amount deviation DFc obtained in the above step 930 to the integral value SDFc of the in-cylinder fuel supply amount deviation DFc at that time, so that a new in-cylinder fuel supply amount deviation DFc is obtained. An integral value SDFc is obtained.
- Step 945 The CPU calculates the main feedback coefficient FAF by applying the main feedback amount DFi and the basic fuel injection amount Fb (k ⁇ N) to the following equation (8). That is, the main feedback coefficient FAF is obtained by dividing “the value obtained by adding the main feedback amount DFi to the basic fuel injection amount Fb (k ⁇ N) N strokes before the current time” by the “basic fuel injection amount Fb (k ⁇ N)”. It is calculated by doing. As described above, the main feedback amount DFi is obtained by the proportional integral control, and this main feedback amount DFi is converted into the main feedback coefficient FAF.
- FAF (Fb (k ⁇ N) + DFi) / Fb (k ⁇ N) (8)
- Step 950 The CPU obtains the weighted average value of the main feedback coefficient FAF as the main feedback coefficient average value FAFAV according to the following equation (9).
- the main feedback coefficient average value FAFAV is hereinafter also referred to as “correction coefficient average value FAFAV”.
- the main feedback coefficient average value FAFAV is a value correlated with the average value of the main feedback amount DFi.
- FAFAVnew is the updated correction coefficient average value FAFAV, and the FAFAVnew is stored as a new correction coefficient average value FAFAV.
- the value q is a constant larger than 0 and smaller than 1.
- the main feedback coefficient average value FAFAV may be an average value of the main feedback coefficient FAF in a predetermined period.
- FAFAVnew q ⁇ FAF + (1-q) ⁇ FAFAV (9)
- the CPU proceeds to step 955 and subsequent steps, and updates (acquires and calculates) the main FB learning value KG. That is, the CPU obtains the main FB learning value KG for bringing the main feedback coefficient FAF closer to the reference value (basic value) “1” based on the correction coefficient average value FAFAV.
- step 955 the CPU proceeds to step 955 to determine whether or not the learning condition is satisfied at the present time.
- the learning condition is satisfied every time a natural number times the time interval (predetermined time ta) at which the routine of FIG. 9 is executed elapses.
- the CPU makes a “No” determination at step 955 to directly proceed to step 995 to end the present routine tentatively.
- the main FB learning value KG is not updated.
- the CPU makes a “Yes” determination at step 955 to proceed to step 960 to determine whether or not the value of the correction coefficient average value FAFAV is equal to or greater than the value (1 + d ⁇ ). judge.
- the value d ⁇ is a positive predetermined value, for example, 0.02.
- the CPU proceeds to step 965 to increase the main FB learning value KG by a positive predetermined value ⁇ KG. Thereafter, the CPU proceeds to step 995 to end the present routine tentatively.
- the main FB learning value KG is stored in the backup RAM.
- step 970 When the CPU proceeds to step 970 and the value of the correction coefficient average value FAFAV is larger than the value (1-d ⁇ ), the CPU directly proceeds from step 970 to step 995 to end the present routine tentatively. That is, when the correction coefficient average value FAFAV is a value between the value (1 ⁇ d ⁇ ) and the value (1 + d ⁇ ), the main FB learning value KG is not updated.
- step 905 determines “No” in step 905, and sequentially performs the processing from step 980 to step 992 described below.
- Step 980 The CPU sets the value of the main feedback amount DFi to “0”.
- Step 985 The CPU sets the value of the main feedback coefficient FAF to “1”.
- Step 990 The CPU sets the integral value SDFc of the in-cylinder fuel supply amount deviation to “0”.
- Step 992 The CPU sets the correction coefficient average value FAFAV to “1”. Thereafter, the CPU proceeds to step 995 to end the present routine tentatively.
- the value of the main feedback amount DFi is set to “0”, and the value of the main feedback coefficient FAF is set to “1”. Accordingly, the basic fuel injection amount Fb is not corrected by the main feedback coefficient FAF. However, even in such a case, the basic fuel injection amount Fb is corrected by the main FB learning value KG.
- Sub feedback control> In order to calculate the sub feedback amount Vafsfb, the CPU executes a “sub feedback control routine” shown in FIG. 10 every time a predetermined time elapses.
- the CPU starts processing from step 1000 in FIG. 10 and proceeds to step 1005 to determine whether or not the sub feedback control condition is satisfied.
- the sub-feedback control condition is satisfied when all of the following conditions are satisfied.
- (B1) The main feedback control condition is satisfied.
- (B2) The downstream air-fuel ratio sensor 56 is activated.
- the CPU makes a “Yes” determination at step 1005 to execute processing from step 1010 to step 1040 described below, and then proceeds to step 1095 to end the present routine tentatively.
- Step 1010 The CPU reads the target value VREF (target value of the output value Voxs of the downstream air-fuel ratio sensor).
- the target value VREF is determined by a routine described later.
- Step 1015 The CPU obtains an “output deviation amount DVoxs” that is a difference between the “target value VREF” and the “output value Voxs of the downstream air-fuel ratio sensor 56” according to the following equation (10). That is, the CPU obtains the output deviation amount DVoxs by subtracting the output value Voxs from the target value VREF.
- DVoxs VREF ⁇ Voxs (10)
- Step 1020 The CPU obtains a sub feedback amount Vafsfb according to the following equation (11).
- Kp is a preset proportional gain (proportional constant)
- Ki is a preset integral gain (integral constant)
- Kd is a preset differential gain (differential constant).
- SDVoxs is an integral value of the output deviation amount DVoxs
- DDVoxs is a differential value of the output deviation DVoxs.
- Vafsfb Kp ⁇ DVoxs + Ki ⁇ SDVoxs + Kd ⁇ DDVoxs (11)
- Step 1025 The CPU obtains a new output deviation amount integrated value SDVoxs by adding “the output deviation amount DVoxs obtained in step 1015” to “the integrated value SDVoxs of the output deviation amount at that time”.
- Step 1030 The CPU obtains a new value by subtracting “the output deviation amount (previous output deviation amount DVoxsold) calculated when this routine was executed last time” from “the output deviation amount DVoxs calculated in Step 1015” above. A differential value DDVoxs of the output deviation amount is obtained.
- Step 1035 The CPU stores “the output deviation amount DVoxs calculated in step 1015” as “the previous output deviation amount DVoxsold”.
- the CPU calculates the “sub feedback amount Vafsfb” by proportional / integral / differential (PID) control for making the output value Voxs of the downstream air-fuel ratio sensor 56 coincide with the target value VREF.
- the sub feedback amount Vafsfb is used to calculate the feedback control output value Vabyfc, as shown in the above-described equation (2).
- Step 1040 The CPU updates the sub FB learning value Vafsfbg according to the following equation (12).
- the left side Vafsfbg (k + 1) of the equation (12) represents the updated sub FB learning value Vafsfbg.
- the value ⁇ is an arbitrary value from 0 to less than 1.
- Vafsfbg (k + 1) ⁇ ⁇ Vafsfbg + (1 ⁇ ) ⁇ Ki ⁇ SDVoxs (12)
- the sub FB learning value Vafsfbg is a value obtained by applying “filter processing for noise removal” to “integration term Ki ⁇ SDVoxs of the sub feedback amount Vafsfb”.
- the sub FB learning value Vafsfbg is a value corresponding to the steady component (integral term) of the sub feedback amount Vafsfb.
- step 1005 when the sub feedback control condition is not satisfied at the time when the CPU executes the process of step 1005, the CPU makes a “No” determination at step 1005 to execute the processes of step 1045 and step 1050 described below. Do in order. Thereafter, the CPU proceeds to step 1095 to end the present routine tentatively.
- Step 1045 The CPU adopts the sub FB learning value Vafsfbg as the value of the sub feedback amount Vafsfb.
- Step 1050 The CPU sets the integrated value SDVoxs of the output deviation amount to “0”.
- the sub feedback amount Vafsfb is obtained so that the output value Voxs matches the target value VREF, and this sub feedback amount Vafsfb is reflected in the commanded fuel injection amount Fi (see step 910 in FIG. 9). .) Accordingly, the command fuel injection amount Fi is feedback-controlled so that the output value Voxs matches the target value VREF.
- ⁇ Target value VREF determination> The CPU executes a “target value determination routine” shown in FIG. 11 every time a predetermined time elapses in order to determine “the target value VREF used for sub-feedback control”. Therefore, when the predetermined timing comes, the CPU starts the process from step 1100 in FIG. 11 and proceeds to step 1110 to determine whether or not the above-mentioned “sub feedback control condition” is satisfied.
- the CPU makes a “No” determination at step 1110 to proceed to step 1120 to set the value of the target value convergence control execution flag XVSFB to “0”.
- the target value convergence control execution flag XVSFB indicates that “target value convergence control (target value change control) for converging the target value VREF to the reference value Vf” is executed when the value is “1”. When the value is “0”, it indicates that “target value convergence control” is not executed.
- the value of the target value convergence control execution flag XVSFB is the initial routine executed by the CPU when the ignition key switch of the “vehicle not shown in which the engine 10 is mounted” is changed from the off position to the on position. Is set to “0”.
- step 1130 the CPU proceeds to step 1130 to set the value of the target value determination request flag XVREFreq to “1”, proceeds to step 1195, and once ends this routine.
- the target value determination request flag XVREFreq indicates that when the value is “1”, it is necessary to newly determine the target value VREF (there is a request for updating the target value VREF).
- the target value determination request flag XVREFreq indicates that it is not necessary to newly determine the target value VREF when the value is “0”.
- the value of the target value determination request flag XVREFreq is set to “1” in the above-described initial routine. Thereafter, the CPU proceeds to step 1195 to end the present routine tentatively.
- step 1110 the CPU makes a “Yes” determination at step 1110 to proceed to step 1040.
- step 1140 the CPU determines whether the value of the target value determination request flag XVREFreq is “1”.
- the value of the target value determination request flag XVREFreq is set to “1” in the initial routine described above or in step 1130 described above. Accordingly, the CPU makes a “Yes” determination at step 1140 to proceed to step 1050 to determine the target value VREF according to the above-described ⁇ determination method>.
- step 1150 the CPU proceeds to step 1150 via step 1200 in FIG. 12, and determines whether the value of the target value convergence control execution flag XVSFB is “0” or not. judge.
- the value of the target value convergence control execution flag XVSFB is set to “0” in the initial routine described above or step 1120 described above. Accordingly, the CPU makes a “Yes” determination at step 1202 to proceed to step 1204 to determine whether or not the output value Voxs of the downstream air-fuel ratio sensor is larger than the reference value Vf.
- the CPU makes a “Yes” determination at step 1204 to proceed to step 1206 to set the value of the rich determination flag XR to “1”.
- the value of the rich determination flag XR is “1”, it indicates that the air-fuel ratio is determined to be “rich”, and accordingly, a lean request is generated. Note that the value of the rich determination flag XR is set to “0” in the above-described initial routine.
- the CPU makes a “No” determination at step 1204 to proceed to step 1208 to set the value of the rich determination flag XR to “0”.
- the value of the rich determination flag XR is “0”, it indicates that the air-fuel ratio is determined to be “lean”, and accordingly, a rich request is generated.
- step 1210 the CPU proceeds to step 1210 to set the value of the target value convergence control execution flag XVSFB to “1” and tentatively set the reference value Vf as the target value VREF. Thereafter, the CPU proceeds to step 1195 in FIG. 11 via step 1295 to end the target value determination routine once.
- the sub feedback amount Vafsfb is calculated so that the output value Voxs matches the “target value VREF set to the reference value Vf”.
- step 1110 the CPU makes a “Yes” determination at step 1110 to proceed to step 1140.
- the target value determination request flag XVREFreq is still “1”. Accordingly, the CPU proceeds from step 1140 to step 1150, and proceeds to step 1202 via step 1200 in FIG.
- the CPU makes a “Yes” determination at step 1212 to proceed to step 1214.
- the “maximum value Vmax of the output value Voxs” has been acquired since the rich determination flag XR has been changed to “1”. Determine.
- the maximum value Vmax is acquired separately by a routine not shown.
- the CPU also acquires the minimum value Vmin of the output value Voxs.
- the CPU acquires the output value Voxs of the downstream side air-fuel ratio sensor every elapse of the predetermined time Tb.
- the CPU subtracts the output value Voxs before the predetermined time Tb (hereinafter referred to as “previous output value Voxszen”) from the newly acquired output value Voxs.
- Value (Voxs ⁇ Voxszen) ” is acquired as“ differential value dVoxs / dt ”.
- the CPU When the differential value dVoxs / dt before the predetermined time Tb is equal to or greater than “0” and the newly obtained differential value dVoxs / dt is smaller than “0”, the CPU outputs the output value Voxs before the predetermined time Tb. Is obtained as the maximum value Vmax. Similarly, when the differential value dVoxs / dt before the predetermined time Tb is equal to or smaller than “0” and the newly obtained differential value dVoxs / dt is larger than “0”, the CPU outputs the output value before the predetermined time Tb. Voxs is acquired as a minimum value Vmin.
- Step 1100, Step 1110, Step 1140, and Step 1150 (actually Step 1200, Step 1202, Step 1212, and Step 1214) in FIG. 11 until the maximum value Vmax is acquired. .
- the CPU determines “Yes” in step 1214 and proceeds to step 1216, and the acquired maximum value Read Vmax. Next, the CPU determines (sets) the target value VREF according to the rules for “rich determination” shown in Table 1 above.
- the CPU proceeds to step 1218 to determine whether or not the maximum value Vmax is greater than or equal to the reference value Vf. If the maximum value Vmax is greater than or equal to the reference value Vf, the CPU proceeds to step 1220 to determine whether or not a value (Vmax ⁇ A1) obtained by subtracting “the value A1 as the first threshold value” from the maximum value Vmax is greater than the reference value Vf. Determine whether. When the value (Vmax ⁇ A1) is larger than the reference value Vf, the CPU proceeds to step 1222 to set a value (Vmax ⁇ A1) obtained by subtracting “value A1 as the first change value” from the maximum value Vmax as the target value. Set to VREF.
- step 1226 the CPU proceeds to step 1226 to set the reference value Vf to the target value VREF. Furthermore, if the maximum value Vmax is smaller than the reference value Vf at the time when the CPU executes the processing of step 1218, the CPU proceeds to step 1228 and subtracts “value B2 as the second change value” from the maximum value Vmax. The value (Vmax ⁇ B2) is set to the target value VREF.
- the CPU executes processing of any one of steps 1222, 1226, and 1228, and then proceeds to step 1224 to set the value of the target value determination request flag XVREFreq to “0”. Thereafter, the CPU proceeds to step 1195 via step 1295 and step 1150 in FIG. 11, and once ends the target value determination routine.
- step 1110 the CPU makes a “Yes” determination at step 1110 to proceed to step 1140.
- the target value determination request flag XVREFreq is set to “0” by the “process of step 1224 in FIG. 12” executed previously. Therefore, the CPU makes a “No” determination at step 1140 to proceed to step 1160 to perform air-fuel ratio determination (and air-fuel ratio request determination).
- step 1160 the CPU proceeds to step 1310 via step 1300 in FIG. 13 and determines whether or not the value of the rich determination flag XR is “1”.
- the CPU makes a “Yes” determination at step 1310 to proceed to step 1320 to determine whether or not the output value Voxs of the downstream air-fuel ratio sensor is smaller than the target value VREF. If the output value Voxs of the downstream air-fuel ratio sensor is smaller than the target value VREF, the CPU determines “Yes” in step 1320 (ie, determines that the air-fuel ratio is lean), and the steps described below The processes of 1330 and step 1340 are sequentially performed.
- Step 1330 The CPU sets the value of the rich determination flag XR to “0”.
- Step 1340 The CPU sets the value of the target value determination request flag XVREFreq to “1”. Thereafter, the CPU proceeds to step 1195 via step 1395 and step 1160 of FIG. 11 to end the target value determination routine once.
- step 1320 determines whether the output value Voxs of the downstream air-fuel ratio sensor is greater than or equal to the target value VREF at the time when the CPU executes the process of step 1320. If the output value Voxs of the downstream air-fuel ratio sensor is greater than or equal to the target value VREF at the time when the CPU executes the process of step 1320, the CPU makes a “No” determination at step 1320 to perform step 1395. Proceed directly to. Thereafter, the CPU proceeds to step 1195 via step 1160 in FIG. 11 to end the target value determination routine once.
- the value of the rich determination flag XR is “1”
- the value of the rich determination flag XR is changed to “0” only when the output value Voxs becomes smaller than the target value VREF.
- step 1140 of FIG. the CPU makes a “Yes” determination at step 1140 to proceed to step 1150. Accordingly, the CPU proceeds to step 1202 via step 1200 in FIG. 12, and determines whether or not the value of the target value convergence control execution flag XVSFB is “0”. In this case, the value of the target value convergence control execution flag XVSFB is “1” (see step 1210).
- step 1202 the value of the rich determination flag XR is set to “0” by the processing of step 1330 of FIG. Therefore, the CPU makes a “No” determination at step 1212 to proceed to step 1230 to determine whether or not the “minimum value Vmin of the output value Voxs” has been acquired since the rich determination flag XR was changed to “0”. judge. As described above, the minimum value Vmin is acquired separately by a routine (not shown).
- Step 1230 If the minimum value Vmin has not been acquired, the CPU makes a “No” determination at step 1230 to proceed directly to step 1195 via step 1295. Therefore, the CPU repeatedly executes Step 1100, Step 1110, Step 1140, and Step 1150 (actually Step 1200, Step 1202, Step 1212, and Step 1230) in FIG. 11 until the minimum value Vmin is acquired. .
- the CPU determines “Yes” in step 1230 and proceeds to step 1232, and the acquired minimum value Read Vmin. Next, the CPU determines (sets) the target value VREF in accordance with the “lean determination” rule shown in Table 1 above.
- the CPU proceeds to step 1234 to determine whether or not the minimum value Vmin is equal to or less than the reference value Vf. If the minimum value Vmin is less than or equal to the reference value Vf, the CPU proceeds to step 1236 to determine whether or not a value (Vmin + A2) obtained by adding “the value A2 as the first threshold value” to the minimum value Vmin is smaller than the reference value Vf. judge. If the value (Vmin + A2) is smaller than the reference value Vf, the CPU proceeds to step 1238 to set a value (Vmin + A2) obtained by adding the “value A2 as the first change value” to the minimum value Vmin as the target value VREF. .
- step 1242 if the value (Vmin + A2) is greater than or equal to the reference value Vf, the CPU proceeds to step 1242 to set the reference value Vf to the target value VREF. Furthermore, if the minimum value Vmin is larger than the reference value Vf at the time when the CPU executes the process of step 1234, the CPU proceeds to step 1244 to add “value B1 as the second change value” to the minimum value Vmin. The value (Vmin + B1) is set to the target value VREF.
- the CPU executes processing of any one of step 1238, step 1242, and step 1244, and then proceeds to step 1240 to set the value of the target value determination request flag XVREFreq to “0”. Thereafter, the CPU proceeds to step 1195 via step 1295 and step 1150 in FIG. 11, and once ends the target value determination routine.
- step 1110 the CPU makes a “Yes” determination at step 1110 to proceed to step 1140.
- the target value determination request flag XVREFreq is set to “0” by the “process of step 1240 of FIG. 12” executed previously. Accordingly, the CPU makes a “No” determination at step 1140 to proceed to step 1160 to perform air-fuel ratio determination.
- step 1160 the CPU proceeds to step 1310 via step 1300 in FIG. 13 and determines whether or not the value of the rich determination flag XR is “1”.
- the CPU makes a “No” determination at step 1310 to proceed to step 1350 to determine whether or not the output value Voxs of the downstream air-fuel ratio sensor is greater than the target value VREF. If the output value Voxs of the downstream air-fuel ratio sensor is larger than the target value VREF, the CPU determines “Yes” in step 1350 (ie, determines that the air-fuel ratio is rich), and the steps described below The processes of 1360 and step 1370 are sequentially performed.
- Step 1360 The CPU sets the value of the rich determination flag XR to “1”.
- Step 1370 The CPU sets the value of the target value determination request flag XVREFreq to “1”. Thereafter, the CPU proceeds to step 1195 via step 1395 and step 1160 of FIG. 11 to end the target value determination routine once.
- step 1350 the CPU makes a “No” determination at step 1350 to step 1395. Proceed directly. Thereafter, the CPU proceeds to step 1195 via step 1160 in FIG. 11 to end the target value determination routine once.
- the value of the rich determination flag XR is “0”
- the value of the rich determination flag XR is changed to “1” only when the output value Voxs becomes larger than the target value VREF.
- step 1140 the CPU makes a “Yes” determination at step 1140 to proceed to step 1150. Accordingly, the CPU proceeds to step 1202, step 1212 and step 1214 via step 1200 in FIG. Thereafter, similar processing is repeatedly performed.
- the target value convergence control execution flag XVSFB is changed from “0” to “1” in accordance with the establishment of the sub-feedback control condition (see step 1140 in FIG. 11).
- the CPU sets “minimum after the target value convergence control execution flag XVSFB is changed from“ 0 ”to“ 1 ”in step 1230. Whether or not the value Vmin has been acquired is monitored.
- the first control device executes target value convergence control for gradually bringing the target value VREF closer to the reference value Vf.
- the first control device determines whether a lean request is generated or a rich request is generated based on the output value Voxs of the downstream air-fuel ratio sensor and the target value VREF.
- Fuel ratio control means determination means
- the lean request is a request for increasing the air-fuel ratio of the engine in order to bring the output value Voxs closer to the target value VREF.
- the rich request is a request for reducing the air-fuel ratio of the engine so that the output value Voxs approaches the target value VREF.
- the lean request and the rich request are used to determine the target value VREF, but are not directly used to control the actual air / fuel ratio of the engine.
- the air-fuel ratio of the engine is controlled by a sub-feedback amount Vafsfb calculated so that the output value Voxs and the target value VREF are matched.
- the sub feedback amount Vafsfb increases the air / fuel ratio of the engine during the period in which the lean request is generated (that is, the period in which the output value Voxs is larger than the target value VREF) (indicated fuel injection amount). (Fi is decreased).
- the sub-feedback amount Vafsfb decreases the air-fuel ratio of the engine (indicated fuel injection amount) during the period when the rich request is occurring (that is, the period during which the output value Voxs is smaller than the target value VREF). Fi is increased).
- the first control device executes feedback control in which the air-fuel ratio of the engine is increased during the period in which the lean request is generated, and the air-fuel ratio in the engine is decreased in the period in which the rich request is generated.
- Air-fuel ratio control means see the routine of FIG. 10, etc.).
- the first control device includes extreme value acquisition means for acquiring the maximum value Vmax and the minimum value Vmin (see step 1214, step 1216, step 1230, and step 1232 in FIG. 12).
- the maximum value Vmax that is equal to or greater than the reference value Vf and the minimum value Vmin that is equal to or less than the reference value Vf are “approaching the reference value Vf from a state in which the output value Voxs of the downstream air-fuel ratio sensor changes in a direction away from the reference value Vf. It can be said that this is the output value Voxs when the state changes to the direction.
- Such extreme values a maximum value Vmax that is equal to or greater than the reference value Vf and a minimum value Vmin that is equal to or less than the reference value Vf
- first extreme values are referred to as “first extreme values” for convenience.
- the maximum value Vmax that is smaller than the reference value Vf and the minimum value Vmin that is larger than the reference value Vf are “separated from the reference value Vf from a state in which the output value Voxs of the downstream air-fuel ratio sensor changes in a direction approaching the reference value Vf. It can be said that this is the output value Voxs when the state changes to the direction.
- Such extreme values maximum value Vmax smaller than reference value Vf and minimal value Vmin larger than reference value Vf
- second extreme value are referred to as “second extreme value” for convenience.
- the first control device includes extreme value acquisition means for acquiring the first extreme value and the second extreme value.
- the air-fuel ratio control means of the first control device is: When the first extreme value (a maximum value Vmax that is equal to or greater than the reference value Vf or a minimum value Vmin that is equal to or less than the reference value Vf) is acquired by the extreme value acquisition unit, the acquired first extreme value and the reference A first value (Vmax ⁇ A1 or Vmin + A2) that is between the values Vf is set as the target value VREF (Table 1, (A) in FIG. 4, (C) in FIG. 4, ( A), (C) of FIG. 5, Step 1222, FIG. 1238 of FIG. 12, etc.).
- the target value VREF Table 1, (A) in FIG. 4, (C) in FIG. 4, ( A), (C) of FIG. 5, Step 1222, FIG. 1238 of FIG. 12, etc.
- the air-fuel ratio control means of the first control device sets the output value Voxs to “first value (Vmax) when a lean request is generated.
- first value Vmax
- the air-fuel ratio control means of the first control device sets the output value Voxs to “first value (Vmax) when a lean request is generated.
- the absolute value of the difference between the output value Voxs and the reference value Vf is smaller than the absolute value of the difference between the “target value VREF set to the first value (Vmax ⁇ A1)” and the reference value Vf. This is the point.
- the point in time when the absolute value of the difference between the output value Voxs and the reference value Vf becomes smaller than the absolute value of the difference between the “target value VREF set to the first value” and the reference value Vf is the first for convenience. Also called time.
- the air-fuel ratio control means of the first control device at the time when the output value Voxs becomes larger than the “target value VREF set to the first value (Vmin + A2)” when the rich request is generated. It is determined that a lean request has occurred (see step 1310, step 1350, and step 1360 in FIG. 13). At this time, the absolute value of the difference between the output value Voxs and the reference value Vf is smaller than the absolute value of the difference between the “target value VREF set to the first value (Vmin + A2)” and the reference value Vf. It is a time point (that is, a first time point).
- the air-fuel ratio control means of the first control device is configured such that “the absolute value of the difference between the output value Voxs and the reference value Vf” is “the target value VREF set to the first value and the reference value Vf”. “The other request”, which is different from the “one of the rich request and the lean request” that has been determined to have occurred up to the first time point at the first time point that is smaller than the “absolute value of the difference” Is determined to have occurred.
- the air-fuel ratio control means of the first control device is: Thereafter (after it is determined that “the other request” has occurred), the second extreme value (the minimum value Vmin larger than the reference value Vf and the maximum value Vmax smaller than the reference value Vf) is obtained by the extreme value acquisition unit. Is acquired, “the acquired second extreme value” and “the first extreme value acquired by the extreme value acquisition means (the maximum value Vmax larger than the reference value Vf or the reference value Vf”). A second value (Vmin + B1 or Vmax ⁇ B2) that is a value between “small minimum value Vmin)” is set as the target value VREF (Table 1, FIG. 4C, FIG. 5C), 12 step 1228, step 1244, etc.). In other words, the air-fuel ratio control means of the first control device sets the value B1 and the value B1 so that the second value is a value between the latest first extreme value and the latest second extreme value. ing.
- the air-fuel ratio control means of the first control device sets the output value Voxs to “the second value (Vmin + B1) when the rich request is generated. It is determined that a lean request has occurred when the target value VREF is greater than the target value VREF (see Step 1310, Step 1350, and Step 1360 in FIG. 13). At this time, the absolute value of the difference between the output value Voxs and the reference value Vf is larger than the absolute value of the difference between the “target value VREF set to the second value (Vmin + B1)” and the reference value Vf. It is time. When the absolute value of the difference between the output value Voxs and the reference value Vf becomes larger than the absolute value of the difference between the “target value VREF set to the second value” and the reference value Vf, for convenience, Also called time.
- the air-fuel ratio control means of the first control device detects when the output value Voxs becomes smaller than the “target value VREF set to the second value (Vmax ⁇ B2)” when the lean request is generated. It is determined that a rich request has occurred (see step 1310 to step 1330 in FIG. 13). At this time, the absolute value of the difference between the output value Voxs and the reference value Vf is larger than the absolute value of the difference between the “target value VREF set to the second value (Vmax ⁇ B2)” and the reference value Vf. This is the point in time (ie, the second point).
- the air-fuel ratio control means of the first control device is configured such that “the absolute value of the difference between the output value Voxs and the reference value Vf” is “the target value VREF set to the second value and the reference value Vf”. “The other request”, which is different from “Any one of the rich request and the lean request” that has been determined to have occurred up to the second time point at the second time point that is greater than the “absolute value of the difference” Is determined to have occurred.
- the first control device brings the target value VREF closer to the reference value Vf by repeating such setting of the target value VREF and determination of the air-fuel ratio (determination of whether a rich request or a lean request is occurring). That is, the first control device determines that the maximum value Vmax of the output value Voxs of the downstream side air-fuel ratio sensor is larger than “a value obtained by adding the first threshold value (A1) to the reference value Vf” or the downstream side air-fuel ratio sensor.
- the target value VREF target value used for sub-feedback control
- the target value VREF executes target value convergence control.
- the first control device changes the air-fuel ratio of the engine earlier than the conventional device in which the target value VREF is fixed to the reference value Vf (in other words, in a short cycle) from “lean air-fuel ratio to rich air-fuel ratio. To “or vice versa”.
- the first control device can bring the output value Voxs closer to the reference value Vf while avoiding an increase in the amplitude of the output value Voxs, so that the emission can be maintained well.
- the second change value (value B1 or value B2) is set to be smaller than “(sufficiently large) positive predetermined value” or more than the first change value (value A1 or value A2).
- the first control device sets a value that is the second value (for example, Vmin + B1) between the acquired second extreme value (Vmin) and the first value (Vmax ⁇ A1). Can be set to a value.
- the first control device sets the second value (for example, Vmax ⁇ B2) to a value between the acquired second extreme value (Vmax) and the first value (Vmin + A2). Can be set.
- the first control device can quickly converge the target value VREF to the reference value Vf.
- the first control device obtains after the “second extreme value acquisition time point when the minimum value Vmin (1) as the second extreme value is obtained”.
- the value A1 and the value B1 are set so that the obtained first extreme value (that is, the maximum value Vmax (2)) is smaller than the maximum value Vmax (1) obtained before the second extreme value acquisition time. It is desirable (see FIG. 6).
- the first control device starts the “second extreme value acquisition time when the maximum value Vmax (1) as the second extreme value is obtained” and thereafter.
- the values A2 and B2 are set so that the obtained first extreme value (that is, the minimum value Vmin (2)) is larger than the minimum value Vmin (1) obtained before the second extreme value acquisition time point. It is desirable to do so (see FIG. 7).
- the air-fuel ratio control means of the first control device reads “the first extreme value (for example, local maximum) acquired by the extreme value acquisition means after the second extreme value acquisition time (for example, time t3 in FIG. 6).
- Value Vmax (2)) and the reference value Vf is an absolute value (
- ) is smaller than the first value.
- it is preferable that the first value (Vmax (1) ⁇ A1) and the second value (Vmin (1) + B1) are set.
- the air-fuel ratio control means of the first control device may read: “The first extreme value (for example, the minimum value) acquired by the extreme value acquisition means after the second extreme value acquisition time (for example, time t3 in FIG. 7) Value Vmin (2)) ”and the reference value Vf is an absolute value (
- the target value VREF can be more reliably converged to the reference value Vf.
- the determination device of the first control device is When the first extreme value is acquired by the extreme value acquisition means, (1) When the absolute value of the difference between the acquired first extreme value and the reference value is larger than the positive first threshold value (value A1 or value A2) (“Yes” in step 1220 in FIG. 12) Or the determination of “Yes” in step 1236), the first value is set as the target value VREF (step 1222 or step 1238), (2) When the absolute value of the difference between the acquired first extreme value and the reference value is less than or equal to the first threshold value (determination of “No” in step 1220 of FIG. 12 or “ Reference value Vf is set as the target value VREF (step 1226 or step 1242).
- the determination device of the first control device determines that the output value Voxs has been generated up to the third time point at the third time point when the output value Voxs crosses the “target value VREF set to the reference value Vf”. It is determined that the “other request” that is different from the “one of the rich request and the lean request” has occurred (routine in FIG. 13, after time t8 in FIG. 6, and time in FIG. 7). (Refer to t8 and later etc.).
- the air-fuel ratio control means of the first control device is A value (Vmax (1) ⁇ A1) that is closer to the reference value by a positive first change value (value A1) than the first extreme value (for example, the maximum value Vmax (1)) is set as the first value. Then, a value (Vmin (1) + B1) far from the reference value Vf by the positive second change value (value B1) compared to the second extreme value (minimum value Vmin (1)) is set as the second value.
- the first change value (value A1) may be equal to or less than the first threshold value (value A1), and the second change value (value B1) is more than the first change value (value A1). Small is desirable.
- the air-fuel ratio control means of the first control device is A value (Vmin (1) + A2) that is closer to the reference value by a positive first change value (value A2) than the first extreme value (for example, the minimum value Vmin (1)) is set as the first value.
- a value (Vmax (1) ⁇ B2) far from the reference value Vf by the positive second change value (value B2) compared to the second extreme value (maximum value Vmax (1)) is set as the second value.
- the first change value (value A2) may be equal to or less than the first threshold value (value A2), and the second change value (value B2) is more than the first change value (value A2). Small is desirable.
- the second control device sets the first change value (value A1 and value A2) and the second change value (value B1 and value B2) to be “smaller as the temperature (element temperature) of the downstream air-fuel ratio sensor 56 is lower. Only in that it is different from the first control device.
- the output value Voxs of the downstream air-fuel ratio sensor increases as the temperature of the downstream air-fuel ratio sensor 56 decreases.
- the minimum value approaches the minimum output value Min.
- the output value Voxs of the downstream air-fuel ratio sensor changes more rapidly as the temperature Tear of the downstream air-fuel ratio sensor 56 is lower.
- the CPU of the second control device executes the routine shown in FIG. 14 every time a predetermined time elapses. Accordingly, when the predetermined timing comes, the CPU starts processing from step 1400 in FIG. 14 and proceeds to step 1410 to acquire the temperature Tear of the downstream side air-fuel ratio sensor 56. Specifically, the CPU acquires the impedance (or admittance) of the downstream air-fuel ratio sensor 56, and acquires the temperature Tear based on the impedance. The CPU may obtain the temperature Tear by estimating the temperature of the exhaust gas from the load KL and the engine rotational speed NE, and performing a first-order lag process or the like on the estimated temperature of the exhaust gas.
- step 1420 the CPU proceeds to step 1420, and applies the acquired temperature Tree to the table MapAB (Trea) shown in step 1420, whereby the first change value (value A1 and value A2) and the second change value are applied.
- the values (value B1 and value B2) are determined.
- the first change value and the second change value are determined to be smaller as the temperature Tear is lower.
- the value A1 and the value A2 are equal, but the value A1 and the value A2 may be different.
- the value B1 and the value B2 are equal, but the value B1 and the value B2 may be different.
- the CPU proceeds to step 1495 to end the present routine tentatively.
- the CPU sets the target value VREF using the “first change value and second change value” thus determined (see the routine of FIG. 12).
- the output value Voxs of the downstream air-fuel ratio sensor changes more rapidly as the temperature Tear of the downstream air-fuel ratio sensor 56 is lower (the output when the air-fuel ratio of the catalyst outflow gas has passed the stoichiometric air-fuel ratio stoich).
- the fluctuation range of the value Voxs becomes large). Therefore, the second control device “decreases” the first change value and the second change value as the temperature Tear is lower. Thereby, it can be determined that a rich request has occurred before the output value Voxs becomes excessively small, and it can be determined that a lean request has occurred before the output value Voxs becomes excessively large.
- the output value Voxs can be maintained in the vicinity of the “target value VREF approaching the reference value Vf with time” while maintaining the amplitude of the output value Voxs small. Therefore, the second control device can maintain the emission satisfactorily regardless of the temperature Tear.
- the second control device may change only the value A1 and the value A2 according to the temperature Tear, and may maintain the value B1 and the value B2 at constant values. Further, the second control device may set at least one of the value A1, the value A2, the value B1, and the value B2 to a “smaller value” as the temperature Tear is lower. In addition, the second control device may change the values (A1, A2) as the first threshold value according to the temperature Tear as well as the first change value, or may maintain the values at a constant value.
- the third control device uses the first change value (value A1 and value A2) and the second change value (value B1 and value B2) as the flow rate of the exhaust gas passing through the catalyst 43 (and hence the intake air amount Ga) decreases. It differs from the first control device only in that it is “smaller”.
- the “change width per unit time of the output value Voxs of the downstream air-fuel ratio sensor” when the air-fuel ratio of the catalyst outflow gas crosses the stoichiometric air-fuel ratio stoich is the flow rate of the exhaust gas passing through the catalyst 43. Is smaller than when the flow rate of the exhaust gas passing through the catalyst 43 is large. This is because when the exhaust gas flow rate is small, compared to when the exhaust gas flow rate is large, it is difficult for oxygen to flow out downstream of the catalyst 43 until the oxygen storage amount OSA reaches a value near the maximum oxygen storage amount Cmax. When the OSA reaches a value near the maximum oxygen storage amount Cmax, it is estimated that oxygen suddenly flows out downstream of the catalyst 43.
- the CPU of the third control device executes the routine shown in FIG. 15 every time a predetermined time elapses. Therefore, when the predetermined timing comes, the CPU starts processing from step 1500 in FIG. 15 and proceeds to step 1510 to acquire the intake air amount Ga.
- the intake air amount Ga represents the flow rate of exhaust gas passing through the catalyst 43.
- the CPU proceeds to step 1520, and applies the acquired intake air amount Ga to the table MapAB (Ga) shown in step 1520, whereby the first change value (value A1 and value A2), 2 change values (value B1 and value B2) are determined.
- the first change value and the second change value are determined so as to decrease as the intake air amount Ga decreases.
- the value A1 and the value A2 are equal, but the value A1 and the value A2 may be different.
- the value B1 and the value B2 are equal, but the value B1 and the value B2 may be different.
- the CPU proceeds to step 1595 to end the present routine tentatively.
- the CPU sets the target value VREF using the “first change value and second change value” thus determined (see the routine of FIG. 12).
- the third control device can maintain the emission satisfactorily regardless of the flow rate of the exhaust gas.
- the third control device may change only the value A1 and the value A2 according to the intake air amount Ga, and may maintain the value B1 and the value B2 at constant values. Further, the third control device may set at least one of the value A1, the value A2, the value B1, and the value B2 to a smaller value as the intake air amount Ga is smaller. In addition, the third control device may change the values (A1, A2) as the first threshold values according to the intake air amount Ga as well as the first change value, or may maintain them at a constant value. .
- the fourth control device increases the first change value (value A1 and value A2) as the first extreme value (the maximum value Vmax larger than the reference value Vf and the minimum value Vmin smaller than the reference value Vf) increases. It differs from the first control device only in that it is “smaller”.
- the CPU of the fourth control apparatus executes a routine shown in FIG. 16 instead of FIG. 12 in addition to the routines shown in FIGS. 8 to 11 and FIG. That is, when the CPU proceeds to step 1150 in FIG. 11, the CPU proceeds to step 1600 in FIG. Further, when the CPU proceeds to step 1695 in FIG. 16, the CPU proceeds to step 1195 via step 1150 in FIG.
- the routine shown in FIG. 16 differs from the routine shown in FIG. 12 only in that “steps 1610 to 1640” are added to the routine shown in FIG. Therefore, hereinafter, this difference will be mainly described.
- step 1220 the CPU proceeds to step 1610 to determine whether or not a value obtained by subtracting the value (A1 + a1) from the maximum value Vmax (Vmax ⁇ (A1 + a1)) is greater than the reference value Vf. judge.
- the value a1 is a positive predetermined value, and the value (A1 + a1) is smaller than the absolute value of the difference between the maximum output value Max and the reference value Vf.
- step 1610 If the value (Vmax ⁇ (A1 + a1)) is larger than the reference value Vf, the CPU proceeds from step 1610 to step 1620, and sets the value (Vmax ⁇ A1s) as the target value VREF.
- the value A1s is a predetermined positive value that is smaller than the value A1. Thereafter, the CPU proceeds to step 1224.
- the CPU proceeds from step 1610 to step 1222, and sets the value (Vmax ⁇ A1) to the target value VREF. Thereafter, the CPU proceeds to step 1224.
- the CPU sets the target value VREF to the value (Vmax ⁇ A1s) when the absolute value of the difference between the maximum value Vmax and the reference value Vf is larger than the value (A1 + a1), and sets the maximum value Vmax and the reference value Vf.
- the target value VREF is set to the value (Vmax ⁇ A1) when the absolute value of the difference between the values is greater than the value A1 and equal to or less than the value (A1 + a1).
- the first value is set to a larger value than when the maximum value Vmax is smaller than the predetermined value (Vf + A1 + a1).
- step 1236 the CPU proceeds to step 1630 to determine whether or not a value obtained by adding the value (A2 + a2) to the minimum value Vmin (Vmim + (A2 + a2)) is smaller than the reference value Vf. Determine.
- the value a2 is a positive predetermined value, and the value (A2 + a2) is smaller than the absolute value of the difference between the minimum output value Min and the reference value Vf.
- step 1630 If the value (Vmim + (A2 + a2)) is smaller than the reference value Vf, the CPU proceeds from step 1630 to step 1640 and sets the value (Vmin + A2s) to the target value VREF.
- the value A2s is a positive predetermined value that is smaller than the value A2. Thereafter, the CPU proceeds to step 1240.
- the CPU proceeds from step 1630 to step 1238, and sets the value (Vmin + A2) to the target value VREF. Thereafter, the CPU proceeds to step 1240.
- the CPU sets the target value VREF to the value (Vmin + A2s) when the absolute value of the difference between the minimum value Vmin and the reference value Vf is larger than the value (A2 + a2), and the difference between the minimum value Vmin and the reference value Vf. Is larger than the value A2 and not more than the value (A2 + a2), the target value VREF is set to the value (Vmin + A2).
- the first value is set to a smaller value than when the minimum value Vmin is larger than the predetermined value (Vf ⁇ (A2 + a2)).
- the catalyst outflow gas contains a large amount of oxygen. Therefore, the output value Voxs of the downstream air-fuel ratio sensor shows a value very close to the minimum output value Min.
- the output value Voxs of the downstream air-fuel ratio sensor does not increase immediately. That is, the change in the output value Voxs with respect to the change in the air-fuel ratio of the catalyst outflow gas is delayed.
- the catalyst outflow gas contains a large amount of unburned substances.
- the output value Voxs of the downstream air-fuel ratio sensor is very close to the maximum output value Max.
- the air-fuel ratio of the catalyst outflow gas becomes the lean air-fuel ratio after the end of the increase control after the fuel cut ends. Even so, the output value Voxs of the downstream air-fuel ratio sensor does not immediately decrease. That is, the change in the output value Voxs with respect to the change in the air-fuel ratio of the catalyst outflow gas is delayed.
- the downstream air-fuel ratio sensor 56 when a large amount of oxygen or a large amount of unburned matter reaches the downstream air-fuel ratio sensor 56, the downstream air-fuel ratio sensor 56 is in a so-called “primary poisoning state”, and the responsiveness of the sensor decreases. .
- the fourth control device when the maximum value Vmax becomes extremely large (that is, when the absolute value of the difference between the maximum value Vmax and the reference value Vf is larger than the value (A1 + a1)), the target The value VREF is set to “a value closer to the maximum value Vmax (Vmax ⁇ A1s) ⁇ . Similarly, the fourth control device determines that the minimum value Vmin becomes extremely small (that is, the minimum value Vmin and the reference value Vf When the absolute value of the difference is larger than the value (A2 + a2)), the target value VREF is set to “a value closer to the minimum value Vmin (Vmin + A2s)”.
- the fourth control device can bring the output value Voxs closer to the reference value Vf while avoiding an increase in the amplitude of the output value Voxs, so that the emission can be maintained satisfactorily.
- the fourth control device The value of the first change value when the absolute value of the difference between the first extreme value (for example, the maximum value Vmax) and the reference value Vf is greater than a positive second threshold (A1 + a1) is the first extreme value. It is said that the device is configured to set a value (A1s) smaller than the value (A1) of the first change value when the absolute value of the difference between the reference value and the reference value is equal to or less than the second threshold value. be able to.
- the fourth control device The value of the first change value when the absolute value of the difference between the first extreme value (for example, the minimum value Vmin) and the reference value Vf is greater than the positive second threshold (A2 + a2) is the first extreme value. It is said that the apparatus is configured to set a value (A2s) smaller than the value (A2) of the first change value when the absolute value of the difference between the reference value and the reference value is equal to or less than the second threshold value. be able to.
- the fourth control device The value of the second change value when the absolute value of the difference between the first extreme value (for example, the maximum value Vmax) and the reference value Vf is larger than the positive second threshold (A1 + a1) is the first extreme value.
- the absolute value of the difference between the reference value and the reference value may be set to a value (B1s) smaller than the value (B1) of the second change value when the absolute value is equal to or less than the second threshold value.
- the fourth control device The value of the second change value when the absolute value of the difference between the first extreme value (for example, the minimum value Vmin) and the reference value Vf is larger than the positive second threshold (A2 + a2) is the first extreme value.
- the absolute value of the difference between the reference value and the reference value may be set to a value (B2s) smaller than the second change value (B2) when the absolute value is equal to or less than the second threshold value.
- the fourth control device may set at least one of the first change value A1 and the second change value B1 so as to continuously decrease as the maximum value Vmax larger than the reference value Vf increases. Good. Similarly, the fourth control device sets at least one of the first change value A2 and the second change value B2 so that it continuously decreases as the minimum value Vmin smaller than the reference value Vf decreases. Also good.
- the fifth control device sets the first change value (at least one of the value A1 and the value A2) for a period from when the fuel cut control ends until a predetermined time elapses (period after the fuel cut control ends), fuel cut control. It differs from the first control device only in that it is smaller than the period other than the period after the end.
- the CPU of the fifth control device is different from the CPU of the fourth control device only in that the routine shown in FIG. 17 instead of FIG. 16 is executed. Therefore, hereinafter, this difference will be mainly described.
- the routine shown in FIG. 17 differs from the routine shown in FIG. 16 only in that “steps 1610 and 1630” of the routine shown in FIG. 16 are replaced with “steps 1710 and 1720”, respectively.
- step 1710 the CPU determines whether or not the current time is within the period after the end of the fuel cut control. If the current time is within the period after the end of fuel cut control, the CPU proceeds from step 1710 to step 1620. If the current time is not within the period after the end of fuel cut control, the CPU proceeds from step 1710 to step 1222.
- step 1720 the CPU determines whether or not the current time is within the period after the end of the fuel cut control. If the current time is within the period after the end of the fuel cut control, the CPU proceeds from step 1720 to step 1640. If the current time is not within the period after the end of fuel cut control, the CPU proceeds from step 1720 to step 1238.
- the downstream air-fuel ratio sensor 56 is in the above-described primary poisoning state within the period after the end of the fuel cut control. Accordingly, as in the fifth control device, the first change value is decreased within the period after the end of the fuel cut control (the target value VREF is set to the value Vmax-A1s instead of the value Vmax-A1, or the value Vmin + A2 Instead of the value Vmin + A2s). That is, the fifth control device sets the “first change value within the period after the end of the fuel cut control” to a value smaller than the “first change value during the period other than the period during the end of the fuel cut control”.
- the fifth control device can bring the output value Voxs closer to the reference value Vf while avoiding an increase in the amplitude of the output value Voxs, so that the emission can be maintained well.
- the fifth control device may set “the second change value within the period after the end of the fuel cut control” to a value smaller than the “second change value during the period other than the end of the fuel cut control”.
- the “period after the end of fuel cut control” includes a control for setting the air / fuel ratio of the engine to a rich air / fuel ratio over a predetermined period after the end of the fuel cut control (an increase control after the end of the fuel cut) and an increase control after the end of the fuel cut.
- a period obtained by adding a period until a predetermined time elapses after the end of the process may be included.
- the fifth control device may replace step 1710 with “a step of determining whether or not the present time is within a period in which a predetermined time has elapsed after the end of the increase control after the fuel cut ends”. Furthermore, the fifth control apparatus may replace step 1720 with “a step of determining whether or not the present time is within a period in which a predetermined time has elapsed after the end of the fuel-cut increase control”. In addition, it is preferable that the fifth control device maintains the values (A1, A2) as the first threshold values at a constant value.
- the sixth control device sets the first change value (value A1 and value A2) as “more than when the engine is in a predetermined acceleration state and when the engine is not in a predetermined acceleration state (when it is in a steady state). It differs from the first control device only in that it is “small”.
- the CPU of the sixth control device is different from the CPU of the fourth control device only in that the routine shown in FIG. 18 instead of FIG. 16 is executed. Therefore, hereinafter, this difference will be mainly described.
- the routine shown in FIG. 18 differs from the routine shown in FIG. 16 only in that “steps 1610 and 1630” in the routine shown in FIG. 16 are replaced with steps 1810 and 1820, respectively.
- the CPU determines whether or not the current state of the engine 10 is in a predetermined acceleration state. More specifically, the CPU determines that the current time is “a period from when the change amount ⁇ TA of the throttle valve opening TA per unit time becomes equal to or greater than the transient determination threshold ⁇ TAth to the time when a predetermined time elapses (acceleration When the period is “within”, it is determined that the current state of the engine 10 is in a predetermined acceleration state.
- the parameters for determining whether or not the vehicle is in an acceleration state include the change amount ⁇ TA per unit time of the throttle valve TA, the change amount ⁇ Accp per unit time of the accelerator pedal operation Accp, and the unit time of the intake air amount Ga. Or a change amount ⁇ KL of the load KL per unit time, a change amount ⁇ SPD of the speed of the vehicle equipped with the engine 10 per unit time, or the like.
- step 1810 the CPU proceeds from step 1810 to step 1620. If the current time is not within the acceleration period, the CPU proceeds from step 1810 to step 1222.
- step 1820 the CPU determines whether or not the current time is within the acceleration period. If the current time is within the acceleration period, the CPU proceeds from step 1820 to step 1640. If the current time is not within the acceleration period, the CPU proceeds from step 1820 to step 1238.
- the oxygen storage amount OSA of the catalyst 43 is likely to reach “a value close to the maximum oxygen storage amount Cmax or a value close to“ 0 ””, and in that state, a large amount of “NOx or unburned” There is a high possibility that the “thing” will flow into the catalyst 43.
- the sixth control device decreases the first change value within the acceleration period (target value VREF is set to value Vmax-A1s instead of value Vmax-A1 or set to value Vmin + A2s instead of value Vmin + A2. To do). That is, the sixth control device sets “the first change value within the acceleration period” to a value smaller than “the first change value during the period other than the acceleration period”.
- the lean request or rich request can be determined more quickly.
- the air-fuel ratio of the engine can be switched without delay from “lean air-fuel ratio to rich air-fuel ratio or vice versa”. Therefore, the sixth control device can maintain the emission satisfactorily.
- the sixth control device may set the “second change value in the acceleration period” to a value smaller than the “second change value in a period other than the acceleration period”.
- a control device according to a seventh embodiment of the present invention (hereinafter simply referred to as “seventh control device”) will be described.
- the seventh control device is different from the first control device only in that the learning condition for the main FB learning value KG is different from the learning condition for the first control device. Therefore, hereinafter, this difference will be mainly described.
- the CPU of the seventh control device executes the routines shown in FIGS. 8 to 13 like the CPU of the first control device. However, the CPU of the seventh control device determines that the learning condition is satisfied when all of the following conditions are satisfied in step 955 of FIG. 9.
- Condition 1 A time that is a natural number times the time interval (predetermined time ta) at which the routine of FIG. 9 is executed has elapsed.
- Condition 2 The state in which the target value VREF matches the reference value Vf has elapsed for a predetermined time t or longer.
- the seventh control device executes “learning control to update the main FB learning value KG” when the target value VREF is set to the reference value Vf, and the target value VREF is set to the reference value Vf. If not, the learning control is not executed (prohibited).
- the seventh control device updates the main FB learning value KG only when the target value VREF matches the reference value Vf (executes learning control). Therefore, the possibility that the main FB learning value KG becomes an incorrect value can be reduced. As a result, the seventh control apparatus can maintain the emission satisfactorily.
- the seventh control device updates the correction coefficient average value FAFAV in step 950 of FIG. 9 only when the state in which the target value VREF matches the reference value Vf has elapsed for a predetermined time t or longer.
- it is configured.
- the seventh control device and the control device are: An intake air amount (in-cylinder intake air amount Mc (k)) sucked into the engine 10 is acquired (step 830 in FIG. 8), and the acquired intake air amount (in-cylinder intake air amount Mc (k)) A basic fuel injection amount Fb for making the air-fuel ratio of the “air mixture supplied to the engine 10” coincide with the stoichiometric air-fuel ratio (step 840 in FIG.
- An upstream air-fuel ratio sensor 55 that is disposed upstream of the catalyst 43 in the exhaust passage and outputs an output value corresponding to the air-fuel ratio of the exhaust gas flowing into the catalyst 43;
- Calculation means steps 905 to 945 in FIG. 9);
- the basic fuel injection amount is corrected so as to increase the basic fuel injection amount in a period in which it is determined that the lean request is generated, and in the period in which it is determined that the rich request is generated.
- Sub feedback amount calculating means for calculating a sub feedback amount (Vafsfb) for correcting the basic fuel injection amount so as to decrease the basic fuel injection amount;
- the basic fuel injection amount Fb is corrected by an air-fuel ratio correction amount (FAF) based on the main feedback amount and the sub feedback amount to calculate the indicated fuel injection amount Fi (step 910 in FIG. 9 and step 850 in FIG. 8).
- FAF air-fuel ratio correction amount
- the feedback control is executed by supplying the calculated fuel injection amount Fi to the engine 10 (step 860 in FIG. 8) fuel injection amount control means, Is an air-fuel ratio control device.
- the air-fuel ratio control means of the seventh control device is Learning control for acquiring a value correlated with the average value of the main feedback amount (for example, FAFAV or a value that increases when FAFAV is large and decreases when FAFAV is small) as an air-fuel ratio learning value (main FB learning value KG).
- Learning means steps 950 to 975 in FIG. 9 to be executed,
- the fuel injection amount control means includes The command fuel injection amount is calculated by correcting the basic fuel injection amount Fb based on the air-fuel ratio learning value KG (step 850 in FIG.
- the learning means of the seventh control device comprises: The learning control is executed when the target value is set to the reference value, and the learning control is not executed when the target value is not set to the reference value ( (See step 955 in FIG. 9 and (Condition 2) described above.)
- the eighth control device is configured to correct the air-fuel ratio learning value (main FB learning value KG) based on a value correlated with the target value VREF when the target value VREF does not converge to the reference value Vf. Only the seventh control device is different. Therefore, hereinafter, this difference will be mainly described.
- the CPU of the eighth control device executes the same routine as the CPU of the seventh control device. Further, the CPU of the eighth control device executes the routine shown in FIG. 19 every time a predetermined time elapses.
- the CPU starts the process from step 1900 in FIG. 19 and proceeds to step 1910 to determine whether or not the main feedback control condition is satisfied. At this time, if the main feedback control condition is not satisfied, the CPU proceeds directly from step 1910 to step 1995 to end the present routine tentatively.
- the CPU makes a “Yes” determination at step 1910 to proceed to step 1920, where “the target value VREF is the first value. It is determined whether or not a state that matches the reference value Vf for one or more durations (hereinafter also referred to as “target value convergence state”) has not occurred for the second duration t href or more. To do.
- the CPU makes a “No” determination at step 1920 to Proceeding directly to 1995, this routine is temporarily terminated.
- the CPU makes a “Yes” determination at step 1920 to proceed to step 1930, where the target value VREF is It is determined whether or not the value (Vmax ⁇ A1) and the value (Vmin + A2) are alternately changed.
- the CPU makes a “Yes” determination at step 1930 to proceed directly to step 1995.
- the routine is temporarily terminated.
- the CPU makes a “No” determination at step 1930 to proceed to step 1940, where the average of the target value VREF It is determined whether or not a value (an average value of the target value VREF from a predetermined point in the past to a current value, a value correlated with the average value of the target value VREF) is larger than the reference value Vf.
- the CPU makes a “Yes” determination at step 1940 to proceed to step 1950 to decrease the main FB learning value KG by a positive predetermined value dKG1. That is, the main FB learning value KG is corrected to “a value that further reduces the basic fuel injection amount Fb” compared to the main FB learning value KG at that time. Thereafter, the CPU proceeds to step 1995 to end the present routine tentatively.
- step 1940 If the average value of the target value VREF is smaller than the reference value Vf when the CPU executes the process of step 1940, the CPU makes a “No” determination at step 1940 to proceed to step 1960, where the main FB learning value KG Is increased by a positive predetermined value dKG2. That is, the main FB learning value KG is corrected to “a value that increases the basic fuel injection amount Fb” as compared with the main FB learning value KG at that time. Thereafter, the CPU proceeds to step 1995 to end the present routine tentatively.
- the center of the air-fuel ratio of the engine is the theoretical sky. It becomes smaller than the fuel ratio stoich. Therefore, the average air-fuel ratio of the catalyst outflow gas also becomes a rich air-fuel ratio.
- the output value Voxs of the downstream air-fuel ratio sensor oscillates around a value larger than the reference value Vf as shown in FIG. That is, the maximum value Vmax continues to be a value near the maximum output value Max.
- the target value VREF alternately changes to a value (Vmax ⁇ A1) that is the lean determination target value VREFL and a value Vf that is the rich determination target value VREFR.
- the target value VREF does not converge to the reference value Vf, and the “target value convergence state” does not occur over the second duration t href.
- the eighth control device decreases the main FB learning value KG by a positive predetermined value dKG1 as described above.
- the center of the air-fuel ratio of the engine can be brought close to the stoichiometric air-fuel ratio stoich, and the target value VREF can be converged to the reference value Vf.
- the center of the air-fuel ratio of the engine is theoretically It becomes larger than the air-fuel ratio stoich. Therefore, the average of the air-fuel ratio of the catalyst outflow gas is also the lean air-fuel ratio.
- the output value Voxs of the downstream air-fuel ratio sensor oscillates around a value smaller than the reference value Vf as shown in FIG. That is, the minimum value Vmin continues to be a value near the minimum output value Min.
- the target value VREF alternately changes to a value (Vmin + A2) that is the rich determination target value VREFR and a value Vf that is the lean determination target value VREFL.
- the target value VREF does not converge to the reference value Vf, and the “target value convergence state” does not occur over the second duration t href.
- the eighth control device increases the main FB learning value KG by a positive predetermined value dKG2 as described above.
- the center of the air-fuel ratio of the engine can be brought close to the stoichiometric air-fuel ratio stoich, and the target value VREF can be converged to the reference value Vf.
- the eighth control device as shown in FIG. 22, the state in which the target value VREF is alternately changed to “value (Vmax ⁇ A1) and value (Vmin + A2)” is a predetermined time (third duration time). ) If the above continues, the main FB learning value KG is not corrected (see the determination of “No” in step 1930 in FIG. 19). That is, the eighth control device, when “the state in which the lean determination target value VREFL is the value (Vmax ⁇ A1) and the rich determination target value VREFR is the value (Vmin + A2)” continues for a predetermined time or longer ( Hereinafter, this case is also referred to as a “target value vibration state.”) The main FB learning value KG is not changed.
- the first duration is set to a time at which the number of times that the air-fuel ratio request has been changed (from the lean request to the rich request or vice versa) (the number of inversions) is equal to or greater than the first predetermined number of times. can do.
- the second duration time can be set to a time when the number of inversions is equal to or greater than the second predetermined number.
- the third duration can be set to a time when the number of inversions is equal to or greater than the third predetermined number.
- a control device according to a ninth embodiment of the present invention (hereinafter simply referred to as “ninth control device”) will be described.
- the ninth control device performs the first change compared to the case where the target value vibration state has not occurred. It differs from the eighth control device only in reducing the values (value A1 and value A2). Therefore, hereinafter, this difference will be mainly described.
- the CPU of the ninth control device executes the same routine as the CPU of the eighth control device. Further, the CPU of the ninth control device executes the routine shown in FIG. 23 every time a predetermined time elapses.
- the routine shown in FIG. 23 differs from the routine shown in FIG. 16 only in that “steps 1610 and 1630” of the routine shown in FIG. 16 are replaced with steps 2310 and 2320, respectively.
- step 2310 the CPU determines whether or not the current time is the above-described target value vibration state. If the current time is the target value vibration state, the CPU proceeds from step 2310 to step 1620. If the current time is not the target value vibration state, the CPU proceeds from step 2310 to step 1222.
- step 2320 the CPU determines whether or not the current time is the target value vibration state. If the current time is the target value vibration state, the CPU proceeds from step 2320 to step 1640. If the current time is not the target value vibration state, the CPU proceeds from step 2320 to step 1238.
- the ninth control device makes the first change value smaller when the target value vibration state is present than when the target value vibration state is not present (the target value VREF is changed to the value Vmax-A1s instead of the value Vmax-A1). Or set to the value Vmin + A2s instead of the value Vmin + A2.) That is, the ninth control device sets the “first change value when the target value is in the vibration state” to a value smaller than the “first change value when the target value is not in the vibration state”.
- the ninth control device can switch the air-fuel ratio of the engine at an earlier timing “from the lean air-fuel ratio to the rich air-fuel ratio or vice versa” when in the target value oscillation state.
- the ninth control apparatus can improve emissions when the target value vibration state occurs.
- the ninth control device may set the “second change value when the target value is in the vibration state” to a value smaller than the “second change value when the target value is not in the vibration state”.
- tenth control device a control device according to a tenth embodiment of the present invention (hereinafter simply referred to as “tenth control device”) will be described.
- the tenth control device is different from the first control device only in that the target value VREF is forced to approach the reference value Vf with time. Therefore, hereinafter, this difference will be mainly described.
- step 2410 determines whether or not the sub feedback control condition is satisfied. If the sub feedback control condition is not satisfied, the CPU makes a “No” determination at step 2410 to proceed to step 2420 to execute the process described below. Thereafter, the CPU proceeds to step 2495 to end the present routine tentatively.
- the CPU sets the value of the target value convergence control execution flag XVSFB to “0”.
- the target value convergence control execution flag XVSFB is set to “0” in the above-described initial routine.
- the CPU sets the value of the target value decrease flag XD to “0”.
- the CPU sets the value of the target value increase flag XU to “0”.
- the CPU sets the reference value Vf as the target value VREF.
- step 2410 the CPU makes a “Yes” determination at step 2410 to proceed to step 2430, where the target value convergence control execution flag XVSFB is executed. It is determined whether the value of “0” is “0”. If the value of the target value convergence control execution flag XVSFB is not “0”, the CPU makes a “No” determination at step 2430 to directly proceed to step 2495 to end the present routine tentatively.
- step 2430 If the value of the target value convergence control execution flag XVSFB is “0” at the time when the CPU executes the processing of step 2430, the CPU determines “Yes” in step 2430 and proceeds to step 2440 to perform sub feedback control. It is determined whether or not “maximum value Vmax has been acquired” during a period from when the condition is satisfied to the present time.
- the CPU makes a “Yes” determination at step 2440 to proceed to step 2450, where the maximum value Vmax and the reference value Vf are It is determined whether or not the absolute value of the difference is greater than a positive first threshold value (in this case, the value A1) (determines whether the maximum value Vmax is greater than the value (Vf + A1)).
- a positive first threshold value in this case, the value A1
- step 2450 the CPU makes a “Yes” determination at step 2450 to proceed to step 2460 to execute the processing described below. Thereafter, the routine proceeds to step 2495 to end the present routine tentatively.
- the CPU sets the value of the target value convergence control execution flag XVSFB to “1”.
- the CPU sets the value of the target value decrease flag XD to “1”.
- the CPU sets the value of the target value increase flag XU to “0”.
- the CPU stores the maximum value Vmax as the initial maximum value Vmax0.
- the absolute value of the difference between the maximum value Vmax and the reference value Vf is obtained when the maximum value Vmax is not acquired at the time when the CPU executes the process of step 2440 and when the CPU executes the process of step 2450. If it is equal to or less than the positive first threshold value A1, the CPU proceeds to step 2470.
- step 2470 the CPU determines “whether or not the minimum value Vmin has been acquired” during the period from when the sub-feedback control condition is satisfied to the present time.
- the CPU makes a “Yes” determination at step 2470 to proceed to step 2480 where the minimum value Vmin and the reference value Vf are It is determined whether or not the absolute value of the difference is greater than a positive first threshold value (in this case, the value A2) (determines whether the minimum value Vmin is smaller than the value (Vf ⁇ A2)). .
- a positive first threshold value in this case, the value A2
- step 2480 If the absolute value of the difference between the minimum value Vmin and the reference value Vf is greater than the positive first threshold value A2, the CPU makes a “Yes” determination at step 2480 to proceed to step 2490 to execute the processing described below. Thereafter, the routine proceeds to step 2495 to end the present routine tentatively.
- the CPU sets the value of the target value convergence control execution flag XVSFB to “1”.
- the CPU sets the value of the target value decrease flag XD to “0”.
- the CPU sets the value of the target value increase flag XU to “1”.
- the CPU stores the minimum value Vmin as the initial minimum value Vmin0.
- the absolute value of the difference between the minimum value Vmin and the reference value Vf is obtained when the minimum value Vmin is not acquired at the time when the CPU executes the process of step 2470 and when the CPU executes the process of step 2480. If it is equal to or smaller than the positive first threshold value A2, the CPU proceeds to step 2495 to end the present routine tentatively.
- the CPU is after the sub-feedback control condition is satisfied and the value of the target value convergence control execution flag XVSFB is “0” (that is, the target value convergence control is not executed).
- the value of the target value decrease flag XD is set to “1”.
- the CPU has a target value convergence control execution flag XVSFB value of “0” (that is, target value convergence control is not executed), and “ When the “absolute value of the difference between the minimum value Vmin and the reference value Vf” is larger than the first threshold value, the value of the target value increase flag XU is set to “1”.
- the CPU starts the process from step 2500 in FIG. 25 at a predetermined timing, and determines whether or not the value of the target value decrease flag XD is “1” in step 2510. At this time, if the value of the target value decrease flag XD is not “1”, the CPU makes a “No” determination at step 2510 to directly proceed to step 2595 to end the present routine tentatively.
- step 2510 the CPU makes a “Yes” determination at step 2510 to proceed to step 2520.
- step 2520 the CPU determines whether or not “current time is immediately after the value of the target value decrease flag XD has changed from“ 0 ”to“ 1 ””.
- the present time is immediately after the value of the target value decrease flag XD changes from “0” to “1”. Accordingly, the CPU makes a “Yes” determination at step 2520 to proceed to step 2530, sets the value of the counter N to “1”, and proceeds to step 2540. If the CPU does not execute the process of step 2520 immediately after the value of the target value decrease flag XD changes from “0” to “1”, the CPU makes a “No” determination at step 2520 to perform the step. Proceed directly to 2540.
- step 2540 the CPU determines whether the air-fuel ratio determination result is reversed. More specifically, when the output value Voxs of the downstream air-fuel ratio sensor is smaller than the target value VREF and the current output value Voxs is larger than the target value VREF before the predetermined time, the CPU determines the air-fuel ratio determination result. Is determined to be reversed. Further, when the output value Voxs of the downstream air-fuel ratio sensor is larger than the target value VREF and the current output value Voxs is smaller than the target value VREF before a predetermined time, the CPU determines that the air-fuel ratio determination result is reversed. To do.
- step 2540 the CPU makes a “Yes” determination at step 2540 to proceed to step 2550 to increase the value of the counter N by “1”, and then proceeds to step 2560.
- the CPU makes a “No” determination at step 2540 to directly proceed to step 2560.
- step 2560 the CPU subtracts “the product of the value N and the positive constant value ⁇ V1” from the initial maximum value Vmax0 acquired in step 2460 of FIG. 24 (Vmax0 ⁇ N ⁇ ⁇ V1). Is set as the target value VREF.
- the value ⁇ V1 corresponds to the first change value, and is set to a value smaller than the absolute value of the difference between the maximum output value Max and the reference value Vf.
- step 2570 the CPU determines whether the target value VREF is equal to or less than the reference value Vf. If the target value VREF is less than or equal to the reference value Vf, the CPU proceeds to step 2580 to set the reference value Vf as the target value VREF, and then proceeds to step 2595 to end the present routine tentatively. On the other hand, when the target value VREF is larger than the reference value Vf, the CPU directly proceeds from step 2570 to step 2595 to end the present routine tentatively. In step 2580, the CPU may execute the same processing as step 2420 in FIG.
- the target value VREF is reversed from the value (Vmax0 ⁇ V1), and the air-fuel ratio determination result is inverted. Every time it is reduced, the value decreases by ⁇ V1, and finally matches the reference value Vf.
- the CPU starts processing from step 2600 of FIG. 26 at a predetermined timing, and determines whether or not the value of the target value increase flag XU is “1” in step 2610. At this time, if the value of the target value increase flag XU is not “1”, the CPU makes a “No” determination at step 2610 to directly proceed to step 2695 to end the present routine tentatively.
- step 2610 the CPU makes a “Yes” determination at step 2610 to proceed to step 2620.
- step 2620 the CPU determines whether or not “current time is immediately after the value of the target value increase flag XU has changed from“ 0 ”to“ 1 ”.
- the CPU makes a “Yes” determination at step 2620 to proceed to step 2630, sets the value of the counter N to “1”, and proceeds to step 2640. If the CPU does not execute step 2620 immediately after the target value increase flag XU has changed from “0” to “1”, the CPU makes a “No” determination at step 2620 to perform step 2620. Proceed directly to 2640.
- step 2640 the CPU determines whether the air-fuel ratio determination result is reversed. If the air-fuel ratio determination result is reversed, the CPU makes a “Yes” determination at step 2640 to proceed to step 2650 to increase the value of the counter N by “1”, and then proceeds to step 2660. On the other hand, if the air-fuel ratio determination result is not reversed, the CPU makes a “No” determination at step 2640 to directly proceed to step 2660.
- step 2660 the CPU adds a value (Vmin0 + N ⁇ ⁇ V2) obtained by adding “the product of the value N and a positive constant value ⁇ V2” to the initial minimum value Vmin0 acquired in step 2490 of FIG. Set as target value VREF.
- the value ⁇ V2 corresponds to the first change value, and is set to a value smaller than the absolute value of the difference between the minimum output value Min and the reference value Vf.
- step 2670 the CPU determines whether or not the target value VREF is greater than or equal to the reference value Vf. If the target value VREF is greater than or equal to the reference value Vf, the CPU proceeds to step 2680 to set the reference value Vf as the target value VREF, and then proceeds to step 2695 to end the present routine tentatively. On the other hand, when the target value VREF is smaller than the reference value Vf, the CPU directly proceeds from step 2670 to step 2695 to end the present routine tentatively. Note that the CPU may execute the same processing in step 2680 as in step 2420 in FIG.
- the target value VREF is changed from the value (Vmin0 + ⁇ V1) every time the air-fuel ratio determination result is inverted. Increases by a value ⁇ V1 and finally matches the reference value Vf.
- the tenth control device determines that the maximum value Vmax obtained after the start of the sub-feedback control or the like (when the value of the target value convergence control execution flag XVSFB is “0”) is “the first reference value Vf.
- the threshold value A1 is larger than the value (Vf + A1) ", the target value VREF is gradually decreased from the" value between the maximum value Vmax and the reference value Vf (Vmax0- ⁇ V1) "toward the reference value Vf. . That is, the tenth control device also executes target value convergence control.
- the initial value of the target value convergence control is a value (Vmax0 ⁇ V1).
- This value (Vmax0 ⁇ V1) is one of the “region larger than the reference value Vf and the region smaller than the reference value Vf”, and the “output value Voxs of the downstream air-fuel ratio sensor ( The current output value Voxs) is a value in a region (in this example, a region on the side larger than the reference value Vf) ”.
- the tenth control apparatus determines that the minimum value Vmin obtained after the start of the sub-feedback control (when the value of the target value convergence control execution flag XVSFB is “0”) is greater than the value (Vf ⁇ A2).
- the target value VREF is gradually increased from the value (Vmin0 + ⁇ V2) between the minimum value Vmin and the reference value Vf toward the reference value Vf. That is, the tenth control device also executes target value convergence control.
- the initial value of the target value convergence control is a value (Vmin0 + ⁇ V2).
- This value (Vmin0 + ⁇ V2) is one of the “region larger than the reference value Vf and the region smaller than the reference value Vf”, and the “output value Voxs of the downstream air-fuel ratio sensor (current The output value Voxs) is a value in a region (in this example, a region on the side smaller than the reference value Vf) ”.
- the value A1 and the value A2 may be the same or different from each other, and the value ⁇ V1 and the value ⁇ V2 may be the same or different from each other.
- a control device according to an eleventh embodiment of the present invention (hereinafter simply referred to as “eleventh control device”) will be described.
- the eleventh control device is different from the first control device only in that the sub feedback amount Vafsfb is changed into a rectangular wave shape based on the rich request and the lean request. Therefore, hereinafter, this difference will be mainly described.
- the CPU of the eleventh control device executes the routines shown in FIGS. 8, 9, 11 to 13, and the routine shown in FIG. 27 instead of FIG.
- the routines shown in FIGS. 8, 9, and 11 to 13 have been described. Therefore, the routine shown in FIG. 27 will be described.
- the CPU of the eleventh control device executes the routine shown in FIG. 27 every time a predetermined time elapses.
- the CPU starts processing from step 2700 in FIG. 27 and proceeds to step 2710 to determine whether or not the sub-feedback control condition is satisfied. At this time, if the sub feedback control condition is not satisfied, the CPU makes a “No” determination at step 2710 to proceed to step 2720 to set the sub feedback amount Vafsfb to “0”. Thereafter, the CPU proceeds to step 2795 to end the present routine tentatively.
- step 2710 the CPU makes a “Yes” determination at step 2715 to proceed to step 2715, where the rich determination flag XR It is determined whether the value of “1” is “1”. That is, the CPU determines whether a lean request has occurred.
- the value of the rich determination flag XR is set by the routine shown in FIG.
- the CPU makes a “Yes” determination at step 2710 to proceed to step 2730.
- the sub-feedback control is set to a negative constant value ( ⁇ Vsfb).
- the value Vsfb is a positive constant value. Thereafter, the CPU proceeds to step 2795.
- the feedback control output value Vabyfc obtained by the above equation (2) is smaller than the output value Vabyfs of the upstream air-fuel ratio sensor 55 by the value Vsfb. Therefore, the feedback control output value Vabyfc is corrected to a value corresponding to the richer air-fuel ratio than the output value Vabyfs of the upstream air-fuel ratio sensor 55. As a result, the commanded fuel injection amount Fi is reduced, so that the air-fuel ratio of the engine and the air-fuel ratio of the catalyst inflow gas become large (lean side air-fuel ratio).
- step 2715 when the value of the rich determination flag XR is “0” at the time when the CPU executes the process of step 2715 (that is, when it is determined that a rich request has occurred), the CPU proceeds to step 2715. If it is determined as “No”, the process proceeds to step 2740 to set the sub feedback control to a positive constant value (Vsfb). Thereafter, the CPU proceeds to step 2795.
- the feedback control output value Vabyfc obtained by the above equation (2) is larger than the output value Vabyfs of the upstream air-fuel ratio sensor 55 by the value Vsfb. Therefore, the feedback control output value Vabyfc is corrected to a value corresponding to the leaner air-fuel ratio than the output value Vabyfs of the upstream air-fuel ratio sensor 55. As a result, since the command fuel injection amount Fi is increased, the air-fuel ratio of the engine and the air-fuel ratio of the catalyst inflow gas become small (the air-fuel ratio becomes rich).
- each air-fuel ratio control apparatus sets the target value VREF to the “reference value” when the deviation of the output value Voxs of the downstream air-fuel ratio sensor from the reference value Vf becomes large.
- the value gradually approaches the “reference value Vf” from the “value different from the value Vf”.
- the air-fuel ratio of the engine is quickly switched, so that the air-fuel ratio of the catalyst inflow gas approaches “an appropriate air-fuel ratio for the catalyst 43 to purify the exhaust gas with high purification efficiency”. Therefore, the emission can be maintained well.
- the downstream air-fuel ratio sensor 56 is a concentration cell type O 2 sensor including a zirconia element, it may be a limit current-type wide-area air-fuel ratio sensor. Further, the downstream air-fuel ratio sensor may be an oxygen concentration sensor using titania as an element.
- the upstream air-fuel ratio sensor 55 is a limit current type wide-area air-fuel ratio sensor, but may be a concentration cell type O 2 sensor.
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Abstract
Description
(1)触媒と下流側空燃比センサとの間に距離があるため、触媒流出ガスが下流側空燃比センサの素子に到達するまでに時間を要すること。
(2)下流側空燃比センサには一般に保護カバーが備えられているので、触媒流出ガスが下流側空燃比センサの素子に到達するまでに時間を要すること。
(3)下流側空燃比センサの素子が「酸素平衡後のガスを素子に到達させるための層(例えば、拡散抵抗層)」により覆われているため、その素子に到達するガスの酸素分圧の変化が遅れること。この遅れは、下流側空燃比センサの素子の周囲に、それまでに蓄積された酸素又は未燃物が存在するとき、顕著になる。
内燃機関の排気通路に配設された触媒と、前記排気通路であって前記触媒の下流に配設される下流側空燃比センサと、空燃比制御手段と、を備える。
前記フィードバック制御において用いられる前記目標値を、所定の基準値に、「前記基準値よりも大きい側の領域及び前記基準値よりも小さい側の領域」の何れが一方の領域であって前記下流側空燃比センサの出力値が存在している領域内の所定の値から、時間経過とともに徐々に近づける。
この極値取得手段は、
(1)前記下流側空燃比センサの出力値が前記基準値から離れる方向に変化する状態から前記基準値に近づく方向に変化する状態へと変化したときの同出力値を、第1極値として取得し、且つ、
(2)前記下流側空燃比センサの出力値が前記基準値に近づく方向に変化する状態から前記基準値から離れる方向へと変化する状態へと変化したときの同出力値を、第2極値として取得する。
前記第2値を、前記取得された第2極値(k2(1))と前記第1値との間の値に設定するように構成されることが好ましい。
前記第2極値が取得された時点である第2極値取得時点以降において取得される前記第1極値k1(2)と前記基準値との差の絶対値が、前記第2極値取得時点以前において取得された前記第1極値k1(1)と前記基準値との差の絶対値よりも小さくなるように、前記第2値を設定することが好ましい。
前記極値取得手段により前記第1極値(k1(1))が取得された場合に、
「その取得された第1極値(k1(1))と前記基準値との差の絶対値」が正の第1閾値よりも大きいとき「前記第1値を前記目標値として設定」し、
「その取得された第1極値(k1(1))と前記基準値との差の絶対値」が前記第1閾値以下であるとき「前記基準値を前記目標値として設定する」ように構成される。
前記第1極値(k1(1))に比べて正の第1変更値(A)だけ前記基準値に近い値(X1)を前記第1値として設定し、且つ、前記第2極値(k2(1))に比べて正の第2変更値(B)だけ前記基準値から遠い値(X2)を前記第2値として設定するように構成され、
前記第1変更値(A)は前記第1閾値(A)以下であり、且つ、
前記第2変更値(B)は前記第1変更値(A)よりも小さいことが望ましい。
なお、図6の例において第1変更値(A)は値A1であり、第2変更値(B)は値B1である。図7の例において第1変更値(A)は値A2であり、第2変更値(B)は値B2である。
更に、第2極値(k2(1))が基準値Vfよりも大きいとき第2値(X2)は値(k2(1))+B)であり、第2極値(k2(1))が基準値Vfよりも小さいとき第2値(X2)は値(k2(1)−B)である。
(構成)
図1は、本発明の第1実施形態に係る空燃比制御装置(以下、「第1制御装置」とも称呼する。)が適用される内燃機関10の概略構成を示している。機関10は、4サイクル・火花点火式・多気筒(本例において4気筒)・ガソリン燃料機関である。機関10は、本体部20、吸気系統30及び排気系統40を備えている。
次に、上記第1制御装置による「空燃比のフィードバック制御」の概要について説明する。第1制御装置は、以下に述べる<判定方法>に従って、目標値VREFを決定するとともに空燃比の判定を行い、その空燃比の判定に基いて「リーン要求及びリッチ要求」の何れの空燃比要求が発生しているかを決定する。
第1制御装置は、出力値Voxsが目標値VREFよりも大きいとき、空燃比は「リッチ」であると判定する。従って、第1制御装置は、出力値Voxsが目標値VREFよりも大きいとき、リーン要求が発生していると判定する。
第1制御装置は、出力値Voxsが目標値VREFよりも小さいとき、空燃比は「リーン」であると判定する。従って、第1制御装置は、出力値Voxsが目標値VREFよりも小さいとき、リッチ要求が発生していると判定する。
(1)現時点の空燃比が「リッチ」であると判定され、従って、リーン要求が発生している場合(機関の空燃比が増大されている場合)。
下流側空燃比センサの出力値Voxsが目標値VREFよりも小さい値から大きい値へと変化したとき、空燃比はリッチに変化した(リーン要求が発生した)と判定される。リーン要求が発生していると、機関の空燃比が増大させられるので触媒流入ガスの空燃比は増大させられ、触媒43に多量の酸素が流入する。従って、リーン要求が所定時間継続すると、触媒43の下流に酸素が流出し始める。この結果、下流側空燃比センサの出力値Voxsは、リーン要求が発生している期間において、増大した後に減少し始める。第1制御装置は、この出力値Voxsの極大値Vmaxを取得する。
(1−1a)「極大値Vmaxから正の一定値A1(正の第1閾値)を減じた値(Vmax−A1)」が基準値Vfよりも大きいとき、第1制御装置は「値(Vmax−A1)」を目標値VREFとして設定する(図4の(A)を参照。)。極大値Vmaxから減算される値A1は、第1変更値とも称呼される。
(1−1b)「極大値Vmaxから正の一定値A1(正の第1閾値)を減じた値(Vmax−A1)」が基準値Vfよりも小さいとき、第1制御装置は基準値Vfを目標値VREFとして設定する(図4の(B)を参照。)。
第1制御装置は「極大値Vmaxから正の一定値B2を減じた値(Vmax−B2)」を目標値VREFとして設定する(図4の(C)を参照。)。値B2は、第2変更値とも称呼される。
下流側空燃比センサの出力値Voxsが目標値VREFよりも大きい値から小さい値へと変化したとき、空燃比はリーンに変化した(リッチ要求が発生した)と判定される。リッチ要求が発生していると、機関の空燃比が減少させられるので触媒流入ガスの空燃比は減少させられ、触媒43に多量の未燃物が流入する。従って、リッチ要求が所定時間継続すると、触媒43の下流に未燃物が流出し始め、酸素は殆ど流出しなくなる。この結果、下流側空燃比センサの出力値Voxsは、リッチ要求が発生している期間において、減少した後に増大し始める。第1制御装置は、この出力値Voxsの極小値Vminを取得する。
(2−1a)「極小値Vminに正の一定値A2(正の第1閾値)を加えた値(Vmin+A2)」が基準値Vfよりも小さいとき、第1制御装置は「値(Vmin+A2)」を目標値VREFとして設定する(図5の(A)を参照。)。極小値Vminに加算される値A2は、第1変更値とも称呼される。
(2−1b)「極小値Vminに正の一定値A2(正の第1閾値)を加えた値(Vmin+A2)」が基準値Vfよりも大きいとき、第1制御装置は基準値Vfを目標値VREFとして設定する(図5の(B)を参照。)。
第1制御装置は「極小値Vminに正の一定値B1を加えた値(Vmin+B1)」を目標値VREFとして設定する(図5の(C)を参照。)。値B1は、第2変更値とも称呼される。
値A1は値B1よりも正の所定値以上大きい(A1>B1>0、図5の(C)を参照。)。但し、値A1は最大出力値Maxと基準値Vfとの差の絶対値よりも正の所定値e1だけ小さい。前述したように、値A1は第1変更値とも称呼され、値B1は第2変更値とも称呼される。
値A2は値B2よりも正の所定値以上大きい(A2>B2>0、図4の(C)を参照。)但し、値A2は最小出力値Minと基準値Vfとの差の絶対値よりも正の所定値e2だけ小さい。前述したように、値A2は第1変更値とも称呼され、値B2は第2変更値とも称呼される。
値A1と値A2とは、互いに等しい値Aであってもよい。
値B1と値B2とは、互いに等しい値Bであってもよい。
次に、上記判定方法に基く空燃比制御の状況について説明する。図6は、時刻t1以前において触媒43の酸素吸蔵量OSAが小さくなり、その結果、下流側空燃比センサの出力値Voxsが基準値Vfよりも相当に大きくなった場合の「出力値Voxs及び要求空燃比等」の変化を示している。
次に、第1制御装置の実際の作動について説明する。以下、説明の便宜上、「MapX(a1,a2,…)」は、「a1,a2,…を引数とするテーブル」であって「値Xを求めるためのテーブル」を表すものとする。
第1制御装置のCPUは、図8に示した燃料噴射制御ルーチンを、任意の気筒のクランク角度が吸気上死点前の所定クランク角度となる毎に、その気筒に対して繰り返し実行するようになっている。前記所定クランク角度は、例えば、BTDC90°CA(吸気上死点前90°クランク角度)である。クランク角度が前記所定クランク角度に一致した気筒は「燃料噴射気筒」とも称呼される。CPUは、この燃料噴射制御ルーチンにより、指示燃料噴射量(最終燃料噴射量)Fiの計算及び燃料噴射の指示を行う。
CPUは図9にフローチャートにより示した「メインフィードバック制御ルーチン」を所定時間taの経過毎に繰り返し実行している。従って、所定のタイミングになると、CPUはステップ900から処理を開始し、ステップ905に進んで「メインフィードバック制御条件(上流側空燃比フィードバック制御条件)」が成立しているか否かを判定する。
(A1)上流側空燃比センサ55が活性化している。
(A2)機関の負荷KLが閾値KLth以下である。
(A3)フューエルカット制御中でない。
KL=(Mc/(ρ・L/4))・100% …(1)
Vabyfc=Vabyfs+Vafsfb …(2)
abyfsc=Mapabyfs(Vabyfc) …(3)
Fc(k−N)=Mc(k−N)/abyfsc …(4)
Fcr=Mc(k−N)/abyfr …(5)
DFc=Fcr(k−N)−Fc(k−N) …(6)
DFi=Gp・DFc+Gi・SDFc …(7)
FAF=(Fb(k−N)+DFi)/Fb(k−N)…(8)
FAFAVnew=q・FAF+(1−q)・FAFAV…(9)
ステップ985:CPUは、メインフィードバック係数FAFの値を「1」に設定する。
ステップ990:CPUは、筒内燃料供給量偏差の積分値SDFcを「0」に設定する。
ステップ992:CPUは、補正係数平均値FAFAVの値を「1」に設定する。
その後、CPUは、ステップ995に進んで本ルーチンを一旦終了する。
CPUは、サブフィードバック量Vafsfbを算出するために、所定時間が経過する毎に図10に示した「サブフィードバック制御ルーチン」を実行するようになっている。
(B1)メインフィードバック制御条件が成立している。
(B2)下流側空燃比センサ56が活性化している。
ステップ1015:CPUは、下記(10)式に従って、「目標値VREF」と「下流側空燃比センサ56の出力値Voxs」との差である「出力偏差量DVoxs」を取得する。即ち、CPUは、目標値VREFから出力値Voxsを減じることにより、出力偏差量DVoxsを求める。
DVoxs=VREF−Voxs …(10)
Vafsfb=Kp・DVoxs+Ki・SDVoxs+Kd・DDVoxs …(11)
ステップ1030:CPUは、「上記ステップ1015にて算出した出力偏差量DVoxs」から「本ルーチンを前回実行した際に算出された出力偏差量(前回出力偏差量DVoxsold)」を減じることにより、新たな出力偏差量の微分値DDVoxsを求める。
ステップ1035:CPUは、「上記ステップ1015にて算出した出力偏差量DVoxs」を「前回出力偏差量DVoxsold」として格納する。
Vafsfbg(k+1)=α・Vafsfbg+(1−α)・Ki・SDVoxs …(12)
ステップ1050:CPUは出力偏差量の積分値SDVoxsの値を「0」に設定する。
CPUは、「サブフィードバック制御に用いられる上記目標値VREF」を決定するために、所定時間が経過する毎に図11に示した「目標値決定ルーチン」を実行するようになっている。従って、所定のタイミングになると、CPUは図11のステップ1100から処理を開始してステップ1110に進み、上述した「サブフィードバック制御条件」が成立しているか否かを判定する。
ステップ1340:CPUは、目標値決定要求フラグXVREFreqの値を「1」に設定する。
その後、CPUはステップ1395及び図11のステップ1160を経由してステップ1195に進み、目標値決定ルーチンを一旦終了する。
ステップ1370:CPUは、目標値決定要求フラグXVREFreqの値を「1」に設定する。
その後、CPUはステップ1395及び図11のステップ1160を経由してステップ1195に進み、目標値決定ルーチンを一旦終了する。
サブフィードバック量Vafsfbは、図10に示したように、リッチ要求が発生している期間(即ち、出力値Voxsが目標値VREFよりも小さい期間)において機関の空燃比を減少する(指示燃料噴射量Fiを増大する)ように制御される。
前記極値取得手段により前記第1極値(基準値Vf以上である極大値Vmax、又は、基準値Vf以下である極小値Vmin)が取得された場合、その取得された第1極値と基準値Vfとの間の値である第1値(Vmax−A1、又は、Vmin+A2)を目標値VREFとして設定する(表1、図4の(A)、図4の(C)、図5の(A)、図5の(C)、図12のステップ1222、ステップ1238等を参照。)。
その後(「他方の要求」が発生したと判定した後)、前記極値取得手段によって前記第2極値(基準値Vfよりも大きい極小値Vmin、及び、基準値Vfよりも小さい極大値Vmax)が取得された場合、「その取得された第2極値」と「前記極値取得手段によって取得された前記第1極値(基準値Vfよりも大きい極大値Vmax、又は、基準値Vfよりも小さい極小値Vmin)」との間の値である第2値(Vmin+B1又はVmax−B2)、を目標値VREFとして設定する(表1、図4の(C)、図5の(C)、図12のステップ1228、ステップ1244等を参照。)。換言すると、第1制御装置の空燃比制御手段は、第2値が、最新の第1極値と最新の第2極値との間の値となるように、値B1及び値B1を設定している。
前記極値取得手段により前記第1極値が取得された場合、
(1)同取得された第1極値と前記基準値との差の絶対値が正の第1閾値(値A1又は値A2)よりも大きいとき(図12のステップ1220での「Yes」との判定又はステップ1236での「Yes」との判定を参照。)、前記第1値を目標値VREFとして設定し(ステップ1222又はステップ1238)、
(2)同取得された第1極値と前記基準値との差の絶対値が前記第1閾値以下であるとき(図12のステップ1220での「No」との判定又はステップ1236での「No」との判定を参照。)、基準値Vfを目標値VREFとして設定する(ステップ1226又はステップ1242)。なお、この場合、第1制御装置の判定装置は、出力値Voxsが「基準値Vfに設定された目標値VREF」を横切った第3時点において、同第3時点まで発生していると判定していた「前記リッチ要求及び前記リーン要求のうちの何れか一方」とは異なる「他方の要求」が発生したと判定する(図13のルーチン、図6の時刻t8以降、及び、図7の時刻t8以降等を参照。)、ように構成されている。
前記第1極値(例えば、極大値Vmax(1))に比べて正の第1変更値(値A1)だけ前記基準値に近い値(Vmax(1)−A1)を前記第1値として設定し、前記第2極値(極小値Vmin(1))に比べて正の第2変更値(値B1)だけ基準値Vfから遠い値(Vmin(1)+B1)を前記第2値として設定するように構成されている。この場合、前記第1変更値(値A1)は前記第1閾値以下(値A1)であればよく、且つ、前記第2変更値(値B1)は前記第1変更値(値A1)よりも小さいことが望ましい。
前記第1極値(例えば、極小値Vmin(1))に比べて正の第1変更値(値A2)だけ前記基準値に近い値(Vmin(1)+A2)を前記第1値として設定し、前記第2極値(極大値Vmax(1))に比べて正の第2変更値(値B2)だけ基準値Vfから遠い値(Vmax(1)−B2)を前記第2値として設定するように構成されている。この場合、前記第1変更値(値A2)は前記第1閾値以下(値A2)であればよく、且つ、前記第2変更値(値B2)は前記第1変更値(値A2)よりも小さいことが望ましい。
次に、本発明の第2実施形態に係る制御装置(以下、単に「第2制御装置」と称呼する。)について説明する。第2制御装置は、第1変更値(値A1及び値A2)と第2変更値(値B1及び値B2)とを、下流側空燃比センサ56の温度(素子温度)が低いほど「より小さく」する点のみにおいて、第1制御装置と相違している。
次に、本発明の第3実施形態に係る制御装置(以下、単に「第3制御装置」と称呼する。)について説明する。第3制御装置は、第1変更値(値A1及び値A2)及び第2変更値(値B1及び値B2)を、触媒43を通過する排ガスの流量(従って、吸入空気量Ga)が小さいほど「より小さく」する点のみにおいて、第1制御装置と相違している。
次に、本発明の第4実施形態に係る制御装置(以下、単に「第4制御装置」と称呼する。)について説明する。第4制御装置は、第1変更値(値A1及び値A2)を、第1極値(基準値Vfよりも大きい極大値Vmax、及び、基準値Vfよりも小さい極小値Vmin)が大きいほど「より小さく」する点のみにおいて、第1制御装置と相違している。
前記第1極値(例えば、極大値Vmax)と基準値Vfとの差の絶対値が正の第2閾値(A1+a1)よりも大きい場合における前記第1変更値の値を、前記第1極値と前記基準値との差の絶対値が前記第2閾値以下である場合における前記第1変更値の値(A1)よりも小さい値(A1s)に設定するように構成された装置であると言うことができる。
前記第1極値(例えば、極小値Vmin)と基準値Vfとの差の絶対値が正の第2閾値(A2+a2)よりも大きい場合における前記第1変更値の値を、前記第1極値と前記基準値との差の絶対値が前記第2閾値以下である場合における前記第1変更値の値(A2)よりも小さい値(A2s)に設定するように構成された装置であると言うことができる。
前記第1極値(例えば、極大値Vmax)と基準値Vfとの差の絶対値が正の第2閾値(A1+a1)よりも大きい場合における前記第2変更値の値を、前記第1極値と前記基準値との差の絶対値が前記第2閾値以下である場合における前記第2変更値の値(B1)よりも小さい値(B1s)に設定するように構成されてもよい。
前記第1極値(例えば、極小値Vmin)と基準値Vfとの差の絶対値が正の第2閾値(A2+a2)よりも大きい場合における前記第2変更値の値を、前記第1極値と前記基準値との差の絶対値が前記第2閾値以下である場合における前記第2変更値の値(B2)よりも小さい値(B2s)に設定するように構成されてもよい。
次に、本発明の第5実施形態に係る制御装置(以下、単に「第5制御装置」と称呼する。)について説明する。第5制御装置は、第1変更値(値A1及び値A2の少なくとも一方)を、フューエルカット制御の終了時点から所定時間が経過する時点までの期間(フューエルカット制御終了後期間)、フューエルカット制御終了後期間以外の期間に比べ、小さくする点のみにおいて、第1制御装置と相違している。
次に、本発明の第6実施形態に係る制御装置(以下、単に「第6制御装置」と称呼する。)について説明する。第6制御装置は、第1変更値(値A1及び値A2)を、機関が所定の加速状態にある場合、機関が所定の加速状態にない場合(定常状態にある場合)に比べ、「より小さく」する点のみにおいて、第1制御装置と相違している。
次に、本発明の第7実施形態に係る制御装置(以下、単に「第7制御装置」と称呼する。)について説明する。第7制御装置は、メインFB学習値KGの学習条件を第1制御装置の学習条件と異なる条件とした点においてのみ、第1制御装置と相違している。従って、以下、この相違点を中心として説明する。
(条件1)図9のルーチンが実行される時間間隔(所定時間ta)の自然数倍の時間が経過した。
(条件2)目標値VREFが基準値Vfに一致した状態が所定時間t以上経過している。
機関10に吸入される吸入空気量(筒内吸入空気量Mc(k))を取得するとともに(図8のステップ830)、その取得された吸入空気量(筒内吸入空気量Mc(k))に基づいて「機関10に供給される混合気」の空燃比を理論空燃比に一致させるための基本燃料噴射量Fbを算出する(図8のステップ840)基本燃料噴射量算出手段と、
前記排気通路であって触媒43よりも上流に配設されるとともに、触媒43に流入する排ガスの空燃比に応じた出力値を出力する上流側空燃比センサ55と、
上流側空燃比センサ55の出力値Vabyfsにより表される上流側空燃比(abyfs)が理論空燃比に一致するように基本燃料噴射量Fbを補正するメインフィードバック量(DFi)を算出するメインフィードバック量算出手段(図9のステップ905乃至ステップ945)と、
前記リーン要求が発生していると判定されている期間において前記基本燃料噴射量を増大させるように前記基本燃料噴射量を補正し且つ前記リッチ要求が発生していると判定されている期間において前記基本燃料噴射量を減少させるように前記基本燃料噴射量を補正するサブフィードバック量(Vafsfb)を算出するサブフィードバック量算出手段(図10のステップ1005乃至ステップ1035)と、
基本燃料噴射量Fbを、前記メインフィードバック量及び前記サブフィードバック量に基く空燃比補正量(FAF)により補正して指示燃料噴射量Fiを算出するとともに(図9のステップ910及び図8のステップ850等)、その算出された指示燃料噴射量Fiの燃料を機関10に供給することにより前記フィードバック制御を実行する(図8のステップ860等)燃料噴射量制御手段と、
を含む空燃比制御装置である。
前記メインフィードバック量の平均値に相関する値(例えば、FAFAV、又はFAFAVが大きいとき増大し且つFAFAVが小さいとき減少する値)を空燃比学習値(メインFB学習値KG)として取得する学習制御を実行する学習手段(図9のステップ950乃至ステップ975)を備え、
前記燃料噴射量制御手段は、
前記基本燃料噴射量Fbを前記空燃比学習値KGにも基いて補正することにより前記指示燃料噴射量を算出するように構成され(図8のステップ850)、
第7制御装置の前記学習手段は、
前記目標値が前記基準値に設定されている場合に前記学習制御を実行し、且つ、前記目標値が前記基準値に設定されていない場合に前記学習制御を実行しないように構成されている(図9のステップ955、及び、上述した(条件2)を参照。)。
次に、本発明の第8実施形態に係る制御装置(以下、単に「第8制御装置」と称呼する。)について説明する。第8制御装置は、目標値VREFが基準値Vfに収束しない場合、目標値VREFに相関する値に基いて空燃比学習値(メインFB学習値KG)を修正するように構成されている点においてのみ、第7制御装置と相違する。従って、以下、この相違点を中心として説明する。
次に、本発明の第9実施形態に係る制御装置(以下、単に「第9制御装置」と称呼する。)について説明する。第9制御装置は、目標値VREFが基準値Vfに収束せず且つ図22に示した目標値振動状態が発生している場合、目標値振動状態が発生していない場合に比べ、第1変更値(値A1及び値A2)を小さくする点のみにおいて、第8制御装置と相違している。従って、以下、この相違点を中心として説明する。
目標値VREFが「基準値Vfよりも大きい値(例えば、Vmax−A1)」と「基準値Vfよりも小さい値(例えば、Vmin+A2)」とに交互に変化する状態が所定時間以上継続する状態(即ち、目標値振動状態)が発生した場合、第1変更値の値(値A1、値A2)をより小さくするように構成された学習手段を備えている。
次に、本発明の第10実施形態に係る制御装置(以下、単に「第10制御装置」と称呼する。)について説明する。第10制御装置は、目標値VREFを時間経過とともに基準値Vfに強制的に接近させる点のみにおいて、第1制御装置と相違している。従って、以下、この相違点を中心として説明する。
CPUは、目標値減少フラグXDの値を「0」に設定する。
CPUは、目標値増大フラグXUの値を「0」に設定する。
CPUは、基準値Vfを目標値VREFとして設定する。
CPUは、目標値減少フラグXDの値を「1」に設定する。
CPUは、目標値増大フラグXUの値を「0」に設定する。
CPUは、極大値Vmaxを初期極大値Vmax0として格納する。
CPUは、目標値減少フラグXDの値を「0」に設定する。
CPUは、目標値増大フラグXUの値を「1」に設定する。
CPUは、極小値Vminを初期極小値Vmin0として格納する。
次に、本発明の第11実施形態に係る制御装置(以下、単に「第11制御装置」と称呼する。)について説明する。第11制御装置は、サブフィードバック量Vafsfbをリッチ要求及びリーン要求に基いて矩形波状に変化させる点のみにおいて、第1制御装置と相違している。従って、以下、この相違点を中心として説明する。
Claims (16)
- 内燃機関の排気通路に配設された触媒と、
前記排気通路であって前記触媒の下流に配設され且つ酸素分圧に応じて変化する出力値を示す素子を備える下流側空燃比センサと、
前記下流側空燃比センサの出力値を所定の目標値に近づけるために前記機関に供給される混合気の空燃比である機関の空燃比を増大させる必要があるリーン要求の発生期間において前記機関の空燃比を増大し、前記下流側空燃比センサの出力値を前記目標値に近づけるために前記機関の空燃比を減少させる必要があるリッチ要求の発生期間において前記機関の空燃比を減少する、フィードバック制御を実行する空燃比制御手段と、
を備える内燃機関の空燃比制御装置において、
前記空燃比制御手段は、
前記目標値を、前記下流側空燃比センサの素子に到達しているガスの酸素分圧が同ガスの空燃比が理論空燃比であるときの酸素分圧であるときに前記下流側空燃比センサの素子の出力値が示す値を含む所定の範囲内の値である基準値に、前記基準値よりも大きい側の領域及び前記基準値よりも小さい側の領域の何れか一方の領域であって前記下流側空燃比センサの出力値が存在している領域内の所定の値から時間経過とともに徐々に近づける目標値変更手段、
を備える空燃比制御装置。 - 請求項1に記載の空燃比制御装置において、
前記空燃比制御手段は、
前記下流側空燃比センサの出力値が前記基準値から離れる方向に変化する状態から前記基準値に近づく方向に変化する状態へと変化したときの同出力値を第1極値として取得し、且つ、前記下流側空燃比センサの出力値が前記基準値に近づく方向に変化する状態から前記基準値から離れる方向へと変化する状態へと変化したときの同出力値を第2極値として取得する極値取得手段を含み、
前記目標値変更手段は、
前記極値取得手段により前記第1極値が取得された場合に同取得された第1極値と前記基準値との間の値である第1値を前記目標値として設定し、その後、前記極値取得手段によって前記第2極値が取得された場合に同取得された第2極値と前記極値取得手段によって取得された前記第1極値との間の値である第2値を前記目標値として設定するように構成された空燃比制御装置。 - 請求項2に記載の空燃比制御装置において、
前記目標値変更手段は、
前記第2値を、前記取得された第2極値と前記第1値との間の値に設定するように構成された空燃比制御装置。 - 請求項3に記載の空燃比制御装置において、
前記目標値変更手段は、
前記第2極値が取得された時点である第2極値取得時点以降において取得される前記第1極値と前記基準値との差の絶対値が、前記第2極値取得時点以前において取得された前記第1極値と前記基準値との差の絶対値よりも小さくなるように、前記第2値を設定する空燃比制御装置。 - 請求項2乃至請求項4の何れか一項に記載の空燃比制御装置において、
前記目標値変更手段は、
前記極値取得手段により前記第1極値が取得された場合に同取得された第1極値と前記基準値との差の絶対値が正の第1閾値よりも大きいとき前記第1値を前記目標値として設定し、同取得された第1極値と前記基準値との差の絶対値が前記第1閾値以下であるとき前記基準値を前記目標値として設定するように構成された空燃比制御装置。 - 請求項5に記載の空燃比制御装置において、
前記目標値変更手段は、
前記第1極値に比べて正の第1変更値だけ前記基準値に近い値を前記第1値として設定し、且つ、前記第2極値に比べて正の第2変更値だけ前記基準値から遠い値を前記第2値として設定するように構成され、
前記第1変更値は前記第1閾値以下であり、且つ、
前記第2変更値は前記第1変更値よりも小さい空燃比制御装置。 - 請求項6に記載の空燃比制御装置において、
前記目標値変更手段は、
前記下流側空燃比センサの温度が低いほど前記第1変更値をより小さくするように構成された空燃比制御装置。 - 請求項6に記載の空燃比制御装置において、
前記目標値変更手段は、
前記触媒を通過する排ガスの流量が大きいほど前記第1変更値をより小さくするように構成された空燃比制御装置。 - 請求項6に記載の空燃比制御装置において、
前記目標値変更手段は、
前記第1極値と前記基準値との差の絶対値が正の第2閾値よりも大きい場合における前記第1変更値の値を、前記第1極値と前記基準値との差の絶対値が前記第2閾値以下である場合における前記第1変更値の値よりも小さくするように構成された空燃比制御装置。 - 請求項6に記載の空燃比制御装置において、
前記目標値変更手段は、
前記機関の運転状態が、前記機関への燃料の供給を停止するフューエルカット状態から前記機関への燃料の供給を行う燃料供給状態へと変化した時点から、所定時間が経過する時点までのフューエルカット終了後期間における前記第1変更値の値を、前記フューエルカット終了後期間以外の期間における前記第1変更値の値よりも小さくするように構成された空燃比制御装置。 - 請求項6に記載の空燃比制御装置において、
前記目標値変更手段は、
前記機関が所定の加速状態にあるか否かを判定するとともに、前記機関が前記加速状態にあると判定された場合の前記第1変更値の値を、前記機関が前記加速状態にあると判定されていない場合の前記第1変更値の値よりも小さくするように構成された空燃比制御装置。 - 請求項6に記載の空燃比制御装置において、
前記空燃比制御手段は、
前記機関に吸入される吸入空気量を取得するとともに同取得された吸入空気量に基づいて前記機関に供給される混合気の空燃比を理論空燃比に一致させるための基本燃料噴射量を算出する基本燃料噴射量算出手段と、
前記排気通路であって前記触媒よりも上流に配設されるとともに前記触媒に流入する排ガスの空燃比に応じた出力値を出力する上流側空燃比センサと、
前記上流側空燃比センサの出力値により表される上流側空燃比が理論空燃比に一致するように前記基本燃料噴射量を補正するメインフィードバック量を算出するメインフィードバック量算出手段と、
前記リーン要求が発生していると判定されている期間において前記基本燃料噴射量を増大させるように前記基本燃料噴射量を補正し且つ前記リッチ要求が発生していると判定されている期間において前記基本燃料噴射量を減少させるように前記基本燃料噴射量を補正するサブフィードバック量を算出するサブフィードバック量算出手段と、
前記基本燃料噴射量を、前記メインフィードバック量及び前記サブフィードバック量に基く空燃比補正量により補正して指示燃料噴射量を算出するとともに、同算出された指示燃料噴射量の燃料を前記機関に供給することにより前記フィードバック制御を実行する燃料噴射量制御手段と、
を含む空燃比制御装置。 - 請求項12に記載の空燃比制御装置において、
前記空燃比制御手段は、
前記メインフィードバック量の平均値に相関する値を空燃比学習値として取得する学習制御を実行する学習手段を備え、
前記燃料噴射量制御手段は、
前記基本燃料噴射量を前記空燃比学習値にも基いて補正することにより前記指示燃料噴射量を算出するように構成され、
前記学習手段は、
前記目標値が前記基準値に設定されている場合に前記学習制御を実行し、且つ、前記目標値が前記基準値に設定されていない場合に前記学習制御を実行しないように構成された空燃比制御装置。 - 請求項13に記載の空燃比制御装置において、
前記下流側空燃比センサは、
前記触媒から流出する排ガスに含まれる酸素の濃度に応じた電圧を前記下流側空燃比センサの出力値として出力する濃淡電池型の酸素濃度センサであり、
前記学習手段は、
前記目標値が第1継続時間以上に渡り前記基準値に一致している状態が第2継続時間以上に渡って発生していない場合、前記目標値の平均値に相関する値が前記基準値よりも大きいとき、前記空燃比学習値を、前記基本燃料噴射量をより減少補正する値へと修正するように構成された空燃比制御装置。 - 請求項13に記載の空燃比制御装置において、
前記下流側空燃比センサは、
前記触媒から流出する排ガスに含まれる酸素の濃度に応じた電圧を前記下流側空燃比センサの出力値として出力する濃淡電池型の酸素濃度センサであり、
前記学習手段は、
前記目標値が第1継続時間以上に渡り前記基準値に一致している状態が第2継続時間以上に渡って発生していない場合、前記目標値の平均値に相関する値が前記基準値よりも小さいとき、前記空燃比学習値を、前記基本燃料噴射量をより増大補正する値へと修正するように構成された空燃比制御装置。 - 請求項13に記載の空燃比制御装置において、
前記下流側空燃比センサは、
前記触媒から流出する排ガスに含まれる酸素の濃度に応じた電圧を前記下流側空燃比センサの出力値として出力する濃淡電池型の酸素濃度センサであり、
前記目標値変更手段は、
前記目標値が、前記基準値よりも大きい値と前記基準値よりも小さい値とに交互に変化する状態が所定時間以上継続する状態である目標値振動状態が発生した場合、前記第1変更値の値を、前記目標値振動状態が発生していない場合の前記第1変更値の値よりも小さくするように構成された空燃比制御装置。
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JP5429230B2 (ja) * | 2011-06-22 | 2014-02-26 | トヨタ自動車株式会社 | 多気筒内燃機関の気筒間空燃比ばらつき異常検出装置 |
KR101551017B1 (ko) * | 2013-12-18 | 2015-09-07 | 현대자동차주식회사 | 차량의 배기가스 정화 시스템 |
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- 2010-05-28 WO PCT/JP2010/059486 patent/WO2011148517A1/ja active Application Filing
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US20130110380A1 (en) | 2013-05-02 |
JPWO2011148517A1 (ja) | 2013-07-25 |
JP5293889B2 (ja) | 2013-09-18 |
US9790873B2 (en) | 2017-10-17 |
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