JP3879603B2 - Engine air-fuel ratio control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine air-fuel ratio control apparatus.
[0002]
[Prior art]
A device for correcting the fuel wall flow has been proposed (see JP-A-10-259748).
[0003]
[Problems to be solved by the invention]
By the way, from the viewpoint of improving fuel efficiency, an intake valve operation stop mechanism capable of stopping the operation of the intake valve (for example, an intake valve itself using an electromagnetically driven valve or a cam driven valve capable of stopping the intake valve is provided. In other words, a so-called cylinder stop engine has been proposed in which the mechanism is operated to stop the operation of the intake valve when a predetermined operating range such as a low load low rotational speed range is provided. This is intended to reduce the pump loss by stopping the operation of the intake valve (which also contributes to the reduction of power consumption in the electromagnetically driven valve) and to improve the fuel efficiency accordingly.
[0004]
Here, “cylinder stop” is defined as follows. That is,
1) Assuming an engine equipped with a fuel supply device that supplies fuel to the intake passage upstream including the intake port,
2) For at least one cylinder,
3) fix all intake valves of the one cylinder in the fully closed position; and
4) Stop the fuel supply to the first cylinder
Is defined as cylinder stop.
[0005]
From the above 1), it is outside the scope of the present invention that the fuel is directly injected into the cylinder from the fuel injection valve facing the cylinder. Accordingly, an object of the present invention is, for example, an MPI (multi-point injection) type fuel supply device provided with a fuel injection valve facing the intake port or a fuel that supplies fuel for all cylinders to the intake collector portion. An SPI (single point injection) type fuel supply device provided with an injection valve is an object. It is even more desirable to stop ignition and energization as necessary together with stopping fuel supply when the cylinder is stopped.
[0006]
From the above 3), what fixes the intake valve to a fully open position other than the fully closed position, for example, is out of scope in the present invention. This is to handle the fuel wall flow remaining on the upstream side of the intake valve by fixing the intake valve to the fully closed position, as will be described later.
[0007]
Since the exhaust valve is not defined from the above 3), the operation of the exhaust valve may be stopped or may remain operating.
[0008]
The operating range for stopping the cylinder is currently considered to be a low-load low-rotation speed range including idle. Therefore, when the cylinder stop operation range is exceeded, the cylinder stop is released and the fuel supply is resumed.
[0009]
Also, an engine that stops cylinders performs a fuel cut that is conventional. In the engine of the present invention, “fuel cut” is defined as follows. That is,
5) For at least one cylinder
6) The operation of the intake valve and exhaust valve of the cylinder 1 remains in the operating state, and
7) Stop the fuel supply to the first cylinder
Is defined as a fuel cut.
[0010]
For this reason, if one cylinder is a fuel cut cylinder, the intake valve is operated in the one cylinder. When all the intake valves are fixed at the fully closed position in the same one cylinder, the one cylinder is in a cylinder stopped state.
[0011]
The method of fuel cut is the same as before. That is, if the accelerator pedal is in the idle position above the predetermined rotational speed, the fuel cut is started, and if the accelerator pedal is stepped on from that state, or if the rotational speed decreases to a predetermined rotational speed (recover rotational speed) or less. Stop the fuel cut and restart the fuel supply.
[0012]
Various methods are conceivable as follows for the method of stopping the cylinder in the multi-cylinder engine and the method of restarting the fuel supply after the cylinder is stopped, all of which are objects of the present invention.
[0013]
(1) The cylinder is stopped for each cylinder, and the fuel supply is resumed for each cylinder.
[0014]
(2) The cylinder is stopped for each predetermined group, and the fuel supply is restarted for each predetermined group.
[0015]
(3) Stop cylinders in all cylinders and restart fuel supply in all cylinders.
[0016]
(4) For example, in the case of a four-cylinder engine, the cylinders are first stopped for two cylinders and then all cylinders are stopped. First, the cylinder stop of the two cylinders is released and the fuel supply is restarted, then the cylinder stop of the remaining two cylinders is released and the fuel supply is restarted.
[0017]
The same applies to the fuel cut, and various modes can be considered as follows for the method of fuel cut in a multi-cylinder engine and the method of restarting fuel supply from the fuel cut, all of which are objects of the present invention.
[0018]
(5) The fuel is cut for each cylinder, the fuel cut is stopped for each cylinder, and the fuel supply is restarted.
[0019]
(6) The fuel cut is performed for each predetermined group, the fuel cut is stopped for each predetermined group, and the fuel supply is restarted.
[0020]
(7) Fuel is cut in all cylinders, fuel cut is stopped in all cylinders, and fuel supply is resumed.
[0021]
(8) For example, in the case of a four-cylinder engine, first, fuel is cut in two cylinders, and then fuel is cut in all cylinders. First, the fuel cut of the two cylinders is stopped and the fuel supply is restarted, and then the fuel cut of the remaining two cylinders is stopped and the fuel supply is restarted.
[0022]
The conventional air-fuel ratio control technique with fuel wall flow correction does not consider the case of stopping the cylinder as defined in the present invention, and the following problems arise.
[0023]
No. of the multi-cylinder engines One cylinder is specifically considered as a cylinder that performs fuel cut. During fuel cut, it adheres to the back of the intake valve and the intake port to form wall flow fuel, and this fuel wall flow flows into the cylinder along with the intake air. The fuel will decrease and eventually there will be no wall flow fuel. For this reason, in the above-described prior art, when the fuel cut is performed for the cylinder that performs fuel cut, the adhesion amount Mf that is a predictive variable of the wall flow fuel amount for the cylinder that performs fuel cut is gradually reduced, so that fuel recovery ( It is devised so that the fuel wall flow correction amount at the time of return from fuel cut does not become insufficient.
[0024]
However, the same No. When one cylinder is the cylinder for which the cylinder is stopped, which is the subject of the present invention, Since the intake valves of one cylinder are all fixed at the fully closed position and the intake valve at the fully closed position blocks the intake air and the movement of the wall flow fuel to the cylinder, the wall flow fuel remaining upstream of the intake valve is the cylinder. No, so no. The wall flow fuel for one cylinder does not decrease regardless of the passage of cylinder stop time.
[0025]
For this reason, no. For one cylinder, No. is the same as when the fuel is cut just because the fuel is not supplied when the cylinder is stopped. When the adhesion amount Mf per cylinder was gradually decreased, No. actually not decreased. Since the calculation is made to gradually reduce the amount of adhesion Mf per cylinder, no. When recovering fuel for one cylinder, the fuel wall flow correction amount becomes excessive. The air-fuel ratio at the time of resumption of fuel supply for one cylinder deviates from the target value and becomes rich.
[0026]
In this case, the amount of wall flow fuel greatly depends particularly on the temperature of a portion to which a part of the injected fuel adheres (hereinafter referred to as “fuel adhering portion”). Experiments have revealed that the temperature of the fuel adhering portion differs between when the fuel is cut and when the cylinder is stopped.
[0027]
Therefore, the present invention independently estimates the fuel adhering portion temperature at the time of cylinder stop for the cylinder that performs cylinder stop, and gives the fuel adhering portion temperature different from that at the time of fuel cut, so that the fuel from the cylinder stop for the cylinder that performs the cylinder stop is determined. The purpose is to optimize the fuel wall flow correction amount when resuming the supply.
[0028]
On the other hand, Japanese Patent Application Laid-Open No. 3-134237 discloses a technique for estimating the temperature of the fuel adhering portion at the time of fuel cut. However, there is no description about cylinder stoppage. For this reason, even in the cylinder where the cylinder is stopped, the temperature of the fuel attachment portion between the cylinder stop state and the fuel cut state is estimated by estimating the fuel attachment portion temperature at the time of fuel cut as in the cylinder where the fuel cut is performed. An error occurs in the estimated temperature value due to the difference, and an excess or deficiency in the fuel wall flow correction amount due to the temperature error. When the cylinder is stopped, the air-fuel ratio becomes less than the target value when the fuel supply is resumed from the cylinder stop. It will come off.
[0029]
[Means for Solving the Problems]
A first aspect of the present invention includes a fuel supply device that supplies injected fuel to an intake passage, and is a part of the fuel from the fuel supply device that adheres to an intake passage wall or an intake valve wall on the upstream side of a cylinder. In an air-fuel ratio control device for an engine with fuel wall flow correction related to a delay in supply to a cylinder, an intake valve operation stop mechanism capable of stopping the operation of the intake valve and the intake valve operation stop mechanism under cylinder stop conditions are used. The cylinder stop start means for starting the cylinder stop for at least one cylinder, the fuel attachment part temperature estimation means for estimating the fuel attachment part temperature during the cylinder stop for the cylinder in which the cylinder is stopped, and the cylinder stop condition are excluded. A fuel supply restarting means for releasing the cylinder stop of the cylinder that has been stopped until then, and restarting the fuel supply to the cylinder that has been stopped until then This resumption of the fuel supply and a fuel wall flow correction means for performing a fuel wall flow correction based on the estimated value Twf of the fuel attachment temperature in the cylinder is stopped against resumes cylinder fuel supply.
[0030]
【The invention's effect】
Consider one cylinder that stops the cylinder. In the state where the cylinder is not stopped in this cylinder, the temperature of the fuel adhering portion is substantially equal to the cooling water temperature. However, when the cylinder is stopped, no heat is transferred from the high-temperature combustion gas to the fuel adhering portion because combustion is not involved. When it disappears (only the heat of compression), the temperature of the fuel adhering portion decreases, and the actual amount of fuel flowing through the wall increases as the temperature decreases. According to the first aspect of the present invention, for the cylinder to be stopped, the temperature of the fuel adhering portion that decreases while the cylinder is stopped is estimated, and when the cylinder stop condition is subsequently removed, the cylinder is stopped until then. Since the fuel supply with the fuel wall flow correction based on the estimated fuel adhering portion temperature is resumed for the cylinder that has been stopped, the fuel supply from the cylinder stop to the cylinder that has been stopped is resumed. The fuel wall flow correction amount at the time becomes optimal, and accordingly, the air-fuel ratio at the time of resuming the fuel supply from the cylinder stop for the cylinder that has stopped the cylinder can be appropriately controlled to the target value.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes an engine body, and a fuel injection valve 4 for each cylinder is provided in the intake passage 2 downstream of the intake throttle valve 3, and a predetermined value is determined according to operating conditions by an injection signal from the engine controller 11. Fuel is injected and supplied toward the intake port 5 so that the air-fuel ratio is achieved. Specifically, a signal from a POS sensor (position sensor) 12, a PHASE sensor (phase sensor) 13, a signal of an intake air flow rate from an air flow meter 14, a signal of an engine cooling water temperature from a water temperature sensor 15, etc. are mainly from a microcomputer. The engine controller 11 calculates a basic injection pulse width Tp from which an air-fuel mixture having a basic air-fuel ratio (for example, theoretical air-fuel ratio) is obtained based on these, and performs various corrections such as an increase in water temperature. The fuel injection pulse width Ti is obtained, and the fuel injection valve 4 is opened for a period corresponding to Ti at a predetermined timing.
[0032]
Part of the fuel injected from the fuel injection valve 4 toward the intake port 5 of the intake valve 7 lying in the intake air so as to block the wall of the intake port 5 and the intake port 5 corresponding to the inlet to the cylinder. It adheres to the back of the umbrella and flows in a liquid state. Among these, the fuel flowing along the wall surface of the intake port 5 flows into the cylinder 6 as it is. Further, the fuel adhering to the back of the umbrella of the intake valve 7 flows in a liquid state through the back of the intake valve 7 and reaches the edge, and then drops from the edge and flows into the cylinder 6 while remaining in a liquid state. These so-called wall flow fuels are different from the fuel that floats in the intake air and flows into the cylinder 6 together with the intake air. However, in the steady state, the amount of wall flow fuel is somewhat different. Regardless of this, the air-fuel ratio is maintained at a constant value. Therefore, the fuel wall flow correction is not necessary in the steady state.
[0033]
However, at the time of acceleration / deceleration of the engine, the air-fuel ratio deviates from the target value (theoretical air-fuel ratio) temporarily due to the quantitative change of the wall flow fuel. For example, when considering acceleration when the accelerator pedal is depressed from a low load state, the amount of wall flow fuel is greater in the post-acceleration state (high load state) than in the low load state. For this reason, since the wall flow fuel is insufficient with respect to the equilibrium state after the acceleration in the early stage of acceleration, a part of the injected fuel is deprived by the increase of the wall flow fuel, and the fuel flowing into the cylinder 6 is insufficient. The fuel ratio is leaner than the target value. When the wall flow fuel settles to the equilibrium state amount after acceleration, the air-fuel ratio returns to the target value.
[0034]
In this case, the equilibrium state quantity of the wall flow fuel can be calculated from the temperature of the fuel adhering portion (mainly the intake valve 7 here), the engine load, and the rotational speed. It is empirically known to respond to a quantity with a first order lag. Also, the actual time constant of the response of the wall flow fuel can be calculated from the temperature of the fuel adhering portion, the engine load, and the rotational speed.
[0035]
Therefore, if the actual wall flow fuel can be estimated, the difference between the equilibrium state quantity and the actual wall flow fuel during acceleration is the shortage of the wall flow fuel quantity. Therefore, a value corresponding to this difference is given as the fuel wall flow correction amount. Do it.
[0036]
For this reason, the engine controller 11 has two values: an equilibrium adhesion amount Mfh for all cylinders representing the wall flow fuel amount in an equilibrium state, and a quantity ratio Kmf corresponding to the time constant of the actual wall flow fuel response. Is determined in advance based on the engine load, the engine speed N, and the cooling water temperature Tw, and the amount of equilibrium adhesion based on the engine load, the engine speed N, and the wall flow correction temperature Twf as the estimated temperature value of the fuel adhering portion. Mfh and the amount ratio Kmf are calculated, and using these and the attachment amount Mf for all cylinders that is a predictive variable at that time, the following equation (9) is used to calculate the attachment amount Mf for all cylinders per control cycle (for example, An adhesion speed Vmf representing a change amount from one injection to the next injection for each cylinder) is calculated, and this adhesion speed Vmf is calculated as a transient correction amount Katos per cylinder which is a fuel wall flow correction amount. Performing fuel wall flow correction by adding the above Tp Te.
[0037]
On the other hand, Vmf is a value that contributes to an increase in the amount of fuel flowing through the wall. Therefore, the deposition speed Vmf at the current injection is added to the deposition amount Mf for all the cylinders before the current injection in synchronization with the fuel injection for each cylinder. By doing so, the adhesion amount Mf for all cylinders is updated.
[0038]
Cut fuel by cylinder from the viewpoint of improving fuel efficiency. That is, the engine controller 11 starts the fuel cut from the fuel injection valve 4 for all of the cylinders (four cylinders) when the accelerator pedal is at the idle position or higher and the remaining amount thereafter. The fuel is cut from the fuel injection valve 4 for the two cylinders (at this time, all cylinders are cut). If the accelerator pedal is stepped on from this state, or if the rotation decreases and falls below the predetermined rotation speed (recovery rotation speed), the fuel cut is stopped for the two cylinders and the fuel supply is restarted. Stop cutting and restart fuel supply.
[0039]
At this time, in the cylinder where the fuel cut is performed, fuel that contributes to maintaining or increasing the wall flow fuel amount is not supplied by the fuel cut, while the wall flow fuel flows into the cylinder 6 together with the intake air. When the cut time elapses, the wall flow fuel for the cylinder where the fuel cut is performed decreases, and finally the wall flow fuel disappears. Therefore, in the engine controller 11, when the fuel cut is performed, when the fuel cut is in progress, the amount of adhesion Mfn for the cylinder in which the fuel cut is performed is gradually decreased to recover the fuel for the cylinder in which the fuel cut is performed. The fuel wall flow correction amount Kathos at the time (at the time of return from the fuel cut) is prevented from being insufficient.
[0040]
In order to further improve fuel consumption, an intake valve operation stop mechanism (not shown) that can stop the operation of the intake valve 7 is provided, and the engine controller 11 has a predetermined operating range such as a low load low rotational speed range. The intake valve operation stop mechanism is operated to stop the cylinder for at least one cylinder. When shifting from the low load low speed range to the high load time, the cylinder stop for the cylinder that is stopping the cylinder is released. The intake valve 7 is brought into operation again and the fuel supply from the fuel injection valve 4 is resumed.
[0041]
Here, the intake valve operation stop mechanism includes, for example, a mechanism in which the intake valve 7 itself is an electromagnetically driven valve, and a mechanism in which a cam driven valve that can stop the intake valve 7 is provided. Description is omitted.
[0042]
In the present invention, the cylinder is stopped for at least one of the cylinders, and the cylinder is stopped for the cylinder in which the cylinder is stopped on the premise of the engine that performs the air-fuel ratio control with the fuel wall flow correction as described above. When the fuel supply is restarted, the wall flow correction amount at the time of restarting the fuel supply from the cylinder stop of the cylinder that has stopped the cylinder is made not to be excessive or deficient as in the case of the fuel recovery from the fuel cut.
[0043]
The contents of this control executed by the engine controller 11 will be described according to the following flowchart.
[0044]
FIG. 2 is for calculating the wall flow correction temperature Twf, which is an estimated value of the fuel adhesion portion temperature, and is executed once every 1 sec, for example, by timer synchronization.
[0045]
Note that FIG. 2 shows the case where cylinders are not distinguished for simplicity, but when performing fuel cut by cylinder or cylinder stop by cylinder, cylinder discrimination is performed, and the flow of FIG. Need to run.
[0046]
In step 1, it is checked whether or not it is during firing. Here, the time of firing is a case other than the following five cases.
[0047]
A) At initialization,
B) When the starter switch is ON
C) When the engine is not running (when the engine is stalled, before starting)
D) When fuel is cut
E) When the cylinder stops
When it is not at the time of firing, it is determined that the case is one of the above-mentioned cases a) to o), and the process proceeds to Steps 2 and 3 and the signal from the ignition switch 17, the signal from the starter switch 18, Based on the signal of the engine rotational speed N detected by the above, it is determined whether it is in any one of the above a) to o).
[0048]
(C) When the engine is not rotating or (b) When the starter switch is turned on, the flow proceeds to step 5 and the current cooling water temperature Tw detected by the water temperature sensor 15 is searched to search the table having the contents shown in FIG. The initial value Inwft of the temperature is calculated. As shown in FIG. 3, the initial temperature value Inwft is a value that increases as the cooling water temperature Tw increases.
[0049]
In step 6, using this wall flow correction temperature initial value Inwft,
Twf = Inwft × ENSTPSP #
+ Twf _-1sec × (1-ENSTPS #) (1)
However, ENSTSP #: weighted average coefficient when the engine is not rotating (constant value),
Twf _-1sec Twf before 1 sec,
The wall flow correction temperature Twf is calculated by the following formula, and the flow of FIG.
[0050]
Twf in the equation (1) is a value that converges toward the initial value Inwft with a first-order lag.
[0051]
On the other hand, when the engine is rotating and the starter switch is not ON, it is determined that the engine is in any one of the above (e) or (e), and it is determined in step 4 whether the cylinder stop condition is satisfied. The cylinder stop condition is a case where all of the following conditions are satisfied, for example.
[0052]
(A) The operating point determined from the engine load and the rotational speed is in the cylinder stop operating range. For example, a predetermined low load low rotation range is determined in advance as the cylinder stop operation range.
[0053]
(B) The accelerator pedal is not depressed.
[0054]
Accordingly, when either of the conditions (a) and (b) is not satisfied, it is determined that the fuel is being cut, and the process proceeds to steps 7 and 8.
Twf = (Inwft + OFST1) × FCTSP1 #
+ Twf _-1sec × (1-FCTSP1 #) (2)
Where OFST1: second offset amount (positive constant value),
FCTSP1 #: Weighted average coefficient at fuel cut (constant value),
Twf _-1sec Twf before 1 sec,
When the wall flow correction temperature Twf is satisfied and all of (a) and (b) are satisfied (when the cylinder stop condition is satisfied), the process proceeds to steps 9 and 10;
Twf = (Inwft + OFST2) × FCTSP2 #
+ Twf _-1sec × (1-FCTSP2 #) (3)
However, OFST2: First offset amount (positive constant value)
FCTSP2 #: Weighted average coefficient when the cylinder is stopped (constant value),
Twf _-1sec Twf before 1 sec,
The wall flow correction temperature Twf is calculated by the following formula, and the flow of FIG.
[0055]
The operations in steps 7 and 9 are the same as those in step 5. That is, the initial value Inwft of the wall flow correction temperature is calculated by searching a table having the contents shown in FIG. 3 from the current cooling water temperature Tw detected by the water temperature sensor 15 in steps 7 and 9.
[0056]
In FIG. 3, since the one-dot chain line is a line of Inwft = Tw, the initial value Inwft corresponding to the cooling water temperature Tw is always lower than the cooling water temperature Tw at that time. Further, Twf is equal to Tw at the time of firing after completion of warming up of the engine.
Further, in the cylinder where the fuel cut is performed, the fuel adhering portion temperature of the cylinder where the fuel cut is performed decreases due to the fuel cut, and settles to the equilibrium state temperature after the fuel cut continues for a long time. The target value (Inwft + OFST1) on the right side of the equation (2) is the equilibrium temperature of the fuel adhering portion for the cylinder where the fuel cut is performed after the fuel cut continues for a long time. That is, when fuel is mainly injected into the intake valve 7, the fuel adheres to the back of the umbrella of the intake valve 7, so that the fuel attachment portion is the intake valve 7, and the fuel cut-off cylinder is long. After the cut continues, the equilibrium temperature of the intake valve 7 for the cylinder where the fuel cut is performed settles to a value lower than the cooling water temperature Tw by a certain value. Therefore, a value obtained by adding the offset amount OFST1 to the initial value Inwft corresponding to the cooling water temperature Tw is set as a target value at the time of fuel cutting for the cylinder where the fuel cut is performed, and this target value is lower than the cooling water temperature at the start of the fuel cut. It is trying to become. Therefore, Twf in the equation (2) is the same in that the fuel supply is stopped from the cooling water temperature Tw at the start of fuel cut toward the target value (Inwft + OFST1) lower than the Tw, and also when the cylinder is stopped. Therefore, Twf in equation (3) is also a value that converges with a first-order lag from the cooling water temperature Tw at the start of cylinder stop toward the target value (Inwft + OFST2) lower than Tw.
[0057]
Here, the target value (Inwft + OFST1) of the equation (2) is the second target value in the invention described in claim 3, and the target value (Inwft + OFST2) in (3) is the second target value described in the inventions of claims 2 and 3. 1 target value.
[0058]
However, the first offset amount OFST2 on the right side of the equation (3) is set larger than the second offset amount OFST1 on the right side of the equation (2) (invention according to claim 3). This is because the fuel adhering portion temperature is less likely to decrease by the amount of the intake air flow rate when there is no intake air flow rate when there is no intake air flow rate when the cylinder is stopped, and the equilibrium state temperature of the intake valve 7 after the cylinder stop continues for a long time. This is because it seems to be higher than the equilibrium state temperature of the intake valve 7 after the fuel cut continues for a long time. Finally, the offset amount OFST2 is determined by matching.
[0059]
On the other hand, when it is determined in step 1 that it is during firing, the process proceeds to steps 11 and 12, and a weighted average coefficient Fltsp during firing is obtained from the intake air flow rate Q with reference to a table having the contents shown in FIG. Using the cooling water temperature Tw, the wall flow correction temperature Twf at the time of firing,
Twf = Tw × Fltsp + Twf _-1sec × (1-Fltsp) (4)
Twf _-1sec Twf before 1 sec,
The flow of FIG.
[0060]
In FIG. 4, the value of the weighted average coefficient Fltsp is increased as the intake air flow rate Qa is increased. The larger the Qa, the greater the heat generated in combustion per unit time and the higher the speed of heat transfer to the fuel adhering portion. Because it becomes.
[0061]
FIG. 5 is for initialization (initialization of the wall flow correction temperature), and is executed only once when the ignition switch 17 is switched from OFF to ON.
[0062]
In step 21, the initial value Inwft of the wall flow correction temperature similar to that when the starter switch is turned on or when the engine is not rotating is searched by searching a table having the contents shown in FIG. 3 from the current cooling water temperature Tw detected by the water temperature sensor 15. In Step 22, this Inwft is put in Twf.
[0063]
Since the initial value Inwft is lower than the cooling water temperature Tw, Twf immediately after starting becomes a value that starts from the initial value Inwft and converges to the cooling water temperature Tw with a first-order delay. When the engine warm-up is completed, Twf matches Tw.
[0064]
Next, a method for calculating the fuel wall flow correction amount using the wall flow correction temperature Twf calculated in this way will be described with reference to the following flowchart.
[0065]
Various apparatuses have been proposed for the calculation method of the fuel wall flow correction amount. Here, a case where the present invention is applied to the technique disclosed in Japanese Patent Laid-Open No. 10-259748 will be described.
[0066]
The technique disclosed in Japanese Patent Laid-Open No. 10-259748 allows an operation with an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a predetermined operation region where a large output is not required, and an operation that requires a large output, such as at high loads. In the range, the operation is switched to the stoichiometric air-fuel ratio, and the transient correction amount Katos per cylinder for the low frequency component and the step-by-step cylinder-specific wall flow correction amount Chosn for the high frequency component. ¹ And calculating. Here, the wall flow fuel has a low frequency component that responds relatively slowly and a high frequency component that responds relatively quickly, and the wall flow correction amount for the low frequency component is Kathos, whereas the wall flow correction for the high frequency component is Quantity Chosn ¹ It is. However, the present invention is not limited to the one that calculates these two correction amounts together.
[0067]
FIG. 6 shows the control operation for calculating and outputting the fuel injection pulse width for each cylinder. First, at step 31, the target equivalent ratio Tfbya is calculated.
[0068]
Here, Tfbya is 1.0 when operating at the stoichiometric air-fuel ratio, and is smaller than 1.0 when operating at an air-fuel ratio leaner than the stoichiometric air-fuel ratio. The air-fuel ratio is switched by this Tfbya. Done. In addition, the Tfbya also has a function of correcting the water temperature for warming up the engine.
[0069]
In step 32, the output of the air flow meter 14 is A / D converted and linearized to calculate the intake air flow rate Q. In step 33, from this intake air flow rate Q and the engine speed N detected by the crank angle sensors 12 and 13, the basic injection pulse width Tp at which a theoretical air-fuel ratio is obtained is obtained as Tp = K × Q / N. . K is a constant.
[0070]
In step 34, for this basic injection pulse width Tp,
Avtp = Tp × Fload + Avtp _-1 × (1-Fload) (5)
Where Fload: weighted average coefficient,
Avtp _-1 : Last Avtp,
The injection valve part air amount equivalent pulse width Avtp is obtained by the following formula. The weighted average coefficient Fload of the equation (5) is obtained by searching a predetermined map from the product N · V of the rotational speed N and the cylinder volume V and the total flow passage area Aa of the intake pipe.
[0071]
In step 35, a transient correction amount Kathos per cylinder is calculated. The calculation of the transient correction amount Kathos will be described with reference to FIG. 7 (subroutine of step 35 in FIG. 6).
[0072]
Since the calculation of the transient correction amount Kathos is performed without distinguishing each cylinder, the transient correction amount Katos, the adhesion speed Vmf, the adhesion will be specifically described in the case of a four-cylinder engine MPI (multipoint injection) and sequential injection. The amount Mf is a value for each cycle (for each input of the 1Ref signal). In contrast, Chosn ¹ Since this is a value for each cylinder, it is a value for each cycle of each cylinder (each time a 4Ref signal is input). Mfh and Mf are values for all cylinders.
[0073]
First, in step 51, the injection valve portion air amount equivalent pulse width Avtp and the target equivalent ratio Tfbya (obtained in steps 31 and 34 in FIG. 6) are read.
Mfh = Avtp × Mfhtvo × Tfbya × CYLNDR # (6)
Where Mfhtvo: adhesion magnification,
CYLNDR #: Number of cylinders (= 4),
The equilibrium adhesion amount Mfh in all cylinders is calculated by the following formula (see Mfh for all cylinders on the upper right side in FIG. 18).
[0074]
Data for obtaining the adhesion magnification Mfhtvo of equation (6) (reference adhesion magnification load term Mfhq described later) _i Map data and reference adhesion magnification rotation term Mfhn _i Table data) is matching data for the target equivalent ratio Tfbya = 1.0. Therefore, even if the equilibrium adhesion amount obtained using this matching data is appropriate for Tfbya = 1.0, the target fuel When the air ratio equivalent amount Tfbya is a value other than 1.0, an error occurs in the calculation of the equilibrium adhesion amount Mfh by the difference, and as shown in FIG. 8, the equilibrium adhesion amount Mfh is substantially proportional to Tfbya. Therefore, as shown in the equation (6), by multiplying the value for Tfbya = 1.0 (Avtp × Mfhtvo × CYLNDR #) by Tfbya, the equilibrium adhesion amount Mfh without excess or deficiency corresponding to Tfbya at that time Is given. As a result, when the target equivalent ratio Tfbya becomes 1.2 at the time of high load after the engine warm-up is completed, the equilibrium adhesion amount Mfh at this time is multiplied by 1.2, and the target equivalent ratio Tfbya is 0.1 in the lean operation region. When it reaches 66, the equilibrium adhesion amount Mfh at this time is multiplied by 0.66.
[0075]
The adhesion magnification Mfhtvo in equation (6) is obtained in the same manner as in the past (see Japanese Patent Laid-Open No. 3-111642). Mfhtvo is an equilibrium deposit amount per unit injection valve portion flow rate equivalent pulse width and per cylinder, and this is an estimated value of load (Avtp), rotation speed N, and fuel adhesion portion temperature. Obtained using Twf. This calculation of Twf has been described above with reference to FIG.
[0076]
Specifically, the reference temperature Twf above and below the wall flow correction temperature Twf _i And Twf _{i + 1} Reference adhesion magnification data Mfhtwf for (i is an integer from 1 to 4 (or 5)) _i And Mfhtwf _{i + 1} Twf, Twf _i , Twf _{i + 1} Obtained by interpolation calculation using. For example, Mfhtwf ₁ , Mfhtwf ₂ And the reference temperature Twf ₁ , Twf ₂ Using current temperature Twf
Mfhtvo = Mfhtwf ₁ + (Mfhtwf ₂ -Mfhtwf ₁ )
× (Twf ₁ -Twf) / (Twf ₁ -Twf ₂ ) ... (7)
Mfhtvo is calculated by the following formula (linear interpolation calculation formula).
[0077]
The reference adhesion magnification data Mfhtwf _i Is
Mfhtwf _i = Mfhq _i × Mfhn _i (8)
However, Mfhq _i : Reference adhesion magnification load term,
Mfhn _i : Reference adhesion magnification rotation term,
Calculate with the following formula.
[0078]
Where Mfhq _i Is obtained by searching a predetermined map with interpolation calculation using the α-N flow rate Qh0 and the wall flow correction temperature Twf. Qh0 is an air flow rate of the throttle valve portion obtained from the throttle valve opening TVO and the rotational speed N and is already known. Mfhn _i Is obtained by searching a predetermined table from the rotational speed N with interpolation calculation. Mfhq _i Map (see Figure 9) and Mfhn _i The table (see FIG. 10) stores data matched at the stoichiometric air-fuel ratio, together with a Kmfat map and a Kmfn table, which will be described later. Each map in FIG. 9 and FIG. 11 described later is originally matched with the cooling water temperature Tw, but when searching this map, the wall flow correction temperature Twf is used instead of the cooling water temperature Tw. That is why.
[0079]
With respect to the equilibrium adhesion amount Mfh for all the cylinders obtained in this way, the adhesion amount (prediction variable) Mf for all the cylinders at the present time (see Mf for all the cylinders on the upper right side in FIG. 18) per unit cycle ( In the case of the 4-cylinder engine MPI and sequential injection, the coefficient (that is, the quantity ratio) Kmf representing the ratio of how close to each half-rotation of the crankshaft is corrected, and in step 53, the basic quantity ratio Kmfat and the quantity rate rotation correction. It calculates from the product of the rate Kmfn.
[0080]
Here, Kmfat is obtained using the wall flow correction temperature Twf. For example, a predetermined map (see FIG. 11) is searched with interpolation calculation using the α-N flow rate Qh0 and the wall flow correction temperature Twf. Kmfn searches a predetermined table (see FIG. 12) from the rotational speed N with interpolation calculation.
[0081]
Reference adhesion magnification rotation term Mfhn _i N attached to the quantity ratio rotation correction factor Kmfn is confusing but does not mean n (described later) as a cylinder number, but means the rotation speed N.
[0082]
Incidentally, since the operating conditions are not divided in FIG. 7, the flow of FIG. 7 is executed at regular intervals even when the cylinder is stopped. For this reason, for a cylinder that stops the cylinder, Twf, which is an estimated value of the temperature of the fuel adhering portion while the cylinder is stopped, is reduced, but is calculated so that the equilibrium adhesion amount Mfh increases as the temperature decreases. Similarly, the fraction ratio Kmf is calculated so that the response of the wall flow fuel becomes slower as Twf, which is an estimated value of the temperature of the fuel adhering portion during cylinder stoppage, decreases for the cylinder that performs cylinder stoppage.
[0083]
In this way, the quantity ratio Kmf thus obtained is multiplied by the difference between Mfh and the adhesion quantity Mf for all cylinders at the present time in step 54, that is,
Vmf = (Mfh−Mf) × Kmf (9)
The adhesion speed Vmf representing the amount of change per one control cycle (for example, from one injection to the next injection for each cylinder) of the adhesion amount Mf for all the cylinders is calculated by the following equation.
[0084]
Mf is a predictive variable for the adhesion amount of all cylinders at that time, and therefore the adhesion amount of (Mfh−Mf) indicates the excess / deficiency amount from the equilibrium adhesion amount in the current cycle, and this value (Mfh−Mf) is Further correction is made with the dose ratio Kmf.
[0085]
After obtaining the adhesion speed Vmf in this way, in step 55, after calculating the deceleration correction rate Ghf, in step 55,
Kathos = Vmf × Ghf (10)
The transient correction amount Kathos per cylinder is calculated by the following equation. Here, the deceleration correction rate Ghf is a value necessary only during deceleration (a value exceeding 1.0), and is 1.0 during acceleration. Therefore, it is not necessary to consider the deceleration correction rate Ghf when resuming fuel supply after canceling the fuel cut or cylinder stop (Ghf = 1.0).
[0086]
When the calculation of the transient correction amount Katos per cylinder is completed in this way, the process returns to FIG.
Tin = (Avtp × Tfbya + Kathos) × α × 2 + Ts
+ Chosn ¹ ... (11)
Where α: air-fuel ratio feedback correction coefficient,
Ts: Invalid injection pulse width,
Chosn ¹ : The fuel injection pulse width Tin given to the fuel injection valve 4 is calculated for each cylinder by the equation of the cylinder-by-cylinder wall flow correction amount in the first step change cycle.
[0087]
The air-fuel ratio feedback correction coefficient α in the equation (11) is O so that the control air-fuel ratio falls within a so-called window centered on the stoichiometric air-fuel ratio. ₂ The value calculated based on the output of the sensor 16 and the invalid injection pulse width Ts is a value for compensating for the operation delay from when the fuel injection valve 4 receives the injection signal until it actually opens.
[0088]
Further, since the expression (11) is an expression in the case of sequential injection (in the case of four cylinders, injection is performed once every two engine revolutions in accordance with the ignition order of each cylinder), the number 2 is entered.
[0089]
Cylinder wall flow correction amount Chosn in the first cycle of step change ¹ Will be described later. Since this is a value for each cylinder (that is, n represents a cylinder number), Ti must also be a value for each cylinder.
[0090]
Next, in step 37, fuel cut is determined. In steps 39 and 40, if the fuel cut condition is satisfied, the invalid injection pulse width Ts is stored in the output register. Otherwise, Tin is stored in the output register. Prepare for injection at a predetermined injection timing according to the output.
[0091]
FIG. 13 shows the cylinder-specific wall flow correction amount Chosn in the first step change cycle. ¹ Is executed every 10 ms.
[0092]
Here, Chosn ¹ Is calculated by the equation (14) described later, and 1 / A of the equation (14) (where A is the response gain of the first cycle of the low frequency component) is calculated using the equations (13a) and (13b). However, the derivation of these equations is described in detail in JP-A-10-259748. Since the present invention is not directly related to these derivations, description thereof is omitted.
[0093]
In step 61, the cooling water temperature Tw detected by the water temperature sensor 15 is read. Chosn ¹ In addition to Tw, the adhesion magnification Mfhtvo, the amount ratio Kmf, the transient correction amounts Kathos, Kathos are calculated. _-4Ref Of these, Mfhtvo, Kmf, and Kathos are obtained by the flow of FIG. Kathos _-4Ref Is obtained by shifting the value of Kathos at the injection timing, as shown in step 87 of FIG.
[0094]
In step 62 of FIG.
ΔKathos = Kathos-Kathos _-4Ref (12)
However, Kathos _-4Ref : 1 cycle before each cylinder (before 4Ref signal)
Kathos,
ΔKathos, which is the amount of change in Kathos from the previous injection, is calculated by the following equation, and ΔKathos is compared with zero.
[0095]
If ΔKathos> 0 (acceleration), the routine proceeds to step 63, where an increase gain Gztwp is calculated, and this Gztwp is entered into the water temperature correction gain Gztwc at step 64. Similarly, when ΔKathos <0 (during deceleration), the routine proceeds to step 65 where the reduction gain Gztwm is calculated, and this Gztwm is entered into Gztwc at step 66. The gains Gztwp and Gztwm are for correcting the water temperature, and are calculated by searching the tables having the contents shown in FIGS. 14 and 15 with interpolation calculation using the cooling water temperature Tw.
[0096]
In step 67, the adhesion magnification Mfhtvo and the quantity ratio Kmf are read, and using these values, the value of A / (1-A) is
A / (1-A) = Mfhtvo × Kmf (13a)
Where A: response gain of the first cycle of the low frequency component,
And the value of A / (1-A) is calculated in step 68.
1 / A = 1 / {A / (1-A)} + 1 (13b)
The value of 1 / A on the left side of the equation (13b) is calculated by substituting it into the right side of the equation
[0097]
In step 69, it is checked if the fuel is being cut. Here, unlike steps 37 and 38 in FIG. 6, only the fuel supply by the fuel injection valve 4 is stopped (that is, whether Ts is output to the output register).
[0098]
If fuel cut is not in progress, go to step 70 and Kathos _-4Ref (Obtained in step 87 of FIG. 16) _-4Ref , 1 / A, Gztwc and Kathos (obtained in step 56 of FIG. 7),
Chosn ¹ = (Kathos-Kathos _-4Ref )
× (Gztwc-1) / A (14)
However, Kathos _-4Ref : 1 cycle before each cylinder (before 4Ref signal)
Kathos,
The cylinder-by-cylinder wall flow correction amount Chosn in the first cycle of step change ¹ Calculate
[0099]
On the other hand, when the fuel is being cut, the routine proceeds from step 69 to step 71, where it is further checked whether the cylinder is stopped. When the cylinder is not stopped, the routine proceeds to step 72 where Mfn (obtained at step 93 in FIG. 16), Mf (obtained at step 89 in FIG. 16), and Kmf (obtained at step 53 in FIG. 7). To calculate the value of (Mf−Mfn) × Kmf and use this to calculate Kathos _-4Ref In step 74, Chosn ¹ Calculate That is, Chosn during fuel cut (except when cylinder is stopped) ¹ But,
Chosn ¹ = {Kathos- (Mf-Mfn) × Kmf}
× (Gztwc-1) / A (15)
This Chosn is calculated by the formula ¹ Becomes the value at the time of resumption of fuel supply immediately after canceling the fuel cut.
[0100]
Similarly, when the cylinder is stopped, the routine proceeds from step 71 to step 73, where Mfn (obtained at step 97 in FIG. 16), Mf (obtained at step 89 in FIG. 16), Kmf (step in FIG. 7). 53) to calculate the value of (Mf−Mfn) × Kmf. _-4Ref In step 74, Chosn ¹ Calculate That is, Chosn while the cylinder is stopped ¹ But,
Chosn ¹ = {Kathos- (Mf-Mfn) × Kmf}
× (Gztwc-1) / A (16)
This Chosn is calculated by the formula ¹ Becomes the value of resumption of fuel supply immediately after the cylinder stop is released.
[0101]
In step 75, it is determined whether or not all cylinders have been completed. If not, the process returns to step 62 and repeats up to step 74. Chosn ¹ The time required for the calculation for all cylinders is sufficiently shorter than the calculation interval of 10 ms in FIG. 13, and there is a situation in which the next 10 ms calculation timing comes before the calculation for all cylinders is completed. Absent.
[0102]
FIG. 16 is for obtaining required values such as Mf for all the cylinders in synchronization with the injection timing (specifically, in synchronization with the Ref signal of each cylinder). Note that the injection timing and the input timing of the Ref signal for each cylinder do not necessarily coincide with each other, but for the convenience of explanation, the timing is set for each input of the Ref signal for each cylinder.
[0103]
In FIG. 16, in step 81, cylinder discrimination is performed based on signals from the crank angle sensors 12, 13, and it is further checked in step 82 whether the determined cylinder is under fuel cut. Also here, unlike steps 37 and 38 of FIG. 6, only the fuel supply by the fuel injection valve 4 is stopped (that is, whether Ts is output to the output register).
[0104]
An example of the fuel cut for each cylinder is a case as shown in FIG. In the same figure, when the fuel cut condition is satisfied, the fuel is cut from the cylinders that come immediately after the fuel cut condition is satisfied for some cylinders (No. 1 cylinder and No. 4 cylinder), and after a predetermined period, all cylinders are fuel cut. (On the contrary, when the fuel recovery condition is satisfied, fuel recovery is performed for the No. 2 cylinder and the No. 3 cylinder from the cylinder that comes immediately after the fuel recovery condition is satisfied, and all cylinders are recovered after a predetermined period of time). In this way, the fuel cut for each cylinder is generated in the middle of the fuel cut.
[0105]
If the fuel is not being cut, after the injection by the fuel injection valve 4 of the cylinder determined in step 83 is executed, all the fuel used in the next processing is used in step 84 using the adhesion velocity Vmf obtained by the above equation (9). The amount of adhesion Mf for the cylinder is
Mf = Mf _-1Ref + Vmf (17)
However, Mf _-1Ref : Mf before injection (1 cycle before)
(See Mf for all cylinders on the upper right side of FIG. 18), and this Mf is processed in step 85 for the next processing. _-1Ref Move to.
[0106]
(17) Mf on the right side of the equation _-1Ref Is the amount of adhesion for all cylinders at the end of the previous injection (before the engine half-rotation in the case of 4-cylinder engine MPI and sequential injection), and the value obtained by adding the adhesion speed Vmf applied at the time of this injection to this It becomes the adhesion amount Mf (Mf on the left side) for all the cylinders at the end point. The value of the adhesion amount Mf is used in the next calculation of Vmf. Mf on the right side of equation (17) _-1Ref Is the value immediately before the calculation of the adhesion speed Vmf, whereas Mf on the left side of the equation (17) is the value immediately after the calculation of the adhesion speed Vmf. Therefore, in terms of content, the value of Mf in equation (9) is set to Mf on the right side of equation (17). _-1Ref And Mf on the left side of equation (17) is calculated. The reason why the adhesion amount appears on the left side and the right side in the equation (17) is that the adhesion amount is cyclically updated at each injection timing without distinguishing each cylinder.
[0107]
The left side of FIG. 18 shows the step response of Mfh and Mf by cylinder, the upper right side of FIG. 18 shows the step response of Mfh and Mf when all cylinders are combined, and the lower right side of FIG. 18 shows the change in Kathos by cylinder. Respectively.
[0108]
In step 86 Chosn ¹ Put 0 in This is Chosn ¹ This is a value that is added only once at the time of the first injection when fuel supply is restarted after a fuel cut or cylinder stop, so that it is not given at the time of the second injection.
[0109]
In step 87, the value of Kathos is shifted for the next processing (memory Kathos). _-3Ref Value of memory Kathos _-4Ref In memory Kathos _-2Ref Value of memory Kathos _-3Ref In memory Kathos _-1Ref- Value of memory Kathos _-2Ref The value of Kathos is stored in the memory Kathos. _-1Ref ).
[0110]
In step 88, the value of Mf is set to Mfn of the cylinder that is at the injection timing at that time. _-4Ref Move to. Mfn is the adhesion amount for each cylinder during fuel cut, and Mf immediately before fuel cut is the initial value of Mfn (Mfn _-4Ref ), Step 88 is required. For example, during fuel injection, the Mfn of all cylinders _-4Ref Mf are sequentially stored.
[0111]
On the other hand, if the fuel cut is in progress, the process proceeds from step 82 to step 89 and thereafter. After performing the operations of steps 89, 90 and 91 in the same manner as when the fuel is not being cut, it is checked in step 92 whether the cylinder is stopped. When the cylinder is not stopped (during fuel cut), in step 93 as in the prior art.
Mfn = Mfn _-4Ref × FCKMF # ... (19)
Where, Mfn: the amount of adhesion by cylinder during fuel cut,
Mfn _-4Ref : Mfn one cycle before each cylinder (before 4Ref signal)
FCKMF #: Weight loss rate,
The amount of adhesion that is reduced during fuel cut is calculated for each cylinder by the following equation. That is, Mfn is the initial value (Mfn _-4Ref ) To every cylinder injection timing (every 4Ref signal) (see FIGS. 19 and 20). However, even if Mfn decreases, it does not become a negative value. Therefore, Mfn is compared with zero at step 94, and when Mfn is a negative value, Mfn is limited to zero at step 95.
[0112]
In step 96, the value of Mfn is stored in the memory Mfn for the next calculation. _-4Ref The calculation at the current injection timing is terminated.
[0113]
On the other hand, when the cylinder is stopped, the routine proceeds from step 92 to step 97, where Mf when the cylinder stop condition is satisfied is held as Mfn. This is due to the following reason. That is, in the cylinder where the fuel cut is performed, the wall flow fuel is urged by the intake air flow and flows into the cylinder 6 in order to keep the intake valve 7 in an operating state. It is necessary to reduce a certain Mfn as shown in the equation (19) during fuel cut. However, in the cylinder where the cylinder is stopped, all the intake valves 7 are fixed at the fully closed position, so that the wall flow fuel amount at the start of the cylinder stop remains on the upstream side of the intake valves 7 without further decrease. . Therefore, for the cylinder where the cylinder is stopped, the Mfn, which is the amount of adhesion for each cylinder, is reduced by the equation (19) as in the cylinder where the fuel cut is performed while the intake valve 7 is kept operating. Chosn to be given to the cylinder where the cylinder is stopped when the fuel supply is resumed after the cylinder is stopped ¹ Becomes excessive, and the air-fuel ratio at the time of resumption of fuel supply from the cylinder stop tends to be richer than the target value. Therefore, in the cylinder where the cylinder is stopped, Mf at the time when the cylinder stop is established corresponding to the wall flow fuel state of the cylinder is held as Mfn.
[0114]
Here, the operation of the present embodiment will be described with reference to FIGS.
[0115]
Now No. Consider one cylinder as a cylinder that performs fuel cut. FIG. 21 shows a model in which the fuel cut is started at the timing t1 and the fuel cut is stopped and the fuel supply is restarted because the accelerator pedal is depressed at the timing t2. That is, when the fuel is cut, In one cylinder, there is no combustion, so there is no heat transfer from the high-temperature combustion gas to the fuel adhering part (No. 1 cylinder intake valve) (compression heat only), and the temperature of the fuel adhering part increases as the fuel cut time elapses. It gradually decreases from t1. In this case, paying attention to the fact that the equilibrium state temperature of the fuel adhering portion after the fuel cut continues for a long time is lower than the cooling water temperature Tw, a value obtained by adding the offset amount OFST1 to the initial value Inwft according to the cooling water temperature Tw. Is set as a target value (Inwft + OFST1), this target value is set lower than the cooling water temperature Tw at the start of the fuel cut, and Twf, which is an estimated value of the fuel adhering portion temperature, converges to this target value. 2) Estimated by equation. Therefore, Twf, which is an estimated value of the fuel adhering portion temperature, decreases with a first order lag according to the weighted average coefficient from t1.
[0116]
Since the fuel cut is stopped at the timing t2 and the fuel supply is resumed, the fuel wall flow correction amount (transient correction amount Katos per cylinder and the cylinder in the first step change cycle) based on Twf at the timing t2. Separate wall flow correction amount Chosn ¹ ) And the fuel wall flow correction amounts Kathos and Chosn with respect to the steady fuel injection pulse width Avtp from the timing t2. ¹ The amount of fuel corresponding to the value obtained by adding is supplied from the injection valve 4. In this case, the transient correction amount Kathos per cylinder increases stepwise from the timing of t2, then gradually decreases and finally becomes zero (because the value gradually decreases is the value for the low frequency component). ), Chosn ¹ Is added only at the first injection timing immediately after the timing of t2.
[0117]
These fuel wall flow correction amounts Kathos, Chosn ¹ The amount of fuel supplied corresponding to is deprived as a fuel wall flow, and the fuel supply is resumed by supplying extra fuel that is deprived as this fuel wall flow when resuming fuel supply from cylinder stoppage. Even immediately after the timing t2, the air-fuel ratio of the cylinder that has been stopped can be kept in the vicinity of the theoretical air-fuel ratio.
[0118]
On the other hand, the same No. When cylinder stop is performed for one cylinder, No. By fixing the intake valve of one cylinder to the fully closed position, the intake is no. No intake flow rate is almost eliminated because it is not introduced into the cylinder of 1 cylinder. The fuel adhering part temperature of one cylinder is different from the fuel adhering part temperature at the time of fuel cut. That is, no. When the cylinder is stopped in one cylinder, the fuel adhering portion is not cooled by the intake air flow rate, and the latent heat of vaporization lost when the wall flow evaporates by the intake air flow rate is reduced. It is considered that the temperature of the fuel adhering portion becomes higher than that at the time of fuel cut.
[0119]
For this reason, no. Even when the cylinder is stopped for one cylinder, the fuel adhesion portion temperature from the cylinder stop is estimated in the same manner as when the fuel cut is performed. As shown by the solid line in the middle stage of FIG. Twf, which is an estimated value, is too low. Therefore, when returning at the time of firing at t4 in FIG. 22, the fuel wall flow correction amount (Kathos and Chosn) based on Twf at t4. ¹ ), The fuel wall flow correction amount increases by the amount estimated to be lower than the actual temperature of the fuel adhering portion (see the solid line in the lower part of FIG. 22), and the air-fuel ratio immediately after resumption of fuel supply from t4 leans to the rich side. End up.
[0120]
On the other hand, in the present embodiment (the invention described in claim 3), there is no intake air flow velocity when the cylinder is stopped, and the fuel adhesion portion temperature is less likely to be lower than when the fuel is cut. In response to the fact that the equilibrium state temperature of the intake valve 7 is likely to be higher than the equilibrium state temperature of the intake valve 7 after the fuel cut has been continued for a long time, the first offset amount OFST2 used when the cylinder is stopped is set at the time of the fuel cut. The fuel adhering portion temperature from t3, which is the cylinder stop timing, is estimated with a target value (Inwft + OFST2) obtained by setting the offset amount OFST2 to be larger than the second offset amount OFST1 to be used and adding the offset amount OFST2 to the initial value Inwft according to the water temperature Tw. As a result, the temperature drop of Twf, which is an estimated value of the fuel adhering portion temperature, becomes more gradual than when the fuel is cut, and when the cylinder is stopped It can have, had to be optimally trace the actual fuel attachment temperature (see the broken line in the middle Figure 22). Therefore, when returning at the time of firing at t4 in FIG. 22, the fuel wall flow correction amount (Kathos and Chosn) based on Twf at t4. ¹ ), The fuel wall flow correction amount is smaller than that at the time of fuel cut by the amount that the fuel adhering portion temperature approaches the actual value (see the broken line in the lower part of FIG. 22), and the air-fuel ratio immediately after the restart of fuel supply from t4 Can be converged to near the theoretical air-fuel ratio.
[0121]
Further, according to the present embodiment (the invention according to claim 9), the equilibrium state quantity of the wall flow fuel quantity decreases as the Twf, which is the estimated value of the fuel adhering part temperature during the cylinder stoppage, decreases for the cylinder that performs the cylinder stoppage. Therefore, the equilibrium adhesion amount Mfh corresponding to the temperature of the fuel adhesion part while the cylinder is stopped can be obtained with high accuracy.
[0122]
According to this embodiment (the invention according to claim 9), the response of wall flow fuel becomes slower as Twf, which is an estimated value of the temperature of the fuel adhering portion during cylinder stoppage, decreases for the cylinder that performs cylinder stoppage. Since the quantity ratio Kmf is calculated, the quantity ratio KMF corresponding to the temperature of the fuel adhering portion while the cylinder is stopped can be obtained with high accuracy.
[0123]
In the cylinder in which the cylinder is stopped, all the intake valves 7 are fixed at the fully closed position, so that the wall flow fuel amount at the start of the cylinder stop remains without being reduced. Accordingly, in the cylinder in which the cylinder is stopped, the amount of adhesion Mfn during the cylinder stop is reduced for the cylinder in which the cylinder is stopped, in the same manner as the cylinder in which the fuel cut is performed while the intake valve 7 is kept operating. The cylinder-by-cylinder wall flow correction amount Chosn for the first cycle of the step change to be applied to the cylinder where the cylinder is stopped when the fuel supply is resumed from the cylinder stop. ¹ In this embodiment (Claim 10), the air-fuel ratio at the time of resumption of fuel supply from the cylinder stop is deviated from the target value and leans to the rich side. According to the invention described in (1), in the cylinder where the cylinder is stopped, during the cylinder stop, the adhesion amount Mf for all the cylinders at the start of the cylinder stop is held as the adhesion amount Mfn for the cylinder where the cylinder is stopped. (Refer to Step 97 in FIG. 16) Cylinder wall flow correction amount Chosn for the first cycle of step change given when resuming fuel supply after cylinder stop for a cylinder in which cylinder stop is performed ¹ Is given in accordance with the actual fuel wall flow state, and the cylinder wall flow correction amount Chosn for the first cycle of the step change also when the fuel supply is resumed from the cylinder stop for the cylinder in which the cylinder is stopped. ¹ Can be calculated with high accuracy.
[0124]
In the embodiment, the case where the wall flow correction temperature Twf when the cylinder is stopped is calculated by the discrete value system as shown in the above equation (3), but the present invention is not limited to this, and Japanese Patent Laid-Open No. 8-177556 discloses. As described, it may be calculated in a continuous value system. An expression expressing the above expression (3) in a continuous value system is shown below.
[0125]
Twf = Twf initial value− {Twf initial value− (Inwft + OFST2)}
X {1-exp (-t / T)} (20)
However, Twf initial value: cooling water temperature at the start of cylinder stop,
t: time,
T: Time constant of response of wall flow fuel with low frequency component,
Here, “exp” on the right side of the equation (20) represents the exponent e, and the value (−t / T) immediately to the right of “exp” is a value on the right shoulder of the exponent e.
[0126]
In the embodiment, the wall flow correction amount for the high frequency component is Chosn. ¹ However, the present invention is not limited to this, and the present invention can also be applied to the wall flow correction amount Chosn for high-frequency components disclosed in the apparatus disclosed in Japanese Patent Application Laid-Open No. 3-11639. (Invention of claim 8)
[0127]
In the embodiment, the estimated value of the fuel adhering portion temperature is described as the wall flow correction temperature Twf. However, the present invention also applies to the predicted intake valve temperature Tf described in Japanese Patent Laid-Open No. 3-134237. Is applicable.
[Brief description of the drawings]
FIG. 1 is a control system diagram of a first embodiment of the present invention.
FIG. 2 is a flowchart for explaining calculation of a wall flow correction temperature.
FIG. 3 is a characteristic diagram of an initial value of a wall flow correction temperature.
FIG. 4 is a characteristic diagram of a weighted average coefficient during firing.
FIG. 5 is a flowchart for explaining initialization.
FIG. 6 is a flowchart for explaining calculation and output of a fuel injection pulse width for each cylinder.
FIG. 7 is a flowchart for explaining calculation of a transient correction amount per cylinder.
FIG. 8 is a characteristic diagram of an equilibrium adhesion amount with respect to a target equivalent ratio.
FIG. 9 is a characteristic diagram of a reference adhesion magnification load term.
FIG. 10 is a characteristic diagram of a reference adhesion magnification rotation term.
FIG. 11 is a characteristic diagram of a basic quantity ratio.
FIG. 12 is a characteristic diagram of a quantity ratio rotation correction factor.
FIG. 13 is a flowchart for explaining calculation of a cylinder-by-cylinder wall flow correction amount in the first step change cycle;
FIG. 14 is a characteristic diagram of an increase gain.
FIG. 15 is a characteristic diagram of a weight loss gain.
FIG. 16 is a flowchart for obtaining a required value in synchronization with the injection timing.
FIG. 17 is a characteristic diagram for explaining fuel cut by cylinder.
FIG. 18 is a waveform diagram showing a comparison between an equilibrium adhesion amount and a change in the adhesion amount for each cylinder and a change in the equilibrium adhesion amount and the adhesion amount for all cylinders.
FIG. 19 is a waveform diagram showing the relationship between the amount of adhesion Mfn during fuel cut and the amount of adhesion Mf for all cylinders for a cylinder where fuel cut is performed.
FIG. 20 is a waveform diagram showing a change in the adhesion amount Mfn for a cylinder in which fuel cut is performed.
FIG. 21 is a waveform diagram for explaining the operation of the first embodiment when acceleration is performed immediately after performing fuel cut for a cylinder performing fuel cut.
FIG. 22 is a waveform diagram for explaining the operation of the first embodiment when the cylinder stop is released and the fuel supply is resumed for the cylinder that performs the cylinder stop.
[Explanation of symbols]
1 Engine body
4 Fuel injection valve
5 Intake port
6 cylinders
7 Intake valve
11 Engine controller
12, 13 Crank angle sensor
14 Air flow meter
17 Ignition switch
18 Starter switch

Claims (11)

A fuel supply device for supplying fuel to the intake passage and supplying fuel;
In an air-fuel ratio control apparatus for an engine with fuel wall flow correction relating to a delay in supplying fuel to a cylinder, which is a part of fuel from the fuel supply apparatus and adheres to an intake passage wall or an intake valve wall upstream of the cylinder,
An intake valve operation stop mechanism capable of stopping the operation of the intake valve;
Cylinder stop start means for starting cylinder stop for at least one cylinder using the intake valve operation stop mechanism under cylinder stop conditions;
A fuel adhering portion temperature estimating means for estimating a fuel adhering portion temperature during cylinder stop for a cylinder that is stopping the cylinder;
A fuel supply restarting means for releasing the cylinder stop of the cylinder that has been stopped until the cylinder stop condition is released, and restarting the fuel supply to the cylinder that has been stopped until then,
A fuel wall flow correcting means for correcting a fuel wall flow based on an estimated value of a fuel adhering portion temperature when the cylinder is stopped for a cylinder that restarts the fuel supply when the fuel supply is restarted. Fuel ratio control device. When the fuel adhering part is mainly an intake valve, the estimated value of the fuel adhering part temperature for the cylinder that is stopping the cylinder is a value that is lower than the cooling water temperature at the start of cylinder stopping by a predetermined value as the first target value. 2. The engine air-fuel ratio control apparatus according to claim 1, wherein the air-fuel ratio control apparatus of the engine is a value that converges with a first-order lag with respect to the first target value from the coolant temperature at the start of cylinder stop. The estimated value of the fuel adhering portion temperature for the cylinder that is performing the fuel cut is set to a second target value that is lower than the coolant temperature at the start of the fuel cut by a predetermined value. 3. The engine air-fuel ratio control apparatus according to claim 2, wherein the first target value is higher than the second target value when the value converges with a first-order lag with respect to the value. The first target value is a value obtained by adding the first offset amount to the initial value determined according to the cooling water temperature, and the second target value is a value obtained by adding the second offset amount to the initial value determined according to the cooling water temperature. The engine air-fuel ratio control apparatus according to claim 3. 5. The engine air-fuel ratio control apparatus according to claim 4, wherein the initial value determined according to the cooling water temperature is lower than the cooling water temperature at that time. The fuel wall flow correction amount when performing the fuel wall flow correction based on the estimated value of the fuel adhesion portion temperature while the cylinder is stopped is a transient correction amount per cylinder for a low frequency component. The engine air-fuel ratio control apparatus described. The fuel wall flow correction amount when performing the fuel wall flow correction based on the estimated value of the fuel adhering portion temperature while the cylinder is stopped is a cylinder-specific wall flow correction amount at the first cycle of the step change with respect to the high frequency component. The engine air-fuel ratio control apparatus according to claim 1. The fuel wall flow correction amount when performing the fuel wall flow correction based on the estimated value of the fuel adhering portion temperature while the cylinder is stopped is a cylinder-specific wall flow correction amount with respect to a high-frequency component. Engine air-fuel ratio control device. A means for calculating the transient correction amount per cylinder for the low frequency component is as follows:
An equilibrium adhesion amount calculating means for calculating an equilibrium adhesion amount for all cylinders representing an equilibrium state amount of a wall flow fuel amount;
A volume ratio calculating means for calculating a volume ratio corresponding to the time constant of the response of the wall flow fuel, and a difference calculating means for calculating a difference between the equilibrium deposit quantity and the deposit quantity for all cylinders which is a predictive variable at that time; ,
An adhesion rate calculating means for calculating an adhesion rate representing a change amount per one control period of the adhesion amount for all cylinders based on the adhesion amount difference and the amount ratio;
Transient correction amount calculating means for calculating a transient correction amount per cylinder based on the adhesion speed;
In the case of comprising means for updating the adhesion amount for all cylinders by adding the adhesion speed at the current injection to the adhesion amount for all the cylinders before the current injection in synchronization with the fuel injection for each cylinder,
The engine air-fuel ratio control apparatus according to claim 6, wherein the equilibrium adhesion amount or the split amount is calculated based on an estimated value of the temperature of the fuel adhesion portion while the cylinder is stopped. The means for calculating the cylinder-by-cylinder wall flow correction amount in the first step change cycle with respect to the high frequency component is:
An equilibrium adhesion amount calculating means for calculating an equilibrium adhesion amount for all cylinders representing an equilibrium state amount of a wall flow fuel amount;
A volume ratio calculating means for calculating a volume ratio corresponding to the time constant of the response of the wall flow fuel, and a difference calculating means for calculating a difference between the equilibrium deposit quantity and the deposit quantity for all cylinders which is a predictive variable at that time; ,
An adhesion rate calculating means for calculating an adhesion rate representing a change amount per one control period of the adhesion amount for all cylinders based on the adhesion amount difference and the amount ratio;
Transient correction amount calculating means for calculating a transient correction amount per cylinder for the low frequency component based on the adhesion speed;
An adhesion amount update means for updating the adhesion amount for all cylinders by adding the adhesion speed at the time of current injection to the adhesion amount for all cylinders before the current injection in synchronization with fuel injection for each cylinder;
An amount-of-attachment holding means for holding the amount of attachment for all the cylinders at the start of cylinder stoppage as the amount of attachment for the cylinder in which the cylinder is stopped;
Similarly, for a cylinder that is to be stopped, a value obtained by multiplying the difference between the adhesion amount for all the cylinders when the cylinder is stopped and the adhesion amount for the cylinder that is held by the attachment amount holding means and that is to be stopped is multiplied by the amount ratio. A transient correction amount 1 cycle before value setting means for setting the value as 1 cycle before the transient correction amount for the cylinder where the cylinder is stopped,
The difference between the transient correction amount and the value of the transient correction amount before the one cycle before the cylinder stop condition when the fuel supply is resumed when the cylinder stop condition is removed from the cylinder in which the cylinder is stopped From the cylinder-specific wall flow correction amount calculating means for calculating the cylinder-specific wall flow correction amount at the first step change cycle for the cylinder that has been stopped based on the response gain of the low-frequency component. The engine air-fuel ratio control apparatus according to claim 7, wherein The response gain of the low-frequency component is a product of the equilibrium adhesion magnification and the quantity ratio when calculating the equilibrium adhesion amount for all cylinders based on the equilibrium adhesion magnification with respect to the theoretical air-fuel ratio. The air-fuel ratio control apparatus for an engine according to claim 10.

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