JP2002364422A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine capable of always securing stability of an operation state of the engine, in the internal combustion engine selectively applying an exhaust passage having a different passage resistance when leading exhaust emission generated by engine combustion to an exhaust emission-controlling catalyst. SOLUTION: An engine 1 has two kinds of the passages having different passage resistances as the exhaust passages, i.e., the heat-retaining exhaust passage 43A and a cooling exhaust passage 43B. When the electronic controller 50 calculates a target fuel injection amount TAUF, the electronic controller 50 selectively uses two kinds of air-fuel ratio learning values FG (Hi), FG (Ri) according to utilization of the heat-retaining exhaust passage 43A or the cooling exhaust passage 43B, and reflects the used air-fuel ratio FG (Hi) or the FG (Ri) on the target fuel injection amount TAUF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes use of a plurality of exhaust passages provided in an exhaust system of an internal combustion engine and an exhaust purification catalyst provided downstream of the passages to optimize exhaust characteristics of the engine. The present invention relates to a control device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, an exhaust system (exhaust passage) of an internal combustion engine is generally provided with a catalyst for purifying harmful components in the exhaust gas.

[0003] In order for this type of catalyst to exhibit a high exhaust gas purifying capability, the bed temperature of the catalyst must be within a predetermined temperature range (active temperature range). For this reason, it is desirable that the catalyst bed temperature rises immediately after the engine is started, shifts to the activation temperature range, and is stably maintained within that range.

[0004] As a measure for quickly shifting the catalyst bed temperature to the activation temperature range and maintaining it within the activation temperature range,
For example, there is known a method of controlling the amount of heat received by a catalyst from exhaust gas by adjusting the temperature of the exhaust gas reaching the catalyst.

For example, in an apparatus described in Japanese Patent Application Laid-Open No. H11-324660, in an exhaust system of an internal combustion engine, two exhaust passages having different heat insulating properties are arranged in parallel on the upstream side of an exhaust gas purification catalyst, and An apparatus configuration for selectively switching the flow path of the discharged exhaust gas is employed. According to such an apparatus configuration, depending on which exhaust passage is selected,
It is possible to adjust the temperature of the exhaust gas reaching the exhaust gas purification catalyst. As a result, the catalyst bed temperature can be controlled to an optimum value.

[0006]

In general, when two exhaust passages having different shapes and structures, including two exhaust passages used in the apparatus described in the above-mentioned publication, have different heat retaining properties, In many cases, the dynamic resistance (flow path resistance) exerted on the exhaust flow by the exhaust passage must necessarily be different. For example, the heat retention of the exhaust passage is greatly related to the capacity of the passage or the size and shape of the passage cross section, and various factors such as the capacity of the passage or the size and shape of the passage cross section depend on the flow rate of the passage. It is also a factor that determines road resistance.

For this reason, when the exhaust passages having different heat insulating properties are to be selectively switched and used, the flow passage resistance upstream of the exhaust passage fluctuates, and this influence is exerted on the pressure in the exhaust system (exhaust pressure) and, consequently, on the exhaust passage. The pressure reaches the pressure (intake pressure) in the intake system of the engine. Due to this, the control gain is determined using the dynamics of the intake air taken in by the engine, the mixed gas supplied to the combustion chamber, or the gas upstream of the exhaust passage, such as the combustion gas and exhaust gas in the combustion chamber, as parameters. For operation control, its precision and reliability are impaired.

For example, in order to converge and maintain the oxygen concentration in the exhaust gas (corresponding to the air-fuel ratio in the air-fuel mixture) that fluctuates according to the operating state of the engine, the exhaust system In the feedback control that corrects the fuel injection amount based on the oxygen concentration in the exhaust gas detected inside, it may be difficult to make the oxygen concentration follow a target value.

As a result, the stability of the operating state of the engine, including the exhaust characteristics, has been reduced.

The present invention has been made in view of such circumstances, and an object thereof is to selectively exhaust gas passages having different flow path resistances when guiding exhaust gas generated by engine combustion to an exhaust gas purifying catalyst. An object of the present invention is to provide a control device for an internal combustion engine, which can always ensure the stability of the operating state of the engine.

[0011]

In order to achieve the above object, the present invention provides a catalyst for purifying exhaust gas discharged from an internal combustion engine in an exhaust system thereof, and a catalyst for forming a part of the exhaust system. A first exhaust passage that guides exhaust discharged from the engine to the catalyst, and an exhaust passage that also forms part of the exhaust system and guides exhaust discharged from the engine to the catalyst. A second exhaust passage having a passage resistance smaller than that of the passage, a flow rate of exhaust flowing into the first exhaust passage out of exhaust discharged from the engine,
Distribution ratio changing means for changing a distribution ratio with the flow rate of exhaust gas flowing into the exhaust passage, control means for controlling parameters relating to the operating state of the engine, recognition means for recognizing the controlled parameters, and control The history of the parameters controlled by the means is stored as a plurality of learning values that differ depending on the distribution ratio between the flow rate of the exhaust gas flowing into the first exhaust passage and the flow rate of the exhaust gas flowing into the second exhaust passage. And a control means for controlling the engine based on a distribution ratio of the flow rate of exhaust gas flowing into the first and second exhaust passages and a learning value corresponding to the distribution ratio. The gist of the present invention is to control a parameter related to an operation state.

Here, the distribution ratio of the exhaust gas flow rate here means
This means not only the relative flow ratio of the exhaust gas flowing into each exhaust passage, but also the absolute amount of the exhaust gas flowing into each exhaust passage. Therefore, the distribution ratio changing means may be, for example, the first
One of the exhaust passage and the second exhaust passage,
Alternatively, it may be provided with a valve mechanism or the like for controlling the degree of opening of both exhaust inflow ports, and may be provided at a branch point of an exhaust flow path existing upstream of each exhaust passage, for exhaust gas flowing into each passage. It may have a valve mechanism or the like for controlling the relative flow rate. Further, the concept of “change of the distribution ratio of the exhaust flow rate” includes, for example, setting the flow rate of the exhaust gas flowing into the first exhaust passage as “100%” and the flow rate of the exhaust gas flowing into the second exhaust passage. It is set as “0%” or the flow rate of the exhaust gas flowing into the first exhaust passage is set to “0%”.
% "And setting the flow rate of the exhaust gas flowing into the second exhaust passage as" 100% ",
The concept of selecting one of the first exhaust passage and the second exhaust passage as a flow passage for guiding the exhaust gas discharged from the engine to the catalyst is also included. Further, in the above configuration, in addition to two passages such as a first exhaust passage and a second exhaust passage, an exhaust passage or a flow passage having a different passage resistance, such as a third exhaust passage, a fourth exhaust passage,. After adding exhaust passages having the same road resistance, the distribution ratio changing means may function to change the distribution ratio of the flow rate of exhaust gas flowing into each passage.

According to the above configuration, even when the distribution of the exhaust gas flow rate to each exhaust passage varies, the pressure in the exhaust system (exhaust pressure) is increased on the upstream side (intake of the engine body and the intake system in the intake system). And combustion gas) (effects on intake air and combustion gas dynamics and pressure, etc.) are reflected in a plurality of learning values that differ according to the distribution ratio. For optimization control,
The stability (for example, the convergence to the target value) is appropriately maintained.

Further, in the above configuration, there is provided oxygen detecting means for detecting the oxygen concentration in the exhaust system, and the control means is configured to operate the engine so that the detected oxygen concentration becomes a target value. The feedback control may be performed on the parameter regarding

According to this configuration, in converging the oxygen concentration in the exhaust gas to be controlled (the air-fuel ratio in the air-fuel mixture) to an optimum value, the accuracy is excellent, but the response to transient disturbances and the like is high. In the implementation of air-fuel ratio feedback control (air-fuel ratio feedback control) for which it is difficult to obtain good performance, the degree of the effect of exhaust pressure on exhaust air-fuel ratio due to changes in the distribution ratio of exhaust gas flow to each exhaust passage Even if it fluctuates, such fluctuation can be quantitatively and promptly grasped and reflected on the air-fuel ratio feedback control.
Therefore, even when the dynamics of the exhaust gas (for example, pressure) fluctuates as a result of the change in the distribution ratio of the exhaust gas flow to each exhaust passage, the follow-up performance of the air-fuel ratio feedback control is always kept stable.

Further, based on the relative shape difference between the first exhaust passage and the second exhaust passage, the amount of heat released from the exhaust passing through the first exhaust passage is reduced by the second exhaust passage. The gist of the invention is that the heat radiation amount of the exhaust gas passing through the exhaust passage is lower than the heat radiation amount.

In an exhaust system of an internal combustion engine, a catalyst for purifying exhaust gas discharged from the engine exhibits its function under a condition where its bed temperature is within a specific range. For this reason, it is desirable to maintain the bed temperature of the catalyst in a specific range by controlling the temperature of exhaust gas reaching the catalyst.

The amount of heat radiation of the exhaust gas passing through the first exhaust passage is smaller than the amount of heat radiation of the exhaust gas passing through the second exhaust passage. By changing the distribution ratio between the flow rate of the inflowing exhaust gas and the flow rate of the exhaust gas flowing into the second exhaust passage, the temperature of the exhaust gas discharged downstream of both the exhaust passages can be maintained in a specific range. . According to this configuration, even if the pressure of the exhaust gas changes due to the function of the distribution ratio changing unit, the fluctuation is reflected on a plurality of different learning values according to the distribution ratio. Therefore, the influence of the fluctuation of the exhaust pressure does not affect other controls related to the operating state of the engine.

Further, the first exhaust passage may have a substantially circular cross-sectional shape, and the second exhaust passage may have a U-shaped cross-sectional shape.

The catalyst is a NOx catalyst that absorbs NOx when the concentration of the reducing component in the exhaust gas guided to the catalyst is low, and releases and reduces the absorbed NOx when the concentration of the reducing component in the exhaust gas is high. You may.

The NOx catalyst for releasing and reducing the absorbed NOx when the concentration of the reducing component in the exhaust gas becomes high has a specific temperature range in which the catalytic function is exhibited. The function of adjusting the exhaust gas temperature by the second exhaust passage and the distribution ratio changing means is effectively utilized. That is, the stability of the NOx purifying function by the NOx catalyst and the stability of the operating state of the engine are compatible with each other.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a control device for an internal combustion engine according to the present invention is embodied as a control device provided in a vehicle engine system will be described below.

In FIG. 1, a vehicle-mounted engine (hereinafter, referred to as an engine) 1 as an internal combustion engine includes a plurality of cylinders 11.

A piston 12 reciprocally provided in each cylinder 11 is connected to a crankshaft 14 which is an output shaft of the engine 1 via a connecting rod 13. The piston 12 in the cylinder 11
A combustion chamber 15 is formed on the upper side. Igniter 1
6 induces a high voltage at an appropriate timing to generate an electric spark in the spark plug 17. The air-fuel mixture introduced into the combustion chamber 15 is ignited by an electric spark generated by the ignition plug 17. The combustion chamber 15 communicates with the intake passage 31 through the intake port 30 and communicates with the exhaust passage 41 through the exhaust port 40.

A fuel injection valve 18 is provided so that the injection hole faces the intake port 30. Fuel injection valve 18
Is a fuel tank (not shown) via a pressure pump (not shown)
(Gasoline) transferred from the fuel cell is injected into the intake port 30 (in a direction toward the combustion chamber).

In the middle of the intake passage 31, a surge tank 32 for suppressing pulsation of the intake air, an air cleaner box 33 for removing dust and the like in the intake air are provided. An air flow meter 51 that outputs an electric signal corresponding to the mass (intake amount) GA of fresh air flowing through the air is attached. At a position downstream of the air flow meter 51 in the intake passage 31, a throttle valve 34 for adjusting the flow rate of intake air flowing through the intake passage 31 is provided.

The throttle valve 34 includes the same valve 34
Actuator 34a for opening and closing the throttle,
In addition to a throttle position sensor 52 that outputs an electric signal corresponding to the opening degree of the throttle valve 34 to an electronic control unit (ECU) 50, an electric signal that is mechanically connected to an accelerator pedal 35 and corresponds to the operation amount of the accelerator pedal 35 Accelerator position sensor 53 that outputs a signal to ECU 50
Is attached.

A timing rotor 55a attached to the end of the crankshaft 14 and an electromagnetic pickup 55b attached near the timing rotor 55a
The crank angle sensor 55 including the ECU 5 outputs an electric signal corresponding to the rotational phase of the crankshaft 14 to the ECU 5.
Output to 0. Further, a cooling water passage 1c is formed in a cylinder block 1a forming an outer shell of the cylinder 11, and in a cylinder 11 head 1b forming an outer shell of the intake port 30 and the exhaust port 40. A water temperature sensor 56 is provided at a predetermined portion of the cooling water passage 1c.
An electric signal corresponding to the temperature (cooling water temperature) THW of the cooling water flowing through the inside c is output to the ECU 50.

The open end of the intake port 30 facing the combustion chamber 15 is opened and closed by an intake valve 36 supported on the cylinder head 1b so as to be able to move forward and backward. The open end of the exhaust port 40 facing the combustion chamber 15 is also connected to the cylinder head 1b.
It is opened and closed by an exhaust valve 46 supported to be able to move forward and backward. These valves 36 and 46 are linked to the rotation of an intake camshaft (not shown) and an exhaust camshaft (not shown), respectively. . In addition, a cam sprocket (not shown) attached to each end of the intake camshaft 37 and the exhaust camshaft 47 is connected to the crankshaft 14 via a timing chain (not shown).

During operation of the engine 1, the rotational force of the crankshaft is transmitted to each camshaft via the timing chain and each cam sprocket. As a result,
Each of the camshafts 37 and 47 rotates in synchronization with the rotation of the crankshaft 14, and opens and closes each of the valves 36 and 46 at a predetermined timing corresponding to the reciprocation of the piston 12. That is, the valves 36 and 46 are operable at predetermined timings in synchronization with the intake stroke, the compression stroke, the explosion / expansion stroke, and the exhaust stroke of the engine 1 according to the vertical movement of the piston 12.

In the middle of the exhaust passage 41, the oxygen sensor 54, the starting catalyst casing 42, the passage switching valve 57, the branch passage 43, the exhaust temperature sensor 58, the NOx catalyst casing 44, A source catalyst casing 45 is sequentially provided.

The oxygen sensor 54 outputs an electric signal corresponding to the oxygen concentration in the exhaust gas to the ECU 50.

In the starting catalyst casing 42 and the three-way catalyst casing 45, hydrocarbons (HC) and carbon monoxide (C) contained in the exhaust gas flowing into the casings 42 and 45 are provided.
A three-way catalyst for purifying various harmful components such as O) and nitrogen oxides (NOx) is housed. When the oxygen concentration in the exhaust gas is close to a predetermined value (a value corresponding to a condition that the air-fuel ratio of the air-fuel mixture involved in engine combustion becomes a stoichiometric air-fuel ratio), the three-way catalyst removes hydrocarbons (HC) contained in the exhaust gas. ), Carbon monoxide (CO) and nitrogen oxides (NOx) are purified with the highest efficiency. The starting catalyst casing 42 and the three-way catalyst casing 45 have different capacities and arrangements. That is, as compared with the three-way catalyst casing 45, the starting catalyst casing 42 has a smaller capacity and is arranged near the combustion chamber 15, so that it is easily exposed to high-temperature exhaust just discharged from the combustion chamber 15. Heat capacity is also small. In other words, the temperature of the three-way catalyst in the starting catalyst casing 42 rises faster than other parts of the exhaust passage 41 even under conditions where the temperature of the entire exhaust system is not sufficiently high, such as immediately after the start of the engine. In addition, various harmful components in the exhaust gas can be purified.

On the downstream side of the starting catalyst casing 42, the exhaust passage 41 is provided with two parallel passages 43A, 43A.
By branching to 3B, a branch passage 43 is formed. These two branched passages 43A and 43B are configured to gather at the upstream of the NOx catalyst casing 44.

FIG. 2 shows a section II-II of the branch passage portion 43.

As shown in FIG. 2, one of the branch passage portions 43 (hereinafter referred to as a heat-retaining exhaust passage) 43A has a substantially circular cross-sectional structure. On the other hand, the other passage (hereinafter, referred to as a cooling exhaust passage) 43B has a U-shaped cross-sectional structure. In other words, the cooling exhaust passage 43B
The heat radiation surface (contact surface between the exhaust gas and the inner wall of the passage) is set to be larger than that of the heat retaining exhaust passage 43A, and the amount of heat radiation to the outside becomes larger for the exhaust gas passing through the passage 43B.

At a branch point on the upstream side of the two passages 43A and 43B, a passage switching valve 57 is provided. The passage switching valve 57 is operated by a switching valve actuator 57a that is driven based on a command signal from the ECU 50, and changes the path of the exhaust gas flowing from the upstream (starting catalyst casing 42) toward the branch passage portion 43 from the passage 43A to the passage 43A. 43B,
Further, the passage 43B is alternatively switched to the passage 43A.

N provided downstream of the branch passage 43
In the Ox catalyst casing 44, a NOx catalyst for purifying NOx components contained in the exhaust gas flowing into the casing 44 is accommodated.

N contained in the NOx catalyst casing 44
The Ox catalyst uses, for example, alumina (Al2O3) as a carrier, and on the carrier, for example, an alkali metal such as potassium (K), sodium (Na), lithium (Li), or cesium Cs, or an alkali metal such as barium Ba or calcium Ca. Rare earths such as earth, lanthanum (La) and yttrium (Y) and a noble metal such as platinum Pt are supported.

This NOx catalyst absorbs NOx when a large amount of oxygen is present in the exhaust gas, the oxygen concentration in the exhaust gas is low, and the reducing component (for example, the unburned component (HC) of the fuel) is reduced. NOx in the presence state
_It is reduced to ₂ or NO and released. NOx released as NO ₂ or NO is further reduced by reacting promptly with HC or CO in the exhaust gas to become N ₂ . Incidentally, HC and CO themselves are oxidized to H ₂ O and CO ₂ by reducing NO ₂ and NO. That is, the oxygen concentration in the exhaust gas introduced into the NOx catalyst casing 44 and the HC concentration
By appropriately adjusting the components, HC, CO, and NOx in the exhaust gas can be purified.

An exhaust temperature sensor 58 provided between the branch passage 43 and the NOx catalyst casing 44 sends an electric signal corresponding to the temperature of exhaust gas introduced into the NOx catalyst casing 44 through the branch passage 43 to the ECU 50. Output.

Downstream of the NOx catalyst casing 44, a three-way catalyst casing 45 is provided. Under the condition that the function of the three-way catalyst accommodated in the three-way catalyst casing 45, that is, the oxygen concentration in the exhaust is within a predetermined range, the H in the exhaust
The function of purifying C, CO and NOx simultaneously is as described above.

The ECU 50 is a known microcomputer. Inside the ECU 50, a central processing unit (CP
U), a read-only memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit including a timer counter, an A / D converter, an external output circuit, etc., are mutually connected to form a logical operation circuit. ing.

The ECU 50 configured as described above includes the throttle position sensor 52, the accelerator position sensor 53, the oxygen sensor 54, the crank angle sensor 55,
In addition to the water temperature sensor 56, detection signals output from various sensors attached to various parts of the engine 1 are input via an external input circuit, and various information related to the operating state of the engine 1 is grasped. Then, based on these various information, each component of the engine 1 such as the igniter 16, the fuel injection valve 18, the throttle actuator 34a and the switching valve actuator 57a is driven. That is, the ECU 50
Control of fuel injection into the intake port 30 through the fuel injection valve 18 (fuel injection control; including air-fuel ratio feedback control), and ignition timing of the air-fuel mixture introduced into the combustion chamber 15 (timing for applying current to the igniter 16) ) (Ignition timing control), and through the operation of the passage switching valve 57, the warming exhaust passage 43A or the cooling exhaust passage 43B.
Is appropriately selected as an exhaust passage, and various controls related to the operation of the engine 1 such as control for switching (exhaust passage switching control) are also executed.

Next, the exhaust passage switching control among the various controls executed by the ECU 50 will be described.

In order to make full use of the functions of the NOx catalyst and the three-way catalyst contained in the casings 44 and 45 of the exhaust passage 41, during operation of the engine 1, the bed temperature of each catalyst is adjusted to a specific range ( In the following, it is necessary to stably maintain such a temperature range in which the catalytic function is significantly exerted within an active temperature range. As described above, the engine 1 according to the present embodiment has a shape (heat retention) as a part of the exhaust passage 41.
Different exhaust passages 43A and 43B are arranged in parallel. The ECU 50 constantly monitors the temperature of the exhaust flowing into the NOx catalyst casing 44 based on the output signal of the exhaust temperature sensor 58. Then, the starting catalyst casing 42 and the NOx catalyst are operated through the function of the passage switching valve 57 so that the observed exhaust gas temperature is maintained within the activation temperature range for the NOx catalyst housed in the NOx catalyst casing 44. Control is performed to appropriately switch the exhaust passage between the casings 44 to a passage 43A having a high heat retention or a passage 43B having a low heat retention (a passage having a high cooling).

Next, the fuel injection control executed by the ECU 50 will be described.

The ECU 50 determines the amount of fuel injected from the fuel injection valve 18 such that the air-fuel ratio in the air-fuel mixture involved in engine combustion becomes a target value (for example, a stoichiometric air-fuel ratio) suitable for the operating state of the engine 1. Is performed for controlling the air-fuel ratio. In the air-fuel ratio feedback control, the ECU 50 first determines the intake air amount GA based on the output signal of the air flow meter 51, and determines the engine speed N based on the output signal of the crank angle sensor 55.
E is calculated, and based on these parameters GA and NE, for example, the basic fuel injection amount (time) TA according to equation (i).
Ask for UBS. TAUBS = K × GA / NE (i) where K is a preset constant. The air-fuel ratio feedback correction coefficient FAF, the air-fuel ratio learning value FG, and various other controls (for example, , The final target fuel injection amount (time) TAUF according to, for example, the arithmetic expression (ii) by taking into account various correction coefficients obtained by the increase control during warm-up operation or the increase or decrease control during acceleration / deceleration. decide. TAUF = TAUBS × FAF × FG × (ii) Here, basic characteristics of the air-fuel ratio feedback correction coefficient FAF and the air-fuel ratio learning value FG employed in the present embodiment will be described.

FIGS. 3 (a), 3 (b) and 3 (c)
Is a detection signal (FIG. 3A) of the oxygen sensor 54 observed during the air-fuel ratio feedback control.
The determination signal of the ECU 50 based on the detection signal of FIG.
(B)) and the air-fuel ratio feedback correction coefficient FAF calculated based on the determination signal of the ECU 50,
It is a time chart which shows each waveform on the same axis.

The ECU 50 determines whether the air-fuel ratio of the air-fuel mixture involved in engine combustion is rich (excessive fuel) or lean (excessive oxygen) based on the output signal of the oxygen sensor 54 corresponding to the oxygen concentration in the exhaust gas. Judge. When the air-fuel ratio is determined to be rich, the air-fuel ratio feedback correction coefficient FAF is decreased (lean skip), and when the air-fuel ratio is determined to be lean, the fuel injection amount is corrected (rich skip). Repeat periodically (perform air-fuel ratio feedback control).

Further, the control result of the air-fuel ratio feedback control is sequentially processed, and stored on a map as an air-fuel ratio learning value FG for each of a plurality of learning regions classified based on the operating state of the engine 1. The air-fuel ratio learning value FG is
This corresponds to the average value of the air-fuel ratio feedback correction coefficient FAF obtained in each learning region.

For example, an average value (hereinafter referred to as an average air-fuel ratio feedback correction coefficient) FAFAV of the air-fuel ratio feedback correction coefficient FAF in a certain learning region is calculated based on the following equation (iii). However, FAFLSKP: FA immediately before lean skip (weight loss)
F (corresponding to point α in FIG. 3 (c)) FAFRSKP: FAF immediately before rich skip (increase) (corresponding to point β in FIG. 3 (c)) In the air-fuel ratio feedback control, the ECU 50 performs the average air-fuel ratio feedback correction. Coefficient FAFAV is set to "1.0
0 "(correction rate is 0%). Therefore, for example, if the average air-fuel ratio feedback correction coefficient FAFAV is “1.0
5 "(5% increase), then the target fuel injection amount TA
In calculating the UF, this “1.05” is taken into account as the air-fuel ratio learning value FG (integrated into the basic fuel injection amount TAUBS).

FIG. 4A shows learning sections (sections on the map) of the air-fuel ratio learning value applied in the present embodiment. As shown in FIG. 4 (a), the air-fuel ratio learning value applied by the ECU 50 in the present embodiment is such that the heat retaining exhaust passage 43A is selected as the exhaust passage extending from the starting catalyst casing 42 to the NOx catalyst casing 44. Learning value (hereinafter referred to as a learning value at the time of exhaust heat retention) F
G (Hi) and a learning value (hereinafter referred to as a learning value during exhaust cooling) FG (Ri) corresponding to a state in which the cooling exhaust passage 43B is selected. Further, each of these two types of air-fuel ratio learning values FG (Hi) and FG (Ri) is a learning region (i = 1, 2, 3, 4, 5) divided based on the magnitude of the intake air amount GA. It is stored and updated as a different numerical value every time (see also FIG. 4B). as a result,
Ten different air-fuel ratio learning values (FG (H1) to FG (H
5), FG (R1) to FG (R1)) are appropriately stored, updated, or utilized according to the operating state of the engine 1. The air-fuel ratio learning value FG is basically one of the basic fuel injection amount TAUBS for calculating the target fuel injection amount TAUF in the fuel injection control, regardless of whether the air-fuel ratio feedback control is being executed. Although the correction coefficient is always adopted, the update is performed in accordance with the execution of the air-fuel ratio feedback control.

Next, the fuel injection control according to the present embodiment (the case where the execution of the air-fuel ratio feedback control is not performed,
(Including when the air-fuel ratio feedback control is performed)
Will be described with reference to a flowchart.

FIG. 5 is a flowchart showing a control procedure of the fuel injection control in the present embodiment. This routine is executed by the ECU 50 at predetermined intervals.

When the processing shifts to this routine, the ECU 5
0 is the basic fuel injection amount T in step S101.
Various parameters relating to the operating state of the engine 1, such as the current intake air amount GA and the engine speed NE required for determining the AUBS, are grasped.

In step S102, the ECU 50
In light of the current operating state of the engine 1, it is determined whether or not the execution condition of the air-fuel ratio feedback control is satisfied. The ECU 50 determines that the execution condition of the air-fuel ratio feedback control is satisfied, for example, when the cooling water temperature THW is higher than a predetermined temperature.

If the determination in step S102 is affirmative, the ECU 50 shifts the processing to step S103 and sets the feedback control execution flag F to "1". On the other hand, if the determination in step S102 is negative, the ECU 50 shifts the processing to step S104 and sets the feedback control execution flag F to “0”.

After the processing in step S103 or S104, the ECU 50 executes the processing in step S1.
Move to 05. In step S105, the ECU 50
Is a warming exhaust passage 43 serving as an exhaust passage from the starting catalyst casing 42 to the NOx catalyst casing 44.
It is determined which one of the exhaust passage A and the cooling exhaust passage 43B (see FIGS. 1 and 2) is selected.

In step S106, the ECU 50
The learning area i to which the current operation state (the intake air amount GA) belongs is recognized.

In step S107, the ECU 50
The basic fuel injection amount TAUBS is calculated based on the intake air amount GA and the engine speed NE obtained in the previous step S101 (refer to operation formula (i)).

In step S108, the ECU 50
Various correction coefficients, such as an air-fuel ratio feedback correction coefficient FAF and an air-fuel ratio learning value FG, necessary for calculating the target fuel injection amount TAUF are determined. Air-fuel ratio feedback correction coefficient FAF
Is calculated as described in FIG.
At this time, when the feedback control execution flag F is set to “0”, a constant “1.00” is adopted as the air-fuel ratio feedback correction coefficient FAF.

In step S109, the ECU 50
Basic fuel injection amount TAUB obtained in step S108
The target fuel injection amount TAUF is calculated based on S and the various correction coefficients obtained in step S109 (refer to operation formula (ii)).

The obtained target fuel injection amount TAU
As described above, F corresponds to the amount of fuel injected and supplied into the combustion chamber 15 through the fuel injection valve 18.

Next, in step S110, the ECU 50 determines whether the feedback control execution flag F is set to "1", that is, whether the air-fuel ratio feedback control is being executed. And the ECU 50
If the determination is affirmative, the process proceeds to step S111. If the determination is negative, the process exits this routine.

In step S111, the ECU 50
It is determined whether or not the current time corresponds to the timing immediately before the lean skip or the timing immediately before the rich skip (point α or point β in FIG. 3C). And the ECU 50
If the determination is affirmative, the process proceeds to step S112. If the determination is negative, the process proceeds to step S11.
Move to 3.

In step S112, the ECU 50
The average air-fuel ratio feedback correction coefficient FA is determined based on the latest air-fuel ratio feedback correction coefficients FAFLSKP (point α) and FAFRSKP (point β) adopted at the points α and β.
The latest value of FAV is calculated (refer to operation formula (iii)).

In step S113, the ECU 50
The latest value of the average air-fuel ratio feedback correction coefficient FAFAV calculated in step S112 is updated to the air-fuel ratio learning value F corresponding to the region i recognized in step S106.
It is stored as G, and the process exits from this routine.

It should be noted that regardless of whether or not the air-fuel ratio learning value FG has been updated in step S113, whether the feedback control execution flag F has been set to "1" or "0" Regardless of the above, when calculating the target fuel injection amount TAUF, the above step S
In 108 and S109, the latest learning value FG (for example, FG (H3), FG (R
2) etc.) will be adopted in each routine.

As described above, in the control device according to the present embodiment, in a situation where different configurations (the heat retaining exhaust passage 43A and the cooling exhaust passage 43B) are employed as a part of the exhaust passage, The two types of air-fuel ratio learning values FG (H
i), FG (Ri) is adopted, and a control structure that reflects these learning values as correction amounts to the target fuel injection amount TAUF is applied.

For example, as in the case of the engine 1, the bed temperature of the NOx catalyst or the three-way catalyst provided in the exhaust system is shifted to and maintained at an optimum value (optimum range) for exerting the exhaust gas purifying function of the catalyst. Therefore, in an internal combustion engine having a function of changing the property of the exhaust passage according to the situation, the property of the exhaust passage is changed, so that the influence of the exhaust pressure on the gas pressure in the combustion chamber, the intake passage, etc. Will also vary. There is a concern that such fluctuations in the gas pressure in the combustion chamber and the intake passage may impair the exhaust characteristics and the stability of the engine output.

Here, optimization control of the operating state performed by the conventional control device (for example, air-fuel ratio feedback control, etc.)
Thus, it has been difficult to ensure sufficient stability of exhaust characteristics and engine output in response to such fluctuations in gas pressure in the combustion chamber and the intake passage.

In particular, in a passage structure in which two kinds of exhaust passages having different flow path resistances are selectively switched as in the engine 1 according to the present embodiment, the exhaust pressure is remarkably affected by the switching of the exhaust passage. Because a step may occur,
In order to maintain the exhaust characteristics and the engine output in a stable state, the control related to the operation state corresponding to the occurrence of the step
High responsiveness and suitability are required.

In this regard, according to the control device of the present embodiment, even if the variation is caused by a change in the exhaust passage, the variation varies depending on each of the exhaust passages (43A, 43B). Hi), FG (R1)). Therefore, the stability (for example, the convergence to the target value) of the control for optimizing the operating state of the engine 1, especially the pressure and the dynamics of the gas in the intake system and the combustion, is improved.

In particular, in order to converge a control amount (air-fuel ratio in an air-fuel mixture) to an optimum value as in the air-fuel ratio feedback control, it is necessary to obtain high responsiveness and high responsiveness to transient disturbances. According to the present embodiment, even when the degree of the effect of the exhaust pressure on the air-fuel ratio of the air-fuel mixture fluctuates in the execution of the control that is difficult, the air-fuel ratio feedback control is quantitatively and quickly grasped according to the present embodiment. Will be reflected in As a result, the function of adjusting the exhaust gas temperature (catalyst bed temperature) by appropriately switching the exhaust passage, that is, the stability of the exhaust gas purifying function using the NOx catalyst (or three-way catalyst), and the stability of the operating state of the engine are compatible. It will be able to be planned.

In the present embodiment, two kinds of passage structures having different passage resistances, such as a heat-retaining exhaust passage 43A and a cooling exhaust passage 43B, are formed in the exhaust system, and a passage switching valve is provided at the entrance of both passage structures. By providing the 57, a configuration in which the exhaust passage between the starting catalyst casing 42 and the NOx catalyst casing 44 is selectively switched is applied. On the other hand, for example, the passage switching valve 5 is controlled so as to variably adjust the flow ratio of the exhaust gas introduced into both passages 43A and 43B steplessly.
7 or by adopting another valve structure, two or more different air-fuel ratio learning values may be set in accordance with the variably adjusted exhaust gas flow ratio. In addition, the present invention is not limited to the structure such as the branch passage portion 43 applied to the present embodiment, but may be applied to any passage structure that substantially changes the flow passage resistance or the like in the exhaust system. A control structure that is applied in the embodiment, that is, a control structure that sets a plurality of different air-fuel ratio learning values according to changes in the physical properties of the exhaust passage and reflects the learning value on the target fuel injection amount TAUF. Can.

The plurality of learning values that differ according to the change in the physical properties of the exhaust passage need not be related to the fuel injection control. For example, a known exhaust gas recirculation device including an exhaust gas recirculation passage that bypasses the intake passage upstream of the combustion chamber and the exhaust gas passage downstream of the combustion chamber, and a control valve that adjusts the opening of the exhaust gas recirculation passage is provided. In such an engine, as the correction amount of the opening degree of the control valve, a plurality of learning values different according to the change in the physical property of the exhaust passage may be adopted as described above. Further, in a well-known ignition timing control (feedback control) for advancing the ignition timing of the engine 1 based on a signal of a vibration sensor (knocking sensor) not shown, the exhaust passage is used as a correction amount of the ignition timing as described above. Even if a plurality of different learning values are adopted in accordance with the change in the physical property of the present embodiment, an effect equivalent to or equivalent to that of the present embodiment can be obtained.

In this embodiment, each of the two air-fuel ratio learning values FG (Hi) and FG (Ri) is used as the intake air amount G
It was further classified based on the size of A. On the other hand, regardless of the difference in the intake air amount GA, the exhaust passage 43
A learning value that differs only depending on which of A and 43B is employed may be used as the correction amount. Further, in place of the intake air amount GA, the classification of the learning value may be set using other parameters such as the pressure (intake pressure) in the intake passage 31 and the engine speed, or a combination of these parameters.

Further, in the present embodiment, the branch passage portion 4
3 adopts a configuration including two exhaust passages such as a heat retaining exhaust passage 43A and a cooling exhaust passage 43B. However, three or more exhaust passages having different flow path resistances or three or more having the same flow path resistance are used. A configuration having more than one exhaust passage may be applied together with a valve structure or the like that makes the flow rate of exhaust flowing into each exhaust passage variable.

Further, the air-fuel ratio learning value FG applied in the present embodiment is set so that its value is updated successively when the air-fuel ratio feedback control is executed. On the other hand, depending on whether the warming exhaust passage 43A or the cooling exhaust passage 43B is used as a part of the exhaust passage (according to the physical properties of the exhaust passage), for example, the target fuel injection amount Even if a control structure is used in which two types of learning values preset as correction amounts are used without updating, an effect equivalent to the present embodiment can be obtained. Further, two or more learning values according to the physical properties of the exhaust passage may be applied in such a manner that updating is not performed under predetermined operating conditions and updating is performed under other predetermined operating conditions. Good.

[0081]

As described above, according to the present invention,
Even when the distribution ratio of the exhaust gas flow to each exhaust passage is changed, the effect of the pressure fluctuation in the exhaust system on the dynamics of the combustion gas and intake air is reflected in a plurality of learning values, so that the operation of the engine is performed. The stability (for example, the convergence to the target value) of the control regarding the optimization of the state, particularly the exhaust characteristics, can be suitably maintained.

Further, the followability of the air-fuel ratio feedback control is always kept stable.

In addition, the influence of such a change in the exhaust pressure is as follows.
It does not extend to other controls relating to the operating state of the engine.

Further, the stability of the NOx purifying function by the NOx catalyst and the stability of the operating state of the engine can be achieved at the same time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an in-vehicle engine provided with a control device according to an embodiment of the present invention.

FIG. 2 shows a branch passage portion forming a part of an exhaust passage in FIG. 1;
FIG. 2 is a plan view showing a II-II cross section (contour).

FIG. 3 is a time chart showing transition of an air-fuel ratio feedback correction coefficient based on a detection signal from an oxygen sensor.

FIG. 4 is a flowchart showing a processing procedure of fuel injection control performed when feedback control is not executed in the embodiment.

FIG. 5 is a flowchart showing a processing procedure of fuel injection control performed at the time of feedback control in the embodiment.

[Explanation of symbols]

Reference Signs List 1 engine (internal combustion engine) 1a cylinder block 1b cylinder head 1c cooling water passage 14 crankshaft 15 combustion chamber 16 igniter 17 spark plug 18 fuel injection valve 30 intake port 31 intake passage 32 surge tank 33 air cleaner box 34 throttle valve 34a throttle actuator 35 accelerator pedal 36 intake valve 40 exhaust port 41 exhaust passage 42 starting catalyst casing 43 branch passage 43A heat retaining exhaust passage (first exhaust passage) 43B cooling exhaust passage (second exhaust passage) 44 NOx catalyst casing 45 Three-way catalyst casing 46 Exhaust valve 50 Electronic control unit (ECU) 51 Air flow meter 52 Throttle position sensor 53 Accelerator position sensor 54 Oxygen sensor 55 Crank Sensor 55a timing rotor 55b electromagnetic pickup 56 water temperature sensor 57 passage switching valve actuator (distribution ratio changing a means) 57a switching valve (constituting a distribution rate changing unit)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/24 F01N 3/24 C F G L M N R 3/26 3/26 L M 3/28 301 3/28 301A 301C 301F 301G 7/08 7/08 Z F02D 41/04 330 F02D 41/04 330M (72) Inventor Tokuhisa Nakagawa 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Corporation (reference) 3G004 BA06 DA01 EA01 3G091 AA17 AB03 AB05 AB09 BA04 CB01 DB08 DC01 DC02 EA01 EA07 EA16 EA17 EA34 FB02 FB03 FC07 FC08 GB02W GB04W GB06W GB10X HA08 HA12 HA36 HA37 HB02 3G301 HA01 JA21 JA03 KA01 ND01 NC03 KA01 ND PD11Z PE03Z PE08Z PF03Z

Claims (5)

[Claims] 1. A catalyst for purifying exhaust gas discharged from an engine in an exhaust system of an internal combustion engine, and a first exhaust passage which forms a part of the exhaust system and guides exhaust gas discharged from the engine to the catalyst. A second exhaust passage which also forms a part of the exhaust system and guides exhaust discharged from the engine to the catalyst, wherein the second exhaust passage has a smaller flow resistance than the first exhaust passage; Distribution ratio changing means for changing a distribution ratio between a flow rate of exhaust gas flowing into the first exhaust passage and a flow rate of exhaust gas flowing into the second exhaust passage out of exhaust gas discharged from the engine; Control means for controlling parameters relating to the operating state of the control means; recognition means for recognizing the controlled parameters; and history of the parameters controlled by the control means, the flow rate of exhaust gas flowing into the first exhaust passage, Previous Storage means for storing as a plurality of learning values different according to a distribution ratio of the flow rate of the exhaust gas flowing into the second exhaust passage, and the control means comprises: the first and second exhaust passages A control device for an internal combustion engine, comprising: controlling a parameter relating to an operation state of the engine based on a distribution ratio of a flow rate of exhaust gas flowing into the engine and a learning value corresponding to the distribution ratio. 2. An engine according to claim 1, further comprising an oxygen detector for detecting an oxygen concentration in said exhaust system, and wherein said controller controls a parameter relating to an operating state of said engine such that said detected oxygen concentration becomes a target value. The control device for an internal combustion engine according to claim 1, wherein feedback control is performed. 3. A heat radiation amount of exhaust passing through the first exhaust passage based on a difference in a relative shape between the first exhaust passage and the second exhaust passage. 3. The control device for an internal combustion engine according to claim 1, wherein the heat radiation amount of the exhaust gas passing through the exhaust passage is lower than the heat radiation amount. 4. The apparatus according to claim 1, wherein the first exhaust passage has a substantially circular cross section, and the second exhaust passage has a U-shaped cross section. A control device for an internal combustion engine according to claim 1. 5. The catalyst according to claim 1, wherein the catalyst absorbs NOx when the concentration of the reducing component in the exhaust gas guided to the catalyst is low, and releases and reduces the absorbed NOx when the concentration of the reducing component in the exhaust gas increases. The control device for an internal combustion engine according to any one of claims 1 to 4, characterized in that: