JPH09137740A - Exhaust gas purifying device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To warm a catalyser by doubly using an exhaust gas circulating passage for a secondary air passage. SOLUTION: A part of supercharging air is made to flow backward in a channel of a passage 36 → a three-way valve 35 → an EGR passage 33 →an exhaust gas circulating port 31 by switching the three-way valve 35 over to the side of a surge tank 19 while a supercharger 18 is driven and it is supplied as secondary air to the upstream side of a catalyser 29 of an exhaust pipe 28 at the time of catalyser warming control. Thereafter, CO and HC in exhaust gas are increased by increasing and correcting fuel injection quantity, they are reacted with oxygen in secondary air by the catalyser 29, and the catalyser 29 is efficiently warmed by its heat of reaction. At the time of supercharging, the supercharger 18 is driven by closing a by-pass opening and closing valve 21, and exhaust gas circulating control is carried out by switching the three-way valve 35 over to the upstream side (passage 37 side) of the supercharger 18. At the time of non-supercharging, exhaust gas circulating control is carried out by switching the three-way valve 35 to the side of the Surge tank 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine equipped with a supercharger provided in an intake system.

[0002]

2. Description of the Related Art Generally, a three-way catalyst for purifying exhaust gas mounted on a vehicle has a harmful component (HC, C) in the exhaust gas.
O, NOx) is made to be harmless by oxidation / reduction reaction under high temperature conditions, and in order to effectively exert its exhaust gas purification ability, the temperature of the catalyst is set to an activation temperature (generally 3
It is necessary to raise the temperature to 100 to 350 ° C. Therefore,
Until the catalyst temperature rises to the activation temperature after starting the engine, the exhaust gas purification capacity is low, the amount of harmful components in the exhaust gas is increased, and the emission is deteriorated.

In order to solve this problem, in recent years, in order to warm up the catalyst to the activation temperature early after the engine is started, for example, as shown in JP-A-5-171973, an exhaust pipe on the upstream side of the catalyst is provided. While introducing secondary air (atmosphere) from the outside, the fuel injection amount is controlled to the rich side to increase CO in the exhaust gas, and this reacts with oxygen in the secondary air in the catalyst to generate the reaction heat. There is one that warms up the catalyst. However, since the exhaust pressure in the exhaust pipe, where the exhaust gas is discharged from the engine, becomes higher than atmospheric pressure, in order to introduce a large amount of secondary air into the exhaust pipe from the outside, an air pump that pumps the secondary air into the exhaust pipe is used. In addition, the secondary air supply device including the electromagnetic valve that shuts off the flow path of the secondary air while the air pump is stopped is required, and there is a disadvantage that the configuration becomes complicated and the cost becomes high.

[0004]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 86847, in an engine equipped with a mechanical drive type supercharger (so-called supercharger), the exhaust gas recirculation passage is also used as a secondary air passage, and the intake pressure is reduced in an operating region below a set load. When the intake air pressure is higher than the exhaust pressure, a part of the intake air is made to flow backward in the exhaust gas recirculation passage to be supplied to the exhaust pipe, and the air-fuel ratio is controlled to the rich side aiming at reduction of NOx in the exhaust gas, Some have been designed to improve the purification performance.

In this known example, the exhaust gas recirculation passage is also used as the secondary air passage, so that the conventional secondary air supply device is not required, but the exhaust gas recirculation passage is formed. The region used as the secondary air passage is the operating region where the intake pressure is lower than the set load and the exhaust pressure is higher than the exhaust pressure, and no control is performed in consideration of the warm-up condition of the catalyst. In short, this known example is likely to generate NOx when the engine temperature is high.
The exhaust gas is purified by controlling the air-fuel ratio to the rich side to reduce the combustion temperature and reducing the combustion temperature, and reacting CO and HC generated by the rich side with oxygen in the secondary air with a catalyst. To do. Therefore, with the control of this known example, it is impossible to effectively perform the catalyst early warm-up required when the engine is not warmed up immediately after the engine is started.

The present invention has been made in consideration of such circumstances, and therefore an object thereof is to discharge an internal combustion engine capable of efficiently warming up a catalyst by utilizing supercharged air from the supercharger. It is to provide a gas purifier.

[0007]

In order to achieve the above object, the exhaust gas purifying apparatus for an internal combustion engine according to claim 1 of the present invention determines the warm-up condition of the catalyst by the catalyst warm-up judging means,
When it is determined that the catalyst is not warmed up, the catalyst warm-up control means opens the exhaust gas recirculation control valve in the exhaust gas recirculation passage while the supercharger is being driven, and the catalyst discharged from the supercharger is opened. A part of the supply air is made to flow backward in the exhaust gas recirculation passage to be supplied to the exhaust system, and the amount of fuel injection to the internal combustion engine is controlled to the rich side to increase CO and HC in the exhaust gas to catalyze them. To react with oxygen in the secondary air, and heat the reaction to warm up the catalyst efficiently. As a result, the exhaust gas recirculation passage is also used as the secondary air passage, and the catalyst can be warmed up efficiently.

Further, in claim 2, the supercharger control means for controlling the drive / stop of the supercharger expands the supercharging region when the catalyst warm-up determination means determines that the catalyst is not warmed up. To do. As a result, the catalyst warm-up control region can be expanded when the catalyst is not warmed up, and the catalyst warm-up functioning power can be further improved.
When expanding the supercharging region, the engine speed may be increased against the supercharger drive load applied to the internal combustion engine.

Further, according to a third aspect of the present invention, passage switching means for switching the exhaust gas recirculation passage between the upstream side and the downstream side of the supercharger is provided, and the passage switching means is used by the switching control means during catalyst warm-up control and non-supercharging. Switch the means downstream of the supercharger. As a result, during catalyst warm-up control, the supercharging pressure (discharge pressure of the supercharger) is effectively applied to the exhaust gas recirculation passage to smooth the flow of secondary air supplied to the exhaust system. Further, at the time of non-supercharging, the exhaust gas (EGR gas) that recirculates from the exhaust system is supplied to the downstream side of the supercharger so that the exhaust gas recirculates smoothly. On the other hand, at the time of supercharging other than the catalyst warm-up control, the passage switching means is switched to the upstream side of the supercharger so that the suction negative pressure of the supercharger is effectively acted on the exhaust gas recirculation passage and the exhaust gas recirculation passage is discharged. The recirculation is promoted and the purification rate of the exhaust gas by the exhaust gas recirculation control is increased.

According to the present invention, the elapsed time after the engine is started is timed by the time measuring means, and the catalyst warm-up judging means judges the warm-up condition of the catalyst based on the elapsed time after the engine starts.
In other words, the catalyst warms up and the catalyst temperature rises with the passage of time after the engine is started.Therefore, if the warm-up condition of the catalyst is judged by the elapsed time after the engine is started, it is determined by the elapsed time after the engine is started. The catalyst warm-up control that indirectly estimates the temperature rise of the catalyst becomes possible.

Further, in the present invention, the temperature of the catalyst or the temperature information reflecting the catalyst temperature is detected by the temperature sensor, and the catalyst warm-up determination means is determined by the catalyst temperature detected directly or indirectly by the temperature sensor. Determine the warm-up condition of.

In the above-mentioned control according to the elapsed time after the start-up of claim 4, the catalyst warm-up effect is affected by the catalyst temperature at the start-up, but in claim 5, the catalyst temperature is detected directly or indirectly. Since the catalyst warm-up is controlled by the catalyst temperature, the catalyst warm-up effect is not affected by the catalyst temperature at the time of starting, and a stable catalyst warm-up effect can be obtained.

Further, according to a sixth aspect of the present invention, the bypass intake passage is provided in parallel with the mechanical drive type supercharger, and the bypass intake passage is opened while the supercharger is stopped so that the intake air is taken into the bypass intake air. A bypass opening / closing valve for supplying the internal combustion engine through a passage and a passage switching means for switching the exhaust gas recirculation passage between the upstream side and the downstream side of the supercharger, and the bypass opening / closing valve is closed during catalyst warm-up control. And driving the supercharger and switching the passage switching means to the downstream side of the supercharger to open the exhaust gas recirculation control valve, and control the fuel injection amount to the internal combustion engine to the rich side, During supercharging other than catalyst warm-up control, the bypass opening / closing valve is closed to drive the supercharger, and the passage switching means is switched to the upstream side of the supercharger to perform exhaust gas recirculation control, When not supercharged, stop the supercharger To discharge gas recirculation control by switching the passage switching means on the downstream side of the supercharger with opening the bypass opening and closing valve Te. Thus, by utilizing the exhaust gas recirculation passage, there are three controls: supply of secondary air to the exhaust system during catalyst warm-up control, exhaust gas recirculation control during supercharging, and exhaust gas recirculation control during non-supercharging. The mode can be appropriately changed to smoothly perform the operation.

Further, according to the present invention, when the catalyst warm-up determination means determines that the catalyst is not warmed up, the flow control valve is opened during driving of the supercharger so that a part of the supercharged air is discharged. The fuel is supplied to the upstream side of the catalyst through the communication passage and the fuel injection amount of the internal combustion engine is controlled to the rich side. As a result, the amounts of CO and HC in the exhaust gas can be increased, and these can be reacted with oxygen in the secondary air by the catalyst, and the heat of reaction can efficiently warm up the catalyst.

Further, in the eighth aspect, when the warm-up condition is lower than the lower limit temperature for promoting exhaust gas purification, the control by the catalyst warm-up control means is prohibited. That is, HC, CO in the catalyst
Since the catalyst warm-up control is executed after the temperature reaches the temperature at which the catalyst starts to react with oxygen, the catalyst can be warmed up more efficiently.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment of the present invention will be described below.
An embodiment will be described with reference to FIGS. First, the schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of an engine 11 which is an internal combustion engine, and an intake air temperature sensor 14 that detects an intake air temperature THA is attached to the air cleaner 13. An intake air amount sensor 1 for detecting the intake air amount QA is provided downstream of the air cleaner 13.
6, a throttle valve 16, and a throttle opening sensor 17 for detecting the throttle opening TH.

A mechanical drive type supercharger (hereinafter referred to as "supercharger") 18 is provided on the downstream side of the intake pipe 12, and the compressed air discharged from the supercharger 18 at the time of supercharging is surge tank 19. And each cylinder of the engine 11 is filled through the intake manifold 20.
Normally, this supercharger 18 is driven by the engine rotational force transmitted from the engine 11 via the belt transmission mechanism 32, and its driving / stopping depends on the engine load, and the electromagnetic clutch (hereinafter referred to as “S / It is switched by "C clutch".
The supercharging area where this supercharger 18 is driven is
Engine load (engine speed NE and intake air amount QA
Is a predetermined operation range or more, and during idle operation, which is a non-supercharging range, or when the load is light, the S / C clutch is released and the drive of the supercharger 18 is stopped. Then, in order to secure intake air in the non-supercharging region, a bypass intake passage 20 is provided in parallel with the supercharger 18, and a bypass opened in the middle of the bypass intake passage 20 while the supercharger 18 is stopped. On-off valve 21
(Solenoid valve) is provided.

A fuel injection valve 22 is attached to the intake manifold 20 of each cylinder. An ignition plug 23 is attached to each cylinder of the engine 11, and a high voltage current generated in an ignition circuit (not shown) is supplied to each ignition plug 23 via a distributor 24. The distributor 24 is provided with a rotation angle sensor 25 that outputs a pulse signal having a frequency corresponding to the engine speed NE and a cylinder discrimination sensor 26 that outputs a cylinder discrimination signal G for discriminating a specific cylinder. There is. A water temperature sensor 27 that detects the engine cooling water temperature THW is attached to the engine 11.

On the other hand, in the middle of the exhaust pipe 28 of the engine 11, a catalyst 29 such as a three-way catalyst for reducing harmful components (CO, HC, NOx, etc.) in the exhaust gas is provided, and the upstream side of this catalyst 29. In addition, an air-fuel ratio sensor 30 that outputs a linear air-fuel ratio signal according to the air-fuel ratio λ of the exhaust gas is provided. Further, the exhaust gas recirculation port 31 is provided on the upstream side of the catalyst 29.
Is formed, and the exhaust gas recirculation port 31 and the intake system are connected by an exhaust gas recirculation passage (hereinafter referred to as “EGR passage”) 33. In the middle of the EGR passage 33, an exhaust gas recirculation valve including an electromagnetic valve is formed. Control valve (hereinafter referred to as "EGR valve") 3
4 are provided.

Further, on the intake system side of the EGR passage 33, an electromagnetic three-way valve 35, which is a passage switching means, is provided, and one port a of the three-way valve 35 is connected to the surge tank 19 via a passage 36. The other port b is connected to the intake pipe 12 on the upstream side of the supercharger 18 via the passage 37. Thus, by switching the three-way valve 35, the communication destination on the intake system side of the EGR passage 33 can be switched between the surge tank 19 side (downstream side of the supercharger 18) and the upstream side of the supercharger 18. ing.

The outputs of various sensors such as the water temperature sensor 27 described above are read in the electronic control circuit 38 through the input port 39. The electronic control circuit 38 includes a CPU 40,
It is mainly composed of a microcomputer including a ROM 41, a RAM 42, a backup RAM 43, and the like.
The fuel injection amount and the ignition timing are calculated according to various engine control programs stored in the OM 41, and the injection signal TAU and the ignition signal are output according to the calculation result.
From the fuel injection valve 22 or an ignition circuit (not shown) to control the operation of the engine 11. Further, the electronic control circuit 3
8 is a supercharging region, a non-supercharging region, and a catalyst warm-up control region depending on the engine load and the warming-up condition of the catalyst 29, as will be described later.
It is divided into two control regions, and the supercharger 18, the bypass opening / closing valve 21, the three-way valve 35, and the EGR valve 34 are controlled in each control region as follows.

(1) Supercharging region (excluding catalyst warm-up control region) The supercharging region is the engine load (for example, engine speed N).
E, intake air amount QA) is a predetermined operating range or more, and for example, a supercharging region and a non-supercharging region are classified by a two-dimensional map having the engine speed NE and the intake air amount QA as parameters. In the supercharging region, the bypass opening / closing valve 21 is closed to drive the supercharger 18, compresses the intake air and sends it to each cylinder, and the three-way valve 35 is switched to the upstream side (passage 37 side) of the supercharger 18. , Suction negative pressure of the supercharger 18 to the EGR passage 3
The exhaust gas recirculation control is performed by controlling the opening degree of the EGR valve 34 while acting on No. 3. In this case, a part of the exhaust gas discharged from the engine 11 into the exhaust pipe 28 is recirculated in the route of the exhaust gas recirculation port 31 → EGR passage 33 → three-way valve 35 → passage 37 → intake pipe 12 → supercharger 18. To do.

(2) Non-supercharging area During idle operation, which is in the non-supercharging area, and when the load is light, the engine torque is small. Therefore, the supercharger 18 is stopped and the bypass opening / closing valve 21 is opened to open the inside of the intake pipe 12. The flowing intake air is caused to flow into the surge tank 19 through the bypass intake passage 20, and the three-way valve 35 is switched to the surge tank 19 side (downstream side of the supercharger 18) so that the negative suction pressure of the surge tank 19 acts on the EGR passage 33. While controlling the exhaust gas recirculation control, the opening degree of the EGR valve 34 is controlled. In this case, part of the exhaust gas is exhaust gas recirculation port 31 → EGR passage 33 → three-way valve 35 → passage 36.
→ Return to the surge tank 19 route.

(3) Catalyst warm-up control area This catalyst warm-up control area is set as follows in the supercharging area. The catalyst 29 is determined to be in the unwarmed state until the elapsed time after the completion of the engine start reaches the predetermined time.
However, even if it is determined that the engine is not warmed up, the engine torque is small in the non-supercharging region, so the catalyst warm-up control is on standby until the supercharging region is reached. Therefore, the period in which the catalyst 29 is determined to be in the unwarmed state in the supercharging region is the catalyst warm-up control region.

In this catalyst warm-up control region, the three-way valve 35 is switched to the surge tank 19 side (downstream side of the supercharger 18) so that the supercharging pressure (discharge pressure of the supercharger 18) acts on the EGR passage 33. EGR valve 3
Open 4. As a result, the pressure (supercharging pressure) on the intake system side of the EGR passage 33 becomes higher than the pressure (exhaust pressure) on the exhaust pipe 28 side, and compressed air (supercharging air) sent from the supercharger 18 into the surge tank 19 is supplied. ) Partly flows back in the path of the passage 36, the three-way valve 35, the EGR passage 33, and the exhaust gas recirculation port 31, and is supplied as secondary air to the upstream side of the catalyst 29 in the exhaust pipe 28. At the same time, the fuel injection amount of each fuel injection valve 22 is increased and corrected, the air-fuel ratio of the mixed gas supplied to each cylinder of the engine 11 is controlled to be rich, and CO and HC in the exhaust gas are increased. Is reacted with oxygen in the secondary air by the catalyst 29, and the heat of the reaction efficiently warms up the catalyst 29. In the following description, the supercharging region and the non-supercharging region excluding the catalyst warm-up control region are called normal control regions.

The control of each area described above is executed by each program shown in FIG. 2 and subsequent figures. The base routine shown in FIG. 2 is executed by interrupt processing every 4 ms, for example. When the electronic control circuit 38 is powered on and this base routine is started, an initialization process is first performed in step 100 to initialize the RAM 42 and the like. This initialization process is executed only when the power is turned on. And the next step 20
At 0, the catalyst warm-up control region determination routine of FIG. 3 described later is executed to determine whether the current operating region is the catalyst warm-up control region or the normal control region. Then, in step 300, the fuel injection control routine of FIG. 5 described later is executed to calculate the fuel injection amount TAU. At this time, the fuel increase coefficient FSC for catalyst warm-up control is also calculated.

At the next step 400, the three-way valve control routine of FIG. 7 to be described later is executed to execute the supercharging region, non-supercharging region,
The three-way valve 35 is switched according to the catalyst warm-up control region.
Then, in the next step 500, the EG of FIG.
The R valve control routine is executed to switch the three-way valve 35 in step 400, and at the same time, the opening degree of the EGR valve 34 in the state at that time is controlled to control the exhaust gas recirculation amount or the secondary air amount. Then, in the next step 600,
The S / C clutch control routine of FIG. 11 to be described later is executed to control ON / OFF of the electromagnetic clutch (S / C clutch) of the supercharger 18. Then, in step 700, a bypass opening / closing valve control routine of FIG. 12 described later is executed to control opening / closing of the bypass opening / closing valve 21.

Next, the process flow of the catalyst warm-up control region determination routine executed in step 200 of FIG. 2 will be described with reference to the flowchart of FIG. This routine functions as catalyst warm-up determination means and low-warm engine control prohibition means in the claims, and is executed by interrupt processing every 40 ms, for example. In this routine, first in step 201,
The cooling water temperature THW detected by the water temperature sensor 27 is the drive lower limit temperature T1 of the supercharger 18 (for example, 20
° C) or more. Here, the drive lower limit temperature T1
Is a lower limit temperature at which the drivability is not deteriorated even if the supercharger 18 is driven if the temperature is higher than this temperature. It is determined whether THW is lower than the complete warm-up temperature T2. Here, the complete warm-up temperature T2 is a temperature at which both the catalyst 29 and the engine 11 are determined to be in the complete warm-up state, and above T2, it is not necessary to warm up the catalyst 29.

Therefore, only when T1≤THW <T2,
In order to determine the catalyst warm-up control region, the routine proceeds to step 203, where it is determined whether or not the start is completed depending on whether or not the engine speed NE has reached 500 rpm. If the start is completed (NE
≧ 500 rpm), the post-start elapsed time counter CSTA (corresponding to the time counting means) is incremented in step 204, and in the following steps 205 and 206, the value of the post-start elapsed time counter CSTA is α1 <CSTA ≦ α2. Or not. Here, α1 is the time required for the catalyst temperature to rise to the lower limit temperature TG1 for promoting the reaction between CO and HC in the exhaust gas and oxygen in the secondary air due to the heat of the exhaust gas. Further, α2 is the time required for the catalyst temperature to rise to the activation temperature TG2 by the catalyst warm-up control.

By the above processing, T1≤THW <T
2. Only when all the conditions of NE ≧ 500 rpm and α1 <CSTA ≦ α2 are satisfied, the routine proceeds to step 207, where the catalyst non-warm determination flag FLG1 is set to “1” indicating the catalyst non-warm section. If any of the above conditions is not satisfied, at step 214, the catalyst non-warm-up determination flag FLG
1 is reset to "0". If THW <T1,
Or, if NE <500 rpm, then step 213
Then, the post-start elapsed time counter CSTA is reset to "0". If THW ≧ T2, or CSTA> α
In the case of 2, in order to prevent the post-start elapsed time counter CSTA from overflowing, the value of the post-start elapsed time counter CSTA is set to "α2 + 1" in step 217.

When the catalyst non-warm-up determination flag FLG1 = 1 (catalyst non-warm-up section), the routine proceeds to steps 208 and 209, and the engine speed NE output from the rotation angle sensor 25 and the intake air amount sensor 14 respectively. The intake air amount QA is read, and in the following step 210, the S / C clutch ON / OFF command value CSC when the catalyst is not warmed up is calculated based on the NE and QA information (that is, whether the operating region is the supercharging region or the non-charging region). Determine whether it is a supercharging area) Here, a CSC map dedicated to catalyst non-warming (see Fig. 4) different from the CSC map for normal control is used. This CSC map dedicated to catalyst non-warming is used on the low load side (small intake air amount) in the supercharging region. Side and engine speed lower side). In addition, S / C clutch ON / O
The value of the FF command value CSC is either "1" which means S / C clutch ON or "0" which means S / C clutch OFF.

Then, in the next step 211, it is determined whether or not CSC is "1" which means S / C clutch ON, and if CSC = 1, it is determined to be in the supercharging region, and step 212 Then, the catalyst warm-up control execution flag FLG2 is set to "1" indicating the catalyst warm-up control execution, and this routine ends. On the other hand, in step 211, CSC =
When it is 0 (S / C clutch OFF), it is determined to be in the non-supercharging region, the catalyst warm-up control execution flag FLG2 is set to "0" indicating the catalyst warm-up control prohibition, and this routine is ended.

On the other hand, when the catalyst non-warm-up determination flag FLG1 is "0", the routine proceeds to step 215, where the catalyst warm-up control execution flag FLG2 is set to "0" indicating the catalyst warm-up control prohibition.
In step 216, the normal S / C clutch control is executed to set the engine speed NE and the intake air amount Q.
Based on A, the S / C clutch ON / OFF command value CSC is calculated (that is, it is determined whether the operating region is the supercharging region or the non-supercharging region). At this time, the calculation of CSC is CS for normal control.
A C map (not shown) is used.

Next, the processing flow of the fuel injection control routine executed in step 300 of FIG. 2 will be described with reference to the flowchart of FIG. This routine is executed, for example, every 180 ° C. First, in steps 301 and 302, the engine speed NE and the intake air amount QA are read, and in the next step 303, the basic fuel injection amount TP is calculated based on the NE and QA. calculate. Thereafter, in step 304, it is determined whether the catalyst warm-up control execution flag FLG2 is set to "1" indicating the catalyst warm-up control execution, and if FLG2 = 1 (catalyst warm-up control execution), Proceeding to step 305, the catalyst warm-up increase coefficient FSC is calculated. This catalyst warm-up increase factor F
SC is calculated by the FSC calculation table shown in FIG.
As the engine speed NE increases, the catalyst warm-up increase factor F
SC becomes large.

Then, in the next step 306, the feedback correction coefficient FAF for feedback controlling the air-fuel ratio to the stoichiometric air-fuel ratio (excess air ratio λ = 1) according to the signal from the air-fuel ratio sensor 30 is set to "1.0". , And in the next step 307, the final injection amount TAU is calculated by the following equation and the present routine is ended. TAU = TP * FSC * FC * FAF + TV Here, TP is a basic injection amount, FSC is a catalyst warm-up increase coefficient, FC is a basic injection quantity correction coefficient, FAF is a feedback correction coefficient, and TV is an invalid injection time.

On the other hand, if the catalyst warm-up control execution flag FLG2 = 0 (catalyst warm-up control prohibited) in step 304, the process proceeds to step 308, and the catalyst warm-up increase coefficient FSC is set to "1.0". Then, the final injection amount TAU is calculated by the above equation, and this routine is ended.

Next, the processing flow of the three-way valve control routine executed in step 400 of FIG. 2 will be described with reference to the flowchart of FIG. This routine functions as a switching control unit in the claims and is executed by interrupt processing every 40 ms, for example. In this routine, first, at step 401, it is judged if the S / C clutch ON / OFF command value CSC is “1” indicating the S / C clutch ON, and if CSC = 1 (supercharging region). Step 40
In step 2, it is determined whether the catalyst warm-up control execution flag FLG2 is "1" indicating the catalyst warm-up control execution. If F
If LG2 = 1 (execution of catalyst warm-up control), step 4
03, set the three-way valve control flag SVAL to "1", and set the three-way valve 35 to the surge tank 19 side (port a,
c communication), and the downstream side of the supercharger 18 and the exhaust pipe 28 side are communicated with each other through the EGR passage 33. As a result, the supercharging pressure (the discharge pressure of the supercharger 18) acts on the EGR passage 33 from the surge tank 19, so that the pressure on the intake system side of the EGR passage 33 is higher than the pressure on the exhaust pipe 28 side (exhaust pressure). And part of the supercharged air is shown in Fig. 8.
From the surge tank 19 to the passage 3 as indicated by the solid arrow.
6, EGR passage 33 through the ports a and c of the three-way valve 35
Is supplied to the upstream side of the catalyst 29 in the exhaust pipe 28 as secondary air.

On the other hand, CSC = 1 (S / C clutch ON:
Supercharging area) and FLG2 = 0 (catalyst warm-up control prohibited)
In the case of, the process proceeds to step 404, the three-way valve control flag SVAL is set to “0”, the three-way valve 35 is switched to the upstream side of the supercharger 18 (communication with ports b and c), and the upstream side of the supercharger 18 is connected. And the exhaust pipe 28 side are communicated with each other through the EGR passage 33. As a result, the negative suction pressure of the supercharger 18 acts on the EGR passage 33, and the exhaust gas recirculation gas (EGR gas) passes from the exhaust pipe 28 side through the EGR passage 33 and the passage 37 as shown by the one-dot chain line arrow in FIG. Is sucked into the supercharger 18.

In step 401, CSC = 0
In the case of (S / C clutch OFF: non-supercharging region), the routine proceeds to step 403, where the three-way valve control flag SVAL is set to "1" and the three-way valve 35 is connected to the surge tank 19 side (ports a and c communication). ), And the surge tank 19 on the downstream side of the supercharger 18 and the exhaust pipe 28 side are set to E
Communication is made through the GR passage 33. During this non-supercharge,
Surge tank 19 with supercharger 18 stopped
Since the inside is negative pressure, the pressure on the intake system side of the EGR passage 33 becomes lower than the pressure on the exhaust pipe 28 side (exhaust pressure), and when the EGR valve 34 is opened, it is shown by a dotted arrow in FIG. Thus, the EGR gas is introduced into the surge tank 19 from the exhaust pipe 28 side through the EGR passage 33 and the passage 36.

Next, E executed in step 500 of FIG.
The processing flow of the GR valve control routine will be described with reference to the flowchart of FIG. This routine is executed by interrupt processing every 4 ms, for example, and first, steps 501 and 502 are executed.
Then, the engine speed NE and the intake air amount QA are read.
In the following step 503, the catalyst warm-up control execution flag FLG
2 is "1" indicating execution of catalyst warm-up control, and if FLG2 = 1, the process proceeds to step 504, and FIG.
The secondary air control map shown in 0 is searched, and the required secondary air amount tSAir is calculated from the map based on the engine speed NE and the intake air amount QA (step 50).
5).

That is, during execution of the catalyst warm-up control, the fuel injection amount is increased to richly control the air-fuel ratio of the mixed gas to increase CO and HC in the exhaust gas. The secondary air amount tSAir containing oxygen required for the oxidation reaction at the engine speed NE and the intake air amount Q
It is calculated by converting the opening of the EGR valve 34 based on A (step 505), and this EGR valve opening tSAir is calculated as the target EGR.
The valve opening degree SEGR is stored in the memory (step 50).
6). Thereafter, in step 507, the target EGR valve opening degree S
The EGR signal is output to the EGR valve 34, and the EGR valve 34 is driven to the position of the target EGR valve opening degree SEGR.

On the other hand, FLG2 = 0 in step 503.
If (catalyst warm-up control is prohibited), steps 508 and 50
9. If the catalyst non-warm-up determination flag FLG1 = 1 (catalyst non-warm-up section), or if FLG1 = 0, the cooling water temperature THW is reached.
<In the case of the complete warm-up temperature T2, it is determined that the driveability failure occurs when the EGR control is performed, and the process proceeds to step 517, where “0” is stored in the memory of the target EGR valve opening SEGR, and the EGR is performed. The valve 34 is fully closed (step 507) to prohibit the EGR control.

On the other hand, when FLG1 = 0, the cooling water temperature TH
When W ≧ full warm-up temperature T2, the routine proceeds to step 510, where it is determined whether or not the supercharging region is based on whether CSC = 1 (S / C clutch is ON). In step 511, a supercharging EGR map (not shown) similar to that in FIG. 10 is searched, and the EGR amount during supercharging is calculated from the map to the optimum EGR amount (NO _X reduction without deteriorating drivability and emission. The EGR valve opening degree tPEgr for controlling the EGR amount to maximize the effect) is calculated (step 512), and this EGR valve opening degree tPEgr is stored in the memory of the target EGR valve opening degree SEGR (step 51).
3).

In step 510, CSC = 0
If it is determined that (S / C clutch OFF: non-supercharging region), the process proceeds to step 514, where a non-supercharging EGR map (not shown) similar to that in FIG. The EGR valve opening tNEgr for controlling the EGR amount during supercharging to the optimum EGR amount is calculated (step 515),
This EGR valve opening tNEgr is set to the target EGR valve opening SEG
Store in R's memory (step 516).

As described above, the target E is set for each control area.
After storing the GR valve opening degree SEGR, the signal of the target EGR valve opening degree SEGR is output to the EGR valve 34, and the EGR valve 34 is driven to the position of the target EGR valve opening degree SEGR (step 507), and this routine is executed. To finish.

Next, S executed in step 600 of FIG.
The processing flow of the / C clutch control routine will be described with reference to the flowchart of FIG. This routine functions as supercharger control means in the claims, and is 40 m, for example.
It is executed by interrupt processing every s. In this routine, first, at step 601, CSC = 1 (S / C clutch O
N), it is determined whether or not it is in the supercharging region. If it is in the supercharging region, the process proceeds to step 602 and the S / C clutch is turned on.
N to drive the supercharger 18. Meanwhile, CS
If C = 0 (S / C clutch OFF: non-supercharging region), the routine proceeds to step 603, where the S / C clutch is turned OFF and the supercharger 18 is stopped.

Next, the flow of processing of the bypass opening / closing valve control routine executed in step 700 of FIG. 2 will be described with reference to the flowchart of FIG. This routine is, for example, 40
It is executed by interrupt processing every ms, and first, step 701.
Then, it is determined whether CSC = 1 (S / C clutch is ON) or not in the supercharging region. If it is in the supercharging region, the routine proceeds to step 702, where the bypass on-off valve control signal VBY is closed. The bypass on-off valve 21 is closed in step 703. On the other hand, if CSC = 0 (S / C clutch OFF: non-supercharging region), the routine proceeds to step 704, where the bypass opening / closing valve control signal VBY is set to “1” indicating opening, and at the following step 705, bypass opening / closing is performed. Open the valve 21.

An example of performing the above-described control will be described with reference to the time charts of FIGS. 13 and 14. First, FIG. 13 is a time chart showing the operation from the engine start to the end of the catalyst warm-up control. After the engine starts, when the engine speed NE reaches 500 rpm, it is determined that the start is completed, and the post-start elapsed time counter CSTA is incremented from that point. Then, a period from a time α1 estimated that the catalyst temperature reaches the first predetermined temperature TG1 to a time α2 estimated to reach the second predetermined temperature TG2 (α1 <CSTA ≦ α
In 2), it is determined that the catalyst is not warmed up, and the catalyst non-warm determination flag FLG1 is set to "1". Here, TG1 is the catalyst warm-up control lower limit temperature for effectively operating the catalyst warm-up control, and TG2 is the activation temperature of the catalyst 29.

Next, when the catalyst is not warmed up (FLG1 = 1), it is determined whether or not the driveability and emission are not impaired even if the supercharger 18 is operated; If it is in the supply range, the catalyst warm-up control execution flag FLG2 is set to "1".
As a result, the bypass opening / closing valve 21 is closed to drive the supercharger 18, and the three-way valve 35 is closed.
Switch to the side to execute catalyst warm-up control. During the catalyst warm-up control, a part of the supercharged air flows backward from the surge tank 19 through the passage 36 in the EGR passage 33 and is supplied as secondary air to the upstream side of the catalyst 29 in the exhaust pipe 28. At the same time, the catalyst warm-up increase coefficient FSC is set to a value larger than 1.0 to richly control the fuel injection amount, and C in the exhaust gas is controlled.
O and HC are increased, and they are reacted with oxygen in the secondary air by the catalyst 29, and the heat of reaction heats the catalyst 29 efficiently. During this catalyst warm-up control, the air-fuel ratio of the exhaust gas is λ
The secondary air amount is calculated so that = 1 and the opening degree of the EGR valve 34 is controlled.

Thereafter, the post-start elapsed time counter CSTA
When the value of α reaches α2, it is determined that the catalyst warm-up is complete, and FL
Both G1 and FLG2 are reset to "0", and then normal control is performed.

On the other hand, FIG. 14 shows a three-way valve 35, a bypass opening / closing valve 21, an EGR valve during catalyst warm-up control and during supercharging / non-supercharging.
6 is a time chart showing the operation of the valve 34, which will be described below.

Immediately after starting the engine, the supercharger 18 is not driven, the bypass opening / closing valve 21 is opened, and the three-way valve 35 is switched to the downstream side of the supercharger 18 (the surge tank 19 side). Is fully closed and the EGR passage 33 is shut off. After that, when the catalyst warm-up control execution flag FLG2 is set to "1", the bypass opening / closing valve 21 is closed, the supercharger 18 is driven, and the catalyst warm-up control is started.
By opening the GR valve 41 and controlling the opening thereof, the amount of secondary air supplied to the exhaust pipe 28 side is controlled.

After that, when the catalyst warm-up is completed and both FLG1 and FLG2 are reset to "0", the control shifts to the normal control. At this time, the S / C clutch is ON (CSC =
Since the supercharger 18 is driven in 1),
Set the three-way valve 35 on the upstream side of the supercharger 18 (passage 3
7 side). However, since the cooling water temperature THW is equal to or lower than the complete warm-up temperature T2 at this point, the EGR valve 3
Fully close 4. This is because EGR control is prohibited so that drivability and emission do not deteriorate when THW ≦ T2. After that, when the cooling water temperature THW becomes equal to or higher than the complete warm-up temperature T2, the EGR control is permitted, and the opening degree of the EGR valve 34 is controlled based on the supercharging EGR control. At this time, the EGR gas is introduced upstream of the supercharger 18.

After that, the S / C clutch is turned off (CSC
= 0) and the supercharger 18 is stopped, the control becomes the same as that of the naturally aspirated engine, the bypass opening / closing valve 21 is opened, and the intake air flowing through the intake pipe 12 flows into the surge tank 19 through the bypass intake passage 20. At the same time, the three-way valve 35 is switched to the downstream side of the supercharger 18, and the EGR gas is recirculated through the EGR passage 33 → three-way valve 35 → passage 36 → surge tank 19.

According to the first embodiment described above, at the time of catalyst warm-up control, the supercharging pressure of the supercharger 18 and the EGR passage 33 are used to cause a part of the supercharging air to flow backward through the EGR passage 33 so as to be secondary. Since air can be supplied to the exhaust pipe 28 side, a dedicated secondary air supply device as in the prior art is unnecessary, and catalyst warm-up can be efficiently performed without complicating the configuration. Moreover, since the supercharging region is expanded when it is determined that the catalyst has not been warmed up, the catalyst warming control region can be expanded and the catalyst warming function can be improved.

When expanding the supercharging area, the engine 1
The engine speed may be increased against the drive load of the supercharger 18 applied to the engine 1. For example, when the catalyst is not warmed up, the idle speed is increased to increase supercharging even during idling. It may be set to a region (catalyst warm-up control region). However, the present invention may be configured such that the supercharging region is not changed, and even in this case, the intended purpose of the present invention can be sufficiently achieved.

In the first embodiment, the catalyst warm-up control region is determined based on the elapsed time after the start, which is measured by the post-start elapsed time counter CSTA. Therefore, the catalyst warm-up control is performed according to the catalyst temperature at the engine start. It is inevitable that the catalyst temperature at the time of completion will change somewhat.

Therefore, in the second example of the embodiment of the present invention shown in FIGS. 15 and 16, a catalyst temperature sensor 45 is attached to the catalyst 29, and the catalyst temperature sensor 45 directly detects the catalyst temperature and detects it. The catalyst unwarmed state is determined based on the temperature. The determination of the catalyst non-warm state is performed according to the flowchart shown in FIG. FIG. 16 shows the changes of FIG. 3 used in the first embodiment, and the processing of steps 205 and 206 in FIG.
Steps 204, 213 and 2 for changing to the processing of 05a and 206a and processing of the post-start elapsed time counter CSTA
17 is deleted, and the other steps are the same as those in FIG.

In this routine, steps 201-203
When the cooling water temperature THW is T1 or more and less than T2 and the engine speed NE is 500 rpm or more, step 2
In step 05a, it is determined whether the catalyst temperature THG detected by the catalyst temperature sensor 45 is higher than the catalyst warm-up control lower limit temperature TG1 for effectively operating the catalyst warm-up control. If THG ≦ TG1, in order to prohibit catalyst warm-up control, the routine proceeds to step 214, where the catalyst non-warm determination flag FLG1 is reset to “0”. If THG> TG1 is determined in step 205a, the process proceeds to step 206a, where the catalyst temperature THG is the activation temperature TG2.
It is determined whether or not: If THG> TG2, it is determined that the catalyst warm-up is completed, the process proceeds to step 214, and the catalyst non-warm-up determination flag FLG1 is reset to "0". If it is determined in step 206a that THG ≦ TG2, it is determined that the catalyst is not warmed up, and step 207
Then, the catalyst non-warm-up determination flag FLG1 is set to "1". The subsequent processing is the same as the processing shown in FIG.

In the second embodiment described above, since the catalyst temperature is detected by the catalyst temperature sensor 45, the catalyst temperature in the catalyst warm-up control region is not affected by the catalyst temperature at the engine start, and the catalyst warm-up is stable. The effect is obtained.

In the second embodiment, the catalyst temperature is directly detected by the catalyst temperature sensor 45, but temperature information reflecting the catalyst temperature, for example, engine cooling water temperature, exhaust temperature, air-fuel ratio sensor 30 element is used. The catalyst temperature may be indirectly detected based on the output signals of various temperature sensors (water temperature sensor 27, exhaust gas temperature sensor, element temperature sensor, heater temperature sensor, etc.) that detect temperature, heater temperature, and the like.

Further, in the first embodiment, the predetermined times α1 and α2 for determining the catalyst non-warm section may be corrected according to the cooling water temperature at the engine start. With this configuration, it is possible to accurately estimate the catalyst temperature based on the elapsed time after the start.

Next, as a third example of the embodiment of the present invention, as shown in FIG. 17, via a communication passage 46 that connects the downstream of the supercharger 18 and the upstream of the catalyst 29.
An example of supplying a part of the supercharged air to the catalyst 29 when the catalyst is not warmed up will be described.

The operation of the flow control valve 47 and the bypass opening / closing valve 21 in the three operating regions of the supercharging region (excluding the catalyst warm-up control), the non-supercharging region and the catalyst warm-up control region will be described below. .

First, in the supercharging region except during the catalyst warm-up control, the bypass opening / closing valve 21 and the flow rate control valve 47 are closed and the supercharger 18 is driven to compress the intake air and send it to each cylinder. Next, in the non-supercharging region, the drive of the supercharger 18 is stopped, the bypass opening / closing valve 21 is opened, and the flow rate control valve 47 is closed. At this time, the intake air passes through the bypass opening / closing valve 21 and the surge tank 19
Flows into.

Finally, in the catalyst warm-up control area, the supercharger 18 is driven, the bypass opening / closing valve 21 is closed, and the flow rate control valve 47 is opened. As a result, a part of the supercharged air is supplied as secondary air to the upstream side of the catalyst via the communication passage 46, and the warm-up of the catalyst 29 is promoted. In addition,
At this time, the fuel injection amount is increased in accordance with the amount of air supplied through the communication passage 46 as in the above-described embodiments.
It should be noted that this catalyst warm-up control is similar to that of the first embodiment.
The warm-up condition of 9 is executed until the activation temperature is reached after the temperature has risen to the lower limit temperature for promoting exhaust gas purification.

As described above, even if the flow path for supplying a part of the supercharged air as the secondary air is not the EGR passage 37,
If the communication passage 46 that connects the downstream side of the supercharger and the upstream side of the catalyst and the flow rate control valve 47 are provided, the same control as in the first and second embodiments can be executed, and the same effect can be obtained.

The flow rate control valve 47 may be an open / close valve that opens / closes the communication passage 46 or a valve that can linearly control the opening.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an engine control system showing a first example of an embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of processing of a base routine.

FIG. 3 is a flowchart showing a processing flow of a catalyst warm-up control region determination routine.

FIG. 4 is a diagram conceptually showing a CSC map when the catalyst is not warmed up.

FIG. 5 is a flowchart showing a flow of processing of a fuel injection control routine.

FIG. 6 is a graph showing the engine speed NE to the catalyst warm-up increase coefficient FS.
The figure which shows notionally the table which calculates C

FIG. 7 is a flowchart showing a processing flow of a three-way valve control routine.

FIG. 8 is a diagram illustrating the flow of EGR gas or secondary air in each control region.

FIG. 9 is a flowchart showing a processing flow of an EGR valve control routine.

FIG. 10 is a diagram conceptually showing a map for calculating a secondary air amount tSAir from an engine speed NE and an intake air amount QA.

FIG. 11 is a flowchart showing a processing flow of an S / C clutch control routine.

FIG. 12 is a flowchart showing a processing flow of a bypass opening / closing valve control routine.

FIG. 13 is a time chart showing the behavior of catalyst warm-up control.

FIG. 14 is a time chart showing the behavior of a three-way valve, a bypass opening / closing valve, and an EGR valve.

FIG. 15 is a schematic configuration diagram of an engine control system showing a second example of the embodiment of the present invention.

FIG. 16 is a flowchart showing the flow of processing of the main part of the catalyst warm-up control region determination routine of the second embodiment.

FIG. 17 is a schematic configuration diagram of an engine control system showing a third example of the embodiment of the present invention.

[Explanation of symbols]

11 ... Engine (internal combustion engine), 12 ... Intake pipe, 15 ... Intake amount sensor, 18 ... Supercharger (supercharger), 1
9 ... Surge tank, 20 ... Bypass intake passage, 21 ... Bypass opening / closing valve, 25 ... Rotation angle sensor, 27 ... Water temperature sensor,
28 ... Exhaust pipe, 29 ... Catalyst, 30 ... Air-fuel ratio sensor, 31
Exhaust gas recirculation port, 33 ... EGR passage (exhaust gas recirculation passage), 34 ... EGR valve (exhaust gas recirculation control valve), 35 ...
Three-way valve (passage switching means), 36, 37 ... Passage, 38 ... Electronic control circuit (supercharger control means, catalyst warm-up determination means, catalyst warm-up control means, switching control means, timing means), 45 ... Catalyst temperature Sensor, 46 ... Communication passage, 47 ... Flow control valve.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location F02D 43/00 301 F02D 43/00 301N 301H 45/00 360 45/00 360C F02M 25/07 550 F02M 25/07 550R 570 570P

Claims (8)

[Claims] 1. A catalyst for purifying exhaust gas provided in an exhaust system, an exhaust gas recirculation passage for recirculating a part of exhaust gas from an upstream side of the catalyst to an intake system, and an exhaust gas flowing through the exhaust gas recirculation passage. In an exhaust gas purifying apparatus for an internal combustion engine, comprising an exhaust gas recirculation control valve for adjusting the amount of gas and a supercharger provided in an intake system, it is determined whether or not the operating state of the internal combustion engine is in a supercharging region. A supercharger control means for controlling the drive / stop of the supercharger, a catalyst warm-up determination means for determining the warm-up state of the catalyst, and a catalyst warm-up state determined by the catalyst warm-up determination means. When it is determined that the exhaust gas recirculation control valve is opened while the supercharger is being driven, a part of the supercharged air is supplied to the exhaust system by flowing back through the exhaust gas recirculation passage and to the internal combustion engine. Catalyst warm-up control that controls the fuel injection amount of fuel to the rich side An exhaust gas purifying apparatus for an internal combustion engine, comprising: a control means. 2. The supercharger control means expands the supercharge region when the catalyst warm-up determination means determines that the catalyst is not warmed up. Exhaust gas purification device for internal combustion engine. 3. A passage switching means for switching the exhaust gas recirculation passage between an upstream side and a downstream side of the supercharger, and the passage switching means for the supercharger during catalyst warm-up control and non-supercharging. 3. The switching control means for switching to the downstream side and switching the passage switching means to the upstream side of the supercharger during supercharging other than during catalyst warm-up control. Exhaust gas purification device for internal combustion engine. 4. The catalyst warm-up determining means comprises a clocking means for clocking an elapsed time after the engine is started, and the catalyst warm-up determining means determines the warm-up condition of the catalyst based on the clocking time of the clocking means. The exhaust gas purifying apparatus for an internal combustion engine according to any one of 1 to 3. 5. A temperature sensor for detecting the temperature of the catalyst or temperature information reflecting the catalyst temperature, wherein the catalyst warm-up determination means determines whether the catalyst temperature of the catalyst is directly or indirectly detected by the temperature sensor. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the degree of warm-up is determined. 6. A catalyst for purifying exhaust gas provided in an exhaust system, an exhaust gas recirculation passage for returning a part of exhaust gas from an upstream side of the catalyst to an intake system, and provided in the exhaust gas recirculation passage. The exhaust gas recirculation control valve, the supercharger provided in the intake system, the bypass intake passage provided in parallel with the supercharger, the bypass intake passage provided in the bypass intake passage to stop the supercharger. A bypass opening / closing valve for opening the bypass intake passage to supply intake air to the internal combustion engine through the bypass intake passage, and a passage switching for switching the exhaust gas recirculation passage between an upstream side and a downstream side of the supercharger Means for controlling the catalyst warm-up, the bypass opening / closing valve is closed to drive the supercharger, and the passage switching means is switched to the downstream side of the supercharger to operate the exhaust gas recirculation control valve. Open and part of the supercharged air The exhaust gas recirculation passage is reversely flown to supply to the exhaust system, the fuel injection amount to the internal combustion engine is controlled to the rich side, and the bypass opening / closing valve is closed at the time of supercharging other than catalyst warm-up control To drive the supercharger and switch the passage switching means to the upstream side of the supercharger for exhaust gas recirculation control.When not supercharging, the supercharger is stopped and the bypass opening / closing valve is opened. And an exhaust gas recirculation control by switching the passage switching means to the downstream side of the supercharger to perform exhaust gas recirculation control. 7. An exhaust gas purifying apparatus for an internal combustion engine, comprising: an exhaust gas purifying catalyst provided in an exhaust system; and a supercharger provided in an intake system, wherein a downstream side of the supercharger and the catalyst are provided. A communication passage communicating with an upstream of the communication passage, a flow rate control valve controlling a flow rate of the communication passage, and determining whether the operating state of the internal combustion engine is in a supercharging region to control driving / stopping of the supercharger. And a catalyst warm-up determining means for determining the warm-up state of the catalyst, and driving the supercharger when the catalyst warm-up determining means determines that the catalyst is not warmed up. And a catalyst warm-up control means for opening the flow rate control valve to supply a part of the supercharged air to the upstream side of the catalyst through the communication passage and controlling the fuel injection amount of the internal combustion engine to the rich side. An exhaust gas purifying apparatus for an internal combustion engine, comprising: 8. A low-warm engine control inhibiting means for inhibiting the control by the catalyst warm-up control means when the catalyst warm-up determination means determines that the catalyst warm-up condition is lower than a lower limit temperature for promoting exhaust gas purification. An exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 7, characterized in that.