JP6535246B2 - Engine control unit - Google Patents

Description

  The present invention relates to an engine control apparatus for controlling an engine in which a catalytic converter is disposed downstream of a turbine of a turbocharger, and more particularly to an engine control apparatus in which the opening of a wastegate valve is optimized according to the deterioration state of a catalyst.

A turbocharger is a turbocharger that drives a turbine by the exhaust gas of the engine and compresses combustion air (fresh air) of the engine by a compressor connected to the turbine.
The turbocharger is provided with a waste gate valve that opens and closes a flow path for extracting a part of exhaust gas from the upstream side of the turbine and bypassing the downstream side of the turbine for the purpose of supercharging pressure control and the like.
When the engine is operated in the supercharging region, the waste gate valve is feedback-controlled so that the actual supercharging pressure approaches a target supercharging pressure set according to the driver's required torque or the like.

In an engine equipped with a turbocharger, a catalytic converter such as a three-way catalyst for purifying exhaust gas is usually provided on the downstream side (outlet side) of the turbine.
Therefore, the temperature in the layer of the catalytic converter depends on the temperature of the exhaust gas downstream of the turbine.
As a prior art related to opening control of a waste gate valve in consideration of the temperature of a catalytic converter, for example, Patent Document 1 discloses that the temperature of exhaust gas passing through the catalyst is a predetermined set time or more for the purpose of preventing thermal deterioration of the catalyst. It is described that the boost pressure is reduced by opening the waste gate valve when the temperature exceeds a predetermined set temperature.

Japanese Patent Application Laid-Open No. 11-287126

An engine equipped with a turbocharger tends to have a severe catalyst temperature-raising performance as compared with a naturally aspirated engine because a turbine having a relatively large heat capacity is present between the engine and the catalyst.
Therefore, the problem is how to reduce the influence of the heat capacity of the turbine to improve the catalyst temperature-raising performance and to improve the exhaust gas purification performance from immediately after the start up to after the completion of the warm-up.
On the other hand, in recent years, the electric waste gate valve which can set an opening degree arbitrarily using an electric actuator is spreading.
In an engine having such an electric waste gate valve, the waste gate valve is opened (normally open) and operated from the upstream side of the turbine at the time of operation in a relatively low load state where the boost pressure feedback control or the like does not intervene. By bypassing part of the exhaust gas to the side, it is possible to raise the exhaust gas temperature at the catalyst inlet and improve the temperature raising performance of the catalyst.

However, if exhaust bypass using a waste gate valve is performed, for example, if the boost pressure is improved according to an increase in driver request torque at the time of acceleration, the waste gate valve is transitioned (driven) from an open state to a closed state. Due to the time required for driving, the time response of the supercharging pressure is delayed, and drivability (ease of driving) is impaired.
In order to achieve both catalyst temperature rise performance and drivability, as long as the catalyst can maintain the activation temperature, the initial opening of the waste gate valve (initial opening in the state in which the supercharging pressure feedback control does not intervene) is reduced. It is preferable to set (in a state of closing).
However, since the exhaust gas purification performance of the catalyst deteriorates due to age deterioration etc., when the opening of the waste gate valve is optimized with respect to the catalyst at the time of new product, the temperature rise performance becomes insufficient when the catalyst deteriorates. Are concerned.
On the other hand, when the initial opening of the waste gate valve is set large (dearly open) so that the temperature rising performance can be maintained even when the catalyst is deteriorated, the drivability at the time of new catalyst is sacrificed. I will.
SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an engine control system in which the west gate valve opening degree is optimized in accordance with the deterioration state of the catalyst.

The present invention solves the above-mentioned problems by the following solutions.
The invention according to claim 1 is a turbocharger having a turbine driven by exhaust gas of an engine and a compressor driven by the turbine to compress combustion air, and one of the exhaust gas from the upstream side to the downstream side of the turbine Gate for bypassing the engine, a waste gate valve driven by an electric actuator to open and close the waste gate, a catalytic converter provided on the downstream side of the turbine for purifying the exhaust gas, the catalyst An engine control apparatus for controlling an engine including a catalyst deterioration diagnosis means for diagnosing a deterioration state of a converter, wherein the opening degree of the waste gate valve approaches a predetermined target charging pressure in a high load state. controlled by the supercharging pressure feedback control for controlling so, other than the high load condition A wastegate valve control means for controlling so that the constant initial opening, the initial opening degree setting means for setting large the initial opening in accordance with the progress of the deterioration of the catalytic converter is diagnosed by the catalyst deterioration diagnosis means And an engine control device characterized by comprising:
According to this, when the state of the catalyst is good, by setting the initial opening degree of the waste gate valve small, the catalyst temperature raising performance necessary for obtaining sufficient exhaust gas purification performance is ensured while securing And boost pressure response characteristics can be improved.
On the other hand, when deterioration of the catalyst progresses, the exhaust gas purification performance can be secured by raising the temperature of the catalyst to a higher temperature by setting the initial opening degree of the waste gate valve large.

The invention according to claim 2 is provided with warm-up completion determination means for determining the completion of warm-up of the catalytic converter, and the wastegate valve control means is configured to determine between the start of the engine and the completion of the warm-up. an engine control apparatus according to claim 1, characterized in that the total open state the waist gate valve regardless the initial opening.
According to this, the period from the start of the engine until the catalyst warm-up is completed by the wastegate valve to full open, fast catalyst temperature was raised by activation of the exhaust gas purification performance immediately after the start Can be improved.

  As described above, according to the present invention, it is possible to provide an engine control device in which the opening degree of the waste gate valve is optimized in accordance with the deterioration state of the catalyst.

FIG. 1 is a view schematically showing a configuration of an engine having an embodiment of an engine control device to which the present invention is applied. It is a figure which shows typically the catalyst degradation diagnostic method in the engine control system of an Example. It is a graph which shows an example of correlation with the catalyst degradation diagnostic value and HC purification rate in an Example. It is a flowchart which shows the waste gate valve-opening degree control in the engine control apparatus of an Example. It is a graph which shows an example of the correlation of the catalyst deterioration diagnostic value and initial opening degree in an Example, and correlation with initial opening degree and catalyst temperature. It is a graph which shows an example of transition of the exhaust gas temperature in the catalyst inlet at the time of making a west gate valve fully open and fully closed.

  The present invention provides an engine control apparatus in which the opening degree of the waste gate is optimized according to the deterioration state of the catalyst, and the initial opening degree in the state where the supercharging pressure control does not intervene in the waste gate valve. The problem is solved by changing the catalyst deterioration diagnostic value.

Hereinafter, an embodiment of an engine control device to which the present invention is applied will be described.
The engine control apparatus according to the embodiment is provided, for example, on a horizontally opposed four-cylinder gasoline direct injection turbocharged engine mounted as a power source for traveling in a car such as a passenger car, and controls the entire engine main body and accessories. It is

FIG. 1 is a view schematically showing a configuration of an engine having an engine control device according to a first embodiment.
The engine 1 is configured to include a crankshaft 10, a cylinder block 20, a cylinder head 30, a turbocharger 40, an intake system 50, an exhaust system 60, a canister 70, an engine control unit (ECU) 100, and the like.

The crankshaft 10 is a rotating shaft that is an output shaft of the engine 1.
A power transmission mechanism such as a transmission (not shown) is connected to one end of the crankshaft 10.
A piston is connected to the crankshaft 10 via a connecting rod (not shown).
At the end of the crankshaft 10, a crank angle sensor 11 for detecting the angular position of the crankshaft is provided.
The output of the crank angle sensor 11 is transmitted to the ECU 100.

The cylinder block 20 is configured as a two-piece so as to sandwich the crankshaft 10 from the left and right direction in vertical mounting on a vehicle body.
At the central portion of the cylinder block 20, there is provided a crankcase portion that accommodates the crankshaft 10 and has a main bearing that rotatably supports the crankshaft 10.
Inside the left and right banks of the cylinder block 20 disposed on the left and right sides of the crankcase portion, for example, a pair of cylinders (in the case of four cylinders) in which pistons are inserted and reciprocated inside are formed.

The cylinder head 30 is provided at each end (left and right end) of the cylinder block 20 opposite to the crankshaft 10.
The cylinder head 30 includes a combustion chamber 31, an ignition plug 32, an intake port 33, an exhaust port 34, an intake valve 35, an exhaust valve 36, an intake camshaft 37, an exhaust camshaft 38, and the like.
The combustion chamber 31 is formed by, for example, indenting a portion facing the piston crown surface of the cylinder head 30 into a pent roof shape.
The spark plug 32 is provided at the center of the combustion chamber 31, generates a spark in response to an ignition signal from the ECU 100, and ignites the air-fuel mixture.

The intake port 33 is a flow path for introducing combustion air (fresh air) into the combustion chamber 31.
The exhaust port 34 is a flow path for discharging the burned gas (exhaust gas) from the combustion chamber 31.
The intake valve 35 and the exhaust valve 36 open and close the intake port 33 and the exhaust valve 34 at predetermined valve timings.
For example, two intake valves 35 and two exhaust valves 36 are provided for each cylinder.
The intake valve 35 and the exhaust valve 36 are opened and closed by an intake camshaft 37 and an exhaust camshaft 38 which rotate in synchronization at a half rotation speed of the crankshaft 10.
The cam sprockets of the intake camshaft 37 and the exhaust camshaft 38 are provided with a variable valve timing mechanism (not shown) that changes the opening timing and closing timing of each valve by advancing and retarding the phase of each camshaft. It is done.

The turbocharger 40 is a supercharger that compresses combustion air (fresh air) using the energy of the exhaust of the engine 1 and supercharges it.
The turbocharger 40 includes a turbine 41, a compressor 42, an air bypass flow path 43, an air bypass valve 44, a waste gate flow path 45, a waste gate valve 46, and the like.
The turbine 41 is rotationally driven by the exhaust gas of the engine 1.
The compressor 42 is coaxially attached to the turbine 41 and rotationally driven by the turbine 41 to compress air.

The air bypass flow path 43 extracts a part of air from the downstream side of the compressor 42 and causes the air to flow back to the upstream side of the compressor 42.
The air bypass valve 44 is provided in the air bypass flow passage 43, and is in a closed state in which the air bypass flow passage 43 is substantially closed in response to a command from the ECU 100, and an open state where air can pass through the air bypass flow passage 43 And in two steps.
The air bypass valve 44 is an electric valve having a valve body that is opened and closed by an electric actuator.
The air bypass valve 44 is opened in order to prevent surging of the turbocharger 40, protect the blades, etc., for example, when the throttle valve 56 is suddenly closed, and the air in the intake pipe downstream of the compressor 42 is opened. Are returned to the upstream side of the compressor 42 to reduce the excess pressure.

The west gate channel 45 extracts a part of the exhaust gas from the upstream side of the turbine 41 and bypasses the downstream side of the turbine 41 for the purpose of supercharging pressure control, temperature rise of the catalyst, and the like.
The wastegate channel 45 is integrally formed in the housing of the turbine 41.
The waste gate valve 46 has a valve body provided in the waste gate flow path 45 for opening and closing the flow path, and controls the flow rate of exhaust gas passing through the waste gate flow path 45.
The waste gate valve 46 is an electric waste gate valve having an electric actuator that opens and closes the valve in accordance with a command from the ECU 100.
The west gate valve 46 can switch between the fully open state and the fully closed state, and can also set an arbitrary degree of opening at these intermediate positions.

The intake system 50 introduces air to the intake port 33.
The intake system 50 includes an intake duct 51, a chamber 52, an air cleaner 53, an air flow meter 54, an intercooler 55, a throttle valve 56, an intake manifold 57, an intake pressure sensor 58, an injector 59, and the like.

The intake duct 51 is a flow path for introducing outside air and introducing it to the intake port 33.
The chamber 52 is a space provided in communication with the vicinity of the inlet of the intake duct 51.
The air cleaner 53 is provided on the downstream side of the communication point of the intake duct 51 with the chamber 52, and filters air to remove dust and the like.
The air flow meter 54 is provided in the vicinity of the outlet of the air cleaner 53 and measures the flow rate of air passing through the intake duct 51.
The output of the air flow meter 54 is transmitted to the ECU 100.
The compressor 42 of the turbocharger 40 is provided downstream of the air flow meter 54.

The intercooler 55 is a heat exchanger that is provided on the downstream side of the compressor 42 in the intake duct 51 and that cools the air that has been compressed to a high temperature, for example, by heat exchange with traveling air or the like.
The throttle valve 56 is a butterfly valve which is provided on the downstream side of the intercooler 55 in the intake duct 51 and adjusts the flow rate of air to control the output of the engine 1.
The throttle valve 56 is driven to open and close by a throttle actuator (not shown) in response to an operation of an accelerator pedal (not shown) by the driver and the like.
Further, the throttle valve 56 is provided with a throttle sensor for detecting the opening degree, and the output thereof is transmitted to the ECU 100.
The intake manifold 57 is a branch pipe provided downstream of the throttle valve 56 and distributing the air to the intake port 33 of each cylinder.
The intake pressure sensor 58 detects the pressure of the air in the intake manifold 57 (intake pressure).
The output of the intake pressure sensor 58 is transmitted to the ECU 100.
The injector 59 is provided at an end of the intake manifold 57 on the cylinder head 30 side, and injects fuel into the combustion chamber 31 to form an air-fuel mixture according to a valve opening signal issued by the ECU 100.

The exhaust system 60 exhausts the exhaust gas exhausted from the exhaust port 34 to the outside.
Exhaust system 60 includes an exhaust manifold 61, exhaust pipe 62, the front catalyst 63, the rear catalyst 64, a silencer 65, the air-fuel ratio sensor 66 is configured to have a rear _{O 2} sensor 67 or the like.
The exhaust manifold 61 is a collecting pipe for collecting the exhaust gas emitted from the exhaust port 34 of each cylinder.
The turbine 41 of the turbocharger 40 is disposed downstream of the exhaust manifold 61.
The exhaust pipe 62 is a pipe line for discharging the exhaust gas emitted from the turbine 41 to the outside.
The front catalyst 63 and the rear catalyst 64 are provided at an intermediate portion of the exhaust pipe 62, and each include a three-way catalyst that purifies HC, NOx, CO and the like in the exhaust gas.
The three-way catalyst is configured, for example, by supporting a noble metal such as platinum, palladium, or rhodium on a carrier formed of a ceramic such as alumina.
The front catalyst 63 is provided adjacent to the outlet of the turbine 41, and the rear catalyst 64 is provided on the outlet side of the front catalyst.
The silencer 65 is provided in the vicinity of the outlet of the exhaust pipe 62 to reduce the acoustic energy of the exhaust gas.

The air-fuel ratio sensor 66 is provided between the outlet of the turbine 41 and the inlet of the front catalyst 63.
Rear O ₂ sensor 67 is provided between the inlet of the outlet and the rear catalyst 64 of the front catalyst 63.
Air-fuel ratio sensor 66, the rear O ₂ sensor 67 by generating an output voltage corresponding to both the oxygen concentration in the exhaust gas, and detects the amount of oxygen in the exhaust gas.
Air-fuel ratio sensor 66 is more a wide detectable linear output sensor oxygen concentration in the air-fuel ratio with respect to the rear O ₂ sensor 67.
Air-fuel ratio sensor 66, the output of the rear O ₂ sensor 67 is transmitted together ECU 100, the air-fuel ratio feedback control of the fuel injection amount, used in the catalyst deterioration diagnosis to be described later.

The canister (charcoal canister) 70 is one in which fuel evaporative gas (evaporative) generated in a fuel tank (not shown) in which gasoline used as fuel for the engine 1 is stored is introduced and temporarily stored.
The canister 70 is configured by housing activated carbon capable of temporarily adsorbing fuel evaporation gas in a canister case which is a resin case.

  The canister 70 mainly includes a non-supercharged purge line 71, a purge control valve 72, and a mainly supercharged purge line 73, a purge control valve 74, and the like.

The purge line 71 is a flow path which is connected to the canister 70 and the intake manifold 57 at both ends and which allows the insides to communicate with each other.
The purge line 71 introduces a purge gas composed of the fuel evaporation gas released from the canister 70 into the intake manifold 57 when the internal pressure of the intake manifold 57 is negative and not supercharged.
The purge control valve (PCV) 72 is a duty control solenoid valve provided in the middle of the purge line 71.
The PCV 72 can switch between an open state and a closed state, and set an opening degree in the open state, in accordance with a command from the ECU 100.

The purge line 73 is a flow path which is connected at both ends to the canister 70 and a region adjacent to the inlet of the compressor 42 in the intake duct 51 and allows the insides to communicate with each other.
The purge line 73 introduces the purge gas into the intake duct 51 on the upstream side of the compressor 42 at the time of supercharging in which the inside of the intake manifold 57 has a positive pressure and the introduction of the purge gas by the purge line 71 becomes difficult.
The purge control valve (PCV) 74 is a solenoid valve provided in the middle of the purge line 73.
The PCV 74 can switch between the open state and the closed state in response to a command from the ECU 100.

An engine control unit (ECU) 100 centrally controls the engine 1 and its accessories.
The ECU 100 is configured to include an information processing unit such as a CPU, a storage unit such as a RAM or a ROM, an input / output interface, a bus connecting these, and the like.
Further, the ECU 100 is provided with an accelerator pedal sensor 101 that detects the depression amount of an accelerator pedal (not shown) by the driver.
The ECU 100 has a function of setting the driver request torque based on the output of the accelerator pedal sensor 101 or the like.
The ECU 100 controls the throttle valve opening degree, the supercharging pressure, the fuel injection amount, the ignition timing, the valve timing, and the like so that the torque actually generated by the engine 1 approaches the set driver request torque.
The control of the supercharging pressure is performed by supercharging pressure feedback control that controls the waste gate valve 46 so that the actual supercharging pressure approaches the target supercharging pressure set by the ECU 100.

Further, the ECU 100 performs catalyst deterioration diagnosis means for diagnosing the deterioration state of the front catalyst 63, waste gate valve control means for controlling the opening degree of the waste gate valve 46, and the waste gate valve 46 according to the increase of the catalyst deterioration diagnosis value. It functions as an initial opening setting means for setting the initial opening of the large opening.
FIG. 2 is a view schematically showing a catalyst deterioration diagnosis method in the engine control device of the embodiment.
Catalyst deterioration diagnosis, the output value variation accumulated value of the air-fuel ratio sensor 66 on the upstream side of the front catalyst 63 for (waveform trajectory length), the output value variation amount integrated value of the downstream of the rear O ₂ sensor 67 (waveform locus length) This is performed by calculating the ratio of the catalyst as the catalyst deterioration diagnostic value.
As the catalyst deterioration diagnosis value, for example, may be a value of the output value variation amount accumulated value, obtained by dividing the output value variation amount integrated value of the air-fuel ratio sensor 66 of the rear O ₂ sensor 67.

Generally, the three-way catalyst temporarily stores O ₂ contained in the exhaust gas when the air-fuel ratio is lean or when the fuel is cut, etc., and also releases the stored O ₂ when the air-fuel ratio is rich or the like. Have.
In a new state where the catalyst is not substantially deteriorated, such an oxygen storage and release capacity is high, and absorbs fluctuations in the O ₂ introduction amount to some extent, so the output value fluctuation of the air-fuel ratio sensor 66 on the upstream side of the catalyst respect, the output value fluctuations in the downstream side of the rear O ₂ sensor 67 becomes small.
In contrast, if a catalyst is oxygen storage capability deteriorates decreases, the output value fluctuations of the rear O ₂ sensor 67 is larger relative to the output value variation of the air-fuel ratio sensor 66.
The above-described catalyst deterioration diagnosis value quantitatively diagnoses the deterioration state of the catalyst using such characteristics.

FIG. 3 is a graph showing an example of the correlation between the catalyst deterioration diagnosis value and the HC purification rate in the example.
As shown in FIG. 3, the HC purification rate decreases as the catalyst deterioration diagnosis value increases.
In order to maintain the HC purification rate equal to that of the undegraded catalyst, it is necessary to further raise the temperature of the catalyst by the catalyst whose diagnosis value for catalyst degradation has increased (deterioration has progressed).
Therefore, in the engine control device according to the embodiment, the initial opening degree (opening degree in the state of waiting for control command) of the waste gate valve 46 in the state where no other control such as boost pressure feedback control intervenes The increase is corrected according to the increase.
A more detailed description will be given below.

FIG. 4 is a flowchart showing the waste gate valve opening degree control in the engine control device of the embodiment.
Hereinafter, each step will be described in order.

<Step S01: Judgment of end of catalyst warm-up after start>
The ECU 100 determines whether the initial warm-up of the catalyst after the cold start of the engine 1 has ended.
The completion of catalyst warm-up is determined, for example, based on whether or not a preset catalyst warm-up termination condition is satisfied.
As the catalyst warm-up completion condition, for example, when the integrated intake air amount of the engine 1 after the start of the engine exceeds a preset threshold value, catalyst warm-up can be ended.
In addition, catalyst warm-up can be completed when an elapsed time after engine start exceeds a preset threshold.
In this case, these threshold values can be corrected to decrease according to the increase of the outside air temperature or the engine coolant temperature at the time of start.
If it is determined that the catalyst warm-up has ended, the process proceeds to step S03, and otherwise proceeds to step S02.

<Step S02: West gate valve fully open>
The ECU 100 maintains the waste gate valve 46 in the fully open state to maximize the flow rate of the exhaust gas bypassing the turbine 41 in order to prioritize the initial warm-up of the catalyst over the boost pressure response characteristic and the engine output.
Thereafter, step S01 is repeated.

<Step S03: Supercharging pressure feedback control intervention judgment>
The ECU 100 determines whether the boost pressure feedback control intervenes in the opening control of the waste gate valve 46.
The supercharging pressure feedback control is to control the supercharging pressure of the turbocharger 40 to approach a target supercharging pressure set according to the driver request torque and the like.
The supercharging pressure feedback control is mainly performed when the load of the engine 1 is in a high load state equal to or more than a predetermined level.
The supercharging pressure feedback control is started, for example, when the actual torque falls below the driver request torque even if the throttle valve 56 is fully opened in a state where the waste gate valve 46 is maintained at the initial opening degree.
If the supercharging pressure feedback control intervenes, the process proceeds to step S05. Otherwise, the process proceeds to step S04.

ＥＣＵ１００がウエストゲートバルブ４６の開度をイニシャル開度に設定した後、一連の処理を終了（リターン）する。 <Step S04: Initial opening degree according to catalyst deterioration diagnosis value>
The ECU 100 maintains the opening degree of the waste gate valve 46 at an initial opening degree set according to the catalyst deterioration diagnosis value.
The initial opening degree is substantially set to the fully closed state when the catalyst deterioration diagnosis value is small (when the catalyst is close to a new state), and becomes larger as the catalyst deterioration diagnosis value increases (progress of the catalyst deterioration) The catalyst deterioration diagnosis value is set to the fully open state when it is equal to or more than a predetermined value.
Table 1 is a table showing an example of the initial opening setting for the catalyst deterioration diagnosis value.
In addition, the intermediate value of the value described in Table 1 is suitably calculated | required by interpolation calculation.

After the ECU 100 sets the opening degree of the waste gate valve 46 to the initial opening degree, the series of processing ends (return).

<Step S05: West gate valve opening control according to target boost pressure>
The ECU 100 executes known boost pressure feedback control for feedback control of the opening degree of the waste gate valve 46 such that the actual boost pressure approaches the target boost pressure set from the driver request torque.
After that, the series of processing ends (returns).

Hereinafter, effects of the engine control device according to the embodiment will be described.
FIG. 5 is a graph showing an example of the correlation between the catalyst deterioration diagnosis value and the initial opening degree and the correlation between the initial opening degree and the catalyst temperature in the example.
FIG. 5 (a) shows the correlation between the catalyst deterioration diagnostic value and the initial opening, and FIG. 5 (b) shows the correlation between the initial opening and the catalyst temperature.
In the embodiment, as shown in FIG. 5 (a), the initial opening degree is set to be large according to the increase (progression of deterioration) of the catalyst deterioration diagnostic value, as shown in FIG. 5 (b), By increasing the catalyst temperature, it is possible to secure the purification processing capacity of the exhaust gas even in the case of a catalyst whose deterioration has progressed.

FIG. 6 is a graph showing an example of the transition of the exhaust gas temperature at the catalyst inlet when the waste gate valve is fully opened and fully closed.
In FIG. 6, the horizontal axis shows the time since engine start, and the vertical axis shows the exhaust gas temperature and the traveling speed (vehicle speed) of the vehicle.
The exhaust temperature at the catalyst inlet has a difference of, for example, about 30 to 50 ° C. throughout substantially the entire operation period in the state in which the waste gate valve 46 is maintained fully open and the state in which the waste gate valve 46 is maintained fully closed.
In the embodiment, the initial opening degree of the waste gate valve 46 is optimally set in accordance with the degree of deterioration of the catalyst, thereby maintaining the catalyst temperature at which the exhaust gas purification performance of the front catalyst 63 can be secured. It is possible to prevent the waste gate valve 46 from being opened, to suppress the delay in supercharging response at the time of acceleration or the like, and to ensure drivability.

As described above, according to this embodiment, the following effects can be obtained.
(1) When the condition of the front catalyst 63 is relatively good (the degree of deterioration progress is small), the initial opening degree of the waste gate valve 46 is set small to secure necessary catalyst temperature rising performance. Supply pressure response characteristics can be improved.
On the other hand, when the deterioration of the front catalyst 63 progresses, by setting the initial opening degree of the waste gate valve 46 large, the temperature of the catalyst can be raised to a higher temperature, and the exhaust gas purification performance can be secured.
(2) From the start of the engine 1 to the end of the catalyst warm-up, the front gate 63 is heated up promptly to be activated by substantially fully opening the waste gate valve 46, and exhaust gas immediately after start-up Purification performance can be improved.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, which are also within the technical scope of the present invention.
(1) The configurations of the engine control device, the engine, and the engine accessories are not limited to the configurations of the above-described embodiment, and can be changed as appropriate. For example, the cylinder layout of the engine, the number of cylinders, the number of turbochargers, and the like are not limited to the above-described embodiment, and can be changed as appropriate.
(2) The engine of the embodiment is, for example, a direct injection gasoline turbo engine, but the present invention is also applicable to an engine using port injection singly or in combination with direct injection.
Not only gasoline engines, but also catalysts that are disposed downstream of the turbocharger and whose exhaust gas purification performance is improved by temperature rise, and that can be used to diagnose catalyst deterioration, fuels other than diesel engines and gasoline It is possible to apply also to the spark ignition type engine to be used.
(3) In the embodiment, the deterioration of the catalyst is diagnosed by comparing the fluctuation of the output of the air-fuel ratio sensor on the upstream side of the catalyst with the fluctuation of the output of the rear O ₂ sensor on the downstream side. The method is not limited to this, and may be another method.
Further, the method for determining the end of catalyst warm-up after engine start is not particularly limited.

Reference Signs List 1 engine 10 crankshaft 11 crank angle sensor 20 cylinder block 30 cylinder head 31 combustion chamber 32 ignition plug 33 intake port 34 exhaust port 35 intake valve 36 exhaust valve 37 intake camshaft 38 exhaust camshaft 40 turbocharger 41 turbine 42 compressor 43 air Bypass flow path 44 Air bypass valve 45 West gate flow path 46 West gate valve 50 Intake system 51 Intake duct 52 Chamber 53 Air cleaner 54 Air flow meter 55 Intercooler 56 Throttle valve 57 Intake manifold 58 Intake pressure sensor 59 Injector 60 Exhaust system 61 Exhaust manifold 62 exhaust pipe 63 front catalyst 4 rear catalyst 65 silencer 66 air-fuel ratio sensor 67 rear _{O 2} sensor 70 the canister 71 purge line 72 purge control valve 73 purge line 74 purge control valve 100 an engine control unit (ECU)
101 accelerator pedal sensor

Claims (2)

A turbocharger driven by an exhaust gas of an engine and a turbocharger driven by the turbine and having a compressor for compressing combustion air;
A wastegate flow passage for bypassing part of the exhaust gas from the upstream side to the downstream side of the turbine;
A waste gate valve driven by an electric actuator to open and close the waste gate passage;
A catalytic converter provided downstream of the turbine for purifying the exhaust gas;
An engine control device for controlling an engine comprising: catalyst degradation diagnosis means for diagnosing the degradation state of the catalytic converter;
The opening degree of the waste gate valve is controlled by the supercharging pressure feedback control which controls the supercharging pressure to approach a predetermined target supercharging pressure in a high load state, and becomes a predetermined initial opening degree except in the high load state. Control means for controlling the waste gate valve
An initial opening degree setting means for setting the initial opening degree to a large value in accordance with the progress of deterioration of the catalytic converter diagnosed by the catalyst deterioration diagnosis means. A warm-up end determination unit that determines the end of warm-up of the catalytic converter;
The wastegate valve control means, during the period from the start of the engine until the warm-up completion is determined, the claim 1, characterized in that the total open state the waist gate valve regardless the initial opening The engine control device according to claim 1.

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