JP2003065058A - Control unit for engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsibility in a low rotational speed region of an engine when shifting an operating state from a twin turbo state to a single turbo state. SOLUTION: When it is judged that the present operating state of the engine shifts from the twin turbo region to the single turbo region (S160 to S164), on the basis of an engine rotational speed N, a single turbo region duration time judgement value T4 is set referring to a table with interpolation calculation (S165). A single turbo region duration time count value C2 is counted up and compared with the single turbo region duration time judgement value T4 (S167, S168). In case of C2<T4, the twin turbo state is maintained. In case of C2>=T4, the operating state is shifted to the single turbo state. Thus, the timing of shifting from the twin turbo state to the single turbo state is advanced in the low rotational speed region of the engine so as to prevent the operation when the torque is low in the twin turbo state, thereby improving the operatability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single turbo state in which a primary turbocharger and a secondary turbocharger are provided in an intake and exhaust system of an engine and only the primary turbocharger is supercharged. The present invention relates to a control device for an engine with a supercharger, which switches between a twin turbo state in which both turbochargers perform a supercharging operation according to an engine operating region.

[0002]

2. Description of the Related Art In recent years, a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine, and an intake control valve is provided in an intake and exhaust system connected to the secondary turbocharger. An engine with a supercharger (so-called sequential turbo engine) has been proposed in which exhaust control valves are respectively provided and both control valves are opened / closed to appropriately switch the operating number of the supercharger in accordance with the operating region.

In this supercharged engine, the operating range is set to a single turbo range in the low speed range and a twin turbo range in the high speed range as disclosed in Japanese Patent Application Laid-Open No. 7-77050 by the present applicant. When the operation area is divided into the single turbo area, the intake control valve is closed and the exhaust control valve is closed or opened slightly (to preliminarily rotate the secondary turbocharger) only the primary turbocharger. When the operating range is in the twin-turbo range, the control valves are both opened to set the twin-turbocharger to the supercharging mode so that the turbocharger operates from the low speed range. The output performance can be improved over the high speed range. When the operating range shifts from the twin turbo range to the single turbo range, the delay time until the twin turbo state is actually switched to the single turbo state is set to a shorter value as the engine load is higher, and The output performance and the acceleration performance are improved by minimizing the operation in the low torque region.

[0004]

However, in the above-mentioned prior art, the operating time shifts from the twin turbo region to the single turbo region, and the delay time when switching from the twin turbo state to the single turbo state depends on the engine load. Since it is set, the switching responsiveness in the engine low speed region tends to decrease, and especially when the engine speed greatly decreases due to the upshift of the transmission, it is necessary to switch to the single turbo state. However, there was a problem that the driving time deteriorated due to the continued operation in the low torque region in the twin-turbo state as the time increased.

The present invention has been made in view of the above circumstances, and is a control device for a supercharged engine capable of improving responsiveness in a low engine speed region when switching from a twin turbo state to a single turbo state. Is intended to provide.

[0006]

In order to achieve the above object, the invention according to claim 1 is provided with a primary turbo supercharger and a secondary turbo supercharger in an intake and exhaust system of an engine, and operates the supercharger. Depending on the comparison result of the switching judgment value for switching the state and the engine load, both the turbocharger and the single turbo region in which only the primary turbocharger is supercharged to bring it into the single turbo state are supercharged. In the control device of the engine with a supercharger that determines the twin-turbo range in which the fuel-supply operation is performed to make the twin-turbo state, the operating range shifts from the twin-turbo range to the single-turbo range according to the comparison result of the switching determination value and the engine load. At this time, delay time setting means for setting the delay time when switching from the twin turbo state to the single turbo state according to the engine speed, After the transitional region is changed from the twin turbo region to the single turbo region, when the duration of the single turbo region is equal to or longer than the delay time, a single turbo switching means for switching from the twin turbo state to the single turbo state is provided. And

The invention described in claim 2 is characterized in that, in the invention described in claim 1, the delay time setting means increases the delay time in accordance with an increase in an engine speed.

That is, according to the first aspect of the invention, when the operating range is changed from the twin turbo range to the single turbo range and the twin turbo state is switched to the single turbo state, the delay time is set according to the engine speed, When the duration of the single turbo region becomes equal to or longer than the delay time, the twin turbo state is switched to the single turbo state to improve the switching responsiveness in the low engine speed region and prevent deterioration of drivability.

At this time, it is desirable that the delay time when switching from the twin turbo state to the single turbo state be increased in accordance with the increase of the engine speed, as in the invention of claim 2, and the engine speed is temporarily changed. It is possible to prevent unnecessary switching due to a decrease in temperature.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 15 relate to an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an engine with a supercharger,
2 is a circuit configuration diagram of an electronic control system, FIGS. 3 to 6 are flowcharts of a turbo switching control routine, FIG. 7 is an explanatory diagram of a turbo switching determination value table, and FIG. 8 is an output characteristic at the time of single turbo and at the time of twin turbo. 9 is an explanatory diagram of the exhaust control valve small opening control region, FIG. 10 is an explanatory diagram of an exhaust control valve opening delay time setting table, and FIG. 11 is an explanatory diagram of an intake control valve opening delay time setting table. 12 is an explanatory diagram of an intake control valve opening differential pressure setting table, FIG. 13 is an explanatory diagram of a single turbo region continuation time determination value table, FIG. 14 is a time chart showing switching from a single turbo state to a twin turbo state, and FIG. It is a time chart which shows switching from a twin turbo state to a single turbo state.

First, the overall construction of a supercharged engine to which the present invention is applied will be described with reference to FIG. In the figure, reference numeral 1 is an engine with a supercharger (hereinafter simply referred to as "engine"), which is a horizontally opposed four-cylinder engine in the present embodiment. The engine 1 is provided with a combustion chamber 5, an intake port 6, an exhaust port 7, an ignition plug 8, a valve operating mechanism 9 and the like in the left and right banks 3 and 4 of a cylinder block 2, and the left bank 3 side has a # 2 nozzle # 2. The # 4 cylinder is provided, and the # 1 and # 3 cylinders are provided on the right bank 4 side.

Due to this engine shortening shape, the primary turbo supercharger 40 and the secondary turbo supercharger 50 are arranged immediately after the left and right banks 3 and 4, respectively. Then, as an exhaust system, the common exhaust pipe 10 from both the left and right banks 3 and 4 is connected to the turbines 40a and 50a of both turbochargers 40 and 50, and the turbines 40a and 50a are connected.
The exhaust pipe 11 from is joined to one exhaust pipe 12 and communicates with the catalytic converter 13 and the muffler 14. The primary turbocharger 40 is a small-capacity low-speed type that has a large supercharging capacity in the low-medium speed range, while the secondary turbocharger 50 has a large-capacity that has a large supercharging capacity in the middle-high speed range. It is a high-speed type. Therefore, the primary turbocharger 40 has a smaller capacity, so that the exhaust resistance becomes larger.

On the other hand, as an intake system, an air cleaner 15
Of the intake pipes 16 and 17 branched from the downstream of the compressor to the compressors 40b and 50 of the turbochargers 40 and 50, respectively.
The intake pipes 18 and 19 from the compressors 40b and 50b are connected to the intercooler 20.
The intercooler 20 communicates with a chamber 22 via a throttle body 27 having a throttle valve 21, and the chamber 22 communicates with an intake port 6 of each cylinder of the left and right banks 3 and 4 via an intake manifold 23.

As an idle control system, a bypass passage 2 that bypasses the throttle valve 21 and connects the intake pipe immediately downstream of the air cleaner 15 to the intake manifold 23.
4, an idle control valve (ISC valve) 25 and a check valve 26 opened by negative pressure are provided to control the intake air amount during idling or deceleration.

Further, the intake manifold 2 is used as a fuel system.
An injector 30 is provided immediately upstream of the intake port 6 for each cylinder 3
And a fuel tank 32 containing a fuel pump 31
A fuel passage 33 from is communicated with the injector 30 and the fuel pressure regulator 35 via a filter 34.

The fuel pressure regulator 35 acts to adjust the pressure of the intake pipe in the intake manifold 23, whereby the fuel pressure supplied to the injector 30 is constantly adjusted to be constant with respect to the intake pipe pressure. The fuel injection amount from the injector 30 driven by the injection signal from the electronic control unit 100 described later is controlled according to the pulse width of the injection signal. Further, as an ignition system, an ignition coil 8a is continuously provided for each ignition plug 8 of each cylinder, and each ignition coil 8a is connected to an igniter 36.

The operation system of the primary turbocharger 40 will be described below. Primary turbocharger 40
The compressor 40b is rotatably driven by the energy of the exhaust gas introduced into the turbine 40a, and operates so as to suck and pressurize air to constantly supercharge it.
A primary wastegate valve 41 including a primary wastegate valve operating actuator 42 composed of a diaphragm actuator is provided on the 0a side.

The actuator 42 for operating the primary wastegate valve is partitioned by a pressure chamber communicating from the control pressure passage 44 to the immediate downstream side of the compressor 40b via the orifice 48, and a diaphragm from the pressure chamber, and the primary wastegate valve is operated. A spring chamber for urging the valve 41 in the closing direction is housed, and a spring chamber in which a rod connecting the diaphragm and the primary wastegate valve 41 extends is provided, and the spring chamber is open to the atmosphere. When the supercharging pressure introduced into the pressure chamber rises above the set value, the primary wastegate valve 41 is opened with good response against the biasing force of the spring.

Further, the control pressure passage 44 is provided with a duty solenoid valve D.D. for primary wastegate control which leaks the boost pressure to the upstream side of the compressor 40b. SOL. 1 is connected to the primary wastegate control duty solenoid valve D.I. SOL. 1 operates in response to a duty signal from the electronic control unit 100 described later to generate a predetermined control pressure, and acts on the pressure chamber of the primary wastegate valve operating actuator 42.

That is, the primary wastegate control duty solenoid valve D.D. SOL. When the duty ratio of the duty signal output to 1 is small, the control pressure is increased to increase the opening degree of the primary wastegate valve 41 to reduce the supercharging pressure, and as the duty ratio increases, the leak amount increases. The control pressure is reduced by the increase, and the opening degree of the primary waste gate valve 41 is reduced to increase the supercharging pressure.

On the other hand, when the throttle valve is suddenly closed, in order to prevent a decrease in compressor rotation and an occurrence of intake noise due to the compressed air being trapped downstream of the compressor 40b, the throttle valve 21 is provided downstream of the compressor 40b.
The exit side of the nearby intercooler 20 and the compressor 4
A bypass passage 46 communicates with the upstream side of 0b, and an air bypass valve 45 is interposed in the bypass passage 46.

The air bypass valve 45 has a bypass passage 46.
A valve chamber having a valve body for opening and closing the valve, and a pressure chamber for accommodating a spring for urging the valve body in the closing direction and communicating with the intake manifold 23 through the passage 47 are configured by a diaphragm. When the throttle valve is suddenly closed, the negative pressure of the manifold is introduced into the pressure chamber through the passage 47 to open the valve, and the pressurized air trapped downstream of the compressor 40b quickly leaks through the bypass passage 46.

Next, the operation system of the secondary turbocharger 50 will be described. The secondary turbocharger 50 is
Similarly, the exhaust causes the turbine 50a and the compressor 50 to
b is rotated and supercharged, and the turbine 50a
On the side, a secondary wastegate valve 51 having a secondary wastegate valve actuating actuator 52 composed of a diaphragm type actuator is provided.

The secondary wastegate valve actuating actuator 52 includes a pressure chamber communicating with the control pressure passage 70a,
And, it is separated from this pressure chamber by a diaphragm,
A spring for urging the secondary wastegate valve 51 in the closing direction is housed, and a spring chamber for extending a rod connecting the diaphragm and the secondary wastegate valve 51 is provided. The secondary waste gate valve 51 is opened and closed according to the control pressure which is opened and introduced into the pressure chamber from the control pressure passage 70a.

The exhaust pipe 10 upstream of the turbine 50a is also provided.
Is provided with a downstream opening type exhaust control valve 53 provided with an exhaust control valve operating actuator 54 composed of a diaphragm type actuator, and an intake control valve operating actuator 56 composed of a diaphragm type actuator is provided downstream of the compressor 50b. A butterfly type intake control valve 55 is provided. A supercharging pressure relief valve 57 is provided in a relief passage 58 that communicates between the upper side and the downstream side of the compressor 50b.

The exhaust control valve actuating actuator 54 is
Two pressure chambers, that is, a positive pressure chamber 54a that communicates with the control pressure passage 73a, and a spring that partitions the positive pressure chamber 54a from the positive pressure chamber 54a by a diaphragm and biases the exhaust control valve 53 in the closing direction are housed. The exhaust pressure control valve 53 is configured to include a negative pressure chamber 54b from which a rod extending in series extends, and the negative pressure chamber 54b communicates with the control pressure passage 74a. The force in the valve opening direction due to the pressure difference between the positive pressure introduced into the positive pressure chamber 54a and the negative pressure introduced into the negative pressure chamber 54b, and the force in the valve closing direction due to the mechanical biasing force of the spring. Accordingly, the opening degree of the exhaust control valve 53 is changed.

The actuator 56 for operating the intake control valve is
A pressure chamber that communicates with the control pressure passage 72a and stores a spring that biases the intake control valve 55 in the opening direction, and a rod that is partitioned from the pressure chamber by a diaphragm and that connects the diaphragm and the intake control valve 55 to each other, are provided. It is configured to have an extended atmospheric chamber that is open to the atmosphere, and opens and closes the intake control valve 55 according to the control pressure introduced into the pressure chamber.

The boost pressure relief valve 57 is provided in the relief passage 5
A valve chamber having a valve body for opening and closing 8 and a pressure chamber for accommodating a spring for urging the valve body in the closing direction and communicating with the control pressure passage 71a are partitioned by a diaphragm. When the valve is closed, the valve body is opened by the negative pressure introduced into the pressure chamber, and the secondary turbocharger 50
The supercharging pressure trapped between the downstream side of the compressor 50b and the intake control valve 55 is leaked.

The pressure operating system for each of the above valves is as follows:
A secondary wastegate valve switching solenoid valve SOL. That switches connection between a passage 65 communicating upstream of the intake control valve 55 and a control pressure passage 70a communicating with the pressure chamber of the secondary wastegate control valve actuating actuator 52.
W, a control pressure passage 71 communicating with the positive pressure passage 64a communicating downstream of the intake control valve 55 and the pressure chamber of the boost pressure relief valve 57.
a and a negative pressure passage 63 communicating with the surge tank 60 of the negative pressure source
Switching solenoid valve for boost pressure relief valve SOL. 1. The control pressure passage 72a communicating with the pressure chamber of the intake control valve operating actuator 56 and the surge tank 60
Of the intake control valve switching solenoid valve SOL. 2. Switching the connection between the positive pressure passage 64b communicating downstream of the intake control valve 55, the control pressure passage 73a communicating with the positive pressure chamber 54a of the exhaust control valve actuating actuator 54, and the negative pressure passage 63 communicating with the surge tank 60. The first exhaust control valve switching solenoid valve SOL.
3. Negative pressure chamber 54 of the exhaust control valve actuating actuator 54
b of the second exhaust control valve for switching the connection between the control pressure passage 74a communicating with the surge tank 60 and the negative pressure passage 63 communicating with the surge tank 60. 4 is provided.

Further, in the leak passage 66 connecting the downstream side of the orifice 67 interposed in the control pressure passage 73a and the intake pipe 16, the exhaust control valve small opening control duty solenoid valve D.D. SOL. 2 is installed. Each switching solenoid valve SOL. A surge tank 60 is provided as a negative pressure source for the intake manifolds 1, 2 and 4, and the surge tank 60 is provided with the intake manifold 2 via a passage 61 having a check valve 62.
When the throttle valve 21 is fully closed, it stores negative pressure and buffers pulsating pressure.

Each switching solenoid valve SOL. W, SOL.
1 to 4 are ON and O from the electronic control unit 100 described later.
The passage 6 communicating with the upstream side of the intake control valve 55 by the FF signal
5, the positive pressure from the surge tank 60, the negative pressure from the negative pressure passage 63 from the surge tank 60, the positive pressure from the positive pressure passages 64a and 64b communicating downstream of the intake control valve 55, or the atmospheric pressure.
The secondary waste gate valve 51, the supercharging pressure relief valve 57, and the control valves 55 and 53 are operated by being guided to each actuator by the control pressure passages 70a to 74a. In addition, the exhaust control valve small opening control duty solenoid valve D.D.
SOL. 2 controls the positive pressure acting on the pressure chamber of the exhaust control valve actuating actuator 54 by the duty signal from the electronic control unit 100, and controls the exhaust control valve 53 to be small open.

Specifically, the secondary wastegate valve switching solenoid valve SOL. W is turned off only when it is determined by the electronic control unit 100 that high-octane gasoline is used based on the ignition advance amount and the like, and is turned on when it is determined that regular gasoline is used. Then, the secondary wastegate valve switching solenoid valve SOL. W is OFF
Then, the passage 65 communicating with the upstream side of the intake control valve 55 is closed to open the atmospheric port, and the atmospheric pressure is introduced into the pressure chamber of the secondary wastegate valve actuating actuator 52 through the control pressure passage 70a. The secondary waste gate valve 51 is closed by the biasing force of the spring.

Further, the switching solenoid valve SOL. When W is turned ON, the atmospheric port is closed and the passage 65 side is opened, and the supercharging pressure downstream of the secondary turbocharger 50 when both turbochargers 40 and 50 are operating is equal to that of the secondary wastegate valve actuating actuator 52. It is guided to the pressure chamber, and the secondary waste gate valve 51 is opened according to this supercharging pressure, and the supercharging pressure is relatively reduced when using regular gasoline as compared to when using high-octane gasoline.

Switching solenoid valve SO for boost pressure relief valve
L. When turned off, 1 closes the positive pressure passage 64a side and opens the negative pressure passage 63 side, and guides the negative pressure to the pressure chamber in which the spring of the supercharging pressure relief valve 57 is installed via the control pressure passage 71a. The supercharging pressure relief valve 57 is opened against the biasing force of the spring. When turned on, the negative pressure passage 6 is turned on the contrary.
3 side is closed and the positive pressure passage 64a side is opened, and positive pressure is introduced into the pressure chamber of the supercharging pressure relief valve 57, whereby the supercharging pressure relief valve 5
Close 7.

Intake control valve switching solenoid valve SOL. Two
When turned off, the atmospheric port is closed to open the negative pressure passage 63 side, and the negative pressure is guided to the pressure chamber in which the spring of the intake control valve actuating actuator 56 is installed via the control pressure passage 72a. The intake control valve 55 is closed against the urging force, and when it is turned on, the negative pressure passage 63 side is closed to open the atmospheric port, and the atmospheric pressure is introduced into the pressure chamber of the intake control valve actuating actuator 56 so that the pressure inside the pressure chamber is reduced. The intake control valve 55 is opened by the biasing force of the spring.

First exhaust control valve switching solenoid valve SO
L. 3, second switching solenoid valve for exhaust control valve SOL.
When both are off, the first exhaust control valve switching solenoid valve SOL. 3 closes the positive pressure passage 64b side to open the atmospheric port, and the second exhaust control valve switching solenoid valve SO
L. 4 closes the negative pressure passage 63 side and opens the atmospheric port, so that both chambers 54 of the exhaust control valve actuating actuator 54
The a and 54b are opened to the atmosphere, and the exhaust control valve 53 is fully closed by the urging force of the spring installed in the negative pressure chamber 54b.

Both switching solenoid valves SOL. 3,4
When both are ON, the atmospheric ports are closed and the first exhaust control valve switching solenoid valve SOL. 3 is a positive pressure passage 6
4b side is opened and the second exhaust control valve switching solenoid valve S
OL. 4 opens the negative pressure passage 63 side to guide positive pressure to the positive pressure chamber 54a and negative pressure to the negative pressure chamber 54b of the exhaust control valve actuating actuator 54, thereby resisting the biasing force of the spring. Fully open 53.

In addition, the first exhaust control valve switching solenoid valve SOL. 3 is ON, positive pressure is supplied to the positive pressure chamber 54a of the exhaust control valve actuating actuator 54, and the negative pressure chamber 54a
In the state in which the valve b is opened to the atmosphere, the exhaust control valve small opening control duty solenoid valve D. SOL. The positive pressure is leaked by 2 and the exhaust control valve 53 is opened slightly.

Here, the exhaust control valve small opening control duty solenoid valve D. SOL. 2 has a large duty ratio in the duty signal from the electronic control device 100,
By increasing the leak amount, the positive pressure acting on the positive pressure chamber 54a is reduced to reduce the opening degree of the exhaust control valve 53, and as the duty ratio becomes smaller, the leak amount is reduced to maintain the positive pressure higher, and the exhaust control valve 53 Operates in the direction of increasing the opening degree of. When the engine operating region is in the predetermined exhaust control valve small opening control region under the single turbo state, the exhaust control valve small opening control duty solenoid valve D. SOL. The supercharging pressure is feedback-controlled by the opening degree of the exhaust control valve 53 by 2, and the exhaust control valve 53 is opened slightly in accordance with the supercharging pressure control.

Next, various sensors provided in the engine 1 will be described. A differential pressure sensor 80 is connected to a passage communicating with the upstream side of the intake control valve 55 and a passage communicating with the downstream side of the intake control valve 55.
Downstream differential pressure is detected. Also, the intake manifold 23
Is connected to an absolute pressure sensor 81 via an intake pipe pressure / atmospheric pressure switching solenoid valve 76. By switching the intake pipe pressure / atmospheric pressure switching solenoid valve 76, the intake pipe pressure (pressure inside the intake manifold 23) and the absolute value are increased. Atmospheric pressure and are selectively detected.

Further, a knock sensor 82 is attached to the cylinder block 2, a cooling water temperature sensor 83 is exposed to a cooling water passage connecting the left and right banks 3 and 4, and an O 2 sensor 84 is exposed to the exhaust pipe 10. . Further, the throttle valve 21 is provided with a throttle sensor 85 having a built-in throttle opening sensor 85a for detecting the throttle opening and an idle switch 85b which is turned on when the throttle valve is fully closed. A sensor 86 is provided.

A crank rotor 90 is mounted on a crank shaft 1a supported by the cylinder block 2,
A crank angle sensor 87 including an electromagnetic pickup and the like is provided on the outer periphery of the crank rotor 90 so as to be opposed thereto. Further, a cylinder discriminating sensor 88 including an electromagnetic pickup and the like is provided opposite to a cam rotor 91 that is connected to a cam shaft of the valve mechanism 9.

Crank angle sensor 87, cylinder discrimination sensor 8
Reference numeral 8 detects protrusions formed at predetermined intervals on the crank rotor 90 and the cam rotor 91, respectively, during engine operation, and outputs a crank pulse and a cylinder discrimination pulse. Then, in the electronic control unit 100, the engine speed is calculated from the crank pulse interval time (protrusion detection interval), and the ignition timing and the fuel injection start timing are calculated,
Further, the cylinder discrimination is performed based on the input patterns of the crank pulse and the cylinder discrimination pulse.

Next, the structure of the electronic control system will be described with reference to FIG. An electronic control unit (ECU) 100 that controls the engine 1 includes a CPU 101, a ROM 102, and an R.
AM 103, backup RAM 104, counter / timer group 105, and I / O interface 106 are mainly configured by a microcomputer connected via a bus line, and a constant voltage circuit 107 for supplying a predetermined stabilizing power supply to each unit, a drive circuit 108, A / D converter 109
And other peripheral circuits.

The counter / timer group 105 is for generating various counters such as a free-run counter, a counter for inputting a cylinder discrimination signal (cylinder discrimination pulse), a fuel injection timer, an ignition timer, and a periodic interrupt. Various timers such as a timer for periodic interrupt, a timer for measuring an input interval of a crank angle sensor signal (crank pulse), and a watchdog timer for monitoring a system abnormality are collectively referred to for convenience. -Including a timer.

The constant voltage circuit 107 is connected to the battery 111 via the first relay contact of the power supply relay 110 having two relay contacts, and also directly connected to the battery 1.
11 and an ignition switch 112.
Is detected at the input port of the I / O interface 106 and the contact of the power relay 110 is closed, EC
While supplying power to each unit in U100, backup power is always supplied to the backup RAM 104 regardless of whether the ignition switch 112 is ON or OFF. Further, the battery 111 includes a fuel pump relay 11
The fuel pump 31 is connected via the relay contact 3 of FIG. A power supply line for supplying power from the battery 111 to each actuator is connected to the second relay contact of the power supply relay 110.

Further, an ignition switch 112, an idle switch 85b, a knock sensor 82, a crank angle sensor 87, a cylinder discrimination sensor 88, a vehicle speed sensor 114, etc. are connected to the input port of the I / O interface 106. Through the D converter 109, the intake air amount sensor 86, the throttle opening sensor 85a, the cooling water temperature sensor 83, the O2 sensor 84, the absolute pressure sensor 81, the differential pressure sensor 80, etc. are connected and the battery voltage VB is input. Are monitored.

The output port of the I / O interface 106 has a switching solenoid valve S for the boost pressure relief valve.
OL. 1, intake control valve switching solenoid valve SOL. 2,
The first exhaust control valve switching solenoid valve SOL. 3, second
Exhaust control valve switching solenoid valve SOL. 4. Duty solenoid valve D. for primary wastegate control S
OL. 1. Exhaust control valve small open control duty solenoid valve D.I. SOL. 2. Secondary wastegate valve switching solenoid valve SOL. W, the intake pipe pressure / atmospheric pressure switching solenoid valve 76, the ISC valve 25, and the injector 30 are connected via the drive circuit 108, and the igniter 36 is also connected.
Are connected.

In the above electronic control system, when the ignition switch 112 is turned on, the power relay 110 is turned on.
Then, a constant voltage is supplied to each unit via the constant voltage circuit 107, and the ECU 100 executes various controls. That is, E
In the CU 100, the CPU 101 inputs the detection signals from various sensors through the I / O interface 106 based on the arithmetic program stored in the ROM 102, and the RAM 103 and the backup RAM 10
Various control amounts are calculated based on the various data stored in No. 4 and the fixed data stored in the ROM 102.

Then, each switching solenoid valve 76, SOL. 1-4, SOL. ON to W,
The OFF signal is sent to each duty solenoid valve D.D. SOL.
1, D. SOL. 2 outputs a duty signal to execute the operation switching control and the supercharging pressure control of the turbocharger, and outputs the drive pulse width signal that determines the calculated fuel injection amount to the injector 30 of the corresponding cylinder at a predetermined timing. Execute fuel injection control. Further, at a predetermined timing, an ignition signal is output to the igniter 36 to execute ignition timing control, and IS
A control signal is output to the C valve 25 to execute idle speed control and the like.

In this case, in the turbocharger operation switching control in the ECU 100, the operation region is a single turbo region in which only the primary turbocharger 40 is supercharged, and the primary turbocharger 4 is operated.
0 and the secondary turbocharger 50 are divided into a twin turbo region in which the turbocharger is operated in a supercharger state, and a switching for switching the supercharger operating state to which region the current operating region is located. Judgment is made according to the result of comparison between the judgment value (single-to-twin switching judgment value Tp2, twin-to-single switching judgment value Tp1 described later) and the engine load.

As a result, when the operating region is in the single turbo region, the boost pressure relief valve switching solenoid valve SOL. 1 is turned off to open the boost pressure relief valve 57, and the intake control valve switching solenoid valve SOL. 2 is turned off, the intake control valve 55 is closed, and the first and second exhaust control valve switching solenoid valves SOL. 3, SOL. 4 are turned off and the exhaust control valve is closed, or the first exhaust control valve switching solenoid valve SOL. Only the No. 3 is turned on, the exhaust control valve 53 is slightly opened, and only the primary turbocharger 40 is brought into the single turbo state in which the supercharge operation is performed.

Further, when the operating region is in the twin turbo region, the boost pressure relief valve switching solenoid valve SO
L. 1, intake control valve switching solenoid valve SOL. 2, first and second exhaust control valve switching solenoid valves SOL. Three
SOL. 4 is turned on, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 53 are both opened, and both turbochargers 40 and 50 are placed in a twin turbo state in which supercharging operation is performed.

When the operating region shifts from the twin turbo region to the single turbo region during the operation in the twin turbo condition, the boost pressure relief valve switching solenoid valve SOL. 1, intake control valve switching solenoid valve SOL. 2, first and second exhaust control valve switching solenoid valves SOL. 3, SOL. 4 is turned off to switch from the twin-turbo state to the single-turbo state, and control hunting for switching the turbocharger operating state (turbo switching) when the single-turbo region determination and the twin-turbo region determination are repeated by throttle operation, etc. To prevent.

The delay time at the time of switching from twin to single turbo is set according to the engine speed, is short in the low speed region, increases in the medium speed region as the engine speed increases, and increases in the high speed region. It is set long in the area. That is, after shifting from the twin-turbo region to the single-turbo region, the lower the engine speed, the earlier the timing of switching from the twin-turbo state to the single-turbo state, especially when the engine speed greatly decreases due to the upshift of the transmission. Quickly switch to single turbo state,
It avoids driving in the low-torque area in the twin-turbo state and prevents deterioration of drivability.

That is, the ECU 100 has the functions of the delay time setting means and the single turbo switching means according to the present invention, and specifically realizes the functions of the respective means in the routines shown in FIGS.

Hereinafter, the processing relating to the operation control of the primary turbocharger 40 and the secondary turbocharger 50 by the ECU 100 will be described with reference to the flowcharts of FIGS.

3 to 6 show the primary turbocharger 4
A control mode (single turbo mode) to a single turbo state in which only 0 is supercharged and both turbochargers 40,
A turbo switching control routine for switching a control mode to a twin turbo state (twin turbo mode) for supercharging 50 is shown. The ignition switch 112 is turned on to power on the system, and the system is initialized (each flag, each After clearing the count value, etc.),
It is executed every set time (for example, 10 msec).

In this turbo switching control routine, first,
In step S101, the twin turbo mode determination flag F1 (initial value is 0; single turbo mode) for determining whether the current control state is the single turbo mode or the twin turbo mode is referred to. When the twin turbo mode discrimination flag F1 is cleared (F1 = 0),
The process proceeds from step S101 to step S102 and subsequent steps in the single turbo mode, and when set (F1 = 1), steps S101 to S160.
Then, the process proceeds to the twin turbo mode process.

In the following description, the single turbo mode will be described first, followed by the single → twin switching control, the twin turbo mode, and finally the twin → single switching control.

Immediately after the ignition switch 112 is turned on and when the current control state is the single turbo mode, since F1 = 0, the process proceeds from step S101 to step S102, and the turbo switching determination value table is based on the engine speed N. With reference to the interpolation calculation, the single-to-twin switching determination value Tp2 is set.

As shown in FIG. 7, in the turbo switching determination value table, the basic fuel injection pulse width Tp (Tp = K × Q / N; Q is the intake air amount, K is the intake air amount, K is the engine speed N and engine load). From the relationship with (constant), a single → twin switching determination line L2 that is optimal for switching from single turbo mode to twin turbo mode, and conversely, a twin → single switching determination line L1 that is optimal for switching from twin turbo mode to single turbo mode The single turbo region and the twin turbo region are set in advance by being obtained from simulations or experiments. Then, each line L2
Corresponding to L1, single → twin switching judgment value T
p2 and the twin-to-single switching determination value Tp1 are RO in advance as a table with the engine speed N as a parameter.
It is stored in a series of addresses of M102.

The single-to-twin switching determination line L2
Must be set at a point where the torque curve for the single turbo and the torque curve for the twin turbo of the output characteristics shown in FIG. 8 coincide with each other in order to prevent torque fluctuation during switching. As described above, the load is set to the low load side in accordance with the increase of the engine speed N from the high load in the low and middle speed ranges. Further, as shown in the figure, in order to prevent control hunting at the time of switching the operation of the turbocharger, the twin → single switching determination line L1 is relatively on the low rotation speed side with respect to the single → twin switching determination line L2. It is set with a wide hysteresis range.

Next, the routine proceeds to step S103, where the single-to-twin switching determination value Tp2 is compared with the current basic fuel injection pulse width (engine load) Tp. If Tp <Tp2, the routine proceeds to step S104 and thereafter to the single turbo mode. If Tp ≧ Tp2, the process branches to step S130 and subsequent steps to shift to single → twin switching control for switching from the single turbo state to the twin turbo state.

In the processing in the single turbo mode after step S104, first, the value of the supercharging pressure control mode determination flag F2 is referred to in step S104. The supercharging pressure control mode determination flag F2 is set when the current operation region is within the exhaust control valve small opening control region in which the supercharging pressure control is performed by the small opening of the exhaust control valve 53 and the secondary turbocharger 50 is preliminarily rotated. (F2 = 1) and cleared when outside the area (F2
= 0).

Therefore, immediately after the ignition switch 112 is turned on, the initial setting is performed, and when the operating region is outside the exhaust control valve small open control region during the execution of the previous routine, F2 = 0, so the process proceeds to step S105.
It is determined whether the current operating region has moved into the exhaust control valve small opening control region by the condition determination in steps S105 to S107.

This transition to the exhaust control valve small opening control region is determined from the single-to-twin switching determination line L2 based on the relationship between the engine speed N and the intake pipe pressure (supercharging pressure) P as shown in FIG. Also on the low rotation and low load side, that is, under the single turbo condition, the set value N2 (for example, 2650 rp)
m) and P2 (for example, 1120 mmHg), and when the throttle opening TH is equal to or larger than the set value TH2 (for example, 30 deg), it is determined that the shift has occurred within the region.

Specifically, the engine speed N and the set value N2 are compared in step S105, the intake pipe pressure P and the set value P2 are compared in step S106, and step S10
At 7, the throttle opening TH is compared with the set value TH2.
And N <N2, or P <P2, or TH <TH
In the case of 2, the process proceeds to step S108, it is determined that the current operation region is outside the exhaust control valve small opening control region, the supercharging pressure control mode determination flag F2 is cleared (F2 ← 0), and N ≧
If N2 and P ≧ P2 and TH ≧ TH2, the process proceeds to step S112, it is determined that the current operation region has shifted to the exhaust control valve small opening control region, and the supercharging pressure control mode determination flag F2.
Set (F2 ← 1).

Then, the process proceeds from step S108 or step S112 to step S113, and the boost pressure relief valve switching solenoid valve SOL. 1 is turned off, and in step S114, the intake control valve switching solenoid valve SOL. Two
Turn off. Next, proceeding to step S115, referring to the value of the supercharging pressure control mode determination flag F2, if F2 = 0, proceeding to step S116, the first exhaust control valve switching solenoid valve SOL. Turn OFF 3 and step S11
8 for the second exhaust control valve switching solenoid valve SOL. Turn off 4.

Then, from step S118 to step S
119, in steps S119 to S121, the twin turbo mode determination flag F1, the differential pressure search flag F3 used in the single-to-twin switching control described below, and the twin after the transition to the twin-turbo region by the single-to-twin switching control described below. The turbo region duration time is measured, the twin turbo region duration time count value C1 for determining the timing of switching the control valve is cleared, and the routine is exited.

Therefore, under the single turbo condition and in the low rotation and low load operation region outside the exhaust control valve small opening control region, each switching solenoid valve SOL. 1 to 4 are all OF
It becomes F. Therefore, the boost pressure relief valve 57 is the switching solenoid valve for the boost pressure relief valve SOL. When 1 is turned off, the negative pressure from the surge tank 60 is introduced into the pressure chamber, and the valve is opened against the biasing force of the spring. The intake control valve 55 includes an intake control valve switching solenoid valve SOL. When 2 is turned off, negative pressure is introduced into the pressure chamber of the intake control valve actuating actuator 56, so that the valve is closed against the biasing force of the spring. Further, the exhaust control valve 53 is
The second exhaust control valve switching solenoid valve SOL. When the exhaust valves 3 and 4 are turned off, atmospheric pressure is introduced into both chambers 54a and 54b of the exhaust control valve actuating actuator 54, thereby closing the valve by the biasing force of the spring.

Then, by closing the exhaust control valve 53, the introduction of exhaust gas to the secondary turbocharger 50 is cut off, the secondary turbocharger 50 is deactivated, and the single turbocharger 40 only operates. It becomes a state. Further, by closing the intake control valve 55, leakage of the boost pressure from the primary turbocharger 40 to the secondary turbocharger 50 side via the intake control valve 55 is prevented, and the boost pressure is reduced. Is prevented.

In the single turbo condition and outside the exhaust control valve small opening control region, or in the twin turbo condition, the supercharging pressure feedback control is performed using only the primary waste gate valve 41. That is, the target boost pressure set based on the engine operating state and the intake pipe pressure detected by the absolute pressure sensor 81, that is, the actual boost pressure P.
And the primary wastegate control duty solenoid valve D.D. SOL. 1 is calculated, and the duty signal of the ON duty is calculated as the primary wastegate control duty solenoid valve D.D. SOL. 1 to control the primary waste gate valve 41 to perform supercharging pressure control.

On the other hand, when it is determined that the current operation region is within the exhaust control valve small opening control region and the supercharging pressure control mode determination flag F2 is set in step S112, step S1
13 to S115, the process proceeds to step S117, where the first exhaust control valve switching solenoid valve SOL. After turning on 3, the routine exits through steps S118 to S121 described above. Therefore, the first exhaust control valve switching solenoid valve SOL. Only No. 3 is turned on, positive pressure is introduced into the positive pressure chamber 54a of the exhaust control valve actuating actuator 54, and the exhaust control valve 53 is opened.

In this exhaust control valve small opening control mode, the exhaust control valve 53 is used to perform supercharging pressure feedback control, and the exhaust control valve 53 is slightly opened accordingly. That is, the target boost pressure is compared with the actual boost pressure detected by the absolute pressure sensor 81, and the exhaust control valve small opening control duty solenoid valve D.D. SOL. 2 is calculated, and the duty signal of this ON duty is used for the exhaust control valve small open control duty solenoid valve D.V.
SOL. 2 to execute the boost pressure feedback control.

Therefore, the exhaust control valve small opening control duty solenoid valve D.D. SOL. 2, the positive pressure acting on the positive pressure chamber 54a of the exhaust control valve actuating actuator 54 is regulated, and as shown in FIG. 14, the exhaust control valve 53 is slightly opened and supercharging is performed using only the exhaust control valve 53. Pressure feedback control is performed. Then, the exhaust control valve 53 is opened slightly so that a part of the exhaust gas is discharged from the turbine 50 of the secondary turbocharger 50.
The secondary turbo supercharger 50 is preliminarily rotated in preparation for the transition to the twin turbo state.

In this state, since the intake control valve 55 is closed, the supercharging pressure between the downstream side of the compressor 50b of the secondary turbocharger 50 and the intake control valve 55 (by the secondary turbocharger 50) is increased. Although the compressor pressure) is contained, the supercharging pressure relief valve 57 is opened at this time to leak the supercharging pressure and smooth the preliminary rotation.

If the engine operating range is within the exhaust control valve small opening control range under the single turbo condition and the supercharging pressure control mode determination flag F2 is set (F2 = 1), the process proceeds from step S104. The process proceeds to step S109, and it is determined whether the current operating region has moved outside the exhaust control valve small open control region based on the condition determination in steps S109 to S111.

In order to prevent the control hunting at the time of switching the supercharging pressure control mode, the determination of the shift to the outside of this region is provided with hysteresis for each determination value for the engine speed N, the intake pipe pressure P, and the throttle opening TH. As shown in FIG. 9, set values N1 (for example, 2600 rpm), P1 (for example, 1070 mmHg), and TH1 (for example, 25 de, which are lower than the above-mentioned set values N2, P2, and TH2.
Determined according to g).

That is, the engine speed N is compared with the set value N1 in step S109, the intake pipe pressure (supercharging pressure) P is compared with the set value P1 in step S110, and the throttle opening TH is compared with step S111. Compared with the set value TH1, N <N1, or P <P1, or TH <TH1
In this case, it is determined that the current operation region has moved to the outside of the exhaust control valve small opening control region, the process returns to step S108, and the supercharging pressure control mode determination flag F2 is cleared. This allows
The exhaust control valve small open control is released. Further, when N ≧ N1 and P ≧ P1 and TH ≧ TH1, it is determined that the current operation region is still within the region, the process proceeds to step S112 described above, and the supercharging pressure control mode determination flag F2 is set to F2 = The state of 1 is maintained and the exhaust control valve small opening control is continued.

As described above, under the single turbo state, most of the exhaust gas from the engine 1 is introduced into the primary turbocharger 40 and the turbine 40a rotationally drives the compressor 40b. So compressor 40b
Air is sucked and compressed by the intercooler 20, the flow rate of the compressed air is adjusted by the opening degree of the throttle valve 21, and the compressed air is supplied to each cylinder through the chamber 22 and the intake manifold 23 with high charging efficiency and supercharged. To work. Then, in the single turbo state in which only the primary turbocharger 40 operates, as shown in the output characteristic of FIG.
A torque curve for a single turbo with high shaft torque in the middle speed range can be obtained.

Next, the single-to-twin switching control will be described. When it is determined in step S103 described above that Tp ≧ Tp2, that is, the current operation region has shifted from the single turbo region to the twin turbo region (see FIG. 7), the process branches from step S103 to step S130, and the primary turbocharger The single-to-twin switching control for switching from the single turbo state in which only 40 operates to the twin turbo state in which both turbochargers 40 and 50 operate is executed.

In this single-to-twin switching control, first, in step S130, the boost pressure relief valve switching solenoid valve SOL. 1 is determined, and in step S132, the first exhaust control valve switching solenoid valve SOL. The energization state for 3 is determined. Then, both switching solenoid valves SOL. If both 1 and 3 are ON, the process directly proceeds to step S134 and each switching solenoid valve S
OL. When 1 and 3 are OFF, steps S131 and S1
After turning on at 33, the process proceeds to step S134.

Therefore, the switching solenoid valve SOL. When 1 is turned on, the positive pressure from the positive pressure passage 64a is introduced into the pressure chamber of the supercharging pressure relief valve 57, and the supercharging pressure relief valve 57 is immediately closed by the positive pressure and the biasing force of the spring. In addition, the second exhaust control valve switching solenoid valve SOL. 4 is OFF and the first exhaust control valve switching solenoid valve SOL. By turning on only No. 3, positive pressure is introduced into the positive pressure chamber 54a in a state where the negative pressure chamber 54b of the exhaust control valve actuating actuator 54 is open to the atmosphere, and the exhaust control valve is resisted against the biasing force of the spring. 53 opens.

In this case, when the exhaust control valve small open control mode under the single turbo mode is shifted to the single → twin switching control, the supercharging pressure feedback control by the exhaust control valve 53 is stopped and the exhaust control valve small open is performed. Control duty solenoid valve D. SOL. 2 is fully closed, positive pressure passage 6
The positive pressure via the exhaust solenoid control valve small open control duty solenoid valve D.D. DOL. 2, the positive pressure chamber 5 of the actuator 54 for directly operating the exhaust control valve without leaking.
4a, the opening degree of the exhaust control valve 53 is increased.

The relief passage 58 is closed by closing the supercharging pressure relief valve 57, and the rotation speed of the secondary turbocharger 50 is increased by opening the exhaust control valve 53 and increasing its opening. At the same time, the supercharging pressure between the downstream side of the compressor 50b of the secondary turbocharger 50 and the intake control valve 55 is gradually increased to prepare for the transition to the twin turbo state.

Next, in step S134, the value of the differential pressure search flag F3 is referred to. If F3 = 0, step S1
35, and if F3 = 1, jump to step S139. After shifting to the single-to-twin switching control, F3 = 0 at the first routine execution, so step S13.
5, first, referring to the exhaust control valve opening delay time setting table with interpolation calculation based on the vehicle speed VSP, fully open control of the exhaust control valve 53 after the transition from single to twin switching control (for the second exhaust control valve) Switch solenoid valve SOL.4 to O
Set the exhaust control valve opening delay time T1 that determines the timing (from FF to ON).

Then, in step S136, the vehicle speed VSP
Referring to the intake control valve open delay time set value table with interpolation calculation based on the above, after the exhaust control valve 53 is fully opened, the intake control valve 55 is opened (from the intake control valve switching solenoid valve SOL.2 to OFF). The intake control valve opening delay time T2 for setting the condition of the start timing is set, and in step S137, the differential pressure between the upstream pressure Pu and the downstream pressure Pd of the intake control valve 55 (the differential pressure sensor 80). Of the intake control valve 5 based on DPS (= Pu-Pd)
The intake control valve opening differential pressure DPSST for determining the valve opening control start timing of No. 5 is set.

FIG. 10 shows the characteristics of the exhaust control valve opening delay time setting table, and FIG. 11 shows the characteristics of the intake control valve opening delay time setting table. As shown in FIGS. 10 and 11, as the vehicle speed VSP is higher, the exhaust control valve opening delay time T1 and the intake control valve opening delay time T2 are shortened,
Advance the timing of fully opening the exhaust control valve 53 and the timing of opening the intake control valve 55, that is, the timing of switching from the single turbo state to the twin turbo state,
Improves drivability by equalizing acceleration response regardless of vehicle speed.

FIG. 12 shows the characteristics of the intake control valve opening differential pressure setting table. As shown in the figure, the differential pressure DPS immediately after the engine operating state shifts from the single turbo region to the twin turbo region (see FIG. 7) with the single → twin switching determination line L2 (single → twin switching determination value Tp2) as a boundary. The negative pressure side, that is, the higher the downstream pressure Pd with respect to the upstream pressure Pu of the intake control valve 55 and the higher the supercharging state, the intake control valve opening differential pressure as a determination condition for opening the intake control valve 55. With DPSST set to the negative side, the timing at which the intake control valve 55 is opened, that is, the supercharging start timing by the secondary turbocharger 50 is advanced, and the twin turbo state is set early to improve the acceleration performance.

After setting the above delay times T1 and T2 and the intake control valve opening differential pressure DPSST, step S13
8, the differential pressure search flag F3 is set (F3 ←
1), in step S139, the second exhaust control valve switching solenoid valve SOL. By checking the energization state for No. 4, it is determined whether or not the full open control for the exhaust control valve 53 has already started.

As a result, in step S139, S
OL. 4 = ON, and if the exhaust control valve fully open control has already been started, the process jumps to step S143 and the second exhaust control valve switching solenoid valve SOL. Turn on 4
SOL. If 4 = OFF, it means that the exhaust control valve fully open control has not yet been executed, and therefore the process proceeds to step S140.
The twin turbo region duration time count value C1 is compared with the exhaust control valve opening delay time T1.

If C1 ≧ T1, the routine proceeds to step S141, where the second exhaust control valve switching solenoid valve SOL. 4 is turned on and the exhaust control valve 53 is fully opened.
When the delay time C1 <T1 has not yet elapsed, the routine proceeds to step S148, the twin turbo region continuation time count value C1 is incremented (C1 ← C1 + 1), and the routine exits.

After that, when the twin turbo region continuation time count value C1 reaches the exhaust control valve opening delay time T1 (C1 ≧ T1), steps S140 to S14.
Go to 1 and switch solenoid valve SO for the second exhaust control valve
L. Turn on 4. As a result, the first and second exhaust control valve switching solenoid valves SOL. 3, SOL. 4 is both O
N, the exhaust control valve 53 is fully opened, the rotation speed of the secondary turbocharger 50 is further increased, and the compressor 5
0b and the intake control valve 55, the compressor pressure (supercharging pressure) by the secondary turbocharger 50 increases, and FIG.
As shown in, the differential pressure D between the upstream and downstream of the intake control valve 55
PS increases.

Next, in step S142, the twin turbo region continuation time count value C1 is once cleared in order to measure the time after the exhaust control valve fully open control by the twin turbo region continuation time count value C1 (C1 ←
0). Then, in step S143, the twin turbo region duration time count value C1 representing the elapsed time after the exhaust control valve full-open control (SOL.4 is turned from OFF to ON) is compared with the intake control valve opening delay time T2, and C1 <T2 In Case of,
When it is determined that the opening condition of the intake control valve 55 is not satisfied, the twin turbo region continuation time count value C1 is incremented in step S148, and the routine exits.
If 1 ≧ T2, it is determined that the valve opening condition is satisfied and the routine proceeds to step S144, where the current differential pressure DPS and the intake control valve opening differential pressure DPSST are compared, and the intake valve opening start timing is reached. Determine if you did.

As a result, when DPS <DPSST, it is determined that the valve opening start timing has not been reached, and step S14
5, the upstream pressure Pu and the downstream pressure Pd of the intake control valve 55 become substantially equal when DPS ≧ DPSST, that is, the compressor 50 of the secondary turbocharger 50.
b between the intake control valve 55 and the secondary turbocharger 5
The supercharging pressure due to 0 increases and the primary turbocharger 40
It becomes substantially equal to the boost pressure due to the intake control valve, and it is judged that the intake control valve opening start timing has been reached, and the routine proceeds to step S146, where the intake control valve switching solenoid valve SOL. 2 is turned on to open the intake control valve 55.

As a result, supercharging from the secondary turbocharger 50 is started and the twin turbo state is established. Then, the process proceeds to step S147, and when the single-to-twin switching control is completed, the twin turbo mode determination flag F1 is set next time to shift to the twin turbo mode, and the routine is exited.

In step S144, DPS <DPS
When it is determined to be ST and the process proceeds to step S145, the count value C1 is set to the intake control valve opening delay time T2.
Is compared with a value obtained by adding the set value TDP to. And C1
<T2 + TDP, the process proceeds to step S148, the count value C1 is incremented, the routine is exited, and C
When 1 ≧ T2 + TDP, the routine proceeds to step S146, and even if the differential pressure DPS does not reach the intake control valve opening differential pressure DPSST, the intake control valve switching solenoid valve SOL. 2 for O
N, the intake control valve 55 is opened to shift to the twin turbo mode.

That is, when the differential pressure DPS by the differential pressure sensor 80 does not rise due to the failure of the differential pressure sensor 80 system, the exhaust control valve opening delay time T1 elapses, the exhaust control valve 53 is fully opened, and then the intake control is further performed. Valve open delay time T2
After the lapse of time, the intake control valve 55 is not opened at any time, and during this period, the boost pressure by the secondary turbocharger 50 is increased between the compressor 50b of the secondary turbocharger 50 and the intake control valve 55. (Compressor pressure) is contained, and the secondary turbocharger 50 and the intake control valve 55
The supercharging pressure between and increases abnormally, and the secondary turbocharger 50 is damaged due to surging. For this reason,
After the exhaust control valve 53 is fully opened, the intake control valve opening delay time T2 is added to the set value TDP (T2 + T).
DP), the differential pressure DPS is equal to the intake control valve opening differential pressure DPS.
Even if ST is not reached, by opening the intake control valve 55, the secondary turbocharger 50 and the intake control valve 55
The abnormal increase of the supercharging pressure between and is prevented, and the secondary turbocharger 50 is prevented from being damaged due to the failure of the differential pressure sensor 80 system.

The switching state from the single turbo state to the twin turbo state by the above single → twin switching control is shown in the time chart of FIG. As described above, in the single-to-twin switching control, first, the boost pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and the preliminary rotation speed of the secondary turbocharger 50 is increased. , Then the secondary turbocharger 50
The exhaust control valve opening delay time T1 gives the time required to increase the preliminary rotation speed of the exhaust control valve, and the exhaust control valve 53 is fully opened after the elapse of the delay time T1.

Then, the boost pressure between the compressor 50b of the secondary turbocharger 50 and the intake control valve 55 is increased by the secondary turbocharger 50, the differential pressure DPS is increased, and the exhaust control valve 53 is fully opened. , The operation delay time until the exhaust control valve 53 is fully opened is compensated by the intake control valve opening delay time T2, and after the delay time T2, the differential pressure DPS between the upstream side and the downstream side of the intake control valve 55 becomes the intake control valve. When the open differential pressure DPSST is reached, the intake control valve 55 is opened.

As a result, the primary turbocharger 4
From the single turbo state where only 0 operates, both turbochargers 4
The switching to the twin turbo state by the 0,50 operation is smoothly performed, and when the upstream pressure Pu and the downstream pressure Pd of the intake control valve become substantially equal, the intake control valve 55 is opened to perform the secondary turbo. Since supercharging from the supercharger 50 is started, it is possible to effectively and reliably prevent the occurrence of torque shock due to a temporary decrease in supercharging pressure that occurs when switching to the twin turbo state.

Next, the twin turbo mode will be described. When the twin-turbo mode determination flag F1 is set by the end of the single-to-twin switching control, or when the twin-turbo mode was set when the previous routine was executed, when this routine is executed, the process branches from step S101 to step S160 by F1 = 1. .

In step S160, the engine speed N
Based on, the turbo switching determination value table is referenced with interpolation calculation and the twin → single switching determination value Tp1 is set (see FIG. 7).
), In step S161, the basic fuel injection pulse width Tp representing the engine load and the twin-to-single switching determination value T
Compare with p1. If Tp> Tp1 and the current operating state is in the twin turbo region, the process proceeds from step S161 to step S162 to clear the determination value search flag F4 (F4 ← 0).

The judgment value search flag F4 is a flag which is set by setting a single turbo region continuation time judgment value T4 which will be described later, and the basic fuel injection pulse width representing the engine load when the engine operating condition is the twin turbo condition. Tp is twin → single switching judgment line L1 (Tp
It is cleared when it is in the twin turbo area after 1).

Next, in step S163, the single turbo region duration time count value C2 for counting the single turbo region duration time after the transition to the single turbo region is cleared, and then the process jumps to step S169. Then, steps S169 to S172
Then, the switching solenoid valve SOL. 1,
Intake control valve switching solenoid valve SOL. 2, first, second
Exhaust control valve switching solenoid valve SOL. 3, 4 are turned on, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 53 are both fully opened, the twin turbo mode determination flag F1 is set in step S173, and step S121 is performed. After returning to the twin turbo region continuation time count value C1, the routine is exited.

In the twin turbo mode, by closing the supercharging pressure relief valve 57, opening the intake control valve 55, and fully opening the exhaust control valve 53, in addition to the primary turbo supercharger 40, the secondary turbo supercharger is also provided. 50 becomes a full-scale operation, becomes a twin turbo state by supercharging operation of both turbochargers 40, 50, compressed air by supercharging of both turbochargers 40, 50 is supplied to the intake system, and output characteristics of FIG. As shown in
It is possible to obtain a torque curve during twin turbo with high shaft torque in the high rotation speed range.

On the other hand, in step S161, Tp ≦ Tp1,
That is, the current operating state is the single turbo region (see FIG.
If it is determined that the process has shifted to (see), the twin → single switching control is performed in step S164 and thereafter. In this twin-to-single switching control, the value of the judgment value search flag F4 is referred to in step S164, and if F4 = 0, step S
165, and if F4 = 1, step S1
Proceed to 67.

Therefore, after Tp ≦ Tp1, in the first routine execution, the process proceeds from step S164 to step S165 by F4 = 0, and the single turbo region continuation time judgment value table is referred to with interpolation calculation based on the engine speed N. After the single turbo region continuation time determination value T4 is set and the determination value search flag F4 is set (F4 ← 1) in step S166, the process proceeds to step S167.

Single turbo region duration determination value T4
Is the primary turbocharger 40 after the engine operating state shifts from the twin turbo region to the single turbo region.
It provides a delay time (delay time) for switching to the single turbo mode in which only the turbocharger operates, while improving the switching response from the twin turbo state to the single turbo state in the low engine speed range while improving the supercharger's A time value capable of avoiding unnecessary switching and preventing control hunting is obtained in advance by simulation or experiment using the engine speed N as a parameter, and this time value is converted into a time conversion value determined by the execution cycle of this routine. It is converted and stored in advance in a series of addresses in the ROM 102 as a table using the engine speed N as a parameter.

FIG. 13 shows the characteristics of the single turbo region continuation time judgment value table. The single turbo region duration determination value T4 based on this table is, for example, 4000r.
The maximum value of 2000 mse in the high rpm range above pm
In the low rotation speed region of 2400 rpm or less, the minimum value is set to 200 msec. And 2
In the medium speed range from 400 rpm to 4000 rpm, the single turbo range duration determination value T4 is increased in accordance with the increase in the engine speed N.

As a result, after the engine operating state shifts from the twin turbo region to the single turbo region, the timing at which the operation of both turbochargers 40 and 50 is switched to the operation of only the primary turbocharger 4 is the engine low speed region. In particular, when the engine speed drops significantly due to an upshift of the transmission, the operation in the low torque part in the twin turbo state is prevented, the drivability is improved, and the twin turbo state and the single turbo state are improved. Since the twin mode is switched to the single turbo mode in a region where the torque difference between the two states is small, it is possible to suppress the occurrence of torque shock due to the difference in torque at the time of switching.

In the engine speed range, the higher the engine speed is, the more delayed the timing at which the operation of both turbochargers 40, 50 is switched to the operation of only the primary turbocharger 40 is. Since a constant delay time is given by, the unnecessary switching of the supercharger due to the temporary decrease in the engine speed can be prevented as in the conventional case.

Next, in step S167, the single turbo region duration time count value C2 is incremented,
In step S168, the single turbo region duration determination value T4 and the single turbo region duration count value C2 are compared. If C2 <T4, the process proceeds to step S169 described above to maintain the twin turbo state, and C2 ≧
In the case of T4, the process proceeds from step S168 to step S174 to clear the count value C2 and then to step S10.
Return to 8 and switch from the twin turbo state to the single turbo state.

When switching from the twin-turbo state to the single-turbo state, the supercharging pressure control mode determination flag F2 is cleared in step S108, and the supercharging pressure relief valve 57 is opened to open the supercharging pressure relief valve 57 in step S113. Switching solenoid valve SOL. Turn OFF 1 and step S1
14, the intake control valve switching solenoid valve SOL. Turn off 2.

Then, by F2 = 0, step S11
It progresses from 5 to step S116, and steps S116 and S
At 118, the first exhaust control valve switching solenoid valve SO
L. 3, second switching solenoid valve for exhaust control valve SOL.
4 is turned off, the twin turbo mode discrimination flag F1 is cleared in step S119, and step S1
At S121 and S121, the differential pressure search flag F3 and the twin turbo region continuation time count value C1 are respectively cleared, and the routine is exited.

The switching state at this time is shown in the time chart of FIG. The switching from the twin-turbo state to the single-turbo state is performed after the engine operating range is changed from the twin-turbo range to the single-turbo range (Tp ≦ Tp
1) When the duration in the single turbo region continues for the set time (C2 ≧ T4), that is, when the predetermined delay time has elapsed after the transition to the single turbo region, the switching is performed. Then, after the delay time has elapsed, each switching solenoid valve S
OL. The surge tank 6 is placed in the pressure chamber of the boost pressure relief valve 57 so that the boost pressure relief valve 57 is opened by turning off the first to fourth valves.
The negative pressure from 0 is introduced, the negative pressure from the surge tank 60 is introduced into the pressure chamber of the intake control valve operating actuator 56 to close the intake control valve 55, and the exhaust control valve 53 is closed. Exhaust control valve actuating actuator 5
The positive pressure chamber 54a and the negative pressure chamber 54b of No. 4 are opened to the atmosphere.

As described above, the single turbo region continuation time determination value T4, which gives the delay time for switching from the twin turbo state to the single turbo state, is set to a short time in the region where the engine speed is low, and the single turbo state is set. The changeover to is accelerated. That is, as shown in FIG. 8, the single turbo region side with the twin-to-single switching determination line L1 as a boundary is given by the axial torque curve at the time of single turbo rather than the torque given by the axial torque curve at the time of twin turbo. When the twin-turbo state is maintained in this region when the torque is higher and the engine speed is greatly reduced due to the upshift, sufficient axial torque cannot be obtained and the drivability deteriorates. For this reason, in the engine low speed region, the single turbo region duration determination value T4 is set to a small value to accelerate the switching from the twin turbo state to the single turbo state, and to operate in the low torque portion in the twin turbo state. By swiftly switching to a single-turbo state in which the torque is high with the minimum required value, it is possible to secure drivability and suppress the occurrence of torque shock due to a torque step.

Further, when the engine speed is in the medium speed range, the single turbo region continuation time determination value T4 is set longer according to the increase in the engine speed, and the single turbo region continuation time determination value T4 is set to a constant time in the high engine speed region. The switching to the turbo state will be switched with a delay time according to the engine speed. As a result, it is possible to effectively and surely avoid unnecessary switching of the supercharger due to a temporary decrease in engine speed and engine load due to a shift change or the like, and control hunting can be prevented. .

[0120]

As described above, according to the present invention, the delay time when the operating range is changed from the twin turbo range to the single turbo range and the twin turbo mode is switched to the single turbo range is set according to the engine speed. Therefore, it is possible to improve the drivability by improving the switching response in the low engine speed region and avoiding the operation in the low torque portion in the twin turbo state.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine with a supercharger.

FIG. 2 is a circuit configuration diagram of an electronic control system.

FIG. 3 is a flowchart of a turbo switching control routine (No. 1)

FIG. 4 is a flowchart (part 2) of a turbo switching control routine.

FIG. 5 is a flowchart (part 3) of a turbo switching control routine.

FIG. 6 is a flowchart of a turbo switching control routine (4).

FIG. 7 is an explanatory diagram of a turbo switching determination value table.

FIG. 8 is an explanatory diagram showing output characteristics during single turbo and during twin turbo.

FIG. 9 is an explanatory diagram of an exhaust control valve small opening control region.

FIG. 10 is an explanatory diagram of an exhaust control valve opening delay time setting table.

FIG. 11 is an explanatory diagram of an intake control valve opening delay time setting table.

FIG. 12 is an explanatory diagram of an intake control valve opening differential pressure setting table.

FIG. 13 is an explanatory diagram of a single turbo region duration determination value table.

FIG. 14 is a time chart showing switching from the single turbo state to the twin turbo state.

FIG. 15 is a time chart showing switching from the twin turbo state to the single turbo state.

[Explanation of symbols]

1 engine 40 primary turbo supercharger 50 secondary turbo supercharger 100 electronic control unit (delay time setting means, single turbo switching means) N engine speed T4 single turbo region duration determination value (delay time)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3G005 EA16 EA26 FA04 GA03 GB19                       GB24 GB28 GC04 GD11 GD17                       GD18 GE09 HA02 HA04 HA05                       JA02 JA06 JA12 JA32 JA39                       JA42 JA45 JA51 JA52 JB04                       JB05 JB17 JB25                 3G092 AA01 AA05 AA15 AA18 AB02                       DB03 DB05 DC12 DF02 DG06                       DG09 EA01 EA11 EA16 EA17                       EA28 EA29 EC01 EC08 EC09                       FA03 FA10 GA14 GA17 HA05Z                       HA06Z HA15X HA16X HA16Z                       HE01Z

Claims (2)

[Claims] 1. An intake system and an exhaust system of an engine are provided with a primary turbocharger and a secondary turbocharger, and according to a comparison result of a switching determination value for switching a supercharger operating state and an engine load, A supercharger that determines a single turbo region in which only the primary turbocharger is supercharged to bring it into a single turbo state, and a twin turbo region in which both of the above turbochargers are supercharged into a twin turbo state. In a control device for an engine equipped with a A delay time setting means that is set according to the number of revolutions, and after the operating range changes from the twin turbo range to the single turbo range, When the duration of Gurutabo region is equal to or greater than the delay time, the control device of the supercharged engine, characterized in that a single turbo switching means for switching from the twin turbo state to single turbo state. 2. The control device for an engine with a supercharger according to claim 1, wherein the delay time setting means increases the delay time in response to an increase in engine speed.