JP3185165B2 - Control method of supercharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharger in which a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine, and the number of turbochargers to be operated is switched based on an operation state. The present invention relates to a method for controlling a charged engine.

[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 has been proposed in which an exhaust control valve is provided, and both control valves are opened and closed, whereby the number of turbochargers to be operated is appropriately switched according to an engine operation range.

[0003] In this turbocharged engine, the engine operation region is divided into a single turbo region in a low speed region and a twin turbo region in a high speed region. When the operation region is in the single turbo region, the intake control valve is closed. When the valve is closed and the exhaust control valve is closed or opened slightly (to pre-rotate the secondary turbocharger), only the primary turbocharger is supercharged. The valves are both opened to operate the turbochargers in a supercharging manner, so that the output performance can be improved from a low speed range to a high speed range.

As shown in FIG. 21, in this type of supercharged engine, when viewed from the relationship between the shaft torque and the engine speed (however, the engine load is constant), only the primary turbocharger is supercharged. In contrast to the torque curve TQ1 at the time of the single turbo operation in the supply operation, the torque curve TQ2 at the time of the twin turbo operation in which the supercharging operation is performed at both the turbocharges is higher at a certain rotational speed N0 or higher, and a high shaft torque can be obtained. In the region where the rotational speed is lower than N0, the operation of the secondary turbocharger causes the shaft torque at the time of the twin turbo to decrease rather. Therefore, the point C where the two torque curves match in the figure
Thus, the state is switched from the single turbo state to the twin turbo state.

However, since the rotational speed at which the two torque curves match depends on the engine load, the point of coincidence between the two torque curves is determined in advance in accordance with the engine load and the engine speed by experiments or the like, and as shown in FIG. → Set the twin switching judgment line L2, and when the engine operation area shifts from the low-speed single turbo area to the high-speed twin turbo area after the single → twin switching judgment line L2, open the exhaust control valve slightly. Or maintain a small opening, increase the rotation speed of the secondary turbocharger, fully open the exhaust control valve after the set time elapses, increase the compressor pressure by the secondary turbocharger, and then open the intake control valve Only the primary turbocharger is switched from the single turbo state of supercharging operation to the twin turbo state of supercharging operation of both turbochargers. In addition, a torque fluctuation caused by a decrease in the supercharging pressure at the time of switching from the single turbo state to the twin turbo state is prevented to prevent the occurrence of torque shock (see, for example, Japanese Patent Application Laid-Open No. 3-260326).

Further, as shown in FIG. 6, in order to prevent control hunting at the time of switching the number of turbochargers to be operated, the single-to-twin switching determination line L2 is switched from the twin-turbo state to the single-turbo state. The hysteresis is provided by setting the twin-to-single switching determination line L1 for judging the condition to the low rotation side.

[0007]

When the supercharging pressure control is performed by using the absolute pressure, the differential pressure between the target supercharging pressure and the atmospheric pressure becomes large in high altitude running at a low atmospheric pressure. Attempting to obtain the supercharging pressure results in a relatively high speed of the turbocharger. When the operation is switched to the twin turbo state, exhaust gas with a high exhaust flow rate is introduced only into the primary turbocharger until the exhaust control valve is fully opened, so that the primary turbocharger is likely to be in an overspeed state.

However, in the above prior art, the timing of switching from the single turbo state to the twin turbo state is determined based only on the engine operating state such as the engine speed and the engine load irrespective of the atmospheric pressure fluctuation. ,
In high-altitude traveling at low atmospheric pressure, the primary turbocharger is in an over-rotation state as described above, reaches a critical rotational speed, and may cause surging and damage. In addition, even in the same engine operating state, since the rotation speed increase rate of the turbocharger changes due to the air pressure fluctuation, the air pressure fluctuation, for example, switching from a single turbo state to a twin turbo state during high altitude traveling and low altitude traveling. The operation feeling due to the start of operation of the secondary turbocharger at the start of the operation is different.

The present invention has been made in view of the above circumstances, and a single-to-twin switching determination line for determining whether to switch from a single turbo state to a twin turbo state is corrected in accordance with the atmospheric pressure. the timing switching is corrected to, thereby preventing excessive rotation of the primary turbocharger, substantially to also drive feeling due to a secondary turbocharger operation start regardless of change in atmospheric pressure, the air
Primary turbocharger more properly regardless of pressure change
It is an object of the present invention to provide a control method of a supercharged engine capable of preventing overspeed of the engine.

[0010]

[0011]

[0012]

Means for Solving the Problems To achieve the above object,
Therefore, according to the present invention , a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine,
An intake control valve and an exhaust control valve are respectively installed in the intake and exhaust systems connected to the secondary turbocharger, and both control valves are opened at high speeds to supercharge both turbochargers. The engine operation region is divided into a twin turbo region where the operation is performed and a single turbo region where only the primary turbocharger is supercharged by closing or slightly opening the exhaust control valve while closing the intake control valve in the low speed region. Then, after the operating region shifts from the single turbo region to the twin turbo region at a single-to-twin switching determination line set based on the single-to-twin switching determination value set based on the engine operating region, exhaust is performed after a lapse of a set time. Fully open the control valve,
Then, in the control method of the supercharged engine in which the intake control valve is opened and only the primary turbocharger is switched from the single turbo state in which the supercharging operation is performed to the twin turbo state in which both the turbocharger is supercharged, the engine operation is performed. Based on the condition
A single to twin switching determination basic value is set in advance by referring to a table in which a single to twin switching determination basic value at standard atmospheric pressure is stored, and based on the atmospheric pressure, a smaller value for single to twin atmospheric pressure is lower as the atmospheric pressure is lower. Set the correction coefficient, and change the basic
The single to twin switching judgment value is corrected by the twin atmospheric pressure correction coefficient, and based on the engine operating condition.
In a single turbo state and at standard atmospheric pressure
Primer for judging overspeed of Imari turbocharger
A table in which basic values for the determination of over-rotation
Refer to and set the primary turbo overspeed judgment basic value,
Based on the atmospheric pressure, the lower the atmospheric pressure, the smaller the judgment value.
Set the air pressure correction coefficient, and
Corrects the constant basic value with the judgment value atmospheric pressure correction coefficient and
Set the turbo overspeed judgment value and elapse the above set time
Before the engine operating area is above the primary turbo overspeed
Twist the primary turbo overspeed judgment line based on the judgment value.
Exhaust gas control valve fully open
Characterized in that that.

[0013]

[0014]

[0015]

According to the present invention, after the engine operation region shifts from the single turbo region to the twin turbo region at the boundary of the single to twin switching determination line, the exhaust control valve is fully opened after a lapse of a set time, and then the intake control valve is opened. The valve is switched from the single turbo state in which only the primary turbocharger is in the supercharging operation to the twin turbo state in which the supercharging operation is in the both turbochargers. The single to twin switching determination line is set by a single to twin switching determination value obtained by correcting the single to twin switching determination basic value at the standard atmospheric pressure by a smaller single to twin atmospheric pressure correction coefficient as the atmospheric pressure is lower. The lower the atmospheric pressure, the lower the rotational speed. As a result, the exhaust control valve is fully opened and the exhaust flow introduced into the primary turbocharger is dispersed to the secondary turbocharger, and the switching from the single turbo state to the twin turbo state is advanced. Where the engine is running
Switching from single turbo state to twin turbo state
Single to twin switching judgment line for judging replacement
Moved from single turbo range to twin turbo range
Later, before the set time elapses, the single turbo state and
Over-rotation of the primary turbocharger at standard atmospheric pressure
Increase the primary turbo overspeed judgment base value for judgment.
The lower the atmospheric pressure, the smaller the judgment value.
Primer based on the corrected primary turbo overspeed judgment value
Cross the re-turbo overspeed judgment line to the twin turbo area
The exhaust control valve is fully opened and the primer
The exhaust flow introduced into the re-turbo turbocharger is a secondary turbo
Immediately distributed to the turbocharger.

[0016]

[0017]

[0018]

An embodiment of the present invention will be described below with reference to the drawings. First, referring to FIG. 19, the overall configuration of a supercharged engine to which the present invention is applied will be described.

Reference numeral 1 denotes an engine body of a horizontally opposed engine (a four-cylinder engine in the present embodiment). A combustion chamber 5, an intake port 6, an exhaust port 7, an ignition port are provided in left and right banks 3 and 4 of a crankcase 2. A plug 8, a valve operating mechanism 9, and the like are provided. The left bank 3 has # 2 and # 4 cylinders, and the right bank 4 has # 1 and # 3 cylinders. Also, right after the left and right banks 3 and 4,
A primary turbocharger 40 and a secondary turbocharger 50 are provided, respectively. As an exhaust system, a common exhaust pipe 10 from both the left and right banks 3 and 4 is communicated with turbines 40 a and 50 a of both turbochargers 40 and 50, and an exhaust pipe 11 from the turbines 40 a and 50 a is connected to one exhaust pipe 12. And is communicated with the catalytic converter 13 and the muffler 14. The primary turbocharger 40 is a small-capacity low-speed type having a large supercharging capacity in a low-medium-speed region, whereas the secondary turbocharger 50 is a large-capacity large-capacity having a large supercharging capability in a medium-high speed region. It is a high-speed type. For this reason, the primary turbocharger 40 has a smaller capacity, so that the exhaust resistance increases.

As an intake system, intake pipes 16 and 17 branched into two from the downstream of the air cleaner 15 are connected to compressors 40b and 50b of the turbochargers 40 and 50, respectively. 1
8, 19 are communicated with the intercooler 20. The intercooler 20 communicates with the chamber 22 via a throttle body 27 having a throttle valve 21, and the chamber 22 communicates with the 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 check valve 26 that opens with a negative pressure with an idle control valve (ISCV) is provided in a bypass passage 24 that bypasses the throttle valve 21 and communicates the intake pipe immediately downstream of the air cleaner 15 with the intake manifold 23. This is provided to control the amount of intake air at the time of idling or deceleration.

As a fuel system, an intake manifold 2 is provided.
An injector 30 is disposed immediately upstream of the intake port 6 in each cylinder 3 and has a fuel pump 31 having a fuel pump 31.
A fuel passage 33 from the fuel tank 2 is provided with a filter 34 and a fuel pressure regulator 35 and communicates with the injector 30. The fuel pressure regulator 35 adjusts according to the intake pressure in the intake manifold, whereby the fuel pressure supplied to the injector 30 is always maintained at a constant level with respect to the intake pressure. The injector 30 is driven by the pulse width of the injection signal from 100 to control the fuel injection amount. As an ignition system, an ignition coil 8 connected to each ignition plug 8 is provided.
They are connected so that an ignition signal from the igniter 36 is input for each a.

Next, the operation system of the primary turbocharger 40 will be described.

The primary turbocharger 40 uses the energy of exhaust gas introduced into the turbine 40a to operate the compressor 4
Ob is driven to rotate so that air is inhaled and pressurized to constantly supercharge. On the turbine 40a side, a primary wastegate valve 41 provided with a diaphragm type actuator 42 is provided. The pressure chamber of the actuator 42 communicates with a control pressure passage 44 having an orifice 48 from immediately downstream of the compressor 40b, and communicates so as to open the wastegate valve 41 with good response when the supercharging pressure rises above a set value. You. The control pressure passage 44 further communicates the supercharging pressure with a duty solenoid valve D.SOL.1, which leaks to the upstream side of the compressor 40b, and the duty solenoid valve D.SOL.1 generates a predetermined control pressure. Acting on the actuator 42, the opening degree of the wastegate valve 41 is changed to control the supercharging pressure. Here, the duty solenoid valve D.SO
L.1 is activated by a duty signal from the electronic control unit 100 described later. When the duty ratio of the duty signal is small, the opening degree of the wastegate valve 41 is increased with a high control pressure to reduce the supercharging pressure, As the ratio increases, the control pressure decreases due to an increase in the leak amount, and the opening degree of the wastegate valve 41 is reduced to increase the supercharging pressure.

On the other hand, in order to prevent a decrease in compressor rotation and the occurrence of intake noise when the throttle valve is rapidly closed, a portion between the outlet side of the intercooler 20 near the throttle valve 21 and the upstream of the compressor 40b is provided downstream of the compressor 40b. Is connected to the bypass passage 46. An air bypass valve 45 is provided in the bypass passage 46 so as to introduce a manifold negative pressure through the passage 47 when the throttle valve is suddenly closed, and to quickly open and leak pressurized air trapped downstream of the compressor 40b.

The operation system of the secondary turbocharger 50 will be described.

Similarly, the secondary turbocharger 50 is a turbocharger in which the turbine 50a and the compressor 50b are rotationally driven by exhaust to supercharge, and a secondary wastegate valve 51 having an actuator 52 is provided on the turbine 50a side. . The exhaust pipe 10 upstream of the turbine 50a is provided with a downstream-opening exhaust control valve 53 having a diaphragm-type actuator 54, and a butterfly-type intake control having a similar actuator 56 downstream of the compressor 50b. A valve 55 is provided, and a supercharging pressure relief valve 57 is provided in a relief passage 58 communicating between the upstream and downstream of the compressor 50b.

The operation system of each of these valves will be described.

First, the surge tank 60 as a negative pressure source is connected to the intake manifold 23 through a passage 61 having a check valve 62.
, The negative pressure is stored and the pulsating pressure is buffered when the throttle valve 21 is fully closed. Further, a switching solenoid valve SOL. For the supercharging pressure relief valve that opens and closes the supercharging pressure relief valve 57.
1, an intake control valve switching solenoid valve SOL. 2. First and second exhaust control valve switching solenoid valves SOL. 3, 4, a duty solenoid valve for controlling the exhaust control valve 53 to open small.
SOL.2 and a secondary wastegate valve switching solenoid valve SO for opening and closing the secondary wastegate valve 51
L. W. Each switching solenoid valve SOL. W, SO
L. Numerals 1 to 4 denote negative pressure through a negative pressure passage 63 from the surge tank 60 and a positive pressure passage 64 that communicates downstream of the intake control valve 55 in response to ON / OFF signals from the electronic control unit 100.
a, 64b is selected and guided to the actuator side by the control pressure passages 70a to 74a, and the secondary wastegate valve 51, the supercharging pressure relief valve 57, and the control valves 55, 53 are controlled. Operate. The duty solenoid valve D.SOL.2 is operated by a duty signal from the electronic control unit 100 to control the positive pressure chamber 54 of the actuator 54.
The positive pressure acting on a is adjusted, and the exhaust control valve 53 is controlled to be small open.

The switching solenoid valve SOL. 1, when the energization is turned off, the positive pressure passage 64a
The side is closed and the side of the negative pressure passage 63 is opened, and the negative pressure is guided to the pressure chamber in which the spring of the supercharging pressure relief valve 57 is housed via the control pressure passage 71a, so that the supercharging is performed against the urging force of the spring. The pressure relief valve 57 is opened. When it is turned on, the negative pressure passage 63 is closed, the positive pressure passage 64a is opened, and the positive pressure is introduced into the pressure chamber of the supercharging pressure relief valve 57 to close the supercharging pressure relief valve 57.

The switching solenoid valve SOL. 2
Is turned off, the atmosphere port is closed, the side of the negative pressure passage 63 is opened, and the actuator 56 is controlled via the control pressure passage 72a.
The intake control valve 55 is closed against the urging force of the spring by introducing a negative pressure into the pressure chamber in which the
When this is done, the side of the negative pressure passage 63 is closed, the atmosphere port is opened, and the atmospheric pressure is guided to the pressure chamber of the actuator 56, so that the intake control valve 55 is opened by the urging force of the spring in the pressure chamber.

The switching solenoid valve SOL. W is turned off only when the electronic control unit 100 determines 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. And, the switching solenoid valve SOL. W is disposed in the actuator 52 by closing the passage 65 communicating with the upstream of the intake control valve 55 when opened and opening the atmosphere port to introduce atmospheric pressure to the actuator 52 through the control pressure passage 70a. The secondary wastegate valve 51 is closed by the biasing force of the spring. Further, when turned on, the atmosphere port is closed and the passage 65 side is opened, and the supercharging pressure downstream of the secondary turbocharger 50 when both the turbochargers 40 and 50 are operated is guided to the actuator 52, and according to this supercharging pressure, When the secondary wastegate valve 51 is opened, the supercharging pressure is relatively reduced when using regular gasoline as compared with when using high-octane gasoline.

Further, the first exhaust control valve switching solenoid valve SOL. The control pressure passage 73a from the exhaust control valve 53
The positive pressure chamber 54a of the actuator 54 that operates
Switching solenoid valve SOL. The control pressure passages 74a from the pressure chambers 4 communicate with the negative pressure chambers 54b containing the springs of the actuators 54, respectively. And
Both switching solenoid valves SOL. 3, 4 are both OFF, the first exhaust control valve switching solenoid valve SOL. 3 closes the positive pressure passage 64b and opens the atmosphere port, and the second exhaust control valve switching solenoid valve SOL. Numeral 4 closes the negative pressure passage 63 and opens the atmosphere port, whereby both chambers 54a and 54b of the actuator 54 are opened to the atmosphere, and the exhaust control valve 53 is fully closed by the urging force of the spring provided in the negative pressure chamber 54b. . Further, both switching solenoid valves SOL. When both 3 and 4 are ON, the respective atmosphere ports are closed, and the first exhaust control valve switching solenoid valve SOL. 3 is a positive pressure passage 64b
Side, and the second exhaust control valve switching solenoid valve SO
L. 4 opens the side of the negative pressure passage 63 to guide the positive pressure to the positive pressure chamber 54a and the negative pressure to the negative pressure chamber 54b of the actuator 54, and fully open the exhaust control valve 53 against the urging force of the spring.

The first exhaust control valve switching solenoid valve SOL. The orifice 67 is provided in the control pressure passage 73a from
The downstream side of the orifice 67 and the intake pipe 16 are provided.
A leak passage 66 communicates with the duty solenoid valve D. for controlling the small opening of the exhaust control valve.
SOL.2 is provided. Then, the first exhaust control valve switching solenoid valve SOL. 3 is ON, the positive pressure is supplied to the positive pressure chamber 54a of the actuator 54 and the negative pressure chamber 54b is opened to the atmosphere, and the positive pressure is leaked by the duty solenoid valve D.SOL. Small open.
Here, when the duty ratio of the duty signal from the electronic control unit 100 is large, the duty solenoid valve D.SOL.2 reduces the positive pressure acting on the positive pressure chamber 54a due to an increase in the amount of leakage, thereby causing the exhaust control valve 53 to operate. As the opening degree is reduced and the duty ratio becomes smaller, the leak amount is reduced, the positive pressure is kept high, and the opening degree of the exhaust control valve 53 is increased.
Then, when the engine operation area is in the predetermined exhaust control valve small opening control mode area under the single turbo mode, the boost pressure is feedback controlled by the opening degree of the exhaust control valve 53 by the duty solenoid valve D.SOL.2, With this supercharging pressure control, the exhaust control valve 53 is slightly opened.

Next, various sensors will be described.

A differential pressure sensor 80 is provided to detect a differential pressure between upstream and downstream of the intake control valve 55, and an absolute pressure sensor 81 is controlled by a switching solenoid valve 76 to increase the intake pipe pressure (intake pressure in the intake manifold 23). It is provided to select and detect the atmospheric pressure.

A knock sensor 82 is attached to the engine body 1, and a water temperature sensor 83 is exposed to a cooling water passage communicating the left and right banks 3, 4.
2 The sensor 84 is facing. Further, a throttle sensor 85 having a throttle opening sensor and an idle switch for detecting the throttle fully closed in the throttle valve 21.
, And an intake air amount sensor 86 is disposed immediately downstream of the air cleaner 15.

A crank rotor 90 is axially mounted on a crankshaft 1a supported by the engine body 1. A crank angle sensor 87, such as an electromagnetic pickup, is provided on the outer periphery of the crank rotor 90. further,
A cam rotor 91 connected to a cam shaft of the valve mechanism 9 is provided with a cam angle sensor 88 for discriminating cylinders, which is composed of an electromagnetic pickup or the like.

The crank angle sensor 87 and the cam angle sensor 88 detect protrusions (or slits) formed at predetermined intervals on the crank rotor 90 and the cam rotor 91, respectively, in accordance with the operation of the engine. Output to control device 100. Then, the electronic control unit 100 calculates the engine speed from the interval time of the crank pulse (the detected protrusion), and
The ignition timing, fuel injection start timing, and the like are calculated, and further, cylinder discrimination is performed from the input pattern of the crank pulse and the cam pulse.

Next, the configuration of the electronic control system will be described with reference to FIG. The electronic control unit (ECU) 100
The microcomputer mainly includes a microcomputer in which a PU 101, a ROM 102, a RAM 103, a backup RAM 104, and an I / O interface 105 are connected via a bus line, and includes a constant voltage circuit 106 and a drive circuit 107 for supplying a predetermined stabilized power to each unit. It is built in.

The constant voltage circuit 106 includes the ECU relay 9
5, and a relay coil of the ECU relay 95 is connected to the battery 96 via an ignition switch 97. The constant voltage circuit 10 is connected to the battery 96.
6 is directly connected, and further, the fuel pump 31 is connected via a relay contact of the fuel pump relay 98.

That is, when the ignition switch 97 is turned on and the relay contact of the ECU relay 95 is closed, the constant voltage circuit 106 supplies control power to each section, and the ignition switch 97 is turned off.
When the flip-flop is turned on, power for backup is supplied to the backup RAM 104.

The I / O interface 105
Sensor 80-88, vehicle speed sensor 8
9 and a battery 96 are connected. Also, I / O
The igniter 36 is connected to the output port of the interface 105, and
CV25, injector 30, each switching solenoid valve 7
6, SOL. W, SOL. 1-4, a duty solenoid valve D.SOL.1,2, and a relay coil of a fuel pump relay 98 are connected.

Then, the ignition switch 97 is set to O
N, the ECU relay 95 is turned on, and the constant voltage circuit 1
A constant voltage is supplied to each unit via the control unit 06, and the ECU 100 executes various controls. That is, in the ECU 100, the CPU 101 inputs the detection signals from the various sensors 80 to 89 via the I / O interface 105 based on the calculation program stored in the ROM 102, and outputs the various signals stored in the RAM 103 and the backup RAM 104. Various control amounts are calculated based on the data, the fixed data stored in the ROM, and the table values. Then, the fuel pump relay 98 is turned on by the drive circuit 107.
N, the fuel pump 31 is energized and driven, and each of the switching solenoid valves 76, SOL.
W, SOL. The ON / OFF signals are output to 1-4 and the duty signals are output to the duty solenoid valves D.SOL.1 and 2 to perform turbocharger operation number switching control and supercharging pressure control.
A drive pulse width signal corresponding to the calculated fuel injection amount is output to the injector 30 of the corresponding cylinder at a predetermined timing to perform fuel injection control, and an ignition signal is output to the igniter 36 at a predetermined timing to control ignition timing. Run
A control signal is output to the ISCV 25 to execute idle speed control and the like.

Next, the supercharger operation number switching control by the ECU 100 will be described with reference to the flowchart shown in the turbo switching control routine of FIGS. This turbo switching control routine is executed every set time (for example, 10 msec) after turning on the ignition switch 97.

When the power is supplied to the ECU 100 by turning on the ignition switch 97, the system is initialized (each flag and each count value are cleared). First, in step S1, the twin turbo mode discrimination flag F1 is set.
Refer to the value of. If the twin turbo mode discrimination flag F1 has been cleared, the process proceeds to step S2,
If set, the process proceeds to step S60. The twin turbo mode discrimination flag F1 is cleared when the current control state is the single turbo mode in which only the primary turbocharger 40 performs the supercharging operation.
Set in the twin turbo mode in which the supercharger 50 operates.

In the following description, the single turbo mode will be described first, then the single-to-twin switching control, and finally the twin turbo mode will be described.

Immediately after the ignition switch 97 is turned on and when the current control state is the single turbo mode, F
Since 1 = 0, the process proceeds to step S2.

In step S2, based on the engine speed N, the turbo switching decision value table is referred to with interpolation calculation to set a single to twin switching decision basic value TP2B. The single to twin switching determination basic value TP2B is for determining switching from the single turbo mode to the twin turbo mode at the standard atmospheric pressure (760 mmHg). As shown in FIG. 6, in the turbo switching determination value table, the single turbo mode switching from the single turbo mode to the twin turbo mode is performed based on the relationship between the engine speed N and the engine load (basic fuel injection pulse width in this embodiment) TP. → Twin switching judgment line L2 and vice versa, twin switching from twin turbo mode to single turbo mode →
The single switching determination line L1 is previously obtained from experiments or the like under standard atmospheric pressure, and a single turbo region and a twin turbo region are set. Then, each line L2, L
The basic values TP2B and TP1B for the single-to-twin switching determination and the twin-single switching determination basic value TP1B are stored in advance in a series of addresses in the ROM 102 as a table using the engine speed N as a parameter.

Here, in order to prevent torque fluctuation at the time of switching, the torque curve TQ1 in the single turbo state and the torque curve TQ2 in the twin turbo state of the output characteristics of FIG. Point C
Therefore, as shown in FIG. 6, the load is set to a low load side according to an increase in the engine speed N from a high load in the low and medium speed ranges. Further, as shown in the figure, in order to prevent control hunting at the time of switching the number of operating turbochargers, the twin-single switching determination line L1 is
The hysteresis has a relatively wide width on the low rotation speed side with respect to the single-to-twin switching determination line L2.

Then, the process proceeds to step S3, where the single to twin atmospheric pressure correction coefficient table is referenced with interpolation calculation based on the atmospheric pressure (absolute pressure) ALT, and the single to twin atmospheric pressure correction coefficient KTWNALT (0 <KTWNALT ≦ 1.0) is set. As shown in FIG. 7, this single-to-twin atmospheric pressure correction coefficient table contains the standard atmospheric pressure (760 mmH
g) is set to 1.0, and a single to twin atmospheric pressure correction coefficient KTWNALT of a smaller value as the atmospheric pressure decreases is stored.

Then, in step S4, the single →
The twin switching determination basic value TP2B is corrected by a single to twin atmospheric pressure correction coefficient KTWNALT to set a single to twin switching determination value TP2.

Then, the process proceeds to a step S5, wherein the single to twin switching determination value TP2 is compared with the current basic fuel injection pulse width TP (hereinafter referred to as "engine load").
In the case of P2, the process proceeds to step S6, and in the case of TP ≧ TP2, the process branches to step S30 and shifts to single-twin switching control for switching from the single turbo state to the twin turbo state.

The above single-twin switching judgment value TP2 is
The single to twin atmospheric pressure correction coefficient KTWNALT is corrected to a smaller value as the atmospheric pressure ALT is lower. For this reason, as the atmospheric pressure ALT becomes lower, only the primary turbocharger 40 is changed from the single turbo state in which the supercharging operation is performed to the two turbochargers 4 according to the single-to-twin switching determination value TP2.
The single-to-twin switch determination line L2 for determining switching to the twin turbo state of the 0,50 supercharging operation is lower in load than the case of the standard atmospheric pressure shown by the solid line in FIG. It is corrected to the low rotation side.

As a result, the timing at which the engine operation region shifts from the single turbo region to the twin turbo region on the boundary of the single-to-twin switch determination line L2 is advanced, and the shift from the single turbo mode to the single-to-twin switch control is performed. The switching from the single turbo state to the twin turbo state is advanced earlier.

When the supercharging pressure control is performed by the absolute pressure, the differential pressure between the target supercharging pressure and the atmospheric pressure becomes larger as the atmospheric pressure ALT becomes lower, such as when traveling at high altitude where the atmospheric pressure ALT is low. If pressure is to be obtained, the rotation speed of the turbocharger becomes relatively high. As a result, the rate of increase in the number of revolutions of the primary turbocharger 40 with an increase in the engine speed N and the load TP representing the engine operating state also increases. In the single turbo state in which only the primary turbocharger 40 is in the supercharging operation, most of the exhaust gas is discharged from the primary turbocharger 40.
As the atmospheric pressure ALT is lower, the engine operating region in which the primary turbocharger 40 is in an overspeed state is expanded to a low load and a low speed side. As described above, this is remarkable when the primary turbocharger 40 has a low-speed small capacity. Therefore, as the atmospheric pressure ALT becomes lower, the single turbo mode based on the engine operating state changes to the single →
By advancing the timing of shifting to the twin switching control and the fully opening control timing of the exhaust control valve 53, which will be described later, the exhaust flow introduced into the primary turbocharger 40 by fully opening the exhaust control valve 53 is changed to the secondary turbocharger. 50 to prevent over-rotation of the primary turbocharger 40. Thereby, the primary turbocharger 40
As a result, the occurrence of surging due to an over-rotation state caused by an increase in the exhaust pressure and the exhaust flow rate and reaching the critical rotational speed is prevented regardless of a change in the atmospheric pressure ALT, and damage is prevented. Further, even in the same engine operation state, the rotation speed increase rate of the primary turbocharger 40 changes under the single turbo state due to the atmospheric pressure fluctuation, and the operation feeling due to the start of the operation of the secondary turbocharger 50 changes.
The lower the atmospheric pressure ALT is, the earlier the switching to the twin turbo state is made, so that the driving feeling accompanying the start of the operation of the secondary turbocharger 50 is substantially the same regardless of the atmospheric pressure change (for example, traveling at high altitude and traveling at low altitude). be able to.

On the other hand, in step S5, if TP <TP2 and the process proceeds to step S6, the single turbo mode control is performed.

In step S6, the value of the supercharging pressure control mode determination flag F2 is referred to. This supercharging pressure control mode discrimination flag F2 indicates that the current operation region is in the exhaust control valve small opening control mode 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 pre-rotated. Is set when it is out of the area.

Therefore, when the ignition switch 97 is
Immediately after N, the initial setting is performed, and when the operation region is outside the exhaust control valve small-opening control mode region during the previous execution of the routine, the process proceeds to step S7 because F2 = 0.
It is determined whether or not the current operation range has shifted to the exhaust control valve small opening control mode range based on the condition determination in steps S7 to S9.

The transition to the exhaust control valve small-opening control mode area is determined based on the relationship between the engine speed N and the intake pipe pressure (supercharging pressure) P as shown in FIG. On the lower rotation speed and lower load side, that is, under the single turbo mode, the set value N2 (for example, 265
0 rpm), P2 (for example, 1120 mmHg), and the throttle opening TH is equal to the set value TH2.
If it is not less than (for example, 30 deg), it is determined that it has moved into the area.

That is, in step S7, the engine speed N is compared with the set value N2, in step S8, the intake pipe pressure P is compared with the set value P2, and in step S9, the throttle opening TH and the set value TH2 are compared. Compare. And N <N
If 2, P <P2, or TH <TH2, the process proceeds to step S10, where it is determined that the current operation region is outside the exhaust control valve small opening control mode region, and the supercharging pressure control mode determination flag F2 is cleared. Also, N ≧ N2 and P ≧ P2 and T
If H ≧ TH2, the process proceeds to step S11, where it is determined that the current operation region has shifted to the exhaust control valve small opening control mode region, and a supercharging pressure control mode determination flag F2 is set.

Then, the process proceeds to a step S12, wherein the switching solenoid valve SOL. Turn 1 off,
In step S13, the switching solenoid valve SO for the intake control valve
L. 2 is turned OFF. Next, when the process proceeds to step S14,
With reference to the value of the supercharging pressure control mode determination flag F2, F2 =
0, the process proceeds to step S15, and the first exhaust control valve switching solenoid valve SOL. 3 is turned off, and step S1
6 and the second exhaust control valve switching solenoid valve SOL. 4 is turned OFF.

Thereafter, at steps S17 to S19, the twin turbo mode discrimination flag F1, the differential pressure search flag F3 described later, and the control valve switching time count value C1 are cleared, and the routine exits.

Accordingly, in the single turbo mode and in the low-rotation, low-load operation region outside the exhaust control valve small-open control mode region, each switching solenoid valve SOL. 1 to 4 are all turned off. Thus, the boost pressure relief valve 57 is provided with a boost pressure relief valve switching solenoid valve SOL. 1, the negative pressure from the surge tank 60 is introduced into the pressure chamber to open the valve against the urging force of the spring, and the intake control valve 55 is switched to the intake control valve switching solenoid valve SOL. 2 O
When a negative pressure is introduced into the pressure chamber of the actuator 56 by the FF, the valve is closed against the urging force of the spring.
Further, the exhaust control valve 53 is provided with a switching solenoid valve SOL. Actuator 54 by turning off 3, 4
When the atmospheric pressure is introduced into both chambers 54a and 54b, the valve is closed by the urging force of the spring.

When the exhaust control valve 53 is closed, the introduction of exhaust gas to the secondary turbocharger 50 is shut off, the secondary turbocharger 50 becomes inactive, and the single turbocharger in which only the primary turbocharger 40 operates. State. In addition, the closing of the intake control valve 55 prevents the supercharging pressure from the primary turbocharger 40 from leaking to the secondary turbocharger 50 via the intake control valve 55, and reduces the supercharging pressure. Is prevented.

In the single turbo mode and out of the exhaust control valve small opening control mode range, or in the twin turbo mode described later, the supercharging pressure feedback control is not described in detail here, but the primary west This is performed using only the gate valve 41. The supercharging pressure control uses the absolute pressure, sets a target supercharging pressure based on the engine operating state, compares the intake pipe pressure detected by the absolute pressure sensor 81 with the actual supercharging pressure P, According to the comparison result, for example, the duty solenoid valve is controlled by PI control.
An ON duty (duty ratio) for D.SOL.1 is calculated, and a duty signal of this ON duty is output to the duty solenoid valve D.SOL.1 to control the primary wastegate valve 41.

On the other hand, if it is determined in step S11 that the current operation region is within the exhaust control valve small opening control mode region and the supercharging pressure control mode determination flag F2 is set, the process proceeds through steps S12 to S14. Proceed to step S20,
The first exhaust control valve switching solenoid valve SOL. Turn ON only 3 Therefore, the first exhaust control valve switching solenoid valve SOL. 3 turns on the positive pressure chamber 5 of the actuator 54.
A positive pressure is introduced into 4a, and the exhaust control valve 53 is opened.

In this exhaust control valve small opening control mode, the exhaust control valve small opening control routine shown in FIG. 5 is executed every set time (for example, 480 msec). The supercharging pressure feedback control is performed, and accordingly, the exhaust control valve 53 is slightly opened. That is, referring to the value of the supercharging pressure control mode determination flag F2 in step S100 in FIG. 5, the routine exits when F2 = 0, and proceeds to step S101 when F2 = 1 and the exhaust control valve small opening control mode. , A switching solenoid valve SOL. Determine the energization state for 1
SOL. If 1 = ON, the routine exits and SOL.
When 1 = OFF, the process proceeds to step S102, where the target supercharging pressure based on the absolute pressure is compared with the actual supercharging pressure P detected by the absolute pressure sensor 81, and according to the comparison result, for example, P
ON duty (duty ratio) for duty solenoid valve D.SOL.2 for exhaust control valve small opening control by I control
And outputs a duty signal of this ON duty to the duty solenoid valve D.SOL.2 to execute the supercharging pressure feedback control. Therefore, the positive pressure chamber 54a of the actuator 54 is operated by the duty solenoid valve D.SOL.2.
As shown in FIG. 17, the exhaust control valve 53 is opened slightly and the supercharging pressure feedback control is performed using only the exhaust control valve 53, as shown in FIG. A part of the exhaust gas is supplied to the turbine 50a of the secondary turbocharger 50 by the small opening of the exhaust control valve 53, and the secondary turbocharger 50 is pre-rotated to prepare for the transition to the twin turbo state.

In this state, since the intake control valve 55 is closed, the supercharging pressure (between the secondary turbocharger 50 and the downstream of the compressor 50b of the secondary turbocharger 50) At this time, the supercharging pressure is leaked by opening the supercharging pressure relief valve 57, thereby smoothing the preliminary rotation.

In the single turbo mode, if the engine operation area is within the exhaust control valve small opening control mode area and the supercharging pressure control mode discrimination flag F2 is set (F2 = 1), the process proceeds to step S6. Then, the process proceeds to step S21, and it is determined whether or not the current operation region has shifted to outside the exhaust control valve small opening control mode region based on the condition determination in steps S21 to S23.

As shown in FIG. 8, in order to prevent the control hunting at the time of switching the supercharging pressure control mode, the setting of the set value N1 lower than the set values N2, P2 and TH2 is determined. (For example, 2600 rpm), P1 (for example, 1070 mmHg), TH1 (for example, 25 de)
g). Then, in step S21, the engine speed N is compared with the set value N1, in step S22, the intake pipe pressure (supercharging pressure) P is compared with the set value P1, and in step S23, the throttle opening TH and the set value TH1 are compared. In the case of N <N1, P <P1, or TH <TH1, it is determined that the current operation region has shifted out of the exhaust control valve small opening control mode region, and the routine proceeds to step S10 described above, where the supercharging is performed. The pressure control mode determination flag F2 is cleared. Thereby, the exhaust control valve small opening control is released. Also, N ≧ N1
If P ≧ P1 and TH ≧ TH1, it is determined that the current operation region remains within the region, and the process proceeds to step S11, where the supercharging pressure control mode determination flag F2 is held at the state of F2 = 1. Then, the exhaust control valve small opening control is continued.

As described above, in the single turbo mode, most of the exhaust gas from the engine body 1 is introduced into the primary turbocharger 40, and the compressor 40b is rotationally driven by the turbine 40a. So compressor 4
The compressed air is cooled by the intercooler 20, the flow rate is adjusted by the opening degree of the throttle valve 21, supplied to each cylinder through the chamber 22 and the intake manifold 23 with high charging efficiency, and supercharged. Works. In the single turbo mode in which only the primary turbocharger 40 operates in the single turbo mode, FIG.
As shown in the output characteristics, a torque curve TQ1 at the time of a single turbo with a high shaft torque in the low and middle rotation speed ranges is obtained.

Next, the single to twin switching control will be described.

In step S5, TP ≧ TP2, that is, the current operation range is the single-to-twin switching determination line L
If it is determined that the transition from the single turbo region to the twin turbo region (see FIG. 14) has taken place at the boundary of step 2, the step S
The control branches to 30 to execute single-to-twin switching control for switching from the single turbo state in which only the primary turbocharger 40 operates to the twin turbo state in which both turbochargers 40 and 50 operate.

Then, first, in step S30, the switching solenoid valve SOL. 1 is determined, and in step S32, the first exhaust control valve switching solenoid valve SOL. 3 is determined, and both switching solenoid valves SOL. When both 1 and 3 are ON,
Proceed directly to step S34. Further, each of the switching solenoid valves SOL. If 1, 3 is OFF, step S3
After turning ON in steps S1 and S33, the process proceeds to step S34.

Therefore, the supercharging pressure relief valve 57 is provided with a supercharging pressure relief valve switching solenoid valve SOL. By turning on 1 the positive pressure from the positive pressure passage 64a is introduced into the pressure chamber,
The valve is immediately closed by the positive pressure and the urging force of the spring. The exhaust control valve 53 includes a first exhaust control valve switching solenoid valve SOL. Actuator 5 by turning on 3
The valve opens when a positive pressure is introduced into the positive pressure chamber 54a.
In the case where the control mode is changed from the small-open exhaust control valve control mode under the single turbo mode to the single-to-twin switching control, the switching solenoid valve SOL.
When 1 is turned on, the supercharging pressure feedback control by the exhaust control valve 53 is stopped by exiting the routine through step S101 without performing the supercharging pressure feedback control in the exhaust control valve small opening control routine of FIG. ,
Exhaust control valve Duty solenoid valve for small opening control D.SOL.2
Is fully closed and the positive pressure through the positive pressure passage 64b is directly introduced into the positive pressure chamber 54a of the actuator 54 without leaking by the duty solenoid valve D.SOL.2. The degree is increased.

When the supercharging pressure relief valve 57 is closed, the relief passage 58 is shut off, and the exhaust control valve 53 is opened and its opening is increased, so that the rotational speed of the secondary turbocharger 50 is increased. At the same time, the supercharging pressure between the downstream 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 mode.

In step S34, the differential pressure search flag F3
If F3 = 0, the process proceeds to step S35, and if F3 = 1, the process jumps to step S39.

After shifting to the single-to-twin switching control, F3 = 0 when executing the first routine, so that step S3
5, first, the exhaust control valve opening delay time setting table is referenced with interpolation calculation based on the vehicle speed VSP, and the exhaust control valve 53 is fully opened (hereinafter referred to as “second exhaust control valve”). Switching solenoid valve SOL.4 to O
The exhaust control valve opening delay time T1 which determines the timing of turning on from the FF) is set. In step S36, the intake control valve opening delay time setting value table is referenced with interpolation calculation based on the vehicle speed VSP, and the exhaust control valve 53 is set. After the full opening control of the intake control valve 55, an intake control valve opening delay time T2 for setting a condition for starting the valve opening control of the intake control valve 55 (turning the intake control valve switching solenoid valve SOL.2 from OFF to ON) is set. Further, in step S37, the intake control valve 55 is determined based on the differential pressure (read value of the differential pressure sensor 80) DPS (= PU-PD) between the upstream pressure PU and the downstream pressure PD of the intake control valve 55.
Control valve opening differential pressure D for determining the valve opening control start timing
Set the PSST.

FIG. 9 is a conceptual diagram of the exhaust control valve opening delay time setting table, and FIG. 10 is a conceptual diagram of the intake control valve opening delay time setting table. As shown in the figure,
As the vehicle speed VSP increases, the exhaust control valve opening delay time T1 and the intake control valve opening delay time T2 are shortened, and the timing for fully opening the exhaust control valve 53 and the timing for opening the intake control valve 55, that is, switching to the twin turbo mode. The timing of the change is advanced, the acceleration response is made uniform regardless of the vehicle speed, and the drivability is improved.

FIG. 11 is a conceptual diagram of an 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. 14) at the boundary of the single-to-twin switching determination line L2 (single-to-twin switching determination value TP2). Is more negative, that is, the downstream pressure PD is higher than the upstream pressure PU of the intake control valve 55, and the higher the supercharged state, the more the intake control valve opening differential pressure DPSST is set to the negative side, and the intake control valve 55 is Advance the opening timing,
The acceleration response is improved.

The delay times T1, T2,
After setting the intake control valve opening differential pressure DPSST, the routine proceeds to step S38, in which the differential pressure search flag F3 is set, and the routine proceeds to step S39.

In step S39, the second solenoid valve SOL. 4 to determine whether the exhaust control valve 53 has already been fully opened. 4 = ON, and if the exhaust control valve fully open control has already been started, the routine jumps to step S49, where the second exhaust control valve switching solenoid valve SOL. 4 is kept ON, and SOL. When 4 = OFF, since the exhaust control valve fully open control has not been executed yet, the process proceeds to step S40, where the control valve switching time count value C1 is compared with the exhaust control valve open delay time T1, and a single →
After the transition to the twin switching control, the exhaust control valve opening delay time T1
Judge whether or not has elapsed.

If C1 ≧ T1, the process jumps to step S47 to jump to the second exhaust control valve switching solenoid valve SOL. 4 is turned ON, and the exhaust control valve 53 is fully opened. If the delay time before C1 <T1 has elapsed, the process proceeds to step S41, in which the engine load TP and the single to twin switching determination value TP2 set in step S4 are set.
Is compared with the value obtained by subtracting the set value WGS from TP, and TP <TP2
In the case of -WGS, the process returns to step S10, in which the single-to-twin switching control is stopped and the mode is immediately switched to the single turbo mode. This is to eliminate the uncomfortable feeling of driving by returning to the single turbo mode when the engine load TP decreases.

More specifically, as shown in FIG. 6, when the engine operating state once crosses the single-to-twin switching determination line L2 (TP2) from the single turbo region to the twin-turbo region side, the twin-to-single switching determination line is established. L1
(Twin → single switching judgment value TP1, details will be described later)
, The exhaust control valve 53 is fully opened after the delay time T1 has elapsed (Step S
47) Further, after the delay time T2 elapses, the differential pressure DPS
Reaches the intake control valve opening differential pressure DPSST, the intake control valve 5
5 opens (step S52), and switches to the twin turbo state. Therefore, once the signal exceeds the single-to-twin switch determination line L2, the twin-to-single switch determination line L1
If the operating state remains in the area surrounded by the single and twin switching determination line L2, the state is switched to the twin turbo state after the delay time has elapsed. However, in this region, as shown in FIG. 21, the shaft torque at the time of the twin turbo by the operation of the secondary turbocharger 50 is rather lower than the shaft torque at the time of the single turbo, and the state changes from the single turbo state to the twin turbo state. In other words, a sudden decrease in torque causes a torque shock and gives the driver an uncomfortable feeling.

In order to deal with this, the twin-to-single switching determination line L1 is changed to the single-to-twin switching determination line L1.
2 and the width (hysteresis) of both switching lines should be reduced, but if the width between both switching determination lines L1 and L2 is reduced, the frequency of switching between single turbo and twin turbo increases, and Since the negative pressure capacity of the surge tank 60 as a negative pressure source to be operated is insufficient, the surge tank 60
If the width is too narrow and the width is too narrow, the operation state becomes the single-twin switching determination line L2.
If it stays in the vicinity, there is an inconvenience that the supercharging pressure relief valve 57 without the setting of the switching delay time causes chattering due to the fluctuation of the engine load TP which is a parameter for turbo switching.

In order to prevent these, the operating condition is changed from single to
After crossing the twin switching determination line L2 to the twin turbo region side, and before the delay time T1 elapses, the interval from the single to twin switching determination line L2 is narrow and the set value WGS is subtracted to the single turbo region side in FIG. Single-twin switching determination stop line L3 (= TP2-WG)
When S) exceeds the single turbo range, the single-to-twin switching control for switching to the twin turbo state is stopped, the system is immediately shifted to the single turbo mode, and the single turbo state in which only the primary turbocharger 40 operates is maintained. This eliminates the operation in the region where the torque is low in the twin turbo state, and improves the drivability.

On the other hand, in step S41, TP ≧ TP2
In the case of -WGS, the process proceeds to step S42, and based on the engine speed N, the switching determination value table is referenced with interpolation calculation to set a primary turbo overspeed determination basic value EM2TP. This primary turbo overspeed determination basic value EM2
TP is used to determine whether the engine operating state has shifted to the primary turbo overspeed region under the single turbo state due to a sudden increase in the engine speed N and the engine load TP before the delay time T1 has elapsed after the shift from the single to the twin switching control. As shown in FIGS. 6 and 13, the primary turbocharger 40 reaches the critical speed under the single turbo condition from the relationship between the engine speed N at the standard atmospheric pressure and the engine load TP. A primary turbo overspeed determination line L4, which is a boundary of the primary turbo overspeed region (shown by oblique lines in FIG. 13), is determined in advance by an experiment or the like, and a ROM 102 corresponding to the primary turbo overspeed determination line L4 at the standard atmospheric pressure is determined in advance. Is stored as a switching determination value table using the engine speed N as a parameter at a series of addresses. I have. Note that the primary turbo overspeed determination line L4 is, of course,
The load is set higher than the twin switching determination line L2.

Next, at step S43, the atmospheric pressure ALT
Then, the judgment value atmospheric pressure correction coefficient KEM2 is set by referring to the judgment value atmospheric pressure correction coefficient table with interpolation calculation based on. FIG. 12 shows a conceptual diagram of the determination value atmospheric pressure correction coefficient table. As shown in the figure, the determination value atmospheric pressure correction coefficient KEM
2 is 1. when the pressure is equal to or higher than the standard atmospheric pressure (760 mmHg).
It is set to 0, and is set to a smaller value as the atmospheric pressure becomes lower.

In step S44, the primary turbo overspeed determination basic value EM2TP is corrected by a determination value atmospheric pressure correction coefficient KEM2 to set a primary turbo overspeed determination value EMV2TP. As a result, as the atmospheric pressure ALT decreases, the primary turbo overspeed determination value EMV
The primary turbo overspeed determination line L4 based on 2TP is
In the case of the standard atmospheric pressure indicated by the solid line in FIG. 14, similarly to the single-to-twin switching determination line L2, the load is corrected to a low load and a low rotation side as indicated by a dashed line, and the single-> constant change is always performed regardless of the atmospheric pressure change. The load is set higher than the twin switching determination line L2.

Next, in step S45, the engine load TP is compared with the primary turbo overspeed determination value EMV2TP, and if TP <EMV2TP, the process proceeds to step S4.
The program proceeds to 6, where the control valve switching time count value C1 is counted up and the routine exits. On the other hand, TP ≧ EMV2TP, and before the delay time T1 elapses, the engine operating region shifts to the primary turbo overspeed region due to the rapid increase of the engine speed N and the engine load TP (for example, corresponding to the case of sudden acceleration, racing, etc.). If it is determined that the second exhaust control valve switching solenoid valve SOL. 4 is immediately turned on and the exhaust control valve 5
3 is fully opened, and exhaust gas is also immediately supplied to the secondary turbocharger 50 side.

Therefore, the exhaust flow of the high exhaust pressure, which has risen due to the rapid increase of the engine load TP and the engine speed N, is immediately transmitted to the primary turbocharger 40 and the secondary turbocharger 5.
0 and are distributed approximately equally. As a result, the primary turbocharger 40 is in an overspeed state due to a rapid increase in the exhaust pressure and the exhaust flow rate, thereby preventing the occurrence of surging due to reaching the critical rotational speed, and reducing the heat load, thereby reliably preventing damage. Is done.

At this time, as described above, the atmospheric pressure AL
The engine operating region in which the primary turbocharger 40 is over-rotated as the T is lower is expanded to a low load and low rotation side. In order to determine the over-rotation of the primary turbocharger 40 in response to this, The primary turbo overspeed determination line L4 is corrected to the low load and low speed side as the atmospheric pressure ALT decreases, so that the primary turbo overspeed can be accurately determined even if the atmospheric pressure ALT changes, and It is possible to appropriately and reliably prevent overspeed of the primary turbocharger 40 irrespective of a change in atmospheric pressure and prevent damage.

Further, a primary turbo overspeed determination basic value EM2TP is set based on the engine speed N, and a primary turbo overspeed determination value EMV2TP obtained by correcting the atmospheric pressure with a determination value atmospheric pressure correction coefficient KEM2 and the engine load. Since the transition of the primary turbocharger 40 to the overspeed state is determined by comparing TP with the engine speed, the engine speed,
The determination can be made accurately over the entire range of the engine load and the atmospheric pressure, and the primary turbocharger 40 can be reliably prevented from being damaged.

After the shift from the single to the twin switching control, when the exhaust control valve opening delay time T1 has elapsed and the process proceeds from step S40 or from step S45 to step S47, the second exhaust control valve switching solenoid valve SOL. 4 is turned on, the exhaust control valve 53 is fully opened, the rotation speed of the secondary turbocharger 50 is further increased, and the compressor 5
The compressor pressure (supercharging pressure) by the secondary turbocharger 50 between the intake air control valve 55 and the intake control valve 55 also increases, and FIG.
As shown in the figure, the differential pressure D between the upstream and downstream of the intake control valve 55
PS rises.

Thereafter, the flow proceeds to step S48, in which the control valve switching time count value C1 is cleared in order to measure the time after the exhaust control valve is fully opened, and the flow proceeds to step S49.

When the process proceeds from step S39 or step S48 to step S49, the count value C1 representing the time after the exhaust control valve fully opening control (SOL.4 OFF → ON) is compared with the intake control valve opening delay time T2. ,
If C1 <T2, it is determined that the condition for opening the intake control valve 55 is not satisfied, and the count value C1 is determined in step S46.
Count up and exit the routine. Also, C1 ≧
In the case of T2, it is determined that the valve opening condition is satisfied, and step S5
0, the current differential pressure DPS and the intake control valve opening differential pressure DPS
ST is compared to determine whether the intake control valve 55 has reached the valve opening start timing.

When DPS <DPSST, it is determined that the valve opening start timing has not been reached, and the routine proceeds to step S51. When DPS ≧ DPSST, the upstream pressure PU and the downstream pressure PD of the intake control valve 55 are substantially equal to each other. The compressor 5 of the secondary turbocharger 50
0b and the intake pressure control valve 55, the boost pressure of the secondary turbocharger 50 increases and the primary turbocharger 4
0, it is determined that the intake control valve opening start timing has been reached, and the routine proceeds to step S52, where the intake control valve switching solenoid valve SOL. 2 is turned ON, and the intake control valve 55 is opened.

As a result, supercharging from the secondary turbocharger 50 is started, and a twin turbo state is established. Then, the process proceeds to step S53, and upon completion of the single-to-twin switching control, the twin-turbo mode discrimination flag F1 is set to shift to the twin-turbo mode next time, and the routine exits.

Also, in the above step S50, DPS <DP
If it is determined as SST and the process proceeds to step S51,
Further, the count value C1 is compared with a value obtained by adding a set value TDP to the intake control valve opening delay time T2, and C1 <T
If 2 + TDP, the process proceeds to step S46, where the count value C1 is counted up and the routine is exited, and C1 ≧ T
If 2 + TDP, the process proceeds to step S52, where the differential pressure DP
S does not reach the intake control valve opening differential pressure DPSST, even if the intake control valve switching solenoid valve SOL. 2 is turned ON, and 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 increase due to the failure of the differential pressure sensor 80 system, the intake control valve 55 is not opened any time after the exhaust control valve 53 is fully opened, and the secondary The supercharging pressure between the compressor 50b of the turbocharger 50 and the intake control valve 55 is abnormally increased, and the secondary turbocharger 50 is damaged due to surging. Therefore, after the exhaust control valve 53 is fully opened, even if the differential pressure DPS does not reach the intake control valve opening differential pressure DPSST, the intake control valve 55 is opened after the set time given by T2 + TDP has elapsed. Secondary turbocharger 5 due to failure of differential pressure sensor 80 system
This prevents zero damage.

The switching state from the single turbo mode to the twin turbo mode by the above single-to-twin switching control is shown in a time chart of FIG.

As described above, in the single-to-twin switching control, first, the supercharging pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and the preliminary rotation speed of the secondary turbocharger 50 is reduced. While increasing the preliminary rotation speed of the secondary turbocharger 50 by the exhaust control valve opening delay time T1.
After the lapse of the delay time T1, the exhaust control valve 53 is fully opened. And, the blower 5 of the secondary turbocharger 50
0b and the secondary turbocharger 50 between the intake control valve 55
, The differential pressure DPS rises, and after the exhaust control valve 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 the delay time T2 After the elapse, the intake control valve 55 is opened when the differential pressure DPS between the upstream and downstream of the intake control valve 55 reaches the intake control valve opening differential pressure DPSST. by this,
The switching from the single turbo state in which only the primary turbocharger 40 is operated to the twin turbo state by operating the two turbochargers 40 and 50 is performed smoothly, and the upstream pressure PU and the downstream pressure PD of the intake control valve are further reduced. Is substantially equal, the intake control valve 55 is opened to start supercharging from the secondary turbocharger 50. Therefore, the torque caused by a temporary decrease in the supercharging pressure generated when switching to the twin turbo state is performed. The generation of shock is effectively and reliably prevented.

After the shift from the single to the twin switching control, even if the set time (exhaust control valve opening delay time T1) has not been reached, the engine operation area is set to the primary turbo state in the single turbo state by TP ≧ EMV2TP (step S45). When it is determined that the operation has shifted to the turbo overspeed region, as shown by the broken line in FIG. 17, the second exhaust control valve switching solenoid valve SOL. 4 to ON to fully open the exhaust control valve 53 and disperse the exhaust gas to the secondary turbocharger 50 side, so that the primary turbocharger 40 is in an overspeed state due to a rapid increase in the exhaust pressure and the exhaust gas flow rate, and reaches the critical speed. Thus, damage to the primary turbocharger 40 due to the occurrence of surging is reliably prevented.

Further, in the primary turbo overspeed region, that is, when the engine is under the high-load and high-speed condition, the start timing of the fully opening of the exhaust control valve 53 is advanced, and accordingly, as shown by the broken line in FIG. The opening timing of the control valve 55 is also advanced, and the state is quickly switched to the twin turbo state. Therefore, as shown in the output characteristic diagram of FIG. 21, it is possible to quickly switch from the single turbo state to the twin turbo state in which the shaft torque is high in the region on the high rotation side bordering on the single-to-twin switching determination line L2. At the same time, good acceleration performance can be obtained by adapting to the driver's acceleration requirements.

Next, the twin turbo mode will be described.

When the twin-turbo mode discrimination flag F1 is set due to the end of the single-twin switching control, or when the twin-turbo mode was set at the time of executing the previous routine, the current routine is executed, and when F1 = 1, step S1 is executed.
The process branches from 1 to step S60.

Then, in step S60, a twin-to-single switching determination basic value TP1B is set by referring to the turbo switching determination value table with interpolation calculation based on the engine speed N (see FIG. 6), and the flow advances to step S61. Atmospheric ALT
The twin → single atmospheric pressure correction coefficient table KSGLALT is set by referring to the twin → single atmospheric pressure correction coefficient table with interpolation calculation based on the above. As shown in FIG. 15, in the twin-to-single atmospheric pressure correction coefficient table, similar to the aforementioned single-to-twin atmospheric pressure correction coefficient table, the standard atmospheric pressure is set to 1.0 or more, and as the atmospheric pressure ALT decreases. ,
The twin-to-single atmospheric pressure correction coefficient KSGLALT of a small value is stored.

Then, in step S62, the above twin →
The single-switching determination basic value TP1B is corrected by the twin-to-single atmospheric pressure correction coefficient KSGLALT, and a twin-to-single switching determination value TP1 for determining switching from the twin turbo mode to the single turbo mode is set.

The above twin → single atmospheric pressure correction coefficient KSG
Since LALT is set to a smaller value as the atmospheric pressure ALT decreases, the twin-to-single switching determination line L1 based on the twin-to-single switching determination value TP1 is the same as the standard atmospheric pressure shown by the solid line in FIG. Similarly to the single-to-twin switching determination line L2, the lower the atmospheric pressure ALT, the lower the load is, as shown by the one-dot chain line in FIG. As a result, a single to twin switching determination line L2 for determining switching from the single turbo state to the twin turbo state, and a twin to single switching determination line L1 for determining switching from the twin turbo state to the single turbo state. In addition, it is possible to always set a substantially constant appropriate hysteresis regardless of changes in the atmospheric pressure ALT,
It is possible to effectively and reliably prevent control hunting of switching the number of operating turbochargers, and furthermore, make the operation feeling accompanying switching from the twin turbo state to the single turbo state substantially the same regardless of changes in the atmospheric pressure ALT. it can.

Then, the process proceeds to a step S63, wherein the engine load TP is compared with the above-mentioned twin-single switching determination value TP1. If TP> TP1, the current operating region is in the twin-turbo region. Search flag F
4 is cleared, the single turbo region duration count value C2 for counting the single turbo region duration after shifting to the single turbo region is cleared in step S65, and then the process jumps to step S74, and jumps to step S74.
Or at step S77, the switching solenoid valve SOL. 1. Switching solenoid valve for intake control valve SO
L. 2. First and second exhaust control valve switching solenoid valves S
OL. 3 and 4 are turned on, respectively, and the boost pressure relief valve 5
7 is closed, the intake control valve 55 and the exhaust control valve 53 are both kept fully open, the twin turbo mode discrimination flag F1 is set in step S78, the process returns to step S19, and the control valve switching time count value C1 is cleared. Then, exit the routine.

In the twin turbo mode, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 5 are closed.
By fully opening 3, the secondary turbocharger 50 in addition to the primary turbocharger 40 is fully operated, and the turbochargers 40 and 50 are in a twin turbo state due to the supercharging operation. 50, the compressed air is supplied to the intake system, and as shown in the output characteristics of FIG.
Q2 is obtained.

On the other hand, at step S63, TP ≦ TP1,
That is, when it is determined that the current operation region has shifted to the single turbo region (see FIG. 14) at the boundary of the twin-single switching determination line L1, the process proceeds to step S66, and the value of the determination value search flag F4 is referred to. If F4 = 0, the process proceeds to step S67, and if F4 = 1, the process jumps to step S69.

The determination value search flag F4 is cleared in the twin turbo mode and when the engine operation state is in the twin turbo region with the engine load TP being on the boundary of the twin-to-single switching determination line L1 (TP1) (step). S
64). Therefore, after TP ≤ TP1, in the first routine execution, the process proceeds to step S67, in which the single turbo region continuation time determination value T is referenced by referring to the single turbo region continuation time determination value table with interpolation calculation based on the engine load TP.
Set 4. This determination value T4 is a reference value for switching to the single turbo mode in which only the primary turbocharger 40 operates after a predetermined time has elapsed after the engine operating state has shifted from the twin turbo region to the single turbo region.

FIG. 16 is a conceptual diagram of a single turbo area continuation time determination value table. The single turbo region continuation time determination value T4 set according to the engine load TP is:
For example, it is set to a maximum of 2.3 sec and a minimum of 0.6 sec, and is set to a smaller value as the value of the engine load TP is larger and higher. As a result, after the engine operation state shifts from the twin turbo region to the single turbo region, the time until switching from the twin turbo mode to the single turbo mode is shortened as the engine load increases.

Next, after setting the judgment value search flag F4 in step S68, the process proceeds to step S69.

Then, after counting up the single turbo region duration time count value C2 in step S69,
In step S70, the determination value T4 is compared with the count value C2. If C2 ≧ T4, the process proceeds to step S73, where the count value C2 is cleared, and the process returns to step S10.
Switch from twin turbo mode to single turbo mode. Thereby, each switching solenoid valve SOL. 1 to 4 are turned off, the supercharging pressure relief valve 57 is opened, and both the intake control valve 55 and the exhaust control valve 53 are closed, so that the primary and secondary turbochargers 40 and 50 are operated from the twin turbo state. The state is switched to the single turbo state in which only the turbocharger 40 operates.

The switching state at this time is shown by a time chart as shown by the solid line in FIG. As described above, the switching from the twin turbo mode to the single turbo mode is performed when the engine operation region shifts from the twin turbo region to the single turbo region (TP ≦ TP1) and the state continues for the set time (C2 ≧ T4). , And unnecessary switching of the supercharger due to a temporary decrease in the engine speed N associated with the shifting of the transmission is prevented.

Here, the single turbo region continuation time determination value T4 giving the set time is set to a shorter time as the value of the engine load TP is higher and the load is higher, and the switching to the single turbo state is accelerated. . That is, high torque is required during high engine load operation, but as shown in FIG. 21, the torque provided by the shaft torque curve TQ2 at the time of the twin turbo is on the single turbo region side of the twin → single switching determination line L1. (For example, point A in the figure)
The torque (point B in the figure) given by the shaft torque curve TQ1 at the time of single turbo is higher than that. If the twin turbo state is maintained in this region, sufficient shaft torque cannot be obtained, the output performance deteriorates, and Acceleration performance also deteriorates. For this reason, at the time of high engine load, the switching from the twin turbo state to the single turbo state is speeded up by setting the single turbo region duration time determination value T4 to a short value,
By quickly switching to a single-torque state with a high torque by minimizing operation in a low-torque region in a twin-turbo state (shifting from point A to point B in FIG. 21),
The output performance is improved, and the re-acceleration performance is also improved.

When the engine is running under a low load, the torque is in a low torque state, the torque difference between the twin turbo and the single turbo is small, and the set time is sufficiently given to switch from the twin turbo to the single turbo. Hardly causes torque fluctuation. For this reason, at a low load, after the engine operation region shifts from the twin turbo region to the single turbo region at the boundary of the twin-to-single switching determination line L1, the state is given by the single turbo region continuation time determination value T4, which is relatively long. By switching from the twin turbo state to the single turbo state after the continuation of the time, unnecessary switching of the turbocharger due to a temporary decrease in the engine speed N is effectively and reliably avoided.

On the other hand, in step S70, C2 <
In the case of T4, the process proceeds to step S71, where the throttle opening TH is compared with a set value TH3 (for example, 30 deg). If TH> TH3, the process returns to step S10 via the above step S73, and the engine operation region is set to the single turbo. After shifting to the region, even before the state continues for the set time, the mode is immediately switched to the single turbo mode, as shown by the broken line in FIG. 18, the supercharging pressure relief valve 57 is opened, and the exhaust control is performed. Both the valve 53 and the intake control valve 55 are closed to stop the supercharging operation of the secondary turbocharger 50, and only the primary turbocharger 40 is switched to the single turbo state of the supercharging operation.

The set value TH3 is for judging an acceleration request. That is, in the single turbo region (TP <TP1), as shown in the output characteristic of FIG. 21, the region is located on the low rotation side of the twin-to-single switching determination line L1 and is in the region where the shaft torque of the torque curve TQ2 at the time of the twin turbo is low. In this state, if the twin turbo mode is maintained in this state and the twin turbo state is maintained, sufficient acceleration performance cannot be obtained even when the accelerator pedal is depressed. Therefore, when it is determined that an acceleration request is required during operation in this region (TH> TH3), the operation mode is immediately shifted to the single turbo mode, the single turbo state is set, and the torque curve of the high shaft torque during the single turbo operation is set. By obtaining TQ1, the acceleration response is improved.

In step S71, TH ≦ TH3
In the case of, the process proceeds to step S72, where the vehicle speed VSP is compared with a set value VSP2 (for example, 2 km / h), and
> If it is determined in VSP2 that the vehicle is running, the process proceeds to step S74, where the twin turbo mode is maintained,
If it is determined that VSP ≦ VSP2 and the vehicle is stopped, the process returns to step S10 via step S73 in the same manner as described above, and immediately shifts to the single turbo mode.

The set value VSP2 is used to determine the stop state of the vehicle. If the accelerator is depressed and the engine is idling while the vehicle is stopped, for example, at idle speed, the engine load TP rises and the engine speed increases. The number N rises, the engine operation region shifts from the single turbo region to the twin turbo region, and becomes a twin turbo state,
After the accelerator is released, the engine load TP and the engine speed N immediately decrease, and the engine operating range is changed from the twin to single switching determination line L1 (FIG. 6 or FIG. 14).
When the transition to the single turbo region is again performed after the boundary of the single turbo region (see C2 ≧ T4), the mode is not switched to the single turbo mode unless the set time has elapsed after the transition to the single turbo region.
During this time, the engine speed N decreases and drops to near the idle speed (for example, near 700 rpm), and then each switching solenoid valve SOL. Switching from 1 to 4 is performed, and the supercharging pressure relief valve 57 and each of the control valves 53 and 55 are switched. At this time, the background noise due to the engine rotation is low because the engine speed N is low, and the sound generated when each valve is switched is heard by the driver, giving the driver discomfort. For this reason, when it is determined that the vehicle is stopped, (VSP ≦ V
SP2) After shifting to the single turbo range, even if the set time has not elapsed (C2 <T4), the valve is switched to the single turbo mode immediately before the engine speed decreases and the background noise decreases before the background noise decreases. Is completed, and the discomfort caused by the noise of the valve operation is eliminated. The switching state from the twin turbo mode to the single turbo mode at this time is shown by a dashed line in FIG.

While the embodiment of the present invention has been described above, the invention is not limited to this, and an engine load other than the basic fuel injection pulse width TP may be used.
Further, the present invention can be applied to engines other than the horizontally opposed engine.

[0125]

As described above , according to the present invention, it is possible to determine whether to switch from the single turbo state of the supercharging operation to the twin turbo state of the supercharging operation of both turbochargers only in the primary turbocharger. The single-to-twin switching determination line is corrected to the low rotation speed side as the atmospheric pressure decreases, the exhaust control valve fully open start time is advanced, and the exhaust flow introduced to the primary turbocharger is sent to the secondary turbocharger. Since the primary turbocharger is over-rotated due to being dispersed, the surging due to reaching the critical rotation speed is prevented even in high altitude traveling at low atmospheric pressure, damage is prevented, and reliability is improved. Further, since the switching from the single turbo state to the twin turbo state is accelerated with a decrease in the atmospheric pressure, the driving feeling due to the start of the operation of the secondary turbocharger can be made substantially the same regardless of the atmospheric pressure change.

Further, the engine operating area is
To switch from the turbo state to the twin turbo state
Single to twin switching judgment line for single turbo
After the transition from the area to the twin turbo area,
Before starting, set the primary turbo with the atmospheric pressure corrected.
When exceeding the overspeed judgment line to the twin turbo area side
Immediately, the exhaust control valve is fully opened and the primary turbo
Exhaust flow introduced to the turbocharger is transferred to the secondary turbocharger
Dispersed immediately, so from single turbo state to twin
When switching to turbo mode, regardless of changes in atmospheric pressure
The primary turbocharger suddenly increases exhaust pressure and exhaust flow
As a result of over-rotation due to ascent,
Heat generation and heat load are reduced.
As a result, damage is reliably prevented, and reliability is further improved.

[0127]

[Brief description of the drawings]

FIG. 1 is a flowchart showing a turbo switching control routine.

FIG. 2

FIG. 3

FIG. 4

FIG. 5 is a flowchart showing an exhaust control valve small opening control routine;

FIG. 6 is an explanatory diagram showing each switching determination value and a relationship between a single turbo region and a twin turbo region.

FIG. 7 is a conceptual diagram of a single to twin atmospheric pressure correction coefficient table.

FIG. 8 is an explanatory diagram of an exhaust control valve small opening control mode region;

FIG. 9 is a conceptual diagram of an exhaust control valve opening delay time setting table.

FIG. 10 is a conceptual diagram of an intake control valve opening delay time setting table.

FIG. 11 is a conceptual diagram of an intake control valve opening differential pressure setting table.

FIG. 12 is a conceptual diagram of a determination value atmospheric pressure correction coefficient table.

FIG. 13 is an explanatory diagram showing a relationship between each determination line and a primary turbo overspeed region.

FIG. 14 is an explanatory diagram showing an atmospheric pressure correction state of each determination line.

FIG. 15 is a conceptual diagram of a twin to single atmospheric pressure correction coefficient table.

FIG. 16 is a conceptual diagram of a single turbo region continuation time determination value table.

FIG. 17 is a time chart showing a switching state from a single turbo mode to a twin turbo mode.

FIG. 18 is a time chart showing a switching state from a twin turbo mode to a single turbo mode.

FIG. 19 is an overall configuration diagram of a supercharged engine.

FIG. 20 is a circuit diagram of a control device.

FIG. 21 is an explanatory diagram showing output characteristics during single turbo and twin turbo.

[Explanation of symbols]

 40 ... Primary turbocharger 50 ... Secondary turbocharger 53 ... Exhaust control valve 55 ... Intake control valve 100 ... Electronic control device (ECU) L1 ... Twin → single switching determination line L2 ... Single → twin switching determination line L4 ... Primary turbo overspeed judgment line TP1B: Basic value of twin-single switching judgment TP2B: Basic value of single-twin switching judgment EM2TP: Basic value of primary turbo overspeed judgment ALT: Atmospheric pressure KSGLALT: Twin-single atmospheric pressure correction coefficient KTWNALT: Single-> Twin atmospheric pressure correction coefficient KEM2: Judgment value Atmospheric pressure correction coefficient TP1: Twin to single switching judgment value TP2: Single to twin switching judgment value EMV2TP: Primary turbo overspeed judgment value T1: Exhaust control valve opening delay time (set time)

Claims (1)

(57) [Claims] A primary turbocharger (40) and a secondary turbocharger (50) are arranged in parallel in an intake and exhaust system of an engine, and a primary turbocharger (50) is connected to the secondary turbocharger (50). An intake control valve (55) and an exhaust control valve (53) are provided in the exhaust system, respectively.
5, 53) together to open both turbochargers (40,
50), the intake control valve (55) is closed and the exhaust control valve (5) is closed in the twin turbo region and the low speed region where the supercharging operation is performed.
3) The engine operation area is divided into a single turbo area in which only the primary turbocharger (40) is supercharged by closing or slightly opening the valve, and a single to twin switching determination set based on the engine operation area. Single to twin switching determination line (L2) set by value (TP2)
After the operation range shifts from the single turbo range to the twin turbo range at the boundary of the exhaust control valve (53), the exhaust control valve (53) is fully opened after a lapse of a set time (T1).
5) is opened, and only the primary turbocharger (40) is changed from the single turbo state of the supercharging operation to the two turbochargers (4).
0,50) In a control method of a supercharged engine that switches to a twin turbo state of a supercharging operation, a table in which a single to twin switching determination basic value (TP2B) at a standard atmospheric pressure is stored in advance based on an engine operating state. The single-to-twin switching determination basic value (TP2B) is set with reference to the pressure, and based on the atmospheric pressure (ALT), the smaller the atmospheric pressure (ALT), the smaller the single-to-twin atmospheric pressure correction coefficient (KTW).
Set NALT), and corrects the single → Twin switching determining a basic value of (TP2B) Single → Twin atmospheric pressure correction coefficient (KTWNALT), and sets the single → Twin switching threshold value (TP2), the engine operation Based on state, single turbo state and target
Overpressure of primary turbocharger (40) at sub-atmospheric pressure
Primary turbo overspeed judgment basics for judging rotation
Refer to the table in which the value (EM2TP) is stored in advance
Set the primary turbo overspeed judgment basic value (EM2TP).
If the atmospheric pressure (ALT) is lower based on the atmospheric pressure (ALT),
Set the smaller judgment value atmospheric pressure correction coefficient (KEM2)
And, the primary turbo overspeed determination basic value (EM2TP)
With the judgment value atmospheric pressure correction coefficient (KEM2)
Set the Maribo turbo overspeed judgment value (EMV2TP), and set the engine operation area before the set time (T1) elapses.
Range is the primary turbo overspeed determination value (EMV2T
P) Primary turbo overspeed judgment line (L4)
The exhaust control valve (5
A method for controlling an engine with a supercharger, characterized by fully opening 3) .