JPH0734889A - Control method of engine with supercharger - Google Patents

Abstract

PURPOSE:To prevent over-rotation of a primary turbo supercharger by correcting a single-twin switching judgement line for judging switching from a single turbo condition to a twin turbo condition in response to the atmospheric pressure. CONSTITUTION:A single-twin switching judgement basic value TP2B for an engine load TP in the standard atmospheric pressure is set based on engine rotational speed N (step S2), and a single twin atmospheric pressure corrective coefficient KTWNALT which is smaller as the atmospheric pressure is lower is set based on the atmospheric pressure ALT (step S3). A single-twin switching judgement basic value TP2B is corrected by the single-twin atmospheric pressure corrective coefficient, and the single twin switching judgement value TP2 is set (step S4). When it is judged that the engine load TP is larger than the single-twin switching judgement value TP2 (step S5), the target of control is transferred to switching of the single turbo condition to the twin turbo condition. Consequently, full opening starting timing of the exhaust control valve of a secondary turbo supercharger is quickened following a decrease in the atmospheric pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a primary turbocharger and a secondary turbocharger arranged in parallel in an intake / exhaust system of an engine and switches the number of turbochargers to be operated based on an operating state. The present invention relates to a control method for an engine with a feeder.

[0002]

2. Description of the Related Art In recent years, a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake / exhaust system of an engine, and an intake control valve is connected to an intake / 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 / closed to appropriately switch the operating number of the supercharger in accordance with the engine operating region.

In this supercharged engine, the engine operating area is divided into a low speed single turbo area and a high speed twin turbo area, and the intake control valve is closed when the operating area is in the single turbo area. When the operating range is in the twin turbo range, both controls are performed by closing the valve and simultaneously opening or closing the exhaust control valve (to pre-rotate the secondary turbocharger) to supercharge the primary turbocharger. By opening both valves, both turbochargers are supercharged to improve the output performance from the low speed range to the high speed range.

Further, as shown in FIG. 21, in the engine with a supercharger of this type, when viewed from the relationship between the shaft torque and the engine speed (however, the engine load is constant), only the primary turbocharger has a supercharger. In contrast to the torque curve TQ1 at the time of single turbo of the feed operation, the torque curve TQ2 at the time of twin turbo which supercharges both turbocharges becomes higher at a certain rotational speed N0 or more, and a high shaft torque can be obtained. In the region lower than the rotational speed N0, the axial torque during twin turbo is rather decreased due to the operation of the secondary turbocharger. Therefore, the point C where both torque curves in the figure coincide
Then, the single turbo state is switched to the twin turbo state.

However, since the rotational speeds at which the two torque curves match are different depending on the engine load, the points of coincidence between the two torque curves are found in advance by experiments or the like in correspondence with the engine load and the engine rotational speed, and as shown in FIG. → When the twin switching judgment line L2 is set, the exhaust control valve is opened small when the engine operating area shifts from the single turbo area on the low speed side to the twin turbo area on the high speed side with this single → twin switching judgment line L2 as a boundary. The secondary turbocharger to increase the rotation speed, open the exhaust control valve fully after the set time, increase the compressor pressure by the secondary turbocharger, and then open the intake control valve. Then, only the primary turbocharger switches from the single turbo state of supercharging operation to the twin turbo state of supercharging operation of both turbochargers. The torque fluctuation is prevented due to the decrease of the supercharging pressure at the time of switching from the single turbo state to the twin turbo state to prevent the occurrence of the torque shock (see, for example, Japanese Patent 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 operating turbochargers, conversely, switching from the twin turbo state to the single turbo state is performed with respect to the single-to-twin switching determination line L2. The twin-to-single switching judgment line L1 for judging is set to the low rotation side to provide hysteresis.

[0007]

By the way, when the supercharging pressure control is performed by the absolute pressure, the difference between the target supercharging pressure and the atmospheric pressure becomes large when the vehicle travels in high altitude where the atmospheric pressure is low. When trying to obtain the supercharging pressure, the rotational speed of the turbocharger becomes relatively high.In particular, in a high load state, only the primary turbocharger is supercharged from the single turbo state where both turbocharger supercharges When the operation is switched to the twin turbo state, the exhaust gas having a high exhaust flow rate is introduced only to the primary turbocharger until the exhaust control valve is fully opened, and the primary turbocharger is likely to be in the overspeed state.

However, in the above-mentioned prior art example, the timing of switching from the single turbo state to the twin turbo state is judged based on only the engine operating state such as the engine speed and the engine load, regardless of the atmospheric pressure fluctuation. ,
During high-altitude running where the atmospheric pressure is low, the primary turbocharger may be in the over-rotation state as described above, reaching the critical rotation speed, causing surging, and possibly being damaged. In addition, even if the engine is in the same operating condition, the rate of increase in the rotational speed of the turbocharger changes due to atmospheric pressure fluctuations. The driving feeling is different when the secondary turbocharger starts operating when turning.

The present invention has been made in view of the above circumstances, and a single-to-twin switching determination line for determining switching from the single-turbo state to the twin-turbo state is corrected in accordance with the atmospheric pressure to be in the twin-turbo state. With a supercharger that can correct the switching timing to prevent over-rotation of the primary turbocharger, and can make the driving feeling almost the same when the secondary turbocharger starts operating regardless of atmospheric pressure changes. A first object is to provide a method of controlling an engine.

Further, in addition to the above-mentioned first purpose, a single →
Even if the twin switching judgment line is corrected according to the atmospheric pressure, a substantially constant hysteresis can always be set between the twin-single switching judgment line for judging the switching from the twin turbo state to the single turbo state. A second object is to provide a method of controlling an engine with a supercharger, which is capable of effectively preventing control hunting for switching the turbocharger operating number.

Further, in addition to the first or second object, there is provided a control method for an engine with a supercharger, which can prevent over-rotation of a primary turbocharger more appropriately regardless of changes in atmospheric pressure. The third purpose is to provide.

[0012]

In order to achieve the above-mentioned first object, a first method of controlling an engine with a supercharger according to the present invention is a method in which a primary turbocharger and a secondary turbocharger are provided in an intake and an exhaust system of the engine. The turbocharger is arranged in parallel and the intake and exhaust systems connected to the secondary turbocharger are respectively provided with an intake control valve and an exhaust control valve. Single turbocharger that supercharges both turbochargers by closing the intake control valve and closing or slightly opening the exhaust control valve in the twin turbo range and low speed range. The engine operating region is divided into a turbo region, and the single operating region is set based on the engine operating region. After shifting from the region to the twin turbo region side, the exhaust control valve is fully opened after the set time elapses, and then the intake control valve is opened to only the primary turbocharger from the single turbo state of supercharging operation to both turbocharging Switch to the twin turbo mode of machine supercharge operation, and the engine operating area is the twin turbo area with the twin → single switching determination line set as a lower rotation side than the single → twin switching determination line according to the twin → single switching determination value. After shifting from the side to the single turbo region, both the exhaust control valve and the intake control valve are closed to change from the twin turbo state of both turbocharger supercharging operation to the single turbo state of only the primary turbocharger supercharging operation. In the control method of the supercharged engine that is switched, single → twin switching at standard atmospheric pressure is performed beforehand based on the engine operating state. Refer to the table that stores the judgment basic value, set the single → twin switching judgment basic value, and based on the atmospheric pressure, set the smaller single → twin atmospheric pressure correction coefficient as the atmospheric pressure becomes lower. It is characterized in that the twin switching judgment basic value is corrected by a single → twin atmospheric pressure correction coefficient to set the single → twin switching judgment value.

In order to achieve the above-mentioned second object, the second method for controlling an engine with a supercharger according to the present invention further has a twin-single switching determination basic value at standard atmospheric pressure based on the engine operating condition. Set the basic value for twin-> single switching judgment by referring to the stored table, and set the twin-> single atmospheric pressure correction coefficient that is smaller as the atmospheric pressure is lower based on the atmospheric pressure. The feature is that the value is corrected by the twin-> single atmospheric pressure correction coefficient to set the twin-> single switching determination value.

In order to achieve the above-mentioned third object, the third method for controlling an engine with a supercharger according to the present invention further includes a primary turbocharger in a single turbo state and at standard atmospheric pressure based on the engine operating state. Set the primary turbo overspeed judgment basic value by referring to the table in which the primary turbo overspeed judgment basic value for judging the overspeed of is stored, and based on the atmospheric pressure, the lower the atmospheric pressure is, the smaller the judgment is Value The atmospheric pressure correction coefficient is set, the primary turbo overspeed judgment basic value is corrected by the judgment value atmospheric pressure correction coefficient, and the primary turbo overspeed judgment value is set. When the primary turbo overspeed judgment line based on the above primary turbo overspeed judgment value exceeds the twin turbo region side, the exhaust control valve must be fully opened. The features.

[0015]

In the above first control method for the engine with the supercharger,
After the engine operating range shifts from the single turbo range to the twin turbo range with the single-to-twin switching judgment line as a boundary, the exhaust control valve is fully opened after the set time has elapsed, and then the intake control valve is opened to perform the primary turbo supercharging. Only the machine will change from a single turbo state of supercharging operation to a twin turbo of supercharging operation of both turbochargers. The above single-twin switching judgment line is set by the single-twin switching judgment value at the standard atmospheric pressure, which is set by the single-twin switching judgment value that is corrected by the single-twin atmospheric pressure correction coefficient, which is smaller as the atmospheric pressure is lower. The lower the atmospheric pressure, the lower the rotation speed side is corrected. As a result, the opening timing of the exhaust control valve is advanced, the exhaust flow introduced into the primary turbocharger is distributed to the secondary turbocharger, and the switching from single turbo state to twin turbo state is advanced. To be

In the second control method for the engine with a supercharger, the twin-to-single switching determination line for determining the switching from the twin turbo state to the single turbo state is further provided at the standard atmospheric pressure. The lower the atmospheric pressure is, the smaller the basic judgment value is. Twin → Single Twin corrected by the atmospheric pressure correction coefficient → Set by the single switching judgment value. Like the single → twin switching judgment line, the lower the atmospheric pressure, the lower the speed Is corrected to. As a result, even if the single-to-twin switching determination line is corrected by atmospheric pressure, a substantially constant hysteresis is always set between the twin-to-single switching determination line.

In the third method for controlling a supercharged engine, the engine operating region further includes a single-twin switching determination line for determining switching from the single turbo state to the twin turbo state from the single turbo region. After the transition to the twin turbo region, before the set time elapses, the primary turbo overspeed judgment basic value for determining the overspeed of the primary turbocharger in the single turbo state and standard atmospheric pressure is low. If the value exceeds the primary turbo overspeed judgment line by the primary turbo overspeed judgment value corrected by the atmospheric pressure correction coefficient to the twin turbo region side, the exhaust control valve will be fully opened immediately and the primary turbocharger will be released. The exhaust flow introduced into the is immediately distributed to the secondary turbocharger.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, referring to FIG. 19, an overall configuration of an engine with a supercharger 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 this embodiment), which is located in the left and right banks 3 and 4 of the crankcase 2, the combustion chamber 5, the intake port 6, the exhaust port 7, and the ignition. A plug 8, a valve mechanism 9 and the like are provided. The left bank 3 side is provided with # 2 and # 4 cylinders, and the right bank 4 side is provided with # 1 and # 3 cylinders. Also, due to this engine shortening shape, immediately after the left and right banks 3 and 4,
A primary turbo supercharger 40 and a secondary turbo supercharger 50 are provided respectively. As an exhaust system, a common exhaust pipe 10 from both left and right banks 3 and 4 is communicated with turbines 40a and 50a of both turbochargers 40 and 50, and an exhaust pipe 11 from turbines 40a and 50a is one exhaust pipe 12. To 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 the low and medium speed range, whereas the secondary turbocharger 50 has a large capacity having a large supercharging capacity in the medium-high speed range. It is a high-speed type. Therefore, the primary turbocharger 40 has a smaller capacity, so that the exhaust resistance becomes larger.

As an intake system, intake pipes 16 and 17 which are branched into two from the downstream of the air cleaner 15 are respectively communicated with the compressors 40b and 50b of the turbochargers 40 and 50, and the intake pipes from the compressors 40b and 50b. 1
8 and 19 are connected to the intercooler 20. The intercooler 20 communicates with a chamber 22 via a throttle body 27 having a throttle valve 21, and the chamber 22 communicates with an intake port 6 of each cylinder of the left and right banks 3 and 4 via an intake manifold 23. Further, as an idle control system, a check valve 26 that opens with an idle control valve (ISCV) and a negative pressure is provided in a bypass passage 24 that bypasses the throttle valve 21 and connects the intake pipe immediately downstream of the air cleaner 15 and the intake manifold 23. It is provided to control the intake air amount during idling or deceleration.

The intake manifold 2 is used as a fuel system.
A fuel tank 3 having an injector 30 disposed immediately upstream of the intake port 6 in each of the cylinders 3 and having a fuel pump 31.
A fuel passage 33 from 2 is provided with a filter 34 and a fuel pressure regulator 35 and communicates with the injector 30. The fuel pressure regulator 35 acts to adjust the intake pressure in the intake manifold, so that the fuel pressure supplied to the injector 30 is always kept at a constant height with respect to the intake pressure, and an electronic control unit to be described later is provided. It is possible to control the fuel injection amount by driving the injector 30 according to the pulse width of the injection signal from 100. Further, as an ignition system, an ignition coil 8 that is continuously provided for each spark plug 8 is provided.
It is connected so that the 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 the exhaust gas introduced to the turbine 40a to compress the compressor 4
0b is driven to rotate, sucks and pressurizes air, and operates so as to constantly supercharge. A primary wastegate valve 41 having a diaphragm actuator 42 is provided on the turbine 40a side. A control pressure passage 44 from directly downstream of the compressor 40b communicates with the pressure chamber of the actuator 42 with an orifice 48 so as to open the wastegate valve 41 with good response when the supercharging pressure rises above a set value. It Further, the control pressure passage 44 communicates the supercharging pressure with a duty solenoid valve D.SOL.1 that leaks to the upstream side of the compressor 40b, and a predetermined control pressure is generated by the duty solenoid valve D.SOL.1. Acts on the actuator 42 to change the opening of the waste gate valve 41 to control the supercharging pressure. Where the duty solenoid valve D.SO
L.1 operates by a duty signal from the electronic control unit 100 described later, and when the duty ratio of the duty signal is small, the opening degree of the waste gate valve 41 is increased by a high control pressure to reduce the supercharging pressure, As the ratio increases, the control pressure decreases due to the increase in the amount of leak, and the opening degree of the waste gate valve 41 is decreased 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, between the outlet side of the intercooler 20 near the throttle valve 21 downstream of the compressor 40b and the upstream side of the compressor 40b. The bypass passage 46 is communicated with. An air bypass valve 45 is provided in the bypass passage 46 so as to open the manifold negative pressure by introducing a manifold negative pressure through the passage 47 when the throttle valve is rapidly closed, and quickly leak the pressurized air contained downstream of the compressor 40b.

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

In the secondary turbocharger 50, similarly, the turbine 50a and the compressor 50b are rotationally driven by the exhaust gas to supercharge, and a secondary wastegate valve 51 having an actuator 52 is provided on the turbine 50a side. . Further, the exhaust pipe 10 upstream of the turbine 50a is provided with a downstream open exhaust control valve 53 having a diaphragm actuator 54, and the butterfly intake control having a similar actuator 56 is provided downstream of the compressor 50b. A valve 55 is provided, and a supercharging pressure relief valve 57 is provided in a relief passage 58 that communicates between the upper side and the lower side of the compressor 50b.

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

First, the surge tank 60, which is a negative pressure source, is connected to the intake manifold 23 through the passage 61 having the check valve 62.
The negative pressure is stored and the pulsating pressure is buffered when the throttle valve 21 is fully closed. Further, the switching solenoid valve SOL. For the supercharging pressure relief valve that opens and closes the supercharging pressure relief valve 57.
1. A switching solenoid valve SOL. For intake control valve that opens and closes the intake control valve 55. 2. First and second exhaust control valve switching solenoid valves SOL. Duty solenoid valve D.3, 4 which controls small opening of the exhaust control valve 53.
SOL.2 and secondary wastegate valve switching solenoid valve SO for opening and closing the secondary wastegate valve 51
L. Have W. Each switching solenoid valve SOL. W, SO
L. Reference numerals 1 to 4 denote negative pressure from the surge tank 60 via the negative pressure passage 63 by the ON and OFF signals from the electronic control unit 100, and a positive pressure passage 64 communicating with the downstream side of the intake control valve 55.
Positive pressure from a, 64b, atmospheric pressure, or the like is selected, and guided to the actuator side by the control pressure passages 70a to 74a, and the secondary waste gate valve 51, the boost pressure relief valve 57, and the control valves 55 and 53 are set. Operate. Further, the duty solenoid valve D.SOL.2 receives the duty signal from the electronic control unit 100, and the positive pressure chamber 54 of the actuator 54
The positive pressure acting on a is regulated to control the exhaust control valve 53 to a small opening.

The switching solenoid valve for the supercharging pressure relief valve SOL. 1 is a positive pressure passage 64a when the power supply is turned off.
Side is closed and the negative pressure passage 63 side is opened, and negative pressure is introduced through the control pressure passage 71a into the pressure chamber in which the spring of the supercharging pressure relief valve 57 is installed, thereby supercharging against the biasing force of the spring. The pressure relief valve 57 is opened. When turned on, the negative pressure passage 63 side is closed, the positive pressure passage 64a side is opened, and positive pressure is introduced into the pressure chamber of the supercharging pressure relief valve 57 to close the supercharging pressure relief valve 57.

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

Switching solenoid valve for secondary wastegate valve SOL. W is turned off only when it is determined by the electronic control unit 100 that high-octane gasoline is used based on the ignition advance amount and the like, and is turned on when it is determined that regular gasoline is used. Then, the switching solenoid valve SOL. When W is turned off, W is disposed in the actuator 52 by closing the passage 65 communicating with the upstream side of the intake control valve 55 and opening the atmospheric port to introduce atmospheric pressure into the actuator 52 via the control pressure passage 70a. The secondary waste gate valve 51 is closed by the biasing force of the spring. Further, when it is ON, the atmospheric port is closed and the passage 65 side is opened, and the supercharging pressure downstream of the secondary turbocharger 50 during operation of both turbochargers 40, 50 is guided to the actuator 52, and in response to this supercharging pressure. When the secondary waste gate valve 51 is opened, the boost pressure is relatively reduced when using regular gasoline as compared to when using high-octane gasoline.

Further, the first exhaust control valve switching solenoid valve SOL. 3 from the control pressure passage 73a is the exhaust control valve 53
The positive pressure chamber 54a of the actuator 54 that operates the
Exhaust control valve switching solenoid valve SOL. The control pressure passages 74a from 4 communicate with the negative pressure chambers 54b in which the springs of the actuator 54 are installed. And
Both switching solenoid valves SOL. When both 3 and 4 are off, the first exhaust control valve switching solenoid valve SOL. 3, the positive pressure passage 64b side is closed and the atmospheric port is opened, and the second exhaust control valve switching solenoid valve SOL. By closing the negative pressure passage 63 side and opening the atmosphere port, 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 biasing force of the spring installed in the negative pressure chamber 54b. . Further, both switching solenoid valves SOL. When both 3 and 4 are ON, the atmosphere port is closed and the first exhaust control valve switching solenoid valve SOL. 3 is a positive pressure passage 64b
Side, the second switching solenoid valve for exhaust control valve SO
L. By opening the negative pressure passage 63 side, 4 guides positive pressure to the positive pressure chamber 54a of the actuator 54 and negative pressure to the negative pressure chamber 54b, and fully opens the exhaust control valve 53 against the biasing force of the spring.

The first exhaust control valve switching solenoid valve SOL. Orifice 67 in control pressure passage 73a from 3
Is provided for the intake pipe 16 and the downstream side of the orifice 67.
A leak passage 66 is communicated with the leak passage 66, and the above-described duty solenoid valve D.
SOL.2 is provided. The first exhaust control valve switching solenoid valve SOL. When only 3 is ON and 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, the positive pressure is leaked by the duty solenoid valve D.SOL.2 and the exhaust control valve 53 Small open.
Here, when the duty ratio in the duty signal from the electronic control device 100 is large, the duty solenoid valve D.SOL.2 reduces the positive pressure acting on the positive pressure chamber 54a due to the increase in the leak amount, and the duty control of the exhaust control valve 53. As the opening degree is reduced and the duty ratio becomes smaller, the leak amount is reduced to keep the positive pressure high, and the opening degree of the exhaust control valve 53 is increased.
Then, when the engine operating region is in the predetermined exhaust control valve small opening control mode region 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 opened slightly.

Next, various sensors will be described.

A differential pressure sensor 80 is provided so as to detect a differential pressure upstream and downstream of the intake control valve 55, and an absolute pressure sensor 81 is controlled by a switching solenoid valve 76 to be larger than the intake pipe pressure (intake pressure in the intake manifold 23). Atmospheric pressure is selected and provided.

Further, a knock sensor 82 is attached to the engine body 1, and a water temperature sensor 83 is exposed in a cooling water passage communicating between the left and right banks 3 and 4 so that the exhaust pipe 10 has an O temperature.
2 The sensor 84 is exposed. Further, a throttle sensor 85 having a throttle valve 21 and a throttle opening sensor and an idle switch for detecting the throttle fully closed is built in.
And the intake air amount sensor 86 is arranged immediately downstream of the air cleaner 15.

A crank rotor 90 is rotatably mounted on a crank shaft 1a supported by the engine body 1, and a crank angle sensor 87 including an electromagnetic pickup is provided on the outer periphery of the crank rotor 90. further,
A cam rotor 91 connected to the cam shaft of the valve mechanism 9 is provided with a cam angle sensor 88 for cylinder discrimination, which is composed of an electromagnetic pickup or the like.

The crank angle sensor 87 and the cam angle sensor 88 detect the projections (or slits) formed at predetermined intervals on the crank rotor 90 and the cam rotor 91, respectively, during engine operation, and output the crank pulse and the cam pulse electronically. Output to the control device 100. Then, in the electronic control unit 100, the engine speed is calculated from the interval time of the crank pulse (protrusion detected), and
Ignition timing, fuel injection start timing, etc. are calculated, and cylinder discrimination is performed based on the input patterns 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 is C
The PU 101, the ROM 102, the RAM 103, the backup RAM 104, and the I / O interface 105 are mainly configured by a microcomputer connected via a bus line, and a constant voltage circuit 106 and a drive circuit 107 for supplying a predetermined stabilizing power supply to each unit are provided. It is incorporated.

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

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

Further, the I / O interface 105 is also provided.
Various sensors 80-88, vehicle speed sensor 8 to the input port of
9 and the battery 96 are connected. Also, I / O
An igniter 36 is connected to the output port of the interface 105, and further, an IS is connected via a drive circuit 107.
CV25, injector 30, each switching solenoid valve 7
6, SOL. W, SOL. 1-4, the duty solenoid valve D.SOL.1,2, and the relay coil of the fuel pump relay 98 are connected.

Then, the ignition switch 97 is turned on.
When turned on, the ECU relay 95 is turned on and the constant voltage circuit 1
A constant voltage is supplied to each unit via 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 through the I / O interface 105 based on the arithmetic program stored in the ROM 102, and stores the various signals in the RAM 103 and the backup RAM 104. Various control variables are calculated based on the data, the fixed data stored in the ROM, and the table value. Then, the drive circuit 107 turns on the fuel pump relay 98.
The fuel pump 31 is energized and driven, and the switching solenoid valves 76, SOL.
W, SOL. The ON / OFF signals are output to 1 to 4 and the duty signals to the duty solenoid valves D.SOL.1 and 2 to output the turbocharger operating number switching control and boost 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 operating number switching control by the ECU 100 will be described with reference to the flowcharts shown in the turbo switching control routines 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 ECU 100 is turned on by turning on the ignition switch 97, the system is initialized (clearing each flag and each count value), and first, at step S1, the twin turbo mode discrimination flag F1.
Refer to the value of. If the twin turbo mode discrimination flag F1 is cleared, the process proceeds to step S2,
If it is set, the process proceeds to step S60. The twin turbo mode determination flag F1 is cleared when the current control state is the single turbo mode in which only the primary turbocharger 40 is supercharged.
It is set in the twin turbo mode in which 50 is supercharged.

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.

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

In step S2, a single-to-twin switching determination basic value TP2B is set by referring to the turbo switching determination value table with interpolation calculation based on the engine speed N. This single-to-twin switching determination basic value TP2B is for determining the 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 is switched to the twin turbo mode based on the relationship between the engine speed N and the engine load (in this embodiment, the basic fuel injection pulse width) TP. → Twin switching judgment line L2 and vice versa Twin to switch from twin turbo mode to single turbo mode →
The single switching determination line L1 is obtained in advance 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
Corresponding to 1, a single-> twin switching determination basic value TP2B and a twin-> single switching determination basic value TP1B are stored in advance in a series of addresses in the ROM 102 as a table with the engine speed N as a parameter.

Here, in the single-to-twin switching determination line L2, 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. 21 coincide with each other in order to prevent torque fluctuation during switching. Point C
Therefore, as shown in FIG. 6, it is set to a low load side from a high load in the low and middle rotation speed range to an increase in the engine speed N. Further, as shown in the figure, in order to prevent control hunting at the time of switching the turbocharger operating number, the twin → single switching determination line L1 is
It is set to have a relatively wide hysteresis on the low speed side with respect to the single-to-twin switching determination line L2.

Next, in step S3, the single-twin atmospheric pressure correction coefficient KTWNALT (0 <KTWNALT≤0 is referred to based on the atmospheric pressure (absolute pressure value) ALT by referring to the single-twin atmospheric pressure correction coefficient table with interpolation calculation. 1.0) is set. As shown in FIG. 7, the standard atmospheric pressure (760 mmH
g) is set to 1.0, and a single-to-twin atmospheric pressure correction coefficient KTWNALT having a smaller value as the atmospheric pressure decreases is stored.

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

Next, in step S5, the single-to-twin switching determination value TP2 is compared with the current basic fuel injection pulse width TP (hereinafter "engine load"), and TP <T
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 the single → twin switching control for switching from the single turbo state to the twin turbo state.

The above single-to-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, the single-to-twin switching determination value TP2 causes only the primary turbocharger 40 to change from the single turbo state in which the supercharger is operating to the both turbochargers 4.
The single → twin switching determination line L2 for determining the switching to the twin turbo state of the 0,50 supercharging operation has a low load as indicated by the one-dot chain line in comparison with 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 operating region shifts from the single turbo region side to the twin turbo region side at the single-to-twin switching determination line L2 is advanced, and the transition from the single turbo mode to the single-to-twin switching control is made. It is hastened and the switching from the single turbo state to the twin turbo state is hastened.

When the supercharging pressure control is performed by the absolute pressure, the lower the atmospheric pressure ALT is, the higher the differential pressure between the target supercharging pressure and the atmospheric pressure becomes. When trying to obtain pressure, the rotational speed of the turbocharger becomes relatively high. As a result, the rate of increase in the number of revolutions of the primary turbocharger 40 also increases as the engine speed N representing the engine operating condition and the load TP increase. In the single turbo state in which only the primary turbocharger 40 is supercharged, most of the exhaust gas is discharged from the primary turbocharger 40.
Therefore, as the atmospheric pressure ALT becomes lower, the engine operating range in which the primary turbocharger 40 is in the over-rotation state is expanded to the low load and low rotation side. As described above, it becomes remarkable when the primary turbocharger 40 is a low-speed type small capacity. Therefore, the lower the atmospheric pressure ALT, the single turbo mode based on the engine operating state becomes single →
By advancing the timing of shifting to the twin switching control and advancing the full-open control timing of the exhaust control valve 53 described later, the exhaust flow introduced into the primary turbocharger 40 by the full opening of the exhaust control valve 53 is secondary turbocharger. The primary turbocharger 40 is prevented from excessive rotation by being dispersed in 50. Thereby, the primary turbocharger 40
Prevents the occurrence of surging due to the increase in exhaust pressure and exhaust flow rate and the occurrence of a critical rotation speed regardless of changes in atmospheric pressure ALT, and damage is prevented. Further, even in the same engine operating state, the rotational speed increase rate of the primary turbocharger 40 changes under a single turbo state due to atmospheric pressure variation, and the operation feeling due to the start of operation of the secondary turbocharger 50 changes.
The lower the atmospheric pressure ALT is, the earlier the switching to the twin turbo state is performed, so that the operation feeling associated with the start of operation of the secondary turbocharger 50 is made substantially the same regardless of the atmospheric pressure change (for example, highland traveling and lowland traveling). be able to.

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

At step S6, the value of the supercharging pressure control mode discrimination flag F2 is referred to. The supercharging pressure control mode determination flag F2 indicates that the current operating region is within 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 preliminarily rotated. Set when, and cleared when out of range.

Therefore, the ignition switch 97 is turned on.
Immediately after N, initial setting is performed, and when the operating region is outside the exhaust control valve small open control mode region during the execution of the previous routine, F2 = 0, so the process proceeds to step S7.
It is determined whether the current operating region has moved into the exhaust control valve small open control mode region by the condition determination in steps S7 to S9.

As shown in FIG. 8, the determination of the shift to the exhaust control valve small open control mode region is made based on the relationship between the engine speed N and the intake pipe pressure (supercharging pressure) P. On the lower rotation speed and lower load side, that is, in the single turbo mode, the set value N2 (for example, 265
0 rpm) and P2 (for example, 1120 mmHg), and the throttle opening TH is set value TH2.
When it is (for example, 30 deg) or more, it is determined to have moved into the area.

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

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

Then, in steps S17 to S19, the twin turbo mode determination flag F1, the differential pressure search flag F3, which will be described later, and the control valve switching time count value C1 are cleared, respectively, and then the routine exits.

Therefore, in the single turbo mode and in the low rotation and low load operation region outside the exhaust control valve small open control mode region, each switching solenoid valve SOL. All of 1 to 4 are turned off. Therefore, the boost pressure relief valve 57 is the switching solenoid valve for the boost pressure relief valve SOL. 1 is turned off, negative pressure from the surge tank 60 is introduced into the pressure chamber to open the valve against the biasing force of the spring, and the intake control valve 55 changes the intake control valve switching solenoid valve SOL. 2 O
A negative pressure is introduced into the pressure chamber of the actuator 56 by the FF, so that the valve is closed against the biasing force of the spring.
Further, the exhaust control valve 53 is a switching solenoid valve SOL. Actuator 54 when 3 and 4 are turned off
When the atmospheric pressure is introduced into both chambers 54a and 54b, the valve is closed by the biasing force of the spring.

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

In the single turbo mode and outside the exhaust control valve small open control mode region, or in the twin turbo mode described later, the boost pressure feedback control will not be described in detail here, but the primary waist will not be described. This is performed using only the gate valve 41. In this supercharging pressure control, the absolute supercharging pressure is used, the target supercharging pressure is set based on the engine operating state, and the intake pipe pressure detected by the absolute pressure sensor 81, that is, the actual supercharging pressure P is compared, Depending on the comparison result, the duty solenoid valve is controlled by PI control, for example.
The ON duty (duty ratio) for D.SOL.1 is calculated, and the duty signal of this ON duty is output to the duty solenoid valve D.SOL.1 to control the primary waste gate valve 41.

On the other hand, if it is determined in step S11 that the current operating region is within the exhaust control valve small open control mode region and the supercharging pressure control mode determination flag F2 is set, steps S12 to S14 are executed. Go 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. By turning on 3, the positive pressure chamber 5 of the actuator 54
Positive pressure is introduced into 4a, and the exhaust control valve 53 is opened.

In the exhaust control valve small open control mode, the exhaust control valve 53 is used by executing the exhaust control valve small open control routine shown in FIG. The supercharging pressure feedback control is performed, and the exhaust control valve 53 is slightly opened accordingly. 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 the exhaust control valve small open control mode is F2 = 1. , Switching solenoid valve for boost pressure relief valve SOL. Judging the energized state for 1,
SOL. When 1 = ON, the routine is exited and SOL.
When 1 = OFF, the process proceeds to step S102, the target supercharging pressure by the absolute pressure is compared with the actual supercharging pressure P detected by the absolute pressure sensor 81, and, for example, P is determined according to the comparison result.
Duty solenoid valve for exhaust control valve small opening control by I control ON duty for duty solenoid valve D.SOL.2 (duty ratio)
Is calculated, the duty signal of this ON duty is output to the duty solenoid valve D.SOL.2, and the boost pressure feedback control is executed. Therefore, the positive pressure chamber 54a of the actuator 54 is controlled by the duty solenoid valve D.SOL.2.
The positive pressure acting on is regulated, and as shown in FIG. 17, the exhaust control valve 53 is opened slightly, and the boost pressure feedback control is performed using only the exhaust control valve 53. Then, 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, the secondary turbocharger 50 is preliminarily rotated, and the transition to the twin turbo state is prepared.

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

If the engine operating region is in the exhaust control valve small open control mode region under the single turbo mode and the supercharging pressure control mode determination flag F2 is set (F2 = 1), the above step S6 is performed. Then, the process proceeds from step S21 to step S21, and it is determined whether the current operating region has moved to the outside of the exhaust control valve small open control mode region by the condition determination in steps S21 to S23.

In order to prevent the control hunting at the time of switching the boost pressure control mode, the determination of the shift to the outside of this area is performed as shown in FIG. (For example, 2600 rpm), P1 (for example, 1070 mmHg), TH1 (for example, 25 de)
g). Then, in step S21, the engine speed N and the set value N1 are compared, in step S22, the intake pipe pressure (supercharging pressure) P and the set value P1 are compared, and in step S23, the throttle opening TH and the set value TH1. If N <N1, or P <P1, or TH <TH1, the current operating region is judged to have moved out of the exhaust control valve small open control mode region, and the routine proceeds to step S10 described above to supercharge. The pressure control mode determination flag F2 is cleared. As a result, 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 is still within the region, and the process proceeds to step S11, and the supercharging pressure control mode determination flag F2 is held in the state of F2 = 1. , 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 turbine 40a rotationally drives the compressor 40b. So compressor 4
0b sucks and compresses the air, the compressed air is cooled by the intercooler 20, the flow rate is adjusted by the opening degree of the throttle valve 21, and is supplied to each cylinder through the chamber 22 and the intake manifold 23 with high charging efficiency and supercharging. To work. Then, in the single turbo state in which only the primary turbocharger 40 in the single turbo mode is operated,
As shown in the output characteristic of 1, the torque curve TQ1 at the time of the single turbo with high axial torque in the low and medium rotation speed range is obtained.

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

In step S5, TP ≥TP2, that is, the current operating region is the single-to-twin switching determination line L.
When it is determined that the single turbo region has shifted to the twin turbo region (see FIG. 14) at the boundary of step 2, step S
A branch to 30 is performed to execute single-to-twin switching control for switching from the single turbo state in which only the primary turbocharger 40 is operating to the twin turbo state in which both turbochargers 40 and 50 are operating.

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 the switching solenoid valves SOL. If both 1 and 3 are ON,
The process directly proceeds to step S34. Further, each of the switching solenoid valves SOL. If 1 and 3 are OFF, step S3
After being turned on in 1 and S33, the process proceeds to step S34.

Therefore, the supercharging pressure relief valve 57 is connected to the supercharging pressure relief valve switching solenoid valve SOL. When 1 is turned on, the positive pressure from the positive pressure passage 64a is introduced into the pressure chamber,
The valve is immediately closed by this positive pressure and the biasing force of the spring. Further, the exhaust control valve 53 includes a first exhaust control valve switching solenoid valve SOL. Actuator 5 when 3 is turned on
The positive pressure is introduced into the positive pressure chamber 54a of No. 4 to open the valve.
When the exhaust control valve small open control mode under the single turbo mode is switched to the single → twin switching control, the boost pressure relief valve switching solenoid valve SOL.
In the exhaust control valve small opening control routine of FIG. 5, turning on 1 causes the routine to exit the routine through step S101 without performing the boost pressure feedback control, so that the boost pressure feedback control by the exhaust control valve 53 is stopped. ,
Exhaust control valve Small open control duty solenoid valve 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 being leaked by the duty solenoid valve D.SOL.2, so that the exhaust control valve 53 is opened. The degree is increased.

The relief passage 58 is closed by closing the supercharging pressure relief valve 57, and the rotation speed of the secondary turbocharger 50 is increased by opening the exhaust control valve 53 and increasing its opening. At the same time, the supercharging pressure between the downstream side of the compressor 50b of the secondary turbocharger 50 and the intake control valve 55 is gradually increased to prepare for the transition to the twin turbo 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 at the first routine execution, so step S3
5, first, referring to the exhaust control valve open delay time setting table with interpolation calculation based on the vehicle speed VSP, fully open control of the exhaust control valve 53 after the transition from single to twin switching control (for the second exhaust control valve) Switch solenoid valve SOL.4 to O
The exhaust control valve opening delay time T1 that determines the timing (from FF to ON) is set, and the intake control valve opening delay time set value table is referred to with interpolation calculation based on the vehicle speed VSP in step S36, and the exhaust control valve 53 The intake control valve opening delay time T2 for setting the 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) after the full open control is set. Further, in step S37, the intake control valve 55 is based on the differential pressure between the upstream pressure PU and the downstream pressure PD of the intake control valve 55 (read value of the differential pressure sensor 80) DPS (= PU-PD).
Intake valve opening differential pressure D for determining the valve opening control start timing of
Set PSST.

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

FIG. 11 shows a conceptual diagram of the intake control valve opening differential pressure setting table. As shown in the figure, the differential pressure DPS immediately after the engine operating state shifts from the single turbo region to the twin turbo region (see FIG. 14) with the single → twin switching determination line L2 (single → twin switching determination value TP2) as a boundary. Is closer to the negative side, that is, the downstream pressure PD is higher than the upstream pressure PU of the intake control valve 55, and the higher the supercharging state is, the intake control valve opening differential pressure DPSST is set to the negative side, and the intake control valve 55 is controlled. Advance the opening timing,
The acceleration response is improved.

Then, these delay times T1, T2,
After setting the intake control valve opening differential pressure DPSST, the process proceeds to step S38, the differential pressure search flag F3 is set, and the process proceeds to step S39.

In step S39, the second exhaust control valve switching solenoid valve SOL. No. 4, the exhaust control valve 53 has already started to be fully opened, and the SOL. 4 = ON, and if the exhaust control valve fully open control has already been started, the process jumps to step S49 and the second exhaust control valve switching solenoid valve SOL. 4 is kept ON, and SOL. If 4 = OFF, it means that the exhaust control valve full-open control has not been executed yet, so the routine 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 single →
Exhaust control valve open delay time T1 after switching to twin switching control
To determine if has passed.

If C1 ≧ T1, the process jumps to step S47 and the second exhaust control valve switching solenoid valve SOL. 4 is turned on and the exhaust control valve 53 is fully opened. When the delay time C1 <T1 has not yet elapsed, the routine proceeds to step S41, where the engine load TP and the single-to-twin switching determination value TP2 set in step S4 are set.
Compared with the value obtained by subtracting the set value WGS from, TP <TP2
In the case of -WGS, the process returns to step S10 to stop the single-to-twin switching control and immediately switch to the single turbo mode. This is because when the engine load TP drops, the mode returns to the single turbo mode, so that the driver does not feel uncomfortable.

More specifically, as shown in FIG. 6, once the engine operating state exceeds the single → twin switching determination line L2 (TP2) from the single turbo region to the twin turbo region side, the twin → single switching determination line is reached. L1
(Twin → single switching judgment value TP1, details will be described later)
The exhaust control valve 53 is fully opened after the lapse of the delay time T1 (step S
47), and after the delay time T2 has elapsed, the differential pressure DPS
Reaches the intake control valve opening differential pressure DPSST, the intake control valve 5
5 opens (step S52), and the twin turbo state is switched to. Therefore, once the single-to-twin switching determination line L2 is exceeded, the twin-to-single switching determination line L1
If the operating state remains in the area surrounded by the single-to-twin switching determination line L2, it will switch to the twin-turbo state after the delay time has elapsed. However, in this region, as shown in FIG. 21, the axial torque during twin turbo due to the operation of the secondary turbocharger 50 is rather lower than the axial torque during single turbo, and the single turbo state is switched to the twin turbo state. In other words, the torque is suddenly reduced to cause a torque shock, and the driver feels uncomfortable.

In order to deal with this, the twin → single switching determination line L1 is changed to the single → twin switching determination line L.
It is sufficient to narrow the width (hysteresis) of both switching lines closer to 2, but if the width between both switching judgment lines L1 and L2 is narrowed, the switching frequency between single turbo and twin turbo increases and each control valve is turned on. Since the negative pressure capacity of the surge tank 60 as a negative pressure source to operate is insufficient, the surge tank 60
Must be made a large capacity, and if the width is too narrow, the operating condition is single → twin switching judgment line L2.
If it stays in the vicinity, there is an inconvenience that the turbocharging pressure relief valve 57, which has no setting of the switching delay time, causes chattering due to the fluctuation of the engine load TP which is a parameter of the turbo switching.

In order to prevent these, the operating condition is single →
After the twin switching determination line L2 is crossed to the twin turbo region side and before the delay time T1 elapses, the single-to-twin switching determination line L2 has a narrower interval and the set value WGS is subtracted to the single turbo region side, which is a broken line in FIG. Single-to-twin switching determination stop line L3 (= TP2-WG
When S) is exceeded to the single turbo region side, the single → twin switching control for switching to the twin turbo state is stopped and the single turbo mode is immediately shifted to maintain the single turbo state in which only the primary turbocharger 40 operates. As a result, driving in a twin-turbo state in a low torque region is eliminated to improve drivability.

On the other hand, in step S41, TP ≧ TP2
In the case of -WGS, the process proceeds to step S42, and the primary turbo overspeed determination basic value EM2TP is set by referring to the switching determination value table with interpolation calculation based on the engine speed N. This primary turbo overspeed determination basic value EM2
TP determines whether the engine operating state has shifted to the primary turbo overspeed region under the single turbo state due to a rapid increase in engine speed N and engine load TP before the delay time T1 has elapsed after the transition from single to twin switching control. 6 and FIG. 13, the primary turbocharger 40 reaches the critical speed under the single turbo condition from the relationship between the engine speed N and the engine load TP at the standard atmospheric pressure, as shown in FIGS. 6 and 13. A primary turbo overspeed determination line L4, which is a boundary of the primary turbo overspeed region (shown by diagonal lines in FIG. 13), is previously obtained by an experiment or the like, and corresponding to the primary turbo overspeed determination line L4 at the standard atmospheric pressure, the ROM 102 is set in advance. Are stored in a series of addresses as a switching judgment value table using the engine speed N as a parameter. There is. Of course, the primary turbo overspeed determination line L4 is
It is set on the higher load side than the twin switching judgment line L2.

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

Then, in step S44, the primary turbo overspeed determination basic value EM2TP is corrected by the determination value atmospheric pressure correction coefficient KEM2 to set the primary turbo overspeed determination value EMV2TP. As a result, as the atmospheric pressure ALT becomes lower, the primary turbo overspeed determination value EMV
2TP primary turbo overspeed judgment line L4
In the case of the standard atmospheric pressure shown by the solid line in FIG. 14, as in the single-to-twin switching determination line L2, the load is corrected to the low load and low rotation side as indicated by the alternate long and short dash line, and it is always single → regardless of the atmospheric pressure change. It is set on the higher load side than the twin switching judgment line L2.

Next, in step S45, the engine load TP is compared with the primary turbo overspeed determination value EMV2TP, and if TP <EMV2TP, step S4
6, the control valve switching time count value C1 is incremented and the routine is exited. On the other hand, TP ≥ EMV2TP, and before the delay time T1 elapses, the engine operating range shifts to the primary turbo overspeed range due to the rapid increase in the engine speed N and the engine load TP (e.g., in case of sudden acceleration, racing, etc. If it is determined that the second exhaust control valve switching solenoid valve SOL. 4 is turned on immediately and the exhaust control valve 5
3 is fully opened, and exhaust gas is immediately supplied to the secondary turbocharger 50 side.

Therefore, the exhaust flow having a high exhaust pressure increased by the rapid increase in the engine load TP and the engine speed N immediately causes the primary turbocharger 40 and the secondary turbocharger 5 to discharge.
It is introduced by being distributed almost equally to 0. As a result, the primary turbocharger 40 is prevented from generating surging due to a rapid increase in exhaust pressure and exhaust flow rate and reaching a critical rotation speed, and the heat load is reduced, and damage is reliably prevented. To be done.

At this time, as described above, the atmospheric pressure AL
The lower T is, the wider the engine operating range in which the primary turbocharger 40 is in the overspeed state is expanded to the low load side and the low speed side. In response to this, the overspeed of the primary turbocharger 40 is determined. The primary turbo overspeed determination line L4 is corrected to a 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. It is possible to prevent over-rotation of the primary turbocharger 40 and prevent damage properly and reliably regardless of changes in atmospheric pressure.

Further, a primary turbo overspeed judgment basic value EM2TP is set on the basis of the engine speed N, and the primary turbo overspeed judgment value EMV2TP and the engine load obtained by correcting the atmospheric pressure by the judgment value atmospheric pressure correction coefficient KEM2 are set. Since the transition to the overspeed state of the primary turbocharger 40 is judged by comparing with TP, the engine speed,
Accurate determination can be made over the entire range of engine load and atmospheric pressure, and damage to the primary turbocharger 40 can be reliably prevented.

When the exhaust control valve opening delay time T1 elapses after the shift to the single-to-twin switching control 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
0b and the intake control valve 55, the compressor pressure (supercharging pressure) by the secondary turbocharger 50 also rises, as shown in FIG.
As shown in, the differential pressure D between the upstream and downstream of the intake control valve 55
PS increases.

After that, the routine proceeds to step S48, where the control valve switching time count value C1 is cleared to measure the time after the exhaust control valve fully open control, and the routine proceeds to step S49.

Then, proceeding from step S39 or step S48 to step S49, the count value C1 representing the time after the exhaust control valve full-open control (SOL.4 OFF → ON) is compared with the intake control valve open delay time T2. ,
If C1 <T2, it is determined that the intake control valve 55 valve opening condition 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 is performed.
0, the current differential pressure DPS and the intake control valve opening differential pressure DPS
By comparing with ST, it is determined whether the opening timing of the intake control valve 55 has been reached.

When DPS <DPSST, it is judged 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. Equal, that is, the compressor 5 of the secondary turbocharger 50
0b and the intake control valve 55, the supercharging pressure by the secondary turbocharger 50 increases and the primary turbocharger 4
0 becomes substantially equal to the supercharging pressure and it is judged that the intake control valve opening start timing has been reached, and the routine proceeds to step S52, and 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 the twin turbo state is established. Then, the process proceeds to step S53, and when the single-to-twin switching control is completed, the twin turbo mode determination flag F1 is set next time to shift to the twin turbo mode, and the routine is exited.

In step S50, DPS <DP
When it is judged as SST and the process proceeds to step S51,
Further, the count value C1 is compared with a value obtained by adding the set value TDP to the intake control valve opening delay time T2, and C1 <T
When 2 + TDP, the process proceeds to step S46, the count value C1 is incremented, the routine is exited, and C1 ≧ T
When 2 + TDP, the process proceeds to step S52, and the differential pressure DP
Even if S has not reached the intake control valve opening differential pressure DPSST, 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 at any time after the exhaust control valve 53 is fully opened, and the secondary control is performed. The supercharging pressure between the compressor 50b of the turbocharger 50 and the intake control valve 55 rises abnormally, and the secondary turbocharger 50 is damaged due to surging. Therefore, even after the differential pressure DPS has not reached the intake control valve opening differential pressure DPSST after the exhaust control valve 53 is fully opened, 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
The damage of 0 is prevented in advance.

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

As described above, in the single-to-twin switching control, first, the boost pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and the preliminary rotation speed of the secondary turbocharger 50 is adjusted. The exhaust control valve opening delay time T1 gives the time required for increasing the preliminary rotation speed of the secondary turbocharger 50 while increasing the speed.
After the lapse of this delay time T1, the exhaust control valve 53 is fully opened. And the blower 5 of the secondary turbocharger 50
0b and the intake control valve 55 between the secondary turbocharger 50
As a result, the supercharging pressure rises and the differential pressure DPS rises, and after the exhaust control valve fully open control, the intake control valve open delay time T2 compensates for the operation delay time until the exhaust control valve 53 is fully opened. After a lapse of time, the intake control valve 55 is opened when the differential pressure DPS between the upstream side and the downstream side 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 operating to the twin turbo state in which both turbochargers 40 and 50 are operating is performed smoothly, and further, the upstream pressure PU and the downstream pressure PD of the intake control valve are increased. Since the intake control valve 55 is opened to start supercharging from the secondary turbocharger 50 when the values become substantially equal to each other, the torque due to the temporary decrease in the supercharging pressure generated when switching to the twin turbo state is performed. Shock is effectively and reliably prevented.

Even if the set time (exhaust control valve opening delay time T1) is not reached after shifting to the single-to-twin switching control, TP ≥ EMV2TP (step S45), and the engine operating region is in the primary turbo state under the single turbo condition. When it is determined that the turbo overspeed range has been entered, the second exhaust control valve switching solenoid valve SOL. 4 is turned 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 over-rotation state due to a rapid increase in exhaust pressure and exhaust flow rate, and the critical speed is reached. The damage to the primary turbocharger 40 due to the occurrence of surging will be reliably prevented.

Further, in the primary turbo overspeed region, that is, in the engine high load and high rotation state, the full-open start timing of the exhaust control valve 53 is advanced, and in response to this, as shown by the broken line in FIG. The valve opening start timing of the control valve 55 is also advanced, and the twin turbo state is quickly switched. Therefore, as shown in the output characteristic diagram of FIG. 21, it is possible to early switch from the single turbo state to the twin turbo state in which the axial torque is high in the high rotation side region with the single to twin switching determination line L2 as a boundary. At the same time, good acceleration performance can be obtained by adapting to the driver's acceleration request.

Next, the twin turbo mode will be described.

When the twin turbo mode discrimination flag F1 is set by the end of the single-to-twin switching control, or when the twin turbo mode was set at the time of the previous routine execution, at the time of the current routine execution, the step S is performed by F1 = 1.
The process branches from 1 to step S60.

Then, in step S60, the 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 process proceeds to step S61. Atmospheric pressure ALT
Based on, refer to the twin-> single atmospheric pressure correction coefficient table with interpolation calculation and set the twin-> single atmospheric pressure correction coefficient KSGLALT. As shown in FIG. 15, in the twin-to-single atmospheric pressure correction coefficient table, the standard atmospheric pressure or higher is set to 1.0 and the atmospheric pressure ALT decreases as in the above-described single-to-twin atmospheric pressure correction coefficient table. ,
A small value of twin → single atmospheric pressure correction coefficient KSGLALT is stored.

Then, in step S62, the twin
The single switching judgment basic value TP1B is corrected by the twin → single atmospheric pressure correction coefficient KSGLALT to set the twin → single switching judgment value TP1 for judging the switching from the twin turbo mode to the single turbo mode.

Twin-to-single atmospheric pressure correction coefficient KSG
Since LALT is set to a smaller value as the atmospheric pressure ALT decreases, the twin → single switching determination line L1 according to the twin → single switching determination value TP1 is the standard atmospheric pressure shown by the solid line in FIG. Similar to the single-to-twin switching determination line L2, the lower the atmospheric pressure ALT, the more the load is corrected to the low-rotation side as shown by the dashed line in the figure. As a result, a single → twin switching determination line L2 for determining the switching from the single turbo state to the twin turbo state, and a twin → single switching determination line L1 for determining the switching from the twin turbo state to the single turbo state. In addition, it is possible to set a proper hysteresis that is almost constant regardless of the change in atmospheric pressure ALT.
Control hunting for switching the turbocharger operating number can be effectively and surely prevented, and further, the operation feeling associated with the switching from the twin turbo state to the single turbo state can be made substantially the same regardless of the change in the atmospheric pressure ALT. it can.

Next, in step S63, the engine load TP is compared with the twin-to-single switching determination value TP1. If TP> TP1, the current operating region is in the twin turbo region, so the determination value is determined in step S64. Search flag F
4 is cleared, and in step S65, the single turbo region continuation time count value C2 for counting the single turbo region continuation time after the transition to the single turbo region is cleared, and then the process jumps to step S74 and step S74.
Through step S77, the switching solenoid valve SOL. 1, intake control valve switching solenoid valve SO
L. 2, switching solenoid valve S for the first and second exhaust control valves
OL. Turn on 3 and 4 respectively, and boost pressure relief valve 5
7 is closed and both the intake control valve 55 and the exhaust control valve 53 are fully opened, the twin turbo mode determination flag F1 is set in step S78, the process returns to step S19, and the control valve switching time count value C1 is cleared. After that, exit the routine.

In this 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 turbocharger 40, 50 is in a twin turbo state due to the supercharging operation. Compressed air by supercharging of 50 is supplied to the intake system, and as shown in the output characteristic of FIG. 21, a torque curve T at the time of twin turbo with high axial torque in a high rotation speed range.
Q2 is obtained.

On the other hand, in 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) with the twin-to-single switching determination line L1 as a boundary, 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 judgment value search flag F4 is cleared in the twin turbo mode and when the engine load TP is within the twin turbo region when the engine operating condition is within the twin → single switching judgment line L1 (TP1). S
64). Therefore, after TP ≤TP1, when executing the routine for the first time, the process proceeds to step S67, and the single turbo region continuation time determination value T is referred to by referring to the single turbo region continuation time determination value table based on the engine load TP with interpolation calculation.
Set 4. The determination value T4 is a reference value for switching to the single turbo mode in which only the primary turbocharger 40 operates after a lapse of a predetermined time after the engine operating state shifts from the twin turbo region to the single turbo region.

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

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

Then, in step S69, after counting up the single turbo region continuation time count value C2,
In step S70, the judgment value T4 is compared with the count value C2. If C2 ≧ T4, the process proceeds to step S73, the count value C2 is cleared, and then the process returns to step S10.
Switch from twin turbo mode to single turbo mode. As a result, 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. Only the turbocharger 40 is switched to the single turbo state in which it is operating.

The switching state at this time is shown by a solid line in FIG. In this way, when switching from the twin-turbo mode to the single-turbo mode, after the engine operating range is changed from the twin-turbo range to the single-turbo range (TP ≦ TP1), the state continues for a set time (C2 ≧ T4). Therefore, unnecessary switching of the supercharger due to a temporary decrease in the engine speed N due to gear shifting of the transmission is prevented.

Here, the single turbo region continuation time determination value T4 that gives the set time is set to a shorter time as 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 engine high load operation, but as shown in FIG. 21, the single turbo region side with the twin-to-single switching determination line L1 as a boundary, the torque given by the axial torque curve TQ2 during twin turbo is provided. (For example, point A in the figure)
The torque (point B in the figure) given by the axial torque curve TQ1 during single turbo is higher than that, and if the twin turbo state is maintained in this region, sufficient axial torque cannot be obtained and output performance deteriorates. Acceleration performance also deteriorates. For this reason, when the engine load is high, the single turbo region continuation time determination value T4 is set to a short value, which speeds up the switching from the twin turbo state to the single turbo state.
By quickly switching to the single-turbo state with high torque (removing from point A to point B in FIG. 21) by minimizing the operation in the low-torque region in the twin-turbo state,
The output performance is improved and the reacceleration performance is also improved.

Further, the low-torque operation is in a low-torque state, and the difference in torque between twin turbo and single turbo is small, and the twin turbo state is switched to the single turbo state by giving the set time sufficiently. Produces almost no torque fluctuation. For this reason, when the load is low, the engine operating region shifts from the twin turbo region side to the single turbo region with the twin-to-single switching determination line L1 as a boundary, and then the state is relatively long given by the single turbo region continuation time determination value T4. By switching from the twin-turbo state to the single-turbo state after continuing for a period of time, unnecessary switching of the supercharger 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, the throttle opening TH is compared with the set value TH3 (for example, 30 deg), and in the case of TH> TH3, the process returns to step S10 via the above step S73, and the engine operating region is the single turbo. Even after the transition to the region, even before the state continues for the set time, as shown by the broken line in FIG. 18, the mode is immediately switched to the single turbo mode, the boost 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 the acceleration request. That is, in the single turbo region (TP <TP1), as shown in the output characteristic of FIG. 21, it is on the low rotation side of the twin → single switching determination line L1, and in the region where the axial torque of the torque curve TQ2 during twin turbo is low. Therefore, if the twin turbo mode is maintained and the twin turbo state is maintained in this state, sufficient acceleration performance cannot be obtained even when the accelerator pedal is depressed. Therefore, when it is determined that an acceleration request is required (TH> TH3) while operating in this region, the mode immediately shifts to the single turbo mode, the single turbo state is set, and the torque curve of the high shaft torque during the single turbo 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, the vehicle speed VSP and the set value VSP2 (for example, 2 Km / h) are compared, and the VSP
When it is determined that the vehicle is traveling in VSP2, the process proceeds to step S74 to maintain the twin turbo mode,
When it is determined that the vehicle is in the stopped state with VSP ≦ VSP2, the process returns to step S10 through step S73 as described above, and immediately shifts to the single turbo mode.

The above-mentioned set value VSP2 is for judging the stopped state of the vehicle. When the engine is idled while the vehicle is stopped, for example, when the engine is idling, the engine load TP is increased and the engine speed is increased. The number N rises, the engine operating range shifts from the single turbo range to the twin turbo range, and the twin turbo state is set.
After the accelerator is released, the engine load TP and the engine speed N immediately decrease, and the engine operating range is the twin-> single switching determination line L1 (see FIG. 6 or FIG. 14).
(See) as a boundary, when the mode is switched to the single turbo region again, the mode is not switched to the single turbo mode unless the set time elapses after the transition to the single turbo region (C2 ≧ T4).
During this time, the engine speed N decreases, and after the engine speed N has dropped near the idle speed (for example, around 700 rpm), each switching solenoid valve SOL. The switching of 1 to 4 is performed, and the supercharging pressure relief valve 57 and the control valves 53 and 55 are switched. At this time, since the engine speed N is low, the background noise due to the engine rotation is low, and the driver hears the noise generated when the valves are switched, which gives the driver discomfort. Therefore, when it is determined that the vehicle is stopped (VSP ≦ V
SP2), after shifting to the single turbo region, even if the set time has not elapsed (C2 <T4), by immediately switching to the single turbo mode, each valve is activated before the engine speed decreases and the background noise decreases. To complete the switching and eliminate the discomfort caused by the noise of the valve operation. The switching state from the twin turbo mode to the single turbo mode at this time is shown by a dashed line in FIG.

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

[0125]

As described above in detail, according to the invention described in claim 1, from the single turbo state in which only the primary turbocharger is supercharged to the twin turbo state in which both turbochargers are supercharged. The single-to-twin switching judgment line for judging the switching is corrected to the low rotation speed side as the atmospheric pressure decreases, and the timing of starting full opening of the exhaust control valve is accelerated, and the exhaust flow introduced into the primary turbocharger is Since it is distributed to the secondary turbocharger, even in high altitude running at low atmospheric pressure, etc., the primary turbocharger is prevented from surging due to the overspeed state and reaching the critical speed, and damage is prevented, Improves reliability. Further, since the switching from the single turbo state to the twin turbo state is accelerated as the atmospheric pressure decreases, it is possible to make the driving feeling substantially the same when the operation of the secondary turbocharger is started regardless of the atmospheric pressure change.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, conversely, a twin-to-single switching determination line for determining switching from the twin turbo state to the single turbo state is provided. As with the single-to-twin switching determination line, it is corrected to the low speed side as the atmospheric pressure decreases. During this period, a substantially constant hysteresis can be set at all times, and control hunting for switching the turbocharger operating number can be effectively and reliably prevented.

Further, according to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or the invention described in claim 2, the engine operating region determines whether to switch from the single turbo state to the twin turbo state. After shifting the single-twin switching determination line from the single-turbo region to the twin-turbo region side, the primary turbo overspeed determination line set by atmospheric pressure correction is set to the twin-turbo region side before the set time elapses. When it exceeds, the exhaust control valve is fully opened immediately and the exhaust flow introduced to the primary turbocharger is immediately dispersed to the secondary turbocharger, so when switching from the single turbo state to the twin turbo state, Despite the change in atmospheric pressure, the primary turbocharger is in a super-rotation state due to a sudden increase in exhaust pressure and exhaust flow rate, causing a critical rotation. The occurrence of surging is prevented due to the reach, the thermal load is reduced, damage can be reliably prevented, is more improved reliability.

[Brief description of drawings]

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

[Fig. 2] Same as above

[FIG. 3] Same as above

[Fig. 4] Same as above

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] Conceptual diagram of single → twin atmospheric pressure correction coefficient table

FIG. 8 is an explanatory diagram of an exhaust control valve small open 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 judgment 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 → single atmospheric pressure correction coefficient table.

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

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

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

FIG. 19 is an overall configuration diagram of an engine with a supercharger.

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

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

[Explanation of symbols]

 40 ... Primary turbo supercharger 50 ... Secondary turbo supercharger 53 ... Exhaust control valve 55 ... Intake control valve 100 ... Electronic control unit (ECU) L1 ... Twin → single switching determination line L2 ... Single → twin switching determination line L4 ... Primary turbo overspeed judgment line TP1B… Twin → single switching judgment basic value TP2B… Single → twin switching judgment basic value EM2TP… Primary turbo overspeed judgment basic value 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 → single switching judgment value TP2… Single → twin switching judgment value EMV2TP… Primary turbo overspeed judgment value T1… Exhaust control valve open delay time (set time)

Claims (3)

[Claims] 1. A primary turbocharger (40) and a secondary turbocharger (50) are arranged in parallel in an intake and exhaust system of an engine, and an intake system connected to the secondary turbocharger (50),
Both intake control valve (55) and exhaust control valve (53) are installed in the exhaust system, and both control valves (55,53) are fully opened in the high-speed range to both turbochargers (40,50). In the twin turbo region and the low speed region where both are supercharged, the intake control valve (55) is closed and the exhaust control valve (53) is closed or opened slightly to supercharge only the primary turbocharger (40). The engine operating area is divided into the single turbo area for feeding operation, and the single-to-twin switching judgment value (TP2) is set based on the engine operating area.
Single → twin switching judgment line (L2) set by
After the operating region transitioned from the single turbo region to the twin turbo region side at the boundary, the exhaust control valve (53) was fully opened after the set time (T1), and then the intake control valve (55) was opened. Only the primary turbocharger (40) is switched from the single turbo state of supercharging operation to the twin turbo state of supercharging operation of both turbochargers (40, 50), twin → single switching judgment value
(TP1) above Single-> Twin switching judgment line (L2)
After the twin-single switching determination line (L1), which is set to the lower rotation speed side, is used as a boundary, the engine operating range shifts from the twin-turbo range to the single-turbo range, and then the exhaust control valve (5
3) and the intake control valve (55) are both closed to both turbochargers
(40,50) In the control method of an engine with a supercharger that switches from the twin turbo state of supercharging operation to the single turbo state of only the primary turbocharger (40), the standard large size is set in advance based on the engine operating state. Refer to the table that stores the basic value for single → twin switching (TP2B) at atmospheric pressure, and then select the basic value for single → twin switching (TP2B)
Based on the atmospheric pressure (ALT), the lower the atmospheric pressure (ALT), the smaller the value of the single → twin atmospheric pressure correction coefficient (KTWNALT) is set, and the above single → twin switching judgment basic value (TP2B) → A method for controlling an engine with a supercharger, characterized in that the above single-to-twin switching judgment value (TP2) is set by correcting with a twin atmospheric pressure correction coefficient (KTWNALT). 2. The twin-single switching determination basic value (TP1B) is set by referring to a table in which the twin-single switching determination basic value (TP1B) at standard atmospheric pressure is stored in advance based on the engine operating state. Based on the atmospheric pressure (ALT), the lower the atmospheric pressure (ALT), the smaller the value of twin → single atmospheric pressure correction coefficient (KSGLALT) is set, and the twin → single switching judgment basic value (TP1B) is set to twin →
The method for controlling an engine with a supercharger according to claim 1, wherein the twin-to-single switching determination value (TP1) is set by performing a correction with a single atmospheric pressure correction coefficient (KSGLALT). 3. A primary turbo overspeed determination basic value (EM2TP) for determining overspeed of the primary turbocharger (40) in a single turbo state and standard atmospheric pressure based on the engine operating state is stored in advance. Set the primary turbo overspeed judgment basic value (EM2TP) by referring to the table, and set the judgment value atmospheric pressure correction coefficient (KEM2) that is smaller as the atmospheric pressure (ALT) is lower, based on the atmospheric pressure (ALT). , The primary turbo overspeed judgment basic value (EM2TP) is corrected by the judgment value atmospheric pressure correction coefficient (KEM2) to set the primary turbo overspeed judgment value (EMV2TP), and before the set time (T1) elapses, The exhaust control valve (53) is fully opened when the engine operating region exceeds the primary turbo overspeed determination line (L4) by the primary turbo overspeed determination value (EMV2TP) to the twin turbo region side. 1 or bill Item 3. A control method for an engine with a supercharger according to Item 2.