JPH07145734A - Control method for engine with supercharger - Google Patents

Abstract

PURPOSE:To prevent generation of torque shock while improving reliability of a primary turbo supercharger and a secondary turbo supercharger regardless of engine operating condition when the engine operating condition is switched from single-turbo condition to twin-turbo condition. CONSTITUTION:Just after an engine operating range is transferred from a single turbo range to a twin turbo range across a single-to-twin switching judging boarder line, a pressure difference reduction rate DELTADPS between upstream pressure and downstream pressure of an intake air control valve is calculated (Step S40) the more the pressure difference reducing rate DELTADPS is the shorter the first setting time T2 for applying the fully opening timing of an exhaust control valve and a second setting time T3 for applying the opening timing of the intake air control valve are set. (Step S41, S42) After the first set time T2 is passed, the exhaust control valve is fully opened (Step S47), and after the second set time T3 is passed the intake air control valve is opened (Step S49). And then engine operation is switched from single turbo condition in which only a primary turbo supercharger is operated to twin turbo condition in which both turbo superchargers are operated.

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 and exhaust system of an engine, and is arranged in an intake and exhaust system on the secondary turbocharger side. The engine with a supercharger that controls the supercharging operation of the secondary turbocharger by opening and closing the intake control valve and the exhaust control valve that are operated is described in detail. The present invention relates to a control method for an engine with a supercharger, which improves the reliability of a primary turbocharger and a secondary turbocharger when switching the supercharger operation to a twin turbo state and prevents torque shock.

[0002]

2. Description of the Related Art A primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine,
An intake control valve is installed in the intake system connected downstream of the blower of the secondary turbocharger, and an exhaust control valve is installed in the exhaust system connected upstream of the turbine. The engine operating range is in the low speed single turbo range. Occasionally, the intake control valve is closed and the exhaust control valve is closed, or the secondary turbocharger is opened slightly to preliminarily rotate it, and the supercharge operation of the secondary turbocharger is stopped to stop the primary turbocharger only. When the operating range is in the high speed twin turbo range, both control valves are fully opened to supercharge both turbochargers, improving output performance from the low speed range to the high speed range. An engine with a supercharger that makes it possible is known. Then, when the engine operating region shifts from the single turbo region to the twin turbo region side with the preset single-to-twin switching determination line as the boundary, only the primary turbo supercharger operates from the single turbo state and both turbo superchargers operate. I am trying to switch to the twin turbo state.

Here, from the single turbo state in which only the primary turbocharger is supercharged by closing both control valves or slightly opening the exhaust control valve, both control valves are fully opened to operate both turbochargers. When transitioning to the twin turbo state of
Since the flow rate of exhaust gas flowing into the turbine of the primary turbocharger drops significantly in a short time, and it takes some time for the secondary turbocharger to reach the rotation speed at which full-scale supercharging is performed. The supercharging pressure drops temporarily and torque shock occurs.

To cope with this, when the engine operating region shifts from the single turbo region to the twin turbo region with the single-to-twin switching determination line as a boundary, the exhaust control valve is opened small or the exhaust control valve is opened small. After the first set time has passed since the transition to the twin turbo range, the exhaust control valve is fully opened after the preliminary rotation speed of the secondary turbocharger has been sufficiently increased, and the secondary turbocharger The intake control valve is opened after the second set time, which can be considered as a sufficiently high blower pressure, and only the primary turbocharger is in the single turbo state where the turbocharger is operating, and the twin turbocharger is operating in the twin turbocharger. To prevent the torque fluctuation due to the temporary decrease in boost pressure that occurs when switching from the single turbo state to the twin turbo state. And so as to stop (JP-4-
(See Japanese Patent No. 164126).

[0005]

However, in the above-mentioned prior art example, the first condition for fully opening the exhaust control valve is provided when switching from the single turbo state to the twin turbo state.
And the second set time that gives the condition for opening the intake control valve are set to unique values, so that there is the following inconvenience.

When the engine operating region shifts from the single turbo region to the twin turbo region at the boundary of the single-to-twin switching determination line under the high engine load condition,
Since the exhaust control valve is closed or slightly open until the set time of the above is exceeded, most of the exhaust gas is introduced to the primary turbocharger, and the primary turbocharger increases due to the rapid increase in the exhaust flow rate and exhaust pressure due to high load operation. There is a possibility that the turbocharger will be in an over-rotation state and will reach a critical rotational speed to cause surging, and that the heat load will damage the primary turbocharger. Further, at this time, after the exhaust control valve is fully opened, the secondary turbocharger preliminary rotation speed immediately increases with high load operation,
Since the intake control valve is in the closed state until the second set time elapses, the blower pressure due to the secondary turbocharger between the turbine downstream of the secondary turbocharger and the intake control valve also rises sharply, and the blower pressure increases. The abnormal rise in pressure causes surging of the secondary turbocharger, which deteriorates reliability.

In order to cope with this, if the first set time for giving the exhaust control valve full opening timing and the second set time for giving the intake control valve opening timing are set short, switching in the engine low load state is performed. At times, exhaust energy is relatively large at one time due to the increase in the secondary turbocharger backup speed when the exhaust control valve is fully opened when the exhaust energy is low, and the secondary turbocharger backup speed is sufficient. Since the intake control valve is opened in a state where the blower pressure by the secondary turbocharger does not rise sufficiently and does not rise, the synergistic effect of these causes a temporary decrease in the supercharging pressure and causes a torque shock. .

That is, when the first set time and the second set time are set to unique values, when switching from the single turbo state to the twin turbo state, when switching is performed in the engine high load state. It is not possible to achieve both the prevention of surging of the primary turbocharger and the secondary turbocharger to improve reliability and the prevention of the occurrence of torque shock when switching in the engine low load state.

In view of the above-mentioned circumstances, the present invention improves the reliability of the primary turbocharger and the secondary turbocharger regardless of the engine operating state when switching from the single turbo state to the twin turbo state, and also provides torque shock. It is an object of the present invention to provide a method for controlling an engine with a supercharger capable of preventing the occurrence of the above.

[0010]

In order to achieve the above object, the present invention provides a secondary turbocharger in which a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine. An intake control valve is installed in the intake system connected downstream of the blower, and an exhaust control valve is installed in the exhaust system connected upstream of the turbine, and both control valves are fully opened in the high-speed range to open both turbochargers. The engine has a twin turbo region in which both of them are supercharged and a single turbo region in which the intake control valve is closed in the low speed region and the exhaust control valve is closed or opened slightly to supercharge only the above primary turbocharger. The operating area is divided and the operating area is a single turbo area with a single-to-twin switching judgment line set based on the engine operating area set as a single-to-twin switching judgment line. The exhaust control valve is opened or maintained at a small level when the engine shifts to the twin turbo region side, the exhaust control valve is fully opened after the lapse of the first set time, and the intake control valve is opened after the lapse of the second set time. In the control method for a supercharged engine in which the valve is opened and only the primary turbocharger is switched from the supercharged single turbo state to the dual turbocharger operated twin turbo state, the engine operating range is the single-to-twin switching judgment. Immediately after the transition from the single turbo region to the twin turbo region at the line, the differential pressure decrease rate between the upstream pressure and the downstream pressure of the intake control valve is calculated, and the differential pressure decrease rate is calculated based on the differential pressure decrease rate. The larger the value, the shorter the first set time and the second set time are set.

[0011]

In the control method for the engine with a supercharger described above, immediately after the engine operating region shifts from the single turbo region to the twin turbo region side with the single → twin switching determination line as a boundary, the upstream pressure and the downstream pressure of the intake control valve are reduced. The decrease rate of the differential pressure from the pressure is calculated, and the larger the differential pressure decrease rate is, the first set time for giving the full opening timing of the exhaust control valve and the second set time for giving the open timing of the intake control valve. Set to a short value.

Therefore, when switching from the single turbo state in which only the primary turbocharger is operating to the twin turbo state in which both turbochargers are operating, the differential pressure reduction rate between the upstream pressure and the downstream pressure of the intake control valve is large and the engine is operating. The higher the load, the earlier the exhaust control valve is fully opened, and the exhaust introduced into the primary turbocharger is immediately distributed to the secondary turbocharger.At this time, the intake control valve is opened earlier. And it is quickly switched to the twin turbo state.

Further, the smaller the differential pressure reduction rate and the smaller the load, the longer the first set time and the second set time are set, and after the preliminary rotational speed of the secondary turbocharger has sufficiently increased, the exhaust control valve Is fully opened, and the intake control valve is opened in a state where the blower pressure by the secondary turbocharger is sufficiently increased to switch to the twin turbo state.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, an overall configuration of a supercharged engine to which the present invention is applied will be described. Reference numeral 1 denotes an engine body of a horizontally opposed engine (a 4-cylinder engine in this embodiment), and combustion chambers 5, intake ports 6, exhaust ports 7, spark plugs 8 are provided in the left and right banks 3 and 4 of the crankcase 2. A valve mechanism 9 and the like are provided. And # 2 and # 4 cylinders on the left bank 3 side, and # 1 and # 1 cylinders on the right bank 4 side.
Equipped with # 3 cylinder. Further, due to this engine shortening shape, the primary turbocharger 40 is provided immediately after the left and right banks 3 and 4.
And a secondary turbocharger 50 are provided respectively. As an exhaust system, a common exhaust pipe 10 from the left and right banks 3 and 4 includes turbines 40a of both turbochargers 40 and 50,
50a, the exhaust pipes 11 from the turbines 40a, 50a merge into one exhaust pipe 12, and the catalytic converter 1
3 、 Communicated with muffler 14.

The primary turbocharger 40 is a low-capacity low-speed type having a large supercharging capacity in the low and medium speed range, whereas the secondary turbocharger 50 has a large supercharging capacity in the middle and high speed range. It is a large-capacity, high-speed type. Therefore, the primary turbocharger 40 has a smaller capacity, so that the exhaust resistance becomes larger.

As an intake system, an intake pipe 16 connected to the air cleaner 15 is divided into two intake pipes 17a and 17b.
Are the blowers 40b of both turbochargers 40 and 50,
The intake pipes 18, 19 from the blowers 40b, 50b are communicated with 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 each cylinder of the left and right banks 3 and 4 via an intake manifold 23. Further, as an idle control system, the intake pipe 1 immediately downstream of the air cleaner 15
6 in the bypass passage 24 between the intake manifold 23,
Idle control valve (ISCV) 25 and check valve 2 that opens with negative pressure
6 is provided so as to control the intake air amount during idling or deceleration.

As a fuel system, an injector 30 is arranged near the port of the intake manifold 23, and the fuel pump 3
The fuel passage 33 from the fuel tank 32 having the No. 1 is connected to the injector 30 with the filter 34 and the fuel pressure regulator 35. The fuel pressure regulator 35 adjusts according to the intake pressure, whereby the fuel pressure supplied to the injector 30 is always kept at a constant height with respect to the intake pressure, and the fuel injection control is performed by the pulse width of the injection signal. It is possible to do. As an ignition system, it is connected so that an ignition signal from an igniter 36 is input to each ignition coil 8a that is continuously provided for each ignition plug 8 of each cylinder.

The operation system of the primary turbocharger 40 will be described. The primary turbocharger 40 operates to rotationally drive the blower 40b by the exhaust energy introduced into the turbine 40a to suck and compress air to constantly supercharge it. A primary wastegate valve 41 equipped with a diaphragm-type primary wastegate valve actuating actuator 42 is provided on the turbine side. A control pressure passage 44 directly downstream of the blower 40b communicates with the pressure chamber of the actuator 42 through an orifice 48 so that the primary wastegate valve 41 can be opened responsively when the boost pressure rises above a set value. To be done. In addition, the control pressure passage 4
4 is a primary waste gate control duty solenoid valve 4 for further leaking the boost pressure to the upstream side of the blower 40b.
3, the duty solenoid valve 43 generates a predetermined control pressure and acts on the actuator 42 to change the opening of the primary waste gate valve 41 to control the supercharging pressure. Here, the primary wastegate control duty solenoid valve 43 is operated 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 primary wastegate valve 41 is increased by a high control pressure. As the supercharging pressure decreases and the duty ratio increases, the control pressure decreases due to the increase in the leak amount, and the opening degree of the primary waste gate valve 41 is reduced to increase the supercharging pressure.

On the other hand, in order to prevent the lowering of the blower rotation and the occurrence of intake noise when the throttle valve is rapidly closed, the intercooler 2 near the throttle valve 21 is provided downstream of the blower 40b.
The bypass passage 46 is connected between the outlet side of 0 and the upstream of the blower 40b. An air bypass valve 45 is provided in the bypass passage 46 so as to introduce a manifold negative pressure through a passage 47 and open when the throttle valve is rapidly closed, so that pressurized air trapped downstream of the blower is quickly leaked.

The operation system of the secondary turbocharger 50 will be described. In the secondary turbocharger 50, similarly, the turbine 50a and the blower 50b are rotationally driven by exhaust gas to supercharge, and a secondary wastegate valve 51 having a secondary wastegate valve actuating actuator 52 is provided on the turbine side. ing. Further, a downstream open type exhaust control valve 53 provided with a diaphragm type exhaust control valve actuating actuator 54 is provided in the exhaust pipe 10 upstream of the turbine 50a, and a similar diaphragm type intake control is provided downstream of the blower 50b. A butterfly type intake control valve 55 having a valve actuating actuator 56 is provided, and a diaphragm type supercharging pressure relief valve 57 is provided in a relief passage 58 between above and downstream of the blower 50b.

The pressure operation system of each of these valves will be described. First, the surge tank 60 of the negative pressure source has a check valve 62
Is communicated with the intake manifold 23 by a passage 61 having a valve for storing negative pressure and buffering pulsating pressure when the throttle valve is fully closed. Further, a switching solenoid valve SOL. For supercharging pressure relief valve that opens and closes the supercharging pressure relief valve 57. 1, intake control valve 55
Intake control valve switching solenoid valve SOL. 2,
The switching solenoid valve SOL. For the first and second exhaust control valves for opening and closing the exhaust control valve 53. 3, SOL. 4, exhaust control valve 5
Exhaust control valve small open control duty solenoid valve 75 for opening small 3 and secondary wastegate valve switching solenoid valve 70 for opening and closing secondary wastegate valve 51.
Have. Each switching solenoid valve 70, SOL. 1-4
Is a negative pressure in the negative pressure passage 63 from the surge tank 60 by the ON / OFF signal from the electronic control unit 100, a positive pressure from the positive pressure passages 64a and 64b communicating with the intake control valve downstream,
The atmospheric pressure or the like is selected and guided to the actuator side by the control pressure passages 70a to 74a to guide the secondary waste gate valve 51, the boost pressure relief valve 57, and both control valves 55 and 53.
To operate. The duty solenoid valve 75 variably controls the positive pressure acting on the positive pressure chamber 54a of the actuator 54 by the duty signal from the electronic control unit 100,
The exhaust control valve 53 is controlled to be small open.

The switching solenoid 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 and the negative pressure passage 63
Side, the actuator 5 is opened via the control pressure passage 72a.
By introducing a negative pressure into the pressure chamber in which the spring 6 is installed, the intake control valve 55 is closed against the biasing force of the spring, and
Then, the negative pressure passage 63 side is closed to open the atmosphere port, and the pressure chamber of the actuator 56 is opened to the atmosphere, so that the intake control valve 55 is opened by the biasing force of the spring in the pressure chamber.

The secondary wastegate valve switching solenoid valve 70 is turned on only when the electronic control unit 100 determines that high-octane gasoline is used based on the ignition advance amount and the like.
It is turned on and turned on when it is determined that regular gasoline is used. When the secondary wastegate valve switching solenoid valve 70 is turned off, the intake control valve 5
5, the positive pressure passage 65 communicating with the upstream side of 5 is closed to open the atmospheric port, and the atmospheric pressure is introduced into the actuator 52 through the control pressure passage 70a. The waste gate valve 51 is closed. Further, when turned on, the atmosphere port is closed to open the positive pressure passage 65, and the supercharging pressure downstream of the secondary turbocharger 50 when both turbochargers 40 and 50 are operating is guided to the actuator 52, and this supercharging pressure is increased. Accordingly, the secondary waste gate valve 51 is opened, and the supercharging pressure is relatively reduced when using regular gasoline as compared to when using high-octane gasoline.

In addition, the first exhaust control valve switching solenoid valve SOL. 3 from the control pressure passage 73a to the positive pressure chamber 54a of the exhaust control valve actuating actuator 54, the second exhaust control valve switching solenoid valve SOL. Control pressure passage 7 from 4
4a are respectively connected to the negative pressure chambers 54b in which the springs of the actuator 54 are installed. When both the switching solenoid valves SOL3, 4 are OFF, the first exhaust control valve switching solenoid valve SOL. 3 is a positive pressure passage 64b
Side is closed to open the atmosphere port, and the second exhaust control valve switching solenoid valve SOL. By closing the negative pressure passage 63 side and opening the atmosphere port 4, the both chambers 54 of the actuator 54
The a and 54b are opened to the atmosphere, and the exhaust control valve 53 is fully closed by the urging force of the spring installed in the negative pressure chamber 54b.
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 opens the positive pressure passage 64b side, and the second exhaust control valve switching solenoid valve SOL. 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 to fully open the exhaust control valve 53 against the biasing force of the spring.

First exhaust control valve switching solenoid valve SO
L. The control pressure passage 73a from the No. 3 is provided with an orifice 67, the leak passage 66 is connected to the downstream side of the orifice 67 and the intake pipe 17a, and the exhaust passage operated by the duty signal from the electronic control unit 100 is connected to the leak passage 66. A control valve small opening control duty solenoid valve 75 is provided. The first exhaust control valve switching solenoid valve SOL. When only 3 is ON and 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 duty solenoid valve 75 leaks the positive pressure and the exhaust control valve 53 is opened slightly. Here, when the duty ratio in the duty signal is large, the exhaust control valve small opening control duty solenoid valve 75 lowers the positive pressure acting on the positive pressure chamber 54a due to the increase in the leak amount, and the exhaust control valve 5
3, the positive opening is increased as the duty ratio becomes smaller to increase the opening of the exhaust control valve 53.
When the engine operating condition is within the predetermined exhaust control valve small opening control region under the single turbo condition in which only the primary turbocharger 40 is supercharged, the opening degree of the exhaust control valve 53 by the duty solenoid valve 75 becomes excessive. The supply pressure is feedback-controlled, and the exhaust control valve 53 is associated with this supercharging pressure control.
Is opened to preliminarily rotate the secondary turbocharger 50.

Various sensors will be described. A differential pressure sensor 80 and an absolute pressure sensor 81 are provided in the engine intake system. The differential pressure sensor 80 communicates above and downstream of the intake control valve of the intake pipe 19 through the passages 79a and 79b to constantly detect the differential pressure between the upstream and downstream of the intake control valve 55. Further, an intake pipe pressure / atmospheric pressure switching solenoid valve 76 having an atmospheric port is provided, and the switching solenoid valve 76 is connected to the intake manifold 23 and the absolute pressure sensor 81 by passages 77 and 78. The absolute pressure sensor 81 is connected to the atmospheric port to detect the atmospheric pressure by the ON / OFF signal of the electronic control unit 100, or is connected to the intake manifold 23 to detect the intake pipe pressure (actual supercharging pressure).

In the engine body 1, a knock sensor 82 is attached, a water temperature sensor 83 is exposed in a cooling water passage connecting the left and right banks 3 and 4, and an O ₂ gas is passed through the exhaust pipe 10.
The sensor 84 is exposed. A throttle sensor 85 including a throttle opening sensor and an idle switch for detecting a fully closed throttle is connected to the throttle valve 21 in series, and an intake air amount sensor 86 is provided immediately downstream of the air cleaner 15.
Is provided. Further, a crank rotor 90 is rotatably mounted on a crank shaft 1a supported by the engine body 1, and a crank angle sensor 87 composed of an electromagnetic pickup or the like is provided on the outer periphery of the crank rotor 90 so as to be opposed thereto. Furthermore,
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.

Next, the structure of the electronic control system will be described with reference to FIG. An electronic control unit (ECU) 100 is a main computer 101 that performs turbocharger operation number switching control, supercharging pressure control, fuel injection control, ignition timing control, and the like.
And a sub-computer 102 dedicated to knock detection processing. The constant voltage circuit 103 and the drive circuit 1 which supply a predetermined stabilizing power supply to each unit are mainly configured.
Peripheral circuits such as 04 are incorporated.

The constant voltage circuit 103 is a power source relay 97.
Is connected to the battery 95 via a relay contact of
The relay coil of the power supply relay 97 is connected to the battery 95 via an ignition switch 96. Further, the constant voltage circuit 103 is directly connected to the battery 95, and further, the fuel pump 31 is connected via a relay contact of the fuel pump relay 98. That is, the constant voltage circuit 103 supplies the control power supply when the ignition switch 96 is turned on and the relay contact of the power supply relay 97 is closed when the engine is operated, and the ignition switch 96 is turned off. Even in this case, the backup power is supplied to the backup RAM 108 described later.

The main computer 101 is a CPU
105, R0M106, RAM107, constant voltage circuit 103 even when the ignition switch 96 is turned off.
A backup RAM 108 for supplying data from a backup power source to hold data, a counter / timer group 109,
Serial communication interface (SCI) 112 and I
The / O interface 110 is a microcomputer connected via a bus line 111. The counter / timer group includes a free-running counter, a counter for counting the input of a cam pulse signal from the cam angle sensor 88 (used when determining a cylinder), and a counter for counting the input interval of a crank pulse signal from the crank angle sensor 87. For the sake of convenience, a regular interrupt timer (used for calculating the engine speed), a regular interrupt timer for generating a regular interrupt of each job in the program, a watchdog timer for system abnormality monitoring, and the like are collectively referred to in the main computer 101. In addition, various software counters and timers are used.

The sub-computer 102, like the main computer 101, has CPUs 113,
R0M114, RAM115, counter / timer group 11
6, I / O interface 117, and SCI 118
Is a microcomputer connected via a bus line 119, and the main computer 101 and the sub computer 102 are connected to each other via a serial communication line via SCIs 112 and 118.

The I / O interface 110 of the main computer 101 has various sensors 80, 81, 83 to 88 other than the knock sensor 82, a vehicle speed sensor 89, an ignition switch 96, a starter switch 92, and a battery 95 at the input port. Are connected. Also, the output port of the I / O interface 110 is
The igniter 36 is connected and I
SCV25, injector 30, each switching solenoid valve 7
0,76, SOL. 1-4, duty solenoid valve 4
3, 75 and the relay coil of the fuel pump relay 98 are connected, and further, the ignition switch 96
A self-shut signal line is connected between the ignition switch 96 and the relay coil of the power supply relay 97 in order to keep the power supply for a predetermined time even after is turned off from ON.

On the other hand, the crank angle sensor 87 and the cam angle sensor 88 are connected to the input port of the I / O interface 117 of the sub computer 102, and the knock sensor 82 is connected to the amplifier 120 and the frequency filter 12.
1, the A / D converter 122 is connected, and after the knock detection signal from the knock sensor 82 is amplified to a predetermined level by the amplifier 120, the necessary frequency component is extracted by the frequency filter 121, and A / It is converted into a digital signal by the D converter 122 and input to the sub computer 102.

Then, the ignition switch 96 is turned off.
When the power is turned on, the power relay 97 is turned on, the ECU 100 is powered on, a constant voltage is supplied to each part via the constant voltage circuit 103, the main computer 101 executes various controls, and the sub computer 102 detects knock. Execute the process. That is, in the main computer 101, the CPU 105 uses the programs stored in the ROM 106 to detect the detection signals from the various sensors 80, 81, 83 to 89 and the switches 92, 96 via the I / O interface 110. Input processing of signals, battery voltage V, etc., RAM 107 and backup R
Various control amounts are calculated based on various data stored in the AM 108 and fixed data stored in the memory R0Ml06. The drive circuit 104 causes the fuel pump relay 98
Is turned on to energize and drive the fuel pump 31,
Each switching solenoid valve 70, 7 via the drive circuit 104
6, SOL. The ON / OFF signals are output to 1 to 4 and the duty signals to the duty solenoid valves 43 and 75 to output the turbocharger operation number switching control and the supercharging pressure control,
A drive pulse width signal corresponding to the calculated fuel injection pulse width is output to the injector 30 of the corresponding cylinder at a predetermined timing to perform fuel injection control, and an ignition signal is sent to the igniter 36 at a timing corresponding to the calculated ignition timing. It is output to execute ignition timing control, and a control signal is output to the ISCV 25 to execute idle speed control and the like.

Further, in the sub computer 102, the engine speed N and the engine load (for example, the basic fuel injection pulse width Tp [= K × Q / N, K is an injector characteristic correction constant, Q is the intake air amount] are used). A sample section (crank angle section) of the signal from the knock sensor 82 is set on the basis of and, and when the sample section is reached, the signal from the knock sensor 82 is A / D converted at high speed by the A / D converter 122. Then, the vibration waveform is faithfully converted into digital data, and the occurrence of knock is determined based on this digital data.

The output port of the I / O interface 117 of the sub computer 102 is the main computer 1
01 is connected to the input port of the I / O interface 110, and the knock determination result in the sub computer 102 is output to the I / O interface 117. Then, the main computer 101 outputs the knocking occurrence determination result from the sub computer 102,
Knock data is read through the serial communication line via the SCI 112, and the ignition timing of the cylinder concerned is immediately retarded based on this knock data to avoid knock.

The I / O of the main computer 101
A read memory switch 123 and a test mode switch 124, which are connectors, are connected to the interface 110. Then, turn on the test mode switch 124 at the factory line end or dealer.
By setting to N (connector connection state), the main computer 101 and the sub computer 102 are switched from the normal control mode to the preset test mode, and the test mode control is executed to perform various inspections and inspections. Is possible. Further, when the read memory switch 123 is turned on (connector connected state), when the external device (not shown) is connected, the main computer 1
01 or the data in the sub computer 102 is sent to an external device, and the failure diagnosis can be performed by displaying the data on the external device.

Next, the supercharger operation 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 turns on the ignition switch 96.
After that, it is executed every set time (for example, 10 msec). When the ignition switch 96 is turned on, the ECU 1
When the power is turned on to 00, the system is initialized (clear each flag and each count value), and first, in step S1, the value of the twin turbo mode determination flag F1 is referred to. Then, this twin turbo mode discrimination flag F
If 1 is cleared, the process proceeds to step S2, and 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, and in the twin turbo mode in which both turbochargers 40 and 50 are supercharged. Sometimes set.

In the following description, the single turbo mode will be described first, then the single-to-twin switching control,
The twin turbo mode, and finally twin-to-single switching control will be described. Turn on the ignition switch 96
Immediately after that, and when the current control state is the single turbo mode, since F1 = 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 state to the twin turbo state at the standard atmospheric pressure (760 mmHg). As shown in FIG. 10, 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 (basic fuel injection pulse width in this embodiment) Tp. The twin switching determination line L2 and, conversely, the twin → single switching determination line L1 for switching from the twin turbo mode to the single turbo mode are previously obtained from experiments and the like under standard atmospheric pressure, and the single turbo region and the twin turbo region are set. There is. And each line L2, L
Corresponding to 1, a single → twin switching judgment basic value Tp2B and a twin → single switching judgment basic value Tp1
B is stored in advance in a series of addresses in the ROM 102 as a table with the engine speed N as a parameter.

Here, the single-to-twin switching determination line L
2 is a torque curve TQ at the time of single turbo of the engine output characteristic shown in FIG. 12 in order to prevent torque fluctuation at the time of switching.
It is necessary to set the point C where 1 and the torque curve TQ2 at the time of twin turbo match, and therefore, as shown in FIG. 10, depending on the increase of the engine speed N from the high load in the low and medium speed range. Is set to the low load side. Further, as shown in the figure, in order to prevent control hunting at the time of switching the turbocharger operating number, twin-to-single switching determination line L1
Is set to have a relatively wide hysteresis on the low rotation speed side with respect to the single-to-twin switching determination line L2.

Next, in step S3, the atmospheric pressure correction coefficient table is referred to with interpolation calculation based on the atmospheric pressure (absolute pressure value) ALT, and the single-to-twin atmospheric pressure correction coefficient K is entered.
Set TWNALT (0 <KTWNALT ≦ 1.0). As shown in FIG. 9A, in this atmospheric pressure correction coefficient table, the standard atmospheric pressure (760 mmHg) is set to 1.0, and a single-to-twin atmospheric pressure correction coefficient KTWNALT having a smaller value is stored as the atmospheric pressure decreases. Has been done.

Then, in step S4, the single
The twin switching determination basic value Tp2B is corrected by the single → twin atmospheric pressure correction coefficient KTWNALT to set the single → twin switching determination 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 <
In the case of Tp2, the process proceeds to step S6. 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.

Single-twin switching judgment value Tp2
Is the above single → twin atmospheric pressure correction coefficient KTWNAL
With T, the lower the atmospheric pressure ALT, the smaller the correction value. Therefore, as the atmospheric pressure ALT becomes lower, the single-twin switching determination value Tp2 causes the primary turbocharger 40 to change from the single turbo state in which only the primary turbocharger 40 is supercharged to the twin turbocharger in which both turbochargers 40 and 50 are supercharged. The single-to-twin switching determination line L2 for determining the switching to is corrected to the low load and low rotation side as indicated by the alternate long and short dash line with respect to the case of the standard atmospheric pressure indicated by the solid line in FIG.

As a result, the timing of transition of the engine operating region from the single turbo region side to the twin turbo region side is advanced with the single → twin switching determination line L2 as a boundary, and the transition from the single turbo mode to the single → twin switching control is performed. 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 is, the higher the differential pressure between the target supercharging pressure and the atmospheric pressure becomes, and the predetermined target supercharging pressure is reached. In order to obtain, 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 increases as the engine speed N representing the engine operating state 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 introduced into the primary turbocharger 40. Therefore, the lower the atmospheric pressure, the more the primary turbocharger 40 is in the overspeed state. Engine operating range is low load,
Expanded to the low rotation side. As described above, this becomes remarkable when the primary turbocharger 40 is a low-speed type small capacity. Therefore, the lower the atmospheric pressure ALT is, the earlier the timing of shifting from the single turbo mode based on the engine operating state to the single-to-twin switching control is advanced, and the later the exhaust control valve 53 is fully opened. The exhaust flow introduced into the primary turbocharger 40 is dispersed in the secondary turbocharger 50 to prevent the primary turbocharger 40 from over-rotating. Thereby, the primary turbocharger 40
Atmospheric pressure AL occurs due to surging caused by an increase in exhaust pressure and exhaust flow, resulting in a critical speed
It is prevented regardless of changes in T, and damage is prevented.

Even in the same engine operating condition, the rate of increase in the rotational speed of the primary turbocharger 40 changes under the single turbo condition due to atmospheric pressure fluctuations, and the operating feeling changes when the operation of the secondary turbocharger 50 starts. However, the lower the atmospheric pressure ALT, the faster the switching to the twin-turbo state, so that the driving feeling associated with the operation start of the secondary turbocharger 50 can be omitted regardless of the atmospheric pressure change (for example, highland traveling and lowland traveling). Can be the same.

On the other hand, in step S5, Tp <Tp2
Therefore, when the process proceeds to step S6, the single turbo mode control is performed. When the process proceeds to step S6, the value of the supercharging pressure control mode determination flag F2 is referred to. The supercharging pressure control mode determination flag F2 indicates that the current operation region is the exhaust control valve 5
Exhaust control valve for preliminarily rotating the secondary turbocharger 50 by the small opening of 3 is set when it is in the small opening control mode region, and is cleared when it is outside the region.

Therefore, the ignition switch 96 is turned off.
Immediately after N, the 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, and the condition determination of steps S7 to S9 is performed. It is determined whether or not the current operation area has moved into the exhaust control valve small open control mode area.

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 low rotation / low load side of L2, that is, in the single turbo mode, the set value N2 (for example, 265
0 rpm) and P2 (for example, 1120 mmHg), and when the throttle opening TH is equal to or greater than the set value TH2 (for example, 30 deg), it is determined that the shift has occurred within the region.

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 <N2,
Alternatively, if 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 open control mode region, and the supercharging pressure control mode determination flag F2 is cleared. On the other hand, 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 moved into the exhaust control valve small open control mode region, and the supercharging pressure control mode determination flag F2 is set.

Then, the routine proceeds to step S12, and the 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 S20, the twin turbo mode determination flag F1, the differential pressure initial value reading flag FINI, which will be described later, the reduction rate calculation flag F3, and the twin turbo region duration 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. Since the negative pressure from the surge tank 60 is introduced into the pressure chamber when the switch 1 is turned off, the valve is opened against the biasing force of the spring.
5 is a switching solenoid valve SOL. 2 OF
Negative pressure is introduced into the pressure chamber of the actuator 56 by F, so that the valve is closed against the biasing force of the spring. Further, the exhaust control valve 53 is a switching solenoid valve S0L. When 3 and 4 are turned off, atmospheric pressure is introduced into both chambers 54a and 54b of the actuator 54 to close the valve by the biasing force of the spring.

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

When the exhaust control valve is in the small open control mode range under the single turbo mode or in the twin turbo mode described later, the boost pressure feedback control is
Although not detailed here, the primary waste gate valve 41
The target supercharging pressure is compared with the actual supercharging pressure detected by the absolute pressure sensor 81, and the duty solenoid valve 4 is controlled by, for example, PI control according to the comparison result.
ON duty (duty ratio) for 3 is calculated,
This is executed by outputting the duty signal of this ON duty to the duty solenoid valve 43.

On the other hand, if it is determined in step S11 that the current operation region is within the exhaust control valve small open control mode region and the boost pressure control mode determination flag F2 is set, steps S12 to S14 are executed. Through the first exhaust control valve switching solenoid valve SOL. Three
Only turns on. Therefore, the first exhaust control valve switching solenoid valve SOL. When 3 is turned on, positive pressure is introduced into the positive pressure chamber 54a of the exhaust control valve actuating actuator 54, and the exhaust control valve 53 is opened.

In this exhaust control valve small opening control mode, the exhaust control valve 53 is used to perform supercharging pressure feedback control, and the exhaust control valve 53 is opened small accordingly. That is, the target supercharging pressure is compared with the actual supercharging pressure detected by the absolute pressure sensor 81, and, for example, PI is determined according to the comparison result.
By control, an ON duty (duty ratio) for the exhaust control valve small opening control duty solenoid valve 75 is calculated, a duty signal of this ON duty is output to the duty solenoid valve 75, and supercharging pressure feedback control is executed. For this reason, the positive pressure acting on the positive pressure chamber 54a of the actuator 54 is regulated by the duty solenoid valve 75, the exhaust control valve 53 is slightly opened as shown in FIG. 13, and only the exhaust control valve 53 is used. Supply pressure feedback control is performed. 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, and the secondary turbocharger 50 is preliminarily rotated to prepare for the transition to the twin turbo.

In this exhaust control valve small open state, the secondary turbocharger 50 is rotating and the intake control valve 55 is closed, so that the blower 5 of the secondary turbocharger 50 is closed.
The supercharging pressure is contained between the downstream side of 0b and the intake control valve 55. At this time, the supercharging pressure relief valve 57 is opened to leak the supercharging pressure and smooth the preliminary rotation.

If the 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 process from step S6 is started. The process proceeds to step S22, and it is determined whether the current operating region has moved out of the exhaust control valve small open control mode region by the condition determination of steps S22 to S24.

In order to prevent the control hunting at the time of switching the exhaust control valve to the small open state, the determination of the shift to the outside of this region is performed as shown in FIG. 8, so that the set value N1 lower than the set values N2, P2 and TH2 is set. (Eg 2600 rpm), P1 (eg 1
070 mmHg), TH1 (for example, 25 deg). Then, in step S22, the engine speed N and the set value N1 are compared, in step S23, the intake pipe pressure (supercharging pressure) P and the set value P1 are compared, and in step S24, the sroll opening TH and the set value TH1 are compared. And N <N1,
Alternatively, if P <P1 or TH <TH1, it is determined that the current operating region has moved outside the exhaust control valve small open control mode region, and the routine proceeds to step S10 described above, where the boost pressure control mode determination flag F2 is set. clear. As a result, the exhaust control valve small opening control is released. Also, N ≧ N1 and P ≧ P1 and TH
If ≧ TH1, it is determined that the current operating region is still within the exhaust control valve small open control region, and the routine proceeds to step S11, where 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 blower 40b. Then, the blower 40b sucks and compresses the air, and the compressed air is supplied to the intercooler 2
It is cooled at 0, 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 filling efficiency to perform supercharging. And
In the single turbo mode in which only the primary turbocharger 40 operates in this single turbo mode,
As shown in the output characteristic of 1., a torque curve TQ1 at the time of a single turbo with a high axial torque in the low and medium rotational speed range is obtained.

Next, the single-to-twin switching control will be described. If it is determined in step S5 that Tp ≧ Tp2, that is, if the current operating region has shifted from the single turbo region to the twin turbo region (see FIG. 10), the process branches to step S30 and only the primary turbocharger 40 operates. The single-to-twin switching control for switching from the single turbo state to the twin turbo state in which both turbochargers 40 and 50 are operated is executed.

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. In addition, each switching solenoid valve SO
L. When 1 and 3 are OFF, steps S31 and S33
Switch solenoid valve SOL. Turn on 1 and 3 and proceed 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,
Due to the positive pressure and the biasing force of the spring, the valve is immediately closed as shown in FIG. Further, the exhaust control valve 53 is the first exhaust control valve switching solenoid valve SOL. When 3 is turned on, positive pressure is introduced into the positive pressure chamber 54a of the actuator 54 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 feedback control by the exhaust control valve 53 is stopped and the exhaust control valve small open control duty solenoid. The valve 75 is fully closed, and the positive pressure via 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 75, whereby the opening degree of the exhaust control valve 53 is increased. 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 of the blower 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 value of the differential pressure initial value reading flag FINI is referred to. When FINI = 0, the process proceeds to step S35, and when FINI = 1, step S37.
Jump to.

When the routine is executed for the first time after shifting to the single-to-twin switching control, the routine proceeds to step S35 because FINI = 0, and the upstream pressure PU and the downstream pressure PD of the intake control valve 55 detected by the differential pressure sensor 80 are detected. Differential pressure DPS (=
(PU-PD) is read and set as the differential pressure initial value DPSINI. After setting the differential pressure initial value DPSINI, the process proceeds to step S36, and the differential pressure initial value reading flag FIN is set.
Set I and proceed to step S37.

At step S37, 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 S48, and SOL. When 4 = OFF,
Since the intake control valve full-open control has not yet been executed, the process proceeds to step S38, and the value of the reduction rate calculation flag F3 is referred to. The reduction rate calculation flag F3 is set after calculating the differential pressure reduction rate per unit time after shifting from the single turbo mode to the single → twin switching control. Single →
After shifting to the twin switching control, when the calculation of the differential pressure reduction rate is not yet performed, the process proceeds to step S39 by F = 3, and the twin turbo region continuation time count value C1 representing the continuation time after shifting to the twin turbo region is set. , And a preset value T1 preset for giving a unit time for the differential pressure reduction rate calculation, and when C1 <T1, step S4
After jumping to 5 and counting up the twin turbo region continuation time count value C1, the routine exits and C1 ≧
When it is T1, the routine proceeds to step S40, where the differential pressure initial value DPSINI is read and subtracted from the current differential pressure DPS to calculate the differential pressure decrease rate ΔDPS given by the set value T1 per unit time.

Then, the process proceeds to step S41, the exhaust control valve open delay time setting table is referred to with interpolation calculation based on the differential pressure reduction rate ΔDPS, and the full open control of the exhaust control valve 53 after shifting to the single-to-twin switching control is performed. An exhaust control valve opening delay time T2 that gives a first set time for setting the timing (turning the second exhaust control valve switching solenoid valve SOL.4 from OFF to ON) is set, and the differential pressure is reduced in step S42. The intake control valve open delay time setting table is referred to with interpolation calculation based on the rate ΔDPS, and after the exhaust control valve 53 is fully opened, the intake control valve 55 is opened (intake control valve switching solenoid valve SOL. The intake control valve opening delay time T3 that gives the second set time for determining the start timing is set. Since the intake control valve opening control is performed after the exhaust control valve fully opening control, the intake control valve opening delay time T3 is naturally larger than the exhaust control valve opening delay time T2 at the same differential pressure reduction rate.
Is set longer.

FIG. 9B shows a conceptual diagram of the exhaust control valve open delay time setting table and the intake control valve open delay time setting table. As shown in the figure, the differential pressure decrease rate ΔDP
The larger S is, the shorter the exhaust control valve opening delay time T2 and the intake control valve opening delay time T3 are.
Is fully opened and the intake control valve 55 is opened, that is, the timing of switching to the twin turbo mode is advanced. Here, the differential pressure decrease rate ΔDP
S represents the degree of engine load, and when the single-to-twin switching control is performed in the engine high load operation state, the supercharging pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and its opening degree is increased. Upstream pressure PU of control valve 55
Immediately increases, and the differential pressure decrease rate ΔDPS increases. Therefore, when it is determined that the differential pressure decrease rate ΔDPS is large and the single-to-twin switching control is performed in the engine high load operating state (corresponding to, for example, sudden acceleration, racing, etc.), the exhaust control valve open delay time T2. Is shortened and the exhaust control valve 53 is fully opened, so that the exhaust gas is dispersed also on the secondary turbocharger 50 side, and the primary turbocharger is caused by a rapid increase in the exhaust flow rate and the exhaust pressure due to the high load operation. It prevents the occurrence of surging due to 40 becoming an over-rotation state and reaching the critical number of revolutions, and reduces the heat load to improve the reliability of the primary turbocharger 40. Along with this, the intake control valve opening delay time T3 is also set short to advance the opening timing of the intake control valve 55,
The upstream pressure PU of the intake control valve 55, that is, the abnormal increase in the blower pressure due to the secondary turbocharger 50 is prevented, the surging of the secondary turbocharger 50 is prevented, and the reliability of the secondary turbocharger 50 is improved. To do.

Further, as the load is smaller and the differential pressure reduction rate ΔDPS is smaller, the exhaust control valve opening delay time T2 and the intake control valve opening delay time T3 are set longer, so that the preliminary rotational speed of the secondary turbocharger 50 is increased. After sufficiently raising the intake control valve 55, the primary turbocharger 4 is opened.
Only when the turbocharger is 0, the turbocharger 40, 50 is prevented from generating a torque shock due to a temporary decrease in supercharging pressure when switching from the turbocharger 40, 50 to the twin turbo state.

After setting these delay times T2 and T3, the process proceeds to step S43, the reduction rate calculation flag F3 is set, and a step for counting the twin turbo region continuation time after each delay time T2 and T3 is set. After the twin turbo region continuation time count value C1 is cleared in S44, the twin turbo region continuation time count value C1 is counted up in step S45 and the routine exits.

After that, if it is determined in step S38 that F3 = 1 by setting the reduction rate calculation flag F3, the process proceeds to step S46, and the twin turbo region continuation time count value C1 and the exhaust control valve opening delay time T2 are set. After comparing and calculating the differential pressure reduction rate, the exhaust control valve opening delay time T2
To determine if has passed. When C1 <T2, the twin-turbo region duration time count value C1 is incremented in step S45 to exit the routine, and C
When the exhaust control valve opening delay time T2 elapses after the differential pressure reduction rate is calculated with 1 ≧ T2, the routine proceeds to step S47, where the second exhaust control valve switching solenoid valve SOL. 4 is turned on to fully open the exhaust control valve 53, the twin turbo region continuation time count value C1 is incremented in step S45, and the routine exits. Therefore, the second exhaust control valve switching solenoid valve SOL. Exhaust control valve 53 by turning on 4
Is fully opened, the rotation speed of the secondary turbocharger 50 is increased, and the blower pressure between the blower 50b and the intake control valve 55 is also increased. As shown in FIG. The differential pressure DPS between the pressure PU and the downstream pressure PD increases.

On the other hand, the second exhaust control valve switching solenoid valve SOL. When the control flow goes from step S47 to step S48 when 4 is turned on, the twin turbo region continuation time count value C1 is compared with the intake control valve opening delay time T3, and when C1 <T3, the intake control valve opening start timing is set. It is determined that the count has not reached, and the count value C is determined in step S45.
Count up 1 and exit the routine. Also, C1
When ≧ T3, it is determined that the opening timing of the intake control valve 55 has been reached, and the routine proceeds to step S49, where the intake control valve switching solenoid valve SOL. 2 is turned on, and the intake control valve 5
5 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 S50, 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.

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 supercharging pressure relief valve 57 is closed and the exhaust control valve 53 is opened, and thereafter, the preliminary rotation speed of the secondary turbocharger 50. Is given by the exhaust control valve opening delay time T2, the preliminary rotation speed of the secondary turbocharger 50 is increased, and the exhaust control valve 53 is fully opened after the delay time T2 has elapsed. Then, the boost pressure (blower pressure) by the secondary turbocharger 50 between the blower 50b of the secondary turbocharger 50 and the intake control valve 55 rises, the differential pressure DPS rises, and after the exhaust control valve fully open control, The delay time T3 is compensated by compensating the operation delay time until the exhaust control valve 53 is fully opened by the intake control valve open delay time T3 and the time until the upstream pressure PU and the downstream pressure PD of the intake control valve 55 become substantially equal. When the time has elapsed, the intake control valve 55 is fully opened. As a result, the switching from the single turbo state in which only the primary turbocharger 40 is supercharged to the twin turbo state due to the operation of both turbochargers 40 and 50 is smoothly performed, and occurs when switching to the twin turbo state. The occurrence of torque shock due to a temporary decrease in boost pressure is prevented.

Further, the exhaust control valve opening delay time T2
And the intake control valve opening delay time T3 are set based on the differential pressure reduction rate ΔDPS immediately after the transition from the single turbo mode to the single → twin switching control, and the differential pressure reduction rate ΔD
The higher the engine operating state when the PS is large and the mode is switched to the single-to-twin switching control, the shorter the time period is set. As a result, as shown by the broken line in FIG.
Exhaust control valve switching solenoid valve SOL. 4 is turned on to accelerate the timing of fully opening the exhaust control valve 53 and to disperse the exhaust gas to the secondary turbocharger 50 side as well, so that the primary turbocharger 40 is rapidly increased due to the rapid increase in the exhaust flow rate and the exhaust pressure accompanying the high load operation. Becomes a super-rotation state and reaches a critical rotational speed to cause surging, so that damage to the primary turbocharger 40 is reliably prevented. Further, at this time, the intake control valve switching solenoid valve SOL. Two
When the intake control valve 55 is opened, the timing of opening the intake control valve 55 is also advanced, and the upstream pressure PU of the intake control valve 55, that is, the abnormal increase in the blower pressure due to the secondary turbocharger 50 is prevented and the surging of the secondary turbocharger 50 is prevented. Is prevented, and the reliability of the secondary turbocharger 50 is also improved. Further, at this time, since the twin turbo state is quickly switched, as shown in the output characteristic diagram of FIG. 12, 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 is provided. By switching from the single turbo state to an early stage, it is possible to simultaneously obtain a good acceleration performance by adapting to the driver's acceleration request.

As shown by the solid line in FIG. 13, the smaller the differential pressure decrease rate ΔDPS and the smaller the load, the longer the exhaust control valve open delay time T2 and the intake control valve open delay time T3 are set, and the secondary turbo After sufficiently increasing the preliminary rotation speed of the supercharger 50, open the exhaust control valve 53,
After that, when the upstream pressure PU of the intake control valve 55, that is, the blower pressure by the secondary turbocharger 50 is sufficiently increased and the upstream pressure PU of the intake control valve 55 and the downstream pressure PD become substantially equal, the intake control valve 55. Since the supercharge from the secondary turbocharger 50 is started by opening the valve, the occurrence of torque shock due to a temporary decrease in supercharging pressure occurring at the time of switching to the twin turbo state is effectively and reliably prevented. .

Next, the twin turbo mode will be described. When the twin turbo mode determination flag F1 is set by the termination of the single-to-twin switching control, or when the twin turbo mode was set at the time of the previous routine execution, when the current routine is executed, the process branches from step S1 to step S60 by F1 = 1. .

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. 10), and the process proceeds to step S61. The twin-to-single atmospheric pressure correction coefficient KSGLALT is set by referring to the atmospheric pressure correction coefficient table with interpolation calculation based on the atmospheric pressure (absolute pressure value) ALT. As shown in FIG. 9A, in the atmospheric pressure correction coefficient table, the standard atmospheric pressure or higher is set to 1.0, and the atmospheric pressure ALT decreases as the atmospheric pressure ALT decreases, similar to the single-to-twin atmospheric pressure correction coefficient KTWNALT. , Small value twin → single atmospheric pressure correction coefficient KSG
LALT is stored.

Then, in step S62, the twin
The single-switching determination basic value Tp1B is corrected by the twin → single atmospheric pressure correction coefficient KSGALT to set the twin → single switching determination value Tp1 for determining the switching from the twin turbo mode to the single turbo mode.

Twin-to-single atmospheric pressure correction coefficient KS
Since the GLALT is set to a smaller value as the atmospheric pressure ALT decreases, the twin → single switching determination line L1 based on 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-load 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, regardless of the change in atmospheric pressure ALT, it is possible to set a proper hysteresis that is almost constant at all times, and control hunting for switching the turbocharger operating number can be effectively and reliably prevented. The driving feeling associated with the switching to the single turbo state can be made substantially the same regardless of the change in the atmospheric pressure ALT.

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 state is in the twin turbo region, so the determination value search is performed in step S64. After the flag F4 is cleared and the single turbo region continuation time count value C2 for counting the elapsed time after shifting to the single turbo region is cleared in step S65, the process jumps to step S71, and steps S71 to S74.
Changeover solenoid valve for boost pressure relief valve SOL. 1, intake control valve switching solenoid valve SOL. 2, first and second exhaust control valve switching solenoid valves SOL. 3, 4 are turned on, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 53 are both fully opened, and the twin turbo mode determination flag F1 is set in step S75. After returning to S20 and clearing the twin turbo region duration time count value C1, the routine exits.

In the twin turbo mode, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 5 are closed.
By fully opening 3, the secondary turbo supercharger 50 in addition to the primary turbo supercharger 40 is in full-scale operation, and the turbocharger 40, 50 is in a twin turbo state due to supercharging operation. Compressed air due to supercharging of 50 is supplied to the intake system, and as shown in the output characteristic of FIG. 12, 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 <Tp
1, that is, if it is determined that the current operating region has shifted to the single turbo region (see FIG. 10), step S66
Then, the process proceeds to step S4, refers to the value of the judgment value search flag F4, and F4 = 0
In the case of, it progresses to step S67, and in the case of F4 = 1, it 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).
54). Therefore, after Tp <Tp1, when executing the first routine, the process proceeds to step S57, and the single turbo region continuation time determination value T4 is set by referring to the single turbo region continuation time determination value table with interpolation calculation based on the engine load Tp. . The set value T4 is a reference value for switching to the single turbo mode in which only the primary turbocharger 40 operates after a predetermined time has elapsed after the engine operating state transitions from the twin turbo region to the single turbo region.

FIG. 9C shows a conceptual diagram of the single turbo region continuation time judgment value table. Single turbo region continuation time determination value T4 set according to the engine load Tp
Is set to, for example, 2.3 sec at maximum and 0.6 sec at minimum, and is set to a smaller value as the engine load Tp is larger and the load is higher. As a result, after the engine operating state has changed from the twin-turbo region to the single-turbo region, the time from switching from the twin-turbo mode to the single-turbo mode is faster as the engine load is higher, and in the part where the axial torque is low in the twin-turbo condition. Driving is prevented and re-acceleration is improved.

Next, after the judgment value search flag F4 is set in step S68, the process proceeds to step S69. Then, in step S69, the single turbo region duration time count value C2 is counted up, and then in step S70, the determination value T4 and the count value C2 are compared, and C2 <T4
If so, the routine proceeds to step S71, and the twin turbo mode is maintained. On the other hand, when C2 ≧ T4, the process proceeds to step S76, the count value C2 is cleared, the process returns to step S10, and the twin turbo mode is switched to the single turbo mode. As a result, each switching solenoid valve SOL. 1 to 4 are turned off, and the boost pressure relief valve 57
Is opened and both the intake control valve 55 and the exhaust control valve 53 are closed, so that from the twin turbo state in which both turbochargers 40, 50 are operating to the single turbo state in which only the primary turbocharger 40 is operating. Switch to.

The switching state at this time is shown in a time chart of FIG. As described above, the switching from the twin turbo mode to the single turbo mode is performed when the engine operating range is changed from the twin turbo range to the single turbo range (Tp <Tp1) and then the state continues for a set time (C2 ≧ T4). As a result, unnecessary switching of the supercharger due to a temporary decrease in the engine speed N due to a shift change or the like is prevented.

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.

[0093]

As described above, according to the present invention, the engine operating region shifts from the single turbo region to the twin turbo region side with the single-to-twin switching determination line as a boundary, and only the primary turbocharger operates. When switching from the turbo state to the twin turbo state in which both turbochargers are operating, immediately after the engine operating region shifts to the twin turbo region side, the differential pressure reduction rate between the upstream pressure and the downstream pressure of the intake control valve is calculated, The larger the differential pressure decrease rate, the shorter the first set time for giving the exhaust control valve full opening timing and the second set time for giving the intake control valve opening timing.
The larger the differential pressure reduction rate between the upstream pressure and the downstream pressure of the intake control valve is and the higher the engine operating condition is, the earlier the exhaust control valve is fully opened and the exhaust gas introduced into the primary turbocharger is immediately secondary. Dispersed in the turbocharger, the primary turbocharger is in an over-rotation state due to a rapid increase in exhaust pressure and exhaust flow rate, which prevents the occurrence of surging due to reaching a critical speed and reduces the heat load,
Damage is reliably prevented and reliability is improved. At this time, the opening timing of the intake control valve is also advanced to prevent surging of the secondary turbocharger due to an abnormal rise in blower pressure due to the secondary turbocharger, and the reliability of the secondary turbocharger is also improved. To do. Further, at this time, since the single turbo state is quickly switched to the twin turbo state, it is possible to obtain a good acceleration performance by adapting to the acceleration request of the driver.

When the differential pressure reduction rate is small and the load is low, the first set time and the second set time are set long, and the exhaust control valve is set after the preliminary rotational speed of the secondary turbocharger has sufficiently increased. Is fully opened, and then the intake control valve is opened to switch to the twin-turbo state when the blower pressure from the secondary turbocharger has risen sufficiently, so the temporary supercharging that occurs when switching to the twin-turbo state. The occurrence of torque shock due to pressure drop is prevented.

Further, since the differential pressure decrease rate also takes into account the supercharging pressure increase rate, the intake control valve is fully opened at the optimum timing corresponding to the engine operating state, and the intake control valve is opened to the twin turbo state. Since the switching is performed, it is possible to obtain the acceleration responsiveness adapted to the driving state at that time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an engine with a supercharger according to the present invention.

FIG. 2 is a circuit diagram of a control device.

FIG. 3 is a flowchart showing a turbo switching control routine.

FIG. 4 is a flowchart showing a turbo switching control routine.

FIG. 5 is a flowchart showing a turbo switching control routine.

FIG. 6 is a flowchart showing a turbo switching control routine.

FIG. 7 is a flowchart showing a turbo switching control routine.

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

9A is an atmospheric pressure correction coefficient table, FIG. 9B is a setting table of exhaust control valve open delay time and intake control valve open delay time, and FIG. 9C is a single turbo region continuation time judgment value table. It is a figure.

FIG. 10 is an explanatory diagram of a turbo switching determination value table.

FIG. 11 is an explanatory diagram showing an atmospheric pressure correction state of each determination value.

FIG. 12 is an explanatory diagram showing engine output characteristics during single turbo and during twin turbo.

FIG. 13 is a time chart showing a switching state from the single turbo mode to the twin turbo mode.

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

[Explanation of symbols]

 40 Primary turbo supercharger 50 Secondary turbo supercharger 50a Turbine 50b Blower 53 Exhaust control valve 55 Intake control valve 100 Electronic control unit (ECU) Tp2 Single → Twin switching determination value L2 Single → Twin switching determination line T2 Exhaust control valve open Delay time (first set time) T3 Intake control valve open delay time (second set time) ΔDPS Differential pressure reduction rate

Claims (1)

[Claims] 1. A primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine,
An intake control valve is installed in the intake system connected downstream of the blower of the secondary turbocharger, and an exhaust control valve is installed in the exhaust system connected upstream of the turbine, and both control valves are fully opened in the high speed range. Both the turbochargers are supercharged together.Twin turbo region and low speed region close the intake control valve and close or slightly open the exhaust control valve to supercharge only the primary turbocharger. The engine operating region is divided into a single turbo region, and a single → twin switching determination line set based on the engine operating region is set based on the single → twin switching determination value. The exhaust control valve to a small open or to maintain a small open, and the exhaust control valve is fully opened after the first set time, and then to the second set time. In the control method of the engine with a supercharger, in which the intake control valve is opened after the overage and only the primary turbocharger is switched from the supercharged single turbo state to the dual turbocharger operated twin turbo state, Immediately after shifting from the single turbo region to the twin turbo region with the single-to-twin switching determination line as a boundary, the differential pressure reduction rate between the upstream pressure and the downstream pressure of the intake control valve is calculated, and based on the differential pressure reduction rate, A method for controlling an engine with a supercharger, wherein the first set time and the second set time are set shorter as the differential pressure reduction rate is larger.