JPH07217476A - Air-fuel ratio control method for internal combustion engine having turbosupercharger - Google Patents

Abstract

PURPOSE:To prevent a torque shock from occurring by restraining a supercharged pressure drop appearing immediately after the start of the substantial supercharging operation of a secondary turbosupercharger through an opened intake control valve. CONSTITUTION:An intake control valve is judged to be open at the time of changing a supercharging process on the operation of a primary turbosupercharger to another supercharging process on the operation of both turbosuperchargers, on the basis of the on/of state of a selector solenoid valve SOL.2 (at a step 70) to control the intake control valve. Then, a correction factor KTWIN for selecting twin-turbo operation is reset (step 72), using an initial value KTWININI synchronously with the opening operation of the intake control valve. Furthermore, fuel injection pulse width is forcibly corrected for reduction on the basis of the factor KTWIN, thereby forcibly correcting an air-fuel ratio for the lean side. Consequently, a drop in supercharging pressure resulting from the start of the substantial supercharging operation of the secondary turbosupercharger can be restrained, and the occurrence of a torque shock can be eliminated. Thereafter, the factor KTWIN is gradually reduced to zero (step 77) and the air-fuel ratio is gradually restored from lean state to normal state. As a result, continuity from the lean state of the air-fuel ratio to the normal state becomes smooth.

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 the turbocharger is based on an operating state. The method for controlling the air-fuel ratio of the engine with a supercharger, which switches the number of actuated fuel cells, is described in detail when switching from the supercharging operation of only the primary turbocharger to the supercharging operation of both turbochargers. The present invention relates to an air-fuel ratio control method for an engine with a supercharger, which prevents the occurrence of torque shock due to a decrease in supercharging pressure.

[0002]

2. Description of the Related Art Primary intake and exhaust systems for an engine
The turbocharger and the secondary turbocharger are arranged in parallel,
An intake control valve and an exhaust control valve are installed in the intake and exhaust systems connected to the secondary turbocharger, respectively, and both control valves are closed when the engine operating range is in the low speed range. Output from low speed range to high speed range by supercharging only turbocharger and opening both control valves in high speed range to operate both turbochargers together. There is known a supercharged engine capable of improving performance.

In this type of engine with a supercharger, as shown in Japanese Patent Laid-Open No. 3-260328, the supercharging pressure is temporarily reduced with the start of the supercharging operation of the secondary turbocharger. In order to suppress the occurrence of torque shock due to the
Prior to switching the secondary turbocharger to the supercharging operation, open the exhaust control valve (exhaust gas switching valve) slightly to pre-rotate the secondary turbocharger, and At the time of switching to the supercharging operation of the feeder, first fully open the exhaust control valve to increase the rotation speed of the secondary turbocharger to increase the supercharging pressure by the secondary turbocharger, After the exhaust control valve is fully opened, a predetermined time has elapsed, the intake control valve (intake switching valve) is opened, and in addition to the supercharging operation of the primary turbocharger, the secondary turbocharger is fully activated. The supercharger is activated.

However, even by the switching control shown in this prior art example, immediately after the start of the full-scale supercharging operation of the secondary turbocharger by opening the intake control valve, the secondary turbocharger operates. It is unavoidable that the boost pressure is temporarily reduced due to the loss, and a torque shock occurs due to the reduction of the boost pressure.

In Japanese Patent Laid-Open No. 2-238142, the air-fuel ratio associated with the opening of the intake control valve is corrected by increasing and correcting the fuel supply amount in synchronization with the opening of the intake control valve (intake cut valve). There is disclosed a technique for preventing the lean air-fuel ratio and suppressing the air-fuel ratio fluctuation.

[0006]

However, as in the above-mentioned prior art example, the secondary type valve is opened by opening the intake control valve.
If the fuel supply amount is increased and corrected in synchronization with the full-scale supercharging operation of the turbocharger, the air-fuel ratio fluctuation can be suppressed,
On the other hand, the amount of fuel adhering to the wall surface increases, and the amount of heat of vaporization due to fuel vaporization increases, which lowers the intake port wall surface temperature and the combustion chamber temperature and reduces the exhaust gas temperature, leading to a reduction in exhaust energy. There is an inconvenience that the supercharging pressure is lowered due to the reduction of the supercharger efficiency, a stronger torque shock is generated, and the driver is uncomfortable.

The present invention has been made in view of the above circumstances, and suppresses the reduction of the supercharging pressure immediately after the start of the full-scale supercharging operation of the secondary turbocharger by opening the intake control valve. An object of the present invention is to provide an air-fuel ratio control method for a supercharged engine that can prevent the occurrence of torque shock.

[0008]

In order to achieve the above object, the present invention provides a primary engine for intake and exhaust systems of an engine.
The turbocharger and the secondary turbocharger are arranged in parallel,
When the engine operating range is in the low speed range, the secondary
Close both the intake control valve and the exhaust control valve, which are connected to the turbocharger, respectively, in the intake and exhaust systems, or open only the exhaust control valve to open the primary turbocharger only. In the air-fuel ratio control method for an engine with a supercharger, in which supercharging operation is performed and both control valves are fully opened to supercharge both turbochargers when in a high speed range. When switching from supercharging operation of only the turbocharger to supercharging operation of both turbochargers, the fuel supply amount is reduced and the air-fuel ratio is lean corrected in synchronization with the opening of the intake control valve. After that, the air-fuel ratio is gradually returned to the normal air-fuel ratio.

[0009]

In the air-fuel ratio control method for the supercharged engine,
At the start of full-scale supercharging operation of the secondary turbocharger by opening the intake control valve from the supercharging operation of only the primary turbocharger, the fuel supply amount is reduced and the air-fuel ratio is forced. Is corrected to lean. As a result, the amount of fuel adhering to the wall surface is reduced, and the amount of heat of vaporization associated with the vaporization of fuel is correspondingly reduced, and the temperature of the intake port wall surface and the temperature of the combustion chamber are increased to raise the exhaust gas temperature.

As a result, the exhaust energy is increased, the operating efficiency of the supercharger is improved, and the decrease in the supercharging pressure due to the start of the supercharging operation of the secondary turbocharger is suppressed.

After that, the air-fuel ratio is gradually returned from the lean state to the normal air-fuel ratio. As a result, the air-fuel ratio lean state is smoothly connected to the normal air-fuel ratio.

[0012]

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. 29, 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). The crankcase 2 has left and right banks 3 and 4, a combustion chamber 5, an intake port 6, and an exhaust port. -, A spark plug 8, a valve operating 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 turbocharger 40 and a secondary turbocharger 50 are provided respectively. As an exhaust system, a common exhaust pipe 10 from both the left and right banks 3 and 4 is provided for both turbochargers 4.
The exhaust pipes 11 connected to the turbines 40a and 50a of 0 and 50 are connected to one exhaust pipe 12 respectively.
To the catalyst converter 13 and the muffler 14.

The primary turbocharger 40 is a small-capacity low-speed type having a large supercharging ability in the low and medium speed range, while the secondary turbocharger 50 is in the medium and high speed range. It is a large-capacity, high-speed type with a large supercharging capacity. Therefore, since the capacity of the primary turbocharger 40 is smaller, 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 compressors 4 of both turbochargers 40 and 50, respectively.
0b, 50b, the compressor 40b, 5
The intake pipes 18 and 19 from 0b are connected to the intercooler 20. The intercooler 20 communicates with a chamber 22 through a throttle body 27 having a throttle valve 21, and the chamber 22 is connected to the intake manifold 2.
The intake port 6 of each cylinder of the left and right banks 3 and 4 communicates with each other through 3. Further, as an idle control system, a bypass passage 24 that bypasses the throttle valve 21 and connects the intake pipe 16 and the intake manifold 23 immediately downstream of the air cleaner 15 is opened by an idle control valve (ISCV) and a negative pressure. A check valve 26 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 in which an injector 30 is arranged immediately upstream of the intake port 6 in each of the cylinders 3 and has 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 adjusts the intake pressure in the intake manifold 23, so that the fuel pressure supplied to the injector 30 is constantly maintained at a constant height with respect to the intake pressure. It is possible to control the fuel injection amount by driving the injector 30 by the pulse width of the injection signal from the electronic control unit 100 described later. Further, as an ignition system, an ignition signal from an igniter 36 is connected to an ignition coil 8a that is continuously provided for each ignition plug 8 of each cylinder.

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

The primary turbocharger 40 uses the energy of the exhaust gas introduced into 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 waist gate valve 41 having a diaphragm type actuator 42 is provided on the side of the turbine 40a. A control pressure passage 44 directly downstream of the compressor 40b communicates with the pressure chamber of the actuator 42 through an orifice 48 so that the waist gate valve 41 can be opened with good response when the supercharging pressure rises above a set value. Be communicated to. Further, the control pressure passage 44 communicates with a duty solenoid valve D.SOL.1 which leaks the supercharging pressure to the upstream side of the compressor 40b, and is controlled by the duty solenoid valve D.SOL.1. The control pressure is generated and acts on the actuator 42 to change the opening of the waist gate valve 41 to control the supercharging pressure. Here, the duty solenoid valve D.SO
L.1 is operated by a duty signal from the electronic control unit 100, which will be described later. When the duty ratio of the duty signal is small, L.1 increases the opening degree of the waist gate valve 41 with a high control pressure. As the supply pressure decreases and the duty ratio increases, the control pressure decreases due to an increase in the amount of leak, and the opening degree of the waist gate valve 41 is reduced to increase the supercharging pressure.

On the other hand, in order to prevent a decrease in compressor rotation and the occurrence of intake noise when the throttle valve is rapidly closed, 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. A bypass passage 46 is communicated between and. Then, the air bypass valve 45 is introduced into the bypass passage 46 by introducing a manifold negative pressure by the passage 47 when the throttle valve is rapidly closed, so that the pressurized air trapped downstream of the compressor 40b is quickly leaked. It is provided.

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

Similarly, the secondary turbocharger 50 is one in which the turbine 50a and the compressor 50b are rotationally driven by the exhaust air to supercharge, and the secondary waist having the actuator 52 on the turbine 50a side. A gate valve 51 is provided. Further, the exhaust pipe 10 upstream of the turbine 50a is provided with a downstream open type exhaust control valve 53 having a diaphragm type actuator 54, and a similar actuator 56 is provided downstream of the compressor 50b. A butterfly type intake control 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 operation system of each of these valves will be described.

First, the surge tank 60 of the negative pressure source is provided with 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 for controlling the exhaust control valve 53 to open slightly.
SOL.2 and secondary waist gate valve switching solenoid valve SO for opening and closing the secondary waist gate 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.
A positive pressure or atmospheric pressure or the like from a, 64b is selected and guided to the actuator side by the control pressure passages 70a to 74a, and the secondary waist gate valve 51, the boost pressure relief valve 57, each. The control valves 55 and 53 are operated. Also, the du
The tee 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 SOL. For the supercharging pressure relief valve. 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 to resist the biasing force of the spring. The boost pressure relief valve 57 is opened. Further, when turned on, the negative pressure passage 63 side is closed and the positive pressure passage 64a side is opened conversely to introduce positive pressure into the pressure chamber of the supercharging pressure relief valve 57, thereby increasing the supercharging pressure relief valve 57. Close.

Intake control valve switching solenoid valve SOL. Two
Is turned off, the atmospheric port is closed to close the negative pressure passage 63.
Side is opened and the actuator 5 is opened through 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
When it is N, the negative pressure passage 63 side is closed and the atmospheric port is opened to introduce the atmospheric pressure into the pressure chamber of the actuator 56, thereby opening the intake control valve 55 by the urging force of the spring in the pressure chamber.

Switching solenoid valve for secondary waist gate 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. The switching solenoid valve SOL. When W is turned off, the passage 65 communicating with the upstream side of the intake control valve 55 is closed to open the atmospheric port, and atmospheric pressure is introduced into the actuator 52 via the control pressure passage 70a, thereby actuating the actuator. The secondary waist gate valve 51 is closed by the urging force of a spring arranged in the switch 52. Further, when it is ON, the atmosphere port is closed to open the passage 65 side, and the supercharging pressure downstream of the secondary turbocharger 50 when both turbochargers 40 and 50 are operating is guided to the actuator 52. Then, the secondary waist gate valve 51 is opened according to this supercharging pressure, and when using regular gasoline, the supercharging pressure is relatively reduced 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 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 to open the atmosphere port, and the second exhaust control valve switching solenoid valve SOL. 4 is a negative pressure passage 63
By closing the side and opening the air port, the actuator 5
Both chambers 54a and 54b of No. 4 are opened to the atmosphere, and the negative pressure chamber 54b
The exhaust control valve 53 is driven by the urging force of the spring installed in the
Will be fully closed. Further, both switching solenoid valves SOL. 3,4
When both are ON, the atmosphere ports are closed and the first exhaust control valve switching solenoid valve SOL. 3 is a positive pressure passage 6
4b side is opened and the second exhaust control valve switching solenoid valve S
OL. 4 is an actuator by opening the negative pressure passage 63 side.
A positive pressure is introduced into the positive pressure chamber 54a and a negative pressure is introduced into the negative pressure chamber 54b, and the exhaust control valve 53 is fully opened 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 17 and the downstream side of the orifice 67.
A leak passage 66 is communicated with a, and the above-mentioned duty solenoid valve for exhaust control valve small opening control is communicated with this leak passage 66.
D.SOL.2 is provided. The first exhaust control valve switching solenoid valve SOL. When only 3 is ON, 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 D.SOL.2
Thus, the positive pressure is leaked and the exhaust control valve 53 is opened slightly. Here, when the duty ratio in the duty signal from the electronic control unit 100 is large, the duty solenoid valve D.SOL.2 produces a positive pressure acting on the positive pressure chamber 54a due to an increase in the leak amount. As the duty ratio decreases and the opening degree of the exhaust control valve 53 decreases, and as the duty ratio decreases, the leak amount is reduced to maintain the positive pressure high and the opening degree of the exhaust control valve 53 increases. When the engine operating region is in the predetermined exhaust control valve small opening control region under the single turbo mode in which only the primary turbocharger 40 is supercharged, the duty solenoid valve D.SOL The supercharging pressure is feedback controlled by the opening degree of the exhaust control valve 53 by .2, and the secondary control turbocharger 50 is opened by the small opening of the exhaust control valve 53 accompanying the supercharging pressure control.
The secondary turbocharger 50 is preliminarily rotated by introducing exhaust gas into the turbine 50a.

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 provided with a switching solenoid valve 76 so that an intake pipe pressure (intake manifold).
(Intake pressure in the valve 23) and atmospheric pressure are selected and detected.

Further, a knock sensor 82 is attached to the engine body 1, and a water temperature sensor 83 is exposed to a cooling water passage communicating between the left and right banks 3 and 4, and the exhaust pipe 10 is O-shaped.
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 a cam shaft of the valve mechanism 9 is provided with a cam angle sensor 88 for discriminating a cylinder, which is composed of an electromagnetic pickup or the like.

As shown in FIG. 30, the crank rotor 90 has projections 90a, 90b and 90c on its outer periphery.
BTDC θ1, θ of each cylinder (# 1, # 3 and # 2, # 4)
Positions of 2 and θ3 (for example, θ1 = 97 °, θ2 = 65
And θ3 = 10 °). Further, as shown in FIG. 31, the cam rotor 91 is provided with projections 91a, 91b, 91c for cylinder discrimination, and the projection 91a is #.
It is formed at the position of the compression top dead center (ATDC) θ4 of the 3rd and # 4 cylinders (for example, θ4 = 20 °), the protrusion 91b is composed of three protrusions, and the first protrusion is the ATDCθ of the # 1 cylinder.
It is formed at a position of 5 (for example, θ5 = 5 °). Further, the protrusion 91c is composed of two protrusions, and the first protrusion is the position of ATDC θ6 of the # 2 cylinder (for example, θ6 = 20 °).
Is formed in.

The crank angle sensor 87 and the cam angle sensor 88 have the crank rotor 90 and the cam rotor, respectively.
The protrusions formed on the motor 91 are detected as the engine runs, and the crank pulse and the cam pulse are detected by the electronic control unit 1.
Output to 00. Then, in the electronic control unit 100,
The engine speed is calculated from the interval time of the crank pulse (protrusion detected), the ignition timing and the fuel injection start timing are calculated, and the cylinder is discriminated from the input pattern of the crank pulse and the cam pulse (FIG. 10). reference).

Next, the structure 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 to each other through a bus line, and a constant voltage circuit 106 for supplying a predetermined stabilizing power source to each unit. A drive circuit 107 is incorporated.

The constant voltage circuit 106 is an 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 the relay contact of the fuel pump relay 98.

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

The I / O interface 105 is also used.
Various sensors 80 to 88, vehicle speed sensor 8 to the input port of
9, the lead memory connector 92, and the battery 96 are connected. The read memory connector 92 is turned on at the time of inspection in a factory inspection line or dealer, so that the control in the ECU 100 is switched from the normal control mode to the special control mode for checking. The fuel injection amount is set to a value that is reduced compared to the normal control.

An igniter 36 is connected to the output port of the I / O interface 105, and further, an ISCV 25 and an injector 3 are connected via a drive circuit 107.
0, each switching solenoid valve 76, SOL. W, SOL. 1
To 4, duty solenoid valves 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 it is N, 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, the battery voltage, and the like via the I / O interface 105 based on the program stored in the ROM 102, and the RAM 103 and the backup R.
Various control amounts are calculated based on various data stored in the AM 104, fixed data stored in the ROM 102, and table values. Then, the drive circuit 107 turns on the fuel pump relay 98 to energize and drive the fuel pump 31, and the switching solenoid valves 76, SOL. W, SOL. ON for 1-4, OF
Duty the F signal to the duty solenoid valves D.SOL.1,2.
Outputs a tee signal to perform turbocharger switching control and supercharging pressure control, and outputs a drive pulse width signal corresponding to the calculated fuel injection pulse width to the injector 30 of the corresponding cylinder at a predetermined timing. Injection control is performed, and an ignition signal is output to the igniter 36 to perform ignition timing control at a timing corresponding to the calculated ignition timing, and a control signal is output to the ISCV 25 to perform idle speed control and the like.

Next, the fuel injection control (air-fuel ratio control) by the ECU 100 will be described based on the flowcharts shown in FIGS.

First, the cylinder discrimination / engine speed calculation rule
Chin will be described according to the flowchart of FIG.

The cylinder discrimination / engine speed calculation routine is interrupted by the crank pulse output from the crank angle sensor 87 in response to engine operation after the ignition switch 97 is turned on.

First, in step S1, it is discriminated whether the crank pulse input this time is θ1 to θ3 based on the output from the cam angle sensor 88, and in step S2, the input pattern of the crank pulse and the cam pulse is determined. The fuel injection target cylinder is determined.

That is, as shown in the time chart of FIG. 10, for example, if there is a cam pulse input between the input of the previous crank pulse and the input of the current crank pulse, the current crank pulse will be θ1. It can be identified as a pulse, and the next crank pulse to be input is θ
It can be distinguished from 2 pulses. If there is no cam pulse input between the previous and current crank pulse inputs and there is a cam pulse input between the previous and previous crank pulse inputs, the current crank pulse can be identified as the θ2 pulse and the next crank pulse input Can be identified as a θ 3 pulse.
In addition, when there is no cam pulse input between the previous and current time, or between the crank pulse input two times before and the previous time, the crank pulse input this time can be identified as θ3 pulse, and the crank pulse input next time is θ1 pulse. It can be identified as a pulse.

Further, three cam pulses are inputted between the crank pulse input at the previous time and the crank pulse at the current time (θ corresponding to the protrusion 91b).
It is possible to determine that the next compression top dead center is the # 3 cylinder, and the fuel injection target cylinder is the # 4 cylinder, which is two cylinders after the compression top dead center. Also, two cam pulses are input between the previous and current crank pulse inputs (projection 9
It can be determined that the next compression top dead center is the # 4 cylinder and the fuel injection target cylinder is the # 3 cylinder when θ6 pulse corresponding to 1c). Also, one cam pulse is input between the crank pulse input of the previous time and this time (θ4 corresponding to the protrusion 91a.
When the previous compression top dead center determination is the # 4 cylinder, the next compression top dead center is the # 1 cylinder, and the fuel injection cylinder can be determined to be the # 2 cylinder. Similarly, when one cam pulse is input between the crank pulse input of the previous time and this time, and the previous compression top dead center determination is the # 1 cylinder, the next compression top dead center is the # 3 cylinder, and the fuel injection is performed. The target cylinder can be identified as the # 4 cylinder.

In the present embodiment, in a 4-cycle 4-cylinder engine, the combustion process is in the order of cylinders # 1 → # 3 → # 2 → # 4, and the cylinder #i which is the compression top dead center after the output of the cam pulse is #.
If the number of cylinders is 1, the fuel injection target cylinder #i (+2) at this time is the # 2 cylinder, and the next fuel injection target cylinder is the # 4 cylinder at the normal time after the engine is started. On the other hand, the sequential injection is performed once every 720 ° CA (two engine revolutions). Further, as shown in the figure, at the intake timing, the intake valve in each cylinder closes in the early stage of the compression stroke, and immediately before the start of the intake stroke (for example, BT
It is set to open the valve to DC5 ° CA). Therefore, in order to complete the fuel injection immediately before the intake valve of the cylinder starts to open, it is necessary to set the fuel injection timing based on the crank pulse of at least two cylinders before.

Then, in step S3, the pulse input interval period (time) from the previous crank pulse input from the crank angle sensor 87 to the current crank pulse input is detected. This crank pulse input interval period is θ
It is detected when 1 pulse or θ3 pulse is input.
The period (time) Tθ3 · 1 from the input of θ3 pulse to the input of θ1 pulse, or the period (time) Tθ2 · 3 from the input of θ2 pulse to the input of θ3 pulse.

Then, in step S4, the period Tθ3.
The engine speed N is calculated from 1 or Tθ2 · 3, stored as the speed data in a predetermined address of the RAM 103, and the routine is exited. This rotation speed data is read and used at the time of executing each routine described later.

Next, the fuel injection pulse width setting routine will be described with reference to the flowcharts shown in FIGS. This routine for setting the fuel injection pulse width is set for a set time (for example, 10 seconds after the ignition switch 97 is turned on).
It is executed every msec).

When the ECU 100 is turned on by turning on the ignition switch 97, the system is initialized (clearing each flag and count value). First, in step S10, simultaneous injection is performed from the engine speed N and the intake air amount Q. The basic fuel injection pulse width TP for each injection is calculated.

TP ← K × Q / N K; constant After that, in step S11, the operating state of the starter switch is detected, and if it is ON (during cranking), step
Proceed to S12, set the starting increase coefficient KST by the set value CKST (however, CKST> 1.0), and if OFF, set the starting increase coefficient KST to 1.0 (without starting increase correction) in step S13, and then go to step S14. move on. The above-mentioned start-up increasing coefficient KST is used to improve the startability of the engine.
This is to increase the fuel amount only when the engine is started during operation.

In step S14, the mixing ratio allocation coefficient KMR is set based on the basic fuel injection pulse width TP and the engine speed N. This mixing ratio allocation coefficient KMR is stored in ROM1
The table is set by referring to the table stored in a series of addresses 02, and the table is appropriate in each region of the engine operating state specified by the basic fuel injection pulse width TP and the engine speed N. The optimum coefficient obtained in advance by experiments or the like is stored so that the air-fuel ratio can be obtained. With this mixing ratio allocation coefficient KMR, fine controllability can be obtained even when the injector 30 and the intake air amount sensor 86 are deviated from the uniqueness.

Next, in step S15, the throttle opening TH detected by the throttle opening sensor constituting the throttle sensor 85 and the basic fuel injection pulse width T are detected.
Full increase coefficient KFULL based on P and engine speed N
To set. This full increase coefficient KFULL refers to a table preset with the engine speed as a parameter when the throttle opening TH is fully open or when the basic fuel injection pulse width TP indicates a high load condition. To set. As a result, when the throttle is fully opened, or when the engine is in an operating state where output is required, such as when the load is high, the amount of fuel is increased to improve output performance. When the throttle opening TH is other than full open and the engine load is other than high load,
KFULL = 0 is set.

Next, in step S16, the connection state of the read memory connector 92 is detected, and when it is ON (connection), the process proceeds to step S17, and the cooling water temperature TW by the water temperature sensor 83 is detected.
Set the line-off fuel coefficient KPKBA based on
Proceed to S19. The line-off fuel coefficient KPKBA is for preventing the air-fuel ratio from becoming excessively high when the engine is repeatedly restarted. For example, the special control for checking from the normal control mode can be performed by turning on (connecting) the read memory connector at the time of inspection at the line end in the factory, that is, the inspection line or the dealer. Mode
The fuel injection amount is corrected by the line-off fuel coefficient KPKBA, and the smoldering of the spark plug 8 due to the residual fuel when the engine is stopped last time is prevented. Since the air-fuel ratio is controlled to be richer as the cooling water temperature TW is lower and the engine temperature is lower, the line-off fuel coefficient KPKBA is set to increase as the cooling water temperature TW decreases as shown in the figure. ing.

Further, the read memory connector 92 is turned off.
If it is (open), proceed to step S18, set the line-off fuel coefficient KPKBA to 1.0 (no correction), and then step
Proceed to S19.

In step S19, the water temperature increasing coefficient KTW is set based on the cooling water temperature TW. This water temperature increase coefficient KTW
Is for increasing and correcting the fuel injection amount in order to ensure drivability when the engine is in a cold state, and as shown in the figure, is set so that the fuel increase rate increases as the cooling water temperature TW decreases.

Then, the process proceeds to step S20, the post-starting amount increase coefficient KAS is set, and the process proceeds to step S21. The post-starting increase coefficient KAS is for ensuring the stability of the engine speed immediately after the engine is started, and is set to an initial value when the starter switch is ON, as shown in the figure, and After turning the switch from ON to OFF, the set value is decreased each time the routine is executed until it becomes 0.

In step S21, the post-idle increase coefficient K
Set AI. The post-idle increase coefficient KAI is used to prevent rattling when the idle is released, and is set to an initial value based on the cooling water temperature TW when the vehicle speed is below the set speed and when the throttle valve is closed to open. After that, as shown, each time the routine is executed, the set value is decreased until it becomes zero.

After that, the process proceeds to step S22 and the twin
The correction coefficient setting subroutine at the time of switching the robot is executed to set the correction coefficient KTWIN at the time of switching the twin turbo. This twin turbo switching correction coefficient KTWIN is changed from the single turbo state in which only the primary turbocharger 40 is supercharged to the twin turbo state in which both turbochargers 40 and 50 are supercharged. This is for correcting the amount of fuel supply, that is, the amount of fuel injection, by reducing the air-fuel ratio in a lean manner in synchronization with the opening of the intake control valve 55 at the time of switching.

FIG. 4 shows a flowchart of the correction coefficient setting subroutine for twin turbo switching.

In this correction coefficient setting subroutine for twin turbo switching, first, in step S70, the intake control valve switching solenoid valve SOL. 2 is ON or OFF, the switching solenoid valve for intake control valve SOL. Judgment is made by checking the control state for 2. Changeover solenoid valve S for intake control valve
OL. When 2 is ON, atmospheric pressure is introduced into the pressure chamber of the actuator 56, and the intake air arranged downstream of the compressor 50b of the secondary turbocharger 50 by the urging force of the spring installed in the pressure chamber. The control valve 55 opens,
In addition to the supercharging operation of the primary turbocharger 40, a full-scale supercharging operation of the secondary turbocharger 50 is performed. It becomes a bo state. Further, the switching solenoid valve SOL. Two
Is off, a negative pressure is introduced into the pressure chamber of the actuator 56 to resist the biasing force of the spring and the intake control valve 5
5 is closed, the supercharging operation of the secondary turbocharger 50 is stopped, and only the primary turbocharger 40 is in the single turbo state of supercharging operation.

Therefore, the intake control valve switching solenoid valve S
OL. The ON / OFF state of No. 2 is referred to every predetermined time determined by the routine execution interval, so that the intake control valve switching solenoid valve SOL. It is possible to judge whether the intake control valve 55 is opened by turning ON from OFF of 2, that is, whether the supercharging operation of the secondary turbocharger 50 is started.

Then, SOL. 2 = ON, that is, if it is determined that the intake control valve 55 is open, the process proceeds to step S71, and the value of the initial value setting determination flag FKTWIN for determining the initial setting of the twin turbo switching correction coefficient KTWIN is referred to. This initial value setting determination flag FKTWIN is SOL.
When 2 = OFF, it is cleared in step S76 described later,
This is set when the twin turbo switching correction coefficient KTWIN is initialized. Therefore, when FKTWIN = 0 in step S71, the intake control valve switching solenoid valve SOL. 2 is turned from OFF to ON, the first subroutine is executed after the intake control valve 55 is opened, and the supercharging operation of the secondary turbocharger 50 is started by closing and opening the intake control valve 55. Judgment is made, and the processing proceeds to step S72, in which the correction coefficient KTWIN for twin turbo switching is initialized with the initial value KTWININI, the initial value setting discrimination flag FKTWIN is set in step S73, and the routine is exited.

On the other hand, in the above step S71, FKTWIN = 1
In the case of, since the intake control valve 55 is opened and the subroutine is being executed for the second time and thereafter, the routine proceeds to step S74, where the value of the twin turbo switching correction coefficient KTWIN is referred to, and KTWIN> 0.
In the case of, the routine proceeds to step S75, where the correction coefficient KTWIN at the time of twin turbo switching is updated with the value obtained by subtracting the set value TWIN, and the routine is exited. If KTWIN≤0, the routine jumps to step S77 to set the twin turbo switching correction coefficient KTWIN to KTWIN = 0 and exit the routine.

As a result, as shown in FIG. 27, the correction coefficient KTWIN at the time of switching the twin turbo is changed from the supercharging operation of only the primary turbocharger 40 to both the turbochargers 40 and 50.
When the intake control valve 55 is switched to the supercharging operation, it is initialized to the initial value KTWININI in synchronization with the opening of the intake control valve 55, and then becomes 0 until the intake control valve 55 maintains the open state. Each time the subroutine is executed, the set value TWIN is decremented and sequentially updated.

On the other hand, in step S70, the SOL. 2 =
If it is determined to be OFF, that is, if the intake control valve 55 is closed, the process proceeds to step S76, and the initial value setting determination flag FKTWI is set.
After clearing N and setting the twin-turbo switching correction coefficient KTWIN to KTWIN = 0 (no correction) in step S77,
Get out of the chin.

Then, the correction coefficient KTWIN at the time of switching the twin turbo is set by the correction coefficient setting subroutine at the time of switching the twin turbo.
After setting, return to the fuel injection pulse width setting routine,
In step S23, the increase correction coefficient KCO is calculated based on the above coefficients.
EF is calculated from the following formula.

KCOEF ← KFULL + KPKBA × (KTW + KAS +
KAI) -KTWIN The above increase correction coefficient KCOEF is used to calculate the fuel injection amount,
By setting the twin turbo switching correction coefficient KTWIN to a negative term when calculating the increase correction coefficient KCOEF, the secondary turbocharger 50 is opened by opening the intake control valve 55 as shown in FIG. At the start of the full-scale supercharging operation, the fuel injection amount is corrected to be reduced, and the air-fuel ratio is set to the lean side relative to the target normal air-fuel ratio immediately after the supercharging operation of the secondary turbocharger 50 is started. The air-fuel ratio is gradually restored to the normal air-fuel ratio.

Then, in step S24, the twin
In order to limit the air-fuel ratio from excessively leaning (over-burning) by correcting the correction coefficient KTWIN at the time of switching, refer to the value of the above-mentioned increase correction coefficient KCOEF and set KCOEF <0.
If so, the process proceeds to step S25, the increase correction coefficient KCOEF is set to KCOEF = 0, and if KCOEF ≧ 0, no limitation is required, so the process directly jumps to step S26.

In step S26, the starting increase coefficient KS
Based on T, the air-fuel ratio allocation coefficient KMR, and the increase correction coefficient KCOEF, various increase coefficients COEF are calculated from the following equations.

COEF ← KST × (1 + KMR + KCOEF) Next, in step S27, the air-fuel ratio feedback correction coefficient α for making the air-fuel ratio close to the target air-fuel ratio is set based on the output voltage of the O 2 sensor 84, and the basic fuel injection is performed. Learning correction coefficient KBLRC as a correction correction amount for the pulse width TP, a fuel cut coefficient KFC for performing fuel cut when decelerating, idling, above a predetermined vehicle speed, or when the boost pressure is abnormally increased (normally KFC = 1, KFC = 0 when the fuel is cut), the acceleration increase coefficient KACC for compensating the measurement delay of the intake air amount Q by the intake air amount sensor 86 at the time of acceleration and the fuel increase delay associated therewith to ensure the responsiveness.
In addition, the deceleration reduction coefficient KDC for preventing the air-fuel ratio from becoming rich during deceleration is set.

Then, in step S28, the basic fuel injection pulse width TP is set to the above-mentioned various increasing factors COEF and the respective coefficients α, KBLRC, KFC, KACC set in step S27,
Corrected by KDC, an effective pulse width Te suitable for one cylinder, one rotation, one injection is calculated.

Te ← TP × α × (COEF × KBLRC + K
ACC-KDC) × KFC After that, the routine proceeds to step S29, and the control discrimination flag F for normal time is used.
Refer to FU (initial value is 0), if FFU = 0 (previous start control), proceed to step S30, and use normal control discriminating rotation speed as a reference value when discriminating between start control and normal control. NST is a preset value NST1 (for example, 50
0 rpm), and when FFU = 1 (previous normal time control), the process proceeds to step S31, and the normal time control determination rotation speed N
ST is set value NST2 (however, NST1> NST2, for example, 30
0 rpm) and proceed to step S32.

The normal-time control determination flag FFU is set in step S34, which will be described later, during normal-time control, and cleared in step S52, which will be described later, during start-up control. As shown in FIG. By providing the rotation speed NST with hysteresis, control hunting at the time of shifting from the starting injection control to the normal injection control is prevented.

In step S32, the engine speed N is compared with the normal control discrimination speed NST. When N> NST, the routine proceeds to step S33 to execute the normal injection control. When N≤NST, The process branches to step S40 to execute the start-up control.

In the following description, the injection control procedure at the start will be described first, and then the injection control procedure at the normal time will be described.

When the process branches from step S32 to step S40, the starting injection pulse width Ti0 is calculated by adding the effective pulse width Te to the voltage correction pulse width TS set based on the battery voltage for correcting the invalid time. To do.

Ti0 ← Te + TS Then, in step S41, the connection state of the read memory connector 92 is detected, and when OFF, the process proceeds to step S42,
Based on the cooling water temperature TW, refer to the first basic value table with interpolation calculation to set the basic value TCST, and when it is ON,
In step S43, the basic value TCST is set by referring to the second basic value table with interpolation calculation based on the cooling water temperature, and then the process proceeds to step S44.

The basic value TCST is a base value for calculating the cold start pulse width TiST at the time of starting,
As shown in FIG. 9, the lower the cooling water temperature TW, the larger the value set. Also, the basic value TCST stored in the second basic value table selected when the read memory connector 92 shown by the broken line in the figure is ON is the read memory connector shown by the solid line when it is OFF. It is set to a value smaller than the basic value TCST stored in the first basic value table selected at this time. As described above, the read memory connector 92 is turned on (connected) when the engine is repeatedly restarted at the time of inspection on the inspection line of the factory, the dealer, or the like. Is in the OFF (open) state.

Therefore, the read memory connector 92 is turned on.
By doing so, a small basic value TCST based on the second basic value table is selected, and along with this, the fuel depletion correction is similarly performed when the cold start pulse width TiST is calculated.
Smoldering of the spark plug 8 is prevented even when restarting is repeated.

In step S44, the rotation correction coefficient TCSN is set by referring to the table based on the engine speed, and the process proceeds to step S45 to set the time correction coefficient TKCS. As shown in the figure, the time correction coefficient TKCS is fixed at 1.0 for a predetermined time when the starter switch is turned on.
After that, it gradually decreases to 0. Therefore, if the starting injection control is not completed within a predetermined time after the starter switch is turned on, the cold start pulse width TiST set in step S48, which will be described later, gradually decreases thereafter and finally. TiST = 0.

Then, in step S46, the table is referenced with interpolation calculation based on the battery voltage to set the voltage correction coefficient TCSL for compensating the dead time, and the flow proceeds to step S47. The voltage correction coefficient TCSL is
It is set to a large value because the invalid time becomes long.

In step S47, the throttle opening correction coefficient TCS is obtained by referring to the table based on the throttle opening TH.
Set A. The throttle opening correction coefficient TCSA is set to a larger value for increasing correction as the throttle opening TH increases.

Then, in step S48, the basic value TCST is corrected by the correction coefficients TCSN, TKCS, TCSL and TCSA to calculate the cold start pulse width TiST.

TiST ← TCST × TCSN × TKCS × TCSL × TCSA After that, the routine proceeds to step S49, where the starting injection pulse width Ti0 is compared with the cold start pulse width TiST and T
When i0 ≧ TiST, the routine proceeds to step S50, where the fuel injection pulse width Ti is set to the starting fuel injection pulse width Ti0, and T
When iST <Ti0, the routine proceeds to step S51, where the fuel injection pulse width Ti is set by the cold start pulse width TiST, then at step S52, the normal time control determination flag FFU is cleared and the routine returns to step S35, and the fuel injection is performed. Pulse width T
Set i and exit the routine.

Here, in the starting injection control, the starting injection pulse width TiST and the cold start pulse width Ti0.
And the larger one is adopted as the fuel injection pulse width Ti to smooth the connection of the fuel injection amount from the cold start pulse width Ti0 to the starting injection pulse width TiST, and the fuel injection amount It prevents sudden changes and suppresses sudden changes in the air-fuel ratio to prevent deterioration of engine drivability and engine stall that accompany sudden changes in the air-fuel ratio.

On the other hand, in step S32, N> NST
When the engine is in the complete explosion state and it is determined to be the normal time control, the routine proceeds to step S33, where the voltage correction pulse width Ts for compensating the invalid time is added to twice the effective injection pulse width Te, and the fuel injection pulse width Set Ti.

Ti ← 2 × Te + TS As shown in FIG. 10, in the normal injection control,
Since the sequential injection (injection once every two rotations of the engine) is executed, a fuel amount (2 × Te) that is twice as much as that of the simultaneous injection (injection once per rotation of the engine) by the injection control at startup is required.

After that, the routine proceeds to step S34, the normal time control discrimination flag FFU is set, and at step S35, the fuel injection pulse width Ti calculated at step S33 is set and the routine is exited.

The output of the fuel injection pulse width Ti in the starting injection control or the setting of the fuel injection timing in the normal injection control after the complete explosion is set by the routine of FIG. 6 which is interrupted by the input of the θ3 pulse. To be executed.

In this θ3 pulse interrupt routine, first, in step S80, the value of the normal control discrimination flag FFU is referred to. If the starting injection control of FFU = 0 is selected, the process proceeds to step S81 and the input is performed. The generated θ3 pulse is # 3
Whether it is before the compression top dead center of the cylinder or the # 4 cylinder is discriminated, and if it is the θ3 pulse before the compression top dead center of the # 1 cylinder or the # 2 cylinder, the routine exits as it is, or the # 3 cylinder or When it is the .theta.3 pulse before the compression top dead center of the # 4 cylinder, the routine proceeds to step S82, where the drive pulse signals of the fuel injection pulse width Ti are simultaneously output to the injectors 30 of all the cylinders, and the routine is exited. As a result, as shown in FIG. 10, in starting fuel injection control, 1
The θ3 pulse input as a reference
The fuel of the fuel injection amount according to the pulse width TiST or the injection pulse width Ti0 at the time of starting is simultaneously injected into all cylinders.

On the other hand, when FFU = 1 and the normal injection control is selected, the routine proceeds to step S83, where the injection start timing TMSTART is calculated. In this embodiment, a so-called time control method is adopted, and the injection start timing is set by time.

At the injection start timing TMSTART, in order to complete the fuel injection earlier than the intake start timing (for example, BTDC 5 ° CA), before the set angle TENDIJ (for example, 30 ° CA) from the intake top dead center of each cylinder. Set to end fuel injection. This setting angle TENDI
In order to complete the fuel injection before J, the crank angle θM (730 (730) to the intake top dead center of the injection target cylinder is input every θ1 pulse or θ3 pulse input after the end of injection in the previous relevant injection target cylinder. ° CA to 10 ° CA
Of the above), the latest cycle Tθ2 · 3 (the time from the input of the θ2 pulse to the input of the θ3 pulse), which is updated every time the pulse signal is input, the cycle Tθ
3 ・ 1 (time from the input of θ3 pulse to the input of θ1 pulse) and the latest fuel injection pulse width T
The injection start timing TMSTART is calculated based on i.

In this step, as shown in FIG. 10, for example, the fuel injection target cylinder is the # 1 cylinder, and the fuel injection start timing is based on the θ3 pulse of θM (= 190 ° CA) before intake top dead center. An example of setting TMSTART is shown, and the fuel injection start timing TMSTART at this time is calculated by the following equation.

TMSTART ← (Tθ2 · 3 / θ2 · 3) × θM− (Ti + (θ2 · 3 / θ2 · 3) × TENDIJ) θ2 · 3; Angle between θ2 and θ3 pulses (in the present embodiment,
55 ° CA) θ3 · 1; Angle between θ3 and θ1 pulses (in this embodiment,
93 ° CA) Then, in step S84, the injection start timing TMSTART
Is set to the injection timer for the corresponding cylinder and the routine is exited.

After that, the starter is synchronized with the θ3 pulse input.
When the time measured by the set timer reaches the injection start timing TMSTART, the control routine for sequential injection shown in FIG. 7 is activated by interruption, and in step S90, the injector 30 of the fuel injection target cylinder is controlled by the normal injection control. A drive pulse signal having a fuel injection pulse width Ti is output and the routine is exited.

Therefore, as shown in FIG. 10, in the normal fuel injection control, the sequential injection is executed once per two revolutions for the corresponding cylinder.

Next, the supercharger switching control by the ECU 100 will be described with reference to the flowchart shown in the turbocharger switching control routine of FIGS. This turbocharger switching control routine turns on the ignition switch 97.
After N, it is executed every set time (for example, 10 msec).

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) as described above. First, in step S100, the twin-terminate mode determination flag is set. Refer to the value of F1. If the twin-termination mode flag F1 is cleared, the process proceeds to step S101, and if it is set, the process proceeds to step S160. This 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 the primary turbocharger 40 is overcharged. In addition to the charging operation, the secondary turbocharger 50 is fully charged to operate both turbochargers 4
It is set in the twin-ter mode in which both 0 and 50 are supercharged.

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

Immediately after the ignition switch 97 is turned on, and when the current control state is the single-terve mode, F
Since 1 = 0, the process proceeds to step S101.

In step S101, the single-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. 16, the turbo switching determination value table has a single 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. From single to twin mode, single to twin switching judgment line L2 and vice versa
Twin to switch from single mode to single mode
The single switching judgment line L1 was previously obtained from experiments under standard atmospheric pressure, and the single turbo area and twin turbine
BO area and are set. Then, each line L2, L
A single-to-twin switching determination basic value TP2B and a twin-to-single switching determination basic value TP1B corresponding to 1 are stored in advance in a series of addresses of 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 at the time of single turbo and the torque curve TQ2 at the time of twin turbo of the output characteristic of FIG. It is necessary to set it at the coincident point C. Therefore, as shown in FIG. 16, it is set to the low load side from the high load in the low and medium rotation speed range to the increase in the engine rotation speed N. Further, as shown in the figure, in order to prevent control hunting at the time of switching the number of turbocharger actuations, the twin → single switching determination line L1 is on the low rotation speed side with respect to the single → twin switching determination line L2. Is set up with a relatively wide hysteris.

Next, in step S102, the single-> twin atmospheric pressure correction coefficient 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. Set KTWNALT ≤ 1.0). As shown in FIG. 17, 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 S103, 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 S104, the single-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 S105, and in the case of TP ≧ TP2, the process branches to step S130 to shift 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. Therefore, as the atmospheric pressure ALT becomes lower, only the primary turbocharger 40 becomes supercharged from the single turbocharger 4 by the single-to-twin switching determination value TP2.
The single-to-twin switching determination line L2 for determining the switching to the twin turbo mode 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. , Is corrected to the low rotation side.

As a result, the engine operating range is advanced from the single turbo mode side to the twin turbo mode side with the single → twin switching determination line L2 as a boundary, and the single turbo mode is switched to the single → twin mode. The transition to the switching control is accelerated and the switching from the single turbo state to the twin turbo state is accelerated.

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, and the predetermined target supercharging is performed. When trying to obtain pressure, the rotation speed of the turbocharger becomes relatively high. As a result, the rate of increase in the number of revolutions of the primary turbocharger 40 also increases as the engine speed N representing the engine operating condition and the load TP increase. In a single turbocharged 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 region 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 is, the lower the atmospheric pressure ALT is from the single turbo mode based on the engine operating state to the 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 turbine. It is dispersed in the turbocharger 50 to prevent the primary turbocharger 40 from over-rotating. 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 condition, the rotation speed increase rate of the primary turbocharger 40 changes under the single turbo condition due to atmospheric pressure fluctuation, and the operating force due to the start of operation of the secondary turbocharger 50. The ring changes,
The lower the atmospheric pressure ALT is, the earlier the switching to the twin turbo state is performed, so that the driving feeling associated with the start of the operation of the secondary turbocharger 50 is maintained regardless of the atmospheric pressure change (for example, highland traveling and lowland traveling). Can be approximately the same.

On the other hand, if TP <TP2 in step S104 and the process proceeds to step S105, single turbo mode control is performed.

At step S105, the value of the supercharging pressure control mode discrimination flag F2 is referred to. The supercharging pressure control mode determination flag F2 is used to control the supercharging pressure by the small opening of the exhaust control valve 53 in the current operating region, and to perform the exhaust control valve small opening control for preliminarily rotating the secondary turbocharger 50. Set when inside the mode area and cleared when outside the area.

Therefore, the ignition switch 97 is turned on.
Immediately after N, the initial setting is performed, and when the operation region is outside the exhaust control valve small opening control mode region at the time of executing the previous routine, F2 = 0, so the process proceeds to step S106.
It is determined whether the current operating region has moved into the exhaust control valve small opening control mode region by the condition determination in steps S106 to S108.

This transition to the exhaust control valve small open control mode region is determined based on the relationship between the engine speed N and the intake pipe pressure (supercharging pressure) P as shown in FIG. On the low rotation and low load side of the line L2, that is, under the single turbo mode, the set value N2 (for example, 26
50 rpm), in a region surrounded by 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 S106, the intake pipe pressure P is compared with the set value P2 in step S107, and the throttle opening TH is compared with the set value TH2 in step S108. And N <N
If 2, or P <P2, or TH <TH2, the process proceeds to step S109, and the current operating region is the exhaust control valve small open control mode.
The supercharging pressure control mode determination flag F2 is determined to be outside the control range, and N ≧ N2 and P ≧ P2 and TH
When ≧ TH2, the routine proceeds to step S110, where it is judged that the current operating 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 routine proceeds to step S111, where the supercharging pressure relief valve switching solenoid valve SOL. 1 is turned off, and in step S112, the intake control valve switching solenoid valve SOL. Two
Turn off. Next, in step S113, the value of the supercharging pressure control mode determination flag F2 is referred to. If F2 = 0, the process proceeds to step S114, in which the first exhaust control valve switching solenoid valve SOL. 3 is turned off, and in step S115 the second exhaust control valve switching solenoid valve SOL. Turn off 4.

After that, in steps S116 to S118, the twin-wheel 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, and then the routine is exited.

Therefore, in the low-rotation, low-load operation region under the single turbo mode and 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 supercharging pressure relief valve 57 is connected to the supercharging pressure relief valve switching solenoid 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 urging force of the spring, and the intake control valve 55 causes 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 shut off, the secondary turbocharger 50 becomes inoperative, and the primary turbocharger is deactivated. Only 40 is in the supercharged single-turbo state. Further, the closing of the intake control valve 55 prevents the boost pressure from the primary turbocharger 40 from leaking to the secondary turbocharger 50 side via the intake control valve 55. The reduction of the boost pressure is prevented.

In the case of under the single turbo mode and outside the exhaust control valve small open control mode region, or under the twin turbo mode described later, the boost pressure feedback control is not performed. , I will not go into detail here
It is performed using only the 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, for example, the duty solenoid valve is controlled by PI control.
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 output the primary waist gate. This is done by controlling the valve 41.

On the other hand, if it is determined in step S110 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 S111 to The process proceeds to step S119 via S113, and the first exhaust control valve switching solenoid valve SOL. Turn on only 3. Therefore, the first exhaust control valve switching solenoid valve SO
L. By turning on 3, the positive pressure chamber 54a of the actuator 54
Positive pressure is introduced into the exhaust control valve 53 and the exhaust control valve 53 is opened.

Under the exhaust control valve small open control mode, the exhaust control valve small open control routine shown in FIG. 15 is executed every set time (for example, 480 msec).
The supercharging pressure feedback control is performed using the exhaust control valve 53, and the exhaust control valve 53 is slightly opened accordingly. That is, in FIG. 15, the value of the supercharging pressure control mode determination flag F2 is referred to in step S180, and when F2 = 0, the routine
In the exhaust control valve small open control mode with F2 = 1, the operation proceeds to step S181, and the boost pressure relief valve switching solenoid valve SOL. Determine the energization state for 1 and
L. When 1 = ON, the routine exits and the SOL. 1 =
When it is OFF, the routine proceeds to step S182, where the target boost pressure due to the absolute pressure and the actual boost pressure P detected by the absolute pressure sensor 81 are detected.
According to the comparison result, the exhaust control valve small opening control duty solenoid valve D.SO is controlled by, for example, PI control.
ON duty (duty ratio) for L.2 is calculated, and the duty signal of this ON duty is output to the duty solenoid valve D.SOL.2 for boost pressure feedback control. To execute. Therefore, the duty solenoid valve D.
The positive pressure acting on the positive pressure chamber 54a of the actuator 54 is regulated by SOL.2, and as shown in FIG. 27, the exhaust control valve 53 is opened slightly and the boost pressure is increased by using only the exhaust control valve 53. 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 5
0 is pre-rotated to prepare for the transition to the twin turbo state.

In this state, since the intake control valve 55 is closed, the supercharging pressure (secondary turbo overpressure) is provided between the intake control valve 55 and the downstream side of the compressor 50b of the secondary turbocharger 50. The compressor pressure by the feeder 50 is contained, but at this time, by opening the supercharging pressure relief valve 57, the supercharging pressure is leaked and the preliminary rotation is smoothed.

Further, 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). In this case, the process proceeds from step S105 to step S120, and it is determined whether the current operating region has moved to the outside of the exhaust control valve small open control mode region based on the condition determination of steps S120 to S122.

In order to prevent the control hunting at the time of switching the supercharging pressure control mode, the determination of the shift to the outside of this area is set to a value lower than the set values N2, P2 and TH2 as shown in FIG. Value N1 (eg 2600 rpm), P1 (eg 1070 mmHg), TH1 (eg 25 de
g). Then, the engine speed N and the set value N1 are compared in step S120, the intake pipe pressure (supercharging pressure) P and the set value P1 are compared in step S121, and step S122
Compare the throttle opening TH with the set value TH1, and set N <
If N1, P <P1, or TH <TH1, it is determined that the current operating region has moved out of the exhaust control valve small open control mode region, and the routine proceeds to step S109, where the boost pressure control mode is set.
The mode determination flag F2 is cleared. As a result, the exhaust control valve small opening control is released. Also, N ≧ N1 and P ≧ P1
If TH ≧ TH1, it is determined that the current operation region is still within the region, and the routine proceeds to step S110, where the supercharging pressure control mode determination flag F2 is held in the state of F2 = 1, and the exhaust gas is exhausted. Continue the control valve small opening control.

As described above, under the single turbo mode, most of the exhaust gas from the engine body 1 is introduced into the primary turbocharger 40 and the turbine 40b is rotationally driven by the turbine 40a. . So compressor 4
0b sucks in and compresses air, and this compressed air
It is cooled by the cooler 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 filling efficiency to perform supercharging. Then, in the single turbo mode in which only the primary turbocharger 40 by this single turbo mode is supercharged, as shown in the output characteristics of FIG. 33, the shaft torque is high in the low and medium speed ranges. A torque curve TQ1 at the time of a single turbo is obtained.

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

In step S104, TP ≥TP2, that is, the current operation area is the single → twin switching determination line L.
If it is determined that the single turbo area has moved to the twin turbo area (see FIG. 24) at the boundary of step 2, step S1
Single to twin for branching to 30 and switching from the single turbo state where only the primary turbocharger 40 is supercharged to the twin turbo state where both turbochargers 40 and 50 are supercharged. Executes switching control.

Then, first, at step S130, the supercharging pressure relief valve switching solenoid valve SOL. 1 is determined, and in step S132, 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 S134. Further, each of the switching solenoid valves SOL. When 1 and 3 are OFF, steps S131 and S133
After turning on respectively, proceed to step S134.

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 by turning on 3
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-to-twin switching control, the supercharging pressure relief valve switching solenoid valve SOL.
When the exhaust control valve small open control routine shown in FIG. 15 is turned on by turning on 1, the exhaust control valve 53 is supercharged by exiting the routine through step S181 without performing boost pressure feedback control. The pressure feedback control is stopped, the exhaust control valve small open control duty solenoid valve D.SOL.2 is fully closed, and the positive pressure via the positive pressure passage 64b is reduced to the duty solenoid valve D.SOL. Since it is directly introduced into the positive pressure chamber 54a of the actuator 54 without being leaked by .2,
The opening degree of the exhaust control valve 53 is increased.

Then, the relief passage 58 is closed by closing the supercharging pressure relief valve 57, and the exhaust control valve 53 is opened and its opening is increased, so that the secondary turbocharger 50 is opened. As the rotation speed is increased, 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 S134, the value of the differential pressure search flag F3 is referred to. If F3 = 0, the process proceeds to step S135 and F
If 3 = 1, jump to step S139.

Since F3 = 0 at the first execution of the routine after shifting to the single-to-twin switching control, step S135
First, referring to the exhaust control valve opening delay time table with interpolation calculation based on the vehicle speed VSP, first, the full open control of the exhaust control valve 53 (second exhaust control Switching solenoid valve SOL.4 for valve OFF
The exhaust control valve opening delay time T1 that determines the timing is set, and in step S136, the intake control valve opening delay time table is referenced with interpolation calculation based on the vehicle speed VSP, and the exhaust control valve Intake control valve 55 after full open control of 53
Open control of intake valve (switching solenoid valve for intake control valve SOL.2
Is set from OFF to ON) The intake control valve opening delay time T2 for setting the condition of the start timing is set. further,
In step S137, the upstream pressure PU and the downstream pressure P of the intake control valve 55
Differential pressure with D (read value of differential pressure sensor 80) DPS (= P
U-PD), the intake control valve opening differential pressure DPSST for determining the opening control start timing of the intake control valve 55 is set by referring to the intake control valve opening differential pressure table with interpolation calculation. .

FIG. 19 shows a conceptual diagram of the exhaust control valve opening delay time table, and FIG. 20 shows the intake control valve opening delay time table.
The respective conceptual diagrams of Bull are shown below. As shown in the figure, the vehicle speed V
The higher the SP, the shorter the exhaust control valve opening delay time T1 and the intake control valve opening delay time T2, and the exhaust control valve 53
Is accelerated and the timing of opening the intake control valve 55, that is, the timing of switching to the twin turbo mode is advanced so that the acceleration response is made uniform regardless of the vehicle speed to improve drivability.

Further, FIG. 21 shows a conceptual diagram of the intake control valve opening differential pressure table. As shown in the figure, immediately after the engine operating state shifts from the single turbo region to the twin turbo region (see FIG. 24) with the single → twin switching determination line L2 (single → twin switching determination value TP2) as a boundary. The more the differential pressure DPS is on the negative side, that is, the higher the downstream pressure PD is with respect to the upstream pressure PU of the intake control valve 55 and the higher the supercharging state is, the more negative the intake control valve opening differential pressure DPSST is, the more the intake control is performed. The timing of opening the valve 55 is advanced to improve the acceleration response.

Then, these delay times T1, T2,
After setting the intake control valve opening differential pressure DPSST, the process proceeds to step S138, the differential pressure search flag F3 is set, and the process proceeds to step S139.

In step S139, 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. If 4 = ON and exhaust control valve full-open control has already started, step S1
Jump to 49, SOL. If 4 = OFF, it means that the exhaust control valve fully open control has not yet been executed, and therefore the process proceeds to step S140.
The control valve switching time count value C1 is compared with the exhaust control valve opening delay time T1 to determine whether the exhaust control valve opening delay time T1 has elapsed after shifting to the single-to-twin switching control.

Then, in the case of C1 ≧ T1, step
Jumping to S147, the switching solenoid valve for the second exhaust control 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 S141, where the engine load TP and the value obtained by subtracting the set value WGS from the single-to-twin switching determination value TP2 set in step S103 are compared. And TP <
In the case of TP2-WGS, the process returns to step S109 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 engine returns to the single turbo mode so as to eliminate the uncomfortable feeling of driving.

More specifically, as shown in FIG.
The engine operating range is from single turbo range to single →
Once the twin switching judgment line L2 (TP2) is crossed to the twin turbo area side, twin → single switching judgment line L
As long as 1 (twin → single switching judgment value TP1, details will be described later) is not exceeded on the single turbo area side, the delay
After the time T1 has elapsed, the exhaust control valve 53 is fully opened (step S147), and after the delay time T2 has elapsed, the differential pressure DP
When S reaches the intake control valve opening differential pressure DPSST, the intake control valve 55 is opened (step S152), 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 region remains within the region surrounded by the single-to-twin switching determination line L2, the switching to the twin turbo state will occur after the delay time has elapsed. However, in this region, as shown in FIG. 33, the axial torque at the time of the twin turbo by the operation of the secondary turbo supercharger 50 becomes rather lower than the axial torque at the time of the single turbo, and the single turbo is rather reduced. When the state is switched to the twin turbo state, a sudden decrease in torque causes a torque shock and gives the driver a feeling of strangeness.

In order to deal with this, the twin → single switching determination line L1 is changed to the single → twin switching determination line L.
The width of both switching lines (hysteresis) may be narrowed by approaching to 2, but if the width between both switching lines L1 and L2 is narrowed, the switching frequency between the single turbo and the twin turbo increases, and each control is controlled. Since the negative pressure capacity of the surge tank 60 as a negative pressure source for operating the valve is insufficient, the surge tank 60 must have a large capacity, and if the width is too narrow, the operating condition is single → twin. When it stays in the vicinity of the switching judgment line L2, the supercharging 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. There is.

In order to prevent these, after the engine operating area exceeds the single-twin switching determination line L2 toward the twin turbo area, and before the delay time T1, the single-twin switching determination line has a narrow interval. Single-to-twin switching determination stop line L3 (= TP2 shown by broken line in FIG. 16 obtained by subtracting the set value WGS from the single turbo area side.
-WGS) is exceeded to the single turbo area side, the single-twin switching control for switching to the twin-turbo state is stopped and the single-turbo mode is immediately changed to the primary turbocharger 40. Only by maintaining the supercharged single-turbo state, the operation in the low torque region in the twin-turbo state is eliminated and the drivability is improved.

On the other hand, in step S141, TP ≧ TP2−
In the case of WGS, the process proceeds to step S142 to set the primary turbo overspeed determination basic value EM2TP by referring to the switching determination value table with interpolation calculation based on the engine speed N. This primary turbo overspeed judgment basic value EM2TP
Indicates that after the shift to the single-twin switching control, the engine operating region shifts to the primary turbo over-rotation region under the single turbo condition due to the rapid increase in the engine speed N and the engine load TP before the delay time T1 elapses. This is a reference value for determining whether or not the primary turbo overrun is under the single turbo condition from the relationship between the engine speed N and the engine load TP at standard atmospheric pressure, as shown in FIGS. The primary turbo overrotation determination line L4, which is the boundary of the primary turbo overrotation region (indicated by diagonal lines in FIG. 23) where the feeder 40 reaches the critical rotational speed, is obtained in advance by experiments or the like.
Corresponding to the primary turbo overspeed determination line L4 at the standard atmospheric pressure, it is stored in advance in a series of addresses in the ROM 102 as a switching determination value table with the engine speed N as a parameter. Of course, the primary turbo overspeed determination line L4 is set on the higher load side than the single-to-twin switching determination line L2.

Next, at step S143, the judgment value atmospheric pressure correction coefficient KEM2 is set by referring to the judgment value atmospheric pressure correction coefficient table with interpolation calculation based on the atmospheric pressure ALT. FIG. 22 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 S144, 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 EMV2
In the case where the primary turbo overspeed determination line L4 by TP is the standard atmospheric pressure shown by the solid line in FIG. 24, as with the single-to-twin switching determination line L2, the low load and low rotation side is indicated by the dashed line. Is corrected to be always set to the high load side from the single-to-twin switching determination line L2 regardless of the atmospheric pressure change.

Then, in step S145, the engine load T
P is compared with the primary turbo overspeed judgment value EMV2TP, and if TP <EMV2TP, the routine proceeds to step S146, where the control valve switching time count value C1 is counted up and the routine is exited. On the other hand, TP ≥ EMV2TP, and the engine speed N, before the delay time T1 elapses.
Due to the rapid increase in the engine load TP, the engine operating region has shifted to the primary turbo overspeed region (for example, sudden acceleration,
(Corresponding to the case of lacing, etc.), the routine proceeds to step S147, where the second exhaust control valve switching solenoid valve SOL. 4 is immediately turned on, the exhaust control valve 53 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 of 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 causing 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 to prevent damage. Is reliably prevented.

At this time, as described above, the atmospheric pressure AL
The engine operating range in which the primary turbocharger 50 is in the over-rotation state becomes wider as T becomes lower, and the engine operating range is expanded to the low load and low rotation side. The primary turbo over-rotation determination line L4 for determining is corrected to a low load and low rotation side as the atmospheric pressure ALT decreases, so that the primary turbo over-rotation can be accurately performed even if the atmospheric pressure ALT changes. Therefore, the primary turbocharger 40 can be properly and reliably prevented from over-rotating regardless of changes in atmospheric pressure, and damage can be prevented.

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

After shifting to the single-to-twin switching control, when the exhaust control valve opening delay time T1 elapses and the process proceeds from step S140 or from step S145 to step S147, 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 by the secondary turbocharger 50 between the compressor 50b and the intake control valve 55. The pressure (supercharging pressure) also rises, and as shown in FIG. 27, the differential pressure DPS between the upstream side and the downstream side of the intake control valve 55 rises.

After that, the process proceeds to step S148, the control valve switching time count value C1 is cleared to measure the time after the exhaust control valve fully open control, and the process proceeds to step S149.

Then, the step S139 or the step
When the process proceeds from step S148 to step S149, the count value C1 representing the time after the exhaust control valve fully open control (SOL.4 OFF → ON) is compared with the intake control valve open delay time T2, and C
When 1 <T2, it is determined that the condition for opening the intake control valve 55 is not satisfied, and in step S146 the count value C1 is incremented and the routine is exited. Also, C1 ≧ T
When it is 2, it is determined that the valve opening condition is satisfied, and the routine proceeds to step S150, where the current differential pressure DPS and the intake control valve opening differential pressure DPSST.
Are compared with each other to determine whether the opening start timing of the intake control valve 55 has been reached.

When DPS <DPSST, it is determined that the valve opening start timing has not been reached, and the routine proceeds to step S151. When DPS ≧ DPSST, the upstream pressure PU and downstream pressure PD of the intake control valve 55 are substantially equal to each other. Equal, that is, the compressor 50 of the secondary turbocharger 50
b between the intake control valve 55 and the secondary turbocharger 5
The supercharging pressure due to 0 increases and the primary turbocharger 40
It becomes substantially equal to the boost pressure due to the intake control valve, and it is judged that the intake control valve opening start timing has been reached, and the routine proceeds to step S152, where the intake control valve switching solenoid valve SOL. 2 is turned on and the intake control valve 55 is opened.

As a result, supercharging from the secondary turbocharger 50 is started, and the twin turbo state is established. Then, the process proceeds to step S153, and when the single-to-twin switching control is completed, the twin-ter mode discrimination flag F1 is set next time to shift to the twin-ter mode.
Get out of the chin.

In step S150, DPS <DPS
When it is determined to be ST and the process proceeds to step S151, the count value C1 is further set to the intake control valve opening delay time T.
Compared with the value obtained by adding the set value TDP to 2, C1 <T2 +
If TDP, the process proceeds to step S146, where the count value C1
Counts up and exits the routine, C1 ≧ T2 + T
When it is DP, the routine proceeds to step S152, where the intake control valve switching solenoid valve SOL. Is operated even if the differential pressure DPS has not reached the intake control valve opening differential pressure DPSST. 2 is turned on, the intake control valve 55 is opened, and the mode is changed to the twin mode.

That is, when the differential pressure DPS by the differential pressure sensor 80 does not rise due to the failure of the differential pressure sensor 80 system, the exhaust control valve 53 is turned on after the first set time by the exhaust control valve opening delay time T1 has elapsed. After the fully open control, the intake control valve 55 is not opened at any time after the second set time by the intake control valve opening delay time T2 has elapsed.
During this time, the compressor 5 of the secondary turbocharger 50
The supercharging pressure (compressor pressure) by the secondary turbocharger 50 is contained between 0b and the intake control valve 55,
The supercharging pressure between the secondary 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 does not reach the intake control valve open differential pressure DPSST (set value) after the second set time has elapsed after the exhaust control valve 53 is fully opened, the first pressure given by T2 + TDP is given. After the elapse of the set time of 3, the intake control valve 55 is opened, so that the secondary turbocharger 50 and the intake control valve 5
5 to prevent the boost pressure from abnormally increasing, and the differential pressure sensor 80
The secondary turbocharger 50 is prevented from being damaged due to the system failure.

The state of switching from single-tor mode to twin-ter mode by the above single-to-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 and the exhaust control valve 53 is opened, so that the secondary turbocharger 50 is opened. The exhaust control valve opening delay time T1 gives the time required to increase the auxiliary engine speed and then increase the auxiliary engine speed of the secondary turbocharger 50.
After the delay time T1 has elapsed, the exhaust control valve 53 is fully opened. Then, 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 the lapse of time T2, 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,
Only the primary turbocharger 40 is supercharged in a single turbo mode, and when the turbochargers 40 and 50 are supercharged, the turbo mode is switched to a twin turbo mode.
Further, when the upstream pressure PU and the downstream pressure PD of the intake control valve become substantially equal, the intake control valve 55 is opened to start the full-scale supercharging operation of the secondary turbocharger 50. It is possible to effectively and surely prevent the occurrence of torque shock due to a temporary decrease in boost pressure that occurs when switching to the twin turbo mode.

Further, at this time, in synchronization with the opening of the intake control valve 55, as described above, the fuel injection pulse width Ti as the fuel supply amount is reduced and corrected by the twin turbo switching correction coefficient KTWIN, and the air-fuel ratio is adjusted. Is forcibly corrected to the lean state. As a result, the amount of fuel adhering to the wall surface decreases, and
The amount of heat of vaporization accompanying the fuel vaporization decreases, the intake port wall surface temperature and the combustion chamber temperature rise, and the exhaust gas temperature rises. As a result, the exhaust energy is increased and the operating efficiency of both turbochargers 40, 50 is improved.

Therefore, the actual supercharging pressure is as shown by the solid line in the case where there is no reduction correction of the fuel injection amount by the twin turbo switching correction coefficient KTWIN shown by the two-dot chain line in FIG.
It is possible to obtain a supercharging pressure characteristic closer to the target supercharging pressure indicated by the broken line, and immediately after the full-scale supercharging operation of the secondary turbocharger 50 is started by opening the intake control valve 55, the secondary turbocharging is performed. The temporary decrease in the supercharging pressure due to the loss due to the operation of the supercharger 50 is reliably eliminated, and the occurrence of the torque shock due to the reduction in the supercharging pressure is more effectively eliminated.

After that, the twin-turbo switching correction coefficient KTWIN is gradually reduced to 0 to gradually reduce the reduction correction for the fuel injection amount, so that the air-fuel ratio gradually changes from the lean state. Then, the air-fuel ratio is returned to the normal air-fuel ratio, the air-fuel ratio lean state is smoothly connected to the normal air-fuel ratio, and deterioration of drivability due to a sudden change in the air-fuel ratio is prevented.

Further, even if the set time (exhaust control valve opening delay time T1) has not been reached after shifting to the single-to-twin switching control, TP≥EMV2TP (step S145) causes the engine operating region to be in the single turbo state. When it is judged below that it has moved to the primary turbo overspeed region,
Immediately after that, the second switching solenoid valve SOL. Four
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 becomes an over-rotation state due to a rapid increase in the exhaust pressure and the exhaust flow rate. Damage to the primary turbocharger 40 due to reaching the rotational speed and causing surging is reliably prevented.

Further, in the primary turbo over-rotation region, that is, in the engine high load and high rotation state, the exhaust control valve 53 is advanced in advance so that the intake control valve 55 starts to open correspondingly. The timing is advanced and the twin turbo mode is quickly switched. Therefore, as shown in the output characteristic diagram of FIG. 33, the twin-turbo state in which the shaft torque is high is switched from the single-turbo state to an early stage in the high-rotation side region with the single-to-twin switching determination line L2 as a boundary. As a result, at the same time, good acceleration performance can be obtained by adapting to the driver's acceleration request.

After the exhaust control valve 53 is fully opened (SO
L. 4 OFF → ON), and further after the intake control valve opening delay time T2 (second set time) has elapsed, the intake control valve 55
The differential pressure DPS between the upstream side and the downstream side of the intake control valve opening differential pressure DPS
When the third set time by T2 + TDP elapses before reaching ST, the intake control valve 55 is immediately opened (SOL.2 OFF → ON), and the secondary turbo valve due to the failure of the differential pressure sensor 80 system is Supercharger 50 and intake control valve 5
By preventing the abnormal increase of the supercharging pressure between 5 and 5, the secondary turbocharger 50 is prevented from being damaged, and when switching from the single turbo state to the twin turbo state,
The reliability of the secondary turbocharger 50 is improved.

Next, the twin-ter mode will be described.

When the twin routine mode determination flag F1 is set by the end of the single-to-twin switching control, or when the twin routine is executed at the previous routine execution, F1 is executed at the current routine execution. = 1 for step S1
The process branches from 00 to step S160.

Then, in step S160, the engine speed N
Based on this, refer to the turbo switching judgment value table with interpolation calculation to set the twin-> single switching judgment basic value TP1B (see FIG. 16), and proceed to step S161 to set the 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. 25, 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 is set in the same manner as the single-to-twin atmospheric pressure correction coefficient table. As the
A small value of twin → single atmospheric pressure correction coefficient KSGLALT is stored.

Then, in step S162, the twin-to-single switching judgment basic value TP1B is corrected by the twin-to-single atmospheric pressure correction coefficient KSGLALT to judge switching from the twin-ter mode to the single-ter mode. Set the twin to single switching judgment value TP1 for switching.

Twin-to-single atmospheric pressure correction coefficient KSG
By setting LALT 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 different from 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, the single → twin switching determination line L2 for determining the switching from the single turbo state to the twin turbo state and the twin → for determining the switching from the twin turbo state to the single turbo state → It becomes possible to set a proper constant hysteresis to the single switching judgment line L1 regardless of the change in atmospheric pressure ALT.
Control hunting for switching turbo turbochargers can be effectively and surely prevented.
Atmospheric pressure ALT for the operation filling that accompanies switching to the BO state.
Approximately the same regardless of the change of.

Next, in step S163, 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 it is determined in step S164. The value search flag F4 is cleared, and in step S165, the single turbo area duration time count value C2 for counting the single turbo area duration time after the transition to the single turbo area is cleared, and then in step S174. Jump to step S174 to step S177, and changeover solenoid valve SO for boost pressure relief valve
L. 1, intake control valve switching solenoid valve SOL. 2, first and second exhaust control valve switching solenoid valves SOL. Three
4 is turned on, the supercharging pressure relief valve 57 is closed, and both the intake control valve 55 and the exhaust control valve 53 are held fully open. In step S178, the twin turbo mode determination flag F is set.
After setting 1 and returning to step S118 to clear the control valve switching time count value C1, the routine is exited.

Under 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.
When the turbo turbocharger 40 is fully opened, the secondary turbocharger 50 in addition to the primary turbocharger 40 is fully supercharged, and the twin turbochargers 40 and 50 are supercharged. In this state, compressed air is supplied to the intake system due to the supercharging of both turbochargers 40 and 50, and as shown in the output characteristics of FIG. A torque curve TQ2 is obtained.

On the other hand, when it is determined in step S163 that TP≤TP1, that is, it is determined that the current operating region has shifted to the single turbo region (see FIG. 24) with the twin-to-single switching determination line L1 as a boundary, step S163 The process proceeds to S166, refers to the value of the determination value search flag F4, proceeds to step S167 when F4 = 0, and proceeds to step S169 when F4 = 1.
Jump to.

The judgment value search flag F4 is a twin counter.
In the mode, the engine load TP is twin → larger than the single switching judgment value TP1 and the engine operating range is twin →
Twin switch with single switching judgment line L1 (TP1) as a boundary
It is cleared when it is in the region (step S164). Therefore, after TP ≤ TP1, at the time of the first routine execution, the process proceeds to step S167, and the single turbo region continuation time determination value table is referred to with the interpolation calculation based on the engine load TP, and the single turbo region is referred. The duration determination value T4 is set. This judgment value T4 is a twin value in the engine operating range.
This is a reference value for switching to the single turbo mode in which only the primary turbocharger 40 is supercharged after a lapse of a predetermined time after the transition from the bob area to the single turbo area.

FIG. 26 is a conceptual diagram of the single turbo area continuation time judgment value table. The single turbo area 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 region is switched from the twin turbo region to the single turbo region, the time until switching from the twin turbo mode to the single turbo mode is made faster as the engine load is higher.

Next, after the judgment value search flag F4 is set in step S168, the process proceeds to step S169.

Then, in step S169, after counting up the single turbo area continuation time count value C2, the judgment value T4 is compared with the count value C2 in step S170. If C2 ≧ T4, the process proceeds to step S173. After clearing the count value C2, the process returns to step S109, and the twin-ter mode is switched to the single-ter mode. As a result, each switching solenoid valve SOL. 1 to 4 are turned off, the boost pressure relief valve 57 is opened, and the intake control valve 5
5 and the exhaust control valve 53 are both closed, so that only the primary turbocharger 40 is supercharged from the twin turbo state in which the superchargers 40 and 50 are supercharged.
Switch to the BO state.

The switching state at this time is shown by a time chart as shown by the solid line in FIG. As described above, the switching from the twin turbo mode to the single turbo mode is performed after the engine operating region is switched from the twin turbo region to the single turbo region (TP≤TP1), and the state is set time. When it continues (C2 ≧ T4), it is performed, and 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 single turbo mode is switched to the single turbo mode. The reason is quick. That is, although high torque is required during engine high load operation, as shown in FIG. 33, the axial torque curve TQ2 during twin turbo is shown on the single turbo area side with the twin → single switching determination line L1 as a boundary. Applied torque (for example, point A in the figure)
The torque (point B in the figure) given by the axial torque curve TQ1 at the time of single turbo is higher than that. If the twin turbo state is maintained in this area, the axial torque cannot be obtained sufficiently and the output performance deteriorates. However, the re-acceleration performance also deteriorates. Therefore, at the time of high engine load, the single turbo region continuation time determination value T4 is set to a short value to speed up the switching from the twin turbo state to the single turbo state,
By quickly switching to the single-turbo state in which the torque is high with the minimum required operation in the low-torque region in the twin-turbo state (transition from point A to point B in FIG. 33),
Improves output performance and re-acceleration performance.

Further, during low load operation, it is in a low torque state, the difference in torque between twin turbo and single turbo is small, and the above set time is sufficiently given to change from the twin turbo state to the single turbo state. Even if it is switched to the bob state, there is almost no torque fluctuation. For this reason, when the engine load is low, the engine operating range shifts from the twin-turbo region side to the single-turbo region at the twin-to-single switching determination line L1, and then the state is set to 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 relatively long time given, the unnecessary switching of the supercharger due to the engine speed N temporarily decreasing is effective and reliable. Avoided.

On the other hand, in the above step S170, C2 <T
In the case of 4, the process proceeds to step S171 and the throttle opening TH
And the set value TH3 (for example, 30 deg) are compared, and T
When H> TH3, the above steps S173 and S1 are executed.
Returning to 09, after the engine operating area has shifted to the single turbo area, even before that state continues for the set time, as shown by the broken line in FIG. 28, the mode is immediately switched to the single turbo mode. The supercharging pressure relief valve 57 is opened, and the exhaust control valve 53 and the intake control valve 55 are both closed, so that the supercharging operation of the secondary turbocharger 50 is stopped and the primary turbo valve is stopped. Only the turbocharger 40 is a supercharger
It is switched to BO state.

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. 33, it is on the low rotation side of the twin → single switching determination line L1, and the axial torque of the torque curve TQ2 during twin turbo is This is a low region, and 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 judged that acceleration is required (TH> TH3) while operating in this region, the single turn is immediately applied.
The acceleration response is improved by shifting to the mode and setting the single-turbo state to obtain the torque curve TQ1 of high shaft torque during the single-turbo.

If TH≤TH3 in step S171, the flow advances to step S172 to set the vehicle speed VSP and the set value V
Compare with SP2 (for example, 2Km / h), VSP> V
If it is determined in SP2 that the vehicle is running, the process proceeds to step S174 to maintain the twin-board mode, and
When it is determined that the vehicle is stopped at VSP2, the process returns to step S109 through step S173 as described above, and immediately shifts to the single turbo mode.

The above set value VSP2 is for judging the stopped state of the vehicle. When the accelerator is stepped on and the engine is idled while the vehicle is stopped, for example, in the state of idle speed, the engine load TP is increased. The engine speed N rises, the engine operating range shifts from the single turbo range to the twin turbo range, the twin turbo mode is established, and the engine load TP is reached after the accelerator is released.
When the engine speed N immediately decreases and the engine operating region again shifts to the single turbo region with the twin-to-single switching determination line L1 (see FIG. 16 or FIG. 24) as a boundary, it shifts to the single turbo region. After that, if the set time does not elapse (C2 ≧ T4), the mode is not switched to the single turbo mode. During this time, the engine speed N decreases, and after switching to near the idle speed (for example, near 700 rpm), each switching is performed. Solenoid valve SOL. The switching of 1 to 4 is performed, and the supercharging pressure relief valve 57 and each control valve 53, 5
5 is 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 ≦ VSP2), after shifting to the single turbo area,
Even if the set time has not elapsed (C2 <T4), by immediately switching to the single turbo mode, the switching of each valve is completed before the engine speed decreases and the background noise decreases. Eliminates the discomfort caused by valve operation noise. In addition,
At this time, the twin-ter mode is changed to the single-ter mode.
The state of switching to the switch is shown by the alternate long and short dash 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.

[0184]

As described above, according to the present invention,
At the start of full-scale supercharging operation of the secondary turbocharger by opening the intake control valve from the supercharging operation of only the primary turbocharger, the fuel supply amount is reduced and the air-fuel ratio is forced. Since the amount of fuel adhered to the wall surface is reduced, the amount of heat of vaporization accompanying the fuel vaporization is reduced, and the temperature of the intake port wall surface and the temperature of the combustion chamber are increased to raise the exhaust gas temperature. As a result, the exhaust energy is increased, the operating efficiency of the supercharger is improved, the decrease of the supercharging pressure due to the start of the full-scale supercharging operation of the secondary turbocharger is suppressed, and the supercharging pressure is temporarily reduced. The occurrence of torque shock due to a decrease in temperature is eliminated.

After that, since the air-fuel ratio is gradually returned from the lean state to the normal air-fuel ratio, the air-fuel ratio is smoothly connected to the normal air-fuel ratio, and the air-fuel ratio is smoothly changed. It is possible to prevent deterioration of drivability due to a sudden change in the vehicle and obtain good driving performance.

[Brief description of drawings]

FIG. 1 is a flowchart showing a routine for setting a fuel injection pulse width.

FIG. 2 is a flowchart showing a fuel injection pulse width setting routine (continued).

FIG. 3 is a flowchart showing a fuel injection pulse width setting routine (continued).

FIG. 4 is a flowchart showing a subroutine for setting a correction coefficient when switching twin turbos.

FIG. 5 is a flowchart showing a routine for cylinder discrimination / engine speed calculation.

FIG. 6 is a flowchart showing an injection timing setting routine.

FIG. 7 is a flowchart showing a control routine for sequential injection.

FIG. 8 is an explanatory diagram showing a switching state between the startup injection control and the normal injection control.

FIG. 9 is an explanatory diagram of a basic value table.

FIG. 10 is a crank angle sensor output, a cam angle sensor output,
Time chart showing the relationship between intake timing, starting injection, and normal injection

FIG. 11 is a flowchart showing a turbocharger switching control routine.
Chart

FIG. 12 is a flow chart showing a turbocharger switching control routine.
Chart (continued)

FIG. 13 is a flow chart showing a turbocharger switching control routine.
Chart (continued)

FIG. 14 is a flowchart showing a turbocharger switching control routine.
Chart (continued)

FIG. 15 is a flowchart showing an exhaust control valve small opening control routine.

FIG. 16 is an explanatory diagram showing each switching determination value and the relationship between the single turbo area and the twin turbo area.

[Fig. 17] Conceptual diagram of single → twin atmospheric pressure correction coefficient table

FIG. 18 is an explanatory diagram of an exhaust control valve small opening control mode area.

FIG. 19 is a conceptual diagram of an exhaust control valve opening delay time table.

FIG. 20 is a conceptual diagram of an intake control valve open delay time table.

FIG. 21 is a conceptual diagram of an intake control valve opening differential pressure table.

FIG. 22 is a conceptual diagram of a judgment value atmospheric pressure correction coefficient table.

FIG. 23 is an explanatory diagram showing a relationship between each determination line and a primary turbo over-rotation region.

FIG. 24 is an explanatory diagram showing an atmospheric pressure correction state of each determination line.

FIG. 25: Conceptual diagram of twin → single atmospheric pressure correction coefficient table

FIG. 26 is a conceptual diagram of a single turbo area continuation time judgment value table.

[Fig. 27] Single-terminate mode to twin-terrace mode
Time chart showing switching status

FIG. 28: Twin-terminate to single-terminate
Time chart showing switching status

FIG. 29 is an overall configuration diagram of an engine with a supercharger.

FIG. 30 is a front view of a crank rotor and a crank angle sensor.

FIG. 31 is a front view of a cam rotor and a cam angle sensor.

FIG. 32 is a circuit diagram of the control device.

FIG. 33 is an explanatory diagram showing output characteristics at the time of single turbo and at the time of 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) KTWIN ... Twin turbo switching correction coefficient Ti ... Fuel injection pulse Width (fuel supply)

Claims (1)

[Claims] 1. A primary engine for the intake and exhaust systems of an engine.
The turbocharger (40) and the secondary turbocharger (50) are arranged in parallel, and when the engine operating region is in the low speed range, the suction connected to the secondary turbocharger (50), Close both the intake control valve (55) and exhaust control valve (53) respectively installed in the exhaust system, or open only the exhaust control valve and open only the primary turbocharger (40). Air-fuel ratio of the engine with a supercharger that operates the turbocharger (40, 50) by fully opening both control valves (55, 53) in the high speed range. In the control method, at the time of switching from the supercharging operation of only the primary turbocharger (40) to the supercharging operation of both turbochargers (40, 50), the intake control valve (55) is opened. The air-fuel ratio control of the supercharged engine is characterized in that the fuel supply amount is reduced and the air-fuel ratio is lean-corrected in synchronization with the valve, and then the air-fuel ratio is gradually returned to the normal air-fuel ratio. Method.