JPH0719058A - Control method for engine having superchanger - Google Patents

Abstract

PURPOSE:To improve operability by stopping switching to a twin turbo condition when an operating area is judged as a low torque area in the twin turbo condition when a condition is switched to the twin turbo condition from a single turbo condition. CONSTITUTION:After an engine operating area is shifted to a single turbo area from a twin turbo condition with a single twin switching judging line as its boundary, judgment (step S40) is made on whether or not preset time T1 passes, and before the preset time T1 passes, judgment (step S41) is made on whether or not the operating area crosses a single twin switching judgment stopping line set at a narrow interval to the single twin switching judging line between the single twin switching judging line and a twin single switching judging line to the single turbo area side. When the operating area crosses the single twin switching judgment stopping line to a single turbo condition side, switching to a twin turbo condition is stopped at once, and a single turbo condition is maintained.

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 the intake and exhaust systems of an engine, and switches the operating number of turbochargers based on operating conditions. The present invention relates to a control method for an engine with a feeder.

[0002]

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

In this supercharged engine, the engine operating range is divided into a low speed range single turbo range and a high speed range twin turbo range, and when the operating range is the single turbo range, the intake control valve is closed. At the same time, the exhaust control valve is closed or opened slightly (to preliminarily rotate the secondary turbocharger) and only the primary turbocharger is supercharged. When the operating range is in the twin turbo range, both control valves are Both are fully opened and both turbochargers are supercharged to improve output performance from the low speed range to the high speed range.

Further, as shown in FIG. 13, in this type of supercharged engine, when viewed from the relationship between the shaft torque and the engine speed (however, the engine load is constant), only the primary turbocharger is overcharged. In contrast to the torque curve TQ1 at the time of single turbo operation of the feed operation, the torque curve TQ2 at the time of twin turbo operation in which both turbochargers are supercharged is higher than a certain rotational speed, and a high shaft torque can be obtained. In the region lower than the rotation speed, the operation of the secondary turbocharger rather reduces the axial torque during twin turbo.
Therefore, the single turbo state is switched to the twin turbo state at the point C where the two torque curves in the figure match. However, since the matching rotational speeds of both torque curves differ depending on the engine load, the matching points of both torque curves are found in advance by experiments or the like corresponding to the engine load and engine speed, and as shown in FIG. The determination line L2 is set, and when the engine operating region shifts from the single turbo region on the low speed side to the twin turbo region on the high speed side with the single → twin switching determination line L2 as a boundary, the exhaust control valve is opened slightly, or Maintain a small opening, increase the rotation speed of the secondary turbocharger, fully open the exhaust control valve after the set time elapses, increase the compressor pressure by the secondary turbocharger, and then open the intake control valve Only the turbocharger is switched from the single turbo state of supercharging operation to the twin turbo state of supercharging operation of both turbosuperchargers. So as to prevent the occurrence of torque shock to prevent torque fluctuations at the time of switching to the twin turbo state turbo state.

Further, as shown in FIG. 8, in order to prevent control hunting at the time of switching the number of operating turbochargers, the twin-turbo state is switched from the single-turbo state to the single-twin switching determination line L2. The twin-to-single switching determination line L1 for determination is set to the low rotation side to provide hysteresis (Japanese Patent Laid-Open No. 3-260).
326).

[0006]

However, in the above-described prior art example, once the engine operating range exceeds the twin turbo range with the single-to-twin switching determination line L2 as a boundary,
Unless the twin-to-single switching determination line L1 is returned to the single turbo region side, the exhaust control valve is fully opened and the intake control valve is opened after the set time elapses to switch to the twin turbo state. In other words, if the engine operating region temporarily shifts the single-to-twin switching determination line L2 to the twin turbo region side and then remains in the region surrounded by both switching determination lines L2 and L1, the engine is switched to the twin turbo state, As shown in FIG. 13, in this region, the axial torque at the time of single turbo (for example, point A in the figure) given by the torque curve TQ1 is different from the axial torque at the time of twin turbo (point B in the figure) given by the torque curve TQ2. However, when switching from the single turbo state to the twin turbo state at this time, there is a problem that a sudden shock of torque causes a torque shock and gives a driver a feeling of strangeness.

The present invention has been made in view of the above circumstances, and when switching from the single turbo state to the twin turbo state, when it is determined that the torque is low in the twin turbo state, the mode is switched to the twin turbo state. It is an object of the present invention to provide a method for controlling an engine with a supercharger, which can stop the operation and improve drivability.

[0008]

In order to achieve the above object, a method of controlling an engine with a supercharger according to the present invention includes a primary turbocharger and a secondary turbocharger arranged in parallel in an intake and exhaust system of the engine. And the intake and exhaust systems connected to the secondary turbocharger are respectively provided with an intake control valve and an exhaust control valve, and both control valves are fully opened in a high speed range to open both turbochargers. Engine operation in the twin turbo region where both supercharge operations are performed, and the single turbo region where only the primary turbocharger is supercharged by closing the intake control valve and closing or opening the exhaust control valve in the low speed range. The regions are divided and the operating region is switched from the single turbo region to the single-twin switching determination line that is set based on the engine operating condition and the single-twin switching determination line that is set by the determination value. After shifting to the turbo range, fully open the exhaust control valve after the set time elapses, and then open the intake control valve to change the turbocharger from the single turbo state where only the primary turbocharger is operating. After switching to the twin-turbo state by operation, the engine operating area transitions from the twin-turbo area side to the single-turbo area on the boundary of the twin-to-single switching judgment line set on the lower rotation speed side than the single-to-twin switching judgment line, In a method of controlling an engine with a supercharger, in which both the exhaust control valve and the intake control valve are closed to switch from the twin turbo state in which both turbochargers are supercharged to the single turbo state in which only the primary turbocharger is supercharged , Between the single → twin switching judgment line and the twin → single switching judgment line, the single → twin switching judgment line When a single-to-twin switching determination stop line with a narrow interval is set, and the engine operating range crosses the single-to-twin switching determination stop line to the single turbo region side before the above set time elapses, the twin-turbo state is set. It is characterized in that the switching to is stopped.

[0009]

In the control method for the engine with a supercharger, the engine operating range is such that the single-to-twin switching determination line for determining the switching from the single turbo mode to the twin turbo mode is switched from the single turbo range to the twin turbo range. After the transition, before the set time elapses, between the single → twin switching determination line and the twin → single switching determination line for determining the switching from the twin turbo state to the single turbo state, the single → twin switching is performed. When the single-twin switching determination stop line, which is set to a narrow interval with respect to the determination line, is crossed to the single turbo region side, the switching to the twin turbo state is immediately stopped and the single turbo state is maintained.

[0010]

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

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

As the intake system, intake pipes 16 and 17 branched from the downstream of the air cleaner 15 are connected to blowers 40b and 50b of the turbochargers 40 and 50, respectively.
The intake pipes 18 and 19 from the blowers 40b and 50b are connected to the intercooler 20. And the throttle body 2 which has the throttle valve 21 from the intercooler 20
7 to the chamber 22, and from the chamber 22 to the cylinders of the left and right banks 3 and 4 via the intake manifold 23. Further, as an idle control system, an idle control valve (ISCV) 25 and a check valve 26 that opens by negative pressure are provided in a bypass passage 24 between the downstream side of the air cleaner 15 and the intake manifold 23. It is provided to control.

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

The operation system of the primary turbocharger 40 will be described. The primary turbocharger 40 operates to rotationally drive the blower 40b by the exhaust energy introduced into the turbine 40a to suck and pressurize air to constantly supercharge. A primary wastegate valve 41 having a diaphragm actuator 42 is provided on the turbine side. The blower 40b is provided in the pressure chamber of the actuator 42.
A control pressure passage 44 from immediately downstream of the valve has an orifice 48 and communicates with it so as to open the waste gate valve 41 with good response when the supercharging pressure rises above a set value. Further, the control pressure passage 44 communicates the supercharging pressure with a duty solenoid valve 43 which leaks to the upstream side of the blower 40b, and a predetermined control pressure is generated by the duty solenoid valve 43 to act on the actuator 42, thereby causing a wastegate valve. 41
The supercharging pressure is controlled by changing the opening degree of. Here, the duty solenoid valve 43 is operated by a duty signal from the electronic control unit 100 described later, and when the duty ratio of the duty signal is small, the waste gate valve 4 is operated at a high control pressure.
The supercharging pressure is decreased by increasing the opening degree of 1, and the control pressure is decreased by increasing the leak amount as the duty ratio increases, and the supercharging pressure is increased by decreasing the opening degree of the waste gate valve 41.

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

The operation system of the secondary turbocharger 50 will be described. Similarly, in the secondary turbocharger 50, the turbine 50a and the blower 50b are rotatably driven by exhaust gas to supercharge, and the actuator 52 is attached to the turbine side.
The secondary waste gate valve 51 having the above is provided. The exhaust pipe 10 upstream of the turbine 50a is provided with a downstream opening type exhaust control valve 53 having a diaphragm type actuator 54, and the butterfly type intake control valve having a similar actuator 56 is provided downstream of the blower 50b. 55 is provided, and a supercharging pressure relief valve 57 is provided in a relief passage 58 between the upper side and the lower side of the blower 50b.

The pressure operation system of each of these valves will be described. First, the surge tank 60 of the negative pressure source has a check valve 62
Is communicated with the intake manifold 23 by a passage 61 having a valve for storing negative pressure and buffering pulsating pressure when the throttle valve is fully closed. Further, a switching solenoid valve SOL. For supercharging pressure relief valve that opens and closes the supercharging pressure relief valve 57. 1, intake control valve 55
Intake control valve switching solenoid valve SOL. 2,
The switching solenoid valve SOL. For the first and second exhaust control valves for opening and closing the exhaust control valve 53. 3, SOL. 4, exhaust control valve 5
3 has a duty solenoid valve 75 for controlling small opening and a secondary wastegate switching solenoid valve 70 for opening and closing the secondary wastegate valve 51. Each switching solenoid valve 70, SOL. 1 to 4 are electronic control devices 10
The ON / OFF signal from 0 selects the negative pressure in the negative pressure passage 63 from the surge tank 60, the positive pressure from the positive pressure passages 64a and 64b communicating downstream of the intake control valve, the atmospheric pressure, etc., and each control pressure passage is selected. The actuators 70a to 74a guide the control valve and the secondary wastegate valve 51 to the actuator side. Further, the duty solenoid valve 75 causes the actuator 5 to receive a duty signal from the electronic control unit 100.
The positive pressure acting on the positive pressure chamber 54a of No. 4 is variably controlled, and the exhaust control valve 53 is controlled to a small opening.

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

Intake control valve switching solenoid valve SOL. Two
When turned off, the atmospheric port is closed and the negative pressure passage 63
Side, the actuator 5 is opened via the control pressure passage 72a.
By introducing a negative pressure into the pressure chamber in which the spring 6 is installed, the intake control valve 55 is closed against the biasing force of the spring, and
When N is reached, the negative pressure passage 63 side is closed to open the atmospheric port, and the atmospheric pressure is introduced into the pressure chamber of the actuator 56 to open the intake control valve 55 by the biasing force of the spring in the pressure chamber.

The secondary wastegate switching solenoid valve 70 is turned off only when the electronic control unit 100 determines that high-octane gasoline is used based on the ignition advance amount and the like.
When it is judged that regular gasoline is used, O
N is done. When the secondary wastegate switching solenoid valve 70 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 the atmospheric pressure is introduced into the actuator 52 via the control pressure passage 70a. Then, the secondary waste gate valve 51 is closed by the urging force of the spring arranged in the actuator 52. Further, when turned on, the atmospheric port is closed and the passage 65 side is opened, and the supercharging pressure downstream of the secondary turbocharger 50 when both turbochargers 40, 50 are operating is guided to the actuator 52, and in response to this supercharging pressure. Then, the secondary waste gate valve 51 is opened, and the supercharging pressure is relatively reduced when using regular gasoline as compared to when using high-octane gasoline.

In addition, the first exhaust control valve switching solenoid valve SOL. 3 from the control pressure passage 73a 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. Both switching solenoid valves SOL. When both 3 and 4 are OFF,
The first exhaust control valve switching solenoid valve SOL. In the third exhaust control valve switching solenoid valve SOL.3, the positive pressure passage 64b side is closed to open the atmospheric port. In No. 4, by closing the negative pressure passage 63 side and opening the atmosphere port, both chambers 54a and 54b of the actuator 54 are opened to the atmosphere, and the exhaust control valve 53 is fully closed by the biasing force of the spring installed in the negative pressure chamber 54b. To do. Further, both switching solenoid valves SOL. When both 3 and 4 are ON, the atmosphere port is closed and the first exhaust control valve switching solenoid valve SOL. 3 is a positive pressure passage 64b
Side, the second switching solenoid valve for exhaust control valve SO
L. By opening the negative pressure passage 63 side, 4 guides positive pressure to the positive pressure chamber 54a of the actuator 54 and negative pressure to the negative pressure chamber 54b, and fully opens the exhaust control valve 53 against the biasing force of the spring.

First exhaust control valve switching solenoid valve SO
L. An orifice 67 is provided in the control pressure passage 73a from the No. 3, and a leak passage 66 is connected to the downstream side of the orifice 67 and the intake pipe 16, and the exhaust passage operated by a duty signal from the electronic control unit 100 is connected to the leak passage 66. A duty solenoid valve 75 for controlling the control valve small opening is provided. Then, the first switching solenoid valve SOL. When only 3 is ON and positive pressure is supplied to the positive pressure chamber 54a of the actuator 54 and the negative pressure chamber 54b is opened to the atmosphere, the duty solenoid valve 75 leaks the positive pressure and the exhaust control valve 53 is opened slightly. Here the duty solenoid valve 75
When the duty ratio in the duty signal is large,
By increasing the leak amount, the positive pressure acting on the positive pressure chamber 54a is reduced to reduce the opening degree of the exhaust control valve 53, and as the duty ratio decreases, the positive pressure increases to increase the opening degree of the exhaust control valve 53. Operate. When the engine operating condition is within the predetermined exhaust control valve small open control mode region under the single turbo mode, the boost pressure is feedback controlled by the opening degree of the exhaust control valve 53 by the duty solenoid valve 75, and the boost pressure is controlled. With the control, the exhaust control valve 53 is configured to be opened slightly.

Various sensors will be described. The differential pressure sensor 80 is provided so as to detect the differential pressure upstream and downstream of the intake control valve 55, and the absolute pressure sensor 81 is provided so as to selectively detect the intake pipe pressure and the atmospheric pressure by the switching solenoid valve 76. To be Further, the knock sensor 82 is attached to the engine body 1.
Is attached, 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 supplied with O
2 The sensor 84 is exposed. Further, a throttle sensor 85 having a throttle valve 21 and a throttle opening sensor and an idle switch for detecting the throttle fully closed is built in.
And the intake air amount sensor 86 is arranged immediately downstream of the air cleaner 15.

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

The crank angle sensor 87 and the cam angle sensor 88 detect the projections (or slits) formed at predetermined intervals on the crank rotor 90 and the cam rotor 91, respectively, as the engine is operated, and output the crank pulse and the cam pulse electronically. Output to the control device 100. Then, in the electronic control unit 100, the engine speed is calculated from the interval time of the crank pulse (protrusion detected), and
Ignition timing, fuel injection start timing, etc. are calculated, and cylinder discrimination is performed based on the input patterns of the crank pulse and the cam pulse.

Next, the structure of the electronic control system will be described with reference to FIG. The electronic control unit (ECU) 100 is a CP
The U101, the ROM 102, the RAM 103, the backup RAM 104, and the I / O interface 105 are mainly configured by a microcomputer connected via a bus line, and a constant voltage circuit 106 and a drive circuit 107 for supplying a predetermined stabilizing power supply to each unit are provided. It is incorporated.

The constant voltage circuit 106 is connected to the ECU relay 9
The relay coil of the ECU relay 95 is connected to the battery 96 via an ignition switch 97. Further, the battery 96 includes the constant voltage circuit 10
6 is directly connected, and further, the fuel pump 31 is connected via a relay contact of the fuel pump relay 98. That is, the constant voltage circuit 106 supplies control power to each part when the ignition switch 97 is turned on and the relay contact of the ECU relay 95 is closed,
Further, when the ignition switch 97 is turned off, the backup power source is the backup RAM 104.
Supply to.

Further, the I / O interface 105 is also provided.
Various sensors 80 to 88, vehicle speed sensor 8 at the input port of
9 and the battery 96 are connected. Also, I / O
An igniter 36 is connected to the output port of the interface 105, and further, an IS is connected via a drive circuit 107.
CV25, injector 30, each switching solenoid valve 7
0,76, SOL. 1-4, duty solenoid valve 4
3, 75 and a relay coil of the fuel pump relay 98 are connected.

Then, the ignition switch 97 is turned on.
When turned on, the ECU relay 95 is turned on and the constant voltage circuit 1
A constant voltage is supplied to each unit via 06, and the ECU 100 executes various controls. That is, in the ECU 100, the CPU 101 inputs the detection signals from the various sensors 80 to 89 through the I / O interface 105 based on the arithmetic program stored in the ROM 102, and stores the various signals in the RAM 103 and the backup RAM 104. Various control variables are calculated based on the data and the fixed data stored in the ROM 102. Then, the drive circuit 107 turns on the fuel pump relay 98 to energize and drive the fuel pump 31, and the drive circuit 1
07, each switching solenoid valve 70, 76, SOL.
The ON / OFF signals are output to 1 to 4 and the duty signals are output to the duty solenoid valves 43 and 75 to perform the turbocharger operation number switching control and the supercharging pressure control, and the drive pulse width corresponding to the calculated fuel injection amount. A signal is output to the injector 30 of the corresponding cylinder at a predetermined timing to perform fuel injection control, an ignition signal is output to the igniter 36 at a predetermined timing to perform ignition timing control, and a control signal is output to the ISCV 25. To perform idle speed control, etc.

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

When the ECU 100 is powered on by turning on the ignition switch 97, the system is initialized (clearing each flag and each count value), and first, at step S1, the twin turbo mode discrimination flag F1.
Refer to the value of. If the twin turbo mode discrimination flag F1 is cleared, the process proceeds to step S2,
If it is set, the process proceeds to step S60. The twin turbo mode determination flag F1 is cleared when the current control state is the single turbo mode in which only the primary turbocharger 40 is supercharged.
It is set in the twin turbo mode in which 50 is supercharged.

In the following description, the single turbo mode will be described first, and then the single-to-twin switching control,
Finally, the twin turbo mode will be described. Immediately after the ignition switch 97 is turned on and when the current control state is the single turbo mode, since F1 = 0, the process proceeds to step S2.

In step S2, a single-to-twin switching determination value Tp2 is set by referring to the turbo switching determination value table with interpolation calculation based on the engine speed N. As shown in FIG. 8, in the turbo switching determination value table, single-turbo mode is switched to twin-turbo mode from the relationship between the engine speed N and the engine load (basic fuel injection pulse width in this embodiment) Tp. The twin switching determination line L2 and, conversely, the twin-to-single switching determination line L1 for switching from the twin turbo mode to the single turbo mode are previously obtained through experiments or the like, and the single turbo region and the twin turbo region are set. The single-to-twin switching determination value Tp2 and the twin-to-single switching determination value T are respectively associated with the lines L2 and L1.
p1 is stored in advance in a series of addresses in the ROM 102 as a table with the engine speed N as a parameter. Note that the single-to-twin switching determination line L2 is set at a point C where the torque curve TQ1 during single turbo and the torque curve TQ2 during twin turbo having the output characteristics of FIG. 13 coincide with each other in order to prevent torque fluctuation during switching. Therefore, as shown in FIG. 8, it is set to a low load side from a high load in the low and medium rotation speed range to an 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 turbocharger operating number, the twin → single switching determination line L1 is relatively on the low rotation speed side with respect to the single → twin switching determination line L2. It is set with a wide hysteresis H.

Then, in step S3, the single-to-twin switching determination value Tp2 is compared with the current basic fuel injection pulse width (hereinafter referred to as engine load) Tp, and Tp <Tp2
In the case of, the process proceeds to step S4 and the single turbo mode control is performed. If Tp ≧ Tp2, step S
Proceed to 30, and perform single-> twin switching control.

From step S3 to step S4,
The value of the supercharging pressure control mode determination flag F2 is referred to. The supercharging pressure control mode determination flag F2 indicates that the current operating region is within the exhaust control valve small opening control mode region in which the supercharging pressure control is performed by the small opening of the exhaust control valve 53 and the secondary turbocharger 50 is preliminarily rotated. Set when, and cleared when out of range.

Therefore, the ignition switch 97 is turned on.
Immediately after N, the initial setting is performed, and when the operating region is outside the exhaust control valve small open control mode region during the execution of the previous routine, F2 = 0, so the process proceeds to step S5, and the current determination is made according to the condition determination in steps S5 to S7. It is determined whether the operating region has moved into the exhaust control valve small open control mode region.

As shown in FIG. 9, the 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. On the low rotation / low load side of L2, that is, in the single turbo mode, the set value N1 (for example, 265
0 rpm) and P1 (for example, 1120 mmHg), and when the throttle opening TH is equal to or larger than the set value TH1 (for example, 30 deg), it is determined that the shift has occurred within the region.

That is, the engine speed N is compared with the set value N1 in step S5, the intake pipe pressure P is compared with the set value P1 in step S6, and the throttle opening TH and the set value TH1 are compared with each other in step S7. Compare. And N <N
If 1, or P <P1, or TH <TH1, the process proceeds to step S8, it is determined that the current operation region is outside the exhaust control valve small open control mode region, and the supercharging pressure control mode determination flag F2 is cleared, Also, N ≧ N1 and P ≧ P1 and TH
When ≧ TH1, the process proceeds to step S9, and it is determined that the current operation region has shifted to the exhaust control valve small open control mode region, and the supercharging pressure control mode determination flag F2 is set.

Then, the routine proceeds to step S10, where the supercharging pressure relief valve switching solenoid valve SOL. 1 is turned off, and in step S11, the intake control valve switching solenoid valve SOL.
Turn off 2. Next, proceeding to step S12, referring to the value of the supercharging pressure control mode determination flag F2, if F2 = 0, proceeding to step S13, the first exhaust control valve switching solenoid valve SOL. 3 is turned off, and the second exhaust control valve switching solenoid valve SOL. 4 OF
F Then, in steps S15 to S17, the twin turbo mode determination flag F1, the differential pressure search flag F3, which will be described later, and the control valve switching time count value C1 are respectively cleared, and then the routine exits.

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

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

When in the single turbo mode and outside the exhaust control valve small open control mode region, or in the twin turbo mode, the boost pressure feedback control is
Although not detailed here, the primary waste gate valve 41
Done using only.

On the other hand, if it is determined in step S9 that the current operation region is within the exhaust control valve small open control mode region and the supercharging pressure control mode determination flag F2 is set, steps S10 to S12 are performed. In step S18, the first exhaust control valve switching solenoid valve SOL. O only 3
N Therefore, the first exhaust control valve switching solenoid valve S
OL. 3 is turned on, the positive pressure chamber 54 of the actuator 54
Positive pressure is introduced to a and the exhaust control valve 53 is opened. In this exhaust control valve small open control mode, the exhaust control valve small open control routine shown in FIG.
Every msec), the boost pressure feedback control is performed by using the exhaust control valve 53, and the exhaust control valve 53 is opened slightly accordingly. That is, in FIG.
In step S100, the value of the supercharging pressure control mode determination flag F2 is referred to. When F2 = 0, the routine exits and F2
= 1 and the exhaust control valve small open control mode, step S1
01, switching solenoid valve SO for boost pressure relief valve
L. 1 is determined and the SOL. When 1 = ON, the routine is exited and SOL. When 1 = OFF, the routine proceeds to step S102, where the target boost pressure and the absolute pressure sensor 81
Is compared with the actual supercharging pressure detected by, and the ON duty (duty ratio) for the exhaust control valve small opening control duty solenoid valve 75 is calculated by PI control, for example, according to the comparison result. The duty signal is output to the duty solenoid valve 75, and the boost pressure feedback control is executed. Therefore, the duty solenoid valve 75 causes the positive pressure chamber 5 of the actuator 54 to
The positive pressure acting on 4a is regulated, and as shown in FIG.
The exhaust control valve 53 is opened slightly, and the boost pressure feedback control is performed using only the exhaust control valve 53. Then, a part of the exhaust gas is supplied to the turbine 50a of the secondary turbocharger 50 by the small opening of the exhaust control valve 53, the secondary turbocharger 50 is preliminarily rotated, and the twin turbo transition is prepared.

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

In the single turbo mode, the boost pressure control mode discrimination flag F is set in the exhaust control valve small open control mode region.
When 2 is set (F2 = 1), the process proceeds from step S4 to step S19, and whether the current operating region has moved out of the exhaust control valve small open control mode region according to the condition determination of steps S19 to S21. Is judged.

In order to prevent the control hunting at the time of switching the boost pressure control mode, the determination of the shift to the outside of this area is performed as shown in FIG. 9, and the set value N2 lower than the set values N1, P1 and TH1 is set. (For example, 2600 rpm), P2 (for example, 1070 mmHg), and TH2 (for example, 25 deg). Then, in step S19, the engine speed N and the set value N2 are compared, and in step S20, the intake pipe pressure (supercharging pressure) P1 and the set value P2 are compared, and step S2
At 1, the throttle opening TH is compared with the set value TH2, and N
<N2 or P <P2 or TH <TH2,
It is determined that the current operation region has moved to the outside of the exhaust control valve small open control mode region, and the routine proceeds to step S8, where the supercharging pressure control mode determination flag F2 is cleared. As a result, the exhaust control valve small opening control is released. In addition, N ≧ N2 and P ≧ P
In the case of 2 and TH ≧ TH2, it is determined that the current operation region is still within the region, the process proceeds to step S9, and the supercharging pressure control mode determination flag F2 is held in the state of F2 = 1,
Exhaust control valve small open control is continued.

As described above, in the single turbo mode, most of the exhaust gas from the engine body 1 is introduced into the primary turbocharger 40 and the turbine 40a rotationally drives the blower 40b. Then, the blower 40b sucks and compresses the air, and the compressed air is supplied to the intercooler 2
It is cooled at 0, the flow rate is adjusted by the opening degree of the throttle valve 21, and is supplied to each cylinder through the chamber 22 and the intake manifold 23 with high filling efficiency to perform supercharging. And
In the single turbo mode in which only the primary turbocharger 40 operates in the single turbo mode, as shown in the output characteristic of FIG. 13, a torque curve TQ1 at the time of single turbo with high axial torque in the low and medium rotation speed regions is obtained. .

Next, the single-to-twin switching control will be described. If it is determined in step S3 that Tp ≧ Tp2, that is, the current operating region has shifted from the single turbo region to the twin turbo region (see FIG. 8), the process branches to step S30 and only the primary turbocharger 40 is operated. A single-to-twin switching control for switching from the single turbo state to the twin turbo state in which both turbochargers 40 and 50 are operated is executed.

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

Therefore, the supercharging pressure relief valve 57 is connected to the supercharging pressure relief valve switching solenoid valve SOL. When 1 is turned on, the positive pressure from the positive pressure passage 64a is introduced into the pressure chamber,
The valve is immediately closed by this positive pressure and the biasing force of the spring. Further, the exhaust control valve 53 includes a first exhaust control valve switching solenoid valve SOL. Actuator 5 when 3 is turned on
The positive pressure is introduced into the positive pressure chamber 54a of No. 4 to open the valve.
When the exhaust control valve small open control mode under the single turbo mode is switched to the single → twin switching control, the boost pressure relief valve switching solenoid valve SOL.
When the exhaust control valve small open control routine of FIG. 7 is turned on by exiting the routine through step S101 without performing the supercharging pressure feedback control, the supercharging pressure feedback control by the exhaust control valve 53 is stopped. ,
The exhaust control valve small opening control duty solenoid valve 75 is fully closed, and the positive pressure through the positive pressure passage 64b is directly introduced into the positive pressure chamber 54a of the actuator 54 without being leaked by the duty solenoid valve 75. The opening degree of the exhaust control valve 53 is increased.

The relief passage 58 is closed by closing the supercharging pressure relief valve 57, and the rotation speed of the secondary turbocharger 50 is increased by opening the exhaust control valve 53 and increasing its opening. At the same time, the supercharging pressure between the downstream of the blower 50b of the secondary turbocharger 50 and the intake control valve 55 is gradually increased to prepare for the transition to the twin turbo mode. In step S34, the differential pressure search flag F
By referring to the value of 3, if F3 = 0, the process proceeds to step S35, and if F3 = 1, the process jumps to step S39.

At the time of executing the routine for the first time after shifting to the single-to-twin switching control, since F3 = 0, step S
35, first, referring to the exhaust control valve open delay time setting table based on the vehicle speed V with interpolation calculation, fully open control of the exhaust control valve 53 after the transition from single to twin switching control (for the second exhaust control valve) Switch solenoid valve SOL.4 to O
The exhaust control valve opening delay time T1 that determines the timing (from FF to ON) is set, and the intake control valve opening delay time setting table is referenced with interpolation calculation based on the vehicle speed V in step S36, and the exhaust control valve 53 After the full open control, the intake control valve 55 is opened (intake control valve switching solenoid valve SO
L. (Turn 2 from OFF to ON) Set the intake control valve opening delay time T2 for determining the condition of the start timing. Further, in step S37, the upstream pressure PU of the intake control valve 55
Differential pressure between the downstream pressure PD and the downstream pressure PD (read value of the differential pressure sensor 80) D
The intake control valve opening differential pressure DPSS for determining the valve opening control start timing of the intake control valve 55 based on PS (= PU-PD)
Set T.

FIG. 10A shows a conceptual diagram of the exhaust control valve opening delay time setting table, and FIG. 10B shows a conceptual diagram of the intake control valve opening delay time setting table. As shown in the figure, as the vehicle speed V is higher, the exhaust control valve open delay time T1 and the intake control valve open delay time T2 are shortened to fully open the exhaust control valve 53 and the intake control valve 5
5 is opened, that is, the timing of switching to the twin turbo mode is advanced so that the acceleration responsiveness is made uniform regardless of the vehicle speed and the drivability is improved.

Further, FIG. 10C shows a conceptual diagram of the intake control valve opening differential pressure setting table. As shown in the figure, the differential pressure immediately after the engine operating state shifts from the single turbo region to the twin turbo region (see FIG. 8) with the single → twin switching determination line L2 (single → twin switching determination value Tp2) as a boundary. The intake control valve opening differential pressure DPSST increases as the DPS decreases toward the negative side, that is, the downstream pressure PD is higher than the upstream pressure PU of the intake control valve 55 and the supercharging state is high.
Is set to the minus side to accelerate the timing of opening the intake control valve 55 and improve the acceleration response.

After setting the delay times T1 and T2 and the intake control valve opening differential pressure DPSST, the process proceeds to step S38, the differential pressure search flag F3 is set, and the process proceeds to step S39. In step S39, the second exhaust control valve switching solenoid valve SOL. No. 4, the exhaust control valve 53 has already started to be fully opened, and the SOL. 4 = ON, and when the exhaust control valve fully open control has already been started, the routine jumps to step S47, and the second exhaust control valve switching solenoid valve SOL. 4 is kept ON, and SOL. Four
= OFF, the exhaust control valve fully open control has not yet been executed, so the routine proceeds to step S40, where the control valve switching time count value C1 is compared with the exhaust control valve open delay time T1.
It is determined whether the exhaust control valve opening delay time T1 has elapsed after the transition from the single-to-twin switching control.

If C1 ≧ T1, the process jumps to step S45 and the second exhaust control valve switching solenoid valve SOL. 4 is turned on and the exhaust control valve 53 is fully opened. When the delay time C1 <T1 has not yet elapsed, the routine proceeds to step S41, where the engine load Tp is compared with the value obtained by subtracting the set value WGS from the single-to-twin switching determination value Tp2 set in step S2, and Tp <Tp2
In the case of WGS, the process returns to step S8 to stop the single-to-twin switching control and immediately switch to the single turbo mode. This is to eliminate the uncomfortable feeling of driving by returning to the single turbo mode when the engine load Tp drops.

More specifically, as shown in FIG. 8, once the engine operating state exceeds the single → twin switching determination line L2 (Tp2) from the single turbo region to the twin turbo region side, the twin → single switching determination line is reached. L
Unless 1 (Tp1) is exceeded on the single turbo region side,
After the delay time T1 has elapsed, the exhaust control valve 53 is fully opened (step S45), and if the differential pressure DPS reaches the intake control valve opening differential pressure DPSST after the delay time T2 has elapsed, the intake control valve 55 opens (step S49), and the twin Switch to turbo mode. Therefore, if the operating state remains in the area surrounded by the twin-single switching determination line L1 and the single-twin switching determination line L2 once the single-twin switching determination line L2 is crossed, the delay time elapses. It will be switched to the twin turbo state.
However, in this region, as shown in FIG. 13, with respect to the axial torque (for example, point A in the figure) in the single turbo given by the torque curve TQ1, the secondary turbocharger 50 is provided.
The axial torque (point B in the figure) of the torque curve TQ2 at the time of twin turbo due to the operation becomes rather low, and when switching from the single turbo state to the twin turbo state, a sudden decrease in torque causes a torque shock and the driver feels uncomfortable. Will give.

To deal with this, the twin → single switching determination line L1 is changed to the single → twin switching determination line L1.
It is sufficient to narrow the width (hysteresis) of both switching lines closer to 2, but if the width between both switching lines L1 and L2 is narrowed, the switching frequency between single turbo and twin turbo increases and each control valve is activated. Since the negative pressure capacity of the surge tank 60 as a negative pressure source is insufficient, the surge tank 60
If the operating condition remains near the single-to-twin switching determination line L2 if the above-mentioned width is too narrow, the engine load Tp, which is a parameter for switching the turbocharger operating number, may vary. However, there is a problem that the boost pressure relief valve 57 for which the switching delay time is not set causes chattering.

In order to prevent these, the operating condition is single →
After the twin switching determination line L2 is crossed to the twin turbo region side and before the delay time T1 has elapsed, the single-to-twin switching determination line has a narrower interval and the set value WGS is subtracted to the single turbo region side, which is indicated by a broken line in FIG. Single →
When the twin switching determination stop line L3 (= Tp2-WGS) is crossed to the single turbo region side, the single → twin switching control for switching to the twin turbo state is stopped and the single turbo mode is immediately changed to the primary turbocharger. By maintaining the single turbo state in which only 40 is operated (the transition from point A to point B in FIG. 13 is stopped), the operation in the low torque region in the twin turbo state is eliminated and the drivability is improved. Try.

On the other hand, in step S41, Tp ≧ Tp2-W
In the case of GS, the process proceeds to step S42, and after the shift from single to twin switching control, before the delay time T1 elapses, the high load determination value TpH for determining whether the engine operating state has shifted to the high load and high speed range is set. Based on the number N, the high load judgment value table is referenced with interpolation calculation and set.

FIG. 10D shows a conceptual diagram of the high load judgment value table. Fuel injection pulse width (engine load) Tp
Is calculated by Tp = K × Q / N K: constant, Q: intake air amount, and when the intake air amount Q is constant at high load, the fuel injection pulse width (engine load) Tp is the engine speed N Inversely proportional to. Therefore, as shown in the figure, the high load determination value TpH is set to a lower value as the engine speed N is higher.

Next, at step S43, the engine load T
p and the high load judgment value TpH are compared, and Tp ≦ TpH
In this case, the process proceeds to step S44, the control valve switching time count value C1 is incremented, and the routine is exited.
On the other hand, if Tp> Tph and it is determined that the engine operating state has transitioned to the high load / high speed region before the delay time T1 has elapsed (e.g., in the case of sudden acceleration, racing, etc.), step S45. To 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 also flown to the secondary turbocharger 50 side to prevent surging of the primary turbocharger 40 due to reaching a critical rotation speed due to a rapid increase in exhaust flow rate. , To prevent damage to the primary turbocharger 40.

When the exhaust control valve opening delay time T1 elapses after the transition to the single-to-twin switching control and the process proceeds from step S40 or from step S43 to step S45, the second exhaust control valve switching solenoid valve SOL. 4, the exhaust control valve 53 is fully opened, the rotation speed of the secondary turbocharger 50 is further increased, and the blower 50b is rotated.
Secondary turbocharger 50 between the intake control valve 55 and the
As a result, the compressor pressure (supercharging pressure) also rises, and as shown in FIG. 11, 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 S46, 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 S47.

When the process proceeds from step S39 or step S46 to step S47, the count value C1 representing the time after the exhaust control valve full-open control (SOL.4 OFF → ON) is compared with the intake control valve open delay time T2. ,
If C1 <T2, it is determined that the intake control valve 55 valve opening condition is not satisfied, and the count value C1 is determined in step S44.
Count up and exit the routine. Also C1 ≧ T
In the case of 2, it is determined that the valve opening condition is satisfied, and step S48 is performed.
To the present differential pressure DPS and intake control valve opening differential pressure DPSS.
By comparing with T, it is judged whether or not the opening start timing of the intake control valve 55 has been reached.

When DPS <DPSST, it is judged that the valve opening start timing has not been reached, and the routine exits and D
When PS ≧ DPSST, the upstream pressure PU of the intake control valve 55
And the downstream pressure PD become substantially equal, that is, the supercharging pressure by the secondary turbocharger 50 between the blower 50b of the secondary turbocharger 50 and the intake control valve 55 increases, and the primary turbocharger 40. Becomes substantially equal to the supercharging pressure due to, and it is judged that the intake control valve opening start timing has been reached, and the routine proceeds to step S49, where the intake control valve switching solenoid valve SO
L. 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 S50, and when the single-twin switching control is completed, the twin turbo mode determination flag F1 is set next time to shift to the twin turbo mode, and the routine is exited. The time chart of FIG. 11 shows the switching state from the single turbo mode to the twin turbo mode by the above single → twin switching control.

As described above, in the single-to-twin switching control, first, the boost pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and the preliminary rotation speed of the secondary turbocharger 50 is adjusted. The exhaust control valve opening delay time T1 gives the time required to increase the preliminary rotation speed of the secondary turbocharger 50, and then the exhaust control valve 53 is fully opened after the delay time T1 has elapsed. Then, the supercharging pressure by the secondary turbocharger 50 between the blower 50b of the secondary turbocharger 50 and the intake control valve 55 rises, the differential pressure DPS rises, and after the exhaust control valve fully open control, the intake control valve open delay. Exhaust control valve 5 depending on time T2
3 is compensated for the operation delay time until the valve 3 is fully opened, and after the delay time T2 elapses, the intake control valve 55 is reached when the differential pressure DPS between the upstream side and the downstream side of the intake control valve 55 reaches the intake control valve open differential pressure DPSST. Open. As a result, the switching from the single turbo state in which only the primary turbocharger 40 is operating to the twin turbo state in which both turbochargers 40 and 50 are operating is performed smoothly, and further, the intake control valve 55
When the upstream pressure PU and the downstream pressure PD become substantially equal to each other, the intake control valve 55 is opened to start supercharging from the secondary turbocharger 50. The occurrence of torque shock due to a temporary decrease in supply pressure is effectively and surely prevented.

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

Then, in step S60, the twin-to-single switching determination value Tp1 is set by referring to the turbo switching determination value table with interpolation calculation based on the engine speed N (see FIG. 8), and the routine proceeds to step S61, where the engine Load Tp
And the twin-single switching judgment value Tp1 above,
If Tp ≧ Tp1, the current operating state is the twin turbo region, so the determination value search flag F4 is cleared in step S62, and the single turbo region duration after the transition to the single turbo region is counted in step S63. After clearing the turbo region duration time count value C2, the routine jumps to step S72, and in step S72 to step S75, the boost pressure relief valve switching solenoid valve SOL. 1, intake control valve switching solenoid valve SO
L. 2, switching solenoid valve S for the first and second exhaust control valves
OL. Turn on 3 and 4 respectively, and boost pressure relief valve 5
7 is closed and both the intake control valve 55 and the exhaust control valve 53 are fully opened, the twin turbo mode determination flag F1 is set in step S76, the process returns to step S17, and the control valve switching time count value C1 is cleared. After that, exit the routine.

In this twin turbo mode, by closing the supercharging pressure relief valve 57, opening the intake control valve 55, and fully opening the exhaust control valve 53, in addition to the primary turbocharger 40, a secondary turbocharger is provided. 50 becomes a full-scale operation, becomes a twin turbo state due to supercharging operation of both turbochargers 40, 50, compressed air due to supercharging of both turbochargers 40, 50 is supplied to the intake system, and output characteristics of FIG. As shown in, a torque curve TQ2 at the time of twin turbo with a high axial torque in a high rotation speed range is obtained.

On the other hand, in step S61, Tp <Tp
1, that is, when it is determined that the current operating state has shifted to the single turbo region (see FIG. 8), the process proceeds to step S64, the value of the determination value search flag F4 is referred to, and when F4 = 0, the process proceeds to step S65. If F4 = 1, the process jumps to step S67.

The judgment value search flag F4 is cleared in the twin turbo mode and when the engine load Tp is in the twin turbo region with the twin-to-single switching judgment line L1 (Tp1) as a boundary (step S).
62). Therefore, after Tp <Tp1, when executing the routine for the first time, the process proceeds to step S65, and the single turbo region continuation time determination value T is referred to by referring to the single turbo region continuation time determination value table with interpolation calculation based on the engine load Tp.
Set 4. The set value T4 is a reference value for switching to the single turbo mode in which only the primary turbocharger 40 operates after a predetermined time has elapsed after the engine operating state transitions from the twin turbo region to the single turbo region.

FIG. 10 (e) shows a conceptual diagram of the single turbo region continuation time judgment value table. Single turbo region continuation time determination value T set according to the engine load Tp
For example, 4 is set to 2.3 sec at maximum and 0.6 sec at minimum, and is set to a smaller value as the engine load Tp is larger and the load is higher. As a result, after the engine operating state shifts from the twin turbo region to the single turbo region, the time until switching from the twin turbo mode to the single turbo mode is made faster as the engine load is higher,
In the twin-turbo state, the operation in the low axial torque part is prevented and the re-acceleration performance is improved.

Next, after the judgment value search flag F4 is set in step S66, the process proceeds to step S67. Then, in step S67, the single turbo region duration time count value C2 is counted up, and then in step S68, the determination value T4 and the count value C2 are compared, and C2 ≧ T4.
In this case, the process proceeds to step S71, the count value C2 is cleared, and then the process returns to step S8 to switch from the twin turbo mode to the single turbo mode. As a result, each switching solenoid valve SOL. 1 to 4 are turned off, the supercharging pressure relief valve 57 is opened, and both the intake control valve 55 and the exhaust control valve 53 are closed, whereby both turbochargers 40,
The twin turbo state of 50 operation is switched to the single turbo state of only the primary turbocharger 40 operating.

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

On the other hand, if C2 <T4, step S69.
The throttle opening TH and the set value TH3 (for example, 3
0 deg), and if TH> TH3, the process returns to step S8 through the above step S71, and after the engine operating region shifts to the single turbo region, even before that state continues for the set time, FIG. As shown by the broken line, the mode is immediately switched to the single turbo mode, the boost pressure relief valve 57 is opened, and the exhaust control valve 53 and the intake control valve 55 are both closed, so that the secondary turbocharger 50
The supercharging operation is stopped, and only the primary turbocharger 40 is switched to the supercharging single turbo 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. 13, the twin → single switching determination line L1 is on the low rotation side, and in the region where the axial torque of the torque curve TQ2 during twin turbo is low. Therefore, if the twin turbo mode is maintained and the twin turbo state is maintained in this state, sufficient acceleration performance cannot be obtained even when the accelerator pedal is depressed. Therefore, when operating in this region, when it is determined that acceleration is required (TH> TH3), the single turbo mode is immediately set to the single turbo state, and the torque curve TQ1 of the high shaft torque during the single turbo is set. By obtaining, the acceleration response is improved.

In step S69, TH≤TH3
In the case of, the process proceeds to step S70, the vehicle speed V is compared with a set value (for example, 2 Km / h), and when it is determined that the vehicle is traveling with V> V2, the process proceeds to step S72 and the twin turbo mode is maintained. If V ≦ V2, it is determined that the vehicle is in a stopped state. Then, similarly to the above, the process returns to step S8 through step S71 and immediately shifts to the single turbo mode.

The set value V2 is used to determine the stopped state of the vehicle. When the vehicle is stopped, for example, when the engine is idling and the accelerator is depressed to idle the engine, the engine load Tp increases and the engine load increases. The engine speed T rises, the engine operating region shifts from the single turbo region to the twin turbo region and becomes a twin turbo state, and the engine load Tp and the engine rotational speed N immediately decrease after the accelerator is released, and the engine speed T decreases. When the operating region shifts again to the single turbo region with the twin-to-single switching determination line L1 (see FIG. 8) as a boundary, after switching to the single turbo region, if the set time does not elapse (C2 ≧ T4), the single turbo mode is switched to. However, during this period, the engine speed N decreases and is close to the idle speed (for example, 700 rpm).
(In the vicinity), each switching solenoid valve SOL. 1
4 to 4 are performed, and the supercharging pressure relief valve 57 and the control valves 53 and 55 are switched. At this time, since the engine speed N is low, the background noise due to the engine rotation is low, and the driver hears the noise generated when the valves are switched, which gives the driver discomfort. Therefore, when it is determined that the vehicle is in the stopped state (V ≦ V2), the engine speed is immediately switched to the single turbo mode even if the set time has not elapsed after shifting to the single turbo region (C2 <T4). The switching of each valve is completed before the number decreases and the background noise decreases, and the discomfort caused by the noise of the valve operation is eliminated. Note that the switching state from the twin turbo mode to the single turbo mode at this time is shown by a dashed line in FIG.

In this embodiment, the single-twin switching determination stop line L3 is set by a value obtained by subtracting the set value WGS from the single-twin switching determination value Tp2 (single-twin switching determination line L2). The engine speed N and the engine load T are not limited to these values.
You may make it set by the table value which made p and a parameter. It can also be applied to engines other than horizontally opposed engines.

[0081]

As described in detail above, according to the present invention, a single-to-twin switching determination line for determining whether the engine operating region is switched from the single turbo state to the twin turbo state is provided. After shifting to the area side and before the set time elapses, the single → twin switching judgment line and the twin for judging switching from the twin turbo state to the single turbo state →
When the single-to-twin switching judgment stop line, which is narrower than the above-mentioned single-to-twin switching judgment line between the single-switching judgment line and the single-turbo area, is immediately switched to the twin-turbo state. Since it is canceled and maintained in the single-turbo state, when switching from the single-turbo state to the twin-turbo state, if the engine operating range is lower than the torque in the single-turbo state, the twin Switching to the turbo state is canceled.

Therefore, by stopping the switching to the twin-turbo state in this region, the torque shock due to the sudden torque decrease due to the switching is eliminated, the discomfort to the driver can be eliminated, and the shaft torque in this region is reduced. The drivability is improved by maintaining the high single turbo state.

[Brief description of drawings]

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

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

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

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

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

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

FIG. 7 is a flowchart showing an exhaust control valve small opening control routine.

FIG. 8 is an explanatory diagram showing each switching determination value and a relationship between a single turbo region and a twin turbo region.

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

10A is an exhaust control valve opening delay time setting table, FIG. 10B is an intake control valve opening delay time setting table, FIG. 10C is an intake control valve opening differential pressure setting table, and FIG. Value table, (e) is a conceptual diagram showing a single turbo region duration determination value table, respectively.

FIG. 11 is a time chart showing a switching state from single turbo mode to twin turbo mode.

FIG. 12 is a time chart showing a switching state from twin turbo mode to single turbo mode.

FIG. 13 is an explanatory diagram showing output characteristics during single turbo and during twin turbo.

[Explanation of symbols]

 40 Primary turbo supercharger 50 Secondary turbo supercharger 53 Exhaust control valve 55 Intake control valve 57 Supercharging pressure relief valve 100 Electronic control unit (ECU) Tp2 Single → Twin switching judgment value L1 Twin → Single switching judgment line L2 Single → Twin switching judgment line L3 Single → Twin switching judgment stop line T1 Exhaust control valve open delay time (setting time)

Claims (1)

[Claims] 1. A primary turbocharger (40) and a secondary turbocharger (50) are arranged in parallel in an intake system and an exhaust system of an engine, and an intake system connected to the secondary turbocharger (50), An intake control valve (55) and an exhaust control valve (53) are provided in the exhaust system, respectively, and both control valves (5
5, 53) are fully opened together and both turbochargers (40,
50), the intake control valve (55) is closed and the exhaust control valve (5)
5) The engine operating region is divided into a single turbo region in which only the primary turbocharger (40) is supercharged by closing or small opening the primary turbocharger (40), and a single-to-twin switching determination is set based on the engine operating state. Single → twin switching judgment line (L2) set by the value (Tp2)
After the operating region has shifted from the single turbo region to the twin turbo region, the exhaust control valve (53) is fully opened after a lapse of a set time (T1), and then the intake control valve (5
5) is opened and only the primary turbocharger (40) is changed from the single turbo state of supercharging operation to both turbochargers (4).
0,50) Switch to twin turbo state by supercharging operation,
Exhaust control after the engine operating range shifts from the twin-turbo region side to the single-turbo region on the boundary of the twin-to-single switching determination line (L1) set at a lower rotational speed side than the single-to-twin switching determination line (L2). Valve (53)
And the intake control valve (55) are both closed to switch from the twin turbo state of both turbochargers (40, 50) to the single turbo state of only the primary turbocharger (40). In the control method of the engine with a feeder, in the single → twin switching determination line (L2) and the twin → single switching determination line (L1), a single narrow gap is provided between the single → twin switching determination line (L2). → Set the twin switching determination stop line (L3), and before the set time (T1) elapses, the engine operating area is the single → twin switching determination stop line (L3).
The method for controlling an engine with a supercharger is characterized in that switching to the twin turbo state is stopped when the value exceeds the single turbo range.