JP2600851Y2 - Engine with turbocharger - Google Patents

Description

[Detailed description of the invention]

[0001] The present invention is, intake of the engine, exhaust system arranged and flop Lai <br/> Maritabo turbocharger and secondary turbocharger in parallel, the secondary turbocharger side of the intake, distribution in the exhaust system More specifically, the present invention relates to a supercharged engine that controls the supercharging operation of a secondary turbocharger by opening and closing an intake control valve and an exhaust control valve provided. It relates to chattering noise reduction measures.

[0002]

BACKGROUND OF THE INVENTION engine intake, and a flop Raimaritabo turbocharger and secondary turbocharger in the exhaust system are arranged in parallel,
An intake control valve and an exhaust control valve are respectively arranged in the intake and exhaust systems connected to the secondary turbocharger, and both control valves are closed when the engine operation range is in a low speed range, so that the secondary turbocharger is closed. By stopping the supercharging operation and supercharging only the primary turbocharger, and in the high-speed range, both the control valves are fully opened to supercharge both turbochargers, so that the turbocharger operates from the low-speed range to the high-speed range. There is known a supercharged engine capable of improving output performance over a wide range. Here the exhaust control valve, be configured to flapper type downstream opening with an emphasis on response and the like at the valve opening time has been proposed by the present applicant (Japanese
See JP-A-5-156555) .

[0003] The exhaust control valve is provided with an actual opening 2-2.
As disclosed in Japanese Patent No. 2618, it is necessary to provide a play between the arm and the valve body in order to secure the sealing performance by absorbing the thermal expansion and aging of the valve body when fully closed.

[0004]

Therefore, when the valve opening is small and the pressure receiving area of the valve body is large, there is play between the arm and the valve body, so that the valve body dances due to exhaust pulsation, especially the valve body. Immediately before the closing of the valve, the valve body may vibrate and collide with the valve seat to generate a chattering sound (slapping sound).

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a supercharged engine capable of effectively reducing chattering noise of an exhaust control valve configured as a flapper that opens downstream. .

[0006]

In order to achieve the above-mentioned object, an engine with a supercharger according to the present invention has a
An exhaust system arranged a primary turbocharger and a secondary turbocharger in parallel, with both closed in the low-speed range Secondary
Singleter that stops the supercharging operation of the Dali turbocharger
In the high-speed range, and open both valves to operate both turbochargers.
An intake control valve in a twin-turbo state and a flapper-type exhaust control valve that opens downstream are provided in the intake and exhaust systems connected to the secondary turbocharger, respectively. comprising a diaphragm actuator for operating the exhaust control valve and a chamber, disposed the switching solenoid valve for switching the control pressure which acts on the positive pressure chamber and the negative pressure chamber of the actuator, the actuator by the switching solenoid valve both chambers closes the exhaust control valve by air opening, the negative pressure in the negative pressure chamber, in an engine with a supercharger that valve opening the exhaust control valve by supplying a positive pressure to positive pressure chamber , The capacity of the switching solenoid valve is increased from 8 l / min.
Increased set 20l / min, from the switching solenoid valve
The diameter of the passage communicating with each chamber of the actuator is 4 mm
From 6.35 mm .

[0007]

According to the above configuration, the capacity of the switching solenoid valve is set to 8
While increasing the setting from 1 / min to 20 l / min,
An opening / closing operation of the exhaust control valve from the switching solenoid valve.
, The capacity of the switching solenoid valve and the diameter of the passage
When the exhaust control valve is closed , both chambers of the actuator are quickly opened to the atmosphere, and the closing speed of the exhaust control valve is increased. Therefore, even when a large exhaust pulsation acts on the valve body due to an increase in the pressure receiving area when the exhaust control valve is closed, the time at which chattering noise is generated is shortened due to the high valve closing speed of the exhaust control valve. As a result, chattering noise of the exhaust control valve is substantially reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 4 illustrates the overall configuration of the supercharged engine to which the present invention is applied. Reference numeral 1 denotes an engine body of a horizontally opposed engine (a four-cylinder engine in this embodiment), and a combustion chamber 5, an intake port 6, an exhaust port 7, and a spark plug 8 are provided in left and right banks 3, 4 of a crankcase 2. , A valve train 9 and the like. The # 2 and # 4 cylinders are on the left bank 3 side, and the # 1 and # 1 cylinders are on the right bank 4 side.
It has a # 3 cylinder. Also, due to the shortened shape of the engine, immediately after the left and right banks 3 and 4, the primary turbocharger 40
And a secondary turbocharger 50 are respectively provided. As an exhaust system, a common exhaust pipe 10 from the left and right banks 3, 4 is provided with turbines 40a,
The exhaust pipe 11 from the turbines 40a and 50a is joined to one exhaust pipe 12 to communicate with the catalytic converter 1a.
3. It is communicated with the muffler 14.

The primary turbocharger 40 is a small-capacity, low-speed type having a large supercharging capacity in a low to medium speed range, whereas the secondary turbocharger 50 has a large supercharging capacity in a medium to high speed range. High capacity, high speed type. For this reason, the primary turbocharger 40 has a smaller capacity, so that the exhaust resistance increases.

As an intake system, intake pipes 17a, 17b branched into two from an intake pipe 16 connected to an air cleaner 15.
Are blowers 40b of both turbochargers 40 and 50, respectively.
The intake pipes 18 and 19 from the blowers 40 b and 50 b are connected to the intercooler 20. The air is communicated from the intercooler 20 to a chamber 22 via a throttle body 27 having a throttle valve 21, and is communicated from the chamber 22 to each cylinder of the left and right banks 3 and 4 via an intake manifold 23. Further, as an idle control system, the intake pipe 1 immediately downstream of the air cleaner 15 is used.
6 and the bypass passage 24 between the intake manifold 23,
Check valve 2 with idle control valve (ISCV) 25 and negative pressure
6 is provided so as to control the intake air amount during idling or deceleration.

As a fuel system, an injector 30 is provided near a port of the intake manifold 23, and a fuel pump 3
A fuel passage 33 from a fuel tank 32 having a 1 is provided with a filter 34 and a fuel pressure regulator 35 and communicates with the injector 30. The fuel pressure regulator 35 regulates the fuel pressure supplied to the injector 30 at a constant level with respect to the intake pressure, and controls the fuel injection by the pulse width of the injection signal. It is possible to do. As an ignition system, the ignition system is connected so that an ignition signal from the igniter 36 is input to an ignition coil 8a connected to each ignition plug 8 of each cylinder.

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

On the other hand, the intercooler 2 near the throttle valve 21 is provided downstream of the blower 40b in order to prevent a decrease in the rotation of the blower and the occurrence of intake noise when the throttle valve is rapidly closed.
The bypass passage 46 is communicated between the outlet side of the blower 40b and the upstream side 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 the passage 47 when the throttle valve is rapidly closed, and to quickly leak pressurized air contained downstream of the blower.

An operation system of the secondary turbocharger 50 will be described. Similarly, the secondary turbocharger 50 is configured to supercharge the turbine 50a and the blower 50b by rotating the turbine 50a by the exhaust gas.
Is provided. A downstream-opening exhaust control valve 53 having a diaphragm actuator 54 is provided in the exhaust pipe 10 upstream of the turbine 50a, and a butterfly-type intake control valve having a similar actuator 56 downstream of the blower 50b. A boost pressure relief valve 57 is provided in a relief passage 58 between the upstream and downstream of the blower 50b.

The pressure operation system of each of these valves will be described. First, the surge tank 60 as a negative pressure source is connected to the check valve 62.
The valve 61 communicates with the intake manifold 23 through a passage 61 having a negative pressure, and stores a negative pressure and buffers a pulsating pressure when the throttle valve is fully closed. Further, a switching solenoid valve SOL. For the boost pressure relief valve for opening and closing the boost pressure relief valve 57. 1. Intake control valve 55
Switching solenoid valve for the intake control valve SOL. 2,
The first and second exhaust control valve switching solenoid valves SOL. 3, SOL. 4. Exhaust control valve 5
3 is provided with a duty solenoid valve 75 for small opening control, and a secondary wastegate switching solenoid valve 70 for opening and closing the secondary wastegate valve 51. Each switching solenoid valve 70, SOL. 1-4 are the electronic control units 10
The ON / OFF signal from 0 selects the negative pressure of the negative pressure passage 63 from the surge tank 60, the positive pressure from the positive pressure passages 64a and 64b communicating with the intake control valve downstream, the atmospheric pressure, and the like. The secondary wastegate valve 51, the supercharging pressure relief valve 57, and both the control valves 55 and 53 are operated by being guided to the actuator side by 70a to 74a. The duty solenoid valve 75 is connected to the positive pressure chamber 54 of the actuator 54 by a duty signal from the electronic control unit 100.
The positive pressure acting on “a” is variably controlled, and the exhaust control valve 53 is controlled to be slightly opened.

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

The switching solenoid valve SOL. 2
Is turned off, the atmosphere port is closed and the negative pressure passage 63 is closed.
Side of the actuator 5 through the control pressure passage 72a.
The intake control valve 55 is closed against the urging force of the spring by introducing a negative pressure into the pressure chamber in which the spring of No. 6 is housed.
When N is reached, the air pressure port is opened by closing the negative pressure passage 63 side, and the atmospheric pressure is guided to the pressure chamber of the actuator 56, so that the intake control valve 55 is opened by the urging force of the spring in the pressure chamber.

The 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.
If it is determined that regular gasoline is used,
N. When the secondary wastegate switching solenoid valve 70 is turned off, the passage 65 communicating upstream of the intake control valve 55 is closed to open the atmosphere port, and atmospheric pressure is introduced into the actuator 52 through the control pressure passage 70a. Then, the secondary wastegate valve 51 is closed by the urging force of the spring disposed in the actuator 52. Further, when turned on, the atmosphere port is closed and the passage 65 side is opened, and the supercharging pressure downstream of the secondary turbocharger 50 when both the turbochargers 40 and 50 are operated is guided to the actuator 52, and the supercharging pressure is adjusted according to the supercharging pressure. By opening the secondary wastegate valve 51, the supercharging pressure is relatively reduced when using regular gasoline as compared to when using high-octane gasoline.

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

First switching valve SO for exhaust control valve SO
L. An orifice 67 is provided in the control pressure passage 73a from the exhaust passage 3, and a leak passage 66 communicates with the downstream side of the orifice 67 and the intake pipe 17a. A duty solenoid valve 75 for control valve small opening control is provided. Then, the first exhaust control valve switching solenoid valve SOL. Only 3 is ON and positive pressure is applied to the actuator 54
When the negative pressure chamber 54b is supplied to the negative pressure chamber 54b and the negative pressure chamber 54b is opened to the atmosphere, the positive pressure is leaked by the duty solenoid valve 75 and the exhaust control valve 53 is slightly opened. Here, when the duty ratio in the duty signal is large, the duty solenoid valve 75 decreases the positive pressure acting on the positive pressure chamber 54a due to an increase in the leak amount, thereby reducing the opening of the exhaust control valve 53,
The positive pressure is increased as the duty ratio decreases, and the opening of the exhaust control valve 53 is increased. When the engine operating state is within a predetermined exhaust control valve small-opening control region under a single turbo state in which only the primary turbocharger 40 is supercharged, the opening degree of the exhaust control valve 53 by the duty solenoid valve 75 is determined. The supercharging pressure is feedback-controlled, and the exhaust control valve 53 is slightly opened with the supercharging pressure control.

Various sensors will be described. The differential pressure sensor 80 is provided to detect a differential pressure between the upstream and downstream of the intake control valve 55, and the absolute pressure sensor 81 is provided to select and detect the intake pipe pressure and the atmospheric pressure by the switching solenoid valve 76. Have been. A knock sensor 82 is attached to the engine body 1, and a coolant temperature sensor 83 faces a cooling water passage communicating the left and right banks 3, 4.
The O ₂ sensor 84 is exposed to the sensor. Further, a throttle sensor 85 having a built-in throttle opening sensor and an idle switch for detecting the throttle fully closed is connected to the throttle valve 21, and an intake air amount sensor 86 is provided immediately downstream of the air cleaner 15.

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

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

Next, the configuration of the electronic control system will be described with reference to FIG. The electronic control unit (ECU) 100
U101, ROM102, RAM103, backup RAM104, and the microcomputer which connected I / O interface 105 via the bus line are mainly comprised, and the constant voltage circuit 106 and the drive circuit 107 which supply predetermined | prescribed stabilized power supply to each part are provided. It is built in.

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

The I / O interface 105
Sensor 80-88, vehicle speed sensor 8
9 and a battery 96 are connected. Also, I / O
The igniter 36 is connected to the output port of the interface 105, and
CV25, injector 30, each switching solenoid valve 7
0, 76, SOL. 1-4, duty solenoid valve 4
3, 75 and the relay coil of the fuel pump relay 98 are connected.

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

Next, referring to FIG. 1 and FIG.
3 will be described in detail. First, the exhaust control valve 53 is
It has a cylindrical valve body 130 also serving as an exhaust pipe, and this valve body 130 is connected to a lower portion of the turbine housing 50 c of the secondary turbocharger 50 by bolts 145. The valve body 130 is formed with a valve seat 132 having a valve port 131 of a predetermined diameter inclined in the middle of the inside of the valve body 130, and a valve shaft 133 is horizontally installed at a position immediately downstream of the valve seat 132 so as to be rotatable. Then, a disc-shaped valve body 135 is attached to the arm 134 integral with the valve shaft 133 so that the valve body 135 is prevented from coming off by the mounting plate 136, and the valve shaft 135 is rotated clockwise so that the valve body 135 is attached to the valve seat 132. By contacting and closing the valve port 131 and rotating in the counterclockwise direction, the valve element 135 is configured to separate from the valve seat 132 and open to the downstream in the exhaust flow direction. Here arm 1
A predetermined clearance is provided between the valve body, the valve body 135, and the mounting plate 136, and when the flapper type valve body 135 is fully closed, its entire periphery is in close contact with the valve seat 132 to ensure the sealing property.

The exhaust control valve actuating actuator 54
Is installed at an angle above the exhaust control valve 53 by a stay 146 that is fastened together by bolts 145. The rod 140 extending below the actuator 54 and the valve shaft 13
The lever 141 integrated with the lever 3 is connected by a pin 142, and the rod 140 is retracted to rotate the valve shaft 133 clockwise, and the rod 140 is projected to rotate the valve shaft 133 counterclockwise. Further, the stopper 14 is provided on the valve body 130.
3 is protruded so as to engage with the lever 141 to regulate the fully open position.

Next, a chattering sound reduction measure will be described. First, in the pressure operation system of the exhaust control valve 53, as described above, the first exhaust control valve switching solenoid valve SOL. Third and second exhaust control valve switching solenoid valves SO
L. 4 Then, the first exhaust control valve switching solenoid valve SOL. 3 is provided in the positive pressure chamber 54a of the actuator 54 with the second exhaust control valve switching solenoid valve SOL. 4 communicates with the negative pressure chamber 54b, and when the exhaust control valve 53 is closed, the positive pressure in the positive pressure chamber 54a and the negative pressure in the negative pressure chamber 54b of the actuator 54 leak and the two control chambers are closed. 54a and 54b are opened to the atmosphere, and the exhaust control valve 5 is actuated by the urging force of the spring 54c.
3 is configured to close.

Here, the relationship as shown in FIG. 3 holds for the generation of chattering noise when the exhaust control valve 53 is closed. That is, the chattering sound generation time is a decreasing function of the valve closing speed as shown in (c), and increasing the valve closing speed shortens the chattering sound generation time and reduces the chattering sound. The valve closing speed is controlled by the actuator 54 as shown in FIG.
The function of increasing the capacity of the switching solenoid valve as shown in (b) of FIG. 2B, and the valve closing speed can be increased by increasing the nipple diameter and the capacity of the switching solenoid valve. Therefore, the control pressure passages 73a, 73 including the nipple
4a is increased from 4 mm to 6.35 mm, for example, and the switching solenoid valve SOL. 3, SOL. 4 is increased from, for example, 8 l / min to 20 l / min to increase the valve closing speed.

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

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

In the following description, the single turbo mode will be described first, and then the single-to-twin switching control will be described.
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, the process proceeds to step S2 because F1 = 0.

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. FIG.
As shown in the above table, the turbo switching determination value table contains a single-to-twin switch for switching from the single turbo mode to the twin turbo mode based on the relationship between the engine speed N and the engine load (basic fuel injection pulse width in this embodiment) Tp. A determination line L2 and, conversely, a twin-to-single switching determination line L1 for switching from the twin turbo mode to the single turbo mode are previously obtained from experiments and the like, and a single turbo region and a twin turbo region are set. And
The single-to-twin switching determination value Tp2 and the twin-to-single switching determination value Tp1 are stored in advance in a series of addresses of the ROM 102 as a table using the engine speed N as a parameter corresponding to each of the lines L2 and L1. Note that the single-to-twin switching determination line L2 is
In order to prevent torque fluctuation at the time of switching, it is necessary to set the point C where the torque curve TQ1 for single turbo and the torque curve TQ2 for twin turbo of the output characteristics of FIG. 16 coincide with each other. Then, the load is set to a low load side in accordance with an increase in the engine speed N from a high load in the low and medium speed ranges. Further, as shown in the figure, in order to prevent control hunting at the time of switching the number of operating turbochargers, the twin-to-single switching determination line L1 is relatively lower than the single-to-twin switching determination line L2 toward the lower rotational speed side. It is set to have 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, engine load) Tp, and Tp <Tp2
In the case of, the process proceeds to step S4 to perform single turbo mode control. If Tp ≧ Tp2, step S30
Then, the single to twin switching control is performed.

When the process proceeds from step S3 to step S4,
The value of the supercharging pressure control mode determination flag F2 is referred to. This supercharging pressure control mode discrimination flag F2 indicates that the current operation area is within the exhaust control valve small opening control mode area for performing the supercharging pressure control by the small opening of the exhaust control valve 53 and for pre-rotating the secondary turbocharger 50. Is set when it is out of range, and cleared when it is out of the area. Therefore, the ignition switch 97 is turned ON.
Immediately after the initial setting, and when the operation area is outside the exhaust control valve small opening control mode area at the time of execution of the previous routine, the flow proceeds to step S5 because F2 = 0. It is determined whether the area has shifted to the exhaust control valve small opening control mode area.

As shown in FIG. 12, the transition to the exhaust control valve small opening control mode range is determined based on the relationship between the engine speed N and the intake pipe pressure (supercharging pressure) P by a single-to-twin switching determination line. On the low-rotation low-load side of L2, that is, under the single turbo mode, the set value N1 (for example, 26
50 rpm), P1 (for example, 1120 mmHg), and the throttle opening TH is equal to the set value TH1.
When it is equal to or more than (for example, 30 deg), it is determined that it has moved into the area.

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

Then, the routine proceeds to step S10, where the switching solenoid valve SOL. 1 is turned off, and in step S11, the switching solenoid valve SOL.
2 is turned OFF. Next, when the process proceeds to step S12, the value of the supercharging pressure control mode determination flag F2 is referred to. If F2 = 0, the process proceeds to step S13, where the first exhaust control valve switching solenoid valve SOL. 3 is turned off, and at step S14, the second exhaust control valve switching solenoid valve SOL. 4 for OF
F. Thereafter, in steps S15 to S17, the twin turbo mode discrimination flag F1, the differential pressure search flag F3 described later, and the control valve switching time count value C1 are cleared, and then the routine exits.

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

When the exhaust control valve 53 is closed, the introduction of exhaust gas to the secondary turbocharger 50 is shut off, the secondary turbocharger 50 is deactivated, and the single turbocharger that operates only the primary turbocharger 40 is operated. State. Further, by closing the intake control valve 55, the leakage of the supercharging pressure from the primary turbocharger 40 to the secondary turbocharger 50 via the intake control valve 55 is prevented,
The reduction of the supercharging pressure is prevented. In addition, in the case of being under the single turbo mode and outside the exhaust control valve small opening control mode region, or in the case of the twin turbo mode, the supercharging pressure feedback control is not described in detail here, but only the primary wastegate valve 41 is used. It is performed using.

On the other hand, if it is determined in step S9 that the current operation area is within the exhaust control valve small opening control mode area and the supercharging pressure control mode determination flag F2 is set, the processing proceeds through steps S10 to S12. Proceeding to step S18, the first exhaust control valve switching solenoid valve SOL. O only for 3
N. Therefore, the first exhaust control valve switching solenoid valve S
OL. 3 turns ON, the positive pressure chamber 54 of the actuator 54
A positive pressure is introduced into a, and the exhaust control valve 53 is opened. In this exhaust control valve small opening control mode, the exhaust control valve small opening control routine shown in FIG.
The supercharging pressure feedback control is performed using the exhaust control valve 53 by being executed every 0 msec), and accordingly, the exhaust control valve 53 is slightly opened. That is, in FIG. 10, at step S100, the supercharging pressure control mode discrimination flag F
2 and exits the routine when F2 = 0,
F2 = 1 and in the case of the exhaust control valve small opening control mode, the routine proceeds to step S101, where the switching solenoid valve SOL. 1 is determined, and SOL. 1 = O
N, the routine exits and SOL. When 1 = OFF, the process proceeds to step S102, in which the target supercharging pressure is compared with the actual supercharging pressure detected by the absolute pressure sensor 81. An ON duty (duty ratio) for the duty solenoid valve 75 is calculated, a duty signal of this ON duty is output to the duty solenoid valve 75, and supercharging pressure feedback control is executed. For this reason, the positive pressure acting on the positive pressure chamber 54a of the actuator 54 is regulated by the duty solenoid valve 75, and as shown in FIG. Feed pressure feedback control is performed. A part of the exhaust gas is supplied to the turbine 50a of the secondary turbocharger 50 by the small opening of the exhaust control valve 53, and the secondary turbocharger 50 is preliminarily rotated to prepare for the transition to the twin turbo.

In this state, since the intake control valve 55 is closed, the blower 5 of the secondary turbocharger 50 is closed.
The supercharging pressure is confined between 0b downstream and the intake control valve 55. At this time, the supercharging pressure is leaked by opening the supercharging pressure relief valve 57, thereby smoothing the preliminary rotation.

Further, in the single turbo mode, the supercharging pressure control mode discrimination flag F
When 2 is set (F2 = 1), the process proceeds from step S4 to step S19, and based on the condition determination in steps S19 to S21, does the current operating region shift to outside the exhaust control valve small opening control mode region? Is determined.

As shown in FIG. 12, in order to prevent control hunting when switching to the supercharging pressure control mode, the setting value N2 which is lower than the setting values N1, P1 and TH1 is determined to be out of the range. (For example, 2600 rpm), P2 (for example, 1070 mmHg), and TH2 (for example, 25 deg). Then, in step S19, the engine speed N
Is compared with the set value N2. In step S20, the intake pipe pressure (supercharging pressure) P is compared with the set value P2.
To compare the throttle opening TH with the set value TH2, and N <
If N2, or P <P2, or TH <TH2, it is determined that the current operation region has shifted out of the exhaust control valve small opening control mode region, and the routine proceeds to step S8, where the supercharging pressure control mode determination flag F2 is set. clear. Thereby, the exhaust control valve small opening control is released. Also, N ≧ N2 and P ≧ P2
If TH ≧ TH2, it is determined that the current operation region remains within the region, and the routine proceeds to step S9, where the supercharging pressure control mode determination flag F2 is maintained at F2 = 1, and the exhaust control valve Continue small opening control.

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 blower 40b is rotated by the turbine 40a. Then, the air is sucked and compressed by the blower 40b, and the compressed air is
0, the flow rate is adjusted by the opening degree of the throttle valve 21, and supplied to each cylinder with high filling efficiency via the chamber 22 and the intake manifold 23 to perform a supercharging operation. And
In the single turbo state in which only the primary turbocharger 40 operates in the single turbo mode, as shown in the output characteristics of FIG. 16, a torque curve TQ1 at the time of a single turbo with a high shaft torque in the low and middle rotation speed ranges is obtained. .

Next, the single to twin switching control will be described. 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. 11), the process branches to step S30 to operate only the primary turbocharger 40. From the single turbo state, both turbochargers 40, 50
The single-to-twin switching control for switching to the operating twin turbo state is executed.

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

Therefore, the supercharging pressure relief valve 57 is provided with a switching solenoid valve SOL. By turning on 1 the positive pressure from the positive pressure passage 64a is introduced into the pressure chamber,
The valve is immediately closed by the positive pressure and the urging force of the spring. The exhaust control valve 53 includes a first exhaust control valve switching solenoid valve SOL. Actuator 5 by turning on 3
The valve opens when a positive pressure is introduced into the positive pressure chamber 54a.
When the control mode is changed from the small-open control mode of the exhaust control valve under the single turbo mode to the single-to-twin switching control, the switching solenoid valve SOL.
When 1 is turned on, in the exhaust control valve small opening control routine of FIG. 10, the supercharging pressure feedback control by the exhaust control valve 53 is stopped by exiting the routine through step S101 without performing the supercharging pressure feedback control. , Exhaust control valve duty solenoid valve 75 for small opening control
Is fully closed, and the positive pressure via the positive pressure passage 64b is directly introduced into the positive pressure chamber 54a of the actuator 54 without being leaked by the duty solenoid valve 75, so that the opening degree of the exhaust control valve 53 is increased. You.

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
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.

When the first routine is executed after the transition to the single-to-twin switching control, F3 = 0 because step F3 = 0.
First, the exhaust control valve opening delay time setting table is referred to with interpolation calculation based on the vehicle speed V, and the exhaust control valve 53 is fully opened (see FIG. Switching solenoid valve SOL.4 to O
An exhaust control valve opening delay time T1 that determines the timing of turning on from FF) is set. In step S36, the intake control valve opening delay time setting table is referred to with interpolation calculation based on the vehicle speed V, and the exhaust control valve 53 After the full opening control, the opening control of the intake control valve 55 (the intake control valve switching solenoid valve SO
L. 2 is changed from OFF to ON). The intake control valve opening delay time T2 for determining the condition of the start timing is set. Further, in step S37, the upstream pressure PU of the intake control valve 55
Pressure between the pressure and the downstream pressure PD (read value of the differential pressure sensor 80) D
An intake control valve opening differential pressure DPSS for determining a valve opening control start timing of the intake control valve 55 based on PS (= PU−PD).
Set T.

FIG. 13A is a conceptual diagram of an exhaust control valve opening delay time setting table, and FIG. 13B is a conceptual diagram of an intake control valve opening delay time setting table. As shown in the figure, as the vehicle speed V increases, the exhaust control valve opening delay time T1 and the intake control valve opening delay time T2 are shortened, and the timing of fully opening the exhaust control valve 53 and the intake control valve 5
The timing for opening the opening 5, that is, the timing for switching to the twin turbo mode, is advanced, the acceleration response is made uniform regardless of the vehicle speed, and the drivability is improved.

FIG. 13C is a conceptual diagram of an intake control valve opening differential pressure setting table. As shown in the drawing, the differential pressure immediately after the engine operating state shifts from the single turbo region to the twin turbo region (see FIG. 11) with the single-to-twin switching determination line L2 (single-to-twin switching determination value Tp2) as a boundary. The more the 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, the more the intake control valve opening differential pressure DPSS
T is set to the minus side, the timing of opening the intake control valve 55 is advanced, and the acceleration response is improved.

After setting the delay times T1 and T2 and the intake control valve opening differential pressure DPSST, the routine proceeds to step S38, in which a differential pressure search flag F3 is set, and the routine proceeds to step S39. In step S39, the second exhaust control valve switching solenoid valve SOL. 4 to determine whether the exhaust control valve 53 has already been fully opened. 4 = ON, and if the exhaust control valve fully open control has already been started, the routine jumps to step S47, where the second exhaust control valve switching solenoid valve SOL. 4 is kept ON, and SOL. 4
In the case of = OFF, since the exhaust control valve fully open control has not been executed, the process proceeds to step S40, where the control valve switching time count value C1 is compared with the exhaust control valve open delay time T1,
After the shift from the single to the twin switching control, it is determined whether or not the exhaust control valve opening delay time T1 has elapsed.

If C1 ≧ T1, the flow jumps to step S45 to jump to the second exhaust control valve switching solenoid valve SOL. 4 is turned ON, and the exhaust control valve 53 is fully opened. If the delay time before C1 <T1 has elapsed, the process proceeds to step S41, where the engine load Tp is compared with a value obtained by subtracting the set value WGS from the single-twin switching determination value Tp2 set in step S2, and Tp <Tp2
In the case of -WGS, the process returns to step S8, in which the single-to-twin switching control is stopped and the mode is immediately switched to the single turbo mode. This is to eliminate the uncomfortable feeling of driving by returning to the single turbo mode when the engine load Tp decreases.

More specifically, as shown in FIG.
The engine operating state changes from single turbo range to single →
Once the vehicle crosses the twin switching determination line L2 (Tp2) toward the twin turbo region, the exhaust control valve 53 is fully opened after the delay time T1 has elapsed unless the vehicle crosses the twin → single switching determination line L1 (Tp1) toward the single turbo region. (Step S45) Further, 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 is opened (Step S49), and the state is switched to the twin turbo state. Therefore, once the single-to-twin switch determination line L2 is exceeded, the single-to-single switch determination line L1 and the single-to-twin switch determination line L
If the operating state remains in the area surrounded by 2, the state will be switched to the twin turbo state after the delay time has elapsed. However, in this region, as shown in FIG. 16, the shaft torque of the torque curve TQ2 at the time of the twin turbo by the operation of the secondary turbocharger 50 is lower than the shaft torque at the time of the single turbo given by the torque curve TQ1. In other words, when switching from the single turbo state to the twin turbo state, a sudden decrease in torque causes a torque shock and gives the driver a sense of incompatibility.

In order to cope with this, the twin-to-single switching determination line L1 is changed to the single-to-twin switching determination line L1.
2, the width (hysteresis) of the two switching lines may be reduced, but if the width between the two switching lines L1 and L2 is reduced, the frequency of switching between the single turbo and the twin turbo increases, and each control valve is activated. Since the negative pressure capacity of the surge tank 60 as a negative pressure source to be
If the operating state remains near the single-to-twin switching determination line L2, the engine load Tp, which is a parameter of the turbocharger operating number switching parameter, is changed when the operating state is too small. In addition, there is an inconvenience that the boost pressure relief valve 57 without setting the switching delay time causes chattering.

In order to prevent these, the operating condition is changed from single to
After crossing the twin switching determination line L2 to the twin turbo region side and before the delay time T1 elapses, the interval from the single to twin switching determination line L2 is narrow and the set value WGS is subtracted to the single turbo region side by a broken line in FIG. Single-twin switching determination stop line L3 (= Tp2-W
GS) to the single turbo range side, the single-to-twin switching control for switching to the twin turbo state is stopped, the system is immediately shifted to the single turbo mode, and the single turbo state in which only the primary turbocharger 40 operates is maintained. This eliminates the operation in the region where the torque is low in the twin turbo state, and improves the drivability.

On the other hand, in step S41, Tp ≧ Tp2-W
In the case of GS, the process proceeds to step S42, and after the shift from the single to the twin switching control, the high load determination value TpH for determining whether or not the engine operation state has shifted to the high load high speed range before the delay time T1 has elapsed is set to the engine speed. Based on the number N, a high load determination value table is set with reference to interpolation calculation.

FIG. 11D is a conceptual diagram of the high load determination value table. Fuel injection pulse width (engine load) Tp
Is obtained by Tp = K × Q / NK: constant, Q: intake air amount. When the load is high and the intake air amount Q is constant, the fuel injection pulse width (engine load) Tp is the engine speed Np. Is inversely proportional to Accordingly, 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 determination value TpH, Tp ≦ TpH
In step S44, the process proceeds to step S44, where the control valve switching time count value C1 is counted up, and the routine exits. On the other hand, if Tp> TpH and it is determined that the engine operating state has shifted to the high-load high-speed range before the delay time T1 has elapsed (for example, corresponding to the case of rapid acceleration, racing, etc.), step S45 is performed. To the second exhaust control valve switching solenoid valve SOL. 4 is immediately turned on, the exhaust control valve 53 is fully opened, and the exhaust is also flown to the secondary turbocharger 50 side, so that the primary turbocharger 40 surging and damage due to reaching a critical rotation speed due to a rapid increase in exhaust flow rate. To prevent

After the shift to the single-twin switching control, when the exhaust control valve opening delay time T1 has elapsed and the process proceeds from step S40 or from step S43 to step S45, the second solenoid valve SOL. 4 is turned on, the exhaust control valve 53 is fully opened, the rotational speed of the secondary turbocharger 50 is further increased, and the blower 50b
Turbocharger 50 between the air conditioner and intake control valve 55
, The compressor pressure (supercharging pressure) also increases, and as shown in FIG. 14, the differential pressure DPS between the upstream and downstream of the intake control valve 55
Rises. Thereafter, the process proceeds to step S46, in which the control valve switching time count value C1 is cleared to measure the time after the exhaust control valve is fully opened, 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 fully opening control (SOL.4 OFF → ON) is compared with the intake control valve opening delay time T2. ,
If C1 <T2, it is determined that the condition for opening the intake control valve 55 is not satisfied, and the count value C is determined in step S44.
Count up 1 and exit the routine. Also, C1 ≧
In the case of T2, it is determined that the valve opening condition is satisfied, and step S4
8 and the current differential pressure DPS and the intake control valve opening differential pressure DPS
ST is compared to determine whether the intake control valve 55 has reached the valve opening start timing.

When DPS <DPSST, it is determined that the valve opening start time has not been reached, and the routine exits.
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 And it is determined 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 a twin turbo state is established. Then, the process proceeds to step S50, and upon completion of the single-to-twin switching control, the twin turbo mode discrimination flag F1 is set to shift to the twin turbo mode next time, and the routine exits. The switching state from the single turbo mode to the twin turbo mode by the above single-to-twin switching control is shown in a time chart of FIG.

As described above, in the single-to-twin switching control, first, the supercharging pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and the preliminary rotation speed of the secondary turbocharger 50 is reduced. After that, the exhaust control valve opening delay time T1 gives a time necessary for increasing the preliminary rotation speed of the secondary turbocharger 50, and after the delay time T1, the exhaust control valve 53 is fully opened. Then, the supercharging pressure by the secondary turbocharger 50 between the blower 50b of the secondary turbocharger 50 and the intake control valve 55 increases, the differential pressure DPS increases, and after the exhaust control valve is fully opened, the intake control valve opening delay is increased. At time T2, the exhaust control valve 5
3 is compensated for, and after the delay time T2 elapses, when the differential pressure DPS between the upstream and downstream of the intake control valve 55 reaches the intake control valve opening differential pressure DPSST, the intake control valve 55 Is opened. Thus, the switching from the single turbo state in which only the primary turbocharger 40 is operated to the twin turbo state by operating both the turbochargers 40 and 50 is smoothly performed.
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 the supply pressure is effectively and reliably prevented.

Next, the twin turbo mode will be described. If the twin-turbo mode discrimination flag F1 is set due to the end of the single-to-twin switching control, or if the twin-turbo mode was set at the time of the previous execution of the routine, at the time of this execution of the routine, F1 = 1 and the process branches from step S1 to step S60. .

Then, in step S60, a twin-to-single switching determination value Tp1 is set by referring to a turbo switching determination value table with interpolation calculation based on the engine speed N (see FIG. 11), and the routine proceeds to step S61. Load T
p is compared with the above-mentioned twin-to-single switching determination value Tp1, and if Tp ≧ Tp1, the current operation state is in the twin turbo range, and the determination value search flag F is set in step S62.
4 is cleared, the single turbo region duration count value C2 for counting the single turbo region duration after shifting to the single turbo region in step S63 is cleared, and then the process jumps to step S72 and proceeds to step S7.
2 to step S75, the switching solenoid valve SOL. 1. Switching solenoid valve S for intake control valve
OL. 2, the first and second exhaust control valve switching solenoid valves SOL. 3 and 4 are turned on, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 53 are both fully opened, and the twin turbo mode discrimination flag F1 is set in step S76. Return to S17,
After clearing the control valve switching time count value C1, the routine exits.

In the 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, the secondary turbocharger is added to the primary turbocharger 40. The full-scale operation of the turbochargers 50 and 50 results in a twin turbo state due to the supercharging operation of the turbochargers 40 and 50, and the compressed air generated by the supercharging of the turbochargers 40 and 50 is supplied to the intake system. As shown in FIG. 7, a torque curve TQ2 at the time of twin turbo with a high shaft torque in a high rotation speed region is obtained.

On the other hand, in the above step S61, Tp <Tp
If it is determined that the current operating state has shifted to the single turbo range (see FIG. 11), the process proceeds to step S64, and the value of the determination value search flag F4 is referred to. If F4 = 0, the process proceeds to step S65. The process proceeds to step S67 if F4 = 1.

The determination value search flag F4 is cleared when the engine operating state is in the twin turbo mode with the engine load Tp being in the twin-to-single switching determination line L1 (Tp1) in the twin turbo mode (step S).
62). Therefore, after Tp <Tp1, the process proceeds to step S65 when the first routine is executed, and the single turbo region duration time determination value T is referenced by referring to the single turbo region duration time determination value table with interpolation calculation based on the engine load Tp.
Set 4. This 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 has shifted from the twin turbo region to the single turbo region.

FIG. 13E is a conceptual diagram of a single turbo area continuation time determination value table. Single turbo region continuation time determination value T set according to engine load Tp
4 is set to, for example, a maximum of 2.3 sec and a minimum of 0.6 sec, and is set to a smaller value as the value of the engine load Tp is larger and higher. As a result, after the engine operation state shifts from the twin turbo region to the single turbo region, the time until switching from the twin turbo mode to the single turbo mode is accelerated as the engine load is higher,
In the twin turbo state, operation in a portion where the shaft torque is low is prevented, and reacceleration is improved.

Next, after setting the judgment value search flag F4 in step S66, the process proceeds to step S67. Then, in step S67, the count value C2 of the single turbo region duration time is counted up, and then in step S68, the determination value T4 is compared with the count value C2, and C2 ≧ T4
In the case of, the process proceeds to step S71 to clear the count value C2, and then returns to step S8 to switch from the twin turbo mode to the single turbo mode. Thereby, each switching solenoid valve SOL. 1 to 4 are turned off, the supercharging pressure relief valve 57 is opened, and both the intake control valve 55 and the exhaust control valve 53 are closed.
The state changes from the twin turbo state of 50 operations to the single turbo state in which only the primary turbocharger 40 operates.

The switching state at this time is shown by a time chart as shown by the solid line in FIG. As described above, switching from the twin turbo mode to the single turbo mode is performed when the engine operation range shifts from the twin turbo range to the single turbo range (Tp <Tp1) and the state continues for the 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
To the throttle opening TH and the set value TH3 (for example, 3
0 deg), and when TH> TH3, the process returns to step S8 via the above-described step S71, and even after the engine operation region shifts to the single turbo region and before the state continues for the set time, the state shown in FIG. As shown by the broken line, the mode is immediately switched to the single turbo mode, the supercharging pressure relief valve 57 is opened, the exhaust control valve 53 and the intake control valve 55 are both closed, and the secondary turbocharger 50 is closed.
Is stopped, and only the primary turbocharger 40 is switched to the single turbo state of the supercharging operation.

The set value TH3 is for judging an acceleration request. In other words, in the single turbo region (Tp <Tp1), as shown in the output characteristic of FIG. 16, it is on the low rotation side of the twin-to-single switching determination line L1 and is in the region where the shaft torque of the torque curve TQ2 at the time of the twin turbo is low. In this state, if the twin-turbo mode is maintained and the twin-turbo state is maintained, sufficient acceleration performance cannot be obtained even when the accelerator pedal is depressed. Therefore, when operating in this region, when it is determined that an acceleration request is required (TH> TH3), the mode is immediately shifted to the single turbo mode to be in the single turbo state, and the torque curve TQ1 of the high shaft torque in the single turbo mode is set. To improve the acceleration response.

In step S69, TH ≦ TH3
In step S70, the process proceeds to step S70, where the vehicle speed V is compared with a set value (for example, 2 km / h). When V> V2, it is determined that the vehicle is running, the process proceeds to step S72 to maintain the twin turbo mode. If it is determined that the vehicle is in a stopped state with V ≦ V2, the process returns to step S8 via step S71 in the same manner as described above, and immediately shifts to the single turbo mode.

The set value V2 is used to determine the stop state of the vehicle. If the accelerator pedal is depressed while the vehicle is stopped, for example, at idle speed, and the engine is idled, the engine load Tp increases and the engine load Tp increases. The engine speed N increases, the engine operation region shifts from the single turbo region to the twin turbo region, and the engine enters a twin turbo state. After the accelerator is released, the engine load Tp and the engine speed N immediately decrease, and the engine speed decreases. When the operation region shifts again to the single turbo region with the twin-single switch determination line L1 (see FIG. 11) as a boundary, after the shift to the single turbo region, the switch to the single turbo mode is performed until the set time has elapsed (C2 ≧ T4). However, during this time, as shown in FIG. 15, the engine speed N decreases and the idle speed N
i (for example, near 700 rpm), and then each switching solenoid valve SOL. Switching from 1 to 4 is performed, and the supercharging pressure relief valve 57 and each of the control valves 53 and 55 are switched. At this time, since the engine speed N is low, the background noise due to the engine rotation is low, and the sound generated when each valve is switched is heard by the driver, giving the driver discomfort.
Therefore, when it is determined that the vehicle is stopped, (V ≦ V
2) After switching to the single turbo range, even if the set time has not elapsed (C2 <T4), immediately switching to the single turbo mode allows each valve to operate before the engine speed decreases and the background noise decreases. Is completed, and the discomfort caused by the noise of the valve operation is eliminated. The state of switching from the twin turbo mode to the single turbo mode at this time is shown by a dashed line in FIG.

Further, the operation of the exhaust control valve 53 in the above-described supercharger operation number switching control will be described. First, in the single turbo mode and when the engine operation region is outside the exhaust control valve small opening control mode region, the actuator 54
When the positive pressure chamber 54a and the negative pressure chamber 54b are opened to the atmosphere, the rod 140 is retracted by the spring 54c, and the valve shaft 133 is rotated clockwise by the lever 141. For this reason, the valve body 135 of the exhaust control valve 53 is fully closed in a state in which the entire periphery thereof is in close contact with the valve seat 132 by the clearance of the mounting portion and the sealing property is secured.

In the exhaust control valve small opening control mode, the first exhaust control valve control switching solenoid valve SOL. When a positive pressure is introduced into the positive pressure chamber 54a of the actuator 54 by 3,
The rod 140 projects a predetermined amount against the urging force of the spring 54c, and the lever 141 rotates the valve shaft 133 counterclockwise. Then, the valve body 135 is separated from the valve seat 132 by the arm 134 and starts to open as shown in FIG. 1, and at this time, the positive pressure is regulated by the duty solenoid valve 75, so that the valve body 135 is variably controlled to a small opening. Open a little.

Next, when a transition is made to the twin turbo mode by the single-to-twin switching control, the actuator 54
In the state where the positive pressure is introduced into the positive pressure chamber 54a, the second exhaust control valve control switching solenoid valve SOL. 4, a negative pressure is introduced into the negative pressure chamber 54b of the actuator 54, the rod 140 projects most, the valve shaft 133 further rotates counterclockwise, and the valve element 135 is separated from the valve seat 132 and fully opened. At this time, the lever 141 comes into contact with the stopper 143 and is restricted to the fully open position.

Further, the mode shifts from the twin turbo mode to the single turbo mode, and the first and second exhaust control valve control switching solenoid valves SOL. 3, SOL. 4 is switched to the atmosphere port side, the positive pressure chamber 5
4a and the negative pressure in the negative pressure chamber 54b are controlled by the control pressure passages 73a and 74a and the switching solenoid valve SOL. 3, SO
L. 4, the chambers 54a and 54b are opened to the atmosphere. Therefore, the spring 54 of the actuator 54
c retreats the rod 140 again, and the exhaust control valve 53
Closes. At this time, immediately before the closing of the exhaust control valve 53, a large exhaust pulsation acts on the valve body 135 as the pressure receiving area increases, so that the valve body 135 dances due to its clearance and collides with the valve seat 132 to vibrate. Chattering sound is likely to occur.

Incidentally, the diameters of the control pressure passages 73a and 74a and the switching solenoid valve SOL. 3, SOL. 4, the positive pressure chamber 5 of the actuator 54 is large.
The positive pressure at 4a and the negative pressure at the negative pressure chamber 54b leak quickly, thereby increasing the closing speed of the exhaust control valve 53. Therefore, when the exhaust control valve 53 is closed, the valve body 135 and the valve seat 132 only vibrate and collide for a moment, and the time for generating chattering noise is very short. This makes it impossible for the occupant to recognize this sound, and the chattering sound is substantially reduced.

Although the embodiment of the present invention has been described above, the present invention can also be applied to a supercharged engine other than the horizontally opposed type.

[0086]

As it has been described above devised], according to the present invention,
The exhaust system to which the secondary turbocharger is connected is provided with a flapper type exhaust control valve that opens downstream, and controls the control pressure acting on the positive pressure chamber and the negative pressure chamber of the diaphragm type actuator that operates this exhaust control valve. Set the capacity of the switching solenoid valve to be switched from 8 l / min to 20 l / min.
At the same time, the exhaust control valve is opened and closed by the switching solenoid valve.
The diameter of the passage communicating with each chamber of the actuator is 4 mm
6.35 mm, the capacity of the switching solenoid valve and the diameter of the passage have been increased, so that when the exhaust control valve is closed, both chambers of the actuator are quickly opened to the atmosphere and the exhaust control valve is opened. , The chattering sound generation time is shortened, and as a result, it becomes difficult to recognize the chattering sound when the exhaust control valve is closed, and the chattering sound can be effectively reduced. With this, the exhaust control valve
Eliminates the discomfort of the occupant by the chattering sound, 且
First, the wear of the mounting part of the exhaust control valve should be reduced.
Can be . In addition , the capacity of the switching solenoid valve,
And since only the diameter of the passage is set to be large, the exhaust system
Measures to reduce chattering noise of the control valve and the structure of the exhaust control valve
To be realized with a simple configuration without substantial changes
Can be .

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a main part of an embodiment of a supercharged engine according to the present invention.

FIG. 2 is a side view showing an exhaust control valve.

FIG. 3 (a) is a valve closing speed with respect to a nipple diameter, and (b)
FIG. 4 is an explanatory diagram showing a relationship between a valve closing speed with respect to a capacity of a switching solenoid valve and a relationship between a valve closing speed and a chattering sound generation time.

FIG. 4 is an overall configuration diagram of a supercharged engine.

FIG. 5 is a circuit diagram of a control device.

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

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

FIG. 8 is a flowchart showing a turbo switching control routine.

FIG. 9 is a flowchart showing a turbo switching control routine.

FIG. 10 is a flowchart showing an exhaust control valve small opening control routine.

FIG. 11 is an explanatory diagram showing each switching determination value and a relationship between a single turbo region and a twin turbo region.

FIG. 12 is an explanatory diagram of an exhaust control valve small opening control mode region.

13A is an exhaust control valve opening delay time setting table, FIG. 13B is an intake control valve opening delay time setting table, FIG. 13C is an intake control valve opening differential pressure setting table, and FIG. FIG. 7E is a conceptual diagram showing a single turbo area duration time determination value table, respectively.

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

FIG. 15 is a time chart showing a switching state from a twin turbo mode to a single turbo mode.

FIG. 16 is an explanatory diagram showing output characteristics during single turbo and twin turbo.

[Explanation of symbols]

 1 Engine main body 40 Primary turbocharger 50 Secondary turbocharger 53 Exhaust control valve 54 Actuator 54a Positive pressure chamber 54b Negative pressure chamber 73a, 74a Control pressure passage SOL. 3 First switching solenoid valve for exhaust control valve SOL. 4. Switching solenoid valve for second exhaust control valve

Claims (1)

(57) [Scope of request for utility model registration] 1. A place engine intake, a primary turbocharger and a secondary turbocharger to the exhaust system in parallel, low
In the high speed range, both valves are closed and the supercharging operation of the secondary turbocharger is performed.
In a single turbo state where operation is stopped,
To open both valves and supercharge both turbochargers
An intake control valve to be in a turbo state and a flapper type exhaust control valve that opens downstream are respectively disposed in an intake and exhaust system connected to a secondary turbocharger, and have a positive pressure chamber and a negative pressure chamber. comprising a diaphragm actuator for operating the exhaust control valve, disposed switching solenoid valve for switching the control pressure which acts on the positive pressure chamber and the negative pressure chamber of the actuator, both of the actuator by the <br/> switching solenoid valve the chamber closes the exhaust control valve by air opening, the negative pressure in the negative pressure chamber, with a supercharger and the exhaust control valve by supplying a positive pressure to positive pressure chamber to open <br/> valve in the engine, the chambers of the actuator from the switching solenoid valve
The diameter of the communicating passage is increased from 4mm to 6.35mm
An engine with a turbocharger.