JP3117784B2 - Exhaust control method for sequential turbo engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sequential turbo engine having a plurality of turbochargers and operating in a sequential turbo system as a vehicle engine.
The present invention relates to an exhaust control system that controls exhaust gas introduced into a secondary turbocharger, and more particularly, to an exhaust control method that fully closes, minutely opens, and fully opens an exhaust control valve in each mode.

[0002]

2. Description of the Related Art In recent years, as a supercharged engine for a vehicle, a multi-cylinder exhaust system is equipped with a primary and secondary turbocharger in parallel, and the turbocharger is operated in a sequential turbo system. Things have been suggested. In this sequential turbo engine, generally, a secondary turbocharger is provided with an intake control valve, a relief valve, an exhaust control valve and the like to operate the secondary turbocharger in a twin turbo mode. In addition, in order to improve responsiveness at the time of transition from the single turbo mode to the twin turbo mode and to reduce torque fluctuation, it is considered to introduce a small amount of exhaust gas from the secondary turbocharger and perform preliminary rotation. In this case, if a pre-control valve or the like is used as the means for pre-rotating, the structure and control become complicated, and it is required to improve this point.

[0003] Conventionally, the preliminary rotation control of the sequential turbo engine has been disclosed in, for example, Japanese Patent Application Laid-Open No. 1-3156.
There is a prior art of Japanese Patent Publication No. 14. Here, when shifting from the single turbo mode to the twin turbo mode, the exhaust leakage valve is opened with the intake relief valve open, and a part of the exhaust gas is introduced into the secondary turbocharger and preliminarily rotated.
It is shown that the intake relief valve is closed before the exhaust cut valve opens, the rotation is sufficiently increased, and in this state, the exhaust cut valve and the intake cut valve are opened to control the secondary turbocharger to operate. Have been.

[0004]

The prior art described above uses a valve such as an exhaust leak valve at the time of preliminary rotation and controls the opening and closing of the intake relief valve and the exhaust leak valve. , Structure and control become complicated.
In addition, since the operation is performed by switching valves having different valve characteristics, there is a problem that it is difficult to smoothly change the supercharging pressure and the like.

The present invention has been made in view of this point, and in a sequential turbo engine, an exhaust control valve is also used for preliminary rotation by itself and the structure of an actuator, thereby simplifying the structure and control. An object of the present invention is to reduce torque fluctuation and prevent overspeed of a turbocharger.

[0006]

In order to achieve the above object, the present invention provides a primary turbocharger and a secondary turbocharger which are arranged in parallel in an intake and exhaust system of an engine body. Boost pressure relief valve on the machine side
An intake control valve and an exhaust control valve are provided to operate only the primary turbocharger in the single turbo mode, and to control both the primary turbocharger and the secondary turbocharger in the twin turbo mode , Thing
In the turbo mode, the actuator spring
Close the exhaust control valve and turn off the boost pressure relief valve during preliminary rotation.
Close and open the exhaust control valve with the exhaust pressure in this operating state.
The exhaust control valve and the feeder control valve
In the sequential turbo engine exhaust control method of controlling the opening of the valve to shift to the twin turbo mode, the exhaust control valve is opened downstream and its actuator is opened.
The spring is biased in the closing direction.
The spring force of the
Of the exhaust control valve.
Data is open to two chambers in single turbo mode
And create negative pressure and positive pressure in the two chambers in twin turbo mode.
That the exhaust control valve is fully opened.
Sign.

[0007]

In the above exhaust control method, the spring force of the actuator and the exhaust pressure in each operating state act on the exhaust control valve of the secondary turbocharger opposingly when the engine is operating, so that the single turbo mode in the low to medium speed range is used. When the exhaust pressure is relatively low, the exhaust control valve closes and only the primary turbocharger operates. In the preliminary rotation mode, the exhaust control valve automatically opens the minute valve with the exhaust pressure in this case, so that a part of the exhaust gas is introduced into the secondary turbocharger and the preliminary rotation is started. When opened, the preliminary rotation further proceeds, and thus the secondary supercharging pressure smoothly rises due to the change in the opening degree of the exhaust control valve, and the mode shifts to the twin turbo mode with little torque fluctuation.
Further, in the single turbo mode, when the exhaust pressure increases due to a failure on the primary turbocharger side, the exhaust control valve opens minutely to leak exhaust gas, thereby preventing the primary turbocharger from blowing.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the overall configuration in the case where a sequential turbocharger is mounted on a horizontally opposed engine will be described. Reference numeral 1 denotes an engine body of a horizontally opposed engine.
A combustion chamber 5, an intake port 6, an exhaust port 7, a spark plug 8, a valve mechanism 9, and the like are provided. Due to this engine shortening shape, a primary turbocharger 40 and a secondary turbocharger 50 are respectively provided immediately after the left and right banks 3 and 4. Left and right banks 3, 4 as exhaust system
Are connected to the turbines 40a, 50a of the turbochargers 40, 50, and the turbine 40a,
The exhaust pipe 11 from 50a joins one exhaust pipe 12 and communicates with the catalytic converter 13 and the muffler 14.

[0009] As an intake system, intake pipes 16 and 17 branched from the air cleaner 15 into two pipes are connected to blowers 40b and 50b of both turbochargers 40 and 50, respectively, and intake pipes 18 and 17 from the blowers 40b and 50b. 19 is communicated with 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, an idle control valve 25 and a check valve 2 that opens with a negative pressure are provided in a bypass passage 24 immediately downstream of the air cleaner 15 and the intake manifold 23.
6 is provided to control the intake air amount during idling or deceleration.

As a fuel system, an injector 30 is disposed near a port of the intake manifold 23, and a fuel passage 33 from a fuel tank 32 having a fuel pump 31 is provided with a filter 34 and a fuel pressure regulator 35 and communicates with the injector 30. Is done. The fuel pressure regulator 35 adjusts according to the intake pressure, thereby keeping the fuel pressure supplied to the injector 30 always constant with respect to the intake pressure, and controlling the fuel injection by the pulse width of the injection signal. It has become possible. The ignition system is connected so that an ignition signal from the igniter 36 is input to the ignition plug 8 as an ignition system.

An operation system of the primary turbocharger 40 will be described. The primary turbocharger 40 uses a blower 40b by the energy of exhaust gas introduced into the turbine 40a.
Is operated to inhale and pressurize air to constantly supercharge. A waste gate valve 41 having a diaphragm type actuator 42 is provided on the turbine side. The pressure chamber of the actuator 42 is communicated with a control pressure passage 44 having an orifice 48 from immediately downstream of the blower 40b so as to open the waste gate valve 41 with good response when the supercharging pressure rises above a set value. You. 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, and a predetermined control pressure is generated by the duty solenoid valve 43 to act on the actuator 42. The supercharging pressure is controlled by changing the opening of the valve 41. Here, for example, when the duty ratio is large, the control pressure is reduced by increasing the leak amount, and the waste gate valve 4
The boost pressure is increased by decreasing the opening of (1). Conversely, when the duty ratio decreases, the opening degree is increased at a high control pressure, and the supercharging pressure is reduced.

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 blower rotation 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.
A waste gate valve 51 provided with 2 is separately provided. A passage 67 directly downstream of the blower 50b communicates with the pressure chamber of the actuator 52 via a duty solenoid valve 53 and a control pressure passage 54 which leak to the atmosphere. The gate valve 51 is opened, a control pressure is generated by the duty solenoid valve 53, and the supercharging pressure is similarly controlled. On the other hand, an exhaust control valve 55 having a diaphragm actuator 56 is provided in the exhaust pipe 10 upstream of the turbine 50a.
An intake control valve 58 provided with a similar actuator 57 is provided downstream of the blower 50b.
A relief passage 59 having a supercharging pressure relief valve 60 is communicated between the upstream and downstream of Ob.

A pressure operation system of each of these valves will be described. A passage 61 from the intake manifold 23 has a check valve 62 and communicates with a surge tank 63 to store a negative pressure when the throttle valve is fully closed and to generate a pulsating pressure. It is designed to buffer. A negative pressure passage 64 from the surge tank 63 and a positive pressure passage 65 downstream of the intake control valve 58 are connected to one spring chamber of the supercharging pressure relief valve 60 via a switching solenoid valve 70 and a passage 66. You. Then, the supercharging pressure relief valve 60 is opened by applying a negative pressure by an electric signal, and the supercharging pressure relief valve 60 is closed by applying a positive pressure. An actuator 57 of the intake control valve 58 has a switching solenoid valve 71 for switching between negative pressure and atmospheric pressure in one of the spring chambers.
8 is communicated. Then, a negative pressure is applied by an electric signal to close the intake control valve 58, and the intake control valve 58 is opened by a spring force when the atmosphere is opened.

The exhaust control valve 55 is configured to open downstream, and a spring 56a is provided in one chamber of the actuator 56.
Are urged in a direction to close the exhaust control valve 55. Here, the spring force of the spring 56a is set equal to the force due to the exhaust pressure in the preliminary rotation mode in the middle speed range. A second solenoid valve 74 for switching between atmospheric pressure and negative pressure is connected to one chamber of the actuator 56 having the spring 56a via a passage 69, and the other chamber is switched between positive pressure and atmospheric pressure. The first switching solenoid valve 73 is connected via a passage 75. In the single turbo mode, both chambers are opened to the atmosphere by the operation of the first and second switching solenoid valves 73 and 74 by an electric signal, and the exhaust control valve 55 is fully closed by a spring force. When the waste gate valve 41 on the primary side fails and the exhaust pressure rises, it has a function of automatically opening and fail-safe. In the pre-rotation mode, this state is maintained for a predetermined time, and a function of a pre-control valve is provided by opening only a minute opening by a balance between the exhaust pressure and the spring force. Further, in the twin turbo mode, the exhaust control valve 55 is fully opened by applying a negative pressure to one chamber and a positive pressure to the other chamber, and is kept in the fully opened state.

A description will be given of various sensors. A differential pressure sensor 80 is provided to detect a differential pressure between upstream and downstream of the intake control valve 58, and an absolute pressure sensor 81 is controlled by a switching solenoid valve 76 to detect the intake pipe pressure. It is provided to select and detect the atmospheric pressure. Further, a crank angle sensor 82, a knock sensor 83, and a water temperature sensor 84 are provided on the engine body 1, and a cam angle sensor 85 is provided opposite to a cam rotor (not shown) connected to a cam shaft of the valve mechanism 9; 10 is provided with an O2 sensor 86 and the throttle valve 21 is provided.
A throttle opening sensor 87 is provided in the air cleaner 15, and an intake air amount sensor 88 is provided immediately downstream of the air cleaner 15.

Referring to FIG. 2, the overall configuration of the electronic control system will be described. First, a control unit 100 including a microcomputer and the like includes an I / O 101, a CPU 10
2, RAM103, backup RAM104, ROM
105 and a constant voltage circuit 106. Also, when the ignition switch 90 is turned on, the relay 91 is turned on, and power is supplied from the battery 92 to the constant voltage circuit 106.
Various controls of the control unit 100 are executed, and the drive circuit 10
7, the relay 93 is turned on, and the fuel pump 31 is energized and driven. The CPU 102 inputs signals from the various sensors 80 to 88 and the vehicle speed sensor 89 from the I / O 101 based on the arithmetic program stored in the ROM 105,
The arithmetic processing is performed based on the data stored in the M103 and fixed data such as a map stored in the ROM 105. A switching signal is output from the drive circuit 107 to the various switching solenoid valves 70, 71, 73, 74, 76 and a duty signal is output to the duty solenoid valves 43, 53 to perform sequential turbo control, and an injection signal is output to the injector 30. Control the fuel injection. Also igniter 3
6 to control the ignition timing by outputting an ignition signal, and to output a control signal to the idle control valve 25 to perform idle control.

Next, the sequential turbo control by the control unit 100 will be described with reference to the flowcharts of FIGS. The main routine of FIG. 3 is executed every predetermined time. First, in step S1, the value of the secondary turbocharger operation determination flag F1 that is set to 1 when the secondary turbocharger is activated is referred to. If F1 = 0 is not operated, the process proceeds to steps S2 to S4, and FIG. The determination is made based on the turbo mode determination map of a).

This turbo mode determination map is based on the basic injection amount Tp as an example showing the engine load and the set values Tps, Nb and Nc for starting the operation of the secondary turbocharger with respect to the engine speed N. Turbo mode is given. That is, Tp ≦ Tps,
N <Nc, low load, medium speed, or Tp> Tps, N <N
Under the condition of high load and low speed b, the single turbo mode is set. In addition, the twin turbo mode is set under other conditions of low load and high speed of Tp ≦ Tps and N ≧ Nc, or high load medium and high speed of Tp> Tps and N ≧ Nb. In order to prevent hunting of operation and stop of the secondary turbocharger, hysteresis is provided for the operation stop set value Na.

Therefore, in S2, the basic injection amount Tp and the set value Tp
s, and if Tp ≦ Tps, the process proceeds to step S3, where the engine speed N is compared with the set value Nc.
If <Nc, it is determined that the mode is the single turbo mode, and the process proceeds to step S5. If Tp> Tps in step S2, the process proceeds to step S4, where the engine speed N and the set value Nb are set.
In the case of N <Nb, it is similarly determined that the single turbo mode is set.

In this single turbo control routine, in step S5, the output signal G1 of the switching solenoid valve 70 is set to 0, and the boost pressure relief valve 60 is opened by applying a negative pressure.
The supercharging pressure downstream of the blower 50b is leaked. In step S6, the output signal G2 of the switching solenoid valve 71 is set to 0, and a negative pressure is applied to the actuator 57 to cause the intake control valve 5 to operate.
8 is closed to prevent leakage of the supercharging pressure by the primary turbocharger 40.

Thereafter, in step S7, the output signal G3 of the first switching solenoid valve 73 is set to 0, the other chamber of the actuator 56 is opened to the atmosphere, and in step S8, the output signal G4 of the second switching solenoid valve 74 is released. Is set to 0, and one chamber of the actuator 56 is also opened to the atmosphere. The spring 56a of the actuator 56 closes the exhaust control valve 55 against the low exhaust pressure in the low to medium speed range, and shuts off exhaust gas from being introduced into the secondary turbocharger 50. 40 alone operating states are ensured.

In step S9, the duty ratio Dse of the secondary-side duty solenoid valve 53 is set to FFH (1
00%) and the waste gate valve 51 is fully closed. Thereafter, in step S10, the ROM 10 in which the optimum value in the single turbo mode obtained in advance through experiments or the like is stored based on the engine speed N and the throttle opening Th.
The target supercharging pressure Pt is set with reference to the single turbo mode target supercharging pressure map stored in 5 with interpolation calculation, and the secondary turbocharger operation determination flag F1 is cleared in step S11. In step S12, the count value C of the delay time is cleared.

Next, in the supercharging pressure control routine shown in FIGS. 5 and 6, first, in step S13, the target supercharging pressure Pt and the actual supercharging pressure Pt are determined.
b, and if the absolute value | Δp | of the deviation is smaller than the set value Δps in step S14,
It is determined that the actual supercharging pressure Pb has converged to the allowable range of the target supercharging pressure Pt, so that the integral control amount Di is made zero in step S15, and the proportional control amount Dp is made zero in step S16. Then, in step S17, the duty ratio D is changed to the previous value Do.
Is added to control amounts Dp and Di for integral and proportional components, and in this case, it becomes the same as the previous value Do. Then, in step S18, the value of the flag F1 is referred to,
In step S19, the duty ratio D is output as the duty ratio Dpr of the primary-side duty solenoid valve 43, and in step S20, the duty ratio D is stored as the previous value Do.

In this mode, when the absolute value | Δp | of the difference between the target supercharging pressure Pt and the actual supercharging pressure Pb becomes larger than the set value Δps, the process proceeds from step S14 to step S21, where the target supercharging of the actual supercharging pressure Pb is performed. The magnitude relationship with the supply pressure Pt is checked. Thus, as shown at t1 in FIG.
Is decreased, the duty ratio D is determined in step S22.
Referring to the value of the PI control determination flag F2 set to 1 at the time of the down correction, if F2 = 1 and the duty ratio D is increased for the first time, the integral control amount D is determined in step S23.
Set i to zero. Then, in step S24, the process proceeds to step S25 with reference to the value of the flag F1, and the proportional increase amount Pup1 corresponding to the deviation Δp is set.

Here, in the single turbo mode, the proportional control amount Dp is a solid line in the integral correction amount map in which the integral control amount Di is (d) as shown by the solid line in the proportional correction amount map in FIG. Is set in a step shape with a large control amount. In the twin turbo mode, the proportional control amount Dp and the integral control amount Di with respect to the deviation Δp are set based on the operation distribution of the turbochargers 40 and 50. Therefore, for example, when the operation distribution of the two turbochargers 40 and 50 is set to be equal, the control amounts Dp and Di for the proportional component and the integral component are set.
Need only be one type, so that FIG.
One control amount is set as shown by the broken line in (d).

For this reason, in step S25, the proportional increase amount Pup1 corresponding to the deviation Δp is set to a large value according to the above-mentioned map, and in step S26, the proportional increase amount Pup1 is determined as the proportional control amount Dp.
In step S27, the PI control determination flag F2 is cleared, and the process proceeds to step S17 and subsequent steps. Accordingly, the duty ratio Dpr of the primary-side duty solenoid valve 43 increases by the proportional control amount Dp, the opening of the waste gate valve 41 decreases, and the actual supercharging pressure Pb increases relatively greatly as shown in FIG.

After the second time, the process proceeds to step S28 according to the flag F2 in step S22, and refers to the value of the flag F1. In step S29, the integrated amount increase amount Iup1 corresponding to the deviation Δp is determined by the map shown in FIG. A search is made, and this is set as the integral control amount Di in step S30, and the proportional control amount Dp is set to zero in step S31. Therefore, in the case of the second time or later such as t2 in FIG.
i, the actual supercharging pressure Pb is gradually increased, and by these corrections, the actual supercharging pressure Pb follows the target supercharging pressure Pt. When the deviation Δp becomes smaller than the set value Δps and converges at t3, the process proceeds from step S14 to step S15 and thereafter, and the control is interrupted.

On the other hand, when the deviation Δp becomes larger than the set value Δps on the high side of the actual supercharging pressure Pb as shown at t5 in FIG. 8, the process proceeds from step S21 to step S32. In this case, the flag F2 is set to 0 by the above control. In the case of the first time according to the flag F2, the process proceeds to step S33 and subsequent steps. Therefore, the integral control amount Di is set to 0 in step S33, the process proceeds to step S35 by referring to the value of the flag F1 in step S34, and a proportional down amount Pdo1 corresponding to the deviation Δp is searched by the same map, and the process proceeds to step S36. Is determined as the proportional control amount Dp, and PI is determined in step S37.
The control discrimination flag F2 is set to 1 and the process proceeds to step S17 and subsequent steps. Therefore, the primary side duty solenoid valve 43
Is reduced by the proportional control amount Dp,
The opening degree of the waste gate valve 41 increases, and the actual supercharging pressure Pb decreases relatively largely as shown in FIG.

After the second time, the process proceeds to step S38 according to the flag F2 of step S32, and refers to the value of the flag F1.
Is searched for the integral down amount Ido1 corresponding to
At 40, this is set as the integral control amount Di, and
At 41, the proportional control amount Dp is set to 0. Therefore, t in FIG.
In the case of the second and subsequent times, such as 6, the actual supercharging pressure Pb is gradually reduced by the integral control amount Di. Thus, in the single turbo mode, the secondary turbocharger 50 does not operate, only the primary turbocharger 40 operates, and the opening degree of the waste gate valve 41 changes according to the PI control amount, so that the comparatively low turbocharger in this case is used. Feedback control is performed so that the actual boost pressure Pb always follows the target boost pressure Pt with good response.

Further, in this turbo mode, the exhaust control valve 5
5 is closed by spring force, when the waste gate valve 41 of the primary turbocharger 40 closes due to a failure and the exhaust pressure rises, the exhaust control valve 55
Opens a minute valve. Then, a part of the exhaust gas leaks through the secondary turbocharger 50, and thus the failsafe operation is performed so as to prevent the primary turbocharger 40 from blowing.

Next, in steps S2 to S4, Tp ≦
Tps, N ≧ Nc, or Tp> Tps, N ≧ Nb
If it is determined that the mode is the twin turbo mode, the preliminary rotation control routine of FIG. 4 is executed. First, in step S50,
Count value C of the time from the preliminary rotation start time ts in FIG. 9
Is compared with the first delay time T1, and if C <T1, the routine proceeds to step S51, where the count value C is incremented. Then, in step S52, the duty ratio Dpr of the primary side duty solenoid valve 43 is set to FFH, the waste gate valve 41 is fully closed, and the actual supercharging pressure Pb by the primary turbocharger 40 is slightly increased so that the output does not decrease. Is controlled. In step S53, the secondary-side duty solenoid valve 53 is also prepared so that the duty ratio Dse is set to FFH, the waste gate valve 51 is fully closed, and preliminary rotation can be performed efficiently.

When the count value C reaches the first delay time T1, the process proceeds from step S50 to step S54,
The output state of the switching solenoid valve 70 is checked, and if it is an open signal (G1 = 0), the output signal G1 of the switching solenoid valve 70 is set to 1 in step S55, and a positive pressure is applied to operate the supercharging pressure relief valve 60. Is closed as shown in FIG. Therefore, thereafter, the process proceeds from step S54 to step S56, where the count value C is compared with the second delay time T2, and if the time T2 is not reached, the count value C is incremented in the same manner as described above.

Therefore, in this case, the secondary turbocharger 50 can generate a supercharging pressure while the exhaust control valve 55 is closed by the spring 56a of the actuator 56. When the increased exhaust pressure in the medium speed region opposes the preset spring force of the spring 56a, the exhaust control valve 55 opens by a small opening θ as shown in FIG. Turbocharger 50
And the preliminary rotation is started smoothly.

When the second delay time T2 has been reached, the output state of the switching solenoid valve 73 is checked in step S57. If the output signal to the atmosphere is (G3 = 0), the first switching solenoid valve is switched in step S58. The output signal G3 of 73 is set to 1 to apply a positive pressure to one chamber of the actuator 56. In step S59, the output state of the switching solenoid valve 74 is checked, and in step S60, the output signal G4 of the second switching solenoid valve 74 is set to 1 in the atmospheric release signal (G4 = 0). Negative pressure is applied to this chamber, and the exhaust control valve 55 is fully opened as shown in FIG. Accordingly, the amount of exhaust gas introduced into turbine 50a of secondary turbocharger 50 increases, and the secondary supercharging pressure further increases.

Thereafter, in step S61, the count value C is compared with the third delay time T3.
In step S62, the output voltage E of the differential pressure sensor 80 is compared with a set value Es. Then, when the differential pressure becomes substantially zero, the output state to the switching solenoid valve 71 is checked in step S63, and if the closing signal (G2 = 0), the flow goes to step S64.
The output signal G2 of the switching solenoid valve 71 is set to 1, the actuator 57 is opened to the atmosphere, and the intake control valve 58 is opened by the spring force as shown in FIG. So in this case,
Proceeding from step S63 to step S65, the secondary turbocharger operation determination flag F1 is set to 1. For this reason, at the time point tg when the intake control valve 58 is opened, the secondary turbocharger 50 ends the preliminary rotation and substantially operates, and automatically shifts to the twin turbo mode with little torque fluctuation. .

In this twin turbo control routine, FIG.
The process proceeds from step S1 to step S70 to check the engine speed N against the set value Na for stopping the operation of the secondary turbocharger. If N ≧ Na, the output signals G1 to G4 for the switching solenoid valves of the respective valves are held in the above-described state in steps S71 to S74. In step S75, based on the engine speed N and the throttle opening Th, the twin turbo mode target supercharging pressure map is referred to with interpolation calculation, and the target supercharging pressure Pt in this mode is calculated as follows.
As shown in FIG. 7 (b), a higher eye is set. Then, the process proceeds to step S86, in which the secondary turbocharger operation determination flag F1 is set to 1, the count value C of the delay time is cleared in step S12, and steps S13, S14, S2 are performed.
In step 1, it is determined whether the actual supercharging pressure Pb follows the target supercharging pressure Pt. By the way, at the beginning of this mode, the waste gate valves 41, 51 of the primary and secondary turbochargers 40, 50 are both fully closed and are in a full operation state as in the above-described preliminary rotation. Specifically, the actual supercharging pressure Pb increases, and the deviation Δp increases on the higher side as shown at t5 in FIG.

Therefore, in the supercharging pressure control routine in this case, in the case of the first time, steps S21 to S32,
The process proceeds to step S76 via S33 and S34, and FIG.
The proportional down amount Pdo2 corresponding to the deviation Δp is searched using the broken line in the map of (c), and the duty ratio D is calculated in step S77 as the proportional control amount Dp. Further, the process proceeds from step S18 to S78 and S79, where the duty ratios Dpr and Dse of the primary and secondary duty solenoid valves 43 and 53 are equal, and the duty ratio D
And the actual supercharging pressure Pb is decreased by increasing the opening of both waste gate valves 41 and 51 equally. And 2
After the first time, the process proceeds from step S32 to step S80 via step S38, and the integral down amount Ido2 is searched using the broken line in the map of FIG.
By setting this to the integral control amount Di at 81, the actual supercharging pressure Pb is gradually reduced and approaches the target supercharging pressure Pt.

When the deviation Δp increases on the lower side of the actual supercharging pressure Pb as shown at t1 in FIG. 8, in the case of the first time, the process proceeds from step S21 to steps S82 and S83 via steps S22, S23 and S24. Then, the proportional control amount Dp is determined by the proportional increase amount Pup2 corresponding to the deviation Δp. 2
After the first time, the process proceeds from step S22 to step S84 via steps S28 and S85, and similarly calculates the duty ratio D by determining the integral control amount Di with the integral increase amount Iup2 corresponding to the deviation Δp. Then, the duty ratios Dpr, Dse of the primary and secondary duty solenoid valves 43, 53 are set equal to the duty ratio D, and the opening degree of the waste gate valves 41, 51 is reduced equally, so that the actual supercharging pressure Pb is increased. The actual boost pressure Pb follows the target boost pressure Pt. Thus, in this twin turbo mode, the primary and secondary turbochargers 40, 50 have their waste gate valves 41, 5 attached.
1, the two turbochargers 40,
The actual supercharging pressure Pb is controlled to an appropriate high level by the co-operation of 50.

Next, at the time of deceleration, the engine speed N is checked in step S70, and if it becomes lower than the secondary turbocharger operation stop set value Na, the flow proceeds to step S70.
From step S5. Then, the output signals G1 to G4 for the switching solenoid valves are inverted to open the boost pressure relief valve 60, and the intake control valve 58 and the exhaust control valve 5 are opened.
Close 5 and return to single turbo mode. FIG. 10 shows the control states and output characteristics of the single turbo mode and the twin turbo mode.

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

[0042]

As described above, according to the present invention,
In the exhaust control of the sequential turbo engine, the exhaust control valve also functions as the pre-control valve, so that the structure and control are simplified. Due to the relationship between the spring force of the actuator of the exhaust control valve and the exhaust pressure in each operating state, the exhaust control valve is closed in single turbo mode, and the exhaust control valve is automatically opened by a small opening in preliminary rotation mode for preliminary rotation. Can be performed smoothly. Since the transition from the preliminary rotation mode to the twin turbo mode is controlled by the change in the opening degree of the exhaust control valve, the secondary supercharging pressure rises smoothly, and the torque fluctuation can be reduced.

In the actuator of the exhaust control valve, the spring force of the spring is merely set to be equal to the force of the exhaust pressure in the operation state in the preliminary rotation mode, so that the structure can be simplified and made compact. Furthermore, in single turbo mode, when the waste gate valve of the primary turbocharger fails, exhaust gas is leaked by the exhaust control valve, so it is possible to reliably prevent the blowout of the primary turbocharger and improve the reliability of the turbocharger. I do.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating an apparatus suitable for implementing an exhaust control method for a sequential turbo engine according to the present invention.

FIG. 2 is an overall circuit diagram of a control system.

FIG. 3 is a flowchart showing a main routine of sequential turbo control.

FIG. 4 is a flowchart showing a preliminary rotation control routine.

FIG. 5 is a flowchart showing a correction of a decrease in a boost pressure control routine and the like.

FIG. 6 is a flowchart illustrating a boost correction and the like in a supercharging pressure control routine.

FIG. 7 is a diagram showing various maps.

FIG. 8 is a time chart showing a state of supercharging pressure control.

FIG. 9 is a time chart showing the opening / closing state of each valve and the state of supercharging pressure in the preliminary rotation mode.

FIG. 10 is a diagram showing control and output characteristics of a single turbo mode and a twin turbo mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 10, 11, 12 Exhaust pipe 16, 17, 18, 19 Intake pipe 36 Igniter 40 Primary turbocharger 50 Secondary turbocharger 100 Control unit

Claims (1)

(57) [Claims] 1. A primary turbocharger and a secondary turbocharger are arranged in parallel in an intake / exhaust system of an engine body, and a supercharging pressure relief valve, an intake control valve, and an exhaust control are provided on a secondary turbocharger side. the valve is provided to operate only the primary turbocharger is in single turbo mode, and controls so as to together operate a primary turbocharger and a secondary turbocharger twin turbo mode, single
In turbo mode, the actuator spring discharges
Close the air control valve and close the boost pressure relief valve during the pre-rotation
The exhaust pressure in this operating state causes the exhaust control valve to
Open, and after a predetermined time delay, open the exhaust control valve and feeder control valve.
In the exhaust control method for a sequential turbo engine that is controlled to open and shift to the twin turbo mode, the exhaust control valve is opened downstream and the actuator has
The spring is biased in the closing direction, and the spring
The pulling force is the force due to the exhaust pressure in the operating state during the preliminary rotation.
And the actuator of the exhaust control valve is a single turbo motor.
To open two chambers to the atmosphere,
Fully open exhaust control valve by applying negative pressure and positive pressure to two chambers
Exhaust control method of sequential turbo engine, characterized in that it is controlled such.