JPH086604B2 - Failure diagnosis 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 equipped with a plurality of turbochargers and operating in a sequential turbo system as a vehicle engine,
TECHNICAL FIELD The present invention relates to a failure diagnosis method for a sequential turbo engine, in which all valves on the secondary turbocharger side are properly diagnosed for failure, and failsafe is appropriately performed at the time of failure.

[0002]

2. Description of the Related Art In recent years, as a supercharged engine for a vehicle, a primary and secondary turbocharger are installed in parallel in a multi-cylinder exhaust system, and the turbocharger is operated in a sequential turbo system. Things have been proposed. In this sequential turbo engine, generally, an intake control valve, a relief valve, an exhaust control valve and the like are provided on the secondary turbocharger side, and these valves are controlled to open and close when switching the turbo mode. By the way, since each of these valves is configured to operate by an electric signal and air pressure,
A variety of causes are expected to cause a failure to stick in the open or closed state. If, for example, a failure occurs in the single turbo mode while the exhaust control valve remains open, the single turbo mode has no meaning. Further, in the twin turbo mode, for example, if the exhaust control valve fails while it is closed, a problem such as excessive rotation of the primary turbocharger may occur. For this reason, it is possible to accurately diagnose the presence or absence of failure of these valves,
In case of a failure, it is desirable to properly fail safe.

Conventionally, as for the failure diagnosis of the above-mentioned sequential turbo engine, for example, Japanese Patent Laid-Open No. 2-136516.
There is a prior art of Japanese Patent Laid-Open Publication No. JP-A-2003-242, in which the operating state of the exhaust cut valve is detected by the compressor outlet pressure, and the exhaust energy is reduced when the opening operation is defective. In addition, JP-A-2-24862
The prior art of Japanese Patent Publication No. 3 discloses that the operating state of the intake cut valve is detected by the blower outlet pressure, and when it is fixed in the closed state, the engine output is reduced in the high intake amount region.

[0004]

By the way, in the above-mentioned prior art, since a method of individually detecting the presence or absence of a failure of the exhaust cut valve and the intake cut valve, many failure detection means are required. Also, the control of failure diagnosis becomes complicated. In addition, there is a problem that other valve failure diagnosis cannot be performed. Originally, it is necessary that all the valves normally operate when switching to the turbo mode, and even if any one valve fails, the turbo operation cannot be normally performed in each turbo mode. Therefore, it can be said that it is meaningless to detect the presence or absence of failure of each valve.

The present invention has been made in view of this point, and it is an object of the present invention to appropriately perform a failure diagnosis on all valves on the secondary turbocharger side and appropriately perform fail-safe in the case of a failure.

[0006]

In order to achieve the above object, the present invention provides a secondary turbocharger in which a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake / exhaust system of an engine body. At least the relief valve, the intake control valve, and the exhaust control valve are provided on the machine side, and only the primary turbocharger operates in the single turbo mode,
In the twin turbo mode, in the sequential turbo engine that controls to operate both the primary turbocharger and the secondary turbocharger, the upstream pressure and the downstream pressure of the intake control valve for each of the single turbo mode, the preliminary rotation mode and the twin turbo mode. The presence / absence of any failure of the relief valve, the intake control valve, and the exhaust control valve is diagnosed based on the pressure difference from the pressure.

[0007]

In the above control method, when the relief valve, the intake control valve, and the exhaust control valve on the secondary turbocharger side all operate normally during engine operation, and when any one of them operates reversely due to a sticking abnormality. In this case, the change in the differential pressure between the upstream pressure and the downstream pressure of the intake control valve is used. By diagnosing the failure based on this differential pressure for each mode, the presence or absence of any failure of all the valves can be accurately diagnosed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, the overall configuration of a horizontally opposed engine equipped with a sequential turbocharger will be described. Reference numeral 1 is an engine body of a horizontally opposed engine, and is provided in the left and right banks 3 and 4 of the crankcase
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. Further, the primary turbo supercharger 40 and the secondary turbo supercharger 50 are respectively arranged immediately after the left and right banks 3 and 4 due to this engine shortening shape. Left and right banks 3, 4 as exhaust system
Is connected to the turbines 40a and 50a of both turbochargers 40 and 50, and the common exhaust pipe 10 from
The exhaust pipe 11 from 50a joins with one exhaust pipe 12, and is connected to the catalytic converter 13 and the muffler 14.

As an intake system, intake pipes 16 and 17 branched from the air cleaner 15 are connected to blowers 40b and 50b of the turbochargers 40 and 50, respectively, and intake pipes 18 and 50 from the blowers 40b and 50b are connected to each other. 19 is 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, an idle control valve 25 and a check valve 2 opened by negative pressure are provided in a bypass passage 24 between the intake manifold 23 and the downstream side of the air cleaner 15.
6 is provided to control the intake air amount during idling or deceleration.

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

The operation system of the primary turbocharger 40 will be described. The primary turbocharger 40 uses the energy of the exhaust gas introduced to the turbine 40a to blower 40b.
It is driven to rotate and sucks and pressurizes air to always supercharge. A waste gate valve 41 provided with 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. Further, the control pressure passage 44 communicates the 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 to cause a waste gate valve. 41
The supercharging pressure is controlled by changing the opening degree of.
Here, for example, when the duty ratio is large, the control pressure is decreased due to the increase in the leak amount, the opening degree of the waste gate valve 41 is reduced, and the supercharging pressure is increased. On the contrary, when the duty ratio becomes small, the opening degree is increased by the high control pressure to reduce the supercharging pressure.

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

The operation system of the secondary turbocharger 50 will be described. Similarly, 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 immediately 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 that leak to the atmosphere, and when the boost pressure rises above a set value, the waste response is good. The gate valve 51 is opened, and a control pressure is generated by the duty solenoid valve 53 so that the boost 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 boost pressure relief valve 60 is connected between the upper side and the lower side of 0b.

Explaining the pressure operation system of each of these valves, the passage 61 from the intake manifold 23 has a check valve 62 and is communicated with a surge tank 63 to store a negative pressure when the throttle valve is fully closed and a pulsating pressure. 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 communicate with one spring chamber of the boost pressure relief valve 60 via a switching solenoid valve 70 and a passage 66. It 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.
It is communicated via 8. 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 the spring force when the atmosphere is opened.

The exhaust control valve 55 is constructed so as 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 switching solenoid valve 74 for switching between atmospheric pressure and negative pressure is communicated with one chamber having the spring 56a of the actuator 56 through a passage 69, and the other chamber is switched between positive pressure and atmospheric pressure. The first switching solenoid valve 73 is connected via the passage 75. In the single turbo mode, the first and second switching solenoid valves 73 and 74 are operated by an electric signal to open both chambers to the atmosphere and fully close the exhaust control valve 55 by the 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. Further, even in the preliminary rotation mode, this state is maintained for a predetermined time, and the function of a pre-control valve is provided by opening a minute opening degree by the balance between the exhaust pressure and the spring force. Further, in the twin turbo mode, a negative pressure is applied to one chamber and a positive pressure is applied to the other chamber so that the exhaust control valve 55 is fully opened and is kept in the fully opened state.

Explaining various sensors, a differential pressure sensor 80 is provided so as to detect a differential pressure upstream and downstream of the intake control valve 58, and an absolute pressure sensor 81 is connected to the intake pipe pressure by a switching solenoid valve 76. It is provided to select and detect atmospheric pressure. Further, the engine body 1 is provided with a crank angle sensor 82, a knock sensor 83, and a water temperature sensor 84, and a cam angle sensor 85 is provided so as to face a cam rotor (not shown) connected to the cam shaft of the valve operating mechanism 9, 10 is provided with an O2 sensor 86, and the throttle valve 21
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.

The overall structure of the electronic control system will be described with reference to FIG. 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.
Then, electric power is supplied from the battery 92 to the constant voltage circuit 106 to execute various controls of the control unit 100, and the drive circuit 107 turns on the relay 93 to energize and drive the fuel pump 31. The CPU 102 inputs signals from the various sensors 80 to 88 and the vehicle speed sensor 89 from the I / O 101 on the basis of an arithmetic program stored in the ROM 105,
The arithmetic processing is performed based on the data stored in the RAM 103 and the backup RAM 104 and the fixed data such as a map stored in the ROM 105. And drive circuit 1
07 to various switching solenoid valves 70, 71, 73, 7
A switching signal to the duty solenoid valve 43,
A duty signal is output to 53 to perform sequential turbo control, and an injection signal is output to the injector 30 to control fuel injection. An ignition signal is output to the igniter 36 to control the ignition timing, and a control signal is output to the idle control valve 25 to control the idle speed.

Here, the failure diagnosis of various valves on the secondary turbocharger side will be described. First, the normal opening / closing operation states of the exhaust control valve 55, the intake control valve 58, and the boost pressure relief valve 60 attached to the secondary turbocharger 50 in each mode are shown in Table 1 below. .

[0019]

[Table 1]

Therefore, if any of the valves is opened or closed in the opposite mode, the sticking abnormality occurs. Therefore, in the single turbo mode, for example, when the exhaust control valve 55 is stuck open, the upstream pressure Pu of the intake control valve 58 rises during supercharging and becomes substantially equal to or higher than the downstream pressure Pd of the intake control valve 58. Even when the differential pressure ΔPdi (= Pu-Pd) between the upstream pressure Pu and the downstream pressure Pd of the intake control valve 58 shows an abnormal value, and the intake control valve 58 is stuck open or the boost pressure relief valve 60 is stuck closed. It will be similar. Further, in the preliminary rotation mode, for example, when the exhaust control valve 55 is stuck closed, the upstream pressure Pu of the intake control valve 58 does not rise and the differential pressure ΔPdi becomes abnormally large on the minus side. Also, in the twin turbo mode, for example, when the intake control valve 58 is stuck closed, the upstream pressure Pu rises abnormally, the differential pressure ΔPdi becomes abnormally large, and the boost pressure relief valve 60 opens stuck. , The upstream pressure Pu does not rise and the differential pressure ΔPdi becomes abnormally large on the minus side. In this way, by detecting the differential pressure ΔPdi of the upstream pressure and the downstream pressure of the intake control valve 58 in each mode, the failure diagnosis of all the valves 55, 58, 60 can be collectively performed.

Therefore, the diagnostic condition determination flag F3 stored in the backup RAM 104 is used to perform a failure diagnosis during control of each mode, and the diagnostic result for each mode is stored in a predetermined address of the backup RAM 104 as a diagnostic result flag Fng1. , Fng2, Fng3. In the case of a failure, the user is notified by lighting an alarm lamp 111 provided on an instrument panel (not shown). Therefore, if a failure occurs, the serial monitor (vehicle diagnostic device) 110 is connected to the I / O 101 of the control unit 100 in the dealer via the connector 112.
Is connected and the failure data by the diagnosis result flags Fng1, Fng2, Fng3 of the backup RAM 104 are read out, and it becomes possible to find the failure of any valve and repair it. After the repair, the failure diagnosis control is executed again, or the serial monitor 110 clears the diagnosis result flags Fng1, Fng2, Fng3 to restore the original condition. The serial monitor 110 is described in detail in Japanese Patent Application Laid-Open No. 2-73131 filed by the present applicant.

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, referring to the value of the twin turbo mode determination flag F1 which is set to 1 in the twin turbo mode in step S1, if the secondary turbo supercharger 50 is inactive with F1 = 0, 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 fuel injection amount Tp as an example showing the engine load and the set values Tps, Nb, Nc for starting the operation of the secondary turbocharger with respect to the engine speed N. Each turbo mode is given. That is, Tp ≦ Tp
s, N <Nc, low load / medium speed, or Tp> Tps, N
Under the conditions of high load and low speed of <Nb, the single turbo mode is set. In addition, the twin turbo mode is set under the other conditions of Tp ≦ Tps, N ≧ Nc, low load and high speed, or Tp> Tps, N ≧ Nb, high load, medium and high speed. still,
A hysteresis is provided in the operation stop set value Na in order to prevent hunting of operation and stop of the secondary turbocharger.

Therefore, in step S2, the basic injection amount Tp is compared with the set value Tps. If Tp≤Tps, the process proceeds to step S3, where the engine speed N is compared with the set value Nc and N <Nc. It is determined to be single turbo mode. If Tp> Tps in step S2, the process proceeds to step S4, the engine speed N is compared with the set value Nb, and if N <Nb, the single turbo mode is similarly determined.

In this single turbo mode, first, the routine proceeds to step S90, where the diagnostic condition determination flag F3 is cleared. This failure condition determination flag F3 is referred to in a failure diagnosis routine described later, and when F3 = 0, failure diagnosis is performed for each valve 55, 58, 60 under the condition of the single turbo mode, and F3 = In the case of 1, failure diagnosis is performed under the conditions of the preliminary rotation mode and the twin turbo mode. After that, in step S91, the value of the first diagnosis result flag Fng1 indicating the failure diagnosis result under the single turbo mode condition is referred to, and if Fng1 = 0 is normal, the process proceeds to step S5 and thereafter to execute the single turbo control routine. To do. The failure diagnosis control and the fail safe at the time of failure will be collectively described later.

In this single turbo control routine, the output signal G1 to the switching solenoid valve 70 is output in step S5.
Is set to 0, a negative pressure is applied to the boost pressure relief valve 60 to open the boost pressure relief valve 60, and the boost pressure downstream of the blower 50b is leaked. Further, in step S6, the output signal G2 to the switching solenoid valve 71 is set to 0, a negative pressure is applied to the actuator 57 to close the intake control valve 58, and leakage of the boost pressure by the primary turbocharger 40 is prevented.

Thereafter, in step S7, the output signal G3 to 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 to the second switching solenoid valve 74 is output. The signal G4 is set to 0, and one chamber of the actuator 56 is also open to the atmosphere. Then, the spring 56a of the actuator 56 closes the exhaust control valve 55 against the low exhaust pressure in the low and medium speed range to block the exhaust from being introduced into the secondary turbocharger 50. Forty independent operation states are ensured.

Further, in step S9, the duty ratio D of the control signal to the secondary side duty solenoid valve 53 is set.
se is set to FFH (100%), and the waste gate valve 51 is fully closed. Then, in step S10, based on the engine speed N and the throttle opening Th, the single turbo mode target supercharging pressure map stored in the ROM 105 in which the optimum value in the single turbo mode obtained in advance by experiments or the like is stored. The target turbocharging pressure Pt is set with reference to the interpolation calculation, and the twin turbo mode determination flag F1 is cleared in step S11. Then step S12
Clear the count value C of the delay time with.

Next, in the supercharging pressure control routine of FIGS. 5 and 6, first, at step S13, the target supercharging pressure Pt and the actual supercharging pressure P are calculated.
If the deviation Δp of b is calculated and the absolute value of the deviation | Δp | is smaller than the set value Δps in step S14, the actual supercharging pressure Pb converges to the allowable range of the target supercharging pressure Pt. If it is determined that the proportional control amount D i is zero in step S15, the proportional control amount D p is also zero in step S16. Then, in step S17, the duty ratio D is obtained by adding the control values Dp and Di for the integral and proportional portions to the previous value Do, and in this case, it is the same as the previous value Do. After that, in step S18, the value of the flag F1 is referred to,
Since it has already become 0, the duty ratio D is output as the duty ratio Dpr of the primary side duty solenoid valve 43 in step S19, and this duty ratio D is stored as the previous value Do in step S20.

In this mode, when the absolute value | Δp | of the deviation 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 and the target supercharging pressure Pb of the target supercharging pressure Pb is increased. The magnitude relationship with the supply pressure Pt is checked. Therefore, as shown at t1 in FIG.
Under the condition that the duty ratio has decreased, the duty ratio D
If the value of the PI control determination flag F2 set to 1 at the time of the down correction is referred to, and F2 = 1 and the duty ratio D is increased for the first time, the integrated control amount D is calculated in step S23.
i is set to zero. Then, in step S24, the value of the flag F1 is referred to, and the flow proceeds to step S25 to set the proportional amount Pup1 for proportional increase in accordance with the deviation Δp.

Here, in the single turbo mode, the proportional control amount Dp is the solid line of the proportional correction amount map of FIG. 7C, and the solid line of the integral correction amount map of the integral control amount Di is (d). As shown in FIG. Further, 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 both turbochargers 40 and 50. Therefore, for example, when the operation distributions of both turbochargers 40 and 50 are set to be equally divided, the control amounts Dp and Di for the proportional portion and the integral portion are set.
Therefore, only one type is required. Therefore, as shown in FIG.
One control amount is set as indicated by the broken line in (d).

Therefore, in S25, the proportional increase amount Pup1 corresponding to the deviation Δp is set to a larger value in the map, and in step S26, this is set 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. Therefore, the duty ratio Dpr of the primary side duty solenoid valve 43 is increased by the proportional control amount Dp, the opening degree of the waste gate valve 41 is reduced, and the actual boost pressure Pb is relatively increased as shown in FIG.

After the second time, the process proceeds to step S28 with the flag F2 in step S22 and refers to the value of the flag F1. In step S29, the integrated increment Iup1 corresponding to the deviation Δp is calculated from the map of FIG. 7D. Search for
In step S30, this is set as the integral control amount Di, and in step S31, the proportional control amount Dp is set to zero. Therefore, in the case of the second and subsequent times such as t2 in FIG. 8, the actual supercharging pressure Pb is gradually increased by the integrated control amount Di, and the actual supercharging pressure Pb follows the target supercharging pressure Pt by these corrections. To do. Then, when the deviation Δp becomes smaller than the set value Δps and converges at t3, steps S14 to S15.
Then, control is interrupted.

On the other hand, when the deviation Δp becomes larger than the set value Δps on the side where the actual supercharging pressure Pb is high, as at t5 in FIG. 8, the routine proceeds from step S21 to step S32. In this case, the flag F2 is set to 0 by the above-mentioned control. Therefore, if the flag F2 is the first time, the process proceeds to step S33 and the subsequent steps. Therefore, in step S33, the integral control amount Di is set to 0, the value of the flag F1 is referred to in step S34, and the process proceeds to step S35. In the same map, the proportional down amount Pdo1 corresponding to the deviation Δp is searched, This is set as the proportional control amount Dp in S36, and PI is set in Step S37.
The control determination flag F2 is set to 1 and the process proceeds to step S17 and thereafter. Therefore, the primary side duty solenoid valve 43
The duty ratio Dpr of is decreased by the proportional control amount Dp,
The opening degree of the waste gate valve 41 is increased, and the actual boost pressure Pb is relatively lowered as shown in FIG.

After the second time, the flow advances to step S38 by the flag F2 in step S32, the value of the flag F1 is referred to, and the deviation Δ is calculated in the same map in step S39.
The integrated down amount Ido1 corresponding to p is searched, and this is set as the integrated control amount Di in step S40, and the proportional control amount Dp is set to 0 in step S41. Therefore, in the case of the second time or later such as t6 in FIG. 8, the actual supercharging pressure Pb is gradually reduced by the integrated control amount Di. Thus, in this single turbo mode, the secondary turbocharger 50
Is not activated, only the primary turbocharger 40 is activated,
Further, due to the change in the opening degree of the waste gate valve 41 due to the PI control control amount, feedback control is performed so that the actual supercharging pressure Pb always follows the relatively low target supercharging pressure Pt in good response.

Then, in steps S2 to S4, Tp≤
When Tps, N ≧ Nc, or Tp> Tps, N ≧ Nb
In the case of, when the twin turbo mode is set, the preliminary rotation mode is initially determined. In this mode, the process proceeds from step S4 to step S92, the diagnostic condition determination flag F3 is set, the process proceeds to step S50, and the preliminary rotation control routine is executed.

In this preliminary rotation control routine, as shown in FIG. 4, first, in step S50, the count value C of the time from the preliminary rotation control start time ts in FIG. 9 is set to the first delay time T.
If C <T1 as compared with 1, the process proceeds to step S51 to increment the count value C. Then, in step S52, the duty ratio Dpr of the primary side duty solenoid valve 43 is set to FFH to fully close the waste gate valve 41, and the actual supercharging pressure Pb by the primary turbocharger 40 is slightly increased so that the output does not decrease. Controlled by. 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 the 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 to the switching solenoid valve 70 is checked, and if an open signal (G1 = 0), the output signal G1 to the switching solenoid valve 70 is set to 1 in step S55, and a positive pressure is applied to the supercharging pressure relief valve 60. Acting on boost pressure relief valve 60
Is closed as shown in FIG. Therefore, after this step S5
The process proceeds from step 4 to step S56, 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 as described above.

On the other hand, at this time, the exhaust control valve 55 is in the state of being closed by the spring 56a of the actuator 56, and the exhaust pressure acts on this spring force in opposition. Therefore, when the exhaust pressure overcomes the spring force under the operating condition of the preliminary rotation mode, the exhaust control valve 55 opens by a small opening θ as shown in FIG. 9, and a part of the exhaust gas is discharged from the secondary turbocharger 50.
It is introduced into the turbine 50a and the preliminary rotation is smoothly started.

When the second delay time T2 is reached, the output state to the switching solenoid valve 73 is checked in step S57, and if the atmosphere release signal (G3 = 0), the first switching solenoid valve 73 is checked in step S58. The output signal G3 to 73 is set to 1, and a positive pressure is applied to one chamber of the actuator 56. Further, in step S59, the output state to the second switching solenoid valve 74 is checked, and in the case of the atmosphere open signal (G4 = 0), step S6
At 0, the output signal G4 to the second switching solenoid valve 74 is set to 1 and a negative pressure is applied to the other chamber of the actuator 56, and thus the exhaust control valve 55 is fully opened as shown in FIG. As a result, the amount of exhaust gas introduced into the turbine 50a of the secondary turbocharger 50 is increased, and the secondary supercharging pressure is further increased.

Thereafter, in step S61, the count value C is compared with the third delay time T3. When the time T3 is reached, the upstream pressure Pu and the downstream pressure Pu of the intake control valve 58 detected by the differential pressure sensor 80 in step S62. Differential pressure from Pd ΔP
The di (= Pu-Pd) is compared with the set value -A (a value slightly smaller than 0). When ΔPdi ≧ −A and the differential pressure becomes substantially zero, the output state to the switching solenoid valve 71 is checked in step S63, and the closing signal (G2 =
In the case of 0), the switching solenoid valve 71 is selected in step S64.
The output signal G2 to the intake control valve 5 as shown in FIG.
Open eight. When the intake control valve 58 opens, step S
In step S65, the twin turbo mode determination flag F1 is set to 1. Therefore, the intake control valve 5
At the opening timing tg of 8, the secondary turbocharger 50 finishes the preliminary rotation and substantially operates, and automatically shifts to the twin turbo mode in a state where the torque fluctuation is small.

Then, in this twin turbo mode, FIG.
From step S1 to step S70, the engine speed N is checked against the set value Na for stopping the operation of the secondary turbocharger. If N ≧ Na, the routine proceeds to step S93, where the diagnostic condition determination flag F3 is set, and the twin turbo control routine from step S71 is executed.

In this twin turbo control routine, the output signals G1 to G4 to the switching solenoid valves of the respective valves are held in the above-mentioned states in steps S71 to 74. In step S75, the engine speed N and the throttle opening Th are set.
Based on and, referring to the target turbocharging pressure map of the twin turbo mode with interpolation calculation, the target supercharging pressure Pt of this mode is referred to.
Is set to the high eye as shown in FIG. After that, the process proceeds to step S86, the twin turbo mode determination flag F1 is set to 1, the delay time count value C is cleared in step S12, and the actual supercharging pressure Pb follows the target supercharging pressure Pt in steps S13, S14, and S21. To judge. By the way, in the initial stage of this mode, the waste gate valves 41 and 51 of the primary and secondary turbochargers 40 and 50 are both fully closed and in a fully operating state as in the case of the above-described preliminary rotation. Actually, the actual supercharging pressure Pb rises, and the deviation Δp increases on the higher side as t5 in FIG.

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

When the deviation Δp becomes large on the side where the actual boost pressure Pb is low as at t1 in FIG. 8, in the case of the first time, the process proceeds from step S21 to steps S82, S83 via steps S22, S23, S24, and the like. Then, the proportional control amount Dp is determined by the proportional increase amount Pup2 according to the deviation Δp. Two
From the second time onward, the process proceeds from steps S22 to S28 to steps S84 and S85, and similarly, the integral control amount Di is determined by the integral increment amount Iup2 corresponding to the deviation Δp to calculate the duty ratio D. Then, the duty ratios Dpr, Dse of the primary and secondary duty solenoid valves 43, 53 are set to be equal to each other, and the opening ratios of both waste gate valves 41, 51 are reduced to increase the actual boost pressure Pb. , The actual supercharging pressure Pb follows the target supercharging pressure Pt. Thus, in this twin turbo mode, the primary and secondary turbochargers 40, 50 have their waste gate valves 41,
The turbocharger 4 will always operate in equal parts by 51.
The actual supercharging pressure Pb is controlled to an appropriate high level by the cooperation of 0 and 50.

Next, at the time of deceleration, the engine speed N is checked at step S70, and if it falls below the secondary turbocharger operation stop set value Na, the routine proceeds from step S70 to step S90 and thereafter. When the first diagnosis result flag Fng1 is cleared, the output signals G1 to G4 for the switching solenoid valves are inverted, the boost pressure relief valve 60 is opened, and the intake control valve 58 and the exhaust control valve 55 are opened. To close and return to single turbo mode. As above, the control states of the single turbo mode and the twin turbo mode,
The output characteristics are collectively shown in FIG.

Next, the failure diagnosis control in each mode and the fail-safe in case of failure will be described with reference to the flowcharts of FIG. The failure diagnosis routine of FIG. 11 is executed every predetermined time. First, referring to the value of the diagnostic condition determination flag F3 in step S100, since F3 = 0 in the single turbo mode, the process proceeds to step S101, and the preset operation of the throttle opening Th and the engine speed N is performed. Check if you are driving in the area,
If it is not within this range, it is determined that the diagnostic condition is not satisfied, and the first diagnostic time count value Cng1 is cleared in step S102.

If the diagnostic condition is satisfied in the single turbo mode, the routine proceeds to step S103, where the differential pressure ΔPdi (= Pu-Pd) between the upstream pressure Pu and the downstream pressure Pd of the intake control valve 58 by the differential pressure sensor 80 is set. The value is compared with the set value -P1 (a value slightly smaller than 0, but -P1≤-A). Here, when all of the exhaust control valve 55, the intake control valve 58, and the boost pressure relief valve 60 are normal, ΔPdi <−
When it is determined to be normal by P1, the process proceeds to step S104, and the first diagnosis result flag Fng1 is cleared. On the other hand, when the differential pressure ΔPdi is reduced due to the sticking abnormality of any one of the valves, the routine proceeds to step S105, where the first diagnosis time count value Cn
g1 is counted up, and thereafter, in step S106, the count value Cng1 and the set value Cs1 are compared, and the set value C
When s1 is reached, the first diagnosis result flag Fng1 is set in step S107.

When the failure diagnosis in the single turbo mode is completed in this way, the third and second diagnosis time count values Cng3 and Cng2 and the twin turbo mode elapsed time count value Co are cleared in steps S108 to 110. After that, in step S111, the first diagnosis result flag Fng1 is referred to. If Fng1 = 1 and there is a sticking abnormality, the process proceeds to step S112, the output signal G5 to the alarm lamp 111 is set to 1 and the alarm lamp 111 is turned on to inform the user .

Therefore, in the single turbo mode and in the operating region set by the predetermined throttle opening Th and the engine speed N, the differential pressure ΔPdi of the upstream and downstream pressures of the intake control valve 58 by the differential pressure sensor 80 is set. When the state of the value −P1 or more is continued for a predetermined time (Cng1 ≧ Cs1), that is, the upstream pressure Pu of the intake control valve 58 rises despite the single turbo mote and the exhaust control valve 55 and the intake control valve 5
When it is determined that at least one of 8 is in the valve open state (valve open fixation) or the boost pressure relief valve 60 is in the valve closed state (valve close fixation), the first diagnosis result flag Fng1 is set (Fng1 ← 1. ) Is done.

This first diagnosis result flag Fng1 is referred to in step S91 of the above-mentioned sequential turbo control routine (FIG. 3), and in the case of the sticking abnormality in the single turbo mode of Fng1 = 1, step S9.
Jump to 3 or later to force twin turbo mode. That is, in the single turbo mode, when one of the valves is reversely operated due to the sticking abnormality, the normal state in the twisten turbo mode is enabled and the turbo operation can be normally performed, and the upstream pressure Pu of the intake control valve 58 is reduced. In order to prevent a failure of the secondary turbocharger 50 due to the rise, the twin turbo mode is forcibly switched to fail-safe.

Next, in the pre-rotation mode or the twin turbo mode in which F3 = 1, the process proceeds from step S100 to step S113, and the output signal G2 for operating the intake control valve is referred to. Then, before the intake control valve open signal of G2 = 0 is output, the preliminary rotation mode is determined and the process proceeds to step S114 to compare the differential pressure ΔPdi with the set value −P3 (≈−A). Here, when all of the exhaust control valve 55, the intake control valve 58, and the supercharging pressure relief valve 60 are normal, the upstream pressure Pu of the intake control valve 58 rises and becomes ΔPdi> −P3, so it is determined to be normal. Then, the process proceeds to step S115, and the third diagnosis result flag Fng3 is cleared. In step S116, the third diagnostic time count value (Cng3) is cleared, and the process proceeds to step S120.

On the other hand, when ΔPdi ≦ −P3, the routine proceeds to step S117, where the third diagnostic time count value Cng.
3 is counted up, and then, in step S118, the count value Cng3 is compared with the set value Cs3 (however, a value corresponding to a time longer than the second delay time T2 and shorter than the third delay time T3). When the set value Cs3 is reached, it is determined that the exhaust control valve 55 is closed, and the third diagnosis result flag Fng3 is set in step S119. When the failure diagnosis in the preliminary rotation mode is completed in this way, the count values Cng1, Cng2, Co of other diagnosis times and the like are similarly cleared in steps S120, 119, 110. After that, in step S132, the value of the third diagnosis result flag Fng3 is referred to, and if Fng3 = 1 and the fixation is abnormal, the process proceeds to step S112, and the alarm lamp 111 is turned on.

Therefore, in the pre-rotation mode, when the differential pressure ΔPdi of the downstream pressure above the intake control valve 58 is kept below the set value −P3 for a predetermined time (Cng3 ≧ Cs3),
That is, before the intake control valve 58 in the pre-rotation mode is opened, the upstream pressure Pu of the intake control valve 58 does not increase and the exhaust control valve 55 is determined to be in the closed state (closed valve sticking). 3 diagnosis result flag Fng3 is set (Fng3 ← 1)
Is done. This third diagnosis result flag Fng3
Is referred to in the fuel cut determination routine described later, and Fn in the pre-rotation mode or the twin turbo mode.
Fuel cut is performed when g3 = 1.

After the intake control valve open signal of G2 = 1 is output, the twin turbo mode is determined, and the process proceeds from step S113 to step S122 in FIG. 12 to compare the twin turbo mode elapsed time count value Co with the set value Cso. , C
If o <Cso and the predetermined time indicated by Cso has not elapsed after the transition to the twin turbo mode, the twin turbo mode elapsed time count value Co is determined in step S123.
Is counted up and the process proceeds to step S126. When the set time elapses after the transition to the twin turbo mode (C
o ≧ Cso), the absolute value of the differential pressure | Δ in step S124
Pdi | is compared with the set value P2. Exhaust control valve 5
5. If both the intake control valve 58 and the boost pressure relief valve 60 are normal, the upstream pressure Pu and the downstream pressure Pd of the intake control valve 58 become substantially equal, so the routine proceeds to step S125, where the second diagnosis result flag is set. Clear Fng2. In step S126, the second diagnosis time count value Cng2 is cleared, and the process proceeds to step S130.

On the other hand, if | ΔPdi | ≧ P2, the process proceeds to step S127, where the second diagnostic time count value Cn
After counting up g2, the count value Cng2 and the set value Cs2 are compared in step S128, and when the set value Cs2 is reached, the intake control valve 58 is stuck closed or the boost pressure relief valve 60 is stuck open. Judge, step S
At 129, the second diagnosis result flag Fng2 is set.
When the failure diagnosis in the twin turbo mode is completed in this way, the first and third diagnosis time count values Cng1 and Cng3 are cleared in steps S130 and S131. After that, in step S121, the value of the second diagnosis result flag Fng2 is referred to, and in the case of the fixation abnormality, the process proceeds to step S112, and the alarm lamp 111 is turned on.

Therefore, in the twin-turbo mode, when the absolute value | ΔPdi | of the differential pressure of the upstream and downstream of the intake control valve 58 is equal to or more than the set value P2, it can be considered that the transition to the twin-turbo mode is complete (Co ≧ Cso) for a predetermined time (Cng2 ≧ Cs2), that is, despite the twin turbo mode, the upstream pressure Pu of the intake control valve 58 does not rise and the boost pressure relief valve 60 is in the open state (open. When it is determined that the intake control valve 58 is in the closed state (closed valve is stuck), the upstream pressure Pu of the intake control valve 58 is abnormally increased in the twin turbo mode. 2 diagnostic result flag Fng2 is set (Fng2
← 1) is done. This second diagnosis result flag Fn
Similarly to the third diagnosis result flag Fng3, g2 is referred to in a fuel cut determination routine described later, and the fuel cut is performed when Fng2 = 1 in the preliminary rotation mode or the twin turbo mode.

As described above, the exhaust control valve 55, the intake control valve 58, and the supercharging pressure relief valve 60 are opened by making a judgment based on the differential pressure ΔPdi of the upstream and downstream pressures of the intake control valve 58 by the differential pressure sensor 80. It is possible to diagnose both sticking and closed sticking. In addition, each diagnostic result flag Fng1, Fng
2, Fng3 is the back-up RAM 10 as described above.
4 and the value of each diagnostic result flag is read by the serial monitor 110, so that the repair worker can know the details of the failure. The initial value of each diagnosis result flag is 0.

If the failure diagnosis in each of the above modes is normal, the process proceeds to step S133 and the alarm lamp 1
By setting the output signal G5 for 11 to 0, the alarm lamp 111 remains off.

Next, the fail-safe at the time of failure of the above-mentioned preliminary rotation mode and twin turbo mode will be explained. Switching to the single turbo mode in the case of this failure undesirably causes over-rotation of the primary turbocharger 40. Further, the secondary turbocharger or the like may be damaged by heat damage or the like due to an abnormal increase in the upstream pressure Pu of the intake control valve 58, and therefore it is desired to reduce the engine output. Therefore, as a means for reducing the engine output, the case of fuel cut will be described with reference to the flowcharts of FIGS. 13 and 14.

FIG. 13 shows a fuel cut determination routine.
It is executed every predetermined time. First, in step S140, the vehicle speed V
Is compared with the vehicle speed limit Vmax, and if the vehicle speed limit is exceeded, the fuel cut flag Ffc is set in step S141.
If the vehicle speed is equal to or lower than the limit vehicle speed, the engine speed N in step S142
And the engine speed limit Nmax are compared, and if the engine speed limit is exceeded, a flag is set in the same manner. Then, under normal traveling conditions that are equal to or lower than the vehicle speed limit and equal to or lower than the engine speed limit, the value of the diagnosis condition determination flag F3 is referred to in step S143,
The throttle opening is referred to in step S144. Therefore, when the throttle is opened, the routine proceeds to step S145, where the fuel cut flag Ffc is cleared, when decelerating with the throttle fully closed, the engine speed N is referred to in step S146, and when it is greater than the recovery speed Nre, a flag is set.
The flag is cleared when the number of revolutions is equal to or lower than Nre.

Further, in the pre-rotation mode of F3 = 1 or the twin turbo mode, steps S143 to S143 are executed.
Proceeding to 147, first, the value of the second diagnosis result flag Fng2 is referred to. If Fng2 = 1 and a failure occurs in the twin turbo mode, the process proceeds to step S141 and the flag is set. If normal under twin turbo mode (Fng2 = 0), the process proceeds from step S147 to step S148 to refer to the value of the third diagnosis result flag Fng3, and if a failure occurs in the preliminary rotation mode of Fng3 = 1, Similarly, the process proceeds to step S141, the flag is set, and if normal in the preliminary rotation mode (Fng3 = 0), the process proceeds to step S144. The fuel cut flag Ffc
Is referred to in the fuel injection amount setting routine of FIG.
When c = 1, fuel cut is executed.

The fuel injection amount setting routine of FIG. 14 is executed every predetermined time. First, at step S150, the intake air amount Q
The basic injection amount Tp is calculated from the engine rotation speed N and (T
p ← K × Q / N, K is an injector characteristic correction constant), and various increase correction coefficients COEF, air-fuel ratio feedback correction coefficient α, and voltage correction coefficient Ts are set in step S151. After that, the routine proceeds to step S152, refers to the value of the fuel cut flag Ffc, and if Ffc = 0, step S1
At 53, the fuel cut coefficient Kfc is set to 1.0, and then the process proceeds to step S154 to calculate the fuel injection amount Ti.
Then, in step S155, the fuel injection amount Ti is set, and thus the predetermined fuel is injected.

When the fuel cut flag Ffc is set (Ffc = 0), steps S152 to S152 are executed.
In step 156, the fuel cut coefficient Kfc is set to 0, and the fuel injection amount Ti is calculated in step S154. Therefore, in this case, Ti = Ts is set and the fuel is cut off. In this way, if any valve is stuck in the pre-rotation mode or the twin turbo mode and fails, the fuel output is reduced so that the engine output is reduced. Is
It will be forced to operate in the single turbo mode range only.

Although the embodiments of the present invention have been described above, the present invention can be similarly applied to engines other than the horizontally opposed engine and those having a different valve configuration on the secondary turbocharger side.

[0066]

As described above, according to the present invention, since the exhaust control valve, the intake control valve, and the boost pressure relief valve on the secondary turbocharger side are collectively diagnosed in the sequential turbo engine, the failure diagnosis is performed individually. Since it is not necessary to provide a failure detecting means, the structure is simplified and the control is facilitated. When all valves operate normally in each mode,
Since it is a method of diagnosing a failure by the differential pressure on the upstream side and downstream side of the intake control valve when any of the valves fails, the presence or absence of the failure can be accurately diagnosed. Further, since the failure diagnosis is automatically performed every time the mode is switched, the frequency of the diagnosis is increased and the reliability is improved.

In the case of a failure in the single turbo mode, the fail-safe operation is performed so as to switch to the twin turbo mode which operates normally, so that the normal turbo operating state can be secured. Also, in the failure in the pre-rotation mode and the twin turbo mode, the fuel is cut off so that fail-safe is performed, so the engine output is reliably reduced to cause over-rotation of the primary turbocharger, heat damage of the secondary turbocharger, etc. Can be prevented.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an apparatus suitable for carrying out a failure diagnosis method for a sequential turbo engine according to the present invention.

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

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

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

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

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

FIG. 7 is a diagram showing various maps.

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

FIG. 9 is a time chart showing an open / closed state of each valve and a supercharging pressure state in a preliminary rotation mode.

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

FIG. 11 is a flowchart showing a failure diagnosis routine.

FIG. 12 is a flowchart showing a failure diagnosis routine.

FIG. 13 is a flowchart showing a fuel cut determination routine.

FIG. 14 is a flowchart showing a fuel injection amount setting routine.

[Explanation of symbols]

 1 Engine Main Body 40 Primary Turbocharger 50 Secondary Turbocharger 55 Exhaust Control Valve 58 Intake Control Valve 60 Supercharging Pressure Relief Valve 80 Differential Pressure Sensor 100 Control Unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02D 43/00 R

Claims (3)

[Claims] 1. A primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine body, and at least a relief valve, an intake control valve, and an exhaust control valve are provided on the secondary turbocharger side. It is provided and operates only the primary turbocharger in single turbo mode,
In the twin turbo mode, in the sequential turbo engine that controls to operate both the primary turbocharger and the secondary turbocharger, the upstream pressure and the downstream pressure of the intake control valve for each of the single turbo mode, the preliminary rotation mode and the twin turbo mode. A failure diagnosis method for a sequential turbo engine, which is characterized by diagnosing whether or not there is any failure in a relief valve, an intake control valve, or an exhaust control valve based on a pressure difference from the pressure. 2. In the single turbo mode, a failure occurs when the differential pressure is larger than the set value, in the pre-rotation mode a failure occurs when the differential pressure is smaller than the set value, and in the twin turbo mode, the absolute value of the differential pressure is larger than the set value. The method for diagnosing a failure of a sequential turbo engine according to claim 1, wherein the failure is judged when the values are large. 3. The twin turbo mode is forcibly switched in the case of a failure in the single turbo mode, and the fuel cut control is performed in the case of a failure in the preliminary rotation mode and the twin turbo mode. Failure diagnosis method for sequential turbo engine.