JPH0417723A - Abnormality detecting device of exhaust air switching valve of 2 stage supercharged internal combustion engine - Google Patents

Abstract

PURPOSE:To discriminate the abnormality of an exhaust change over valve by calculating the rate of the outlet port air pressure of a compressor of a high pressure stage turbocharger to the outlet port air pressure of a compressor of a low pressure stage turbocharger. CONSTITUTION:A high pressure stage turbocharger 18 and low pressure stage turbocharger 17 are arranged in series in the gas flow direction, and an exhaust change over valve 38 is provided in an exhaust air by-path 36, which makes detour around the high pressure stage turbocharger 18. The exhaust change over valve 38 closes the exhaust air by-path 36 when supercharging pressure is low and opens the exhaust air by-path 36 when supercharging pressure is high. A control circuit 72 distinguishes the abnormality of the work of the exhaust change over valve 38 by comparing the rate of the outlet pressure of a compressor 20 from the first pressure sensor 78 to that of a compressor 26 from the second pressure sensor 80 with the specified value. Thus, abnormality can quickly be discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an abnormality detection device for an exhaust switching valve in a sequential two-stage supercharged internal combustion engine.

[Prior art]

A sequential two-stage supercharging system is disclosed, for example, in Japanese Utility Model Application Laid-open No. 119930/1983, in which two large and small turbochargers are arranged in series.

The two-stage supercharging system is a supercharging system that achieves supercharging over a wide range of engine speeds, from low to high engine speeds. That is, in the low speed range of the engine, supercharging is performed by a high pressure stage turbocharger with a small capacity, and in the high speed range of the engine, supercharging is performed by a low pressure stage turbocharger with a large capacity. The high-pressure turbocharger is provided with a bypass, and the bypass is closed in the low-speed range, allowing the high-pressure turbocharger to exert its supercharging effect, and the bypass is opened in the high-speed range when the low-pressure turbocharger is fully activated. , only the low-pressure turbocharger provides supercharging. A pressure detector is installed to detect an abnormal increase in supercharging pressure caused by a stuck exhaust switching valve, etc. The pressure between the compressor of the large-capacity turbocharger on the upstream side of the intake pipe and the high-pressure stage turbocharger on the downstream side is installed. In response to this, when the pressure exceeds a predetermined value, it is determined that there is an abnormality and a mechanism is installed to release the pressure.

[Problem to be solved by the invention]

In conventional technology, a pressure detector is installed between the compressor of the upstream low-pressure turbocharger and the downstream high-pressure turbocharger in order to detect abnormalities in the supercharging system such as an exhaust switching valve sticking. It is determined that an abnormality has occurred when the pressure detected by the pressure detector is higher than a predetermined value. However, with this conventional abnormality detection method, it cannot be determined that there is an abnormality unless the boost pressure exceeds a predetermined value.
This method has the disadvantage that abnormality determination is delayed.

In this invention, an abnormality is determined by knowing the ratio of the outlet pressures of each compressor in a region where large and small turbochargers are operating.

[Means to solve the problem]

According to this invention, in FIG. 1, a high-pressure turbocharger A and a low-pressure turbocharger B are arranged in series in the gas flow direction, and an exhaust switching valve is provided in a bypass passage C that bypasses the high-pressure turbocharger A. In a two-stage supercharged internal combustion engine, the exhaust switching valve closes the bypass passage C when the boost pressure is low and opens the bypass passage C when the boost pressure increases. A first detection means E detects the compressor outlet pressure of the high-pressure turbocharger A, a second detection means F detects the compressor outlet pressure of the high-pressure turbocharger A, and the ratio of the compressor outlet pressure of the low-pressure turbocharger to the compressor outlet pressure of the high-pressure turbocharger and a means G for determining an abnormality in the operation of the exhaust switching valve by comparing the value with a predetermined value.

[For production]

The first detection means E detects the compressor outlet pressure P of the low pressure turbocharger, and the second detection means F detects the compressor outlet pressure P2 of the high pressure turbocharger.

The exhaust switching valve closes the bypass passage C when the boost pressure is low, and opens the bypass passage C when the boost pressure increases.

The abnormality determination means G calculates the ratio between the pressure P and the pressure P2,
An abnormality in the exhaust switching valve is determined based on the value of the ratio.

〔Example〕

FIG. 2 shows an embodiment of the present invention in a fuel injection internal combustion engine using gasoline as fuel, and 10 is an engine body, to which an intake pipe 12 and an exhaust pipe 14 are connected. The intake pipe 12 has a fuel injector 15 and a throttle valve 16. A large-sized low-pressure turbocharger 17 and a small-sized high-pressure turbocharger 18 are arranged in series. The low-pressure turbocharger 17 includes a compressor 20, a turbine 22, and a rotating shaft 24. The high-pressure turbocharger 18 includes a compressor 26, a turbine 28, and a rotating shaft 25. The compressor 20 of the low-pressure turbocharger 17 and the compressor 26 of the high-pressure turbocharger 18 are arranged in this order in the intake air flow direction in the intake pipe 12, and the intercooler 2 is disposed downstream of the compressor 20 of the low-pressure turbocharger 17 and the compressor 26 of the high-pressure turbocharger 18.
9 is arranged, and a throttle valve 16 is arranged downstream of the intercooler 29. In the exhaust pipe, the turbine 28 of the high-pressure turbocharger 18 and the turbine 22 of the low-pressure turbocharger 17 are arranged in this order in the exhaust gas flow direction.

A first exhaust bypass passage 30 is connected to the exhaust pipe bypassing the turbine 22 of the low-pressure turbocharger 17.
A swing door type wastegate valve 32 is disposed in the exhaust bypass passage 30 of the exhaust gas bypass passage 30 . Waste gate valve 3
2 is connected to a diaphragm actuator 34, and its diaphragm 34a is connected to the bypass valve 32. Although the bypass valve 32 is normally biased to close by the spring 34b, the boost pressure applied to the diaphragm 34a causes the wastegate valve 32 to open against the spring 34b.

A second exhaust bypass passage 36 is provided bypassing the turbine 28 of the high-pressure turbocharger 18, and an exhaust switching valve 38 as a butterfly valve is provided in the second bypass passage 36. The exhaust switching valve 38 is connected to its actuator 40, and the actuator 40 is configured as a two-stage diaphragm mechanism. As described later, this actuator 40 closes the exhaust switching valve 38 until the low-pressure turbocharger 17 exerts its full supercharging capacity, and when the low-pressure turbocharger 17 reaches its full supercharging capacity, exhausts the exhaust gas. It has the characteristic of rapidly opening the switching valve 38. The actuator 40 includes diaphragms 40a, 40b and a spring 40C140d, with one diaphragm 40a
is connected to the exhaust switching valve 38 via a rod 40e, and another diaphragm 40b is connected to a rod 40f.

The exhaust switching valve 38 determines whether supercharging pressure is applied to the diaphragm 40a or supercharging pressure is applied to the diaphragm 40b.
A step-like opening characteristic is obtained. That is, when supercharging pressure is applied to the diaphragm 40b, the spring 40c
The exhaust switching valve 3 resists the force of the spring 40d and the resultant force.
8, the valve is opened slowly. When supercharging pressure acts on the diaphragm 40a, the spring 40c
Since the exhaust switching valve 38 is opened only against the force of
The valve opening operation becomes quick.

The exhaust switching valve 38 is further connected to a solenoid 41 for forced full opening. The solenoid 41 is normally demagnetized and does not affect the operation of the exhaust switching valve 40 in this state. However, in the event of an abnormality, which will be described later, the solenoid 41 is energized and the exhaust switching valve 38 is forcibly opened.

An intake bypass passage 44 that bypasses the compressor 26 of the high-pressure turbocharger 18 is provided, and an intake bypass valve 46 is disposed in the intake bypass passage 44. The switching valve 46 is connected to a diaphragm actuator 48, and the operation of the intake bypass valve 46 is controlled by the pressure applied to the diaphragm 48a. This intake bypass valve 46 closes the intake bypass passage 44 in the operating range of the high pressure turbocharger 18 when the low pressure turbocharger 17 has not finished rising, but after the startup is completed, the supercharging pressure acts on the diaphragm 48a from below. Then, the intake bypass valve 46 is opened.

In this embodiment, the internal combustion engine is provided with an exhaust gas recirculation (EGR) device, the EGR device comprising an exhaust gas recirculation passage (EGR).
R passage) 50, and an exhaust gas recirculation control valve (EGR valve) 52 on the EGR passage 50.The EGR valve 52 is provided with a diaphragm 52a, and opens and closes depending on the pressure applied to the diaphragm 52a. controlled.

A three-way solenoid valve (VSVI) 54 is provided for pressure control to the actuator 34 of the wastegate valve 32;
This solenoid valve 54 is switched between a position where atmospheric pressure is introduced into the diaphragm 34a and a position where supercharging pressure is introduced at a position 56 downstream of the high-pressure turbocharger 26 and upstream of the intercooler 29. When atmospheric pressure is introduced, wastegate valve 32 is driven to close by spring 34a, and when supercharging pressure is introduced, wastegate valve 32 is opened against spring 34b.

A three-way solenoid valve (VSV2) 58 is provided to control the pressure of the tire flamm 40a of the actuator 40 of the exhaust switching valve 38. It changes depending on the position where the boost pressure is introduced.

Moreover, the pressure at the high-pressure stage turbocharger outlet 60 is constantly introduced into the diaphragm 40b.

Two three-way solenoid valves 64, 66 are provided for pressure control to the actuator 48 of the intake bypass valve 47.

A three-way solenoid valve (VSV3) 64 is provided above the diaphragm 48a of the actuator 48 of the intake bypass valve 46 for pressure control.
The position is switched between a position where atmospheric pressure is introduced above 8a and a position where supercharging pressure from the outlet 60 of the high-pressure turbocharger 18 is introduced. In addition, a three-way solenoid valve (VSV4) 66 is the diaphragm 4 of the actuator 48 of the intake bypass valve 46.
This solenoid valve 6 is provided for pressure control to the lower side of 8a.
6 is the diaphragm 48. The lower side of the throttle valve 16 is switched between a position where negative pressure is introduced at a position 68 downstream of the throttle valve 16 and a position where supercharging pressure at the outlet 60 of the high-pressure stage turbocharger 26 is introduced.

Three-way solenoid valve (VSV5) 70 is provided to control the operation of the EGR valve 52, and this solenoid valve 70 is connected to the diaphragm 52.
The position is switched between a position where atmospheric pressure is introduced to a and a position 68 downstream of the throttle valve 16 where negative pressure is introduced.

The control circuit 72 is provided for supercharging control, fuel injection, and ignition timing control in the present invention, and is provided for controlling each electromagnetic valve 54 (V
SVI), 58 (VSV2), 84 (VSV3),
66 (VSV4).

70 (VSV5), the fuel injector 15, the igniter 74, and the distributor 76 via respective drive signal lines. Further, the control circuit 72 is connected to various sensors in order to execute control according to the present invention. First, the first pressure sensor 7 is used to detect the outlet pressure P1 of the compressor 20 of the low-pressure turbocharger 17.
8 is provided, and a second pressure sensor 80 is provided to detect the outlet pressure P2 of the compressor 26 of the high-pressure turbocharger 18.

An air-fuel ratio sensor 82 is provided downstream of the turbine 22 of the low-pressure turbocharger 17 . In addition, although not shown, an air flow meter is provided to measure the intake air amount Q, and for timing control, the crank angle is 30', 7.
A pulse signal every 20' is output.

The operation of the control circuit 72 will be explained below using a flowchart. FIG. 3 shows a boost pressure control routine, and this routine can be executed within the main routine. In step 100, it is determined whether the ratio of the compressor outlet pressure P2 of the high pressure turbocharger 18 to the compressor outlet pressure P of the low pressure turbocharger 17 is greater than a predetermined value. This is abnormality determination using the stick of the exhaust switching valve 38, and will be described later. As long as the exhaust switching valve is normal, the process proceeds to step 102, where it is determined whether the compressor outlet pressure P2 of the high pressure turbocharger 18 is greater than the compressor outlet pressure P of the low pressure turbocharger 17. Figure 8 shows the engine speed NE and supercharging pressure (
(turbocharger outlet pressure), and the rise of the high-pressure stage turbocharger outlet pressure P2 is faster than the rise of the low-pressure stage turbocharger outlet pressure P.

Therefore, in a state where the engine speed has not yet increased, P2>PI holds true, and in steps 103 and 104, the flag FEGR is set to permit exhaust gas recirculation operation, and in step 106, the air-fuel ratio is controlled normally. Therefore, flag FA is set, and in step 108, flag FI is set to control the ignition timing normally. From step 110 onwards, each solenoid valve 54 (VSVI') 58 (VSV2), 64 (
VSV3), 66 (VSV4) operation is shown. Step 110: When the solenoid valve 54 (VSVI) is turned off, atmospheric pressure is introduced into the diaphragm 34a, and the wastegate valve 32 is closed by the spring 34b.

On the other hand, regarding the operation of the exhaust switching valve 38, when the solenoid valve 58 (VSV2) is turned off in step 112, atmospheric pressure is introduced into the diaphragm 40a, while the compressor outlet pressure of the high-pressure stage turbocharger 18 is introduced into the diaphragm 40b. Since the springs 40c and 4 are introduced,
The operation of the exhaust switching valve is controlled by the compressor outlet pressure of the high-pressure turbocharger 18 that opposes the spring force corresponding to the resultant force of 0d. That is, as long as the spring force is dominant over the supercharging pressure P2, the exhaust switching valve 38 remains fully closed, but the rotational speed at which the supercharging pressure P2 reaches the predetermined value PSET (NE in FIG. 8, ), the exhaust switching valve 38 remains fully closed, and when P2=predetermined value PSeT is reached, the exhaust switching valve 38 gradually begins to open against the closing biasing force that is the resultant force of the spring 40c and the threshold 40d. do.

On the other hand, when the engine speed is low, the solenoid valve 64 is activated in step 114.
(VSV3) is turned on and the compressor outlet pressure P2 of the turbocharger 18 acts on the upper side of the diaphragm 48a, so the intake bypass valve 46 is closed.

Furthermore, in step 116, the solenoid valve 66 (VSV4) is turned off, so the intake pipe pressure downstream of the throttle valve 16 (negative pressure at this time) acts on the lower side of the diaphragm 48a, so the diaphragm 48a moves downward. being pulled,
The closing force of the intake bypass valve 46 is increased to ensure its reliable closing.

When the engine speed NE increases to NE, the rise in the compressor outlet pressure P of the low-pressure turbocharger 17 catches up with the compressor outlet pressure P2 of the high-pressure turbocharger 18, and P2=P, step 102
The process proceeds to step 120, and since it is still normal, the solenoid 41 is turned off, and the process proceeds to step 122.12.
4, 126 are steps 104 and 106.

108, and normal control of EGR, air-fuel ratio, and ignition timing is continued. In step 128, the solenoid valve 54 (VS
VI) is turned on, the diaphragm 34a moves to the position 56.
The supercharging pressure is introduced, and the wastegate valve 32 is urged in the opening direction against the spring 34b.

When the solenoid valve 58 (VSV2) is turned ON in step 112, the supercharging pressure from the position 60 is introduced into the diaphragm 40a, so the spring 40d becomes irrelevant to the valve opening force.
The weak force of spring 40c alone opposes the valve opening force applied to diaphragm 40a. Therefore, the exhaust gas switching valve 38 is fully opened all at once.

Step 132 Solenoid valve 64 (VSV3) OFF
i, atmospheric pressure acts on the upper side of the diaphragm 48a, and in step 134, the solenoid valve 66 (VSV4) is turned on, so that the supercharging pressure downstream of the throttle valve 68 is applied to the diaphragm 48a.
8a, the diaphragm 48a is pushed upward and the intake bypass valve 46 is opened.

The above is the control under normal conditions, but the case where the exhaust switching valve 38 is maintained in operation by a stick or the like will be explained below. That is, the exhaust switching valve 38 is a butterfly valve, and its outer peripheral edge tends to stick to the inner peripheral wall surface of the passage 36 due to the influence of heat. still,
Since the wastegate valve 32 is a swing door type, there are few stick problems.

A small clearance is provided between the outer periphery of the exhaust switching valve 38 and the inner periphery of the bypass passage 36 to absorb thermal expansion even when the exhaust switching valve 38 is fully closed. Exhaust gas passes through this portion and contributes to driving the low-pressure turbine 22, albeit to some extent.

When the exhaust switching valve 38 sticks, the area formed by the clearance becomes smaller by the stick, and the amount of exhaust gas passing through the clearance decreases.

Low-pressure stage turbocharger 17 corresponds to the reduction in exhaust gas volume.
The rise in rotation of the turbine 22 is delayed from normal times, and the speed rises as shown by the broken line l in FIG. 8, for example.

On the other hand, in the high pressure stage, the pressure rises quickly as indicated by l'. In this invention, abnormality due to sticking is determined by utilizing the fact that the balance between the amount of exhaust gas to the high-pressure turbocharger and the amount of exhaust gas to the low-pressure turbocharger changes depending on whether it is normal or stuck. In other words, when the stick is applied, the rise of P is slow, so P2/P calculated in step 100
becomes larger than normal. The predetermined value in step 100 is determined according to the values of P and /P obtained during normal operation.

That is, when stick occurs, the original relationship of P2/P, > K no longer holds, and an abnormality can be detected. When it is determined that there is an abnormality, the process proceeds to step 140, and solenoid 4
1 is turned on, and the exhaust switching valve is forcibly opened. In step 142, the EGR control flag FEGR is cleared, and exhaust gas recirculation is stopped as described below. In step 144, the air-fuel ratio control flag FA is cleared, and air-fuel ratio control in the event of an abnormality is performed as described later. Step 146
In this case, the ignition timing control flag Fl is cleared, and ignition timing control in the event of an abnormality is performed as described later. Each solenoid valve 54 (VSVI), 58 (V
SV2>, 64 (VSV3), 66 (VSV4
) is shown in steps 148.150.152.154.

The solenoid valve 54 (VSVI) is turned on and the pressure at position 56 is introduced, and each solenoid valve 58 (VSV2) is turned off. Also, solenoid valve 64 (VSV3) is OFF, solenoid valve 6
6 (VSV4) ON sat'L, the intake bypass valve 46 is opened when the supercharging pressure is activated.

FIG. 4 shows the EGR control routine, and in step 160 it is determined whether the flag FEGR is set. When the exhaust switching valve 40 is operating normally, FEGR=1,
Proceeding to step 162, the engine speed NE is set to a predetermined value N.
In step 164, it is determined whether the engine load L (e.g. intake air amount - engine rotation speed ratio) is greater than E.
is a predetermined value, and it is determined whether or not it is larger than a predetermined value. NE≦NE
, and when the condition L≦L1 is satisfied, the exhaust gas recirculation is performed at low engine speed and low load.The process proceeds to step 166, and the amount of exhaust gas recirculation at that engine speed and load is calculated. When the conditions of NE>NE+ or L>L are satisfied at high speeds and high loads, this is a non-exhaust gas recirculation region, and the process proceeds to step 168, where the amount of exhaust gas recirculation is set to zero. In step 170, the EGR signal is
0 (VSV5). In this case, the electric signal applied to the electromagnetic valve 70 becomes a pulse signal having a predetermined duty ratio so that the EGR amount calculated at step 166 and threshold 168 is obtained.

If the exhaust switching valve 38 is abnormal, the FEGR is reset (0
), the process proceeds to step 168 unconditionally, so that the exhaust gas recirculation operation is not performed.

FIG. 5 shows a fuel injection routine, which is executed every fuel injection for that cylinder, for example, every 180' CA in the case of a four-cylinder internal combustion engine. This timing is every 30°CA and 72°
This can be known from the crankshaft timing signal every 0°CA. In step 180, the basic fuel injection amount TP is calculated, and this basic fuel injection amount TP corresponds to the fuel injection amount that makes the air-fuel ratio the stoichiometric air-fuel ratio at the engine speed and load. In step 182, the fuel injection amount TAU is changed to LEAN xa (1+
β) + γ. FAF is an air-fuel ratio feedback coefficient described later, KLEAN is an air-fuel ratio correction coefficient described later, and α, β, and γ are correction coefficients and correction amounts whose explanations are omitted because they are not directly related to this invention. .

In step 184, a fuel injection signal is applied to the injector 15 of the cylinder in which fuel is to be injected.

FIG. 6 shows a calculation routine for the feedback correction coefficient used in FIG. This routine is a time synchronized routine that is executed at regular intervals. In step 200, it is determined whether the air-fuel ratio control flag FA=1. Exhaust switching valve 4
If 0 is normal, FA=1, and the process proceeds to step 202, where the air-fuel ratio correction coefficient KLEAN is calculated. KLEA
N is a coefficient for correcting the basic injection amount TP according to the stoichiometric air-fuel ratio calculated in step 180 to the optimum lean air-fuel ratio or rich air-fuel ratio according to the engine speed and load, and K
The value of LEAN is smaller than 1.0 when the air-fuel ratio is on the lean side, and larger than 1.0 when the air-fuel ratio is on the rich side. In step 204, an output value (target value of the air-fuel ratio) vx is calculated for the air-fuel ratio sensor 82 according to the air-fuel ratio correction coefficient KLEAN calculated in step 202. In step 206, the target value vX of the air-fuel ratio is compared with the actual value vO of the air-fuel ratio measured by the air-fuel ratio sensor 82. When vx>vo, it is determined that the target air-fuel ratio is larger than the actual value of the air-fuel ratio, that is, it is necessary to increase the air-fuel ratio, and the process proceeds to step 208, where the feedback correction coefficient FAF is decreased and the fuel amount is decreased. be done. When vx>vo, it is determined that the target air-fuel ratio is smaller than the actual value of the air-fuel ratio, that is, it is necessary to reduce the air-fuel ratio, and the process proceeds to step 210, where the feedback correction coefficient FAF is increased and the fuel amount is increased. be done. In this way, the air-fuel ratio is controlled to the target value.

If there is an abnormality in the exhaust switching valve 38 such as stick, FA=O in step 144 of FIG.
In step 214, the feedback correction coefficient FAF is set to 1.0, and as a result, the air-fuel ratio becomes the stoichiometric air-fuel ratio.

FIG. 7 shows an ignition timing control routine, and this routine, like fuel injection, is executed once for each cylinder in one engine cycle (that is, every 180° CA in a four-cylinder engine). In step 220, the basic ignition timing τsp is calculated, and in step 220, it is determined whether the ignition timing control flag FI=1. If the exhaust switching valve 38 is normal, FI=
Since it is 1, the process proceeds to step 224, where the ignition timing retardation correction amount Δ is set to 0, and the ignition timing retardation correction due to the abnormality of the exhaust switching valve 38 is not performed. If the exhaust switching valve 38 is abnormal, FI=0, so the process proceeds to step 226, where the ignition timing retardation correction amount is set to Δ, and in step 228, the ignition timing retardation correction amount is set to Δ, and in step 228, the retardation correction amount Δ is subtracted from the basic ignition timing τ. The ignition timing will be retarded from the optimum timing.

Although the above embodiments describe a fuel-injected internal combustion engine that uses gasoline as fuel, a diesel engine can also be implemented. In a diesel engine, the abnormality of the exhaust switching valve 38 is determined according to the invention by the ratio of the compressor outlet pressure P2 of the high pressure turbocharger to the compressor outlet pressure P of the low pressure turbocharger. Moreover, as a measure after detecting an abnormality, instead of setting the air-fuel ratio to the stoichiometric air-fuel ratio, control is performed to reduce the maximum injection amount.

〔effect〕

According to this invention, by determining an abnormality in the exhaust switching valve based on the ratio of the compressor outlet pressure P2 of the high-pressure turbocharger to the compressor outlet pressure P1 of the low-pressure turbocharger, stick occurs before the boost pressure increases. Since the system detects abnormalities, it is possible to determine abnormality more quickly, and the engine can be protected.

Further, by simply using the existing pressure sensor provided in the system, there is no need to provide a detection device for abnormality determination.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the functional configuration of the present invention. FIG. 2 is a diagram showing a schematic configuration of an embodiment of the present invention. 3 to 7 are flowcharts explaining the operation of the apparatus of the present invention. FIG. 8 is a graph schematically explaining the operation of the exhaust switching valve. 10... Engine body, 12... Intake pipe, 14...
- Exhaust pipe, 15...Fuel injector, 16
...Throttle valve, 17..Low pressure stage turbocharger, 18..High pressure stage turbocharger, 29..Intercooler, 30..First exhaust bypass passage, 32..Wastegate valve, 36. ...Second exhaust bypass passage, 38...Exhaust switching valve, 44...Intake bypass passage, 52...EGR valve, 54, 58.64.66, 70...Solenoid valve, 72...
・Control circuit, 74... igniter, 76...
Distributor, 78... first pressure sensor, 80... second pressure sensor. Figure 4 Figure Figure Figure Figure

Claims (1)

[Claims] A high-pressure turbocharger and a low-pressure turbocharger are arranged in series in the gas flow direction, and an exhaust switching valve is provided in a bypass passage that bypasses the high-pressure turbocharger. In a two-stage supercharged internal combustion engine that closes the exhaust switching valve and opens the exhaust switching valve when boost pressure increases, the first detection means detects the compressor outlet pressure of the low-pressure stage turbocharger and the compressor outlet pressure of the high-pressure stage turbocharger. a second detection means for
A two-stage supercharged internal combustion engine, comprising means for determining abnormal operation of an exhaust switching valve by comparing the ratio of compressor outlet pressure of a low-pressure turbocharger to a compressor outlet pressure of a high-pressure turbocharger with a predetermined value. Abnormality detection device for exhaust switching valve.