JP2005220890A - Supercharging system for internal combustion engines - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercharging system for an internal combustion engine capable of specifying a failure mode when an abnormality is detected in the system and capable of taking measures according to the specified failure mode.
A turbocharging system for an internal combustion engine according to the present invention includes a turbocharger 3, an electric compressor 4 provided in an intake pipe 5 upstream or downstream of the turbocharger, and a bypass that bypasses the electric compressor 4. A passage 7, a bypass valve 8 provided in the bypass passage 7, and a supercharging system control means 2 for controlling the electric compressor 4 are provided. Then, an abnormality detecting means 2 for detecting an abnormality of the system operating beyond a permissible range from a normal value indicating a normal operating characteristic of the system, and in which of the assist area and the non-assist area the abnormality of the system is detected. And a failure mode determination means 2 for determining a failure mode in which an abnormality is detected only in the assist region and a failure mode in which an abnormality is detected only in the non-assist region.
[Selection] Figure 1

Description

  The present invention relates to a supercharging system for an internal combustion engine.

As a supercharging system for internal combustion engines, an electric compressor is arranged in series with the turbocharger compressor, and a check valve is provided at the junction between the downstream intake passage of the electric compressor and the upstream intake passage of the turbocharger compressor. A supercharging system configured to selectively switch one of the downstream intake passage and the upstream intake passage with a bubble to switch the route of the intake passage between a route passing through the electric compressor and a route bypassing the electric compressor. Yes (see, for example, Patent Document 1). In addition, Patent Documents 2 to 4 exist as prior art documents related to the present invention.
JP-T-2001-518590 Special Table 2000-500544 Special table 2001-509561 gazette JP 2002-021573 A

  As disclosed in Patent Document 1 above, in this type of supercharging system, in order to switch the path of the intake passage in accordance with the operating state of the electric compressor, it is common to provide a movable member such as a check valve in the intake passage. Is. For this reason, for example, a failure may occur in which the movable member becomes inoperable for some reason. In such a case, it is necessary to identify the failure mode (failure mode) and cope with it. However, the above patent document does not disclose not only a means for detecting a failure in the supercharging system but also a means for specifying a failure mode. Therefore, when a failure occurs, there is a possibility that the supercharging system itself cannot take measures according to the failure mode.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a supercharging system for an internal combustion engine that can specify a failure mode when an abnormality is detected in the system and that can take measures according to the specified failure mode. And

  A first supercharging system for an internal combustion engine according to the present invention includes a turbocharger that supercharges the internal combustion engine using exhaust energy of the internal combustion engine, and an upstream or downstream of a compressor of the turbocharger. An electric compressor provided in the intake passage, a bypass passage bypassing the electric compressor, and provided in the bypass passage, and closes the bypass passage when the electric compressor is in operation, while the electric compressor is inactive A switching valve that can be opened and closed to open the bypass passage, and supercharging that controls the electric compressor so that the electric compressor is in a first state in which the electric compressor is in operation or in a second state in which the electric compressor is inactive A supercharging system for an internal combustion engine comprising system control means, which is set in advance as normal operating characteristics of the system in each state. As an abnormality detection means for detecting an abnormality of a system that operates beyond a permissible range from a normal value that has been set, an assist region that is preset as a condition to be controlled to the first state, and a condition that is to be controlled to the second state A failure mode in which the abnormality is detected only in the assist region and a failure mode in which the abnormality is detected only in the non-assist region by determining in which region of the preset non-assist region the abnormality is detected The above-described problem is solved by including a failure diagnosis unit including a failure mode determination unit that determines whether or not

  There are several types of failure modes of the system that performs supercharging assist by the electric compressor. Among these, failure modes are found during operation of the electric compressor, but return to normal when the electric compressor is deactivated. On the other hand, there is a failure mode in which an abnormality is recognized when the electric compressor is inactive, while a normal mode is restored when the electric compressor is operated. According to the present invention, by determining whether the operation region of the system in which the abnormality is detected is in the assist region where the electric compressor should be operated or in the non-assist region where the electric compressor should be deactivated, A failure mode in which an abnormality appears in only one of the assist region and the non-assist region can be determined from a plurality of failure modes. As a failure mode in which an abnormality is detected only in the non-assist region, for example, there is a first failure mode in which the switching valve is fixed in a fully closed state (claim 2). In this case, an important failure mode in which the bypass passage is blocked can be distinguished from other failure modes.

  In the first supercharging system for an internal combustion engine according to the present invention, the failure mode determination unit may include the failure mode determining unit in the assist region when there are a plurality of failure modes in which the abnormality is detected only in the assist region. In consideration of the rotational speed of the electric compressor, one failure mode may be specified from the plurality of types of failure modes. For example, as a system abnormality in the assist region, the supercharging pressure may not rise above a normal value. According to this aspect, since the rotational speed of the electric compressor is considered in such a case, it is possible to determine whether the failure mode is caused by the electric compressor or a failure mode unrelated to the electric compressor. it can. As a failure mode in which an abnormality appears only in the assist region, there are a second failure mode in which the switching valve is fixed in a fully opened state and a third failure mode in which the electric compressor fails. Therefore, when an abnormality in the system is detected in the assist region, if the rotational speed of the electric compressor does not indicate an abnormality, it can be seen that the second failure mode is that the switching valve is stuck in the fully open state. If the rotation speed of the compressor is abnormal, it is found that the electric compressor is in the third failure mode.

  In the first supercharging system for an internal combustion engine of the present invention, when the abnormality is detected, the failure mode determination means determines the presence or absence of the abnormality in a region other than the region where the abnormality is detected. The failure mode in which the abnormality is detected in both the assist region and the non-assist region, the failure mode in which the abnormality is detected only in the assist region, and the failure in which the abnormality is detected only in the non-assist region It may be distinguished from at least one mode. Among the failure modes, there is a failure mode that shows an abnormality in both the assist region and the non-assist region. According to this aspect, even when the abnormality cannot be determined at the time of detecting the abnormality, by confirming the abnormality in both the assist area and the non-assist area, the abnormality occurs in only one of the failure mode and the assist area or the non-assist area. Can be distinguished from the failure mode in which In addition, such a failure mode includes a fourth failure mode in which an adjustment valve that is provided in the intake passage upstream of the electric compressor and adjusts the amount of air flowing into the intake passage is fixed in a closed state. (Claim 6). Therefore, it is possible to discriminate between the fourth failure mode and the other failure modes by confirming the abnormality in both the assist region and the non-assist region.

  Further, in the first supercharging system for an internal combustion engine of the present invention, in the case where the electric compressor is arranged upstream of the compressor of the turbocharger, as the normal value serving as a criterion for determining abnormality, The pressure in the intake passage between the electric compressor and the compressor of the turbocharger determined according to the intake flow rate flowing into the intake passage may be used. Further, as the normal value, a differential pressure upstream and downstream of the electric compressor determined according to an intake air flow rate flowing into the intake passage may be adopted. Therefore, the system abnormality can be detected by monitoring these values and comparing the normal value with the monitoring result to determine whether or not the comparison result exceeds the allowable range.

  A second supercharging system for an internal combustion engine of the present invention is a supercharging system for an internal combustion engine applied to an internal combustion engine provided with an internal combustion engine control means for controlling the operating state of the internal combustion engine, comprising a compressor, a turbine, A turbocharger that is equipped with a variable nozzle that changes the flow rate of exhaust gas to the turbine and that uses the exhaust energy of the internal combustion engine to supercharge the internal combustion engine, and upstream of the compressor of the turbocharger or An electric compressor provided in a downstream intake passage, a bypass passage that bypasses the electric compressor, and a bypass passage that is provided in the bypass passage and closes the bypass passage when the electric compressor is in operation, while the electric compressor is not A switching valve that can be opened and closed to open the bypass passage in operation, the opening of the variable nozzle, and the operation of the electric compressor. A supercharging system control means for controlling the state; a failure diagnosis means for specifying any of a plurality of preset failure modes when a system abnormality is detected; and a failure mode specified by the failure diagnosis means. Accordingly, there is provided a risk avoidance control unit that changes control for at least one of the opening degree of the variable nozzle, the operating state of the electric compressor, and the operating state of the internal combustion engine, thereby solving the above-described problem. (Claim 9).

  According to the present invention, it is possible to take appropriate measures according to the nature of the failure mode by changing the control for each control target. For example, when the first failure mode in which the switching valve is fixed in a fully closed state is specified by the failure diagnosis means, the opening degree of the variable nozzle is changed to a nozzle fully open control that controls the fully opened state, and You may change to the driving | running | working restriction | limiting control which restrict | limits the driving | running state of an internal combustion engine to less than predetermined output (Claim 10). The first failure mode is a failure mode in which the switching valve is fixed in a fully closed state, and the bypass passage is always closed. For this reason, as the internal combustion engine rotates at a higher speed, the intake resistance by the electric compressor increases and the burden on the internal combustion engine and the turbocharger increases. Therefore, if each control object is controlled in this manner, the back pressure of the internal combustion engine can be reduced and the increase in the rotational speed of the turbocharger can be suppressed, and the internal combustion engine can be prevented from entering a high speed state. be able to. Further, in this aspect, since the control is changed to limit the operation state of the internal combustion engine, the travel is possible but the fully open travel is impossible, and a serious failure of the internal combustion engine and the supercharging system is prevented. Can do.

  In the second internal combustion engine supercharging system of the present invention, when the second failure mode in which the switching valve is fixed in a fully opened state is specified by the failure diagnosis means, the opening of the variable nozzle is closed. It is preferable to change to the nozzle closing side control for controlling to the side state and to the electric compressor operation prohibiting control for prohibiting the operation of the electric compressor (claim 11). In the second failure mode, the intake air flows into the bypass passage, and effective assist cannot be realized even if the electric compressor is operated. Therefore, it is desirable to prohibit the operation of the electric compressor as in this aspect. In this case, the opening of the variable nozzle may be reduced. Thereby, the fall of the supercharging performance by the operation | movement prohibition of an electric compressor can be relieved.

  In the second internal combustion engine supercharging system of the present invention, the electric compressor is provided in the intake passage upstream of the compressor of the turbocharger, and the inflow amount of air is adjusted in the intake passage upstream of the electric compressor. In the aspect provided with the adjustment valve to perform, the danger avoidance control unit may further change to adjustment valve full open control for controlling the opening degree of the adjustment valve to a full open state. In this case, since the amount of intake air increases, the intake resistance due to the electric compressor can be reduced.

  Further, in the second supercharging system for an internal combustion engine of the present invention, the danger avoidance control unit is configured to detect the variable nozzle when the third failure mode in which the electric compressor fails is specified by the failure diagnosis unit. Preferably, the opening degree is changed to the closing side control for controlling the opening side state, and the electric compressor operation prohibiting control is prohibited to prohibit the operation of the electric compressor. In this case, since the electric compressor has failed, the electric compressor is not operated. However, the performance deteriorated by the non-operation of the electric compressor is dealt with by reducing the opening of the variable nozzle. Thereby, the fall of the supercharging performance by the operation | movement prohibition of an electric compressor can be relieved.

  In the second internal combustion engine supercharging system of the present invention, the electric compressor is provided in the intake passage upstream of the compressor of the turbocharger, and the inflow amount of air is adjusted in the intake passage upstream of the electric compressor. When the fourth failure mode in which the regulating valve is fixed in the closed state is specified in the aspect including the regulating valve to be changed, the control is changed to the feedback inhibition control for inhibiting the feedback control of the opening degree of the variable nozzle. (Claim 14). In the fourth failure mode, the amount of intake air is insufficient because the adjustment valve for adjusting the amount of intake air is fixed in the closed state. For this reason, if the feedback control of the variable nozzle with the supercharging pressure as the target value is continued, the actual supercharging pressure does not rise in one direction, and there is a risk of a vicious circle in which the opening of the variable nozzle is further narrowed down. Therefore, according to this aspect, since the feedback control for the variable nozzle is prohibited when the fourth failure mode is specified, such a vicious circle can be broken.

  In the second supercharging system for an internal combustion engine according to the present invention, the nozzle closing side control is set in advance as a region where the electric compressor is operated to assist supercharging of the turbocharger to the internal combustion engine. May be performed only in the assist region that has been set (claim 15). In this case, since the opening of the variable nozzle is limited to the assist region, the acceleration performance at a low speed, which is reduced by the operation prohibition control of the electric compressor, can be efficiently compensated.

  As described above, according to the present invention, a supercharging system for an internal combustion engine that can specify a failure mode when an abnormality is detected in the system and can take measures according to the specified failure mode by itself. Can be provided.

(First embodiment)
A supercharging system for an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the overall configuration of the present embodiment. This supercharging system is applied to a diesel engine (hereinafter also referred to as an engine) 1 as an internal combustion engine. The engine 1 is controlled by an engine control unit (ECU) 2 as internal combustion engine control means. ECU2 is comprised as a computer unit provided with peripheral devices, such as a microprocessor, ROM, and RAM. The ECU 2 controls the operating state of the engine 1 based on input information of various sensors according to a predetermined program stored in a ROM or the like.

  The supercharging system includes a turbocharger 3 that supercharges the engine 1 and an electric compressor 4 (hereinafter sometimes referred to as MC). As is well known, the turbocharger 3 has a compressor 3a for compressing the sucked air and a turbine 3b for driving the compressor 3a. The compressor 3a is provided in the intake pipe 5 as an intake passage. The turbine 3b is provided in the exhaust pipe 6. A variable nozzle 3c is provided in the housing of the turbine 3b for making the flow rate characteristic of the turbine 3b variable. The variable nozzle 3c is composed of a plurality of movable vanes (not shown), and the opening degree (opening area) of the variable nozzle is changed by changing the inclination of these movable vanes. By setting the opening of the variable nozzle 3c to the closed side (squeezing) in the low rotation range of the engine 1, the supercharging pressure can be increased and the low speed torque can be improved. And in the high rotation area of the engine 1, the back pressure of the engine 1 can be lowered by opening the opening of the variable nozzle 3c. Such control of the variable nozzle 3c is performed by the ECU 2. The turbocharger 3 rotates the turbine 3b with the exhaust gas flowing through the exhaust pipe 6 to drive the compressor 3a. Thereby, a desired supercharging pressure can be obtained.

  On the other hand, the electric compressor 4 is provided in the intake pipe 5 on the upstream side of the turbocharger 3. The electric compressor 4 includes an electric motor 4a as a driving device. The electric motor 4a is connected to a power source (not shown). By driving the electric motor 4a, the electric compressor 4 operates, and the air in the intake pipe 5 can be compressed.

  A desired supercharging pressure can be obtained by operating the turbocharger 3 and the electric compressor 4. Since the turbocharger 3 uses the energy of the exhaust gas as described above, a time lag occurs until a desired supercharging pressure is obtained (so-called turbo lag). This is particularly noticeable when rapid acceleration is required during low-speed traveling. Therefore, supercharging assistance is performed by the electric compressor 4 to compensate for the turbo lag and assist the turbocharger until a desired supercharging pressure is obtained.

  Further, in the supercharging system, a bypass passage 7 that bypasses the electric compressor 4 is provided. In the middle of the bypass passage 7, a bypass valve 8 is provided as a switching valve for switching between inflow of air into the bypass passage 7 and prohibition thereof. The bypass valve 8 is basically fully closed when the electric compressor 4 is in operation, and the inflow of air into the bypass passage 7 is prohibited. Therefore, substantially all the air upstream of the electric compressor 4 is guided to the electric compressor 4. On the other hand, when the electric compressor 4 is not in operation, the air compressor 4 is basically fully opened and air is guided to the bypass passage 7. The bypass valve 8 may be linearly driven by a solenoid or the like, but only needs to be able to switch between opening and closing. Further, as the bypass valve 8, a shutter valve that is driven by a balance between the pressure downstream of the electric compressor 4 and the pressure of the inlet of the bypass passage 7 may be employed. In this case, since the control of the bypass valve 8 becomes unnecessary, the structure can be simplified.

  As shown in FIG. 1, an intercooler 9 is provided in the intake pipe 5 on the downstream side of the compressor 3a of the turbocharger 3 in order to cool the air compressed by the compressor 3a. Thereby, the supercharging efficiency can be increased. Further, an intercooler 10 is provided in the intake pipe 5 between the electric compressor 4 and the compressor 3a of the turbocharger 3 for the same reason as described above. By providing this intercooler 10, it is possible to further improve the supercharging efficiency, but it is not always necessary to provide it. In addition, an air cleaner 11 is provided in the intake pipe 5 on the upstream side of the electric compressor 4 to remove foreign substances in the intake air.

  The electric motor 4a generates heat and is preferably cooled. In this case, it is difficult to cool by air cooling, and the operation time of the electric compressor 4 may be limited. Therefore, for example, a cooling system in which cooling water is circulated by a radiator (not shown) around the electric motor 4a may be employed. This radiator may also be used as the one used for the engine 1, but it is more preferable to prepare the cooling water for the electric compressor 4 separately because the cooling water of the engine 1 has a high temperature. In this case, the temperature of the cooling water is preferably about 30 ° C. Furthermore, this radiator can also be used for cooling the turbocharger 3. Such a configuration is very effective as a countermeasure against coking, which is a serious problem.

  As shown in FIG. 1, the engine 1 according to this embodiment may be provided with an introduction pipe 12 for introducing at least one of a part of exhaust gas and blow-by gas. The reason why the connecting portion 12a on the outlet side of the introduction pipe 12 is set to the position shown in FIG. 1 is that it tends to be a negative pressure more easily than other places of the intake pipe 5 and is suitable for introduction of exhaust gas or blow-by gas. . A part of the exhaust gas may be introduced by a known exhaust gas recirculation device (EGR device). When the introduction pipe 12 is used for exhaust gas recirculation, the introduction pipe 12 functions as an EGR pipe connecting the intake pipe 5 and the exhaust pipe 6. Thereby, since the maximum combustion temperature in a cylinder can be suppressed, the discharge | emission amount of NOx (nitrogen oxide) can be reduced. The introduction of blow-by gas may be performed by a known blow-by gas reduction device (PCV device). When the introduction pipe 12 is used for introducing blow-by gas, the introduction pipe 12 functions as a PCV pipe that connects a crankcase (not shown) and the intake pipe 5. Thereby, blow-by gas in a crankcase (not shown) can be reduced, and discharge of blow-by gas can be prevented.

  Further, a throttle valve 13 as an adjustment valve is provided in the intake pipe 5 on the upstream side of the connecting portion 13a. The throttle valve 13 can adjust the amount of air guided to the intake pipe 5 and can also be used to adjust the exhaust gas recirculation rate (EGR rate) or the concentration of blow-by gas. Therefore, the throttle valve 13 is driven by a solenoid or the like so that the opening degree can be changed linearly.

  The supercharging system of the present embodiment configured as described above is controlled by the ECU 2 that controls the operating state of the engine 1. The ECU 2 determines the opening degree of the variable nozzle 3 c of the turbocharger 3, the operating state of the electric compressor 4, the opening degree of the bypass valve 8, and the opening degree of the throttle valve 13 based on input information of various sensors shown below. It functions as a supercharging system control means for controlling each. However, when the above-described shutter valve is employed as the bypass valve 8, control on the bypass valve 8 is not necessary.

  As shown in FIG. 1, the supercharging system according to the present embodiment includes an accelerator opening sensor 20 that detects an accelerator opening and a change amount thereof, an engine speed sensor 21 that detects an engine speed, and an engine 1. A supercharging pressure sensor 22 for detecting the pressure (supercharging pressure) in the intake pipe 5, and provided in the intake pipe 5 between the electric compressor 4 and the compressor 3 a of the turbocharger 3. And a pressure sensor 23 for detecting the pressure in the intake pipe 5 and an air flow meter 24 for detecting the intake flow rate flowing into the intake pipe 5. These various sensors are appropriately used according to the control modes described below. These various sensors may be sensors that detect the physical quantity itself that is a detection target, or may estimate the physical quantity.

  FIG. 2 is a flowchart showing an outline of a control routine of the supercharging system according to the present embodiment. This control routine is repeatedly executed at predetermined intervals according to a program stored in the ROM or the like of the ECU 2. As shown in FIG. 2, the ECU 2 first controls the opening degree of the variable nozzle 3c described above in step S1. In this control, the opening degree of the variable nozzle 3c is feedback-controlled based on the actual supercharging pressure and the target supercharging pressure set corresponding to the required load so as to eliminate the deviation between the two. By executing this control, the nozzle opening can be made appropriate according to the operating state of the engine 1. The target boost pressure is stored in the ROM of the ECU 2 as a map, for example, by referring to the relationship between the required load determined based on the engine speed and the fuel injection amount and the optimum boost pressure. Set by. The engine speed is acquired from the speed sensor 21, and the fuel injection amount may be estimated from the output value of the accelerator opening sensor 20 (see FIG. 1).

  Next, the ECU 2 determines whether or not the electric compressor 4 is in a non-actuated (OFF) state in step S2. When an affirmative determination is made in step S2 that the electric compressor 4 is in a non-operating state, the ECU 2 proceeds to a process in step S3 and determines whether or not the operating condition of the electric compressor 4 is satisfied. This operating condition is a criterion for determining the necessity of supercharging assistance by the electric compressor 4, and is set in advance in consideration of the operating state of the engine 1 as a condition (assist region) where supercharging assistance by the electric compressor 4 is necessary. ing. For example, the engine speed is less than a predetermined speed, the intake flow rate is less than a predetermined amount, the accelerator opening exceeds a predetermined opening, or the difference between the target boost pressure and the actual boost pressure, etc. May be used as a determination factor. In this embodiment, when the engine speed Ne, the intake air flow rate Ga, the accelerator opening degree accpf, and the supercharging pressure deviation Δp (target supercharging pressure pimtrg−actual supercharging pressure pim) satisfy the following conditions: The operating conditions are met. That is, Ne <2400 rpm, Ga <100 g / s, accpf> 50%, Δp> 10 kPa. These various amounts may be acquired from the rotation speed sensor 21, the air flow meter 24, the accelerator opening sensor 20, and the supercharging pressure sensor 22 shown in FIG.

  If it is determined in step S3 that the operating condition of the electric compressor 4 is not satisfied, the current routine is terminated. On the other hand, if it is determined that this operating condition is satisfied, the ECU 2 applies the voltage to the electric motor 4a (see FIG. 1) in step S4 to operate the electric compressor 4 (electric compressor operation control). . Then, the bypass valve 8 shown in FIG. 1 is closed to prohibit the inflow of air into the bypass passage 7 (switching valve closing control). When the above-described shutter valve is used as the bypass valve 8, the pressure in the intake pipe 5 downstream of the electric compressor 4 is increased, so that the bypass valve 8 is closed and no control is required. This state of the supercharging system is the first state. Further, the throttle valve 16 described above is fully opened to increase the intake flow rate (throttle valve opening control), and the current routine is terminated. Thereby, the supercharging assistance of the electric compressor 4 is implement | achieved. Further, when the electric compressor 4 is operated in step S4, the bypass valve 8 is closed, so that intake air can be prevented from flowing back through the bypass passage 6.

  On the other hand, if a negative determination is made in step S2 that the electric compressor 4 is in the operating state, the ECU 2 advances the process to step S5. In step S5, it is determined whether or not the non-operation condition of the electric compressor 4 is satisfied. The non-operation condition is determined in advance as a region (non-assist region) where the supercharging assistance by the electric compressor 4 is not necessary. In this case, the non-operating condition may be established by negating any of the determination elements of the operating condition in step S3, or the turbocharger 3 may be over-rotated from the viewpoint of safety. It may be possible to determine whether or not the non-operating condition is successful based on whether or not the excessive assist is performed or whether the electric compressor 4 may choke and whether or not this criterion is satisfied.

  If the non-operation condition is not satisfied in step S5, the current routine is terminated and the supercharging assist is continued. On the other hand, when this non-operation condition is satisfied, the ECU 2 advances the process to step S6, stops the supply of electric power to the electric motor 4a, and deactivates the electric compressor 4 (electric compressor non-operation control). ). Then, the bypass valve 8 shown in FIG. 1 is opened, and control is performed so that air flows into the bypass passage 7 (switching valve opening control). When the above-described shutter valve is used as the bypass valve 8, the pressure in the intake pipe 5 downstream of the electric compressor 4 is low as opposed to the above-described operation control. is there. This state of the supercharging system is the second state. When the electric compressor 4 is deactivated, the intake air can be guided to the bypass passage 7 by bypassing the electric compressor 4, so that the electric compressor 4 can be prevented from becoming an intake resistance. The throttle valve 16 is subjected to normal control according to the operating state of the engine 1 (event control).

Next, failure diagnosis and failure countermeasures according to the present embodiment will be described. In the supercharging system according to the present embodiment, the normal operating characteristics of the first state and the second state described above are stored as normal values in advance in the ROM of the ECU 2 as a map, and this map and the operating characteristics during system operation are stored. By comparing with the above, an abnormality (failure) in the system is discovered and the failure mode is specified. In the present embodiment, as the operating characteristics of the supercharging system employs a pressure P _i in the intake pipe 5 for the intake flow rate Ga as operating characteristics. This pressure _Pi is the pressure in the intake pipe 5 between the compressor 3a of the turbocharger 3 and the electric compressor 4 (see FIG. 1).

FIG. 3 is an example of a map showing the operating characteristics under normal conditions. The pressure P _i relative to the intake flow rate Ga shown by the solid line in this figure corresponds to the normal value. A region A on the left side of the figure corresponds to the supercharging assist region, and the normal value of the first state when the electric compressor 4 is operating (MC-ON) and the bypass valve 8 is fully closed (bypass valve-close) is Indicated. On the other hand, the right region B corresponds to the non-assist region, and shows the normal value of the second state when the electric compressor 4 is not operating (MC-OFF) and the bypass valve 8 is fully open (bypass valve-open). It is. Accordingly, an allowable range is appropriately determined for the normal value, and when a value exceeding the allowable range is indicated, it is possible to detect that some failure has occurred in the system.

  Since the present supercharging system operates by switching between the first state and the second state, the following failure mode may occur. The first is a first failure mode in which the bypass valve 8 is fixed in a fully closed state, the second is a second failure mode in which the bypass valve 8 is fixed in a fully opened state, a third is a third failure mode in which the electric compressor 4 is failed, and The fourth is a fourth failure mode in which the throttle valve 13 is fixed in the closed state.

The first failure mode is a failure mode in which the bypass valve 8 is not opened when the bypass valve 8 is to be fully opened, that is, in the non-assist region (region B). Accordingly, no abnormality appears in the assist region (region A) where the bypass valve 8 should be fully closed, and only in the non-assist region (region B). In this failure mode, the intake air cannot bypass the non-operating electric compressor 4, and the electric compressor 4 becomes an intake resistance. Therefore, as shown in FIG. 4, the pressure P _i only in the region B abnormality appears to decrease significantly with increasing intake air flow rate Ga.

On the contrary, the second failure mode is a failure mode in which the bypass valve 8 is not closed when the bypass valve 8 should be fully closed, that is, in the assist region (region A). Accordingly, no abnormality appears in the non-assist region (region B) where the bypass valve 8 should be fully opened. This is a failure mode that appears only in region A. In this failure mode, since the intake air despite operating the electric compressor 4, as shown in FIG. 5 will be flowing into the bypass passage 7, the abnormality appears to pressure P _i hardly rise. Also, Similarly, in the third failure mode where the electric compressor 4 has failed, the abnormality appears not only rise the pressure P _i region A as shown in FIG.

Further, in the fourth failure mode, the throttle valve 13 is stuck in the closed state, so that the intake air is insufficient. Therefore, as shown in FIG. 6, in the assist region (region A), the pressure _Pi is lower than the normal value, and in the non-assist region (region B), the pressure of the compressor 3a of the turbocharger 3 is lower than the normal value. also pressure P _i is an abnormality appears to be significantly reduced.

In order to perform failure diagnosis of the supercharging system including identification of these failure modes, the supercharging system of the present embodiment executes the failure detection diagnosis control routine shown in FIGS. This is executed in parallel with the control routine of FIG. 2, and is repeatedly executed at predetermined intervals according to a program stored in the ROM or the like of the ECU 2. This routine is executed by the ECU 2, whereby the ECU 2 functions as failure diagnosis means. As shown in FIGS. 7 and 8, ECU 2 in step S11, the difference between the actual pressure P _i and the target value P _Itrg determines whether exceeds a predetermined value. This target value P _itrg is specified according to the current intake flow rate Ga by acquiring the intake flow rate Ga from the air flow meter 24 (see FIG. 1) and referring to the map shown in FIG. The predetermined value may be appropriately determined as an allowable range in consideration of an error or the like. The predetermined value may be constant or may be changed according to the intake air amount Ga. In the present embodiment, this predetermined value is 10 kPa. By executing step S11, the ECU 2 functions as an abnormality detection unit.

  If an affirmative determination is made in step S11, a system abnormality is detected, so the process proceeds to the next step S12. On the other hand, when a negative determination is made, the present supercharging system is normal, so the subsequent processing is skipped and the current routine is terminated. In step S12, the ECU 2 turns on the check lamp 30 (see FIG. 1). This is performed for the purpose of notifying the driver of the occurrence of an abnormality. Therefore, an alarm device that appeals not only to the driver's vision such as a lamp but also to other five senses may be used.

  Next, in step S13, the ECU 2 determines whether or not the region where the abnormality is detected is a region A. Thereby, a failure mode in which an abnormality occurs in the region A and a failure mode in which an abnormality occurs in the region B can be discriminated. In the present embodiment, the second, third, and fourth failure modes in which a failure occurs in the region A and the first and fourth failure modes in which a failure occurs in the region B can be distinguished. When an affirmative determination is made in step S13, since an abnormality is detected in the region A, it is determined whether the failure mode is the second, third, or fourth failure mode. Therefore, in step S14, failure flags F2, F3, and F4 corresponding to the second, third, and fourth failure modes are set.

  Next, in the subsequent step S15, the ECU 2 determines whether there is an abnormality in the region B other than the region A where the abnormality is detected. Thereby, it is possible to discriminate between a failure mode in which an abnormality occurs in both the region A and the region B and a failure mode in which an abnormality occurs only in the region A. In the present embodiment, it is possible to determine the fourth failure mode in which an abnormality occurs in both the region A and the region B and the second and third failure modes in which an abnormality occurs only in the region A. When an affirmative determination is made in step S15, it is determined whether the failure mode is the second or third failure mode. Therefore, in the subsequent step S16, the ECU 2 clears the failure flag F4 among the failure flags (F2, F3, F4) set in step S14, and advances the process to step S18. On the other hand, when a negative determination is made in step S15 that it is not normal (abnormal), it is determined that the failure mode is the fourth failure mode, so the ECU 2 clears the failure flags F2 and F3 in the subsequent step S17. Finish this routine. Thereby, the fourth failure mode in which the throttle valve 13 is fixed in the closed state can be specified.

  Next, in step S18, the ECU 2 determines whether or not the rotational speed of the electric compressor 4 is normal. Whether or not the rotational speed is normal can be determined from the relationship between the electric power supplied to the electric motor 4a and the rotational speed. In other words, the determination criterion is that the electric motor 4a is not supplied with power but the target rotational speed is not reached. Thereby, it is possible to determine whether the cause of the abnormality detected in the region A is due to the failure of the electric compressor 4 or the other. Accordingly, when an affirmative determination is made in step S18 that the rotational speed is normal, it is determined that the failure mode is the second failure mode. In step S19, the failure flag F3 is cleared and the current routine is terminated. Thereby, the 2nd failure mode which bypass valve 8 sticks in a full open state can be specified. On the other hand, when a negative determination is made in step S18 that the rotational speed of the electric compressor 4 is abnormal, in the subsequent step S20, the failure flag F2 is cleared and the current routine is terminated. Thereby, the 3rd failure mode in which electric compressor 4 fails can be specified.

  When a negative determination is made in step S13, an abnormality is detected in the region B, so that it is determined that the failure mode is either the first or fourth failure mode. Therefore, the ECU 2 sets failure flags F1 and F4 corresponding to the first and fourth failure modes in the subsequent step S21. Next, in step S22, it is determined whether or not there is an abnormality in the region A other than the region B where the abnormality is detected. This is the same processing as step S15 described above. Therefore, when a positive determination is made in step S22 that it is normal, it is determined that the failure mode is the first failure mode in which an abnormality occurs only in the region B, so the failure flag F4 is cleared in the next step S23. To finish the current routine. Thereby, the first failure mode in which the bypass valve 8 is fully closed and fixed can be specified. On the other hand, when a negative determination is made in step S22 that it is not normal (abnormal), it is determined that the failure mode is the fourth failure mode in which an abnormality occurs in both region A and region B. The flag F1 is cleared and the current routine is terminated. Thereby, the fourth failure mode in which the throttle valve 13 is fixed in the closed state can be specified. By executing the above steps S13 to S24, the ECU 2 functions as a failure mode determination unit and can specify one failure mode from each failure mode.

  Next, failure countermeasures according to the present embodiment will be described. The supercharging system executes a danger avoidance control routine shown in FIG. 9 and takes measures according to each failure mode. This control routine is executed in parallel with the control routine of FIG. 2, and is repeatedly executed at predetermined intervals according to a program stored in the ROM or the like of the ECU 2. This routine is executed by the ECU 2, whereby the ECU 2 functions as danger avoidance control means. As shown in FIG. 9, first, in step S31, the ECU 2 determines whether any of the above-described failure flags F1 to F4 is set. If any failure flag is set, the process proceeds to step S32 and subsequent steps. On the other hand, if any failure flag is not set, the subsequent processing is skipped and the current routine is finished.

  In step S32, the ECU 2 refers to the failure flag F1 and determines whether or not the failure mode is the first failure mode. If an affirmative determination is made in the first failure mode, the process proceeds to the subsequent step S33. In step S33, from the normal control over the opening degree of the variable nozzle 3c, the operating state of the engine 1 and the opening degree of the throttle valve 13 shown in FIG. ) Change to throttle valve fully open control. The first failure mode is a failure mode in which the bypass valve 8 is stuck in a fully closed state. For this reason, as the engine 1 rotates at a higher speed, the intake resistance by the electric compressor 4 increases and the burden on the engine 1 and the turbocharger 3 increases. Therefore, the opening degree of the variable nozzle 3c of the turbocharger 3 is forcibly changed to a fully open state, thereby lowering the back pressure of the engine 1 and suppressing an increase in the rotational speed of the turbocharger 3 (nozzle fully open control). And in order to prevent that the engine 1 will be in a high rotation state for the same reason, a restriction | limiting is added to a driving | running state (operation restriction | limiting control). For example, the accelerator opening is limited to less than a predetermined value. In the present embodiment, the accelerator opening is limited to less than 25%. As a result, the vehicle can travel, but cannot fully open, and the like, and a serious failure of the engine 1 and the supercharging system can be prevented. Furthermore, it is preferable that the throttle valve 13 is fully opened (throttle valve full open control). This is because the intake air amount by the electric compressor 4 is reduced as much as possible by increasing the intake air amount. In the first failure mode, since the operation of the electric compressor 4 is not hindered, it is desirable to permit the operation until choke is generated in the assist region described above.

  If a negative determination is made in step S32, the ECU 2 advances the process to step S34, and refers to the failure flag F2 to determine whether or not the failure mode is the second failure mode. If an affirmative determination is made in the second failure mode, the process proceeds to the subsequent step S35. In step S35, from the normal control over the opening degree of the variable nozzle 3c, the operating state of the electric compressor 4 and the opening degree of the throttle valve 13 shown in FIG. Control, (3) Change to throttle valve full open control. The second failure mode is a failure mode in which the bypass valve 8 is stuck in a fully opened state. For this reason, the intake air flows into the bypass passage 7 and effective assist cannot be realized even if the electric compressor 4 is operated. Therefore, the operation of the electric compressor 4 is prohibited (electric compressor operation prohibition control). Then, the opening degree of the variable nozzle 3c is reduced (nozzle restriction control). This nozzle aperture control is preferably performed in the assist region described above. Thereby, the acceleration performance at the time of low speed which falls by the operation prohibition of the electric compressor 4 can be supplemented. Furthermore, it is preferable that the opening degree of the throttle valve 13 is fully opened in the same manner as described above (throttle valve fully open control).

  If a negative determination is made in step S34, the ECU 2 advances the process to step S36, refers to the failure flag F3, and determines whether or not the failure mode is the third failure mode. When an affirmative determination is made in the third failure mode, the process proceeds to the next step S37. Since the third failure mode is a failure mode in which the electric compressor 4 has failed, effective supercharging assistance cannot be performed. Accordingly, as in the case of the second failure mode described above, the ECU 2 performs the normal control of FIG. 2 in step S37 (1) nozzle closing side control, (2) electric compressor operation inhibition control, and (3) throttle valve full open control. Change to

  If a negative determination is made in step S36, it can be seen that the failure mode is the fourth failure mode. Accordingly, the ECU 2 advances the processing to the next step S38, and changes the control for the opening degree of the variable nozzle 3c shown in FIG. 2 to feedback prohibition control. In the fourth failure mode, since the throttle valve 13 for adjusting the intake air amount is fixed in the closed state, the intake air amount is insufficient. For this reason, if feedback control using the supercharging pressure as described above as a target value is continued, the actual supercharging pressure does not increase in one direction, and there is a risk of a vicious circle in which the opening of the variable nozzle 3c is further narrowed down. Therefore, by prohibiting feedback control for the variable nozzle 3c, such a vicious circle can be broken.

(Second Embodiment)
Next, an internal combustion engine supercharging system according to a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, as shown in FIG. 10, the electric compressor 4 is provided in the intake pipe 5 downstream of the compressor 3 a of the turbocharger 3. Accordingly, a bypass passage 7 and a bypass valve 8 that bypass the electric compressor 4 are also provided on the downstream side of the compressor 3a. In the present embodiment, the differential pressure ΔP _i before and after (upstream and downstream) of the electric compressor 4 is adopted as a physical quantity for determining the operation characteristics. This is because the electric compressor 4 is disposed downstream of the compressor 3a. Therefore, a differential pressure sensor 25 for measuring the differential pressure ΔP _i is provided. However, in order to obtain ΔP _i , pressure sensors may be provided before and after the electric compressor 4, and the difference between them may be taken. Furthermore, in this embodiment, the introduction pipe 12 and the throttle valve 13 are not provided. Since the configuration other than the above is the same as that of the first embodiment, the same reference numerals are given and detailed description thereof is omitted.

In the present embodiment, as described above, the throttle valve 13 is not provided. Therefore, among the failure modes described in the first embodiment, the fourth failure mode in which the throttle valve 13 is closed and fixed is not assumed. Other failure mode characteristics and normal operation characteristics are the same except that the pressure P _i is changed to ΔP _i as shown in FIGS. That is, FIGS. 11, 12, and 13 correspond to FIGS. 3, 4, and 5 according to the first embodiment. Therefore, repeated explanation is omitted.

  The basic control control routine applied to the present embodiment is also the same as that in FIG. 2 according to the first embodiment. However, as described above, since the throttle valve 13 is not provided and the fourth failure mode is not assumed, the failure detection diagnosis routine and the risk avoidance control routine are different from those according to the first embodiment. Hereinafter, the difference will be mainly described. FIG. 14 is a flowchart showing a failure discovery diagnosis routine according to this embodiment. The processes common to those in FIGS. 7 and 8 are denoted by the same reference numerals.

As shown in FIG. 14, in the present embodiment, the differential pressure ΔP _i before and after the electric compressor 4 is adopted as the operating characteristic. Therefore, in the abnormality detection process (step S41), the differential pressure before and after the electric compressor 4 is detected. The determination is made when the difference between the target value ΔP _itrg and the actual measurement value ΔP _i exceeds a predetermined value. Further, since the fourth failure mode does not exist as described above, a process for discriminating between a failure mode in which an abnormality occurs in both the assist region (region A) and the non-assist region (region B) and another failure mode (FIG. 7, There are no 8 steps S15 and 22). Therefore, as shown in FIG. 14, when an abnormality is determined in region B in step S13 (NO), the ECU 2 can immediately specify the first failure mode in which an abnormality occurs only in region B (step S42). ). If an abnormality is determined in area A (YES), failure flags F2 and F3 are set because there is no fourth failure mode. The other processes are the same as those shown in FIGS.

  Next, in the danger avoidance control routine, as shown in FIG. 15, the process for dealing with the fourth failure mode (step S38 in FIG. 9) is omitted. Further, in the processes for the first to third failure modes (steps S51, S51, and S53), the change of control for the throttle valve 13 is omitted. The rest is the same as the control routine according to the first embodiment. Therefore, the technical significance of the nozzle fully open control and operation restriction control in step S51, the nozzle closing side control in steps S52 and S53, and the electric compressor operation inhibition control is the same as described above. For this reason, repeated description is omitted.

  As mentioned above, although the supercharging system for internal combustion engines of this invention was demonstrated based on 1st and 2nd embodiment, this invention is not limited to these embodiment. For example, in the first and second embodiments, the diesel engine 1 is used as an application target of the supercharging system of the present invention, but the type of the internal combustion engine is not limited. Therefore, the present invention may be applied to a spark ignition type gasoline engine or may be applied to other gasoline engines.

  In the above embodiment, the pressure or pressure difference is used as the physical quantity for determining the operating characteristics of the system. However, there is no particular limitation, and any system can be used as long as the system exhibits different behaviors during normal operation and abnormal operation. It may be a physical quantity. For example, the temperature or temperature difference at the same location as the above embodiment may be used. Also, the place where the sensor or the like is arranged may be other than the position shown in the figure.

Schematic which shows the whole structure of the supercharging system which concerns on 1st Embodiment of this invention. The flowchart which showed the outline | summary of the control routine of the supercharging system which concerns on 1st Embodiment. Explanatory drawing showing an example of the map which showed the operation characteristic at the time of normal time concerning 1st Embodiment. Explanatory drawing which showed the operating characteristic at the time of the 1st failure mode (bypass valve fully closed adhering) which concerns on 1st Embodiment. Explanatory drawing which showed the operating characteristic at the time of the 2nd failure mode (bypass valve full open adherence) based on 1st Embodiment, or the 3rd failure mode (electric compressor failure). Explanatory drawing which showed the operating characteristic at the time of the 4th failure mode (closed side adhesion of the throttle valve 13) which concerns on 1st Embodiment. The flowchart which showed the failure discovery diagnosis control routine which concerns on 1st Embodiment. 8 is a flowchart showing a control routine continued from FIG. The flowchart which showed the danger avoidance control routine which concerns on 1st Embodiment. Schematic which shows the whole structure of the supercharging system which concerns on 2nd Embodiment of this invention. Explanatory drawing showing an example of the map which showed the operating characteristic at the time of normal time concerning 2nd Embodiment. Explanatory drawing which showed the operating characteristic at the time of the 1st failure mode (bypass valve fully closed adhering) which concerns on 2nd Embodiment. Explanatory drawing which showed the operation characteristic at the time of the 2nd failure mode (bypass valve full open fixation) or 3rd failure mode (electric compressor failure) which concerns on 2nd Embodiment. The flowchart which showed the failure discovery diagnosis control routine which concerns on 2nd Embodiment. The flowchart which showed the danger avoidance control routine which concerns on 2nd Embodiment.

Explanation of symbols

1 Diesel engine (internal combustion engine)
2 ECU
3 Turbocharger 3a Compressor 3b Turbine 3c Variable nozzle 4 Electric compressor 5 Intake pipe (intake passage)
7 Bypass passage 8 Bypass valve (switching valve)
13 Throttle valve (regulating valve)
23 Pressure sensor 25 Differential pressure sensor

Claims (15)

A turbocharger that supercharges the internal combustion engine using exhaust energy of the internal combustion engine, an electric compressor provided in an intake passage upstream or downstream of the compressor of the turbocharger, and the electric compressor A bypass passage that is bypassed and a switch that is provided in the bypass passage and that can be opened and closed to close the bypass passage when the electric compressor is in operation and to open the bypass passage when the electric compressor is not in operation A supercharging system for an internal combustion engine, comprising: a valve; and a supercharging system control means for controlling the electric compressor so that the electric compressor is in a first state in which the electric compressor is operating or a second state in which the electric compressor is inactive Because
Abnormality detection means for detecting an abnormality of the system operating beyond the allowable range from a normal value set in advance as normal operating characteristics of the system in each state, and preset as a condition to be controlled in the first state A failure mode in which the abnormality is detected only in the assist region by determining in which region of the assist region and the non-assist region set in advance as a condition to be controlled to the second state; A supercharging system for an internal combustion engine, comprising: a failure diagnosis unit that includes a failure mode determination unit that determines a failure mode in which the abnormality is detected only in the non-assist region.   2. The supercharging system for an internal combustion engine according to claim 1, wherein the failure mode in which the abnormality is detected only in the non-assist region is a first failure mode in which the switching valve is fixed in a fully closed state.   In the case where there are a plurality of failure modes in which the abnormality is detected only in the assist region, the failure mode determination means considers the rotation speed of the electric compressor in the assist region, and the plurality of types of failure modes. The supercharging system for an internal combustion engine according to claim 1 or 2, wherein one failure mode is specified from the above.   The supercharging for an internal combustion engine according to claim 3, wherein the plurality of types of failure modes are a second failure mode in which the switching valve is fixed in a fully opened state and a third failure mode in which the electric compressor fails. system.   When the abnormality is detected, the failure mode determination means determines the presence or absence of the abnormality in a region other than the region where the abnormality is detected, and the abnormality is detected in both the assist region and the non-assist region. The at least one failure mode in which the abnormality is detected, the failure mode in which the abnormality is detected only in the assist region, and the failure mode in which the abnormality is detected only in the non-assist region are discriminated. The supercharging system for internal combustion engines as described in any one of -4. The electric compressor is provided in the intake passage upstream of the compressor of the turbocharger;
Provided in the intake passage upstream of the electric compressor, further comprising an adjustment valve for adjusting the amount of air flowing into the intake passage;
The internal combustion engine according to claim 5, wherein the failure mode in which the abnormality is detected in both the assist region and the non-assist region is a fourth failure mode in which the regulating valve is fixed in a closed state. Supercharging system. The electric compressor is provided in the intake passage upstream of the compressor of the turbocharger;
The normal value is determined according to an intake air flow rate flowing into the intake passage, and is a pressure in the intake passage between the electric compressor and the compressor of the turbocharger. The supercharging system for internal combustion engines as described in any one of 1-6.   7. The internal combustion engine according to claim 1, wherein the normal value is a differential pressure upstream and downstream of the electric compressor determined according to an intake air flow rate flowing into the intake passage. Supercharging system for engines. A supercharging system for an internal combustion engine applied to an internal combustion engine provided with an internal combustion engine control means for controlling an operating state of the internal combustion engine,
A turbocharger comprising a compressor and a turbine, and a variable nozzle for changing a flow rate of exhaust gas to the turbine, and supercharging the internal combustion engine using exhaust energy of the internal combustion engine, and the turbocharger An electric compressor provided in the intake passage upstream or downstream of the compressor, a bypass passage that bypasses the electric compressor, and provided in the bypass passage, and closes the bypass passage when the electric compressor is in operation, A switching valve that can be opened and closed to open the bypass passage when the electric compressor is inactive, a supercharging system control means that controls the opening of the variable nozzle and the operating state of the electric compressor, and a system abnormality Fault diagnosis means for identifying any of a plurality of preset failure modes when a fault is detected; Risk avoidance control means for changing control over at least one of the opening degree of the variable nozzle, the operating state of the electric compressor, and the operating state of the internal combustion engine according to the failure mode specified by the diagnosis means. A supercharging system for an internal combustion engine.   The danger avoidance control means is a nozzle full open control that controls the opening of the variable nozzle to a fully open state when the first failure mode in which the switching valve is fixed in a fully closed state is specified by the failure diagnosis means. The supercharging system for an internal combustion engine according to claim 9, wherein the supercharging system is changed to an operation restriction control that restricts the operation state of the internal combustion engine to less than a predetermined output.   The danger avoidance control means controls the opening degree of the variable nozzle to the closed side state when the second failure mode in which the switching valve is fixed in the fully opened state is specified by the failure diagnosis means. The supercharging system for an internal combustion engine according to claim 9, wherein the control is changed to an electric compressor operation prohibition control that prohibits the operation of the electric compressor. The electric compressor is provided in the intake passage upstream of the compressor of the turbocharger;
Provided in the intake passage upstream of the electric compressor, further comprising an adjustment valve for adjusting the amount of air flowing into the intake passage;
The control means further controls the opening of the regulating valve,
The supercharging system for an internal combustion engine according to claim 10 or 11, wherein the danger avoidance control means further changes to an adjustment valve full open control for controlling the opening of the adjustment valve to a full open state.   When the third failure mode in which the electric compressor fails is specified by the failure diagnosis unit, the risk avoidance control unit changes to a closed side control that controls the opening of the variable nozzle to a closed side state. The supercharging system for an internal combustion engine according to claim 9, wherein the control is changed to an electric compressor operation prohibition control for prohibiting the operation of the electric compressor. The electric compressor is provided in the intake passage upstream of the compressor of the turbocharger;
Provided in the intake passage upstream of the electric compressor, further comprising an adjustment valve for adjusting the amount of air flowing into the intake passage;
The control means further controls the opening of the regulating valve,
The danger avoidance control means is changed to feedback prohibition control for prohibiting feedback control of the opening degree of the variable nozzle when the failure diagnosis means specifies a fourth failure mode in which the regulating valve is fixed in a closed state. The supercharging system for an internal combustion engine according to claim 9. 12. The nozzle closing side control is performed only in an assist region set in advance as a region where the electric compressor is operated to assist supercharging of the turbocharger to the internal combustion engine. Or the supercharging system for internal combustion engines of Claim 13.

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