JP2011226437A - Abnormality detection device and method of egr system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine which a high pressure EGR device and a low pressure EGR device has an abnormality when EGR gas is supplied from both the high pressure EGR device and the low pressure EGR device.SOLUTION: An abnormality detection device of an EGR system includes the high pressure EGR device that supplies high pressure EGR gas from an exhaust passage on an upstream than a turbine to an intake passage, and the low pressure EGR device that supplies low pressure EGR gas from the exhaust passage on a downstream than the turbine to the intake passage. The abnormality of the low pressure EGR device is detected from the opening of a high pressure EGR valve when the high pressure EGR gas and the low pressure EGR gas are supplied and also when the high pressure EGR valve is under the feedback control while a low pressure EGR valve is under open-loop control. Afterwards, the abnormality of the high pressure EGR valve is detected from the opening of the low pressure EGR valve when the low pressure EGR valve is under feedback control while the high pressure EGR valve is under the open-loop control.

Description

  The present invention relates to an abnormality detection device and an abnormality detection method for an EGR system.

  A high pressure EGR device that supplies EGR gas (hereinafter referred to as high pressure EGR gas) from an EGR passage (hereinafter referred to as high pressure EGR passage) that connects an exhaust passage upstream of the turbine and an intake passage; and a downstream of the turbine In an EGR system comprising: a low pressure EGR device that supplies EGR gas (hereinafter referred to as low pressure EGR gas) from an EGR passage (hereinafter referred to as low pressure EGR passage) connecting the exhaust passage and the intake passage. A technique for determining clogging based on a pressure difference between an exhaust passage and an intake passage is known (see, for example, Patent Document 1).

  In this technique, a pressure sensor is provided in each of the exhaust passage and the intake passage in order to detect clogging of the low pressure EGR passage. Thus, since it is necessary to provide a separate sensor, the cost is increased and the apparatus is complicated.

  By the way, the supply mode of EGR gas may be changed according to the operation region of the internal combustion engine. For example, high-pressure EGR gas is supplied only from the high-pressure EGR device at low rotation and low load, and low-pressure EGR gas is supplied from only the low-pressure EGR device at high rotation or high load. In addition, low pressure EGR gas and high pressure EGR gas may be supplied from both the low pressure EGR device and the high pressure EGR device to other medium loads. Further, when both the low pressure EGR gas and the high pressure EGR gas are supplied, a large amount of the low pressure EGR gas is supplied, and a small amount of the high pressure EGR gas is supplied so that the temperature of the intake manifold is not excessively lowered by the low pressure EGR gas. Things have been done.

  Here, when the EGR gas amount is excessive or insufficient when the EGR gas is supplied from only one of the low pressure EGR device and the high pressure EGR device, the EGR gas is supplied at that time. It can be determined that there is an abnormality in the device. However, if an excess or deficiency of the amount of EGR gas occurs while supplying EGR gas from both the low pressure EGR device and the high pressure EGR device, the excess or deficiency of one EGR gas is eliminated by the other EGR gas. Therefore, it is difficult to detect an abnormality. Even if it is found that the amount of EGR gas is excessive or insufficient, it is difficult to distinguish whether there is an abnormality in the low pressure EGR device or an abnormality in the high pressure EGR device.

  For example, when supplying the EGR gas using both the low pressure EGR device and the high pressure EGR device, if the high pressure EGR device is feedback controlled and the low pressure EGR device is open loop controlled, the amount of EGR gas is the target value. The high-pressure EGR device is controlled so that only a small amount of high-pressure EGR gas is supplied to low-pressure EGR gas. For this reason, even if the amount of the high-pressure EGR gas is insufficient, the shortage amount is small compared to the supply amount of the low-pressure EGR gas amount, and thus it is difficult to detect an abnormality. In addition, when the low pressure EGR gas is excessive or insufficient, the excess or shortage is eliminated by feedback control of the high pressure EGR device, so that it is difficult to detect an abnormality.

  In addition, for example, if the vehicle continues running in a medium load region (for example, the vehicle speed is around 60 to 80 km / h) immediately after the EGR control is not performed, a period during which both the low pressure EGR gas and the high pressure EGR gas are supplied. Therefore, it is difficult to detect an abnormality using EGR feedback control when only one of the low pressure EGR gas and the high pressure EGR gas is supplied. Since the internal combustion engine is often operated in a medium load or medium rotation region, it is only necessary to determine whether the apparatus is abnormal when EGR gas is supplied from only one of the low pressure EGR device and the high pressure EGR device. Then, it is not possible to obtain a sufficient opportunity to determine the abnormality of the apparatus.

JP 2007-292028 A JP 2008-223554 A JP 2007-315371 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a high-pressure EGR device or a low-pressure EGR device when both EGR gas is supplied from the high-pressure EGR device and the low-pressure EGR device. It is to determine which is abnormal.

In order to achieve the above object, the abnormality detection apparatus for an EGR system according to the present invention employs the following means. That is, the abnormality detection device for the EGR system according to the present invention is:
A turbocharger having a turbine in the exhaust passage of the internal combustion engine and a compressor in the intake passage;
A high-pressure EGR device having a high-pressure EGR passage connecting the exhaust passage upstream of the turbine and the intake passage, and a high-pressure EGR valve for adjusting the amount of EGR gas flowing through the high-pressure EGR passage;
A low pressure EGR device having a low pressure EGR passage connecting the exhaust passage downstream of the turbine and the intake passage, and a low pressure EGR valve for adjusting an amount of EGR gas flowing through the low pressure EGR passage;
A high pressure EGR valve opening degree detection device for detecting the opening degree of the high pressure EGR valve;
A low pressure EGR valve opening degree detecting device for detecting an opening degree of the low pressure EGR valve;
In the EGR system abnormality detection device comprising:
When EGR gas is supplied from both the high-pressure EGR device and the low-pressure EGR device, one of the low-pressure EGR valve and the high-pressure EGR valve is controlled in an open loop, while the other EGR valve is The EGR device having the one EGR valve has an abnormality from the opening degree of the other EGR valve when the EGR gas amount in the cylinder is feedback-controlled so that the EGR gas amount in the cylinder goes to the target range of the EGR gas amount Whether or not
Thereafter, when EGR gas is supplied from both the high pressure EGR device and the low pressure EGR device, the other EGR valve is controlled in an open loop, and the one EGR valve is moved to the EGR gas in the cylinder. Determination to determine whether or not there is an abnormality in the other EGR device having the other EGR valve based on the opening degree of the one EGR valve when feedback control is performed so that the amount goes to the target range of the EGR gas amount Means are provided.

  Here, when the EGR gas is supplied from both the high pressure EGR device and the low pressure EGR device, both the high pressure EGR valve and the low pressure EGR valve are opened, and the EGR gas is circulated through the high pressure EGR passage and the low pressure EGR passage, respectively. When you are. In addition, there are times when EGR gas is supplied only from the high-pressure EGR device, or EGR gas is supplied only from the low-pressure EGR device.

When EGR gas is supplied from both the high-pressure EGR device and the low-pressure EGR device, the high-pressure EGR valve and the low-pressure EGR valve are opened respectively. At this time, for example, the low-pressure EGR valve is controlled by open loop, and the high-pressure EGR valve is turned on. Feedback control. At this time, the low-pressure EGR valve has an opening degree corresponding to, for example, the engine speed and the engine load. That is, if the operating state of the internal combustion engine is constant, the opening of the low pressure EGR valve is also constant. Further, the opening degree of the high pressure EGR valve is adjusted so that the EGR gas amount becomes a target value. At this time, the opening degree of the high pressure EGR valve may be adjusted so that the intake air amount becomes a target value. Here, since EGR gas and air are sucked into the cylinder, when the amount of EGR gas decreases, the amount of air increases correspondingly, and when the amount of EGR gas increases, the amount of air decreases accordingly. For this reason, if the air amount becomes the target value, the EGR gas amount also becomes the target value. It should be noted that the target value of the air amount or the EGR gas amount may have a range to be a target range.

  For example, when the intake air amount is smaller than the target value, the high pressure EGR valve is adjusted to the closed side so as to decrease the EGR gas amount on the assumption that the EGR gas amount is excessive. On the other hand, when the intake air amount is larger than the target value, the high pressure EGR valve is adjusted to the open side so as to increase the EGR gas amount because the EGR gas amount is insufficient. In this way, the amount of EGR gas supplied into the cylinder is adjusted by the high pressure EGR valve. That is, even if the low pressure EGR device causes an excess or deficiency in the EGR gas amount in the cylinder, the excess or deficiency of the EGR gas amount can be eliminated by adjusting the opening of the high pressure EGR valve.

  By the way, when the low-pressure EGR passage is abnormal, such as when the low-pressure EGR passage is clogged, and the degree of excess or deficiency in the EGR gas amount increases, the opening of the high-pressure EGR valve becomes different from the normal opening. The opening degree of the high pressure EGR valve at this time is changed in a direction to eliminate the excess or deficiency of the EGR gas amount. Thus, the abnormality of the low pressure EGR device appears in the opening degree of the high pressure EGR valve. For this reason, the abnormality of the low pressure EGR device can be determined based on the opening degree of the high pressure EGR valve.

  On the other hand, even if there is an abnormality in the high pressure EGR device such as clogging of the high pressure EGR passage and the degree of excess or deficiency in the amount of EGR gas increases, the amount of EGR gas supplied from the high pressure EGR device may be small. It is difficult to detect an abnormality even if the gas amount is excessive or insufficient and the opening degree of the high pressure EGR valve is observed. On the other hand, when the abnormality of the high pressure EGR device is determined, the high pressure EGR valve is subjected to open loop control and the low pressure EGR valve is feedback controlled. That is, the control target for feedback control of the EGR gas amount is switched between the abnormality determination of the low pressure EGR device and the abnormality determination of the high pressure EGR device. When the high-pressure EGR device is abnormal, such as when the high-pressure EGR passage is clogged, and the degree of excess or deficiency in the EGR gas amount increases, the opening degree of the low-pressure EGR valve is greatly changed in a direction to eliminate the excess or deficiency in the EGR gas amount. . That is, an abnormality in the high pressure EGR device appears in the opening of the low pressure EGR valve. For this reason, the abnormality of the high pressure EGR device can be determined based on the opening degree of the low pressure EGR valve.

  And since it only switches the object of feedback control when determining the abnormality of each EGR apparatus, the influence which it has on a combustion state or an exhaust state can be made small.

  In the present invention, the determination means determines that the low pressure EGR device is abnormal when the opening of the high pressure EGR valve is out of a specified range, and the opening of the low pressure EGR valve is out of a specified range. Sometimes it can be determined that there is an abnormality in the high-pressure EGR device.

  Here, if there is no abnormality in the low pressure EGR device and the high pressure EGR device, the amount of EGR gas can be adjusted to the target value without greatly changing the opening degree of the high pressure EGR valve and the low pressure EGR valve. The opening degree of the low pressure EGR valve is within a specified range. That is, if the opening degree of the high pressure EGR valve and the low pressure EGR valve is feedback controlled within the specified range, the EGR gas amount is within the target range, and it can be determined that the low pressure EGR device and the high pressure EGR device are normal. . On the other hand, when the opening degree of the high pressure EGR valve or the low pressure EGR valve is larger than the specified range or smaller than the specified range by feedback control, it can be determined that there is an abnormality in the low pressure EGR device or the high pressure EGR device. . The specified range is a range of the opening degree of the high pressure EGR valve or the low pressure EGR valve when there is no abnormality in the low pressure EGR device. Further, the specified range may be different between the low pressure EGR valve and the high pressure EGR valve.

Further, in the present invention, the determination means determines the opening degree of the high pressure EGR valve when the high pressure EGR valve is controlled in an open loop by using EGR gas from both the high pressure EGR device and the low pressure EGR device. It can be made larger than when the high-pressure EGR valve is being fed back and fed.

  When the high pressure EGR valve is feedback controlled, it may be determined whether or not there is an abnormality in the low pressure EGR device, and both the abnormality determination of the low pressure EGR device and the abnormality determination of the high pressure EGR device are performed. It's okay if you don't. Note that when the high pressure EGR valve is feedback controlled, the opening degree of the high pressure EGR valve can change, so that the high pressure EGR valve has a higher opening degree than the range where the opening degree of the high pressure EGR valve can change. The opening degree may be increased. Further, the opening degree of the high pressure EGR valve when the high pressure EGR valve is open-loop controlled is made larger than the opening degree of the low pressure EGR valve, and the low pressure EGR valve is opened when the low pressure EGR valve is open loop controlled. The opening degree may be larger than the opening degree of the high pressure EGR valve.

  Here, when EGR gas is supplied from both the low pressure EGR device and the high pressure EGR device, generally, the opening degree of the high pressure EGR valve is made smaller than the opening degree of the low pressure EGR valve. For this reason, even if there is an abnormality in the high pressure EGR device and the opening degree of the low pressure EGR valve is adjusted, the amount of change may be small. If it does so, there exists a possibility that the precision of the abnormality determination of a high voltage | pressure EGR apparatus may become low. On the other hand, if the target value of the opening degree of the high pressure EGR valve is increased, the target value of the opening degree of the low pressure EGR valve is reduced, so that an abnormality of the high pressure EGR device appears remarkably in the opening degree of the low pressure EGR valve. For this reason, the accuracy of the abnormality determination of the high-pressure EGR device can be improved.

In order to achieve the above object, the abnormality detecting method for the EGR system according to the present invention employs the following means. That is, the abnormality detection method of the EGR system according to the present invention is:
A high-pressure EGR device having a high-pressure EGR passage connecting an exhaust passage upstream of a turbine of a turbocharger of the internal combustion engine and an intake passage, and a high-pressure EGR valve for adjusting the amount of EGR gas flowing through the high-pressure EGR passage;
A low pressure EGR device having a low pressure EGR passage connecting an exhaust passage downstream of the turbine and an intake passage, and a low pressure EGR valve for adjusting an amount of EGR gas flowing through the low pressure EGR passage;
When EGR gas is supplied from both
The first low-pressure EGR valve or the high-pressure EGR valve is subjected to open-loop control, and the other EGR valve is feedback-controlled so that the EGR gas amount in the cylinder is directed to the target range of the EGR gas amount. Process,
A second step of determining whether there is an abnormality in one of the EGR devices having the one EGR valve, based on the opening degree of the other EGR valve when the first step is being performed;
A third step of performing feedback control so that the EGR gas amount in the cylinder is directed to a target range of the EGR gas amount while performing open-loop control of the other EGR valve;
A fourth step of determining whether or not there is an abnormality in the other EGR device having the other EGR valve from the opening degree of the one EGR valve when the third step is being performed;
It is characterized by including.

  Further, it can be determined that there is an abnormality in the low pressure EGR device when the opening of the high pressure EGR valve is outside a specified range. Furthermore, it can be determined that there is an abnormality in the high pressure EGR device when the opening of the low pressure EGR valve is outside a specified range.

  According to the present invention, when both the high pressure EGR device and the low pressure EGR device are supplying EGR gas, it is possible to determine whether the high pressure EGR device or the low pressure EGR device is abnormal.

It is a figure which shows schematic structure of the internal combustion engine which concerns on an Example, and its intake / exhaust system. It is the figure which showed the relationship between the engine speed, an engine load, and the control mode of EGR feedback control. It is the figure which showed the control method in each control mode. It is the time chart which showed transition of the opening degree of a high pressure EGR valve, the opening degree of a low pressure EGR valve, and an EGR rate. It is the time chart which showed transition of the opening degree of a high pressure EGR valve, the opening degree of a low pressure EGR valve, and an EGR rate. It is the flowchart which showed the flow which determines the abnormality of the EGR system which concerns on an Example.

  Hereinafter, specific embodiments of an abnormality detection device and an abnormality detection method for an EGR system according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2. In the present embodiment, a diesel engine will be described as an example, but the present invention can be similarly applied to other gasoline engines.

  An intake passage 3 and an exhaust passage 4 are connected to the internal combustion engine 1. A compressor 5 a of a turbocharger 5 that operates using exhaust energy as a drive source is provided in the middle of the intake passage 3. The intake passage 3 upstream of the compressor 5 a is provided with a first intake throttle valve 6 that adjusts the flow rate of intake air flowing through the intake passage 3. The first intake throttle valve 6 is opened and closed by an electric actuator. An air flow meter 7 is provided in the intake passage 3 upstream of the first intake throttle valve 6 to output a signal corresponding to the flow rate of the air flowing through the intake passage 3. The air flow meter 7 measures the intake air amount of the internal combustion engine 1.

  An intercooler 8 that performs heat exchange between the intake air and the outside air is provided in the intake passage 3 downstream of the compressor 5a. The intake passage 3 downstream of the intercooler 8 is provided with a second intake throttle valve 9 that adjusts the flow rate of intake air flowing through the intake passage 3. The second intake throttle valve 9 is opened and closed by an electric actuator.

  On the other hand, a turbine 5 b of the turbocharger 5 is provided in the middle of the exhaust passage 4. Further, a particulate filter (hereinafter simply referred to as a filter) 10 is provided in the exhaust passage 4 downstream of the turbine 5b. The filter 10 may carry a catalyst, for example.

  The internal combustion engine 1 is provided with a low pressure EGR device 30 that recirculates a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a low pressure. The low pressure EGR device 30 includes a low pressure EGR passage 31, a low pressure EGR valve 32, and an EGR cooler 33.

The low pressure EGR passage 31 connects the exhaust passage 4 downstream of the filter 10 and the intake passage 3 upstream of the compressor 5a and downstream of the first intake throttle valve 6. Through this low pressure EGR passage 31, the exhaust gas is recirculated at a low pressure. In this embodiment, the exhaust gas recirculated through the low pressure EGR passage 31 is referred to as low pressure EGR gas. Low pressure EGR
The exhaust passage 4 side of the passage 31 may be connected downstream of the turbine 5b. Further, the intake passage 3 side of the low-pressure EGR passage 31 may be connected upstream of the compressor 5a.

  Further, the low pressure EGR valve 32 adjusts the amount of the low pressure EGR gas flowing through the low pressure EGR passage 31 by adjusting the passage sectional area of the low pressure EGR passage 31. An opening degree sensor 34 that detects the opening degree of the low pressure EGR valve 32 is attached to the low pressure EGR valve 32. Further, the EGR cooler 33 exchanges heat between the low-pressure EGR gas passing through the EGR cooler 33 and the cooling water of the internal combustion engine 1 to lower the temperature of the low-pressure EGR gas. In this embodiment, the opening degree sensor 34 corresponds to the low pressure EGR valve opening degree detecting device in the present invention.

  The internal combustion engine 1 is also provided with a high-pressure EGR device 40 that recirculates part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 at a high pressure. The high pressure EGR device 40 includes a high pressure EGR passage 41 and a high pressure EGR valve 42.

  The high pressure EGR passage 41 connects the exhaust passage 4 upstream of the turbine 5 b and the intake passage 3 downstream of the second intake throttle valve 9. Exhaust gas is recirculated at high pressure through the high pressure EGR passage 41. In this embodiment, the exhaust gas recirculated through the high pressure EGR passage 41 is referred to as high pressure EGR gas. The exhaust passage 4 side of the high pressure EGR passage 41 only needs to be connected upstream of the turbine 5b. Further, the intake passage 3 side of the high pressure EGR passage 41 may be connected downstream of the compressor 5a.

  Further, the high pressure EGR valve 42 adjusts the amount of high pressure EGR gas flowing through the high pressure EGR passage 41 by adjusting the passage sectional area of the high pressure EGR passage 41. An opening degree sensor 44 that detects the opening degree of the high pressure EGR valve 42 is attached to the high pressure EGR valve 42. In the present embodiment, the opening sensor 44 corresponds to the high-pressure EGR valve opening detection device in the present invention.

  The internal combustion engine 1 configured as described above is provided with an ECU 20 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 20 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the above sensor, the ECU 20 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 14 by the driver, and an accelerator opening sensor 15 that can detect the engine load, and a crank position that detects the engine speed. Sensors 16 are connected via electric wiring, and output signals from these various sensors are input to the ECU 20. On the other hand, the ECU 20 is connected to the first intake throttle valve 6, the second intake throttle valve 9, the low pressure EGR valve 32, and the high pressure EGR valve 42 through electric wiring, and these devices are controlled by the ECU 20. The

  Here, the ECU 20 supplies the EGR gas from the low-pressure EGR device 30 or the high-pressure EGR device 40, or both devices according to the operation state (for example, the engine speed and the engine load) of the internal combustion engine 1. Decide whether to supply from. And when supplying EGR gas, EGR feedback control is performed. The EGR feedback control is performed when EGR gas is supplied only from the low pressure EGR device 30, when EGR gas is supplied only from the high pressure EGR device 40, or when EGR gas is supplied from both the low pressure EGR device 30 and the high pressure EGR device 40. Different for each.

  FIG. 2 is a diagram showing the relationship between the engine speed, the engine load, and the control mode of EGR feedback control. FIG. 3 is a diagram showing a control method in each control mode.

  When both the engine speed and the engine load are low (low rotation and low load region), the EGR gas is supplied using only the high pressure EGR device 40. This operation region is referred to as an HPL region. Even when the cooling water temperature is low, the EGR gas is supplied using only the high-pressure EGR device 40. The EGR feedback control at this time is performed by adjusting the opening degree of the high pressure EGR valve 42 so that the intake air amount obtained by the air flow meter 7 becomes a target value. The target value of the intake air amount is determined according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load). At this time, the low pressure EGR valve 32 is maintained fully closed.

  For example, when the intake air amount obtained by the air flow meter 7 is smaller than the target value, the opening degree of the high pressure EGR valve 42 is decreased so as to decrease the EGR gas amount, assuming that the EGR gas amount is larger than the target value. To do. Further, for example, when the intake air amount obtained by the air flow meter 7 is larger than the target value, the opening degree of the high pressure EGR valve 42 is set so that the EGR gas amount is increased on the assumption that the EGR gas amount is smaller than the target value. Enlarge.

  Hereinafter, a control mode for supplying EGR gas using only the high-pressure EGR device 40 is referred to as an HPL mode. It should be noted that the target value of the intake air amount and the target value of the EGR gas amount may be set to a target range with a certain range. When the EGR gas amount can be directly measured by a sensor or the like, the opening degree of the high pressure EGR valve 42 may be adjusted so that the EGR gas amount becomes a target value or a target range.

  Next, when at least one of the engine speed and the engine load is high (high rotation region, high load region), EGR gas is supplied using only the low pressure EGR device 30. This operation region is referred to as an LPL region. The EGR feedback control at this time is performed by adjusting the opening degree of the low pressure EGR valve 32 so that the intake air amount obtained by the air flow meter 7 becomes a target value. The target value of the intake air amount is determined according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load). At this time, the high pressure EGR valve 42 is kept fully closed.

  For example, when the amount of intake air obtained by the air flow meter 7 is smaller than the target value, the opening degree of the low pressure EGR valve 32 is decreased so that the EGR gas amount is decreased on the assumption that the EGR gas amount is larger than the target value. To do. Further, for example, when the intake air amount obtained by the air flow meter 7 is larger than the target value, it is assumed that the EGR gas amount is smaller than the target value, and the opening degree of the low pressure EGR valve 32 is increased so as to increase the EGR gas amount. Enlarge.

  Hereinafter, a control mode for supplying EGR gas using only the low-pressure EGR device 30 is referred to as an LPL mode. It should be noted that the target value of the intake air amount and the target value of the EGR gas amount may be set to a target range with a certain range. Further, when the EGR gas amount can be directly measured by a sensor or the like, the opening degree of the low pressure EGR valve 32 may be adjusted so that the EGR gas amount becomes a target value or a target range.

  A region between the HPL region and the LPL region is referred to as an MPL region. The MPL region is an operation region when the engine load is medium (medium load region). And it is an operation area | region where EGR gas is supplied using both the low voltage | pressure EGR apparatus 30 and the high voltage | pressure EGR apparatus 40. FIG. In this EGR feedback control, the opening degree of the high pressure EGR valve 42 is adjusted so that the amount of intake air obtained by the air flow meter 7 becomes a target value. The target value of the intake air amount is determined according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load). Further, the opening degree of the low pressure EGR valve 32 at this time is determined according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load). That is, the high pressure EGR valve 42 is feedback controlled, and the low pressure EGR valve 32 is open loop controlled.

For example, when the intake air amount obtained by the air flow meter 7 is smaller than the target value, the opening degree of the high pressure EGR valve 42 is decreased so as to decrease the EGR gas amount, assuming that the EGR gas amount is larger than the target value. To do. Further, for example, when the intake air amount obtained by the air flow meter 7 is larger than the target value, the opening degree of the high pressure EGR valve 42 is set so that the EGR gas amount is increased on the assumption that the EGR gas amount is smaller than the target value. Enlarge. In any case, the opening degree of the low pressure EGR valve 32 is determined regardless of the EGR gas amount and the intake air amount. That is, the sum of the low pressure EGR gas amount and the high pressure EGR gas amount is adjusted by the high pressure EGR valve 42.

  Hereinafter, a control mode in which EGR gas is supplied using both the low pressure EGR device 30 and the high pressure EGR device 40 is referred to as an MPL mode. It should be noted that the target value of the intake air amount and the target value of the EGR gas amount may be set to a target range with a certain range. When the EGR gas amount can be directly measured by a sensor or the like, the opening degree of the high pressure EGR valve 42 may be adjusted so that the EGR gas amount becomes a target value or a target range.

  Here, when particulate matter in the exhaust gas adheres to the low-pressure EGR passage 31 or the high-pressure EGR passage 41 and the cross-sectional area of the passage becomes small or the passage is clogged, the low-pressure EGR passage 31 or the high-pressure EGR passage An abnormality occurs in which the amount of EGR gas flowing through 41 is smaller than normal. In the HPL mode and the LPL mode, since the EGR gas is supplied only from one EGR device, it is possible to determine an abnormality relatively easily.

  That is, in the HPL mode, the target value of the EGR rate is compared with the actual value, and it can be determined that there is an abnormality in the high-pressure EGR device 40 when this difference exceeds a threshold value, for example. Thus, since the EGR rate in the HPL mode changes only depending on the amount of EGR gas supplied from the high pressure EGR device 40, if the EGR rate is out of the target range, the high pressure EGR device 40 is abnormal. Can be judged. Further, when the correction amount or the opening when the opening degree of the high pressure EGR valve 42 is feedback controlled is out of the normal range, it may be determined that the high pressure EGR device 40 is abnormal.

  Similarly, also in the LPL mode, the target value of the EGR rate is compared with the actual value, and for example, when this difference exceeds the threshold value, it can be determined that the low-pressure EGR device 30 is abnormal. . That is, since the EGR rate in the LPL mode changes only by the amount of EGR gas supplied from the low pressure EGR device 30, if the EGR rate is out of the target range, it can be determined that the low pressure EGR device 30 is abnormal. . Further, when the correction amount or the opening when the opening of the low pressure EGR valve 32 is feedback-controlled is outside the normal range, it may be determined that the low pressure EGR device 30 is abnormal.

  However, in the MPL mode, it is difficult to determine whether the low-pressure EGR device 30 or the high-pressure EGR device 40 is abnormal only by detecting the intake air amount or the EGR gas amount in the cylinder.

  Here, even when the high pressure EGR passage 41 is clogged, in the MPL region, the low pressure EGR valve 32 is open-loop controlled with a relatively large opening, so a large amount of low pressure EGR gas is supplied. . Further, since the high pressure EGR valve 42 is feedback controlled with a relatively small opening, even if the high pressure EGR passage 41 is clogged and the amount of the high pressure EGR gas is reduced, the high pressure EGR valve 42 is absorbed by a large amount of the low pressure EGR gas. As a result, the difference between the opening degree of the high-pressure EGR valve 42 and the target value (target EGR) of the EGR rate and the actual value (actual EGR) does not show any abnormality, and is substantially the same as in the normal state.

When the low pressure EGR passage 31 is clogged, a large amount of low pressure EGR gas cannot be supplied by open loop control of the opening degree of the low pressure EGR valve 32. Therefore, the opening degree of the high pressure EGR valve 42 for which feedback control is performed with a small opening degree becomes larger than usual in order to compensate for the shortage of the low pressure EGR gas. At this time, the difference between the target value (target EGR) of the EGR rate and the actual value (actual EGR) does not show any abnormality, and is almost the same as in the normal state.

  As described above, when the high pressure EGR valve 42 is feedback-controlled and the low pressure EGR valve 32 is open-loop controlled in the MPL mode, the abnormality of the low pressure EGR device 30 is determined based on the opening degree of the high pressure EGR valve 42. Can be detected, but an abnormality of the high-pressure EGR device 40 cannot be detected.

  Therefore, in this embodiment, first, abnormality of the low pressure EGR device 30 is determined based on the opening degree of the high pressure EGR valve 42 in the MPL mode. That is, if the low-pressure EGR device 30 is abnormal and the EGR rate is out of the target range, the opening degree of the high-pressure EGR valve 42 is adjusted, so that the low-pressure EGR device 30 is abnormal based on the opening degree of the high-pressure EGR valve 42. It can be determined that there is.

  Here, FIG. 4 is a time chart showing changes in the opening degree of the high pressure EGR valve 42, the opening degree of the low pressure EGR valve 32, and the EGR rate. A solid line indicates a case where the low pressure EGR device 30 and the high pressure EGR device 40 are normal, and a broken line indicates a case where the low pressure EGR passage 31 is clogged.

  The opening degree of the high-pressure EGR valve 42 is increased in order to compensate for the decrease in the low-pressure EGR gas due to the clogging of the low-pressure EGR passage 31 when abnormal. For example, when the opening degree of the high pressure EGR valve 42 is equal to or greater than the threshold value, it is determined that there is an abnormality in which the low pressure EGR gas amount decreases. Note that the opening of the low pressure EGR valve 32 is open-loop control, so that there is no change even if there is an abnormality in the low pressure EGR passage 31. In addition, since the actual value of the EGR rate is adjusted to the target value by adjusting the opening degree of the high pressure EGR valve 42, the EGR rate is not different between when it is normal and when it is abnormal.

  Next, a method for determining whether or not there is an abnormality in the high-pressure EGR device 40 in the MPL mode will be described. Even when the high pressure EGR passage 41 is clogged, the low pressure EGR valve 32 is open-loop controlled with a relatively large opening, so that the opening of the high pressure EGR valve 42 and the target value of the EGR rate (target The difference between the EGR) and the actual value (actual EGR) does not show an abnormality, and is almost the same as in the normal state. On the other hand, when determining whether or not there is an abnormality in the high-pressure EGR device 40, the control target of the EGR feedback control is switched. That is, the high pressure EGR valve 42 is open-loop controlled and the low pressure EGR valve 32 is feedback controlled.

  Here, FIG. 5 is a time chart showing changes in the opening degree of the high pressure EGR valve 42, the opening degree of the low pressure EGR valve 32, and the EGR rate. The solid line shows the case where the high pressure EGR valve 42 is feedback controlled and the low pressure EGR valve 32 is open loop controlled, and the low pressure EGR device 30 and the high pressure EGR device 40 are normal. A one-dot chain line indicates a case where the high pressure EGR valve 42 is open-loop controlled and the low pressure EGR valve 32 is feedback controlled, and the low pressure EGR device 30 and the high pressure EGR device 40 are normal. A broken line indicates a case where the high pressure EGR valve 42 is open-loop controlled and the low pressure EGR valve 32 is feedback controlled, and the high pressure EGR passage 41 is clogged.

  The opening degree of the high pressure EGR valve 42 is increased when switching from feedback control to open loop control. That is, a small amount of high-pressure EGR gas is supplied during feedback control, but when an abnormality is determined, the supply amount of high-pressure EGR gas is increased in conjunction with open-loop control of the opening degree of high-pressure EGR valve 42.

Then, when the low pressure EGR valve 32 is switched from the open loop control to the feedback control, when the high pressure EGR passage 41 is not clogged, the opening of the high pressure EGR valve 42 is increased. The opening degree of the low pressure EGR valve 32 is reduced. That is, the opening degree of the low-pressure EGR valve 32 is a case where the low-pressure EGR valve 32 is open-loop controlled, and is smaller than the case where the low-pressure EGR device 30 and the high-pressure EGR device 40 are normal (see the one-dot chain line).

  On the other hand, if the high pressure EGR passage 41 is clogged when the low pressure EGR valve 32 is switched from the open loop control to the feedback control, even if the opening of the high pressure EGR valve 42 is increased, the high pressure EGR valve 42 is increased. Since the gas supply amount does not increase to a desired amount, the opening degree of the low pressure EGR valve 32 is increased (see the broken line). That is, the low pressure EGR gas amount is increased to try to match the EGR rate with the target value. For example, when the opening degree of the low pressure EGR valve 32 is equal to or greater than the threshold value, it is determined that there is an abnormality that the high pressure EGR gas amount decreases. At this time, since the actual value of the EGR rate is adjusted to the target value by increasing the opening degree of the low pressure EGR valve 32, the EGR rate is not different between the normal time and the abnormal time.

  Next, a flow for determining an abnormality in the EGR system according to the present embodiment will be described. FIG. 6 is a flowchart illustrating a flow of determining an abnormality of the EGR system according to the present embodiment. In the flow shown in FIG. 6, it is possible to detect an abnormality in which the flow rate of the EGR gas decreases compared to the normal time. This routine is repeatedly executed by the ECU 20 every predetermined time.

  In step S101, it is determined whether or not the control mode of the EGR system is the MPL mode. For example, the control mode is determined from the operating state of the internal combustion engine 1 and the relationship shown in FIG. In this flow, first, the abnormality of the low pressure EGR device 30 is determined, and then the abnormality of the high pressure EGR device 40 is determined. Therefore, the feedback control of the high pressure EGR valve 42 and the low pressure EGR required for the determination of the low pressure EGR device 30 are performed. It is also determined whether or not the open loop control of the valve 32 is being performed. If an affirmative determination is made in step S101, the process proceeds to step S102, and if a negative determination is made, this routine is terminated.

  In step S102, it is determined whether a precondition for determining an abnormality in the EGR system is satisfied. For example, if EGR feedback control is not performed, it is difficult to determine an abnormality of the EGR system from the opening degree of the low pressure EGR valve 32 or the high pressure EGR valve 42. Therefore, it is assumed that the EGR feedback control can be performed. One of the conditions. Further, since EGR gas is not supplied unless the internal combustion engine 1 is in operation, it is assumed that the internal combustion engine 1 is in operation. Since these are controls performed by the ECU 20, it can be easily determined by the ECU 20.

  In addition, if the sensor used to determine the abnormality of the EGR system is not normal, the abnormality of the EGR system is determined based on incorrect information. Therefore, it is assumed that the sensor is normal. Whether or not the sensor is normal is detected using another known technique. Furthermore, if the intake air amount is too large or too small, the operating state of the internal combustion engine 1 deteriorates and it becomes difficult to determine an abnormality in the EGR system from the opening of the high pressure EGR valve 42. It may be one of the preconditions that it is within the reference range.

  Further, it may be determined whether or not steady operation is being performed. That is, it may be determined whether the engine speed and the engine load of the internal combustion engine 1 are constant. This is because it is difficult to determine an abnormality in the EGR system because the EGR rate and the following various threshold values change when the operation is not steady.

When all these preconditions are satisfied, an affirmative determination is made in step S102. If an affirmative determination is made in step S102, the process proceeds to step S103, and if a negative determination is made, an abnormality in the EGR system cannot be determined, so this routine is temporarily terminated.

  In step S103, the opening degree of the high pressure EGR valve 42 is detected. That is, the value of the opening sensor 44 is read.

  In step S104, it is determined whether or not the opening degree of the high pressure EGR valve 42 is larger than a threshold value. The threshold value is an upper limit value in a range in which the opening degree of the high pressure EGR valve 42 can change when there is no abnormality in the EGR system. If there is no abnormality in the low pressure EGR device 30, the opening degree of the high pressure EGR valve 42 is within a specified range, and if there is an abnormality in the low pressure EGR device 30, the opening degree of the high pressure EGR valve 42 is outside the specified range. That is, the threshold value may be an upper limit value of the opening degree of the high pressure EGR valve 42 that can be said to be normal for the low pressure EGR device 30. Thus, in this step, it is determined whether or not the opening degree of the high pressure EGR valve 42 is in a range where it can be said to be abnormal. Further, since the opening degree of the high pressure EGR valve 42 changes according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load), the threshold value is similarly changed according to the operating state of the internal combustion engine 1. The threshold value is obtained in advance through experiments or the like.

  Alternatively, it may be determined that there is an abnormality in the low-pressure EGR device 30 only when the same state continues for a certain period. That is, in this step, it may be determined whether or not the opening degree of the high-pressure EGR valve 42 is larger than the threshold value and the period in which this state continues is longer than the specified period. This specified period is set as a period required for determining an abnormality of the low-pressure EGR device 30.

  If an affirmative determination is made in step S104, the process proceeds to step S105, where it is determined that there is an abnormality in the low pressure EGR device 30. On the other hand, if a negative determination is made in step S104, the process proceeds to step S106, where it is determined that the low pressure EGR device 30 is normal.

  Next, in step S107, the control target of EGR feedback control is switched. That is, the high pressure EGR valve 42 is open-loop controlled and the low pressure EGR valve 32 is feedback controlled.

  In step S108, the target opening degree (target value of the opening degree) of the high pressure EGR valve 42 is calculated. The target value of the opening degree of the high pressure EGR valve 42 is made larger than that when the high pressure EGR valve 42 is feedback controlled. That is, when feedback control of the high pressure EGR valve 42 is performed when the system is normal, the opening degree of the high pressure EGR valve 42 is set to be larger than a range in which the opening degree can be changed. This target value may be determined according to the engine speed and the engine load. Further, the target value of the opening degree of the high pressure EGR valve 42 may be determined so as to be larger than the opening degree of the low pressure EGR valve 32.

  In step S109, the opening degree of the low pressure EGR valve 32 is adjusted by EGR feedback control.

  In step S110, the opening degree of the low pressure EGR valve 32 is detected. That is, the value of the opening sensor 34 is read.

In step S111, it is determined whether or not the opening degree of the low pressure EGR valve 32 is larger than a threshold value. The threshold value is an upper limit value in a range in which the opening degree of the low pressure EGR valve 32 can change when there is no abnormality in the EGR system. This threshold value is different from the threshold value in step S104. If there is no abnormality in the high-pressure EGR device 40, the opening degree of the low-pressure EGR valve 32 is within the specified range, and if there is an abnormality in the high-pressure EGR device 40, the opening degree of the low-pressure EGR valve 32 is outside the specified range. That is, the threshold value may be an upper limit value of the opening degree of the low pressure EGR valve 32 that can be said to be normal for the high pressure EGR device 40. Thus, in this step, it is determined whether or not the opening degree of the low pressure EGR valve 32 is in a range that can be said to be abnormal. Further, since the opening degree of the low pressure EGR valve 32 changes according to the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load), the threshold value is similarly changed according to the operating state of the internal combustion engine 1. The threshold value is obtained in advance through experiments or the like. Since the opening degree of the high pressure EGR valve 42 is larger than usual, the opening degree of the low pressure EGR valve 32 is smaller than usual if the system is normal. On the other hand, when the opening degree of the low pressure EGR valve 32 becomes larger than normal, it may be determined that the high pressure EGR device 40 is abnormal. That is, the threshold value may be the opening of the low pressure EGR valve 32 when the low pressure EGR valve 32 is open-loop controlled when the system is normal and the high pressure EGR valve 42 is feedback controlled.

  Alternatively, it may be determined that there is an abnormality in the high-pressure EGR device 40 only when the same state continues for a certain period. That is, in this step, it may be determined whether or not the opening degree of the low pressure EGR valve 32 is larger than the threshold value and the period in which this state continues is longer than the specified period. This specified period is set as a period required for determining an abnormality of the high-pressure EGR device 40.

  If an affirmative determination is made in step S111, the process proceeds to step S112, where it is determined that there is an abnormality in the high-pressure EGR device 40. On the other hand, when a negative determination is made in step S111, the process proceeds to step S113, and it is determined that the high-pressure EGR device 40 is normal.

  And in step S114, it switches to normal control. That is, the high pressure EGR valve 42 is feedback-controlled and the low pressure EGR valve 32 is open-loop controlled.

  In the present embodiment, the ECU 20 that processes steps S103 to S113 corresponds to the determination means in the present invention.

  As described above, according to the present embodiment, an abnormality of the EGR system can be determined in each of the HPL mode, the MPL mode, and the LPL mode. That is, even when the EGR gas is supplied from both the high pressure EGR device 40 and the low pressure EGR device 30, both the high pressure EGR device 40 and the low pressure EGR device 30 can be switched by switching the control target of the EGR feedback control. The presence or absence of abnormality can be determined.

  Further, in the MPL mode, since only the control target is switched, EGR gas can be supplied into the cylinder, so that deterioration of the exhaust state can be suppressed.

  In this embodiment, after determining whether or not there is an abnormality in the low pressure EGR device 30, it is determined whether or not there is an abnormality in the high pressure EGR device 40. However, this order may be reversed. In the present embodiment, the abnormality in which the amount of EGR gas is mainly reduced has been described. However, the abnormality can be similarly applied to an abnormality in which the amount of EGR gas is increased.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 4 Exhaust passage 5 Turbocharger 5a Compressor 5b Turbine 6 First intake throttle valve 7 Air flow meter 8 Intercooler 9 Second intake throttle valve 10 Filter 14 Accelerator pedal 15 Accelerator opening sensor 16 Crank position sensor 20 ECU
30 Low pressure EGR device 31 Low pressure EGR passage 32 Low pressure EGR valve 33 EGR cooler 34 Opening sensor 40 High pressure EGR device 41 High pressure EGR passage 42 High pressure EGR valve 44 Opening sensor

Claims (6)

A turbocharger having a turbine in the exhaust passage of the internal combustion engine and a compressor in the intake passage;
A high-pressure EGR device having a high-pressure EGR passage connecting the exhaust passage upstream of the turbine and the intake passage, and a high-pressure EGR valve for adjusting the amount of EGR gas flowing through the high-pressure EGR passage;
A low pressure EGR device having a low pressure EGR passage connecting the exhaust passage downstream of the turbine and the intake passage, and a low pressure EGR valve for adjusting an amount of EGR gas flowing through the low pressure EGR passage;
A high pressure EGR valve opening degree detection device for detecting the opening degree of the high pressure EGR valve;
A low pressure EGR valve opening degree detecting device for detecting an opening degree of the low pressure EGR valve;
In the EGR system abnormality detection device comprising:
When EGR gas is supplied from both the high-pressure EGR device and the low-pressure EGR device, one of the low-pressure EGR valve and the high-pressure EGR valve is controlled in an open loop, while the other EGR valve is The EGR device having the one EGR valve has an abnormality from the opening degree of the other EGR valve when the EGR gas amount in the cylinder is feedback-controlled so that the EGR gas amount in the cylinder goes to the target range of the EGR gas amount Whether or not
Thereafter, when EGR gas is supplied from both the high pressure EGR device and the low pressure EGR device, the other EGR valve is controlled in an open loop, and the one EGR valve is moved to the EGR gas in the cylinder. Determination to determine whether or not there is an abnormality in the other EGR device having the other EGR valve based on the opening degree of the one EGR valve when feedback control is performed so that the amount goes to the target range of the EGR gas amount An abnormality detection device for an EGR system, characterized in that it comprises means.   The determination means determines that the low pressure EGR device is abnormal when the opening of the high pressure EGR valve is out of a specified range, and the high pressure EGR device determines that the opening of the low pressure EGR valve is out of a specified range. The abnormality detection device for an EGR system according to claim 1, wherein it is determined that there is an abnormality.   The determination means is the opening degree of the high pressure EGR valve when the high pressure EGR valve is controlled by open loop control when the EGR gas is supplied from both the high pressure EGR device and the low pressure EGR device. The abnormality detection device for an EGR system according to claim 1 or 2, wherein the high pressure EGR valve is made larger than when feedback control is performed. A high-pressure EGR device having a high-pressure EGR passage connecting an exhaust passage upstream of a turbine of a turbocharger of the internal combustion engine and an intake passage, and a high-pressure EGR valve for adjusting the amount of EGR gas flowing through the high-pressure EGR passage;
A low pressure EGR device having a low pressure EGR passage connecting an exhaust passage downstream of the turbine and an intake passage, and a low pressure EGR valve for adjusting an amount of EGR gas flowing through the low pressure EGR passage;
When EGR gas is supplied from both
The first low-pressure EGR valve or the high-pressure EGR valve is subjected to open-loop control, and the other EGR valve is feedback-controlled so that the EGR gas amount in the cylinder is directed to the target range of the EGR gas amount. Process,
A second step of determining whether there is an abnormality in one of the EGR devices having the one EGR valve, based on the opening degree of the other EGR valve when the first step is being performed;
A third step of performing feedback control so that the EGR gas amount in the cylinder is directed to a target range of the EGR gas amount while performing open-loop control of the other EGR valve;
A fourth step of determining whether or not there is an abnormality in the other EGR device having the other EGR valve from the opening degree of the one EGR valve when the third step is being performed;
An abnormality detection method for an EGR system, comprising:   The abnormality detection method for an EGR system according to claim 4, wherein when the opening degree of the high pressure EGR valve is outside a specified range, it is determined that the low pressure EGR device is abnormal.   5. The abnormality detection method for an EGR system according to claim 4, wherein when the opening of the low pressure EGR valve is outside a specified range, it is determined that the high pressure EGR device is abnormal.

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