JP6784579B2 - Failure diagnosis device and failure diagnosis method - Google Patents

Description

The present invention relates to a failure diagnosis device and a failure diagnosis method for diagnosing a failure of an EGR valve.

Conventionally, a diesel engine is equipped with an EGR (Exhaust Gas Recirculation) pipe that introduces a part of the exhaust gas from the exhaust pipe to the intake pipe in order to reduce NOx contained in the exhaust gas. The EGR pipe is provided with an EGR valve, and the flow rate of the EGR gas introduced into the intake pipe is adjusted by controlling the opening degree of the EGR valve.

For example, Patent Document 1 discloses an apparatus for diagnosing a failure of an EGR valve. This device diagnoses an EGR valve failure based on the discrepancy between the flow rate of EGR gas actually flowing through the EGR tube and the estimated flow rate of EGR gas calculated by a formula based on Bernoulli's theorem.

Japanese Unexamined Patent Publication No. 2016-37932

However, since the calculation formula of Patent Document 1 is insufficient in the estimation accuracy of the flow rate, there is a possibility that a highly accurate failure diagnosis cannot be performed.

An object of the present invention is to provide a failure diagnosis device and a failure diagnosis method capable of accurately diagnosing a failure of an EGR valve.

The failure diagnosis device of the present invention is a failure diagnosis device that diagnoses a failure of an EGR valve provided in an EGR pipe that introduces EGR gas from an exhaust pipe to an intake pipe, and is a flow rate of EGR gas that actually flows through the EGR pipe. Based on the difference between the first flow rate and the second flow rate, which is the flow rate of the EGR gas estimated to flow through the EGR tube, and the difference between the first flow rate and the second flow rate. A diagnostic unit for diagnosing whether or not the EGR valve is out of order is provided, and the second flow rate is the pressure upstream of the EGR valve, the pressure downstream of the EGR valve, and the temperature upstream of the EGR valve. The effective opening area is calculated based on the preset specific heat ratio and the effective opening area of the EGR valve, and the effective opening area is the opening command value for the EGR valve, the pressure upstream of the EGR valve, and the EGR. opening area der of the EGR valve corresponding to the differential pressure or pressure ratio between the pressure downstream of the valve is, the diagnostic unit, the opening degree of the EGR valve, and the differential pressure or the pressure ratio, advance When the specified diagnosis non-execution condition is met, it is not diagnosed whether or not the EGR valve is out of order, and the diagnosis non-execution condition is the opening degree of the EGR valve and the differential pressure or the pressure ratio. The opening degree of the EGR valve and the differential pressure or the pressure ratio, wherein the standard deviation obtained by normalizing the flow rate of the EGR gas measured in advance according to the above is a predetermined value or more .

The failure diagnosis method of the present invention is a failure diagnosis method for diagnosing a failure of an EGR valve provided in an EGR pipe connecting an intake pipe and an exhaust pipe, and is a flow rate of EGR gas actually flowing through the EGR pipe. The first flow rate and the second flow rate, which is the flow rate of the EGR gas estimated to flow through the EGR pipe, are calculated, and the EGR valve fails based on the difference between the first flow rate and the second flow rate. The second flow rate is the pressure upstream of the EGR valve, the pressure downstream of the EGR valve, the temperature upstream of the EGR valve, the preset specific heat ratio, and the above. Calculated based on the effective opening area of the EGR valve, the effective opening area is the differential pressure or pressure between the opening command value for the EGR valve and the pressure upstream of the EGR valve and the pressure downstream of the EGR valve. Ri opening area der of the EGR valve corresponding to the ratio, the opening degree of the EGR valve, when said differential pressure or the pressure ratio, corresponds to a predetermined diagnostic non-execution condition, the EGR valve Without diagnosing whether or not there is a failure, the diagnosis non-execution condition normalizes the flow rate of the EGR gas measured in advance according to the opening degree of the EGR valve and the differential pressure or the pressure ratio. The opening degree of the EGR valve and the differential pressure or the pressure ratio at which the standard deviation obtained is equal to or greater than a predetermined value .

According to the present invention, it is possible to accurately diagnose a failure of the EGR valve.

The figure which shows the structural example of the failure diagnosis apparatus and engine which concerns on Embodiment 1 and 2 of this invention. The figure which shows the operation example of the failure diagnosis apparatus which concerns on Embodiment 1 of this invention. The figure explaining an example of the diagnosis non-execution condition which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>
The configuration of the failure diagnosis device and the engine according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a configuration example of a failure diagnosis device 1 and an engine 2 according to the present embodiment.

First, the engine 2 will be described.

The engine 2 is a diesel engine having four cylinders 3. The engine 2 may be a multi-cylinder engine other than the 4-cylinder engine or a single-cylinder engine.

The injector (also referred to as a fuel injection valve) 4 is provided corresponding to each cylinder 3, and injects fuel supplied from the common rail 5 into the combustion chamber of each cylinder 3.

The upstream end of the intake pipe 7 is connected to the air filter 6. The downstream end of the intake pipe 7 is connected to the inlet of the compressor 9 of the turbocharger 8. A high pressure side intake pipe 11 is connected to the outlet of the compressor 9. The high pressure side intake pipe 11 is connected to the downstream end of the EGR pipe 15. Further, the high pressure side intake pipe 11 is connected to the intake manifold 12.

With such a configuration, the air from the atmosphere taken in from the air filter 6 (hereinafter referred to as intake air) is compressed by the compressor 9 through the intake pipe 7 to become high-pressure intake air. Then, the intake air flowing from the compressor 9 to the high pressure side intake pipe 11 is mixed with the EGR gas from the EGR pipe 15. This air-fuel mixture is hereinafter referred to as "working gas". The working gas flows into the combustion chamber of each cylinder 3 via the intake manifold 12.

A high-pressure side exhaust pipe 14 is connected to the exhaust manifold 13. An EGR pipe 15 is connected to the high pressure side intake pipe 14. The EGR pipe 15 is provided with an EGR cooler 16 for cooling the EGR gas and an EGR valve 17 for adjusting the flow rate of the EGR gas flowing into the high pressure side intake pipe 11. In this embodiment, the “flow rate” means a mass flow rate.

Further, the inlet of the turbine 10 of the turbocharger 8 is connected to the high-pressure side exhaust pipe 14. An exhaust pipe 18 is connected to the outlet of the turbine 10. An exhaust gas purification device 19 is installed in the exhaust pipe 18.

With such a configuration, the exhaust gas from the combustion chamber of each cylinder 3 flows from the exhaust manifold 13 into the high-pressure side exhaust pipe 14. A part of this exhaust gas (EGR gas) flows into the high-pressure side intake pipe 11 via the EGR pipe 15. On the other hand, the exhaust gas that has flowed into the turbine 10 flows into the exhaust gas purification device 19 via the exhaust pipe 18. The exhaust gas purified by the exhaust gas purification device 19 is discharged to the outside of the vehicle.

The intake pipe 7 is provided with an air flow sensor 20 that detects the flow rate of the intake air. Further, the high pressure side intake pipe 11 is provided with a pressure sensor 21 for detecting the pressure of the working gas and a temperature sensor 22 for detecting the temperature of the working gas. The pressure detected by the pressure sensor 21 corresponds to "pressure downstream of the EGR valve 17".

The installation location of the air flow sensor 20, the pressure sensor 21, and the temperature sensor 22 is not limited to the installation location shown in FIG. For example, the air flow sensor 20, the pressure sensor 21, and the temperature sensor 22 may be provided on the intake manifold 12.

The EGR tube 15 is provided with a pressure sensor 23 for detecting the pressure of the EGR gas flowing upstream of the EGR valve 17 and a temperature sensor 24 for detecting the temperature of the EGR gas flowing upstream of the EGR valve 17. The pressure detected by the pressure sensor 23 corresponds to "the pressure upstream of the EGR valve 17". The temperature detected by the temperature sensor 24 corresponds to "the temperature upstream of the EGR valve 17".

The detection results of the air flow sensor 20, the pressure sensors 21, 23, and the temperature sensors 22 and 24 are output to the failure diagnosis device 1.

The engine 2 has been described above.

Next, the failure diagnosis device 1 will be described.

The failure diagnosis device 1 has a calculation unit 100 and a diagnosis unit 101. The failure diagnosis device 1 has, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) in which a control program is stored, a working memory such as a RAM (Random Access Memory), and an input / output port. .. Each function of the calculation unit 100 and the diagnosis unit 101 is realized by the CPU executing the control program.

The calculation unit 100 calculates the flow rate of the EGR gas actually flowing through the EGR tube 15 (hereinafter referred to as the first flow rate) based on the detection results of the air flow sensor 20, the pressure sensor 21, and the temperature sensor 22. A specific example of this calculation process will be described later.

Further, the calculation unit 100 determines the flow rate of the EGR gas (hereinafter referred to as the second flow rate) estimated to flow through the EGR tube 15 based on the detection results of the pressure sensor 21, the pressure sensor 23, and the temperature sensor 24. calculate. A specific example of this calculation process will be described later.

Further, the calculation unit 100 calculates the difference between the first flow rate and the second flow rate.

The diagnosis unit 101 determines whether or not the difference between the first flow rate and the second flow rate (hereinafter referred to as a flow rate difference) is equal to or greater than a preset threshold value. This threshold value may be, for example, a specified value specified in a predetermined law, or may be a value set by a manufacturer or the like based on the specified value.

When the flow rate difference is equal to or greater than the threshold value, the diagnosis unit 101 diagnoses that the EGR valve 17 is out of order. On the other hand, when the flow rate difference is less than the threshold value, the diagnosis unit 101 diagnoses that the EGR valve 17 has not failed.

When the diagnosis unit 101 diagnoses that the EGR valve 17 is out of order, the diagnosis unit 101 controls a predetermined device (for example, a lamp, a display, a speaker, etc.) so as to notify the user (for example, a vehicle occupant) of that fact. You may.

The configurations of the failure diagnosis device 1 and the engine 2 have been described above.

Next, the operation of the failure diagnosis device 1 according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing an operation example of the failure diagnosis device 1 according to the present embodiment.

First, the calculation unit 100 calculates the first flow rate (step S101).

For example, first, the calculation unit 100 calculates the flow rate Gwg of the working gas by using the equation of state P × V = Gwg × R × T. In this equation of state, P is the pressure of the working gas (detection result of the pressure sensor 21), V is a value based on the product of the engine speed and the exhaust amount of the engine 2, R is the gas constant, and T is the temperature of the working gas. (Detection result of the temperature sensor 22).

Next, the calculation unit 100 subtracts the flow rate of the intake air detected by the air flow sensor 20 from the flow rate Gwg of the working gas. As a result, the first flow rate is calculated.

Next, the calculation unit 100 calculates the second flow rate (step S102).

For example, the calculation unit 100 calculates the second flow rate m based on the following calculation formula (1). In the calculation formula (1), A is the effective opening area, p ₂ is the pressure downstream of the EGR valve 17 (detection result of the pressure sensor 21), and p ₃ is the pressure upstream of the EGR valve 17 (pressure sensor 23). (Detection result), T ₃ is the temperature upstream of the EGR valve 17 (detection result of the temperature sensor 24), κ is a preset specific heat ratio, and t is time. The effective opening area is the differential pressure or pressure ratio between the opening command value for the EGR valve 17 (in other words, the opening of the EGR valve 17) and the pressure upstream of the EGR valve 17 and the pressure downstream of the EGR valve 17. It is the opening area of the EGR valve 17 corresponding to.

Next, the calculation unit 100 calculates the flow rate difference based on the first flow rate and the second flow rate (step S103).

Next, the diagnostic unit 101 determines whether or not the calculated flow rate difference is equal to or greater than a preset threshold value (step S104).

When the flow rate difference is equal to or greater than the threshold value (step S104: YES), the diagnostic unit 101 determines that the EGR valve 17 is out of order (step S105).

On the other hand, when the flow rate difference is not equal to or greater than the threshold value (step S104: NO), the diagnostic unit 101 determines that the EGR valve 17 has not failed (step S106).

The operation of the failure diagnosis device 1 has been described above.

The failure diagnosis device 1 of the present embodiment is a differential pressure or pressure between the opening command value (opening of the EGR valve 17) for the EGR valve 17 and the pressure upstream of the EGR valve 17 and the pressure downstream of the EGR valve 17. The second flow rate is calculated using the effective opening area corresponding to the ratio. On the other hand, for example, in Patent Document 1, the second flow rate is calculated using the opening area (hereinafter, referred to as a geometric opening area) corresponding only to the opening command position. However, it is known that the area (effective opening area) through which the EGR gas actually flows changes according to the differential pressure or the pressure ratio between the pressure on the upstream side and the pressure on the downstream side of the EGR valve. Therefore, the second flow rate calculated using the geometric opening area may lack accuracy. Since the failure diagnosis device 1 of the present embodiment calculates the second flow rate using the effective opening area, the second flow rate can be calculated with high accuracy. Therefore, the failure diagnosis device 1 can accurately diagnose the failure of the EGR valve.

<Embodiment 2>
The second flow rate calculated by the above formula (1) is the opening degree of the EGR valve 17 (hereinafter referred to as the valve opening degree) and the difference between the pressure upstream of the EGR valve 17 and the pressure downstream of the EGR valve 17. The estimation accuracy may vary depending on the pressure or pressure ratio (hereinafter, simply referred to as differential pressure or pressure ratio).

Therefore, in the present embodiment, the valve opening and the differential pressure or the pressure ratio, which may cause variations in the estimation accuracy of the second flow rate, are set in advance as the diagnosis non-execution conditions, and the valve is opened before the diagnosis is executed. If the degree and the differential pressure or pressure ratio correspond to the non-diagnosis conditions, the failure should not be diagnosed.

A specific example will be described below. Since the configurations of the failure diagnosis device 1 and the engine 2 of the present embodiment are the same as those of the first embodiment, the description here will be omitted, and the operation of the failure diagnosis device 1 will be described below. Further, although the differential pressure will be described below as an example, the pressure ratio may be used.

For example, a manufacturer or the like inputs steady-state operation test data into the failure diagnosis device 1. This steady-state operation test data includes data indicating a valve opening degree measured in advance and a flow rate of EGR gas for each differential pressure.

Next, the calculation unit 100 of the failure diagnosis device 1 normalizes the flow rate of the EGR gas included in the steady operation test data and calculates the standard deviation.

Here, an example in which the calculated standard deviation is plotted for each valve opening degree and differential pressure is shown in FIGS. 3 (a) and 3 (b).

Next, the calculation unit 100 specifies a standard deviation of a predetermined value (for example, 0.5) or more set in advance from the plurality of standard deviations. The standard deviation of the predetermined value or more is, for example, the standard deviation surrounded by the ellipse X in FIG. 3A.

Next, the calculation unit 100 determines the valve opening degree and the differential pressure corresponding to the standard deviation of a predetermined value or more as the diagnosis non-execution condition. The valve opening degree and differential pressure determined under the non-diagnosis execution condition are, for example, the valve opening degree and differential pressure corresponding to the region Y in FIGS. 3A and 3B. The valve opening degree and the differential pressure can be said to be the valve opening degree and the differential pressure in which the estimation accuracy of the second flow rate may vary when the second flow rate is calculated based on them.

For example, the diagnosis non-execution condition corresponds to either the case where the valve opening is less than 10%, or the case where the valve opening is 10% or more and less than 30% and the differential pressure is 20% or more and less than 40%. , Is the content.

Next, the calculation unit 100 stores information indicating the diagnosis non-execution condition (hereinafter referred to as condition information) in a predetermined storage device. This storage device is a device that can be accessed by the diagnosis unit 101 of the failure diagnosis device 1, and may be provided inside the failure diagnosis device 1 or outside the failure diagnosis device 1.

Then, for example, the diagnosis unit 101 reads the condition information from the storage device before performing the determination process of step S104 shown in FIG. 2, and the current valve opening degree and the differential pressure are shown in the condition information. Determine if the condition is met.

When the current valve opening degree and the differential pressure do not correspond to the diagnosis non-execution condition, the diagnosis unit 101 performs the processes after step S104. On the other hand, when the current valve opening degree and the differential pressure correspond to the diagnosis non-execution condition, the diagnosis unit 101 does not perform the processing after step S104.

The diagnostic unit 101 reads condition information from the storage device before executing the process of step S101 shown in FIG. 2, and the current valve opening degree and differential pressure correspond to the diagnosis non-execution condition shown in the condition information. You may decide whether or not to do so. Then, when the current valve opening and the differential pressure do not correspond to the diagnosis non-execution condition, the processing after step S101 is performed, and when the current valve opening and the differential pressure correspond to the diagnosis non-execution condition, the step The processing after S101 may not be performed.

Further, in the above description, the case where the failure diagnosis device 1 determines the diagnosis non-execution condition has been described as an example, but the diagnosis non-execution condition may be determined by a computer other than the failure diagnosis device 1.

As described in detail, in the failure diagnosis device 1 of the present embodiment, the valve opening degree and the differential pressure before the execution of the diagnosis are the conditions for non-diagnosis (the valve opening degree and the difference in which the estimation accuracy of the second flow rate may vary). In the case of pressure), the failure diagnosis of the EGR valve 17 is not performed, so that the accuracy of the failure diagnosis can be further improved.

Although the first and second embodiments of the present invention have been described above, the present invention is not limited to the first and second embodiments, and is appropriately modified and implemented without departing from the spirit of the present invention. It is possible.

For example, in the first and second embodiments, the case where the engine 2 includes the turbocharger 8 has been described as an example, but the engine 2 does not have to include the turbocharger 8.

<Summary of this disclosure>
The failure diagnosis device of the present invention is a failure diagnosis device that diagnoses a failure of an EGR valve provided in an EGR pipe that introduces EGR gas from an exhaust pipe to an intake pipe, and is a flow rate of EGR gas that actually flows through the EGR pipe. Based on the difference between the first flow rate and the second flow rate, which is the flow rate of the EGR gas estimated to flow through the EGR tube, and the difference between the first flow rate and the second flow rate. A diagnostic unit for diagnosing whether or not the EGR valve is out of order is provided, and the second flow rate is the pressure upstream of the EGR valve, the pressure downstream of the EGR valve, and the temperature upstream of the EGR valve. The effective opening area is calculated based on the preset specific heat ratio and the effective opening area of the EGR valve, and the effective opening area is the opening command value for the EGR valve, the pressure upstream of the EGR valve, and the EGR. The opening area of the EGR valve corresponding to the differential pressure or pressure ratio with the pressure downstream of the valve.

ｍ：前記第２流量
Ａ：前記有効開口面積
ｐ_２：前記ＥＧＲバルブの下流の圧力
ｐ_３：前記ＥＧＲバルブの上流の圧力
Ｔ_３：前記ＥＧＲバルブの上流の温度
κ：前記比熱比
ｔ：時間 In the failure diagnosis device, the calculation unit may calculate the second flow rate based on the following calculation formula (1).

m: The second flow rate A: The effective opening area p ₂ : The pressure downstream of the EGR valve p ₃ : The pressure upstream of the EGR valve T ₃ : The temperature upstream of the EGR valve κ: The specific heat ratio t: Time

Further, in the failure diagnosis device, when the opening degree of the EGR valve and the differential pressure or the pressure ratio correspond to a predetermined diagnosis non-execution condition, the diagnosis unit fails the EGR valve. The diagnosis non-execution condition is obtained by normalizing the flow rate of the EGR gas measured in advance according to the opening degree of the EGR valve and the differential pressure or the pressure ratio without performing a diagnosis as to whether or not the EGR valve is used. The opening degree of the EGR valve and the differential pressure or the pressure ratio may be such that the obtained standard deviation becomes a predetermined value or more.

The failure diagnosis method of the present invention is a failure diagnosis method for diagnosing a failure of an EGR valve provided in an EGR pipe connecting an intake pipe and an exhaust pipe, and is a flow rate of EGR gas actually flowing through the EGR pipe. The first flow rate and the second flow rate, which is the flow rate of the EGR gas estimated to flow through the EGR pipe, are calculated, and the EGR valve fails based on the difference between the first flow rate and the second flow rate. The second flow rate is the pressure upstream of the EGR valve, the pressure downstream of the EGR valve, the temperature upstream of the EGR valve, the preset specific heat ratio, and the above. Calculated based on the effective opening area of the EGR valve, the effective opening area is the differential pressure or pressure between the opening command value for the EGR valve and the pressure upstream of the EGR valve and the pressure downstream of the EGR valve. The opening area of the EGR valve corresponding to the ratio.

The present invention can be applied to a failure diagnosis device and a failure diagnosis method for diagnosing a failure of an EGR valve.

1 Failure diagnosis device 2 Engine 3 Cylinder 4 Injector 5 Common rail 6 Air filter 7 Intake pipe 8 Turbocharger 9 Compressor 10 Turbine 11 High pressure side intake pipe 12 Intake manifold 13 Exhaust manifold 14 High pressure side exhaust pipe 15 EGR pipe 16 EGR cooler 17 EGR valve 18 Exhaust pipe 19 Exhaust gas purification device 20 Air flow sensor 21, 23 Pressure sensor 22, 24 Temperature sensor 100 Calculation unit 101 Diagnostic unit

Claims (3)

It is a failure diagnosis device that diagnoses the failure of the EGR valve provided in the EGR pipe that introduces EGR gas from the exhaust pipe to the intake pipe.
A calculation unit that calculates a first flow rate, which is the flow rate of EGR gas that actually flows through the EGR pipe, and a second flow rate, which is the flow rate of EGR gas that is estimated to flow through the EGR pipe.
A diagnostic unit for diagnosing whether or not the EGR valve has failed based on the difference between the first flow rate and the second flow rate is provided.
The second flow rate is
Calculated based on the pressure upstream of the EGR valve, the pressure downstream of the EGR valve, the temperature upstream of the EGR valve, the preset specific heat ratio, and the effective opening area of the EGR valve.
The effective opening area is
And opening command value for the EGR valve, Ri opening area der of the EGR valve corresponding to the differential pressure or pressure ratio between the pressure downstream of the upstream pressure and the EGR valve of the EGR valve,
The diagnostic unit
When the opening degree of the EGR valve and the differential pressure or the pressure ratio correspond to a predetermined diagnosis non-execution condition, it is not diagnosed whether or not the EGR valve is out of order.
The diagnosis non-execution condition is
The opening degree of the EGR valve in which the standard deviation obtained by normalizing the opening degree of the EGR valve and the flow rate of the EGR gas measured in advance according to the differential pressure or the pressure ratio becomes a predetermined value or more. And the differential pressure or the pressure ratio,
Failure diagnostic device. The calculation unit calculates the second flow rate based on the following calculation formula (1).
The failure diagnosis device according to claim 1.

m: The second flow rate A: The effective opening area p ₂ : The pressure downstream of the EGR valve p ₃ : The pressure upstream of the EGR valve T ₃ : The temperature upstream of the EGR valve κ: The specific heat ratio t: Time It is a failure diagnosis method for diagnosing a failure of the EGR valve provided in the EGR pipe connecting the intake pipe and the exhaust pipe.
The first flow rate, which is the flow rate of the EGR gas actually flowing through the EGR pipe, and the second flow rate, which is the flow rate of the EGR gas estimated to flow through the EGR pipe, are calculated.
Based on the difference between the first flow rate and the second flow rate, it is diagnosed whether or not the EGR valve is out of order.
The second flow rate is
Calculated based on the pressure upstream of the EGR valve, the pressure downstream of the EGR valve, the temperature upstream of the EGR valve, the preset specific heat ratio, and the effective opening area of the EGR valve.
The effective opening area is
And opening command value for the EGR valve, Ri opening area der of the EGR valve corresponding to the differential pressure or pressure ratio between the pressure downstream of the upstream pressure and the EGR valve of the EGR valve,
When the opening degree of the EGR valve and the differential pressure or the pressure ratio correspond to a predetermined diagnosis non-execution condition, it is not diagnosed whether or not the EGR valve is out of order.
The diagnosis non-execution condition is
The opening degree of the EGR valve in which the standard deviation obtained by normalizing the opening degree of the EGR valve and the flow rate of the EGR gas measured in advance according to the differential pressure or the pressure ratio becomes a predetermined value or more. And the differential pressure or the pressure ratio,
Failure diagnosis method.

Images