KR20050112707A - System and method for on board diagnosis of diesel particulate filter - Google Patents

Abstract

The present invention relates to a system and a method for diagnosing a self-diagnosis of a diesel particulate filter, wherein a first temperature in which an ECU is installed in a can in front of a DPF, respectively, a temperature of an exhaust gas flowing into a diesel particulate filter (DPF) and a temperature of an end of the DPF. It receives and monitors the signal from the sensor and the second temperature sensor installed at the end of the DPF, and monitors the pressure difference between the front and rear of the DPF by receiving the signal from the differential pressure sensor. A self-diagnosis system and method for a diesel particulate filter configured to determine a fault condition and cause of failure.

According to the present invention, it is possible to inform the driver of the state of the DPF through the warning means as well as respond to the OBD law, it is possible to contribute to the improvement of the productability to increase the customer satisfaction.

Description

System and Method for On Board Diagnosis of Diesel Particulate Filter

The present invention relates to a system and a method for diagnosing a self-diagnosis of a diesel particulate filter, wherein a first temperature in which an ECU is installed in a can in front of a DPF, respectively, a temperature of an exhaust gas flowing into a diesel particulate filter (DPF) and a temperature of an end of the DPF. It receives and monitors the signal from the sensor and the second temperature sensor installed at the end of the DPF, and monitors the pressure difference between the front and rear of the DPF by receiving the signal from the differential pressure sensor. A self-diagnosis system and method for a diesel particulate filter configured to determine a fault condition and cause of failure.

Generally, automobiles are classified into passenger cars, buses, and trucks according to their type, but even vehicles of the same type may be used as gasoline vehicles using gasoline, diesel vehicles using diesel, LPG vehicles using LPG, etc., depending on fuel used. Can be classified.

Due to its low fuel consumption and excellent reliability, dual diesel engines have various uses across industries such as automobiles, ships, and general industries, and are capable of high power and high load operation, and demand thereof continues to increase.

In addition, the adoption of diesel engines in the 3L automotive program or supercar project, which is being promoted for low fuel consumption vehicles, is being actualized, and an increase in diesel engine vehicles is expected.

However, in advanced countries, such diesel vehicles occupy a very high proportion of total air pollution and are recognized as a major cause of air pollution, and in order to cope with this, countries are gradually tightening emission regulations of diesel engines.

Air pollution in diesel vehicles is mainly caused by nitrogen oxides (NOx) and particulate matter (PM) called soot.

In the United States, the federal regulations that are in force are expected to be strengthened since 2004. The European Union is also applying or planning to apply EURO III in 2000 and EURO IV in 2005. EURO V is 50% of EURO IV. Regulation of particulate matter is expected to be tightened.

Therefore, the main targets of diesel vehicle exhaust regulation are nitrogen oxides and particulate matters. The countermeasures include the delay of fuel injection timing, the reduction of nitrogen oxide concentration by the exhaust gas recirculation (EGR) device, and the reduction of particulate matters. In order to improve and improve the combustion performance of the engine, the research has been focused on the after-treatment technology.

The specific countermeasures of diesel vehicle exhaust regulation are classified into engine improvement and aftertreatment technology. First, engine improvement technology of diesel vehicle is improved fuel chamber, intake system (turbo charger + intercooler), and fuel injection system ( Electronically controlled high-pressure fuel injection device) and exhaust gas recirculation device are being applied or under development.

In addition, post-treatment technologies developed so far include diesel oxidation catalyst (DOC) for oxidizing and purifying SOF among gaseous HC, CO, and particulate matter, and diesel for physically purifying particulate matter by filtration. Diesel Particulate Filter (DPF) or catalyst coated diesel particulate filter (CPF), DeNOx catalyst that decomposes or reduces nitrogen oxides in an excess oxygen atmosphere, and other DeNOx to diesel oxidation catalyst. 4Way catalyst with added functions.

The diesel particulate filter (DPF) device in the post-treatment technology is a device installed in the exhaust line to collect the non-combusted particulate matter discharged from the diesel engine in the form of a filter to prevent it from being released into the atmosphere. It burns (regenerates) by heating up above the temperature repeatedly.

As such, the diesel particulate filter used for reducing particulate matter undergoes a regeneration process when the particulate matter accumulates to a certain degree. At this time, a high temperature of 550 ° C. or more must be maintained for regeneration.

On the other hand, the DPF is also part of the engine component, it should be determined on the engine board whether the normal operation when driving the vehicle.

Currently, OBD-II (On Board Diagnosis-II) has been enacted in gasoline engines, and cars are operated while checking the engine's normal operation. Cars that do not satisfy the OBD regulations are prohibited from selling.

As the exhaust regulations are being tightened, diesel engines are being tightened as well as gasoline engines. Currently, the regulations do not regulate OBD, but the OBD system of diesel catalysts was announced as soon as possible. .

However, the reality is that there is no OBD system that can cope with OBD regulation for DPF (or CPF: Catalyzed Particulate Filter), which is manufactured and sold by automobile companies, and there is no special research or development.

1 shows a conventional DPF, and as shown, a DOC (Diesel Oxidation Catalyst) 12 is installed in the front of the can 11, and a DPF 13 is installed at the rear of the can 11. As a result, the DOC 12 and the DPF 13 are arranged in series with each other.

Further, a thermocouple detecting the temperature at the front end of the DOC 12 and the front end of the DPF 13, that is, a differential pressure detecting the differential pressure at the front end of the DOC 12 and the rear end of the DPF 13, namely the temperature sensors 14a and 14b. When the sensor 16 is installed, reference numerals 15a and 15b denote pipes for detecting the differential pressure.

Eventually, the ECU 18 monitors the temperature of the exhaust gas discharged from the engine and the temperature after passing the DOC 12 for regeneration of the DPF 13, and the front end of the DOC 12 using the differential pressure sensor 16. The pressure difference behind the DPF 13 is monitored.

However, such a system alone cannot perform the OBD function which can cause various causes of DPF to be identified.

Accordingly, the present invention has been invented in view of the above, and the ECU has a first temperature sensor in which the temperature of the exhaust gas flowing into the diesel particulate filter (DPF) and the temperature of the end of the DPF are respectively installed inside the can in front of the DPF. And receive and monitor the signal from the second temperature sensor installed at the end of the DPF and monitor the pressure difference between the front and rear of the DPF by receiving the signal from the differential pressure sensor. By providing a system and method for self-diagnosis of diesel particulate filter configured to determine the status and cause of failure, it not only responds to the OBD regulations but also informs the driver of the status of DPF through warning means so as to contribute to the improvement of the productability which increases customer satisfaction. The purpose is.

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

Magnetic failure diagnosis system of the diesel particulate filter according to the present invention,

A first temperature sensor installed inside a can in front of the diesel particulate filter and detecting a temperature of the exhaust gas flowing into the diesel particulate filter;

A second temperature sensor installed at an end of the diesel particulate filter and detecting a temperature of the end of the diesel particulate filter;

A differential pressure sensor for detecting a pressure difference between the front and rear of the diesel particulate filter;

Calculate and monitor the temperature difference between the front and the end of the diesel particulate filter and the pressure difference between the front and the end of the diesel particulate filter from the signals of each sensor, and compare the temperature difference and the pressure difference with a preset input map to determine the steady state and ECU for determining fault status and cause of failure;

It includes.

In addition, the magnetic failure diagnosis method of the diesel particulate filter according to the present invention,

Calculating and monitoring a temperature difference between the front and the end of the filter by receiving signals from the first temperature sensor and the second temperature sensor respectively installed at the front and the end of the diesel particulate filter;

Monitoring the pressure difference between the front and rear of the diesel particulate filter by receiving a signal from the differential pressure sensor;

Comparing the temperature difference and the pressure difference with a preset input map to determine a steady state, a failure state, and a cause of failure of the diesel particulate filter;

It includes.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The present invention relates to a system and method for diagnosing a self-diagnosis of a diesel particulate filter (DPF), and in particular, by adding a simple hardware element and adding logic in the ECU, the main characteristic of the OPF function is given to the DPF. There is this.

First, in order to give the DPF an OBD function, the main failure mode of the DPF should be considered.

Since the DPF is not exposed to high temperature and uses a heat-resistant material such as SiC, in particular, the DPF is hardly deteriorated even when exposed to heat for a long time, and thus performance deterioration does not occur due to increased use time.

However, the main causes of failure of the DPF are: ① When uncontrolled burning occurs on the DPF, the temperature rises above 1500 ° C, and the DPF melts. ② The particulate matter is normally regenerated and accumulated on the DPF. Or regeneration by abnormality of other engines (if the pressure difference between DPF is over a certain level, the fuel is oversupplied through post-injection of the engine, and the particulate matter accumulated in the DPF is burned at a temperature where the DPF is not thermally damaged). 3. If the regeneration logic of the engine is normal, but excessive particulate matter is generated during the engine combustion process using poor quality fuel, and the DPF is clogged before the DPF regeneration logic is momentarily activated by the excessive particulate matter. , And ④ When the particulate matter is excessively burned and the DPF is severely melted, the entire DPF is pierced. Can be divided.

2A and 2B show the state of the DPF according to each failure cause. FIG. 2A shows a state in which clogging due to melting occurs in the case of failure cause ①, and FIG. 2B shows a failure cause. It shows the state of ② or ③ and shows the state that PDF is excessively blocked by the accumulation of excessive particulate matter.

In order to determine the cause of the failure of the DPF by the ECU, it is impossible with the existing system. In the existing system, the pressure difference between the front and rear ends of the DPF is measured. Is the DPF blocked due to partial melting caused by it, or is it caused by the fact that the regeneration logic is wrong and only the regeneration logic is accumulated and the regeneration logic is not working (cause of failure ②), or the momentary excessive amount of the particulate material due to the use of poor fuel It is not known whether the cause is caused (failure ③).

In addition, it is not possible to determine whether the entire melting of the DPF has been drilled out due to severe melting.

Therefore, in the present invention, a thermocouple, that is, a temperature sensor is additionally installed at the DPF end of the existing system (in the existing system, the thermocouple is not mounted at the end of the DPF, and there is no need to monitor the DPF temperature). To be diagnosed.

That is, as shown in FIG. 3, the ECU 18 forwards the temperature T1 of the exhaust gas flowing into the front end of the DPF 13 and the temperature T2 of the end of the DPF 13 in front of the DPF 13, respectively. The first temperature sensor 14b installed inside the can 11 and the second temperature sensor 16 installed at the end of the DPF 13 are received and monitored, and in front of the DPF 13 and the DPF 13 ) Back pressure difference (ΔP = ┃P2-P1┃) is monitored by receiving the signal from the differential pressure sensor 16 to determine the normal operating state and failure state of the DPF 13 from the temperature difference and the pressure difference of each part. In other words, the cause of the failure can be determined.

Here, the pressure difference between the front and rear ends of the DPF 13 is obtained from a signal of the existing differential pressure sensor 16 which detects the pressure difference between the position of the can 11 in front of the DOC 12 and the position of the can 11 in the rear of the DPF 13. Monitoring is possible.

In other words, the ECU 18 changes the temperature difference between the front and the end of the DPF 13 (ΔT = # T2-T2) and the pressure difference (ΔP = # P2-P1) between the front and rear of the DPF 13. The state of the DPF can be determined accordingly.

At this time, the state of the DPF can be diagnosed by the temperature difference ΔT and the pressure difference ΔP as shown in the map shown in FIG. 4.

For this purpose, a map for each temperature difference (ΔT) and pressure difference (ΔP) region must be input in the EUC 18. Also, the DPF state is determined for each region according to the map, and a failure cause code is determined according to the determination result. Logic must be configured to give.

In the map of FIG. 4, X1 and X2 are predetermined threshold values such as X1 = 3 kPa and X2 = 4 kPa as specific constant values of pressure, and Y1 and Y2 are specific constant values of temperature, for example Y1 = 100 ° C. , Y2 is a preset threshold such as 300 ° C.

Referring to the map of FIG. 4 in more detail, in the case of the region 1, the DPF is partially drilled due to fine melting of the DPF, but the function of the DPF is almost normal, and there is little pressure difference ΔP. , The temperature difference ΔT is a region where the temperature difference ΔT is present to some extent above the predetermined temperature difference threshold 1 (Y1) (normal operation state).

In addition, in the case of the region (2), the state corresponding to the cause of the failure ④ is a state in which the melting of the DPF is entirely opened, so that the DPF cannot operate normally, and the condition is that the pressure difference ΔP It is an area where there is little below the set pressure difference threshold 1 (X1), and there is almost no temperature difference (ΔT) below the preset temperature difference threshold 1 (X1) (MIL ON).

In the case of the region 3, the temperature of the DPF rises in a state in which the pressure difference ΔP is within a certain range, and the DPF is normally regenerated (normal operation state).

Further, in the case of the region 4, the temperature difference ΔT is under the condition that the temperature difference ΔT is less than the preset temperature difference threshold 2 (Y2) while having the pressure difference ΔP in the preset pressure difference threshold 2 (X2) ( Normal operation).

In the case of the region 5, the pressure difference ΔP is equal to or higher than the pressure difference threshold 2 (X2) and the temperature difference ΔT is equal to or higher than the temperature difference threshold 2 (Y2). Condition in which regeneration or uncontrolled burning has occurred.

At this time, the DPF is a state in which the pores through which the exhaust gas flows are blocked due to melting, and thus a large temperature difference ΔT and a pressure difference ΔP occur (MIL ON).

In addition, in the case of the region 6, when the particulate matter is severely accumulated, the regeneration logic does not work or the particulate matter blocks the DPF before the regeneration logic is operated by using a poor fuel, which causes the failure ②. Or ③.

In this case, the pressure difference ΔP is equal to or higher than the pressure difference threshold 2 (X2), but the temperature difference ΔT is less than the temperature difference threshold 2 (Y2) (MIL ON).

Finally, if no additional thermocouple, i.e. no signal is input from the second temperature sensor 17 at the end of the DPF to the ECU 18 (the signal is disconnected and no temperature value appears), this is uncontrolled after the thermocouple. It is a case where the thermocouple is disconnected due to uncontrolled burning, and in this case, it can be determined whether the region 2 or 5 is the pressure difference ΔP (MIL ON).

Meanwhile, FIG. 5 shows the temperature and the pressure when the DPF is regenerated, and the combustion process is a total of four steps.

First, the L1 section is a transient section, which is a section in which the regeneration condition is reached by increasing the temperature of the exhaust gas.

In addition, the L2 section is an initial regeneration section, which is a start stage of regeneration, that is, a section in which oxygen consumption is not abrupt, and the L3 section is in a normal regeneration state, and the L4 section is a normal state in which the temperature difference ΔT and the pressure difference ΔP are normal. If

Therefore, by simply utilizing the existing DPF system and additionally installing a second temperature sensor at the rear end of the DPF, when monitoring the temperature difference (ΔT) and the pressure difference (ΔP), it is possible to construct an OBD system that can grasp the state of the DPF. .

That is, according to the self-diagnosis system and method according to the present invention, as shown in FIG. 6, the ECU 18 causes the temperature of the exhaust gas in front of the DPF 13 and the end of the DPF 13 to be in front of the DPF. The first temperature sensor 14b installed and the signal of the second temperature sensor 17 installed at the end of the DPF are received and monitored, and the pressure difference between the front of the DPF 13 and the rear of the DPF is signaled by the differential pressure sensor 16. By receiving and monitoring the transmission, it is possible to determine the normal operating state and failure of the DPF 13 through the map from the temperature difference (ΔT) and the pressure difference (ΔP), it is possible to determine the cause of the failure.

Also, the ECU 18 notifies the driver by operating the warning means 19 after determining the failure and the cause of the failure. The ECU 18 turns on a MIL (Malfunction Indication Lamp), which is a warning light, when it is determined that the failure state is caused. The fault information will be saved.

7 is a flowchart illustrating a process in which an ECU determines a normal operating state and each failure state by using a map from a temperature difference ΔT and a pressure difference ΔP.

In this way, the present invention can be configured in a simple configuration, and excellent in reproducibility, and also has a function to monitor the normal operating state of the DPF with temperature in addition to the OBD function, to inform the driver of the state of the DPF in addition to regulatory compliance As a result, it is possible to contribute to the improvement of merchandise that increases customer satisfaction.

As described above, according to the self-diagnosis system and method of the diesel particulate filter according to the present invention, the temperature of the exhaust gas flowing into the diesel particulate filter (DPF) and the temperature of the end of the DPF are respectively inside the can in front of the DPF. It receives and monitors the signals of the first temperature sensor installed in the sensor and the second temperature sensor installed at the end of the DPF, and monitors the pressure difference between the front and rear of the DPF by receiving the signal from the differential pressure sensor. By configuring the DPF to determine the normal operating state, failure state, and cause of failure, it can not only respond to OBD regulations, but also inform the driver of the DPF state through warning means, thereby contributing to the improvement of product quality that increases customer satisfaction.

1 is a perspective view showing a conventional DPF,

2a and 2b is a view showing a DPF state according to the failure cause,

3 is a configuration diagram of a self-diagnosis system according to the present invention;

4 is a view showing a map for implementing a self-diagnosis in the present invention,

5 shows the temperature and pressure when the DPF is regenerated;

6 is a block diagram of a self-diagnosis system according to the present invention;

7 is a flowchart showing a self-diagnosis process according to the present invention.

<Explanation of symbols for the main parts of the drawings>

11: can 12: DOC

13: DPF 14b: first temperature sensor

16: differential pressure sensor 17: second temperature sensor

18 ECU 19 Warning means

Claims (4)

A first temperature sensor installed inside a can in front of the diesel particulate filter and detecting a temperature of the exhaust gas flowing into the diesel particulate filter; A second temperature sensor installed at an end of the diesel particulate filter and detecting a temperature of the end of the diesel particulate filter; A differential pressure sensor for detecting a pressure difference between the front and rear of the diesel particulate filter; Calculate and monitor the temperature difference between the front and the end of the diesel particulate filter and the pressure difference between the front and the end of the diesel particulate filter from the signals of each sensor, and compare the temperature difference and the pressure difference with a preset input map to determine the steady state and ECU for determining fault status and cause of failure; Self-diagnosis system of diesel particulate filter comprising a. The method according to claim 1, Self-diagnosis system of the diesel particulate filter characterized in that it further comprises a warning means for operating by the control signal of the ECU to inform the failure state and cause. Calculating and monitoring a temperature difference between the front and the end of the filter by receiving signals from the first temperature sensor and the second temperature sensor respectively installed at the front and the end of the diesel particulate filter; Monitoring the pressure difference between the front and rear of the diesel particulate filter by receiving a signal from the differential pressure sensor; Comparing the temperature difference and the pressure difference with a preset input map to determine a steady state, a failure state, and a cause of failure of the diesel particulate filter; Self failure diagnosis method of the diesel particulate filter comprising a. The method according to claim 3, And outputting a control signal according to the determination result of the determining step to operate a warning means for informing the failure state and cause.