KR101551083B1 - Mehtod for monitoring fail of DPF system - Google Patents

Abstract

The present invention relates to a method for diagnosing malfunction of a DPF system for a vehicle and, more specifically, to a method of diagnosing malfunction of a DPF system for a vehicle to accurately diagnose malfunction of a DPF system using a PM sensor. That is, the present invention provides a method for diagnosing malfunction of a DFP system for a vehicle to accurately diagnose malfunction of a DFP by compensating for a value measured by a PM sensor in consideration of engine operation conditions while measuring the amount of PMs discharged as an exhaust gas by the PM sensor, obtaining an average value during (t, t+a) of F(t) which is the specific time of a time function presented by the compensated PM value, obtaining a distribution value by using the obtained average value, and then diagnosing malfunction of a DPF by comparing the distribution value with a distribution value which is in a reference range pre-obtained through a test.

Description

[0001] The present invention relates to a method for diagnosing faults in a vehicle,

The present invention relates to a fault diagnosis method for a DPF system for an automobile, and more particularly, to a fault diagnosis method for a DPF system for a vehicle, which can accurately diagnose a fault of the DPF system using a PM sensor.

Nitrogen oxides (NOx) and particulate matter (PM) contained in the exhaust gas of diesel vehicles are recognized as the main cause of air pollution.

Diesel Oxidize Catalyst (DOC) was initially applied to meet the exhaust gas regulations for diesel engines. However, as regulations have been gradually strengthened, diesel particulate matter filter (DPF) has been additionally applied .

1, a general PM (particulate matter) purifier of a commercial engine includes a DOC 10 that functions to raise the temperature of the exhaust gas, a DPF 12 that collects and burns PM, A temperature sensor 16 on the inlet side of the DOC and an outlet side temperature sensor 17 on the outlet side of the DPF 12, a differential pressure sensor 13 for measuring the front and rear end pressures of the DPF 12, And an HCI 15 which is connected to the network.

The DPF collects PM in the exhaust gas, and when the exhaust gas temperature exceeds a predetermined amount, it regenerates the exhaust gas by forcibly raising the exhaust gas temperature.

At this time, post injection of common rail is used to raise the temperature of the exhaust gas for regenerating the DPF. However, in order to overcome the problem of insufficient temperature rise of the exhaust gas in the commercial engine, a separate engine called a HCI (Hydrocarbon Injection) Fuel injection system.

The HCI dosing module injects the fuel supplied from the fuel tank through the dosing valve and injects the fuel to the front side of the DOC 10 to increase the temperature of the exhaust gas to maximize the regeneration performance of the DPF.

Such a DPF system requires that the amount of PM (particulate matter) discharged from the vehicle be maintained at about 25 mg / kWh or less in order to satisfy exhaustion regulation regulations (for example, EURO6 OBD regulation) If there is a problem that the emission amount of particulate matter exceeds the regulation value, there is a regulation to build a fault diagnosis system that notifies the driver by lighting the warning lamp.

Therefore, a method for diagnosing a failure of a DPF system to satisfy a new exhaust gas regulation is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an exhaust gas purifying apparatus, The exhaust gas temperature, the exhaust gas flow, and the soot estimation value calculated in the ECU's DPF control model can be used to easily diagnose the failure of the DPF system. The present invention provides a method for diagnosing faults in a vehicle DPF system.

According to an aspect of the present invention, there is provided a method for controlling an internal combustion engine comprising the steps of: measuring a PM amount in a PM sensor mounted at a rear end of a DPF; Compensating the measured value measured by the PM sensor in consideration of an engine driving condition; A DPF system state check step of checking a current state of the DPF system; If the DPF system is in a normal state, the start of the fault diagnosis of the DPF system is determined to determine a start time t for fault diagnosis; Determining a calculation end point (t + a) for an average value and a variance value based on a channel state of the DPF; Obtaining a mean value during a specific time (t, t + a) for diagnosing the failure of the PM value measured at the downstream of the DPF, and obtaining a variance value using the calculated average value; Diagnosing the abnormality of the DPF system by comparing the obtained dispersion value with the dispersion value obtained through the test; The present invention provides a method for diagnosing a failure of a DPF system for an automobile.

Preferably, the method further comprises filtering the signal measured by the PM sensor by a Min-max filter to reduce a measurement error.

Particularly, during the DPF system status check step, 1) the DPF is being regenerated, or 2) one of the DOC input side and output side temperature sensor, differential pressure sensor, and HCI which controls the DPF system fails, and 3) (4) When the internal soot accumulation amount of the DPF is less than or equal to the minimum reference value, the diagnosis of the DPF system is not performed.

The starting point (t) for the fault diagnosis is determined when the compensated PM measurement value is smaller than the variance value calculated during the set time.

Also, in the step of determining the calculation end point (t + a), the a time may be calculated by multiplying the Soot Percentage value of the DPF by the value of the channel length reduced by the ash deposition of the DPF, And a value of < / RTI >

In particular, in the step of diagnosing the abnormality of the DPF system, if the dispersion value measured during (t + a) is less than the minimum reference dispersion value obtained in advance through the test, The DPF is diagnosed to be cracked when the measured dispersion value is larger than the maximum reference dispersion value obtained in advance through the test.

Through the above-mentioned means for solving the problems, the present invention provides the following effects.

First, the PM sensor is installed at the rear end of the DPF to measure the amount of PM discharged from the exhaust gas. At the same time, the value measured by the PM sensor is compensated in consideration of the engine driving conditions, and the compensated PM value is expressed as a function of time (t, t + a) at the specific time (t, t + a) of the DPF is calculated, the variance value is obtained by using the calculated average value, Can be diagnosed.

Secondly, it is possible to satisfy the new exhaust gas regulations by making an accurate diagnosis of the abnormality of the DPF and warning the driver.

1 is a system configuration diagram for a fault diagnosis method of a DPF system for a vehicle according to the present invention;
FIG. 2 and FIG. 3 are graphs showing the principle of the fault diagnosis method for a vehicle DPF system according to the present invention,
FIG. 4 is a flowchart illustrating a method for diagnosing a failure of a DPF system for a vehicle according to the present invention. FIG.

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

1, the DPF system includes an HCI 15 that injects fuel to an exhaust pipe 14, a DOC 10 that serves to raise the temperature of the exhaust gas, a DPF 12 that collects and burns PM A DOC inlet side temperature sensor 16 and an outlet side temperature sensor 17 and a differential pressure sensor 13 for measuring the front and rear end pressures of the DPF 12 and the like.

In order to diagnose a fault diagnosis of a DPF system for a vehicle according to the present invention, a PM sensor 18 is mounted at the rear end of a DPF 12 for collecting and burning PM.

First, the concept and principle of the DPF system failure diagnosis method will be described in order to facilitate understanding of the present invention.

When the measured value of the PM sensor 18 is compensated in consideration of the engine driving condition and the compensated PM value is denoted by F and the value of F is expressed as a function of time, It can be expressed as F (t) as shown in the graph.

If a problem such as micro cracks occurs in the DPF, the PM value F (t) measured at the rear end of the DPF is changed to F '(t) as indicated by a bold solid line in the graph of FIG.

The reason for changing to F '(t) is that since the exhaust gas flow rate increases in the acceleration mode, the amount of exhaust gas passing through the crack portion of the DPF increases and the measured PM amount increases. In the deceleration mode, There is no big change compared to the normal condition due to the decrease in back pressure.

(T, t + a) for the diagnosis of F (t) by accurately diagnosing the abnormality of the DPF system by quantitatively determining the difference between F (t) and F The DPF can be diagnosed as having an abnormality by comparing the measured value with the value obtained from the test.

Hereinafter, a fault diagnosis method for a vehicle DPF system according to the present invention will be described in detail.

FIG. 4 is a flowchart illustrating a method for diagnosing a failure of a DPF system for a vehicle according to the present invention.

First, the step of measuring the PM amount in the PM sensor 18 mounted at the rear end of the DPF 12 is preceded (S101), and the measured signal is filtered by the Min-max filter to reduce the measurement error (S102 ).

Next, the PM measurement value is compensated in consideration of the measured value measured by the PM sensor, that is, the engine driving condition and the running condition rather than the raw data (S103).

The compensation of the PM measurement value in consideration of the engine driving condition and the running condition means that the PM measurement value is compensated for in each zone by dividing the PM measurement value into five zones according to the amount of engine fuel and the number of revolutions, If the compensation value is 0.8 when it corresponds to the load driving zone, the PM measurement value is multiplied by 0.8, and the multiplied value is used as the cumulative PM value.

At this time, before the actual diagnosis process for the DPF is performed using the compensated PM measurement value, a diagnosis enable condition is checked to determine whether to start the diagnosis.

For this purpose, a process of checking the status of the DPF system (System Status Check) (S104) is performed before the actual diagnosis process for the DPF proceeds.

That is, the status check of the DPF system is to check whether or not the DPF system is regenerated and whether the DPF system configuration is operating normally, thereby determining whether or not to start the diagnosis of the DPF system. .

More specifically, when 1) the DPF is being regenerated, 2) one of the DOC input side and output side temperature sensor, the differential pressure sensor and the HCI which controls the DPF system fails, and 3) the PM sensor itself is defective, 4) If the internal soot accumulation amount of the DPF, that is, the PM accumulation amount is equal to or less than the minimum standard value (DPF_Monitor_Soot_min_AVP) or is equal to or greater than the maximum standard value (DPF_Monitor_soot_max_apv), the DPF system is not diagnosed.

Of course, as a result of the state check of the DPF system, the start of the trouble diagnosis for the DPF system is determined in a steady state other than the above 1) to 4).

When the start of the failure diagnosis for the DPF system is determined, a step of determining the start time t for the failure diagnosis proceeds (S105).

That is, if the compensated PM measurement value is smaller than the variance value (DPF_Monitor_start_var_apv) calculated during the set time (DPF_Monitor_start_time_apv), the start time t for the DPF system diagnosis is determined, So that the DPF system diagnosis can be started in the driving condition.

At this time, an average value during a specific time (t) for diagnosing the failure of the PM value measured at the downstream of the DPF is obtained through the following equation (1), and the average value is calculated according to the following equation The variance value is obtained (S106).

Next, the calculation end point (t + a) for the average and variance is determined based on the DPF channel state (S107).

In the (t + a) time determination, the a time is a value determined by an internal deposition shot value of the DPF and a channel length value reduced by ash deposition of the DPF, to be.

More specifically, the value a is a value determined according to a channel, which is a DPF filter use area, which is decreased when the number of regeneration times of the DPF increases. The reason why the value of the channel is decreased is that the ash (Ash).

At this time, based on the determined calculation end point (t + a), an average value during a specific time (t + a) for diagnosing the failure of F (t) , And a variance value is calculated based on the above equation (2) using the calculated average value.

Then, an average value for a specific time (t, t + a) for diagnosis of F (t) is obtained as described above, a variance value is obtained using the calculated average value, and then compared with the variance value obtained through direct testing (S108) for diagnosing the abnormality of the DPF is proceeded.

If the dispersion value measured during (t + a) is smaller than the minimum reference variance value (DPF_system_fault_min_MPV) obtained in advance by directly testing the DPF in the step of diagnosing the abnormality of the DPF system, Diagnosis is made by DPF clogging due to ash deposition.

On the other hand, if the dispersion value measured during (t + a) is larger than the maximum reference dispersion value (DPF_system_fault_max_MPV) obtained through the direct test on the DPF, the amount of exhaust gas passing through the DPF crack portion increases and the measured PM amount increases And diagnoses that a crack has occurred in the DPF.

On the other hand, when the DPF system is diagnosed as a result of the DPF clogging, or when it is diagnosed that the DPF is cracked, a driver warning (for example, a warning lamp is turned on) is made.

10: DOC
12: DPF
13: Differential pressure sensor
14: Exhaust pipe
15: HCI
16, 17: Temperature sensor
18: PM sensor

Claims (6)

Measuring a PM amount in a PM sensor mounted at a rear end of the DPF;
Compensating the measured value measured by the PM sensor in consideration of an engine driving condition;
A DPF system state check step of checking a current state of the DPF system;
If the DPF system is in a normal state, the start of the fault diagnosis of the DPF system is determined to determine a start time t for fault diagnosis;
Determining a calculation end point (t + a) for an average value and a variance value based on a channel state of the DPF;
Obtaining a mean value during a specific time (t, t + a) for diagnosing the failure of the PM value measured at the downstream of the DPF, and obtaining a variance value using the calculated average value;
Diagnosing the abnormality of the DPF system by comparing the obtained dispersion value with the dispersion value obtained through the test;
And a fault diagnosis method for a DPF system for an automobile.
The method according to claim 1,
Further comprising the step of filtering the signal measured by the PM sensor by a Min-max filter to reduce a measurement error.
The method according to claim 1,
During the DPF system state check step,
1) If the DPF is playing,
2) If any one of DOC input side and output side temperature sensor, differential pressure sensor, and HCI that controls the DPF system fails,
3) If the PM sensor itself is defective,
4) If the internal soot accumulation amount of the DPF is less than or equal to the minimum reference value,
Wherein a fault diagnosis for the DPF system is not performed.
The method according to claim 1,
Wherein the starting time (t) for the fault diagnosis is determined when the compensated PM measurement value is smaller than the variance value calculated during the set time.
The method according to claim 1,
In the step of determining the calculation end point (t + a)
a time is determined by an internal deposition shot value of the DPF and a channel length value reduced by ash deposition of the DPF.
The method according to claim 1,
In the step of diagnosing the abnormality of the DPF system,
If the dispersion value measured during (t + a) is smaller than the minimum reference dispersion value obtained through the test, the DPF is diagnosed as clogging, and the dispersion value measured during (t + a) The diagnosis is made that a crack has occurred in the DPF.

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