JP6201578B2 - Diagnostic equipment - Google Patents

Description

  The present invention relates to a diagnostic device, and more particularly, to a diagnosis of an exhaust purification filter provided in an exhaust system of an internal combustion engine.

  Diesel Particulate Filter (DPF) that collects particulate matter (PM) mainly contained in exhaust as an exhaust purification filter installed in exhaust systems such as diesel engines )It has been known.

  If the PM collection capability of the DPF deteriorates due to melting damage, etc., the PM that is slipped without being collected by the DPF may be released to the atmosphere, and the exhaust gas regulation value may not be satisfied. Therefore, there is a request for diagnosing a DPF failure in an on-board state.

  As a technique for determining a failure of a DPF, for example, a method of providing a resistance PM sensor on the downstream side of the DPF and comparing the sensor value with a reference threshold is known (for example, see Patent Document 1).

JP 2009-1444577 A

  In general, a resistance PM sensor detects the amount of PM by utilizing the fact that the resistance value between electrodes changes due to conductive PM adhering between a pair of electrodes. However, in the resistance type PM sensor, if the electrical resistance of the PM adhering between the electrodes changes when affected by the exhaust temperature or the exhaust flow rate, there is a possibility that an accurate PM amount cannot be detected. For this reason, there is a problem that the diagnosis method based on the sensor value of the resistance PM sensor cannot accurately determine the failure of the DPF.

  An object of the present invention is to provide a diagnostic apparatus that can determine a DPF failure with high accuracy.

  In order to achieve the above object, a diagnostic device of the present invention includes a filter that collects particulate matter in exhaust gas discharged from an internal combustion engine, and a particulate matter that is provided on the downstream side of the filter and adheres between electrodes. A sensor capable of detecting the amount of particulate matter from the current value flowing through the substance and regenerating the particulate matter by burning when the particulate matter adhered between the electrodes reaches a predetermined amount, and from the end of regeneration of the sensor An actual interval calculating means for calculating an actual interval until the next regeneration start, a slip amount estimating means for estimating a slip amount of particulate matter discharged from the internal combustion engine and passing through the filter, and an exhaust state of the internal combustion engine And a deposition state of particulate matter adhering between the electrodes based on a multiple regression equation including the amount and the estimated slip amount as an input value, and based on the deposition state. And an estimation interval calculating means for calculating an estimated interval from the end of regeneration of the sensor to the start of the next regeneration, and a determining means for comparing at least the actual interval with the estimated interval to determine at least a failure of the filter. It is characterized by providing.

  The determination means may determine that the filter is faulty when the actual interval is less than the estimated interval, and determine that the filter is normal when the actual interval is equal to or greater than the estimated interval. Good.

  The determination unit may determine that the filter is normal when regeneration of the filter is not started even after a predetermined threshold time has elapsed after the calculation of the estimation interval. .

  The determination unit may determine that the filter is faulty when the calculation of the estimation interval does not end even when a predetermined threshold time has elapsed after the calculation of the actual interval. Good.

Further, the determination unit may determine that the filter is faulty when a ratio between the actual interval and the estimated interval falls below a predetermined upper limit threshold.

  According to the diagnostic apparatus of the present invention, it is possible to determine a DPF failure with high accuracy.

1 is a schematic overall configuration diagram showing an intake / exhaust system of an engine to which a diagnostic device according to an embodiment of the present invention is applied. (A) is a typical perspective view which shows the principal part of the resistance type PM sensor of this embodiment, (b) is a figure which shows the sensor reproduction | regeneration signal of a resistance type PM sensor. It is a functional block diagram which shows ECU40 of this embodiment. It is a figure explaining an example of failure diagnosis of this embodiment. It is a figure explaining an example of failure diagnosis of this embodiment. It is a figure explaining an example of failure diagnosis of this embodiment.

  Hereinafter, based on an accompanying drawing, a diagnostic device concerning one embodiment of the present invention is explained. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, a diesel engine (hereinafter simply referred to as an engine) 10 is provided with an intake manifold 10a and an exhaust manifold 10b. An intake passage 11 for introducing fresh air is connected to the intake manifold 10a, and an exhaust passage 12 for releasing exhaust gas to the atmosphere is connected to the exhaust manifold 10b.

  In the intake passage 11, an air cleaner 13, a MAF sensor 31, a supercharger compressor 14 a, an intercooler 15, an intake air temperature sensor 32, an intake oxygen concentration sensor 33, a boost pressure sensor 34, and the like are provided in order from the intake upstream side. Yes. In the exhaust passage 12, a turbocharger turbine 14b, an exhaust oxygen concentration sensor 35, an air-fuel ratio sensor 36, an exhaust temperature sensor 37, an exhaust aftertreatment device 50, and the like are provided in order from the exhaust upstream side. In FIG. 1, reference numeral 38 denotes an engine rotation sensor, and reference numeral 39 denotes an accelerator opening sensor.

  The exhaust aftertreatment device 50 is configured by arranging an oxidation catalyst (Diesel Oxidation Catalyst: DOC) 51 and a DPF 52 in order from the exhaust upstream side in a catalyst case 50a. An exhaust pipe injection device 53 is provided on the exhaust upstream side of the DOC 51, and a resistance PM sensor 20 that detects the amount of PM in the exhaust gas that has passed through the DPF 52 is provided on the downstream side of the DPF 52.

  The exhaust pipe injection device 53 injects unburned fuel (mainly HC) into the exhaust passage 12 in accordance with an instruction signal output from an electronic control unit (hereinafter, ECU) 40. In addition, when using the post injection by the multistage injection of the engine 10, this in-pipe injection device 53 may be omitted.

  The DOC 51 is formed, for example, by carrying a catalyst component on the surface of a ceramic carrier such as a cordierite honeycomb structure. When HC is supplied by the exhaust pipe injection device 53 or the post injection, the DOC 51 oxidizes this and raises the exhaust temperature.

  The DPF 52 is formed, for example, by arranging a large number of cells partitioned by porous partition walls along the flow direction of the exhaust gas and alternately plugging the upstream side and the downstream side of these cells. The DPF 52 collects PM in the exhaust gas in the pores and surfaces of the partition walls, and when the amount of accumulated PM reaches a predetermined amount, so-called forced filter regeneration is performed to remove the PM. The forced regeneration of the filter is performed by supplying unburned fuel (HC) to the DOC 51 by the in-pipe injection device 53 or post injection, and raising the exhaust temperature flowing into the DPF 52 to the PM combustion temperature (for example, about 600 ° C.). Is called.

  As shown in FIG. 2A, the resistance PM sensor 20 includes a pair of comb-like electrodes 22 to which a voltage is applied on an insulating substrate 21, and the resistance value between the electrodes 22 is conductive. The amount of PM is detected by utilizing the change due to the adhesion of PM. Further, the resistance type PM sensor 20 includes a heater (not shown). As shown in FIG. 2B, when a predetermined amount of PM deposited between the electrodes 22 accumulates, the heater is heated by the heater to remove the combustion. Sensor regeneration is performed. This sensor regeneration signal (start signal / end signal) is output to the electrically connected ECU 40.

  The ECU 40 controls the engine 10, the exhaust pipe injection device 53, and the like, and includes a known CPU, ROM, RAM, input port, output port, and the like.

  Further, as shown in FIG. 3, the ECU 40 includes an actual regeneration interval calculation unit 41, an engine exhaust PM amount calculation unit 42, a PM slip amount calculation unit 43, an estimated regeneration interval calculation unit 44, and a DPF diagnosis unit 45. As a part of functional elements. Each of these functional elements will be described as being included in the ECU 40 which is an integral hardware, but any one of them can be provided in separate hardware.

  The actual playback interval calculation unit 41 is an example of the actual interval calculation means of the present invention, and a period from the end of playback of the resistive PM sensor 20 to the start of the next playback (hereinafter, this period is referred to as the actual playback interval INTact). Calculate. The actual reproduction interval INTact is calculated based on the reproduction start signal and the reproduction end signal input from the resistance type PM sensor 20.

The engine exhaust PM amount calculation unit 42 constitutes a part of the slip amount estimation means of the present invention, and calculates the PM amount discharged from the engine 10 in real time (hereinafter referred to as engine exhaust PM amount MEG_out). The engine exhaust PM amount MEG_out is calculated from, for example, a model equation including the oxygen concentration O2 of the intake / exhaust system detected by the various sensors 31 to 39, the air-fuel ratio λ, the exhaust temperature T _{exh and the} like as input values. The engine exhaust PM amount MEG_out may be obtained by reading a value corresponding to the engine operating state detected by the sensors 38, 39, etc., from a PM exhaust amount map (not shown) created in advance by experiments or the like.

The PM slip amount calculation unit 43 constitutes a part of the slip amount estimation means of the present invention, and calculates the PM amount passing through the DPF 52 (hereinafter referred to as PM slip amount M _{DPF_slp} ) in real time. More specifically, the ECU 40 stores the PM slip rate SLP _% when the PM collection capability of the DPF 52 obtained in advance by experiments or the like is assumed to be normal. The PM slip amount M _{DPF_slp} is obtained by multiplying the engine exhaust PM amount M _{EG_out} by the PM slip rate SLP _% (M _{DPF_slp} = M _{EG_out} · M _{DPF_slp} ). The PM slip ratio SLP _% is preferably set based on the state immediately before the DPF 52 fails due to melting or the like. This makes it possible to reliably detect a failure of the DPF 52 immediately before the PM slip amount exceeds the exhaust gas reference value or the like in failure diagnosis described later.

The estimated regeneration interval calculating unit 44 is an example of the estimated interval calculating means of the present invention, and estimates from the end of regeneration of the resistive PM sensor 20 to the start of the next regeneration, assuming that the PM collection capability of the DPF 52 is normal. A period (hereinafter, this period is referred to as an estimated reproduction interval INTTest) is calculated. Estimated regeneration interval INTE _st the exhaust temperature, the exhaust flow rate and, using a PM slip amount (outlet PM of DPF 52), is calculated based on the model expression prepared in advance by multiple regression analysis. A detailed calculation procedure will be described below.

At the start of sensor regeneration, the resistance value (corresponding current value) between the electrodes 22 and the PM deposition amount (mainly soot) between the electrodes 22 are constant. That is, as shown in Equation 1 below, the PM accumulation amount M _{soot_reg} between the electrodes 22 obtained by multiplying the PM slip amount MDPF_slp by a predetermined correction coefficient CF during the regeneration interval _{T_reg} is obtained by sensor regeneration. It becomes constant at the start.

  During the steady operation of the engine 10, the PM slip amount MDPF_slp and the correction coefficient CF do not change. Therefore, Equation 1 is replaced with Equation 2 below.

Since the PM deposition amount ratio M _norm between the electrodes 22 is 1 (100%) at the start of sensor regeneration, it can be expressed by the following Equation 3.

In Expression 3, when the ratio between the correction coefficient CF and the PM deposition amount M _{soot_reg} is normalized assuming a predetermined correction coefficient CC, the following Expression 4 is obtained.

When an exhaust temperature, an exhaust flow rate, and a PM slip amount are measured in advance through experiments or the like and a multiple regression analysis is performed, the correction coefficient CC is an equation having the exhaust temperature T _exh , the exhaust flow rate Q _exh, and the PM slip amount MDPF_slp as input values. Defined as a multiple regression function of 5.

As shown in Equation 6 below, the PM accumulation amount ratio M _norm obtained by integrating the value obtained by multiplying the PM slip amount MDPF_slp by the correction coefficient CC from the end of sensor regeneration in the transient operation state of the engine 10 is It becomes 1 (100%) at the start of sensor regeneration (when PM deposition between the electrodes 22 is completed).

The estimated regeneration interval calculation unit 44 starts the calculation of the PM deposition amount ratio M _norm based on the above formulas 5 and 6 from the end of the sensor regeneration. The estimated regeneration interval INTTest is calculated by measuring the period from the end of sensor regeneration until the calculated value of the PM accumulation amount ratio M _norm becomes 1 by a timer (not shown) built in the ECU 40. Has been. In Equation 5, the exhaust gas temperature T _exh is acquired from the exhaust gas temperature sensor 37, and the exhaust gas flow rate Q _exh is calculated from the detection value of the MAF sensor 31, the fuel injection amount of the engine 10, or the like, or an exhaust gas flow rate not shown. Obtained directly from the sensor.

  The DPF diagnosis unit 45 is an example of a determination unit according to the present invention, and is based on the actual reproduction interval INTact input from the actual reproduction interval calculation unit 41 and the estimated reproduction interval INTTest input from the estimated reproduction interval calculation unit 44. Thus, the failure or normality of the DPF 52 is determined. Hereinafter, a specific determination method will be described with reference to FIGS.

  The determination method shown in FIG. 4 directly compares the actual reproduction interval INTact and the estimated reproduction interval INTTest. In this determination method, when the actual playback interval INTact is shorter than the estimated playback interval INTTest (INTact <INTTest), the DPF 52 is determined to be faulty. On the other hand, when the actual reproduction interval INTact is equal to or longer than the estimated reproduction interval INTTest (INTact ≧ INTTest), the DPF 52 is determined to be normal.

  The determination method shown in FIG. 5 aims at shortening the diagnosis time and increasing the number of diagnoses. In FIG. 5A, if the next sensor regeneration start signal is not input even after a predetermined threshold time has elapsed after the calculation of the estimated regeneration interval INTTest, the DPF 52 is determined to be normal. Thereby, when the DPF 52 is normal, it is possible to determine the normal state of the DPF 52 at an early stage without waiting for the completion of the calculation of the actual reproduction interval INTact.

  In FIG. 5B, if the calculation of the estimated reproduction interval INTTest is not completed even after a predetermined threshold time has elapsed after the calculation of the actual reproduction interval INTact, the DPF 52 is determined to be faulty. As a result, when the deterioration of the DPF 52 is significant, it is possible to detect a failure of the DPF 52 at an early stage without waiting for the calculation of the estimated regeneration interval INTTest to end.

The determination method shown in FIG. 6 uses a ratio between the actual reproduction interval INT _act and the estimated reproduction interval INT _est . In this determination method, when the ratio% INT obtained by dividing the actual reproduction interval INT _act by the estimated reproduction interval INT _est falls below a predetermined upper limit threshold T _MAX% , the DPF 52 is determined to be a failure. The upper threshold value T _MAX% is _preferably set, for example, based on a state immediately before the PM slip amount passing through the DPF 52 does not satisfy the exhaust gas reference value due to melting damage or the like (normal product immediately before failure).

  Next, functions and effects of the diagnostic apparatus according to the present embodiment will be described.

  Conventionally, as a technique for diagnosing a DPF failure, a method of comparing a PM amount detection value of a resistance PM sensor provided on the downstream side of the DPF with a threshold value is known. However, since the electrical resistance of PM adhering between the electrodes changes due to the influence of the exhaust temperature and the exhaust flow rate, the diagnosis method based on the detected PM amount of the resistance PM sensor cannot accurately determine the deterioration of the DPF. There is.

  On the other hand, in the diagnostic device of the present embodiment, the actual regeneration interval INTact calculated from the sensor regeneration signal of the resistive PM sensor 20 without using the PM amount detection value of the resistive PM sensor 20, the exhaust temperature, A failure or normality of the DPF 52 is determined on the basis of an estimated regeneration interval INTTest calculated from a model formula (Formulas 5 and 6) created by multiple regression analysis of the exhaust flow rate and the PM slip amount. Therefore, according to the diagnostic device of the present embodiment, the diagnostic accuracy of the DPF 52 can be effectively improved without being affected by the exhaust temperature and the exhaust flow rate.

  In the diagnostic apparatus of the present embodiment, the model formula for calculating the estimated regeneration interval INTTest is configured to include the exhaust flow rate, the exhaust temperature, and the PM slip amount as input values. Therefore, according to the diagnosis device of the present embodiment, compared with a technique for diagnosing the DPF by simply comparing the actual regeneration interval and the threshold value, the operation history of the engine 10 between the regeneration intervals is taken into consideration. Diagnosis can be performed.

  Further, in the diagnostic device of the present embodiment, the DPF 52 is determined to be normal when the next sensor regeneration start signal is not input even after a predetermined time has elapsed after the calculation of the estimated regeneration interval. That is, when the DPF 52 is normal, the determination can be made early without waiting for the calculation of the actual regeneration interval to end. Therefore, according to the diagnostic apparatus of this embodiment, it is possible to effectively shorten the diagnosis time and increase the number of diagnoses.

  Further, in the diagnosis device of the present embodiment, if the calculation of the estimated regeneration interval does not end even after a predetermined time has elapsed after the calculation of the actual regeneration interval, the DPF 52 is determined to be faulty. That is, when the deterioration of the DPF 52 is significant, it is possible to determine a failure without waiting for the calculation of the estimated regeneration interval to end. Therefore, according to the diagnostic apparatus of the present embodiment, it is possible to detect a failure of the DPF 52 at an early stage.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, although the DPF 52 and the DOC 51 have been described as being provided separately, they may be integrated. Further, the engine 10 is not limited to a diesel engine, and can be widely applied to other internal combustion engines such as a gasoline engine.

10 Engine 20 Resistance PM Sensor 22 Electrode 40 ECU
41 Actual regeneration interval computation unit 42 Engine exhaust PM amount computation unit 43 PM slip amount computation unit 44 Estimated regeneration interval computation unit 45 DPF diagnosis unit 51 DOC
52 DPF
53 Exhaust pipe injection device

Claims (5)

A filter that collects particulate matter in the exhaust discharged from the internal combustion engine;
Provided on the downstream side of the filter, the amount of particulate matter is detected from the current value flowing through the particulate matter attached between the electrodes, and when the amount of particulate matter attached between the electrodes reaches a predetermined amount, the particulate matter is removed. A recyclable sensor that burns away,
An actual interval calculating means for calculating an actual interval from the end of reproduction of the sensor to the start of the next reproduction;
Slip amount estimating means for estimating a slip amount of particulate matter discharged from the internal combustion engine and passing through the filter;
Based on the exhaust temperature and exhaust flow rate of the internal combustion engine and the estimated slip amount , the following formulas 1 and 2 (where T _exh is the exhaust temperature, Q _exh is the exhaust flow rate, M _{DPF_slp} is the slip amount, and M _norm is the electrode) The accumulation state of the particulate matter adhering between the electrodes is estimated on the basis of the particulate matter deposition amount ratio in the _meantime , _{T_reg} is the regeneration interval) , and the next regeneration from the end of regeneration of the sensor based on the deposition state An estimated interval calculating means for calculating an estimated interval until the start;
A determination unit that compares the actual interval with the estimated interval and determines at least a failure of the filter; and
The estimated interval calculation means starts calculation of the particulate matter deposition amount ratio M _norm based on the mathematical expressions 1 and 2 from the end of the sensor regeneration until the calculated value of the particulate matter deposition amount ratio M _norm becomes 1. The estimated interval is calculated by measuring the period of
A diagnostic apparatus characterized by that.

The determination means includes
The diagnostic device according to claim 1, wherein when the actual interval is less than the estimated interval, the filter is determined as a failure, and when the actual interval is equal to or greater than the estimated interval, the filter is determined as normal. The determination means includes
The diagnostic device according to claim 1 or 2, wherein if the regeneration of the sensor is not started even after a predetermined threshold time has elapsed after the calculation of the estimated interval, the filter is determined to be normal. The determination means includes
The filter is determined to be a failure if the calculation of the estimated interval does not end even after a predetermined threshold time has elapsed after the calculation of the actual interval. Diagnostic equipment. The determination means includes
The diagnostic device according to any one of claims 1 to 3, wherein the filter is determined to be faulty when a ratio between the actual interval and the estimated interval falls below a predetermined upper limit threshold value.

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