• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
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  • 优先权
    • 专利摘要:
    A method of diagnosing a differential pressure sensor (15) which determines a differential pressure (16) of an exhaust after-treatment unit (11). This sensor is connected by an upstream connection (15.1) to the pipe (11) and downstream (15.2). The diagnosis is made on the basis of the comparison of a gradient as a function of time of the measured differential pressure (16) and a predicted gradient (32). The correlation between the measured gradient curve (33) and the predicted gradient curve (32) is determined. For a high correlation neither the sensor (15) nor its connections (15.1, 15.2) are defective.
    公开号:FR3021355A1
    申请号:FR1554313
    申请日:2015-05-13
    公开日:2015-11-27
    发明作者:Thomas Zein；Yunjie Lian
    申请人:Robert Bosch GmbH；
    IPC主号:
    专利说明:

    [0001] Field of the invention The present invention relates to a method of diagnosing a differential pressure sensor which determines a differential pressure of an exhaust aftertreatment unit installed in an exhaust pipe and causing part of an exhaust cleaning system of a heat engine, this sensor being connected by an upstream connection to the exhaust gas line upstream of the gas after-treatment unit. exhaust and downstream connection to the exhaust pipe downstream of the exhaust aftertreatment unit, the diagnosis being made on the basis of the comparison of a gradient as a function of time of the Differential pressure measured as a result of a variation of the exhaust gas pressure upstream of the exhaust aftertreatment unit and a gradient as a function of time of the predictive differential pressure. The invention also relates to a diagnostic unit characterized in that it comprises an electrical circuit or a program for executing the method. State of the art The regulations on emissions, particularly in Europe and the United States, set limit values for the emission of pollutants by thermal engines. In order to comply with this regulation exhaust gas or engine exhaust gas systems have exhaust cleaning facilities with an exhaust aftertreatment unit, for example under the engine exhaust system. form of catalyst or particulate filter. The correct operation of such installations must be checked. In addition to the emission limit values, the regulation also sets diagnostic limit values for which a fault must be reported in the event of an overshoot. This is why diagnostic functions are implemented in vehicles that monitor the parts and components used to reduce emissions during vehicle operation by an on-board diagnostic (OBD diagnostic) and display any faulty operation resulting in an overrun. diagnostic limits.
    [0002] To monitor the operation of an exhaust aftertreatment unit, particularly a particulate filter, it is known to monitor the pressure drop (pressure drop) in the gas aftertreatment unit. exhaust. In the case of the particle filter, this pressure drop increases with the accumulation of soot. This can be monitored by measuring the pressure difference (differential pressure) of the particulate filter and initiating a regeneration phase of the particulate filter when this capacity limit is reached. The particulate filter may be the one installed in the exhaust line of a gasoline or diesel fuel engine; it may be a simple, uncoated particulate filter or a particulate filter with a catalytic coating combining a particulate filter with a three-way catalyst. In addition to the monitoring of the aftertreatment unit of the exhaust gases, the sensor of the latter must also be monitored. A differential pressure sensor (also called pressure difference sensor) is generally connected by two connections to the exhaust pipe; one of the connections is upstream and the other downstream of the exhaust aftertreatment unit that is monitored. The connections can be simple pipes. If any of the connections are faulty or damaged, the result of the diagnosis of the exhaust aftertreatment unit is distorted. Ensuring the safety of detecting a failure of a differential pressure sensor connection is an operation that is in part very delicate since the measurement signal of the differential pressure sensor can always be in a valid range, even in case of disappearance of a connection. DE 10 2005 034 270 A1 discloses a method and apparatus for monitoring a differential pressure sensor installed in parallel with an exhaust gas component, particularly a particulate filter. The dynamic behavior of the differential pressure signal is then exploited as a consequence of a modification of the pressure of the exhaust gases upstream of the component of the exhaust gas installation. According to an alternative embodiment, the gradient of the differential pressure signal is determined in the event of variation of the pressure of the exhaust gas and is compared with a second threshold. The second threshold is formed using the operating parameters of the heat engine and it corresponds at least by approximation to the forecast signal of the gradient. If the gradient of the pressure signal does not exceed the second threshold, it is assumed that there is a fault in the upstream pipe (the upstream pipe is clogged or cut), with respect to the differential pressure sensor. According to another variant, the excursion of the differential pressure signal is used as a function of time. The signal curve is thus exploited for one of the different variations of the exhaust gas pressure. To increase the security of the diagnosis it is possible to carry out several separate evaluations of this type and to conclude on an upstream connection, defective in the case of repetition of the fault message. DE 10 2011 003 748 A1 describes a method and a device for monitoring the operation of a differential pressure sensor connected by connections in parallel with the particulate filter. Downstream of the particulate filter, depending on the direction of passage of the gases, there is an exhaust flap. In order to monitor the connections of the differential pressure sensor, the position of the exhaust flap is modified so that the counterpressure of the exhaust gases upstream of the flap increases and the pressure upstream and downstream of the particulate filter increases. If the differential pressure sensor is correctly connected, the measured pressure difference remains within the predefined tolerances. But if one of the connections has come loose, the pressure variation of the differential pressure sensor will not be transmitted. Thus, the measured differential pressure changes and the fault will be detected. If the differential pressure exceeds a given predicted value, it is assumed that there is a fault in the downstream connection because then the pressure increase at the outlet of the particulate filter will not be transmitted to the differential pressure sensor. If, however, the front connection is defective, the pressure variation produced by the exhaust flap results in a negative variation of the measured differential pressure.
    [0003] According to one variant, the evolution over time of the differential pressure measured after a variation of the position of the flap of the exhaust gases is also exploited. If, for example because of a jam or a blocked connection, the modified pressure on one side of the differential pressure sensor is delayed, it will be noted that it is a fault. The process requires an exhaust flap in the exhaust gas channel downstream of the particulate filter which is not the case in most exhaust systems so that the process can not be carried out. 'apply. DE 10 2007 000 892 B4 discloses a diagnostic apparatus for detecting the plugging of the connection of an apparatus for capturing a differential pressure (differential pressure). The device measures the differential pressure of the exhaust cleaning device. Differential pressure is determined for a stationary operating point. Next, a second stationary operating point is set which provides for a significant variation of the differential pressure with respect to the first stationary operating point. If the connection line is jammed, the measured differential pressure converges only slowly towards a stable end value. If the time required to reach this final value is too long, it is considered that there is a blockage of the transmission of gases from the connection of the apparatus. The method does not detect a faulty connection. OBJECT OF THE INVENTION The present invention aims to develop a method for ensuring the monitoring of a differential pressure sensor vis-à-vis various causes of defect.
    [0004] The invention also aims to develop a diagnostic unit for the implementation of such a method. DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose, the subject of the invention is a method for diagnosing a differential pressure sensor of the type defined above, characterized in that the correlation between the curve of the gradient of the differential pressure measured and that of the gradient curve of the predicted differential pressure and for a high correlation it is concluded that the differential pressure sensor is not defective and has non-defective connections and for a low correlation it is concluded that a sensor defective differential pressure or a fault in one or both differential pressure sensor connections. According to the invention it is possible to determine and exploit the correlation of at least two and more than two variations of the pressure of the exhaust gases.
    [0005] By exploiting the gradient of the differential pressure, the process is independent of the measured absolute pressure differences which, for example, even in the event of failure of the differential pressure sensor connection, can always be within a valid range of values. By forming the correlation between the measured differential pressure gradient and the predicted differential pressure gradient, the two gradients can be compared over a long period of time, which significantly reduces the risk of misdiagnosis for exploiting a single variation. differential pressure. This is particularly true if during the operating period during which the correlation is determined, there are several variations in the pressure of the exhaust gas and thus in the differential pressure. The determination of the correlation between the measured differential pressure gradient and the predicted differential pressure gradient can be reliably applied and determined by forming a standard cross-correlation of the measured differential pressure gradient plot and the trace. From the predictive differential pressure gradient, a cross-correlation value is formed and the correlation between the measured evolution and the predicted evolution of the differential pressure gradient is evaluated using the cross-correlation value.
    [0006] For this purpose, the cross-correlation value KKF is formed, for example by applying the following relation: KKF = EMAp (k)) * (14p * (k) »I EMAp * (k)) * Cl (Ap * (k) )) (1) In this formula d (Ap (k)) / dk represents the gradient of the differential measured pressure and d (Ap * (k)) / dk represents the gradient of the predicted differential pressure of an intact unit aftertreatment of the exhaust gases. The thus obtained standardized cross-correlation value is independent of the level of the gradient signal and thus takes high values or low values for insufficient correlation and values close to 1 for good correlation. According to a particularly preferred embodiment of the invention, it is concluded that the rear connection of the differential pressure sensor is damaged or is cut off if the cross correlation value exceeds a first predefined correlation threshold, preferably a first threshold. greater than unity correlation and particularly preferably a first correlation threshold greater than 1.2 and / or it is considered that the front connection of the differential pressure sensor is damaged or is cut if the correlation value crosses. - Sée is less than a second correlation value, predefined, preferably less than a second correlation threshold, less than zero and particularly preferably less than a second correlation threshold less than -0.2. The diagnosis thus makes it possible to detect and precisely locate the defect. If the back connection of the differential pressure sensor is faulty or damaged, the gradient as a function of time of the differential pressure signal increases significantly because this sensor no longer captures only the pressure difference on the after-treatment unit of the differential gas. exhaust, but measure this difference in pressure with respect to the ambient pressure. Thus the differential pressure sensor additionally captures the pressure drop on the components of the exhaust gas system downstream of the aftertreatment unit of the exhaust gas in the exhaust pipe, for example Exhaust pipe. The standardized cross-correlation thus gives a value significantly greater than 1.0 which exceeds the range of values of the cross-correlation coefficient for an intact and correctly connected differential pressure sensor and thus an exhaust after-treatment unit. which is intact. If the differential pressure sensor's upstream connection is faulty or damaged, this differential pressure sensor measures negative differential pressures in extended ranges and negative differential pressure gradients. Standard cross-correlation thus has a value significantly lower than zero. The cross-correlation coefficient obtained exceeds the range of values for an intact differential pressure sensor and an intact exhaust aftertreatment unit or for if the exhaust after-treatment unit has been dismounted. It is thus possible to determine the predicted differential pressure gradient to determine the evolution of the measured differential pressure and at least from the volume flow rate of the exhaust gases in the exhaust aftertreatment unit and the loss. load of this post-processing unit. The predicted differential pressure is thus simply the product of the current flow rate of the exhaust gas and the pressure drop. The variation as a function of time of the volume flow rate of the exhaust gases for a pressure drop that is at least substantially constant during the diagnosis period results in a change in the predicted differential pressure and thus in the differential gradient of the differential pressure. The presumed pressure drop may correspond, for example, to an exhaust aftertreatment unit operating at the limit of a maximum possible pressure drop. This avoids misdiagnosis. According to another preferred variant of the method, a low-pass filtering of the differential pressure measured on the exhaust after-treatment unit and / or the predictive differential pressure on this unit and / or flow rate of the exhaust gas to determine the predicted differential pressure. This eliminates for the diagnosis signal variations generated by disturbances which improves the quality of the diagnosis. The correlation of the variations in the measured and the predicted differential pressures can only be exploited for sufficient dynamic operating conditions of the engine. For this purpose it is intended to make the diagnoses only if the differential pressure gradient, preferably the predicted differential pressure gradient or a measurement in correlation with this differential pressure gradient exceeds a predefined value. As a measure in correlation with the differential pressure gradient, there is, for example, the gradient of the exhaust gas mass flow rate, the exhaust gas volume flow rate, the engine speed and the quantities thereof. deducted.
    [0007] It is expected that the differential pressure sensor will determine this differential pressure on a particulate filter so that the operation of the differential pressure sensor and thus that of the particulate filter can be monitored. The monitoring of the particulate filter by a differential pressure sensor is the usual method currently.
    [0008] The method thus finds a wide range of applications and the diagnosis of the differential pressure sensor is done without the need for additional component, only by relying economically on the existing data. The method preferably applies to a gasoline engine whose exhaust gas system comprises at least one catalyst and a separate particulate filter or a catalyst-particle filter combination or a catalytically coated particle filter. In the case of gasoline engines, compared with diesel engines, the flow rate is rather lower, which translates into lower pressure differences on the gasoline particulate filter used. The excellent quality of confirmation of the process also allows a guaranteed detection of a fault in the connections of the differential pressure sensor, even under adverse conditions. The invention also relates to a diagnostic unit characterized in that it comprises an electric circuit or that it applies a program for carrying out the method as defined above. It allows in particular to apply the program in an economical way. According to another characteristic, the diagnostic unit is a separate component or component integrated in the control or management of the motor which makes it possible to carry out the diagnosis of the differential pressure sensor in a component specially designed for this purpose or without additional component and this in an economical way. The engine control also has all the usual data necessary for the execution of the method as described.
    [0009] Drawings The present invention will be described below, in more detail with the aid of an exemplary embodiment shown in the accompanying drawings, in which: FIG. 1 is a diagram of an alternative embodiment of the technical environment applying FIG. 2 shows a first diagram of the measured differential pressure curve and the predicted differential pressure curve on a particulate filter for a non-defective differential pressure sensor, FIG. the differential pressure curve measured and the predicted differential pressure curve on a particulate filter when the back connection of the differential pressure sensor is open, Figure 4 shows a third diagram of the measured differential pressure curve and the predictive differential pressure of a particulate filter whose connection before the Differential pressure gauge is open, Figure 5 shows a fourth diagram of the measured differential pressure curve and the predicted differential pressure curve if the particulate filter is disassembled or defective, Figure 6 shows a fifth diagram of the measured differential pressure curve and predicted differential pressure curve with back connection of the differential pressure sensor open, Figure 7 shows a sixth diagram of the measured differential pressure curve and the predicted differential pressure curve for a sensor 8 shows a seventh graph of the cross correlation coefficient curves determined from the differential pressure gradient for different differential pressure sensor defects. Description of Embodiments figure 1 schematically shows an embodiment of the technical environment in which the invention is inscribed. The representation is limited to the components necessary for the description of the invention. The figure shows for example a heat engine 10 in the form of a gasoline engine; the exhaust gases of the heat engine 10 are discharged through an exhaust gas pipe 11. The exhaust gas pipe 11 comprises a multi-stage exhaust gas cleaning system. In the direction of passage of the exhaust gas stream 14, the exhaust pipe 11 comprises a catalytic converter 12 in the form of a three-way catalyst and a particulate filter 13 constituting aftertreatment units for the exhaust gases. 'exhaust. The particulate filter 13 is followed by a muffler 17.
    [0010] A differential pressure sensor 15 is connected to diagnose the particulate filter 13. The sensor 15 determines the pressure difference (differential pressure 16) between the inlet and the outlet of the particulate filter 13. For this, the differential pressure sensor 15 is connected by an upstream connection 15.1 to the exhaust gas duct 11 upstream of the particulate filter 13 and by a downstream connection 15.2 to the exhaust gas duct 11, downstream of the particulate filter 13. The output signal of the differential pressure sensor 15 is applied to a diagnostic unit 18 which performs, as part of an on-board diagnosis (OBD diagnosis), the diagnosis of the differential pressure sensor 15 to detect any break or damage. upstream or downstream 15.1, 15.2 This diagnostic unit 18 may be part of the main control or management of the engine (ECU control). The connections 15.1, 15.2 of this embodiment are pipes. If one of the connections 15.1, 15.2 is defective or if it is damaged for example by a rodent bite, the determined differential pressure 16 will be false so that the diagnosis of the particle filter 13 will be considered as erroneous. The differential pressures 16, measured in particular in the case of damaged or disconnected connections 15, will be in the range of the usual values, which makes it practically impossible to distinguish the normal operation by measuring the absolute differential pressure 16. FIG. diagram of the measured differential pressure curve 23 and the predicted differential pressure 22 on the particle filter 13 of FIG. 1 in case of a differential pressure sensor 15, intact and correctly connected. For this, the differential pressure curves 22, 23 are the curves of the predicted differential pressure for an intact particle filter 13 along the time axis 20 and along the axis 21 representing the differential pressure. The predicted differential pressure curve 22 is the product of the current exhaust flow rate and the pressure drop of a reference particle filter. The characteristic is that between the predicted differential pressure curve and the measured differential pressure curve 23 there are only slight differences in signal amplitude and phase difference, which corresponds to a high correlation between differential pressure curves 22, 23. This high correlation corresponds to an intact differential pressure sensor connected correctly. FIG. 3 shows a second diagram of the measured differential pressure curve 23 and the predicted differential pressure curve 22 on the particle filter 13 in the case of an open downstream connection 15.2 of the differential pressure sensor 15. The connection 15.2 has come off as a result of a defect with respect to the exhaust line 11 or the differential pressure sensor 15. For such a defect, the measured differential pressure 16 and the gradient as a function of time of the differential pressure signal increases significantly because the differential pressure sensor 15 only captures the differential pressure 16 on the particulate filter 13, but the measurement with respect to the ambient pressure and thus by comparison with a differential pressure sensor 15 correctly connected, it measures in addition the pressure drop on the muffler 17 or other unrepresented components of the exhaust gas system downstream of the particulate filter 13. Fig. 4 shows a third diagram of the measured differential pressure curve 23 and the predicted differential pressure curve 22 on the particle filter 13 in case of differential pressure 15 whose upstream branch is open. The upstream branch 15.1 has come off as a result of a fault in the exhaust line 11 or the differential pressure sensor 15. For this purpose, the differential pressure sensor 15 measures, in wide ranges, negative differential pressures 16 with a negative differential pressure gradient. In addition to the difference between the signal levels, there is also a phase shift between the predicted and the measured differential pressure curve 22, 23.
    [0011] Figure 5 shows a fourth diagram of the measured differential pressure curve 23 and the predicted differential pressure curve 22 in the case of a disassembled or defective particulate filter. In this case, the pressure drop between the connections 15.1, 15.2 is very small so that the measured differential pressure curve 23 and its gradient are significantly smaller than for the predicted differential pressure curve 22. FIG. a fifth diagram of the measured differential pressure gradient curve 33 and the predicted differential pressure gradient curve 32 in the case of a differential pressure sensor 15 whose downstream branch 15.2 is open. The curves shown correspond to a prolonged period with several variations of the differential pressure 16 on the particle filter 13, along the second time axis 30 and the differential pressure gradient axis 31.
    [0012] As the downstream branch 15.2 has come off the exhaust line 11 or the differential pressure sensor 15, the latter measures, as already described with reference to FIG. 3, with reference to FIG. the ambient pressure. The differential pressure gradients 33 measured in case of sufficiently high variations of the differential pressure 16 are thus significantly above the predicted differential pressure gradient 32. Thus there is no correlation or only a weak correlation between the curves. measured differential pressure gradients 33 and the predictive differential pressure gradients 32. According to the invention, the defect will be detected due to a lack of correlation between the curves of the measured and predicted differential pressure gradients 33, 32. A sixth diagram according to FIG. 7 shows the curve of the measured differential pressure gradient 33 and the predicted differential pressure gradient curve 32 in the case of an upstream open connection 15.1 of the differential pressure sensor 15. The curves are represented as a function of the second time axis 30 and of the diff pressure gradient axis As the branch before 15.1 is detached or damaged, as described with reference to FIG. 4, differential pressures 16 and differential pressure gradients 33, which are negative, are primarily measured. phase shift between the curves of the differential pressure gradients 32, 33. Thus, even for this defect, there is no correlation or only a weak correlation between the curves of the measured differential pressure gradients 33 and the pressure gradients predictive differential 32 which allows to note the defect according to the invention because of the lack of correlation. The diagnostic method according to the invention is thus based on the monitoring of the differential pressure sensor 15 and its connections 15.1, 15.2 by exploiting the correlation of the gradient curve as a function of time, of the differential pressure measured on the particulate filter 13 with respect to the predicted gradient versus time curve of the differential pressure 16 of a non-defective particulate filter 13. The predictive value is deduced from a model according to the current operating parameters of the heat engine 10. The main stages of the diagnosis will be described below. The low-pass filtering of the measured differential pressure signal is first performed to eliminate the noise. Then, the curve of the measured differential pressure gradient 33 d (Ap (k)) / dk is determined as a gradient as a function of time of the signal of the pressure sensor 15; the letter k corresponds to the measure of order k. For the same period, the corresponding curve of the predicted differential pressure gradient 32, namely d (Ap * (k)) / dk, is determined in that from the volume flow rate of the exhaust gas or its gradient as a function of time and the pressure drop of a non-defective particulate filter 13, the reference particle filter, the curve versus time of the predicted pressure difference gradient 32 of a non-defective particulate filter 13 is calculated. The predicted differential pressure gradient 32 or the exhaust gas flow rate thereof may also be optionally filtered by low pass filtering. Next, it is determined to what extent this is approximated by a normal cross-correlation of the curves of the measured differential pressure gradient 33 and the predicted differential pressure gradient 32. For this purpose, the cross correlation coefficient KKF is formed according to the following relationship: KKF = EMAp (k)) * (14p * (k) »I EMAp * (k)) * Cl (Ap * (k))) (1) In this formula, d (Apk (k)) / dk represents the gradient 33 the differential pressure measured in Figures 6 and 7; d (4r (k)) / dk represents the predicted differential pressure gradient 32 for different times characterized by the index k. The predicted differential pressure (4p * (4) is calculated with the product of the exhaust gas flow rate and the pressure drop R * of the intact particulate filter, to evaluate whether the differential pressure sensor 15 is correctly connected or if it functions correctly, the output value of the normal cross correlation, namely the cross correlation coefficient KKF, is compared with the thresholds recorded in the diagnosis unit 18 or in the main control of the motor. FIG. 8 shows a seventh diagram for the cross-correlation coefficients determined from the differential pressure gradients 32, 33 for different defects of the differential pressure sensor 15. A first cross correlation curve 42, a second cross correlation curve is deduced therefrom. 43, a third cross correlation curve 44 and a fourth cross correlation curve 45 with respect to a third time axis 40 and a correlation coefficient axis 41. A first range of correlation coefficients 46 and a second range of correlation coefficients 47 are also identified by double arrows along the axis of the correlation coefficients. .
    [0013] The second cross-correlation curve 43 is that of a non-defect particulate filter 13 and a differential pressure sensor 15 properly connected and operating properly. Under these conditions, the second cross-correlation curve 43 may lie in the first range of cross-correlation values 46. The third cross-correlation curve 44 has been measured in the case of a particulate filter 13, disassembled and removed. a differential pressure sensor 15 connected correctly and operating correctly. The second cross correlation curve 43 may be in the second range of cross correlation coefficients 47. The first cross correlation coefficient curve 42 is obtained if the downstream connector 15.2 of the differential pressure sensor 15 is detached or damaged. The correlation coefficients obtained are then significantly higher than that of the first range of cross-correlation coefficients 46, which makes it possible to guarantee the defects and to assign them only in a limited manner to the rear connection 15.2. The fourth cross-correlation curve 45 is obtained if the front connector 15.1 of the differential pressure sensor 15 is detached or damaged. The obtained correlation coefficients are significantly below the first cross-correlation coefficient range 46 and also below the second cross-correlation coefficient range 47. This thus ensures detection at the front connector 15.1. of the differential pressure sensor 15 and makes it possible to distinguish this defect and a defect of the downstream connection 15.2 or that of a particulate filter 13 integrated therein. For a strong correlation of the curves of the predicted and measured differential pressure gradients 32, 33 as is the case for a non-defective differential pressure sensor and a particulate filter 13, the cross correlation coefficient is of the order of 1 To detect a fault in the downstream connection 15.2, it is thus verified that the cross-correlation coefficient is significantly greater than 1 and in particular greater than 1.2. If the particle filter 13 is disassembled the cross correlation coefficients will be too low and in particular they will have values between 0.5 and -0.2. In order to detect a fault in the upstream connection 15.1, it is checked whether the cross-correlation coefficient is significantly lower than zero, especially less than -0.2. The method operates in a particularly reliable manner if there is some dynamic excitation, i.e. if the differential pressure gradients 32, 33 exceed a certain level. This is why it is advantageous to exploit cross-correlation only if certain dynamic criteria are met. This involves the gradients of the mass flow rate of the exhaust gas, the volume flow rate of the exhaust gas, the speed of the engine 10 or quantities derived therefrom. Ideally, to exploit a sufficient momentum, the differential gradient of the differential pressure is used directly. According to an alternative device, the differential pressure and its gradient as a function of time can also be measured from the signals supplied by two differential pressure sensors, each measuring the differential pressure with respect to the ambient pressure, or two absolute pressure sensors installed. upstream and downstream of the particulate filter 13. The diagnostic method thus makes it possible to check the upstream and downstream connections 15.1, 15.2 each connected to a separate pressure sensor. Advantageously in the process, the correlation over a prolonged period is determined for several variations in the volume flow rate of the exhaust gas and thus in the differential pressure 16. The safety of the diagnosis is thus increased for the exploitation of the measured gradient of the Differential pressure 33 for a single pressure variation and also for single measurements performed repeatedly. According to an advantageous development, the diagnostic process is recorded as a program in the diagnostic unit 18 and can be applied in particular to petrol engines with a petrol particle filter, but also to diesel engines.
    [0014] 10 NOMENCLATURE OF MAIN ELEMENTS 11 12 13 14 15 Heat engine Exhaust gas line Catalyst Particulate filter Exhaust gas stream Differential pressure sensor 15.1 Upstream connection 15.2 Downstream connection 16 Differential pressure / pressure difference 17 Exhaust system 18 Diagnosis unit 20 Time axis 21 Differential pressure axis 22 Predictive differential pressure curve 23 Measured differential pressure curve 32 Predicted differential pressure gradient curve 33 Differential pressure gradient curve measured 40 Third axis of time 41 Axis of correlation coefficients 42 First curve of cross correlation coefficient 43 Second curve of cross correlation coefficient 44 Third curve of cross correlation coefficient 45 Fourth curve of cross correlation coefficient 46 First range of cross correlation coefficients 47 Second range of cross correlation coefficients30
    权利要求:
    Claims (11)
    [0001]
    CLAIMS 1 °) A method of diagnosing a differential pressure sensor (15) which determines a differential pressure (16) of an exhaust aftertreatment unit installed in an exhaust pipe (11) and forming part of an exhaust cleaning system of a heat engine (10), which sensor is connected by an upstream connection (15.1) to the exhaust pipe (11) upstream of the unit exhaust gas after-treatment and a downstream connection (15.2) to the exhaust gas pipe (11) downstream of the exhaust after-treatment unit, the diagnosis being made on the basis of the comparison of a gradient (33) as a function of time of the measured differential pressure (16) as a result of a variation of the exhaust gas pressure upstream of the gas aftertreatment unit. escape and a gradient as a function of time (32) of the differential pressure a process, characterized in that the correlation between the gradient curve (33) of the measured differential pressure and that of the gradient curve (32) of the predicted differential pressure is determined, and for a high correlation it is concluded that the sensor differential pressure (15) is not defective and its connections (15.1, 15.2) are not defective, and for a weak correlation it is concluded that a differential pressure sensor (15) is defective or has a defect one or both of its branches (15.1, 15.2).
    [0002]
    Method according to claim 1, characterized in that the correlation is determined and exploited for at least two or more variations of the exhaust gas pressure.
    [0003]
    3) Method according to claim 1, characterized in that by forming a standardized cross-correlation from the gradient curve (33) of the measured differential pressure and the predicted differential pressure gradient curve (32) one forms a cross-correlation coefficient, and the correlation between the measured curve and the predicted differential pressure gradient curve (33, 32) is exploited using the cross-correlation coefficient.
    [0004]
    Method according to Claim 1, characterized in that it is concluded that the differential pressure sensor (15) has a damaged or interrupted downstream connection (15.2) if the cross-correlation coefficient exceeds a first predefined correlation threshold, preferably greater than a first cross-correlation coefficient greater than one and particularly preferably greater than a first correlation threshold higher than 1.2 and / or it is concluded that the upstream connection (15.1) of the pressure sensor has been damaged or cut off differential (15) if the cross-correlation coefficient is less than a second correlation threshold preferably less than a second correlation threshold of less than 0 and particularly preferably less than a second correlation threshold of less than -0, 2.
    [0005]
    Method according to Claim 1, characterized in that the predicted differential pressure curve is determined at least from the volume flow rate of the exhaust gases through the exhaust after-treatment unit and the pressure drop of the aftertreatment unit of the exhaust gas.
    [0006]
    Process according to Claim 1, characterized in that the measured differential pressure (16) is filtered on the exhaust aftertreatment unit and / or the predicted differential pressure on the aftertreatment unit. exhaust gas treatment and / or volume flow rate of the exhaust gas to determine the predicted differential pressure.
    [0007]
    Method according to Claim 1, characterized in that the diagnosis is carried out only if the differential pressure gradient (32, 33), preferably the predicted differential pressure gradient (32) or a measurement correlated with the gradient. differential pressure (32, 33) exceeds a predefined value.
    [0008]
    Process according to Claim 1, characterized in that the differential pressure sensor (15) determines the differential pressure (16) on a particulate filter (13).
    [0009]
    9 °) Application of the method according to any one of claims 1 to 8, a gasoline engine (10) wherein the installation of the exhaust gas comprises at least one catalyst (12) and a particulate filter ( 13), a catalyst or particle filter combination or a catalytically coated particle filter.
    [0010]
    A diagnostic unit (18) for diagnosing a differential pressure sensor (15) for determining a differential pressure (16) of an exhaust aftertreatment unit of a gas cleaning plant. exhaust in the exhaust line (11) of a heat engine (10), the diagnostic unit (18) receiving the measurement signals of the differential pressure sensor (15), and the diagnostic unit (18) forming a measured differential pressure gradient (33) from the measured differential pressure (16) and determining a predictive differential pressure gradient (32) from at least one volume flow rate of the exhaust gas passing through the exhaust aftertreatment unit and the pressure drop of the exhaust aftertreatment unit, a diagnostic unit (18) characterized in that it comprises an electrical circuit or a program to execute the process itself according to any of claims 1 to 8.
    [0011]
    11 °) diagnostic unit (18) according to claim 10, characterized in that it is constituted by a separate component or a component integrated in the main control of the engine.
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    公开号 | 公开日
    DE102014209718A1|2015-11-26|
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    CN105089758A|2015-11-25|
    CN105089758B|2019-02-26|
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    法律状态:
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    2022-02-11| ST| Notification of lapse|Effective date: 20220105 |
    优先权:
    申请号 | 申请日 | 专利标题
    DE102014209718.5|2014-05-22|
    DE102014209718.5A|DE102014209718A1|2014-05-22|2014-05-22|Method and diagnostic unit for diagnosing a differential pressure sensor|
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