DE102014201138B4 - Method for detecting faulty sensors in an exhaust system of a motor vehicle and motor vehicle suitable for carrying out this method - Google Patents

Abstract

Detection method (30), in which in an exhaust line (12) of a motor vehicle (10) by means of a first sensor (19) in an upward detection (33) at a first measuring point (21) an upward value (U) is determined by means of a second sensor (20) in a downward determination (34) at a second measuring point (22) a downward value (D) is determined, a first product (P1) of the upward value (U) and the downward value (D) formed in a first product formation (35) is formed, a second product (P2) from the upward value (U) with itself or from the downward value (D) with itself in a second product formation (36), a ratio (V) from the first product (P1) and the ratio (V) in a ratio score (40) is checked for whether it lies in a predefined range and an error message (41) is generated if the ratio (P) is determined in a ratio determination (39). V) outside the front defined range, characterized in that the ratio (V) is determined from a sum of a predetermined number (n) of first products (P1) and a sum of the predetermined number (n) of second products (P2).

Description

The present invention relates to a method for detecting faulty sensors in an exhaust system of a motor vehicle and to a motor vehicle.

The sensors in exhaust gas lines of motor vehicles are exposed to high loads. Due to high temperatures and aggressive exhaust components, there are difficult conditions for the sensors, which could impair the function of the sensors after some time.

The DE 10 2009 010 307 A1 shows an exhaust gas treatment device for an internal combustion engine with a first particulate filter and arranged in the flow direction of the exhaust gas through the exhaust gas treatment device downstream of the first particulate filter second particulate filter. The second particle filter comprises at least one carrying device through which the exhaust gas can flow, on which a filter unit is arranged, wherein a pore size of the filter unit is smaller than a pore size of the at least one carrying device. By means of pressure sensing means, a ratio of a difference in pressure between a location upstream of the second particulate filter and a location downstream of the second particulate filter is detected to a difference in pressure between a location upstream of the first particulate filter and a location downstream of the first particulate filter. A ratio determined on the basis of the pressure detecting means can be compared by means of an evaluation device with a ratio stored in a memory and evaluated with regard to a state of the first particle filter. A damage of the first particulate filter is closed by means of the evaluation device when the ratio determined on the basis of the pressure sensing means increases again during the operation of the exhaust gas treatment device.

From the DE 10 2006 055 563 B3 The object of the invention is a method and a device which are intended to enable the reliable estimation and correction of nominal value deviations of the fuel quantity injected in an internal combustion engine while avoiding time delays. In the method, a plurality of times, in each case one pair of values consisting of a nominal value of the injected fuel quantity and a calculated value for the actually injected fuel quantity, are determined, the calculated value being calculated on the basis of other measured variables. On the basis of the determined pairs of values, a characteristic value for characterization, a setpoint deviation of the fuel quantity injected in the internal combustion engine is calculated using the least squares method. The setpoint deviation is corrected on the basis of the characteristic value. In the event that an R ² value (= coefficient of determination) obtained using the least-squares method falls below a predetermined threshold value, the operating behavior of the injection device is classified as defective and the driver is informed of the need for a burning-off phase and / or an exchange of the injection device.

The DE 696 15 768 T2 discloses an apparatus for determining an abnormal degree of deterioration of a catalyst disposed in an engine exhaust system. This comprises a measuring device for measuring a temperature of the catalyst; Accepting means for accepting a temperature of the catalyst based on the engine operating condition, calculating means for calculating a ratio of a variable value of the temperature measured by the meter and a temperature adopted by the acceptor; and determining means for determining that the degree of deterioration of the catalyst is abnormal when the ratio is smaller than a predetermined value.

The DE 199 44 009 A1 proposes a method for operating an SCR catalyst in the exhaust tract of an internal combustion engine. With the knowledge that the efficiency of the SCR catalyst depends inter alia on the Reduktionsmitteldosierung, the actual efficiency, for example, from NOx concentrations upstream and downstream of the SCR catalyst is determined and compared with an operating-dependent target efficiency to the reducing agent metering so control that the actual efficiency reaches the target efficiency. The actual efficiency is determined by a ratio formation of the NOx concentration upstream and downstream of the SCR catalyst. The desired efficiency results from the NOx content upstream of the SCR catalyst and its operating temperature and is taken from a suitable map.

The US Pat. No. 6,397,583 B1 shows a method and system for monitoring the performance of a catalytic converter coupled to an exhaust of an internal combustion engine fueled from a fuel tank, the fuel having a first and a second fuel in varying proportions. A ratio indicating a catalyst exhaust gas conversion efficiency is defined by signals of an exhaust gas sensor arranged upstream and downstream of the catalyst. A threshold indicative of non-functioning of the catalyst is adjusted depending on the concentration of one of the first and second fuels in the fuel tank.

From the US 2011/0 252 767 A1 For example, a method is disclosed that includes increasing a temperature of an SCR catalyst for a predetermined period of time during metering of urea. The method further includes maintaining the temperature of the SCR catalyst without metering urea for a second predetermined period of time. The method further includes filtering out at least low-frequency data of a first NOx sensor upstream of the SCR catalyst and a second NOx sensor downstream of the SCR catalyst, and comparing the filtered data of the first NOx sensor and the second NOx sensor without the metering of urea over a third predetermined period of time. The method further includes providing a NOx sensor state index for at least one of the NOx sensors in response to the comparison.

The DE 695 19 274 T2 discloses a system for monitoring the efficiency of a catalytic converter of a motor vehicle. In this case, the efficiency of a catalytic converter is evaluated on the basis of output signals from two lambda probes, which are arranged upstream or downstream of the catalytic converter. More specifically, a signal obtained by calculating the difference between the time-averages obtained by integration and then dividing for the duration of an integration window of the output signals of these probes is used as the signal indicative of the efficiency.

The US 2011/0 143 449 A1 proposes a system for detecting the presence of a catalyst comprising an exhaust pipe, a first temperature sensing device, a second temperature sensing device, a flow rate measuring device, and a processing device. The first temperature detecting device measures a first temperature of the exhaust gas upstream of the exhaust pipe. The second temperature detecting device measures a second temperature of the exhaust gas downstream of the exhaust pipe. The processing apparatus estimates an expected time delay between the measured inlet and outlet exhaust temperatures, corresponding to a system with catalyst. The processing device may also determine the presence of a catalyst by comparing the measured second temperature with the measured first temperature and comparing the measured second temperature with an estimated delayed first temperature in conjunction with the expected time delay.

From the DE 101 12 139 A1 shows a method and a device for monitoring a sensor. In this case, a first signal of a first sensor to be monitored is compared with a second signal of a second sensor, and detected for errors when at least the two signals differ by more than a predetermined value. This procedure is also proposed for controlling the exhaust aftertreatment system, preferably for sensors for detecting the state of the exhaust aftertreatment system and / or for pressure, temperature and / or air quantity sensors.

The present invention has for its object to provide a method and a motor vehicle, with which a malfunction of a sensor in an exhaust line of the motor vehicle can be detected early.

This object is achieved with a recognition method according to claim 1 and a motor vehicle according to claim 9. Advantageous developments of the invention are specified in the subclaims and described in the description.

In the detection method according to the invention, an upward value is determined in an exhaust gas train of a motor vehicle by means of a first sensor in an upward value determination at a first measuring point and by means of a second sensor in a downward value determination at a second measuring point. From the up value and the down value, a first product is formed in a first product formation. A second product is formed from the up value with itself or from the down value with itself in a second product formation. Thereafter, a ratio is determined from the first product and the second product in a ratio determination. This ratio is then checked in a ratio evaluation to see if it is in a predefined range. If the ratio is outside the predefined range, an error message is generated.

This advantageously provides a method with which a malfunction of the sensors in the exhaust gas line can be determined in a simple and reliable manner. Regardless of driving behavior, faulty sensors can be detected.

According to the invention, in the recognition method, the ratio is determined from a sum of a predetermined number of first products and a sum of the predetermined number of second products.

This improves the accuracy of the method according to the invention. Individual outliers are less significant.

In a further advantageous embodiment of the recognition method according to the invention the down-value is determined delayed to the up-value.

Thus, the up-value and the down-value can be determined at the same position of the mass flow flowing through the exhaust gas line. Changing operating conditions of the engine can thus be hidden.

In a further advantageous embodiment of the recognition method according to the invention, the upward value or the downward value is multiplied by a compensation factor.

Thus, principle-related different states at the two measuring points can be taken into account. The predefined area in which the ratio should lie lies around the one. An evaluation of measured values of different sizes is thus clearer.

In a further advantageous embodiment of the recognition method according to the invention, in each case a value for a pressure is determined in the ascertaining of ascending value and in the ascertaining of ascending value.

Thus, the inventive method can be used in the monitoring of pressure sensors.

In an alternative embodiment of the detection method according to the invention, in each case a value for a temperature is determined in the ascertaining of the ascertaining value and in the ascertaining of the downward value.

Thus, the method according to the invention can be used in the monitoring of temperature sensors.

In a further alternative embodiment of the recognition method according to the invention, in each case a value for a substance content is ascertained in the ascertaining of the upward value and in the determination of the downward value. In particular, the substance content of oxygen or of a nitrogen oxide is determined.

Thus, the inventive method can be used in the monitoring of material sensors, such as lambda probes.

The motor vehicle according to the invention comprises an engine, an exhaust system, a first sensor arranged in the exhaust system, a second sensor arranged in the exhaust system downstream of the first sensor, and an evaluation unit connected to the first sensor and the second sensor. In this case, the evaluation unit is designed in such a way to carry out the method according to the invention in all its embodiments.

The motor vehicle according to the invention benefits from the advantages of the recognition method according to the invention.

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below. Show it:

1 a motor vehicle according to the invention; and

2 an inventive detection method.

In the 1 is an example of a motor vehicle according to the invention 10 outlined. The car 10 includes a motor 11 and an exhaust system 12 in the operation of the engine 11 derived exhaust gases. In addition, the motor vehicle includes 10 at least a first sensor 19 at a first measuring point 21 and a second sensor 20 at a second measuring point 22 in the exhaust system 12 and one with the two sensors 19 . 20 signal-conducting connected evaluation unit 18 ,

That in the 1 shown motor vehicle 10 has only four wheels as an example 13 on. The car 10 can be single-lane or multi-lane. The motor 11 of the motor vehicle 10 is an internal combustion engine in the sense of the present invention. The motor 11 may be suitable for a self-ignition principle or a Fremdzündprinzip. In addition, the engine can 11 with an exhaust gas turbocharger 14 be provided.

The exhaust system 12 of the motor vehicle 10 can be next to the two sensors 19 . 20 conversion devices 14 . 15 . 16 . 17 for example, for an exhaust aftertreatment or an energy extraction or addition or a substance removal or addition. In the 1 has the motor vehicle 10 for example, a nitrogen oxide storage catalyst 15 , a particle filter 16 and a nitric oxide reduction catalyst 17 on.

The measuring points 21 . 22 are spaced from each other. This is the first measuring point 21 upstream of the second measuring point 22 arranged or is the second measuring point 22 downstream of the first measuring point 21 arranged. Between the measuring points 21 . 22 , ie downstream of the first measuring point 21 and upstream of the second measuring point 21 may be a conversion device 14 . 15 . 16 . 17 be arranged in the exhaust system. In the 1 is an example of the first measuring point 21 downstream of the engine 11 and upstream of the nitrogen oxide storage catalyst 15 arranged and the second measuring point 22 is downstream of the particulate filter 16 and upstream of the bead oxide reduction catalyst 17 arranged.

The first sensor 19 and the second sensor 20 are for the purposes of the present invention designed to measure the same size. The first sensor 19 and the second sensor 20 are in particular temperature sensors 19 . 20 , and / or substance concentration sensors 19 . 20 , in particular for nitrogen oxides and / or oxygen, for example λ sensors 19 . 20 , The sensors 19 . 20 can also pressure sensors 19 . 20 or sensors 19 . 20 be different state variables. The sensors 19 . 20 can also in this application, probes 19 . 20 Transducers 19 . 20 , Sensor 19 . 20 , Measuring heads 19 . 20 or measuring devices 19 . 20 be.

The sensors 19 . 20 are with the evaluation unit 18 signal-conducting connected. The evaluation unit 18 In particular, an engine control unit 18 of the motor vehicle 10 be.

In the 2 is an example of a recognition method according to the invention 30 in a diagram of startup 31 until the end 42 shown. In the recognition process 30 become an up-value determination in a single cycle 33 , a down-value determination 34 , a first product formation 35 and a second product formation 36 carried out.

The number n of cycles is greater than one. In the 2 the cycle is shown in a loop starting from an index 32 the index i after each cycle in an index increase 38 increased by one, until the number n is reached, which by an index check 37 is shown.

In the upward valuation 33 becomes an up-value U and in down-value determination 34 a down-value D is determined. The up-value determination 33 takes place at the first measuring point 21 and the down-value determination 34 takes place at the second measuring point 22 instead of. From the obtained values U, D are then in the context of the first product formation 35 a first product P1 and as part of the second product formation 36 formed a second product P2. The first product P1 is formed of the upward value U and the downward value D. The second product P2 is the up-value U squared or the down-value D squared.

The up-value U and / or the down-value D can be used in the product formations 35 . 36 additionally be supplemented with a compensation factor F. The compensation factor F is a predefined value. The compensation factor F can vary depending on the operating condition of the engine 11 or as a function of the operating state of the exhaust gas line 12 vary. With the compensation factor F, the upward value U or the downward value D is adjusted to the respectively other downward or upward value D, U. In this way, deviating values D, U can be compensated, which result from different states in the first measuring point 21 and the second measuring point 22 result. With the compensation factor F, the applied value D, U is calibrated.

In addition or as an alternative to loading one of the values D, U with the compensation factor F, it is possible to ascertain the upward value 33 and the down-value determination 34 time-delayed.

After the product formations 35 . 36 the products P1, P2 are in a ratio determination 39 each other in a ratio V set. The sums Σ of the products P1, P2 are set to ratio V with each other. In the 2 For example, the ratio V is exemplified by the sum Σ of the first products P1 as a dividend and the sum Σ of the second products P2 as a divisor. The ratio V can also be formed from the sum Σ of the second products P2 as a dividend and the sum Σ of the first products P1 as a divisor.

After the ratio determination 39 will be a ratio assessment 40 carried out. In the ratio assessment 40 it is checked whether the ratio V is in a predefined range or outside the predefined range. The predefined range is determined by a lower threshold value A and an upper threshold value B. The ratio V is in the predefined range when the ratio V is greater than or equal to A and at the same time V is less than or equal to B. For example, the predefined range is between A = 0.95 and B = 1.05.

Returns the ratio assessment 40 in that the ratio V is outside the predefined range when the ratio V is smaller than A or greater than B becomes an error message 41 generated.

The recognition method according to the invention 30 is from the evaluation unit 18 carried out. The by means of the sensors 19 . 20 ascertained upward value 33 or downwards value 34 may be, for example, a value for a pressure, a temperature or a substance content.

LIST OF REFERENCE NUMBERS

10

 motor vehicle

11

 engine

12

 exhaust gas line

13

 wheel

14

 turbocharger

15

 Nitrogen oxide storage catalyst

16

 particulate Filter

17

 Sickoxidreduktionskatalysator

18

 evaluation

19

 First sensor

20

 Second sensor

21

 First measuring point

22

 Second measuring point

30

 detection methods

31

 begin

32

 Index setting

33

 Upward valuation

34

 Downward valuation

35

 First product formation

36

 Second product formation

37

 index check

38

 Index increase

39

 ratio determination

40

 money Rating

41

 error message

42

 The End

i

 index

n

 number

U

 up value

D

 down value

F

 compensation factor

Σ

 total

P1

 First product

P2

 Second product

V

 relationship

A

 Lower threshold

B

 Upper threshold

Claims (9)

Detection method ( 30 ), in which in an exhaust line ( 12 ) of a motor vehicle ( 10 ) by means of a first sensor ( 19 ) in an upward value determination ( 33 ) at a first measuring point ( 21 ) an upward value (U) is determined by means of a second sensor ( 20 ) in a down-value determination ( 34 ) at a second measuring point ( 22 ) a down-value (D) is determined, a first product (P1) from the up-value (U) and the down-value (D) in a first product formation ( 35 ), a second product (P2) from the upward value (U) with itself or from the downward value (D) with itself in a second product formation ( 36 ), a ratio (V) of the first product (P1) and the second product (P2) in a ratio determination ( 39 ), the ratio (V) is determined in a ratio ( 40 ) is checked to see if it is in a predefined area and an error message ( 41 ) is generated when the ratio (V) is outside the predefined range, characterized in that the ratio (V) is calculated from a sum of a predetermined number (n) of first products (P1) and a sum of the predetermined number (n ) is determined by second products (P2). Detection method ( 30 ) according to claim 1, wherein the downwards value (D) is determined with a time delay to the upwards value (U). Detection method ( 30 ) according to Claim 1 or 2, in which the upward value (U) or the downward value (D) is multiplied by a compensation factor (F). Detection method ( 30 ) according to one of claims 1 to 3, in which in the upward value determination ( 33 ) and in the down-value determination ( 34 ) is determined in each case a value for a pressure. Detection method ( 30 ) according to one of claims 1 to 3, in which in the upward value determination ( 33 ) and in the down-value determination ( 34 ) in each case a value for a temperature is determined. Detection method ( 30 ) according to one of claims 1 to 3, in which in the upward value determination ( 33 ) and in the down-value determination ( 34 ) in each case a value for a substance content is determined. Detection method ( 30 ) according to claim 6, wherein the substance content of oxygen is determined. Detection method ( 30 ) according to claim 6, wherein the substance content is determined by a nitric oxide. Motor vehicle ( 10 ) with a motor ( 11 ), an exhaust gas line ( 12 ), one in the exhaust system ( 12 ) arranged first sensor ( 19 ), one in the exhaust system ( 12 ) downstream of the first sensor ( 19 ) arranged second sensor ( 20 ) and one with the first sensor ( 19 ) and with the second sensor ( 20 ) signal-conducting connected evaluation unit ( 18 ), whereby the evaluation unit ( 18 ) is formed in the manner, the method ( 30 ) according to one of the preceding claims 1 to 8.

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