How to Identify a Load Disconnect Error

Abstract

A method for identifying a load release error of a wideband lambda sensor (112) configured for detecting at least one characteristic of exhaust gas in an exhaust gas chamber of a motor vehicle, the wideband lambda sensor (112) further comprising at least one heater, the method comprising the steps of a) enabling an error check, checking whether the wideband lambda sensor (112) is sufficiently heated using a temperature model, and b) performing an error check, where if no error is identified after the error check, the next step is performed, b1) terminating the method with an i.O. result, and if an error is identified after the error check, the next step is performed, b2) terminating the method with an ni.O. result, and before performing step b), a check is performed for the need for overheating prevention, and if the need for overheating prevention exists, the heater voltage of the heater is reduced simultaneously with or before performing step a).

Description

[Technical Field]

[0001] Prior art To comply with exhaust gas regulations, lambda sensors are used in internal combustion engines. Lambda sensors are generally known, for example, from Konrad Reif (Hrsg.): "Sensoren im Kraftfahrzeug", 1st Edition (1. August), 2010, pp. 160-165. Wideband lambda sensors are used in both Otto and diesel systems. The measured lambda signal can be used for many functions in the control unit, for example, to improve exhaust gas aftertreatment and to monitor the efficiency of three-way catalytic converters. [Background technology]

[0002] Wideband lambda sensors can determine the oxygen concentration in exhaust gases over a wide range. The measured lambda value can define the actual air-fuel ratio relative to the stoichiometric air-fuel ratio. Wideband lambda sensors typically deliver a continuous lambda signal unambiguously in the range from 0.7 to air. Wideband lambda sensors usually have individual ceramic films stacked one above the other. Wideband lambda sensors are typically heated electrically because they only function at a sufficiently high operating temperature of the sensor ceramic. To ensure the required ceramic temperature can be reached as quickly as possible, heater elements are usually integrated between the ceramic layers. Wideband lambda sensors typically only become operational above a certain ceramic temperature, which falls within the tolerance range of the wideband lambda sensor specified in the customer's technical documentation. The signal provided by the wideband lambda sensor is typically evaluated via a special evaluation module (ASIC) integrated into the control unit. A digital or digital / analog module is typically used here. A pumping current proportional to the oxygen concentration in the exhaust gas can flow between the outer pumping electrode of the wideband lambda sensor and the evaluation module. If the exhaust gas mixture is lean, the pumping current is essentially positive, and if the mixture is rich, the pumping current is negative. In ideal conditions, i.e., when the lambda ratio is 1, the pumping current is essentially 0. The evaluation module typically evaluates the measured current and delivers an output voltage for further processing in the control unit.

[0003] The wideband lambda sensor may include, in particular, a cable harness, a connector, and an evaluation module that includes a separate output stage for the sensor heating and a software component driver for operating the wideband lambda sensor and for providing a physical lambda signal for the lambda-based functions of the control device. To achieve optimal utilization, the lambda-based functions of the control device essentially require a lambda signal that is extremely valuable in terms of quality over the entire service life. Since the wideband lambda sensor essentially has a decisive influence on exhaust gas emissions, various diagnostic functions are essentially required that may include, in particular, diagnostics of the cable connection, diagnostics of the output stage, diagnostics of the heating power of the sensor heater, diagnostics of signal availability and loop closure time, and / or diagnostics of symmetrical and asymmetrical dynamics errors (filters and delays).

[0004] In part, the diagnosis of the cable connection can only be expressed by evaluating the internal resistance ratio of the wideband lambda sensor, so for open load diagnosis (identification of cable break), the sensor ceramic must be above a certain operating temperature.

[0005] The heating power diagnosis can also be based on the temperature derived from the resistance of the sensor ceramic. Therefore, it is essentially impossible to distinguish unambiguously whether the resistance of the sensor ceramic is outside the measurable range (possible heater error) or whether an open circuit exists. Currently, the open-load diagnosis is enabled by a sensor temperature model. This model essentially ensures that, on the one hand, the weaker heater or WPA heater (Worst Performance Acceptable heater) has already heated up to a temperature sufficient for robust on-site diagnosis, and, on the other hand, that overheating of the more powerful heater (BP heater or Best Performing heater) is essentially precluded for component protection reasons. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Konrad Reif (Hrsg.): “Sensoren im Kraftfahrzeug”, 1st edition (1. Aufl.), 2010, pp. 160-165 Summary of the Invention [Problem to be solved by the invention]

[0007] Disclosure of the Invention Therefore, a method for identifying load-release errors in a wideband lambda sensor, a system including at least one wideband lambda sensor and at least one control unit, a computer program, and a data carrier are proposed, which at least largely avoid the above-mentioned disadvantages of known devices and methods. In particular, the conflict between the objectives of identifying a cable break in a signal line and a heating output error can be resolved. Furthermore, overheating prevention can be simultaneously ensured, taking into account high manufacturing tolerances. [Means for solving the problem]

[0008] In a first aspect of the present invention, a method for identifying a load-release error in a wideband lambda sensor configured to detect at least one characteristic of exhaust gases in an exhaust gas chamber of a motor vehicle is proposed. The wideband lambda sensor has at least one heater. The term "wideband lambda sensor" basically refers to any device configured to supply actual measurement data to an engine control unit in the exhaust gas chamber of a gasoline or diesel engine, in particular to reduce the harmful substance content in the exhaust gas. In particular, the wideband lambda sensor can be configured to determine the residual oxygen content in the exhaust gas. In this way, the engine control unit can optimize the fuel mixture accordingly. Basically, the method for identifying a load-release error involves the use of a jump sensor and a NOx sensor. x It is also suitable for sensors, in which case the temperature signal can be determined via evaluation of the ceramic resistance.

[0009] The term "heater" basically refers to any element that is configured to bring the wideband lambda sensor to the required operating temperature immediately after a cold start. This basically ensures an emission-optimized operation even during the engine warm-up phase. A "cold start" basically refers to the start of a vehicle without preheating. In particular, all components of the vehicle, in particular all components, may have the same temperature level during start-up. In particular, all temperature sensors of the vehicle, in particular all temperature sensors, may have the same temperature level. In particular, the wideband lambda sensor may have a temperature of less than 50° C. during a cold start.

[0010] The method according to the present invention is an on-board diagnostic (OBD) for monitoring compliance with emission limits, in particular legally mandated emission limits. If an error in the system could result in non-compliance with exhaust gas limits, the error can be identified and entered into an error memory of the control device. As described above, the method according to the present invention is a method for identifying open-load errors. Therefore, the method can also be referred to as an open-load diagnostic. The open-load diagnostic can correspond to identifying a broken cable.

[0011] The method comprises the steps listed below. The method may also comprise other steps not listed here. These steps may be carried out at least partially repeatedly, in particular one after the other.

[0012] The method comprises the following steps: a) enabling an error check, which checks whether the wideband lambda sensor (112) is sufficiently heated using a temperature model; b) performing error checking; Including, If no errors are identified after error checking, the next step is to b1) i.O. Terminating the method using the results is executed, If an error is identified after error checking, the next step is to b2) niO. Terminating the method with the results is executed, Before step b) is performed, a check is made to see if overheat protection is necessary, and if there is a need for overheat protection, the heater voltage of the heater is reduced simultaneously with step a) or before step a) is performed.

[0013] The method may in particular be a computer-implemented method. The term "computer-implemented" may in particular refer to a process that is fully or partly implemented using data processing means, in particular using at least one processor.

[0014] The concept of "enabling" basically refers to a process of authorizing the execution of a method step if certain conditions exist. After enabling, the method step can be executed. If enabling does not occur, the method step is not executed. During the error check enabling in step a), it can be checked in particular whether the operating temperature of the wideband lambda sensor, as determined by the temperature model, has exceeded a predetermined limit value.

[0015] The concept of "overheat protection" basically refers to a safety function of the wideband lambda sensor. As the heater voltage of the heater increases, the heat generation of the heater coil and therefore of the wideband lambda sensor may also increase. If the temperature of the heater or the wideband lambda sensor exceeds a predetermined limit value, the need for overheat protection may arise.

[0016] In the error check in step b), the measured internal resistance can be compared with a diagnostic threshold. In the case of double-cell sensors, particularly wideband double-cell sensors, the internal resistance between the following signal lines can be considered: the internal resistance between the APE (external pumping electrode) and the IPN (internal pumping electrode and Nernst electrode) and the internal resistance between the RE (reference electrode) and the IPN. In the case of single-cell sensors, particularly wideband single-cell sensors, the internal resistance between the following signal lines can be considered: the internal resistance between the APE and the IPN. In this regard, if multiple consecutive individual measurements are performed for robust error identification, the time characteristics of the signal can be taken into account.

[0017] As mentioned above, if no error is identified after the error check, the method ends with an "i.O. result." The concept of i.O. result may particularly refer to an i.O. system (a "normal" system). The i.O. system may particularly be an error-free system, in which case there is no definition of a new, running-in, aging, or other state.

[0018] As mentioned above, if an error is identified after the error check, the method ends based on the "nO.result." The concept of "nO.result" may particularly refer to a nO.system (a "bad" system). The nO.system may particularly be a system having an error, and in this case, there are definitions of states such as new, running-in, and aging.

[0019] As mentioned above, in step a) a temperature model is used to check whether the wideband lambda sensor is sufficiently heated.

[0020] The temperature of a wideband lambda sensor can essentially only be calculated if the wideband lambda sensor is brought into the required temperature operating window by a heater, in particular a sensor heater, i.e., a window starting from approximately 550°C for the sensor ceramic of the wideband lambda sensor. The temperature operating window of approximately 550°C essentially corresponds to the current state of the art, but in some cases may be lower. Since there are essentially no means by which the temperature of a wideband lambda sensor can be calculated during the heating process of the wideband lambda sensor, a temperature model can be configured to calculate the amount of energy and / or heat introduced into the wideband lambda sensor by the heater. The temperature model can take into account the actual battery voltage of the vehicle and / or the duty cycle of the heater output stage. Based on these quantities, it is possible to calculate the temperature that will be reached for the wideband lambda sensor.

[0021] The temperature model can be based on various state variables. These may be, in particular, temperature and / or energy. For energy balances, in particular in the form of energy or temperature, the transfer of electrical energy of the heater and / or at least one other energy can be taken into account, possibly in a generalized manner, for all transfer forms. Possible transfer forms are essentially thermal radiation, convection and / or conduction. Depending on the model design, these transfer forms can also result in cooling (in the case of low ambient temperatures) or heating (in the case of high ambient temperatures) of the wideband lambda sensor. Furthermore, a cooling model can be provided for initialization after start-up of the control device.

[0022] The temperature model can be selected from the group consisting of a WPA model, a BP model, and a WPA / BP model.

[0023] The BP model (Best Performance model) is essentially an error-free system, which may have the lowest heater resistivity, especially in response to manufacturing tolerances.

[0024] The WPA model (Worst Performance Acceptable model) can in particular be an aged but error-free system, i.e. a system that is still able to accurately comply with emission limits. This can in particular be a vehicle approaching the end of its useful life. Based on the aged system, essentially all verification measurements required for authority verification on an error-containing system are also carried out.

[0025] One difference between the BP and WPA models can be in the initialization after restart. The WPA model allows for faster cooling due to existing robustness. The BP model allows for slower cooling in the event of overheating due to safety. Also, heater resistance differences of over 50% between the cold and hot states can be typical.

[0026] The WPA / BP model may specifically be a combination of the BP model and the WPA model.

[0027] In a first variant, the temperature model may in particular have two functions: on the one hand, it can be configured to calculate the minimum energy threshold required for the implementation of the method according to the invention, and, furthermore, it can be configured to prevent overheating of the wideband lambda sensor.

[0028] In a first variant, the temperature model can be a WPA / BP model. The WPA / BP model can be used to check whether the wideband lambda sensor is sufficiently heated. Furthermore, the WPA / BP model can be used to check the need for overheating protection.

[0029] In a first variant, the heater voltage of the heater can be reduced simultaneously with step a), in particular simultaneously with enabling the error check, and depending on the selected reduced effective heater voltage, the debouncing time can be extended.

[0030] In a second variant, the temperature model, in particular the temperature model in step a), can be a WPA model. The need for overheating protection can be checked using another temperature model. In particular, this other temperature model can be a BP model. Separate modeling of the WPA model for enabling error checking and the BP model for overheating protection provides an additional degree of freedom, allowing for a wider variation in heater resistance to be taken into account. This is particularly important when the WPA heater has not yet reached a sufficiently high temperature to perform robust diagnostics, while the BP heater is already in danger of overheating.

[0031] In another aspect of the invention, a system is proposed, comprising at least one wideband lambda sensor and at least one controller, the controller comprising at least one processor, the controller being configured to perform the method steps according to the methods described above or further below.

[0032] In another aspect of the invention, a computer program is proposed which, when executed on a computer or on a computer network, is arranged to carry out the method described above or further below.

[0033] In another aspect of the invention, a computer program is proposed having program code means, the computer program being arranged to perform the method set out above or further described below when the computer program is run on a computer or on a computer network.

[0034] In another aspect of the invention, a data carrier is proposed having stored thereon a data structure, the data structure being configured to perform the method described above or further below after being loaded into the operating memory and / or main memory of a computer or computer network.

[0035] In another aspect of the invention, a computer program product is proposed comprising program code means stored on a machine readable carrier for performing the methods set out above or further described below when the program is run on a computer or on a computer network.

[0036] In this case, a computer program product is understood to mean a program available for sale. A computer program can essentially be in any form, and therefore can be, for example, on paper or on a computer-readable data carrier, and can in particular be distributable via a data transmission network. In particular, program code means can be stored on a computer-readable data carrier and / or a computer-readable storage medium. The terms "computer-readable data carrier" and "computer-readable storage medium" used in this specification can in particular refer to non-transitory data storage devices, for example hardware data storage media on which instructions executable by a computer are stored. A computer-readable data carrier or a computer-readable storage medium can in particular be or include a storage medium such as a random access memory (RAM) and / or a read-only memory (ROM).

[0037] In another aspect of the invention, a modulated data signal is proposed which comprises instructions executable by a computer system or computer network for carrying out the methods described above or further below.

[0038] The method according to the invention and the device according to the invention have many advantages over known methods and devices, in particular, they can resolve the conflict between identifying a cable break and a heating power error by clearly distinguishing between a cable error on the sensor side and an error that occurs when reducing the heating power on the sensor heater side.

[0039] The requirements for a sensor temperature model for robust diagnostics and assurance of component protection can be realized by two different models. Today's lambda sensors typically have heaters that are very powerful and therefore low-resistance. However, due to the manufacturing process, which may include screen printing and / or sintering, significant variations in heater resistance typically occur. By separating the requirements for two different temperature models, if overheating of the sensor element is imminent, the closed-loop control of the heater can intervene to give the relatively weak, high-resistance heater enough time to heat the sensor element sufficiently for the load-open diagnostics. Furthermore, improved diagnostic robustness can also be achieved by the temperature model adjusting the closed-loop control of the heater by enabling the diagnostics.

[0040] In an error-free system, the load-release diagnostic is typically enabled when a predetermined temperature threshold is exceeded. In an error-containing system, a temperature signal is typically unavailable, so the diagnostic is typically enabled based on a sensor temperature model. In current prior art, the load-release diagnostic can be enabled based on a WPA / BP model, but robust diagnostics and overheat protection must be provided at the same time. In this case, the debouncing time must be long enough to ensure a reliable diagnostic result, but must be as short as possible for overheat protection reasons.

[0041] The proposed method allows for an extension of the allowable debouncing time by simultaneously enabling the open load diagnostic and reducing the heater voltage. The debouncing time can be extended depending on the selection of the effective heater voltage to be reduced.

[0042] Furthermore, the proposed method allows for the decomposition of the robust diagnostic and overheat protection requirements into two heater models. Separate modeling of the WPA model for enabling open-load diagnostics and the BP model for overheat protection provides additional degrees of freedom, allowing for a wider variation in heater resistance to be considered. This is especially important when the WPA heater has not yet reached a high enough temperature to perform robust diagnostics, while the BP heater is already in imminent danger of overheating.

[0043] Both of the two variations allow increasing the effective energy input for heating the sensor without risking sensor damage.

[0044] Further optional details and features of the invention will become apparent from the following description of preferred embodiments which are illustrated diagrammatically in the drawings. [Brief explanation of the drawings]

[0045] [Figure 1] 1 shows an overall overview of a system including a control device, a lambda sensor, a cable connector and a sensor connector, in which the method according to the invention can be implemented; [Figure 2] FIG. 1 illustrates a basic software system. [Figure 3A] 4 is a further flow chart illustrating a method according to the present invention. [Figure 3B] 4 is a further flow chart illustrating a method according to the present invention. [Figure 4A] FIG. 10 is a graph showing the temperature characteristics of the ceramic of the lambda sensor. [Figure 4B] FIG. 10 is a graph showing the temperature characteristics of the ceramic of the lambda sensor. [Figure 4C] FIG. 10 is a graph showing the temperature characteristics of the ceramic of the lambda sensor. [Figure 5] FIG. 10 shows the temperature characteristic and sensor voltage signal for the ceramic of the lambda sensor. DETAILED DESCRIPTION OF THE INVENTION

[0046] Embodiments of the invention FIG. 1 shows a general overview of a system 108 including a lambda sensor 110, in particular a wideband lambda sensor 112, a control device 114, and a cable and sensor connector 118, in which the method according to the invention can be implemented.

[0047] The lambda sensor 110 can be connected to the control device 114 via a cable connector and sensor connector 118 and a cable harness 120. The lambda sensor 110 can be screwed into an exhaust pipe 122. The control device 114 can have a heater output stage 124 for heating the sensor, an ASIC 126, in particular ASIC CJ 135, and a microcontroller 128. The microcontroller 128 can include a hardware capsule 130 and a software component driver 131 for the lambda sensor 110. The ASIC 126 can be a hardware component that, in particular, drives and converts the sensor signal that is supplied to the microcontroller 128 for the software component driver 131.

[0048] 2 illustrates a software scheme 132. The load disconnection diagnostic unit 134 may include an error identification unit, a suspected error notification unit, and a signal detection unit. Notification may occur in a diagnostic manager 142. The load disconnection diagnostic unit 134 may be implemented using a physical temperature model 136 of the I.O. system. Additionally, the load disconnection diagnostic unit 134 may be implemented using a physical temperature model 138 of the WPA system. The physical temperature model 136 and the physical temperature model 138 may each incorporate one parameter: battery voltage, stop time, ambient temperature, and heater, as shown schematically by arrow 140. Additionally, the load disconnection diagnostic unit 134 may be implemented based on sensor signals and an exhaust gas temperature model that may take into account wall temperature and / or catalyst temperature, as shown schematically by arrow 142.

[0049] 3A shows a flowchart of a method according to the present invention. For the heater drive control shown in field 144, the operating temperature of the wideband lambda sensor can be calculated using at least one temperature model of the wideband lambda sensor, in particular the WPA / BP model, as shown in field 146. If the operating temperature calculated by the temperature model exceeds another predetermined limit, a method for identifying a load-release error can be enabled as shown in field 148. When the execution of the method for identifying a load-release error is enabled, the heating voltage of the heater of the wideband lambda sensor can be simultaneously reduced, in particular if overheating protection is required, as shown in field 150. After a debouncing time, as shown by arrow 152, the error confirmation of the load-release diagnostics can be queried as shown in field 154. If an error is confirmed as shown by arrow 156, a load-release error exists as shown by field 158. If no error is confirmed as shown by arrow 160, the enablement of the heater diagnostics is reported as shown in field 162.

[0050] Thus, the heater voltage is reduced simultaneously with enabling the open load diagnostic, thereby increasing the allowable debouncing time. Depending on the effective heater voltage that is reduced, the debouncing time can be extended.

[0051] Figure 3B shows another flowchart of a method according to the invention, which corresponds at least in part to the flowchart shown in Figure 3A, and reference is therefore also made to the above description of Figure 3A.

[0052] 3B, a temperature model may be used to calculate the operating temperature of the wideband lambda sensor as shown generally in field 146, where if the operating temperature calculated by the temperature model exceeds a predetermined limit, a method for identifying an open load error may be enabled as shown in field 148. The temperature model may be a WPA model.

[0053] Another temperature model, specifically the BP model, can be used to check whether overheat protection is needed, as shown schematically in field 164, and to further reduce the heater voltage, as shown schematically by field 150. This provides an additional degree of freedom, as shown by arrow 166.

[0054] Thus, the requirements for robust diagnostics and overheat protection can be split between two heater models. By separately modeling the WPA model for enabling open-load diagnostics and the BP model for overheat protection, additional degrees of freedom are gained, allowing for wider variations in heater resistance to be considered. This is especially important when the WPA heater has not yet reached a high enough temperature to perform robust diagnostics, while the BP heater is already in imminent danger of overheating.

[0055] The two variants according to FIGS. 3A and 3B make it possible to increase the effective energy input for heating the sensor without risking damage to the sensor.

[0056] Figures 4A to 4C show temperature characteristics for the lambda sensor ceramic: Figure 4A shows the temperature characteristics of the lambda sensor ceramic in an iO system, Figure 4B shows the temperature characteristics of the lambda sensor ceramic in a system with a heater error, and Figure 4C shows the temperature characteristics of the lambda sensor ceramic in a system with a cable break.

[0057] The temperature characteristics of the lambda sensor ceramic and the sensor voltage signal are shown in Figure 5. The temperature characteristics correspond to those shown in Figures 4A to 4C. The temperature characteristics of the lambda sensor ceramic in the i.O. system are shown by circles, the temperature characteristics of the lambda sensor ceramic in the system with a heater error are shown by triangles, and the temperature characteristics of the lambda sensor ceramic in the system with a cable break are shown by crosses.

[0058] The sensor voltage signal of the lambda sensor ceramic in the i.O. system is shown by a circle, the sensor voltage signal of the lambda sensor ceramic in the system with a heater error is shown by a triangle, and the sensor voltage signal of the lambda sensor ceramic in the system with a cable break is shown by a cross.

[0059] The enable time for the open load diagnostic is shown by line 200, and the end time for the open load diagnostic is shown by line 202. This provides a maximum wait time when a suspected error occurs, as shown by arrow 204. Additionally, arrow 206 indicates the minimum wait time for enabling the open load diagnostic. In region 206, the change in the sensor voltage can be seen.

Claims

1. 1. A method for identifying a load release error in a wideband lambda sensor (112) configured to detect at least one characteristic of exhaust gases in an exhaust gas chamber of a motor vehicle, the wideband lambda sensor (112) further comprising at least one heater, the method comprising: The method comprises the following steps: a) enabling an error check to check whether the wideband lambda sensor (112) is sufficiently heated using a temperature model; b) performing error checking; Including, If no errors are identified after error checking, the next step is to b1) i.o. terminating the method with a result (normal result). is executed, If an error is identified after error checking, the next step is to b2) terminating the method with an n.i.o. result (abnormal result). is executed, a check for the need for overheating prevention is performed before performing step b), and if the need for overheating prevention exists, a heater voltage of the heater is reduced simultaneously with or before performing step a); In step a), it is checked whether the operating temperature of the wideband lambda sensor (112) calculated by the temperature model exceeds a predetermined limit value; the temperature model is a WPA model, and the need for overheat protection is checked using another temperature model; the other temperature model is a BP model, The method, wherein the error check in step b) involves comparing the measured internal resistance with a diagnostic threshold value.

2. at least one broadband lambda sensor (112); At least one control unit; A system comprising: the control unit includes at least one processor; The system, wherein the control unit is configured to perform the method steps of the method of claim 1 .

3. A computer program comprising a program code which, when executed on a computer, causes said computer to carry out the method of claim 1.

4. A data carrier storing a program code, 10. A data carrier, the program code being for causing a computer to carry out the method according to claim 1 after being loaded into the working memory and / or main memory of the computer.

Images