Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/416—Systems
  • G01N27/417—Systems using cells, i.e. more than one cell and probes with solid electrolytes
  • G01N27/4175—Calibrating or checking the analyser

Definitions

• the invention relates to a method and a device for diagnosing the electrical contacting of an exhaust gas sensor with two cells, in which a first of the cells is connected between a first and a second terminal of the exhaust gas sensor and a second of the cells between the second and a third terminal.
• the first cell represents a so-called pump cell of the lambda probe.
• the second cell is the reference cell of the lambda probe.
• Reference cell is usually interconnected as virtual ground.
• DE 102008 001 697 A1 discloses a device for diagnosing the electrical contacting of an exhaust gas sensor with two cells, in which a first of the cells is connected between a first and a second connection of the exhaust gas sensor and a second one of the cells is interconnected between the second and a third connection. It comprises a first current source, which is connected via a first controllable switching element to the first terminal and coupled to the second terminal, through which a current between the first and the second terminal can be driven, and a second current source, via a third controllable Switching element is connected to the third terminal and coupled to the second terminal, through which a current between the second and the third terminal is driven. It further comprises a first voltage measuring device, which is connected between the first and the second terminal, a second voltage measuring device, which is connected between the second and the third terminal, and a controller, by which a first voltage of the first
• Triggering of the first and third switching element and the first and the second current source can be determined, which can be concluded from the determined first and / or the second voltage to a defect of the electrical contact.
• the invention provides a device for diagnosing the electrical contacting of an exhaust gas sensor with two cells, in which a first of the cells is connected between a first and a second terminal of the exhaust gas sensor and a second of the cells between the second and a third terminal.
• the device comprises: a first current source connected to the first terminal via a first controllable switching element and coupled to the second terminal through which a current is drivable between the first and second terminals; a second current source connected to the third terminal via a third controllable switching element and coupled to the second terminal through which a current is drivable between the second and third terminals; a first voltage measuring device connected between the first and second terminals; a second
• Voltage measuring device which is connected between the second and the third terminal; a controller, by which a first voltage of the first voltage measuring device and / or a second voltage of the second voltage measuring device in dependence on the control of the first and the third
• Switching element and the first and the second current source can be determined, which can be concluded from the determined first and / or the second voltage to a defect of the electrical contact.
• the invention further provides a method for diagnosing the electrical contacting of an exhaust gas sensor with two cells, in which a first of the cells is connected between a first and a second terminal of the exhaust gas sensor and a second of the cells between the second and a third terminal, by means of a device which comprises: a first one
• a power source which is connected via a first controllable switching element to the first terminal and coupled to the second terminal, through which a current between the first and the second terminal is drivable; a second power source over a third controllable switching element is connected to the third terminal and coupled to the second terminal, through which a current between the second and the third terminal is drivable; a first voltage measuring device connected between the first and second terminals; and a second voltage measuring device connected between the second and third terminals.
• Detected switching element and the first and the second current source which is concluded based on the determined first and / or the second voltage to a defect of the electrical contact.
• a wiring harness comprises the cable provided between the exhaust gas sensor and the device. If required, the diagnostic concept allows the line diagnosis with only a brief interruption of the service
• Exhaust gas sensor during operation The device can be realized with only a few components. As a result, this can be realized in a simple and cost-effective manner.
• the first and / or the second current source is a DC source or an AC source.
• the first and the second current source in particular to different rated currents, regulated. This allows a simultaneous diagnosis of the electrical contacting of various terminals and leads of the contact.
• the second connection of the exhaust gas sensor is connected as a virtual ground.
• the device has an interconnection which is known in principle from the prior art and which holds the second connection at a defined potential, for example 2.5 V.
• the first and / or the second voltage measuring device comprise a
• Lock-in amplifier for detecting a DC voltage when the power sources are designed as AC sources.
• the exhaust gas sensor comprises a balancing resistor, which is connected between the first terminal and a fourth terminal, the device comprising: a second controllable
• Switching element connected between the second terminal and a node between the first and second current sources; a third current source connected to the fourth terminal via a fourth controllable switching element and coupled to a node between the first switching element and the first current source, through which a current is drivable between the first and fourth terminals; a third voltage measuring device connected between the first and fourth terminals; wherein the controller is adapted to a third voltage of the third
• Voltage measuring device as a function of the control of the switching elements and the current sources to determine, with reference to the determined third voltage to a defect of
• the adjustment resistor serves to
• An advantage of the device according to the invention for the diagnosis of the electrical contact is that the device can be constructed discretely.
• this may also be integrated in a microcontroller that interacts with a controller of the exhaust gas sensor, or directly in a controller (control ASIC) of the exhaust gas sensor.
• the determination of the first and / or the second voltage during operation of the exhaust gas sensor and / or during the start of the internal combustion engine to monitor the
• Exhaust gas sensor is provided.
• the determination of the voltages is independent of the operation of a
• Internal combustion engine performed which includes the exhaust gas sensor and monitored by the internal combustion engine emitted exhaust gases.
• the first voltage is determined, wherein at a voltage value of the first voltage, which is well above the nominal resistance of the first cell, to a
• the second voltage is determined, wherein at a voltage value of the second voltage, which is far above the nominal resistance of the second cell, to one
• Contacting error is closed at the second terminal; c) with open first switching element and closed second and third switching element and activated second current source, the second voltage is determined, wherein at a voltage value of the second voltage, which is well above the nominal resistance of the second cell, to a
• a closed switching element is understood to mean a conductive switching element and an open switching element is a non-conductive switching element.
• the described procedure which alternatively can also be carried out in the order c), b) and a), not only makes it possible to detect a fault in the electrical contacting, but also to which of the terminals the fault in the contacting is present.
• third voltage source is the third voltage is determined, wherein at a voltage value of the third voltage, well above the nominal resistance of the
• Adjustment resistor is closed, a contact failure on the first or fourth connection is closed.
• Fig. 1 is a schematic representation of an inventive
• Fig. 2a shows the arrangement of Fig. 1 during a first
• Measuring step, 2b shows the currents and voltages occurring within the arrangement in a diagram over time
• Fig. 3a shows the arrangement of Fig. 1 during a second
• Fig. 4a shows the arrangement of Fig. 1 during a third
• 4b shows the currents and voltages occurring within the arrangement in a diagram over time.
• Fig. 1 shows a schematic representation of a
• Inventive device CA for diagnosing the electrical contacting of an exhaust gas sensor LS in the form of a linear exhaust gas probe.
• the exhaust gas sensor LS comprises as a first cell a pump cell PZ and as a second cell a reference cell RZ.
• the pump cell PZ is connected between a first terminal 1 and a second terminal 2 of the exhaust gas sensor.
• the reference cell RZ is connected between the second terminal 2 and a third terminal 3 of the exhaust gas sensor LS.
• FIG. 1 shows in dashed lines an optional balancing resistor R3, which is provided between the first terminal 1 and a fourth terminal 4.
• the trimming resistor R3 serves to compensate for manufacturing tolerances of the probe, i. of
• the device CA which comprises all the components for diagnosing the electrical contact, is preferably part of a control ASIC (Application Specific Integrated Circuit) of the exhaust gas sensor.
• ASIC Application Specific Integrated Circuit
• the components described below can be arranged in a separate microcontroller which is then communicative with the principle
• the second terminal 2 is connected in a known manner as a virtual ground.
• the circuitry necessary for this, which connects the second connection to e.g. 2.5 V is known to those skilled in the art, so that this is not shown in the schematic representation.
• the necessary circuitry is usually provided in the control ASIC.
• the device CA includes a number of ports corresponding to the number of ports of the exhaust gas sensor LS.
• Corresponding or mutually associated connections of the exhaust gas sensor LS and the device CA are interconnected via lines LI, L2, L3, L4, which are usually present as a wiring harness.
• the device CA monitors whether a line break of one of the lines LI to L4 is present or an open connection is present within the exhaust gas sensor LS (so-called open-line diagnosis).
• the device CA comprises a first current source II, which via a first controllable switching element Sl to the first terminal
• a second current source 12 is connected via a third controllable switching element connected to the third port.
• the other end of the second current source 12 is connected to the second terminal 2 via the second switching element S2.
• the second switching element S2 is required only when the optional trim resistor R3 is provided in the exhaust gas sensor LS. This is assumed in the following description.
• a first voltage measuring device for detecting a voltage Ul is connected between the first and the second connection 1, 2. In a similar way is a second
• Voltage measuring device for detecting a voltage 2 between the second and the third terminal 2, 3 interconnected. The necessary for the detection of the first and second voltage
• a third current source 13 is provided which is coupled to the first terminal 1 via the first switch S1 and to the fourth terminal 4 via a fourth switching element S4.
• a third voltage measuring device for detecting a voltage 3 is provided between the terminals 1 and 4.
• the device CA further comprises a controller, which is designed to control the controllable switching elements Sl to S4 and the current sources II to 13, and those of the
• Voltage measuring devices determined voltage values Ul to U3 evaluate. The control is not shown for simplicity in Fig. 1 and the further drawings.
• the first to third current sources II to 13 can optionally be designed as a DC source or as an AC source. If the current sources II, 12, 13 are designed as alternating current sources, they can be regulated in particular to different rated currents (with the same or different signs). As a result, a simultaneous determination of the voltages Ul to U3 is possible.
• FIGS. 2 a, 3 a and 4 a respectively show the states of the switching elements S 1 to S 4 required for a measuring sequence and the voltages U 1 or U 2 to be detected in each case.
• FIGS. 2 b, 3 b and 4 b represent the current impressed into the exhaust-gas sensor for the respective measuring section and the measured voltage in the event of a fault (NOK) and in the proper case (OK).
• the switching elements S1 and S2 are closed.
• the switching element S3 is open.
• the first current source II is activated and the voltage Ul is determined by the first voltage measuring device.
• a current is generated by the pump cell PZ.
• the internal resistance of the pump cell PZ is usually in the range of 300 ⁇ . If the lines LI, L2 and all the lines PZ relevant pump cell in order, then a voltage Ul is set, which results from the current generated by the current source II and the internal resistance of the pump cell PZ. Since both variables are known, a plausible voltage value can be determined. As is apparent from Fig. 2b, an approximately rectangular current is impressed in the pumping cell. Owing to
• Exhaust gas sensor LS results in an approximately sawtooth-shaped, temporally shifted voltage Ul, which has a rather flat course in the "good case" OK If, however, one of the lines LI or L2 has an interruption, the voltage generated by the current source II increases due to the This results in a much greater voltage U1 (NOK in Fig. 2b)
• the switching elements Sl and S2 remain closed, as well as the switching element S3 is still open Likewise, power source II is activated, however, finds a Measurement of the voltage U2 by the second
• the voltage value U2 should be small in the event of a fault, since no current can flow via the terminal 3 and the circuit is closed via the terminal 2, i. below a diagnostic threshold. If, on the other hand, the line L2 is defective, a significantly greater voltage U2 is determined on the basis of the current which is greater by the first current source II. If this is the case, it can be concluded that there is a line break in line L2.
• the switching elements S2 and S3 are closed, while the switching element Sl is open.
• the second current source 12 is activated.
• the same procedure is used to check one of the lines LI, L4, in which case the switches S1 and S4 are closed and the switching elements S2 and S3 are open.
• the third current source 13 is activated and the voltage U3 is determined. If a line break is detected based on the voltage U3, however, it can not be determined whether it is assigned to the line LI or L4. Nevertheless, the defect of the electrical contact can also be signaled here.
• An advantage of the procedure described is that multiple errors, ie simultaneous interruptions on more than one line, are also detected in the described cycle and do not lead to failure of the diagnosis. If the current sources II to 13 are formed as alternating current sources, then the device can be implemented such that a frequency demodulation is automatically performed and that caused by the alternating current
• the voltage measuring devices comprise lock-in amplifiers known to the person skilled in the art.
• the circuit complexity can be reduced.
• the described circuit of the device according to the invention as well as the implementation of the described measuring sequence can advantageously be carried out already during the engine start as well as continuously during operation of the exhaust gas sensor. For this purpose, only a brief interruption of the exhaust gas measurement is required.

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• 2011
  • 2011-02-14 DE DE201110004073 patent/DE102011004073A1/de not_active Ceased
• 2012
  • 2012-02-09 WO PCT/EP2012/052166 patent/WO2012110385A1/de active Application Filing

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