Method and arrangement for performing an exhaust gas analysis on motor vehicles having an on-board engine control and diagnostic system

#Due to legal regulations, motor vehicles must be subjected to emissions inspections at regular intervals. The emissions test is performed according to a fixed procedure using an exhaust emissions tester, whereby the motor vehicle has to be brought into predetermined operating states for the various individual analysis steps, and be kept in these states for the duration of the respective analysis steps. The predetermined operating states are set by the test personnel in accordance with instructions provided by an analysis procedure, which is typically displayed on a monitor. For example, a predetermined engine speed is set by pressing the accelerator pedal, or the required disturbance variable for the lambda control is applied or removed by pulling off or plugging in an air hose. Predetermined data, including the exhaust gas values, of the motor vehicle being tested are stored and printed out in the form of a test certificate.

#Due to legal requirements, enacted, in particular, to reduce the emissions of motor vehicles, the USA since 1996 and the European Union beginning in 2000 have required new cars to be equipped with on-board diagnostic (OBD) systems. These OBD systems, either as a component of the on-board engine control or in combination therewith, detect essential operating variables of the motor vehicle as well as its emissions values using suitable sensors, and detect malfunctions of the motor vehicle by comparing these variables with predetermined recommended variables. In addition to displaying the malfunctions on-board the motor vehicle, the information needed for identifying and repairing these malfunctions must be made available via a diagnostic interface.

#Equipping motor vehicles with on-board diagnostic systems will affect the emissions test at least in that current and/or stored emissions-related motor vehicle data will be read out from the diagnostic systems during the emissions test and recorded together with additional emissions test data in the course of the emissions test. This means that the exhaust gas tester must be connected to the diagnostic interface of the on-board diagnostic system.

#In the following, reference is made to the preferred embodiments shown in the drawing, for further explaining the present invention, its features and its advantages.

#FIG. 1 shows a first exemplary embodiment of the arrangement according to the present invention, and

#FIG. 2 shows a further exemplary embodiment.

#FIG. 1 shows a motor vehicle 1, which has an on-board engine control and diagnostic system 2 having a diagnostic interface 3, in the form of a simplified block diagram. The engine control and diagnostic system 2 contains one or more engine control functions 4 and a diagnostic unit 5, which exchange data with one another and are connected to the diagnostic interface 3. A plurality of sensors 6 provide data 7 specific to the current operating state to the engine control and diagnostic system 2, which in turn transmits control signals 8 to actuators 9, to control the engine and other systems of the motor vehicle 1. The diagnostic unit 5 evaluates significant operating variables of the motor vehicle 1, of which some operating variables allow conclusions about the emissions behavior to be drawn. The diagnostic unit 5 also indicates a malfunction of the motor vehicle 1 whenever limiting values are exceeded, by means of a lamp 10 in the motor vehicle 1. In addition, the diagnostic unit 5 provides information, such as error codes, via the diagnostic interface 3, upon request, for identifying and repairing the malfunction of the motor vehicle 1.

#During the emissions test, the exhaust gases of the motor vehicle 1 are supplied via a sampling line 11 to an exhaust gas tester 12 and analyzed therein. The emissions test is performed within a test and control unit 17 as a function of data from the motor vehicle 1 that are read out from the engine control and diagnostic system 2 via the diagnostic interface 3. Alternatively or in addition, the data may be registered using a suitable sensor 13 in the motor vehicle 1, as here, for example, the engine speed. The emissions test procedure is controlled by a program, which is executed in a computer device 14 and which contains information about the analysis steps through which the emissions test passes as well as manufacturer-specific information about the engine control of the motor vehicle 1. Specific control commands 15 are generated as a function of the respective analysis steps through which the program passes. These control commands are then transmitted from the test and control unit 17 via the diagnostic interface 3 to the engine control and diagnostic system 2, for the purpose of setting predetermined operating states of the motor vehicle 1. Data provided by the engine control and diagnostic system 2 and/or received from the sensor 13 signals that the various respective operating states have been reached, whereupon, respectively, the corresponding test steps of the emissions analysis are performed. The exhaust gas values obtained hereby are output in a test report 16 together with other data received from the motor vehicle 1.

#In a second embodiment of an arrangement according to the present invention, shown in FIG. 2, the control commands 15 for setting predetermined operating states of the motor vehicle 1 are generated in a controller 18, for example a diagnostic device, which also controls the exhaust gas tester 12. For this purpose, the controller 18 contains, in addition to a diagnostic and control unit 19 connected to the diagnostic interface 3 of the motor vehicle 1, a computer unit 14, in which a program that controls the execution of the emissions test is run. When a given operating state of the motor vehicle 1 prescribed for a specific test step is reached in response to a control command 15, the exhaust gas tester 12 is activated to perform the exhaust gas analysis for that particular test step.