Abstract:
A method makes it possible to measure and evaluate the efficiency of a start-stop system of a vehicle having an internal combustion engine, and on the basis of the measurement, to optimize the efficiency in a vehicle-specific fashion or with regard to the driving behavior of the driver.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2009 010 925.0, filed Feb. 27, 2009; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a start-stop system of a motor vehicle with an internal combustion engine. Such start-stop systems are described, for example, in U.S. Patent Publication No. US 2006/0208568 A1 (cf. DE 10 2006 000 114 A1, JP2006256562) and U.S. Pat. No. 6,371,889 B1 (cf. DE 100 40 094 A1, JP2001055940). 
         [0003]    There, whenever the vehicle is at a standstill, that is to say the speed of the vehicle is equal to zero, the system checks on the basis of various deactivation conditions as to whether it is possible to shut down the internal combustion engine while at a standstill. If one or more deactivation conditions are met, the internal combustion engine is shut down and is only re-activated when the controller detects the presence of at least one activation condition. 
       SUMMARY OF THE INVENTION 
       [0004]    It is accordingly an object of the invention to provide a start-stop system which overcomes various disadvantages associated with the heretofore-known devices and methods of this general type and which provides for a start-stop system that is specifically improved as it further extends the advantages of the start-stop system with regard to fuel consumption and emissions. 
         [0005]    With the foregoing and other objects in view there is provided, in accordance with the invention, a method of operating an internal combustion engine of a motor vehicle, the method which comprises: 
         [0006]    automatically starting the internal combustion engine in dependence on at least one activation condition and/or automatically deactivating the internal combustion engine in dependence on at least one deactivation condition; 
         [0007]    measuring the at least one activation condition and/or the at least one deactivation condition while the motor vehicle is at a standstill; and 
         [0008]    storing a presence of the activation conditions and/or deactivation conditions in a memory and evaluating the presence of the activation conditions and/or deactivation conditions in order to diagnose a control of the internal combustion engine. 
         [0009]    In other words, the objects are achieved according to the invention, with a method for operating an internal combustion engine of a motor vehicle, in which method the internal combustion engine is automatically started as a function of at least one activation condition and/or automatically deactivated as a function of at least one deactivation condition, with the at least one activation condition and/or the at least one deactivation condition being measured while the vehicle is at a standstill, in that the presence of the activation conditions and/or deactivation conditions are stored and evaluated in order to diagnose the control of the internal combustion engine. 
         [0010]    By means of the storage, according to the invention, of the deactivation and activation conditions and associated parameters and/or time indications, it is possible to measure the efficiency of the start-stop system at the end of a driving cycle and/or over the entire operating duration of the vehicle. 
         [0011]    It is thus possible, for example, for a characteristic regarding the use of the start-stop system to be displayed to the driver at the end of a driving cycle, and for recommendations to be shown as to how he can improve the efficiency of the system. 
         [0012]    It is also possible, in the event of an inspection of the motor vehicle, and during the course of an on-board diagnosis, for the characteristics determined using the method according to the invention to be read out and evaluated by trained professionals. This may on the one hand lead to the identification and realization of improvement potential in technical components of the motor vehicle. Furthermore, it is also possible for the trained workshop personnel to give the driver of the motor vehicle indications as to how he can use the start-stop system more efficiently and thereby reduce fuel consumption and save on operating costs. Finally, the vehicle manufacturer gains information regarding how often the start-stop system has been used, and if appropriate, regarding why said start-stop system could not be used despite the vehicle being at a standstill. 
         [0013]    In a further advantageous embodiment of the invention, it is provided that a first time counter starts running when the vehicle comes to a standstill, and in that the first time counter is stopped when the vehicle starts moving again. In this way, it is possible to measure the standstill times of the vehicle, which are an important dependent variable for the assessment of the efficiency of the start-stop system. 
         [0014]    In a further advantageous embodiment of the invention, it is provided that a first group of conditions for the stop of the internal combustion engine is queried and that a first counter is incremented by a value if all the conditions of the first group are met. 
         [0015]    In a further advantageous embodiment of the invention, a second group of conditions for the deactivation of the internal combustion engine is queried and a second counter is incremented by a value if all the conditions of the second group of conditions are met. The deactivation of the internal combustion engine is thereupon initiated. 
         [0016]    From the ratio of the values between the first counter, which measures the presence of the first group of conditions, and the value of the second counter, which measures the presence of the additional conditions of the second group of conditions, it is already possible to draw a first conclusion regarding the efficiency of the start-stop system. 
         [0017]    In a further advantageous embodiment of the invention, it is provided that a second time counter starts running when the internal combustion engine is deactivated, and that the second time counter is stopped when the internal combustion engine is re-activated. 
         [0018]    From the ratio of the first time counter, which measures the duration for which the vehicle is at a standstill, and of the second time counter, which measures the duration for which the internal combustion engine is deactivated, it is possible to draw a further, very significant conclusion regarding the efficiency of the start-stop system. 
         [0019]    In a further advantageous embodiment of the invention, the deactivation of the internal combustion engine is prohibited if the value of the first time counter is higher than a predefined limit value. In this way, it is ensured that erroneous deactivations of the internal combustion engine cannot occur. 
         [0020]    Furthermore, it is provided according to the invention that the cause for the prohibition of the stop of the internal combustion engine is stored together with a time indication. 
         [0021]    To re-activate the internal combustion engine after a deactivation has taken place, the internal combustion engine is automatically activated if at least one activation condition is present, and the cause for the presence of the at least one activation condition is stored together with a time indication. 
         [0022]    By forming ratios between the first time counter and the second time counter and between the value of the first time counter and the value of the second counter, it is possible to draw important conclusions regarding the efficiency of the start-stop system. Said ratios also give an indication regarding the causes for a low efficiency of the start-stop system, and may also be used to improve efficiency. 
         [0023]    It has proven to be particularly advantageous for the method to be carried out at the end of each driving cycle, that is to say when the vehicle is parked and the ignition key is removed. It is then possible, directly after the internal combustion engine is shut down, for an evaluation to be carried out and for an indication of a possible improvement potential to be given to the driver before he has left the vehicle. 
         [0024]    In addition, it is also possible for the method according to the invention to be carried out over the entire operating duration of the vehicle, such that a declaration can be made, over the entire distance driven by the vehicle, regarding the efficiency of the start-stop system. 
         [0025]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0026]    Although the invention is illustrated and described herein as embodied in a method and computer program for operating an internal combustion engine, and control unit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0027]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0028]      FIG. 1  is a first portion of a flow diagram illustrating an embodiment of the method according to the invention; 
           [0029]      FIG. 2  is a second portion of a flow diagram illustrating the method according to the invention; and 
           [0030]      FIG. 3  is a schematic illustration of an internal combustion engine. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Referring now to the figures of the drawing in detail, we will first explain a functional principle of an internal combustion engine of a motor vehicle with a start-stop system on the basis of  FIG. 3 , to which reference is hereby made, and which will be explained further below. 
         [0032]    An exemplary embodiment of the method according to the invention will be presented and explained with reference to  FIGS. 1 and 2 . 
         [0033]    After the start of the method, a first functional block  41  checks whether the vehicle is in motion or at a standstill. If it is detected that the vehicle is at a standstill, a first time counter  43  starts running. The first time counter  43  therefore measures the duration for which the vehicle is at a standstill, during one driving cycle and over the entire operating duration of the internal combustion engine. 
         [0034]    If it is detected in the first functional block  41  that the vehicle is at a standstill, then a second functional block  45  checks whether a first group of conditions for the deactivation of the internal combustion engine  40  are met. 
         [0035]    Said conditions are base conditions which must imperatively be met in order to be able to deactivate the internal combustion engine  40 . Examples of such base conditions are: 
         [0036]    Driver brings the vehicle to a standstill by means of a braking process 
         [0037]    Vehicle has been moving at speed for a defined time 
         [0038]    Vehicle has moved a minimum distance 
         [0039]    Enablement by means of selector lever pending 
         [0040]    If the base conditions are not met, the program branches back to before the first functional block  41 . 
         [0041]    If the first group of conditions for the deactivation of the internal combustion engine are met, a first counter  47  is incremented by a value of 1. Furthermore, a third functional block  49  checks whether a second group of conditions for the deactivation of the internal combustion engine  40  are met. If the additional conditions for the deactivation of the internal combustion engine  40  are met, then the internal combustion engine  40  is deactivated and a second counter  51  is activated which measures the number of deactivations (D). In a second time counter  53 , the duration of the deactivation of the internal combustion engine  40  is measured. 
         [0042]    If the second group of conditions for the engine stop are not met, the cause, that is to say the condition which has not been met, is stored together with a time indication in a third memory  55 . 
         [0043]    Furthermore, the program then branches back to before the first functional block  41 . 
         [0044]    If the second group of conditions for the deactivation of the internal combustion engine are met, then the internal combustion engine is deactivated in a fourth functional block  57  (cf  FIG. 2 ). 
         [0045]    Enablement of stop operation by external control units 
         [0046]    Enablement of stop operation by diagnosis conditions, engine control unit 
         [0047]    Enablement of stop operation if relevant sensors and actuators are without faults 
         [0048]    Enablement of stop operation if relevant CAN communication is without faults. 
         [0049]    A fifth functional block  59  checks whether at least one activation condition for the internal combustion engine is present. If this is the case, the internal combustion engine  40  is re-activated in the fifth functional block  59 . In a second memory  61 , the cause for the activation of the internal combustion engine is stored together with a time indication. At the same time, the second time counter  53 , which measures the duration for which the internal combustion engine is deactivated, is stopped. 
         [0050]    A sixth functional block  63  detects whether the vehicle still remains at a standstill or has in the meantime started moving. Once the vehicle is moving, the first time counter  43  is stopped. Finally, in a sixth functional block  65 , the ratio between the values of the second counter  51  and the first counter  47  is formed for example at the end of each driving cycle for the directly preceding driving cycle or for the entire operating duration of the internal combustion engine. 
         [0051]    Furthermore, it is possible to form a ratio from the values of the first time counter  43  (standstill time) and the second time counter  53  (deactivation time). From said ratios, it is possible to obtain the characteristic variables for evaluating the efficiency of the start-stop system. Said characteristic variables may on the one hand be taken into consideration for fault diagnosis of hardware components of the motor vehicle. This is advantageous in particular if the memories  55  and  61  are read out and the causes for the stop prevention or for the renewed deactivation of the internal combustion engine are taken into consideration in the evaluation. 
         [0052]    Furthermore, from the efficiency of the start-stop system, it is also possible to provide the driver of the vehicle with recommendations on possible actions he can take to increase the efficiency and thereby reduce the fuel consumption of the vehicle. 
         [0053]      FIG. 3  shows the technical field of the invention. In detail,  FIG. 3  shows the internal combustion engine  40  having the combustion chamber  42  which is sealed off in a movable fashion by a piston  44 . A charge exchange of the combustion chamber  42  is controlled by at least one inlet valve  46  and one outlet valve  48  which, for this purpose, are actuated by corresponding actuators  50 ,  52 . In the embodiment of  FIG. 3 , an injector  54  serves to meter fuel into an air charge of the combustion chamber  42 . The resulting mixture of fuel and air is ignited by a spark plug  56 . The charging of the combustion chamber  42  with air takes place from an intake pipe  58  which has a throttle flap  62 , which is actuated by a throttle flap actuator  64 , and an air mass sensor  66 . 
         [0054]    The internal combustion engine  40  is controlled by the control and regulating (i.e., closed-loop control) unit  72  which, for this purpose, processes signals depicting different operating parameters of the internal combustion engine  40 . In the illustration of  FIG. 3 , such operating parameters are in particular signals mL from the air mass sensor  66 , the signal FW from a driver demand transducer  74  which measures a torque demand by the driver, and the signal n from a rotational speed transducer  76  which measures a rotational speed n of a crankshaft of the internal combustion engine  40 . 
         [0055]    It is self-evident that modern internal combustion engines  40  are fitted with a multiplicity of further transducers and/or sensors, which are not illustrated here for clarity. Examples of such sensors are temperature sensors, pressure sensors, exhaust-gas sensors, et cetera. The listing of the transducers  66 ,  74  and  76  is therefore not intended to be exhaustive. It is also not necessary for a separate sensor to be provided for each of the operating parameters processed by the control and regulating device  72 , because the control and regulating device  72  can model various operating parameters by means of mathematical models from other measured operating parameters. 
         [0056]    From the received transducer signals, the control and regulating device  72  forms inter alia actuating variables for setting the torque to be generated by the internal combustion engine  40 . In the embodiment of  FIG. 3 , such actuating variables are in particular an actuating variable S_K for activating the injector  54 , an actuating variable S_Z for activating the spark plug  56 , and an actuating variable S_L_DK for activating the throttle flap actuator. 
         [0057]    The control and regulating device  72  is otherwise set up, in particular programmed, to carry out the method according to the invention or one of its embodiments, and/or to control the corresponding method processing.