Patent Publication Number: US-10767586-B2

Title: Pilot control of an internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of PCT Application PCT/EP2015/077750 filed Nov. 26, 2015, which claims priority to German Application DE 10 2015 200 898.3, filed Jan. 21, 2015. The contents of the above applications are incorporated herein by reference. 
     FIELD OF INVENTION 
     The invention relates to the mixture preparation of an internal combustion engine. In particular, the invention relates to the mixture preparation in pilot control mode. 
     BACKGROUND 
     An internal combustion engine, in particular a reciprocating-piston internal combustion engine, for example on board a motor vehicle, is operated by means of a mixture preparation, wherein the mixture preparation determines a quantity or mass of fuel which is to be injected into the internal combustion engine on the basis of parameters which influence the operation of the internal combustion engine. In addition, the mixture preparation evaluates the signal from a λ probe which is arranged in the exhaust tract of the internal combustion engine and indicates whether the combustion is proceeding in a stoichiometric manner, that is to say neither with excess fuel nor with excess air. 
     In order to be able to always adapt the internal combustion engine to an extremely wide variety of operating points in an improved manner, operating parameters can increasingly be changed by means of actuators. For example, control times of an inlet valve or an outlet valve, compression of a piston, a proportion of returned exhaust gas can be varied. In addition, there is a further degree of freedom in the case of a so-called dual injection system comprising a combination of intake manifold and direct injection operation. The mixture preparation takes into account the positions of the actuators when determining the quantity of fuel. Remaining deviations which can be attributed, for example, to imperfections of an actuator are corrected on the basis of the λ value. 
     The λ probe requires a high operating temperature which is usually not yet reached immediately after the internal combustion engine is started. During this phase, the mixture preparation has to carry out a pilot control operation, that is to say determine the quantity of fuel to be injected on the basis of operating parameters of the internal combustion engine, without receiving feedback about the quality of the combustion. 
     DE 10 2008 012 607 B4 proposes carrying out the pilot control of the mixture preparation on the basis of the main parameters rotation speed, load and temperature. Here, a fixed dependence of the quantity of fuel to be injected on the main parameters is assumed. 
     However, the actuators are subject to inaccuracies which can have a significant influence on the pilot control. For example, the actual position of an actuator may differ from its intended position owing to wear, scatter or temperature influence. In this case, pilot control can be carried out on the basis of main parameters of the internal combustion engine only with difficulty. The combustion result may be of low quality, with the result that the environmental pollution created by the internal combustion engine increases. 
     SUMMARY 
     An object of embodiments of the present invention is to specify an improved technique for mixture preparation during the pilot control of an internal combustion engine. 
     A method for the pilot control of a mixture preparation for an internal combustion engine includes the steps of determining a configuration of the internal combustion engine, wherein the configuration is realized by means of a combination of discrete positions of a plurality of actuators which influence operating parameters of the internal combustion engine, determining a constant adaptation component of the mixture preparation which is fed back by means of an exhaust gas probe of the internal combustion engine, storing the constant adaptation component and the associated configuration, and performing pilot control of the mixture preparation with the constant adaptation component when the internal combustion engine is operated in the same configuration. 
     Using the information from the λ probe, the mixture preparation controls the quantity of fuel to be injected during conventional operation in such a way that all inaccuracies and deviations of actual positions of the actuators from their intended values are suitably compensated. Deviations of this kind are incorporated into a constant adaptation component. In this case, the adaptation corresponds to the deviation between the injection quantity determined on the basis of the operating parameters and the actual injection quantity determined on the basis of the λ signal. A variable adaptation component can be attributed to measurement delays, measurement noise and other influences. In the present case, the constant component is assumed to be a deviation in at least one of the actuators from its intended position. By virtue of storing the constant adaptation component during feedback of the mixture preparation by means of the exhaust gas probe, the pilot control can be adapted to the faults in the actuators in an improved manner at a different time at which the internal combustion engine is operated in the same configuration. In addition, improved operation of the internal combustion engine may be achieved when the exhaust gas probe is not available, for example during a cold-running phase of the internal combustion engine. 
     The combination of the discrete positions of the actuators may be understood to be a logical engine. If the position of only one of the actuators changes, another logical engine for which another constant adaptation component may apply is created. This procedure is advantageous particularly in case of conventional actuators which have only a small number of two or three different positions. 
     A direct relationship may be established between a mixture deviation or a mixture adaptation and the actuators involved in the deviation. 
     A temperature dependence of an actuator or a drive strategy may already be taken into account by the concept of the logical engine. If, for example, there is a drive strategy according to which a piston stroke is changed over from a discrete value to another value when a predetermined oil or coolant temperature is reached, two logical engines are automatically formed, one of which operates at the relatively low temperature and the other of which operates at the relatively high temperature. A further operation taking into account the temperature may then no longer be required. 
     An actuator adaptation which can adapt the drive strategy by means of the aging of a control element may automatically also influence the position of the mixture adaptation range by means of the design of the logical engines. 
     Different actuator combinations at the same engine operating point (for example with respect to a rotation speed, a load and/or a temperature) may also have different adaptation values over the logical engines. 
     In an embodiment, an associated constant adaptation component is used for each combination of discrete positions of the actuators. Therefore, the pilot control may be operated with all discrete position combinations. The internal combustion engine may therefore be operated in the warm-running phase on the part of the mixture preparation in all position combinations of the actuators. 
     In an embodiment, the pilot control operation takes into account the constant adaptation component in an additive manner. This is often expedient particularly in the case of low loading of the internal combustion engine. In another embodiment, the pilot control operation may also take into account the constant adaptation component in a multiplicative manner. This may provide better results particularly in the case of a higher load on the internal combustion engine. 
     In a yet further embodiment, the mixture preparation is performed depending on at least one of the parameters of the internal combustion engine, wherein the way in which the constant adaptation component is taken into account during the pilot control operation is dependent on this parameter. In particular, the loading of the internal combustion engine may be expressed, for example, by a rotation speed or a torque, wherein the constant adaptation component is taken into account in an additive manner in the case of a low rotation speed or low torque and is taken into account in a multiplicative manner in the case of a high rotation speed or a high torque. 
     In an embodiment, the mixture preparation is performed depending on a plurality of parameters of the internal combustion engine, wherein respectively associated constant adaptation components are used for different ratios of these parameters. The phase space of the operating states of the internal combustion engine in a combination of discrete positions of the actuators may therefore be suitably broken up in order to allow more precise handling in subspaces. This division may advantageously be assisted by the management of a correspondingly large number of constant adaptation components. 
     A computer program product includes program code means for carrying out the above-described method when the computer program product runs on a processing device or is stored in a computer-readable data carrier. 
     An apparatus for the pilot control of a mixture preparation for an internal combustion engine includes a first interface for sampling a configuration of the internal combustion engine, a second interface for sampling a constant adaptation component of a mixture preparation which is fed back by means of an exhaust gas probe of the internal combustion engine, a memory for recording the constant adaptation component and the associated configuration, and a processing device for providing the constant adaptation component to the mixture preparation when the internal combustion engine is operated in the same configuration and the exhaust gas probe is not available. In this case, the configurations are realized by means of a combination of discrete positions of a plurality of actuators which influence operating parameters of the internal combustion engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention will now be described in more detail with reference to the appended figures, in which: 
         FIG. 1  shows an internal combustion engine with a mixture preparation; and 
         FIG. 2  shows phase spaces of the mixture preparation of  FIGS. 1 ; and 
         FIG. 3  is a flowchart of the operation of an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an internal combustion engine  100  with a mixture preparation  105 . The internal combustion engine  100  may be designed, in particular, for operation in a motor vehicle. The internal combustion engine  100  may include a multi-cylinder reciprocating-piston engine. The mixture preparation  105  is connected to a number of sensors  125  and actuators  130 . The mixture preparation  105  determines the quantity of fuel which should be injected into the internal combustion engine  100  for combustion. In one embodiment, the mixture preparation  105  is designed to drive a fuel injector  135  for dispensing the determined quantity of fuel. The quantity of fuel is usually determined with respect to one or more parameters which may be tapped off from the internal combustion engine  100 . For example, one of the sensors  125  may be an airflow meter, a rotation speed sensor or a torque sensor. Further sensors are likewise possible and may determine, for example, different temperatures or pressures in the internal combustion engine  100 . 
     The operation of the internal combustion engine  100  may additionally be influenced by means of at least one actuator  130 , wherein the actuator  130  has a fixedly predetermined number of discrete positions. A plurality of actuators  130  are usually provided, the actuators controlling, for example, a stroke or a phase of an inlet valve, a stroke or a phase of an outlet valve, a compression of a cylinder or the use of one or more possible injectors. 
     The mixture preparation  105  is connected to a processing device  155  by means of an interface  150 , the processing device in turn being connected to a memory  160 . The processing device  155  is configured to determine, during conventional operation in which a λ probe  140  is available, a deviation between a quantity of fuel which is determined on the basis of the sensors  125  and positions of the actuators  130 , and the quantity of fuel which is determined on the basis of the signal from the λ probe  140 . In particular, a constant proportion is determined and stored in the memory  160  from this difference. This value is associated with a configuration of the internal combustion engine  100 , which configuration is dependent on assumed discrete positions of the actuators  130  owing to the combination. In other words, a pair of values may be formed, which pair of values comprises the combination and the constant adaptation component used. In another embodiment, a fixed location in the memory  160  is associated with one combination and the determined constant adaptation component is stored at the associated point. 
     If the internal combustion engine  100  is operated at a later time without the λ probe  140  being available, for example because it does not yet output a useful signal during a warm-running phase of the internal combustion engine  100 , the mixture preparation  105  has to control the internal combustion engine  100  or determine the quantity of fuel to be injected in the pilot control mode, that is to say without feedback by the signal of the λ probe  140 . To this end, it is proposed to obtain, via the interface  150 , that constant adaptation component which corresponds to the current configuration of the internal combustion engine  100  from the memory  160  using the processing device  155 . This adaptation component is then used to correct the quantity of fuel which was determined on the basis of the positions of the actuators  130  and the signal values from the sensors  125 . 
     A direct relationship between the mixture adaptation and the actuators  130  which are involved in the deviation may be expressed by the constant adaptation component. Temperature dependences of an actuator  130  and of the drive strategy of the actuator  130  may be automatically taken into account since the drive strategy is reflected in the configuration of the internal combustion engine  100 . If, for example, a piston stroke of the internal combustion engine  100  is first changed over at a predetermined operating temperature, this changeover is also automatically taken into account in the pilot control mode by the proposed procedure. Adaptations to the actuators  130  which can adapt the drive strategy, for example by means of influences such as aging of an actuator  130 , may automatically also influence the position of the mixture adaptation range. Different configurations of the internal combustion engine  100  at the same operating point in respect of rotation speed, load and temperature of the internal combustion engine  100  may also have different adaptation values in this way. 
       FIG. 2  shows phase spaces  200  of the mixture preparation  105  of  FIG. 1 . A load L of the internal combustion engine  100  is plotted in the horizontal direction, and the rotation speed N of said internal combustion engine is plotted in the vertical direction. Different configurations K of the internal combustion engine  100  are indicated along a third axis. 
     At least one constant adaptation component, which is used for determining the quantity of fuel to be injected, is prespecified for each configuration K. In the illustration of  FIG. 2 , two adaptation values, which cover different parts of the respective phase space, are prespecified for each configuration K. Purely by way of example, the phase spaces are separated into subspaces  205  which have a substantially triangular shape. 
     The associated constant adaptation components may be taken into account in an additive manner or in a multiplicative manner in different embodiments. In one embodiment, the way in which the adaptation components are taken into account may be dependent on the load of the internal combustion engine  100 . In this case, the transfer may be made in discrete steps or continuously. For example, the stored constant adaptation component may be taken into account in an additive manner in the case of a low load, while the adaptation component is taken into account in a multiplicative manner in the case of a higher load. For a continuous transfer, the processes of taking into account the adaptation component both in an additive manner and in a multiplicative manner are determined and weighted by means of weighting factors which are dependent on the load. The sum of the weighted correction terms is then passed on to the processing device  105 . 
     As in the case of a known mixture adaptation, the correction of the fuel pilot control may be taken into account directly during calculation of the quantity of fuel to be injected. However, ascertaining the correction value to be taken into account depends, amongst other things, on the currently active logical engine:
 
MFF_SP_COR=MFF_SP_BAS*[Σ(AD_ i _LogEng_ k ×FAC_ i _ k )]/Σ(FAC_ i _ k )]*FAC_LAM* . . .
 
     where: 
     MFF_SP_COR: actuating value for fuel flow, which actuating value is corrected by exhaust gas control 
     MFF_SP_BAS: actuating value for basic fuel flow 
     LogEng_k: logical engine k 
     AD_i_LogEng_k: adaptation value i of the logical engine k 
     FAC_i_k: weighting factor for adaptation value i of the logical engine k 
     FAC_LAM: correction of the lambda pilot control and/or lambda control. 
     When a changeover is made between actuator positions, the transition between two related adaptation values is also defined by means of the weighting factors FAC_i_k. This transition represents the physical transition in this case. A transition may therefore be performed in a synchronized manner at the moment at which, for example, a valve stroke is changed in order to apply the correct adaptation value in good time for the purpose of calculating the associated injection mass. Furthermore, a transition may, however, also be performed with a time delay or in the form of a smoothed transfer. 
     Referring to  FIG. 3 , there is shown a method for the pilot control of a mixture preparation for an internal combustion engine includes the steps of determining at  302  a configuration of the internal combustion engine, wherein the configuration is realized by means of a combination of discrete positions of a plurality of actuators which influence operating parameters of the internal combustion engine, determining at  304  a constant adaptation component of the mixture preparation which is fed back by means of an exhaust gas probe of the internal combustion engine, storing at  306  the constant adaptation component and the associated configuration, and performing at  308  pilot control of the mixture preparation with the constant adaptation component when the internal combustion engine is operated in the same configuration. 
     Embodiments have been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The description above is merely exemplary in nature and, thus, variations may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims. 
     LIST OF REFERENCE SYMBOLS 
     
         
           100  Internal combustion engine 
           105  Mixture preparation 
           110  Processing device 
           125  Sensor 
           130  Actuator 
           135  Fuel injector 
           140  Lambda probe 
           150  Interface 
           155  Processing device 
           160  Memory 
           200  Phase space 
           205  Subspace 
         L Load 
         N Rotation speed 
         K Configurations