Method for operating an internal combustion engine

In an internal combustion engine, combustion air is supplied to at least one combustion chamber via at least one intake duct. The intake duct includes at least two parallel control sections, to each of which one final controlling device is allocated. Using these final controlling devices, the flow cross-section of the particular control section may be influenced. At least two final controlling devices are activated based on one single setpoint variable, and, in fact, using only one control and/or regulating system associated with the intake duct.

FIELD OF THE INVENTION

The present invention relates first of all to a method for operating an internal combustion engine, where combustion air is supplied to at least one combustion chamber via an intake duct which includes at least two parallel control sections, to each of which a final controlling device is allocated, via which the flow cross-section of the particular control section may be influenced.

BACKGROUND INFORMATION

The present invention further relates to a computer program, an electrical memory medium for a control and/or regulating system of an internal combustion engine, a control and/or regulating system for an internal combustion engine, and an internal combustion engine, in particular for a motor vehicle.

A method is known from the market. It is used with internal combustion engines having a vee-type cylinder arrangement, for example. Each of the two cylinder banks of an internal combustion engine of this type has its own intake duct which, in turn, has its own throttle valve. The positions of the throttle valves are adjusted independently of each other via separate position regulating circuits. A separate setpoint value is generated for each position regulating circuit in a dedicated control unit.

An object of the present invention is to further develop a method of the type mentioned in the preamble such that the corresponding internal combustion engine is as compact and economical as possible.

In a computer program, the object is attained by programming the computer program for use in a method of the type described above. In an electrical memory medium, the object is attained by storing a computer program in the electrical memory medium for use in a method of the type described above.

In a control and/or regulating system, the object is attained by programming the control and/or regulating system for use, in this case, in a method of the type described above. In an internal combustion engine, the object is attained by the fact that it includes, in this case, a control and/or regulating system which is used in a method of the type described above.

SUMMARY OF THE INVENTION

In the method according to the present invention, the hardware which would be required to generate a second setpoint variable may be eliminated, because the final controlling devices are activated based on a common setpoint variable. For example, a second control unit which would be responsible for forming a second setpoint variable can be eliminated. Finally, with this method, adjustment of two final controlling devices of a single intake duct is therefore enabled using a single control unit. Costs and installation space are reduced as a result. Although the use of a single setpoint variable means that, in the normal case, the two final controlling devices cannot be adjusted differently from each other, this is, however, quite acceptable for many internal combustion engines having a single intake duct.

It is first proposed that each final controlling device have its own closed-loop position control to which the same setpoint variable is supplied. In this manner, each individual final controlling device may be adjusted optimally and under consideration of its individual mechanical properties. Manufacturing tolerances are compensated for very well in this manner.

It is particularly advantageous when a final controlling device includes at least two position sensors which detect the instantaneous position of a final controlling element belonging to the final controlling device, and that the plausibility of the signals from the position sensors of the final controlling device is monitored. The use of a plurality of position sensors and monitoring the plausibility of the signals from the position sensors increases the safety of operation of the internal combustion engine, because erroneous adjustments of the position of the final controlling element due to erroneous position recognition can be largely ruled out.

In a refinement of the present invention, it is proposed that, if an error occurs, a determination is made as to which of the position sensors of the final controlling device is defective by forming a value for a partial air-mass flow from the signals from the position sensors of each final controlling device and checking the determined values of the partial air-mass flow for plausibility by referencing them against a value of a measured total air-mass flow. Generally, the formation of the value of a partial air-mass flow from the signal from a position sensor is carried out indirectly, i.e., via the detour of determining an angle, e.g., using a characteristic curve and then determining the partial air-mass flow from the angle. Further operation of the internal combustion engine is enabled as a result, because, by identifying the faulty position sensor, its signal may be excluded from further use. The regulation of the position of the final controlling element is then based only on the signals from the position sensor which is functioning correctly.

A further advantageous embodiment of the method according to the present invention provides that each of the final controlling devices includes a clamping device which is capable of holding the final controlling element of a final controlling device in a neutral position, and an activating device which can move the final controlling element out of the neutral position, and that, to perform a function test, the activating devices of both final controlling devices are activated so that the final controlling elements move into a test position, and that, when both final controlling elements are in the test position, activation is ended and the period of time required for the final controlling elements to move from the test position into the neutral position is detected.

The clamping device provided according to the present invention provides that, even if the closed-loop position control fails completely, the final controlling element is brought into a certain neutral position in which an “emergency operation” of the internal combustion engine is possible. The clamping device is therefore a safety device. Its proper effect is given only when the final controlling element moves sufficiently smoothly, i.e., it does not “stick”. This effect is investigated by the proposed method. Finally, this also makes the operation of the internal combustion engine safer as a result. In addition, separate activation of the final controlling devices is not required for this function test, because activation is basically not ended until the last final controlling element has reached its test position.

In a refinement of the present invention, it is proposed that the function test is carried out in separate test blocks for each final controlling device, the test blocks being coordinated with each other. This is simple to implement using software, and it allows a few tests within the test block to be carried out for one final controlling device fully independently of the other final controlling device, and it also allows other function tests to run simultaneously. This saves time so that the function test can be carried out relatively frequently.

It is further proposed that, in certain operating situations of the internal combustion engine, current properties of a final controlling device are detected independently of another final controlling device and are made available for activation. As a result, the precision of the adjustment of the final controlling device is improved. For example, changes in mechanical properties of the final controlling device due to wear or replacement of a final controlling element, and many other properties, may be determined currently and taken into account in the activation of the final controlling device. Due to the use of a dedicated learning and test block for each final controlling device, the learning and testing methods may be carried out independently of each other, i.e., simultaneously. As described above, this allows these methods to be carried out relatively frequently.

A further advantageous embodiment of the method according to the present invention is unique in that status information about a final controlling device and its components are stored independently of another final controlling device. Despite the use of a single setpoint variable to activate two final controlling devices, status information from one final controlling device is stored independently of the other final controlling device. This also increases safety, because, since status information is stored “in parallel,” this information may be stored more frequently and is therefore particularly current.

It is further proposed that error information be evaluated jointly for all final controlling devices and that corresponding responses be triggered. This refinement takes into account the fact that an error identified in one final controlling device may affect the operation of the other final controlling device. Joint error evaluation therefore allows the overall situation of the internal combustion engine to be observed. In turn, this makes it easier to prevent damage to the internal combustion engine as a whole, and to protect the operator from danger.

It is particularly preferred if identical error information from the final controlling devices is gated using a logical “or”. This means that, when a certain error type occurs in only one final controlling device, this is sufficient to trigger a certain error response.

DETAILED DESCRIPTION

An internal combustion engine is labeled in its entirety with reference numeral10inFIG. 1. It is used to drive a motor vehicle (not shown). Internal combustion engine10has two cylinder banks12aand12b, each of which has four cylinders and four combustion chambers14athrough14dand14cthrough14h. These cylinder banks12aand12bare positioned relative to each other in the shape of a vee. The internal combustion engine10shown inFIG. 1is therefore a V8-engine.

Combustion air is supplied to cylinders14of internal combustion engine10via an intake duct, an intake manifold16in this case. An air filter18is provided at the end of intake manifold16facing away from combustion chambers14. Downstream of air filter18, intake manifold16is divided into two control sections20aand20bwhich are parallel to each other. One final controlling device22aand22b, respectively, is allocated to each of these control sections. Using the final controlling devices, it is possible to influence the flow cross-section of corresponding control section20aand/or20b, as explained below in greater detail.

An intake manifold divider24is provided in intake manifold16downstream of control sections20aand20b, the intake manifold divider dividing intake manifold16into two intake manifold sections26aand26b, each allocated to one cylinder bank12aand12b, respectively. A manifold28aand/or28bfurther divides the air stream among the individual combustion chambers14athrough14dand14ethrough14h.

Final controlling devices22aand22bare identical in design. For the sake of simplicity, the design of only final controlling device22awill be discussed in greater detail below: It includes a final controlling element30aconfigured as a throttle valve, which is movable into any position by an activating device32a. A fully closed position of throttle valve30ais defined by a “lower mechanical” stop34a. A stop is also provided for the fully open position, although it is not shown in the figure. Two springs36aand38aact on throttle valve30a, by way of which throttle valve30ais brought into a neutral position (the “limp-home air position”) if activating device32ais switched off, i.e., de-energized. In the present exemplary embodiment, this neutral position corresponds to a degree of opening of approximately 6%.

The instantaneous position of throttle valve30ais detected by two position sensors40aand42a; in this case, they are potentiometers, one each of which is coupled to a throttle valve. As shown inFIG. 2, the characteristic curves of position sensors40aand42a, which link a signal voltage u1a(position sensor40a) and u2a(position sensor42a) with an angle iw, are mirror images of each other.

Position sensors40aand42asupply corresponding signals to a control and regulating system44, which outputs corresponding triggering signals to the activating device32a. The control and regulating system, which will also be described in greater detail below, includes a closed control loop for adjusting the position of throttle valve30a. In this process, only one single setpoint value is generated in a setpoint value generator46for both final controlling devices22aand22bin the control and regulating system, namely as a function of the position of a gas pedal48, among other things. The total air mass flowing through intake duct16is detected by an HFM sensor50, which also delivers corresponding signals to control and regulating system44.

The operation of an internal combustion engine10will now be explained in greater detail with reference toFIG. 3:

The use of a single setpoint value wdks for activating throttle valves30aand/or30bis identical for both final controlling devices22aand/or22b. For the sake of simplicity, only the procedure for final controlling device22aand/or throttle valve30awill therefore be described below.

Setpoint variable wdks is supplied to a block52a, to which an actual value iwa is also supplied, by an actual value generator54a. In turn, voltage signals u1aand u2a, which are provided by potentiometers40aand42a, are supplied to the actual value generator. To this end, the current and mirror-symmetric characteristic curves of position sensors40aand42aare stored in actual value generator54a. The characteristic curves are generated in a manner described in greater detail below.

Block52acontains a position controller for throttle valve30a, which is designed as a PID controller. Errors in the triggering circuit are also diagnosed in block52a, however. The position controller contained in block52aoutputs a pulse-width modulated pulse duty factor and a directional bit to an end stage which is not shown in the figures. The end stage is designed as an integrated H-bridge having internal current-limit control. In block52a, the position controller is also monitored for impermissible deviations of actual value iwa from setpoint value wdks. In addition, setpoint value wdks is monitored to determine if a range is exceeded, and the operating condition of the end stage is also monitored.

The signals from both position sensors40aand42aare supplied to actual value generator54a. Actually, however, only signal u1afrom position sensor40ais normally used to generate the actual value; actual angle iwa is thus equal to value iw1aobtained from the characteristic curve. Signal u2afrom position sensor42ais used to check signal u1afrom position sensor40aand is used when signal u1ahas been recognized as being erroneous. This check takes place specifically as follows (seeFIG. 4):

After a start block56, the absolute value of the difference between actual values iw1aand iw2ais formed in58; the difference is obtained from voltage signals u1aand u2afrom position sensors40aand42a. If this amount is less than a limiting value G1, that is, if both position sensors40aand42aindicate positions of throttle valve30athat are essentially identical, it is assumed that the signals which were supplied are correct. In this case, signal u1afrom position sensor40aand the corresponding characteristic curve are used to form actual value iwa, and the process jumps back to the input of block58(i.e., this check is carried out continually). The basis thereof is the consideration that it is unlikely that both position sensors40aand42aindicate an identical position of the throttle valve30aif an error occurs, despite their having characteristic curves which run in opposite directions.

If the result of block58is “no,” however, total air mass mHFM which flows through intake duct16is first determined in block60based on the signal from HFM sensor50. Furthermore, air mass m40bflowing through control section20bis determined from voltage signal u1bfrom position sensor40bwhich is allocated to second throttle valve30b, which has not yet been discussed explicitly (an angle is first determined from signal u1b, and from this, the corresponding mass flow m40bis then determined). It is assumed here that it is unlikely that position sensors40band42bof second final controlling device22balso yield an erroneous signal.

The absolute value of the difference is now formed from air mass mHF and m40b, which is supplied by the air mass flowing through control section20a. Furthermore, the corresponding air masses miw1aand miw2a(one of which must be erroneous, based on the results of the query in block58) are determined from signals u1aand u2aof position sensors40aand42aand the positions (angles) of throttle valve30adetermined from the signals.

A check is now run in block62to determine which of the two air masses miw1aor miw2adetermined based on signals u1aand u2abest corresponds to the correct air mass ma. To accomplish this, a check is run to determine whether the difference between the correct air mass ma and air mass miw1adetermined based on signal u1aof position sensor40ais greater than the difference between correct air mass ma and air mass miw2adetermined based on signal u2aof position sensor42a. If the answer in block62is “yes,” this means that sensor40ais supplying an erroneous signal (block64). If the answer in block62is “no,” this means that position sensor42ais supplying an erroneous signal (block66). In the first case, the characteristic curve of position sensor42and/or value iw2ais used immediately to form actual value iwa. The procedure ends in block68.

As mentioned above, the characteristic curves used in actual value generator54aare updated continually. To this end, the current slopes of the characteristic curves and the voltage values of a defined position of throttle valve30aare repeatedly made available to actual value generator54a. They are made available in a learning and test block70a. In the learning and test block, activating device32ais activated in certain operating situations of internal combustion engine10in such a way that throttle valve30adefinitely rests against stop34. An operating situation of this type is present, for instance, when the operator turns on the ignition of internal combustion engine10but the engine does not start right away.

When throttle valve30arests against stop34, the corresponding voltage values of position sensors40aand42aare detected and stored. Activating device32ais then de-energized, so that throttle valve30amoves into the neutral position defined by the two clamping devices36aand38a, and the voltage values of the two position sensors40aand42aare read again. In this manner, the characteristic curves are defined unambiguously. In addition, this allows the voltage value corresponding to the neutral position to be detected. The voltage value is made available to the position controller in block52ato enable the most precise pilot control of throttle valve30apossible.

Another test is carried out in learning and test block70a. For example, if an error is detected in an actual value amplification, the operational reliability of springs36aand38ais checked, and throttle valve30ais checked for smoothness of movement and/or “sticking”. The latter will now be explained with reference toFIG. 5:

After a start block72, the two throttle valves30aand30bare moved into a defined position POS1in block74. In block76, the signals from position sensors40aand42aand/or40band42bare used to check whether the two throttle valves30aand30bhave reached position POS1. If they have not, activation of activating devices32and/or32bcontinues. It may be assumed that, due to manufacturing differences, throttle valves30aand30bdo not reach position POS1absolutely simultaneously. In the current method, however, in block78, activating devices32aand32bare not de-energized (block78) until the “slower” of the two throttle valves30aor30bhas reached position POS1.

Time t1is detected for throttle valve30aand time t2is detected for throttle valve30b, the time being the period of time that elapses until the particular throttle valve30aor30breaches the neutral position (also referred to as the “limp-home air position”) defined by springs36aand38a. The corresponding time values t1and t2are detected in block80ofFIG. 5.

A check is carried out in block82to determine whether the detected time values t1and t2are less than a limiting value G2. If one of the time values t1or t2reaches at least limiting value G2, this means that the corresponding throttle valve30aor30bdoes not move as smoothly as desired, or that one of the springs36or38is broken. A corresponding error message ERR1or ERR2is therefore generated in block84. If the answer in block82is “yes,” however, another check is carried out in block82to determine whether the absolute value of the difference between times t1and t2is less than a limiting value G3. In this manner, wear on one side of a throttle valve30aor30bmay be detected. Depending on the result of the query in block86, an error message ERR3is generated in block88, or the process jumps to End block90.

As shown inFIG. 3, the different error states which are generated in the tests carried out in blocks54aand70a(and for throttle valve30bin blocks54band70b) are supplied to a response block92. Depending on the type of error which is present, corresponding response procedures react1, react2, etc. (block94) are implemented in response block92. Identical error types occurring in the two final controlling devices22aand22bare gated in block92using a logical “or.” If the error is present in only one final controlling device22aor22b, this is therefore sufficient to trigger a corresponding response. The responses may mean that the performance of the internal combustion engine is limited, that throttle valves30aand30bare being brought into the neutral position, or that internal combustion engine10has been brought to a standstill because fuel supply or fuel injection has been switched off.

As further shown inFIG. 6, a separate status memory94aor94bis provided for each final controlling device22aand/or22b, in which current status information regarding final controlling devices22aand22band their components, e.g., final controlling elements30, activating devices32, springs26and28, and position sensors40and42are stored. The two status memories94aand94bmay be read out using a corresponding diagnostic tool during service of internal combustion engine10.